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GNAT User's Guide for Unix Platforms

1. 28 May 2002 Chapter 6 The GNAT Make Program gnatmake First a definition an object file is considered up to date if the corre sponding ALI file exists and its time stamp predates that of the object file and if all the source files listed in the dependency section of this ALI file have time stamps matching those in the ALI file This means that neither the source file itself nor any files that it depends on have been modified and hence there is no need to recompile this file gnatmake works by first checking if the specified main unit is up to date If so no compilations are required for the main unit If not gnatmake compiles the main program to build a new ALI file that reflects the latest sources Then the ALI file of the main unit is examined to find all the source files on which the main program depends and gnatmake recursively applies the above procedure on all these files This process ensures that gnatmake only trusts the dependencies in an existing ALI fileif they are known to be correct Otherwise it always recompiles to determine a new guaranteed accurate set of dependencies As a result the program is compiled upside down from what may be more familiar as the required order of compilation in some other Ada systems In particular clients are compiled before the units on which they depend The ability of GNAT to compile in any order is critical in a
2. 28 May 2002 Chapter 2 The GNAT Compilation Model pragma Source_File_Name Body File Name gt 2 ada The default GNAT scheme is actually implemented by providing the following default pragmas internally pragma Source File Name Spec File Name gt ads Dot Replacement gt nan pragma Source_File_Name Body_File_Name gt adb Dot_Replacement gt nau Our final example implements a scheme typically used with one of the Ada 83 compilers where the separator character for subunits was __ two underscores specs were identified by adding Apa bodies by adding apa and subunits by adding sEp All file names were upper case Child units were not present of course since this was an Ada 83 compiler but it seems reasonable to extend this scheme to use the same double underscore separator for child units pragma Source_File_Name Spec File Name gt _ ADA Dot Replacement gt __ Casing Uppercase pragma Source_File_Name Body_File_Name gt ADA Dot Replacement gt __ Casing Uppercase pragma Source_File_Name Subunit_File_Name gt SEP Dot_Replacement gt __ Casing Uppercase 2 6 Generating Object Files An Ada program consists of a set of source files and the first step in com piling the program is to generate the corresponding object files These are generated by comp
3. 539 May 2002 Chapter 24 Inline Assembler Application Note AP 485 Intel Processor Identification and the CPUID Instruction as of April 1998 This application note can be found on www intel com It currently deals with 32 bit processors only will not detect features added after april 1998 and does not guarantee proper results on Intel compatible processors Cache info and x386 fpu type detection are not supported This package does not use any privileged instructions so should work on any OS running on a 32 bit Intel processor with Interfaces use Interfaces for using unsigned types with System Machine_Code use System Machine_Code for using inline assembler code with Ada Characters Latin_1 use Ada Characters Latin_1 for inserting control characters package Intel_CPU is 315 GNAT User s Guide for Unix Platforms subtype Num_Bits is Natural range O 31 the number of processor bits 32 define a processor register type for easy access to the individual bits type Processor_Register is array Num_Bits of Boolean pragma Pack Processor_Register for Processor Register Size use 32 define a processor register type for easy access to the individual bytes type Unsigned_Register is record L1 Unsigned_8 H1 Unsigned_8 L2 Unsigned_8 H2 Unsign
4. gnat finalize exit gnat exit status unsigned helloB 0x7880BEB3 23 May 2002 unsigned unsigned unsigned unsigned unsigned unsigned unsigned unsigned unsigned unsigned unsigned unsigned unsigned unsigned unsigned unsigned unsigned unsigned unsigned unsigned unsigned unsigned unsigned unsigned unsigned unsigned unsigned unsigned unsigned unsigned unsigned unsigned unsigned unsigned unsigned unsigned unsigned unsigned unsigned unsigned unsigned unsigned unsigned Chapter 4 Binding Using gnatbind system__standard_libraryB 0x0D24CBD0 0x3283DBEB system__standard_libraryS adaS 0x2359F9ED ada__text_ioB 0x47C85FC4 ada__text_ioS 0x496FE45C ada__exceptionsB 0x74F50187 ada__exceptionsS 0x6736945B gnatS 0x156A40CF gnat__heap_sort_aB 0x033DABEO0 gnat__heap_sort_aS Ox6AB38FEA systemS 0x0331C6FE System exceptionsS Ox20C9ECA4 System exception tableB 0x68A22947 System exception tableS Ox394BADDb gnat htableB 0x08258E1B gnat htableS 0x367D5222 system machine state operationsB Ox4F3B7492 system machine state operationsS 0x182F5CF4 System storage elementsB 0x2F1EB794 system storage elementsS 0x102C83C7 system secondary stackB 0x1574B6E9 System secondary stackS8 0x708E260A System parametersB 0x56D770CD system parametersS 0x237E39BE system__soft_linksB Ox08AB6B2C system__soft_linksS 0x1E2491F3 syst
5. 233 16 2 Installing an AdaLibrary 234 16 3 Usingan AdaLibrary Qo 235 16 4 Creatingan Ada Library to be Used in a Non Ada Context PONE PREIS DUDEN 236 16 4 1 CreatingtheLibrary 236 16 4 2 UsingtheLibrary 237 16 4 3 TheFinalization Phase 238 16 4 4 Restrictions in Libraries 238 165 Rebuildingthe GNAT Run TimeLibrary 239 17 Using the GNU make Utility BEN OHENNEEENENUEEESESESM 241 17 1 Usinggnatmakein a Makefile 241 17 2 Automatically Creating a List of Directories 243 17 3 Generating the Command Line Switches 245 17 4 Overcoming Command Line Length Limits 245 18 Finding Memory Problems with gnatmem 247 18 1 Running gnatmem GDB Mode 247 18 2 Running gnatmem GMEM Modge 248 18 3 Switches for ematiems sii creo REL RA 249 18 4 Example of gnatmem USaYQe 249 185 GDB and GMEM MOodES 253 18 6 Implementation NOte 253 18 6 1 gnatmem Using GDB Mode 253 18 6 2 gnatmem Using GMEM Mode 253 19 Finding Memory Problems with GNAT Debug 20 Creating Sample Bodies Using gnatstub 259 20 1 RUnNnNinJggnatstUb 000000446 259 20 2 Switchesforgnat
6. 35 GNAT User s Guide for Unix Platforms compiler would simply construct a program that malfunctioned at run time 2 13 Comparison between GNAT and Conventional Ada Library Models This section is intended to be useful to Ada programmers who have pre viously used an Ada compiler implementing the traditional Ada library model as described in the Ada 95 Language Reference Manual If you have not used such a system please go on to the next section In GNAT there is no library in the normal sense Instead the set of source files themselves acts as the library Compiling Ada programs does not generate any centralized information but rather an object file and a ALI file which are of interest only to the binder and linker In a tradi tional system the compiler reads information not only from the source file being compiled but also from the centralized library This means that the effect of a compilation depends on what has been previously compiled In particular e When a unit is with ed the unit seen by the compiler corresponds to the version of the unit most recently compiled into the library e Inlining is effective only if the necessary body has already been compiled into the library e Compiling a unit may obsolete other units in the library In GNAT compiling one unit never affects the compilation of any other units because the compiler reads only source files Only changes to source files can affect the results of a c
7. ada finalization list controllerS system machine code spec system parameters spec system parameters body interfaces c streams spec interfaces c streams body system standard library spec ada exceptions spec system exception table spec system exception table body ada io exceptions spec system exceptions spec system storage elements spec system storage elements body system machine state operations spec system machine state operations body system secondary stack spec system stack checking spec system soft links spec system soft links body system stack checking body system secondary stack body 81 GNAT User s Guide for Unix Platforms system standard_library body system string_ops spec system string ops body ada tags spec ada tags body ada streams spec system finalization root spec system finalization root body system string ops concat 3 spec system string ops concat 3 body system traceback spec system traceback body ada exceptions body system unsigned_types spec system stream attributes spec system stream attributes body system finalization implementation spec system finalization implementation body ada finalization spec ada finalization body ada final
8. end Decls with Utils package body Decls is task body Lib Task is begin accept Start Utils Put Val 2 end Lib Task function Ident M My Int return My Int is begin return M end Ident end Decls with Decls package Utils is procedure Put Val Arg Decls My Int end Utils with Text I0 package body Utils is procedure Put Val Arg Decls My Int is begin Text IO0 Put Line Decls My Int Image Decls Ident Arg end Put Val end Utils with Decls 193 GNAT User s Guide for Unix Platforms procedure Main is begin Decls Lib_Task Start end If the above example is compiled in the default static elaboration mode then a circularity occurs Thecircularity comes fromthecall utils Put val in the task body of Decls Lib Task Since this call occurs in elabo ration code we need an implicit pragma elaborate A11 for Utils This means that not only must the spec and body of utils be elaborated be fore the body of Decls but also the spec and body of any unit that is with ed by the body of utils must also be elaborated before the body of Decls This is the transitive implication of pragma Elaborate_A11 and it makes sense because in general the body of Put val might have a call to something in a with ed unit In this case the body of Utils actually its spec with s Decls Un fortunately this means that the body of Dec1s must be elaborated before itself in case there is a call from the body of
9. objects will be recompiled and the main program will be re linked The list of computer software component for your project This might be generated automatically CSC_LIST aa bb cc Name of the main program no extension MAIN main If we need to build objects with fPIC uncomment the following line tNEED_FPIC fPIC The following variable should give the directory containing libgnat so You can get this directory through gnatls v This is usually the last directory in the Object Path GLIB The directories for the libraries This macro expands the list of CSC to the list of shared libraries you could simply use the expanded form LIB_DIR aa lib libaa so bb lib libbb so cc lib libcc so LIB_DIR foreach dir CSC_LIST dir lib lib dir so MAIN objects LIB_DIR gnatbind MAIN CSC_LIST a0 lib shared gnatlink MAIN CSC_LIST 1 objects recompile the sources gnatmake c i MAIN adb NEED_FPIC CSC_LIST 1 Note In a future version of GNAT the following commands will be simplified by a new tool gnatmlib LIB_DIR mkdir p dir cd dir 0 gcc shared o notdir o L GLIB lgnat cd dir 0 cp f ali 242 CccL 23May 2002 Chapter 17 Using the GNU make Utility The dependencies for the modules Note that we
10. pragma Source_File_Name Body_File_Name gt FILE_NAME_PATTERN Casing gt CASING_SPEC Dot_Replacement gt STRING_LITERAL pragma Source_File_Name Subunit_File_Name gt FILE_NAME_PATTERN Casing gt CASING_SPEC Dot Replacement gt STRING LITERAL FILE NAME PATTERN STRING LITERAL CASING_SPEC Lowercase Uppercase Mixedcase 21 GNAT User s Guide for Unix Platforms The FILE NAME PATTERN String shows how the file name is constructed It contains a single asterisk character and the unit name is substi tuted systematically for this asterisk The optional parameter casing indicates whether the unit name is to be all upper case letters all lower case letters or mixed case If no casing parameter is used then the default is all lower case The optional Dot Replacement string is used to replace any periods that occur in subunit or child unit names If no Dot Replacement ar gument is used then separating dots appear unchanged in the resulting filename Although the above syntax indicates that the casing argu ment must appear before the bot Replacement argument but it is also permissible to write these arguments in the opposite order As indicated it is possible to specify different naming schemes for bodies specs and subunits Quite often the rule for subunits is the same as the rule for bodies in which case there is no need to give a separate Subunit File Name rule andin this casethe Body F
11. 120 nostdlib gnatmake 121 OWE6e o s e E eae dae Sei 39 D ECC sss em ee etc 39 328 o gnatbind 104 342 0 gnatbind 104 o gnathtml 271 o gnatlink 112 o gnatls oves Ene 230 o gnatmake 119 o gnatmem 249 p gnatchop ecis cieri enes RG 128 gnathtmnl crc eene 271 P gnatname 134 pass exit codes gcc 67 q gnatchop 128 q gnatmake 119 q gnatmem Ass aane harde Ld E 249 r gnatbind 104 r gnatchop 128 SS GCC rs ada M epis 39 s gnatbind 102 si gnatls ooi erea a a ai 230 sc gnathtml 271 t gnatbind 103 t gnathtml sseesssse 271 w gnatis s Gist setae ay ae ela 230 u gnatmake 120 SV GCC vein dale E veri ee aa 39 V ECC AF bu tel heehee dhe dee 39 v gnatbind 102 v gnatchop 128 v gnatlink s esses 112 v gnatmake 04 120 gnatname 135 v v gnatlink 112 I arbi d lio d gcuan RON RLM 51 w gnatchop 128 we gnatbind 103 ws gnatbi
12. It is not possible to refer to the original generic entities in GDB but it is always possible to debug a particular instance of a generic by using the appropriate expanded names For example if we have 280 s3May 2002 Chapter 23 Running and Debugging Ada Programs procedure g is generic package k is procedure kp v1 inout integer end k package body k is procedure kp vi inout integer is begin vi vi 1 end kp end k package k1 is new k package k2 is new k var integer 1 begin ki kp var k2 kp var ki kp var k2 kp var end Then to break on a call to procedure kp in the k2 instance simply use the command gdb break g k2 kp When the breakpoint occurs you can step through the code of the in stance in the normal manner and examine the values of local variables as for other units 23 10 GNAT Abnormal Termination or Failure to Terminate When presented with programs that contain serious errors in syntax or semantics GNAT may on rare occasions experience problems in op eration such as aborting with a segmentation fault or illegal memory access raising an internal exception terminating abnormally or failing to terminate at all In such cases you can activate various features of 281 GNAT User s Guide for Unix Platforms GNAT that can help you
13. e A range iin a for loop that is known to be null or might be null The following switches are available to control the handling of warning messages gnatwa activate all optional errors This switch activates most optional warning mes sages see remaining list in this section for details on optional warning messages that can be indi vidually controlled gnatwA suppress all optional errors This switch suppresses all optional warning mes sages see remaining list in this section for details on optional warning messages that can be indi vidually controlled gnatwb activate warnings on biased rounding If a static floating point expression has a value that is exactly half way between two adjacent machine numbers then the rules of Ada Ada Reference Manual section 4 9 38 require that this rounding be done away from zero even if the normal unbiased rounding rules at run time would require rounding towards zero This warn ing message alerts you to such instances where compile time rounding and run time rounding are not equivalent I fit is important to get proper run time rounding then you can force this by making one of the operands into a variable The default is that such warnings are not generated Note that gnatwa does not affect the setting of this warning option gnatwB suppress warnings on biased rounding This switch disables warnings on biased round ing gnatwe activate warnings on conditionals This s
14. movl ebx 1 Inputs gt Unsigned_32 Asm_Input g Var_In Outputs gt Unsigned_32 Asm_Output g Var_Out Clobber gt ebx Volatile gt True By default volatile is set to False unless there is no outputs pa rameter Although setting volatile to True prevents unwanted optimizations it will also disable other optimizations that might be important for effi ciency In general you should set volatile to True only if the compiler s optimizations have created problems 24 7 A Complete Example This section contains a complete program illustrating a realistic usage of GNAT s Inline Assembler capabilities It comprises a main procedure Check CPU and a package Intel cpu The package declares a collection of functions that detect the properties of the 32 bit x86 processor that is running the program The main procedure invokes these functions and displays the information The Intel CPU package could be enhanced by adding functions to detect the type of x386 co processor the processor caching options and special operations such as the SIMD extensions Although the Intel CPU package has been written for 32 bit Intel compatible CPUs it is OS neutral It has been tested on DOS Win dows NT and Linux 24 7 1 Check cPU Procedure 304 28 May 2002 Chapter 24 Inline Assembler running on and some
15. pragma Export C u00039 interfaces c streamsB pragma Export C u00040 interfaces c streams pragma Export C u00041 system file ioB pragma Export C u00042 system file io pragma Export C u00043 ada finalizationB pragma Export C u00044 ada__finalizationS pragma Export C u00045 system finalization rootB 80 28 May 2002 pragma pragma pragma pragma pragma pragma pragma pragma pragma pragma pragma pragma BEGIN ELABORATION ORDER ada gnat gnat gnat gnat gnat inte syst Export C u00046 Export C u00047 Export C u00048 Export C u00049 Export C u00050 Export C u00051 Export C u00052 Export C u00053 Export C u00054 Export C u00055 Export C u00056 Export C u00057 spec spec heap_sort_a spec heap_sort_a body htable spec htable body rfaces spec em spec Chapter 4 Binding Using gnatbind system__finalization_rootS system__finalization_implementationB system__finalization_implementationS system__string_ops_concat_3B system__string_ops_concat_38 system__stream_attributesB system stream attributes ada io exceptions system unsigned types system file control block ada finalization list controllerB
16. 129 GNAT User s Guide for Unix Platforms 130 8 May 2002 Chapter 8 Configuration Pragmas 8 Configuration Pragmas In Ada 95 configuration pragmas include those pragmas described as such in the Ada 95 Reference Manual as well as implementation dependent pragmas that are configuration pragmas See the individual descriptions of pragmas in the GNAT Reference Manual for details on theseadditional GNAT specific configuration pragmas Most notably the pragma source File Name which allows specifying non default names for source files is a configuration pragma The following is a complete list of configuration pragmas recognized by GNAT Ada_83 Ada_95 C_Pass_By_Copy Component_Alignment Discard_Names Elaboration_Checks Eliminate Extend_System Extensions Allowed External Name Casing Float Representation Initialize Scalars License Locking Policy Long Float No Run Time Normalize Scalars Polling Propagate_Exceptions Queuing Policy Ravenscar Restricted_Run_Time Restrictions Reviewable Source_File_Name Style_Checks Suppress Task_Dispatching Policy Unsuppress Use_VADS_Size Warnings Validity_Checks 131 GNAT User s Guide for Unix Platforms 8 1 Handling of Configuration Pragmas Configuration pragmas may either appear at the start of a compilation unit in which case they apply only to that unit or they may apply to all compilations performed in a given compilation environment GNAT alsoprovides the gnat chop
17. 1ink opt notation This is intended to store the default switches given to gnat link main EXECUTABLE default specifies the name of the executable for the application This variable can be referred to in the following lines by using the main notation comp cmd COMMAND default gcc c I src dir g gnatq specifies the command used to compile a single file in the application make cmd COMMAND default gnatmake main arI src dir aO0 obj dir g gnatq cargs comp opt bargs bind opt largs link opt specifies the command used to recompile the whole applica tion run cmd COMMAND default main specifies the command used to run the application debug cmd COMMAND default gdb main specifies the command used to debug the application gnatxref and gnatfind only take into account the src air and obj dir lines and ignore the others 214 28 May 2002 Chapter 12 The Cross Referencing Tools gnatxref and gnat find 12 4 Regular Expressions in gnat find and gnatxref As specified in the section about gnat find the pattern can be a regular expression Actually there are to set of regular expressions which are recognized by the program globbing patterns regexp term term term term term term These are the most usual regular expression They are the
18. Elaboration checks 61 180 Elaboration control 177 205 Elaboration of library tasks 192 Elaboration order control 35 Eliminate 3 1 4A EARS C ARE 261 End of source file 15 Error messages suppressing 44 BUC Coding eese 18 EXCEPCIONS v ec EH IE 278 Export o ha DO e RS XR Ds 268 EES iud e eun dutem lA 15 File names 20 21 File naming schemes alternative 21 Foreign Languages 28 Fortran g enisapegsapee dde pri 29 Free Documentation License GNU 333 G BADA Se isu Se pun PIE DE 273 Generic formal parameters 64 Generics iiss deg cde RR Re 24 280 Gide aa s ei e ceu ub eer 9 GMEM gnatmem 248 GNAT cec cheers 109 283 GNAT Abnormal Termination or Failure to Terminate 05 281 GNAT compilation model 15 GNAT library 36 EnatadG essi ete RR 21 132 gnat argc cnsghendeea berba dg 108 gnat argv aevi adir eda xen 108 GNAT STACK LIMIT 62 Brat Tes Lata aa ced e teu 37 GMa bind eek a eb n eres 75 GNatCHOP maireta cece ee raad 125 nateLime cease ee vede vedi 261 344 gnatfind cee eee eee 209 BRAK i ae ae ad DE An ae 221 gnatlink vod ono Ore d eR Rt 111 gnatls o d ieee chee cda gd e eye 229 gnatmake icc ds edidere enn eas 115 GNALMEM sso A 58b 61i lod ene 247 natpLep
19. File Name amp ads A string list expression is either a simple string list expression or a com pound string list expression A simplestring list expression is one of the following e A parenthesized list of zero or more string expressions separated by commas File_Names File_Name gnat adc File_Name amp orig Empty_List e A string list valued variable reference e A string list valued attribute reference A compound string list expression is the concatenation using of a simple string list expression and an expression Note that each term in a compound string list expression except the first may be either a string expression or a string list expression File_Name_List amp File_Name One string in this list Extended_File_Name_List File_Name_List amp File_Name amp orig Two strings Big_List File Name List amp Extended File Name List Concatenation of two string lists three strings Illegal List gnat adc amp Extended File Name List Illegal must start with a string list 10 3 4 String Types The value of a variable may be restricted to a list of string literals The restricted list of string literals is given in a string type declaration 149 GNAT User s Guide for Unix Platforms Here is an example of a string type declaration type OS is NT nt Unix Linux other 0 Variables of a string type are called typed variables all other variables are
20. GNAT User s Guide for Unix Platforms No order exists No order of elaboration exists which follows the rules taking into account any Elaborate Elaborate All Of Elaborate _ Body pragmas In this case an Ada 95 compiler must di agnose the situation at bind time and refuse to build an executable program One or more orders exist all incorrect One or more acceptable elaboration orders exists and all of them generate an elaboration order problem In this case the binder can build an executable program but Program Error Will be raised when the program is run Several orders exist some right some incorrect One or more acceptable elaboration orders exists and some of them work and some do not The programmer has not con trolled theorder of elaboration sothe binder may or may not pick one of the correct orders and the program may or may not raise an exception when it is run This is the worst case because it means that the program may fail when moved to another compiler or even another version of the same com piler One or more orders exists all correct One ore more acceptable elaboration orders exist and all of them work In this case the program runs successfully This state of affairs can be guaranteed by following the rule we gave above but may be true even if the ruleis not followed Note that one additional advantage of following our Elaborate All ruleis that the program continues to stay in the ideal all orders OK
21. Generate Source Reference pragmas Use this switch if the output files are regarded as temporary and devel opment is to be done in terms of the original unchopped file This switch causes Source Reference pragmas to be inserted into each of the generated files to refers back to the original file name and line number The result is that all error messages refer back to the original unchopped file In addition the debugging information placed into the object file when the g switch of gcc or gnatmake is specified also refers back tothis original file so that tools like profilers and debuggers will give information in terms of the original unchopped file If the original file to be chopped itself contains a Source _ Reference pragma referencing a third file then gnatchop respects this pragma and the generated source Reference pragmas in the chopped file refer to the original file with appropriate line numbers This is particularly useful when gnatchop iS used in conjunction with gnatprep to compile files that contain preprocessing statements and multiple units Causes gnatchop to operate in verbose mode The version number and copyright notice are output as well as exact copies of the gnat1 commands spawned to obtain the chop control information Overwrite existing file names Normally gnat chop regards it as a fatal error if there is already a file with the same name as a file it would otherwise output in other words if the files to be
22. Init Constants spec Constants spec Calc spec Main body 206 23 May 2002 Chapter 11 Elaboration Order Handling in GNAT Init_Constants body and Init_Constants spec Init_Constants body Constants spec Calc spec Main body There is no language rule to prefer one or the other both are correct from an order of elaboration point of view But the programmatic effects of the two orders are very different In the first the elaboration routine of calc initializes z to zero and then the main program runs with this value of zero But in the second order the elaboration routine of calc runs after the body of Init Constants has set x and y and thus z is set to 7 before Main runs Onecould perhaps by applying pretty clever non artificial intelligence to the situation guess that it is more likely that the second order of elaboration is the one desired but there is no formal linguistic reason to prefer one over the other In fact in this particular case GNAT will prefer the second order because of the rule that bodies are elaborated as soon as possible but it s just luck that this is what was wanted if indeed the second order was preferred If the program cares about the order of elaboration routines in a case like this it is important to specify the order required In this particular case that could have been achieved b
23. Outputs gt Processor_Signature Asm_output a Result P g P 23 May 2002 Chapter 24 Inline Assembler tell compiler that ebx ecx and edx are also destroyed Clobber gt ebx ecx edx return processor signature return Result end Signature function Features return Processor_Features is Result Processor_Features processor features returned begin execute CPUID storing the results in the Result variable Asm the assembler code cpuid execute CPUID one stored in eax processor features returned in edx Inputs Unsigned 32 Asm input a 1 edx is stored in Result Outputs gt Processor Features Asm output d Result tell compiler that ebx and ecx are also destroyed Clobber gt ebx ecx return processor signature return Result end Features end Intel CPU 325 GNAT User s Guide for Unix Platforms 326 33 May 2002 Chapter 25 Performance Considerations 25 Performance Considerations The GNAT system provides a number of options that allow a trade off between e performance of the generated code e speed of compilation e minimization of dependences and recompilation e the degree of run time checking The defaults if no options are selected aim at improving the speed of compilation and minimizing dependences at the expense of performance of the generated code e no optimization e noinlining of subprogram calls
24. Program_Error will be raised at run time function One return Float is begin return 1 0 end One begin null end Note that in this particular case it is likely that the call is safe because the function one does not access any global variables Nevertheless in Ada 95 wedonot want the validity of the check to depend on the contents of the body think about the separate compilation case so this is still wrong as we discussed in the previous sections GNAT User s Guide for Unix Platforms The error is easily corrected by rearranging the declarations so that the body of One appears before the declaration containing the call note that in Ada 95 declarations can appear in any order so there is no restriction that would prevent this reordering and if we write function One return Float function One return Float is begin return 1 0 end One Q Float One then all is well no warning is generated and no Program Error ex ception will be raised Things are more complicated when a chain of subprograms is executed function A return Integer function B return Integer function C return Integer function B return Integer is begin return A end function C return Integer is begin return B end X Integer C function A return Integer is begin return 1 end Now the call to c at elaboration time in the declaration of x is correct because the body of c is already elaborated and the
25. Same meaning as the equivalent gnatmake flag see Section 6 2 Switches for gnatmake page 116 If this switch is set gnatxref will output the parent type reference for each matching derived types If this switch is set the output file names will be preceded by their directory if the file was found in the search path If this switch is not set the directory will not be printed If this switch is set information is output only for library level entities ignoring local entities The use of this switch may accelerate gnatfind and gnatxref Equivalent to aoDIR aIDIR Specify a project file to use See Section 10 1 1 Project Files page 137 By default gnatxref and gnatfind will try to locate a project file in the current directory If a project file is either specified or found by the tools then the content of the source directory and object directory lines are added as if they had been specified respectively by a1 and ao Output only unused symbols This may be really useful if you give your main compilation unit on the command line as gnatxref Will then display every unused entity and with ed package Instead of producing the default output gnatxref will gen erate a tags filethat can be used by vi For examples how to use this feature see See Section 12 5 Examples of gnatxref 23 May 2002 Chapter 12 The Cross Referencing Tools gnatxref and gnat find Usage page 216 T
26. Set_Globals __gnat_set_globals SDP_Table_Build is a library routine used to build the exception tables See unit Ada Exceptions in files a except ads adb for full details of how zero cost exception handling works This procedure the call to it and the two following tables are all omitted if the build is in longjmp setjump exception mode procedure SDP Table Build SDP Addresses System Address SDP_Count Natural Elab_Addresses System Address Elab_Addr_Count Natural pragma Import C SDP_Table_Build __gnat_SDP_Table_Build Table of Unit_Exception_Table addresses Used for zero cost exception handling to build the top level table ST aliased constant array 1 23 of System Address Hello UET_Address Ada Text_Io UET_Address Ada Exceptions UET_Address Gnat Heap_Sort_A UET_Address System Exception_Table UET_Address System Machine_State_Operations UET_Address System Secondary_Stack UET_Address System Parameters UET_Address System Soft_Links UET_Address System Stack_Checking UET_Address System Traceback UET Address Ada Streams UET Address Ada Tags UET Address System String Ops UET Address Interfaces C Streams UET Address System File Io UET Address Ada Finalization UET Address System Finalization Root UET Address 84 ___ SSS 28 May 2002 Chapter 4 Binding Using gnatbind System Finalization_Implementation UET_Address
27. as the command prompt in the examples in this document gcc c hello adb gcc is the command used to run the compiler This compiler is capable of compiling programs in several languages including Ada 95 and C It assumes that you have given it an Ada program if the file extension is either ads or adb andit will then call the GNAT compiler to compile the specified file The c switch is required It tells gcc to only doa compilation For C programs gcc can also do linking but this capability is not used directly for Ada programs so the c switch must always be present This compile command generates a file hello o which is the ob ject file corresponding to your Ada program It also generates an Ada Library Information file ne11o a1i which contains additional infor mation used to check that an Ada program is consistent To build an executable file use gnatbind to bind the program and gnat1ink to link it The argument to both gnatbind and gnatlink isthe name of the ali file but the default extension of a1i can be omitted This means that in the most common case the argument is simply the name of the main program gnatbind hello gnatlink hello A simpler method of carrying out these steps is to usegnatmake a master program that invokes all the required compilation binding and linking tools in the correct order In particular gnatmake automatically recom piles any sources that have
28. but the restrictions on this string e g a file name or a language name depend on the individual attribute Also depending on the at tribute its specified value will need to be either a string or a string list EAT GNAT User s Guide for Unix Platforms In the Debug project we set the switches for two tools gnatmake and the compiler and thus we include corresponding packages with each package defining the Default Switches attribute with index ada Note that the package corresponding to gnatmake is named Builder The Release project is similar but with just the compiler package In project Debug above the switches starting with gnat that are specified in package compiler could have been placed in package Builder Since gnatmake transmits all such switches to the compiler Main Subprograms One of the properties of a project is its list of main subprograms actually a list of names of source files containing main subprograms with the file extension optional This property is captured in the Main attribute whose value is a list of strings If a project defines the main attribute then you do not need to identify the main subprogram s when invoking gnatmake See Section 10 13 1 gnatmake and Project Files page 166 Source File Naming Conventions Since the project files do not specify any source file naming conventions the GNAT defaults are used The mechanism for defining source file naming conventions a packa
29. common directory The file proc adb contains an Ada main 138 28 May 2002 Chapter 10 GNAT Project Manager subprogram Proc that with s package Pack We want to compile these source files under two sets of switches e When debugging we want to pass the g switch to gnatmake and the gnata gnato and gnatE switches to the compiler the compiler s output is to appear in common debug e When preparing a release version we want to pass the 02 switch to thecompiler the compiler s output is to appear in common release The GNAT project files shown below respectively debug gpr and release gpr in the common directory achieve these effects Diagrammatically common debug gpr release gpr pack ads pack adb proc adb common debug g gnata gnato gnatE proc ali proc o pack ali pack o common release 1 02 proc ali proc o pack ali pack o Here arethe project files project Debug is for bject Dir use debug for Main use proc package Builder is for Default Switches Ada use g end Builder package Compiler is for Default Switches Ada use fstack check gnata gnato gnatE end Compiler end Debug 139 GNAT User s Gui
30. gnatempath A mapping file is a way to communicate to the compiler two mappings from unit names to file names without any direc tory information and from file names to path names with full directory information These mappings are used by the compiler to short circuit the path search A mapping file is a sequence of sets of three lines In each set the first line is the unit name in lower case with s appended for specifications and b appended for bodies the second lineis the filename and thethird lineis the path name Example main b main 2 ada gnat projecti sources main 2 ada When the switch gnatem is specified the compiler will cre ate in memory the two mappings from the specified file If there is any problem non existent file truncated file or du plicate entries no mapping will be created Several gnatem switches may be specified however only the last one on the command line will betaken into account When using a project file gnatmake create a temporary map ping file and communicates it to the compiler using this switch 3 3 Search Paths and the Run Time Library RTL With the GNAT source based library system the compiler must be able to find source files for units that are needed by the unit being compiled Search paths are used to guide this process The compiler compiles one source file whose name must be given explicitly on the command line In other words no searching is done for this file To
31. gt Processor Register Asm output g Original Flags Processor Register Asm output g Modified Flags tell compiler eax is destroyed Clobber gt eax check if CPUID is supported if Original_Flags ID_Flag Modified_Flags ID_Flag then return True ID flag was modified else return False ID flag unchanged end if check for CPUID end Has_CPUID function CPUID_Level return Natural is Level Unsigned_32 returned support level begin execute CPUID storing the results in the Level register Asm the assembler code cpuid execute CPUID zero is stored in eax returning the support level in eax Inputs gt Unsigned_32 Asm_input a 0 eax is stored in Level Outputs gt Unsigned_32 Asm_output a Level 23 May 2002 Chapter 24 Inline Assembler tell compiler ebx ecx and edx registers are destroyed Clobber gt ebx ecx edx return the support level return Natural Level end CPUID_Level The vendor ID string is returned in the ebx ecx and edx register after executing the CPUID instruction with eax set to zero In case of a true Intel processor the string returned is GenuineIntel function Vendor_ID return String is Ebx Ecx Edx Unsigned_Register registers containing the vendor ID string Vendor_ID String 1 12 the vendor ID string begin execute CPUID storing the resu
32. gt Unsigned 32 Asm Output a Flags Put Line Flags register amp Flags Img end Get Flags 2 The a constraint tells the compiler that the Flags variable will come from the eax register Hereis the resulting code APP pushfl popl eax NO_APP movl eax 40 ebp The compiler generated the store of eax into Flags after expanding the assembler code Actually there was no need to pop the flags into the eax register more simply we could just pop the flags directly into the program variable with Interfaces use Interfaces with Ada Text_I0 use Ada Text I0 with System Machine Code use System Machine Code procedure Get Flags 3 is Flags Unsigned 32 use ASCII begin Asm pushfl amp LF amp HT amp push flags on stack pop 0 save flags in Flags Outputs gt Unsigned_32 Asm_Output g Flags Put Line Flags register amp Flags Img end Get Flags 3 299 GNAT User s Guide for Unix Platforms 24 4 Input Variables in Inline Assembler Theexamplein this section illustrates how to specify the source operands for assembly language statements The program simply increments its input value by 1 with Interfaces use Interfaces with Ada Text_I0 use Ada Text I0 with System Machine_Code use System Machine_Code procedure Increment is function Incr Value Unsigned_32 return Unsigned_32 is Result Unsigned_32 begin Asm incl 0 Inputs gt Unsigned_32 Asm_Input
33. hello adb then a file hello adb dg will be written The debugging information generated by the gcc g switch will refer to the generated xxx dg file This allows you to do source level debugging using the gen erated code which is sometimes useful for com plex code for example to find out exactly which part of a complex construction raised an excep tion This switch also suppress generation of cross reference information see gnatx 69 GNAT User s Guide for Unix Platforms gnatC In the generated debugging information and also in the case of long external names the compiler uses a compression mechanism if the name is very long This compression method uses a check sum and avoids trouble on some operating sys tems which have difficulty with very long names The gnatc switch forces this compression ap proach to be used on all external names and names in the debugging information tables This reduces the size of the generated executable at the expense of making the naming scheme more complex The compression only affects the quali fication of the name Thus a name in the source Very_Long_Package Very_Long_Inner_Package Var would normally appear in these tables as very_long_package__very_long_inner_package__var but if the gnatc switch is used then the name appears as XCb7e0c705__var Here b7e0c705 is a compressed encoding of the qualification prefix The GNAT Ada aware ver sion of GDB understands these encod
34. itis published as a printed book Werecommend this License principally for works whose purpose is instruction or reference 1 APPLICABILITY AND DEFINITIONS This License applies to any manual or other work that contains a notice placed by the copyright holder saying it can be distributed under the terms of this License The Document below refers to any such manual or work Any member of the publicis a licensee andis addressed as you A Modified Version of the Document means any work containingthe Document or a portion of it either copied verbatim or with modifications and or translated into another language 333 GNAT User s Guide for Unix Platforms A Secondary Section is a named appendix or a front matter section of the Document that deals exclusively with the relationship of the pub lishers or authors of the Document to the Document s overall subject or to related matters and contains nothing that could fall directly within that overall subject For example if the Document is in part a textbook of mathematics a Secondary Section may not explain any mathemat ics Therelationship could be a matter of historical connection with the subject or with related matters or of legal commercial philosophical ethical or political position regarding them The Invariant Sections are certain Secondary Sections whose titles are designated as being those of Invariant Sections in the notice that says that the Document is rel
35. means checking variables in the preceding code and in the calling subprogram to verify that the value observed is explainable from other values one must apply the procedure recursively to those other values or re running the code and stopping a little earlier perhaps before the call and stepping to better see how the variable obtained the value in question or continuing to step from the point 329 GNAT User s Guide for Unix Platforms of the strange value to see if code motion had simply moved the variable s assignments later 25 4 Inlining of Subprograms A call to a subprogram in the current unit is inlined if all the following conditions are met e The optimization level is at least o1 e The called subprogram is suitable for inlining It must be small enough and not contain nested subprograms or anything else that gcc cannot support in inlined subprograms e The call occurs after the definition of the body of the subprogram e Either pragma Inline applies to the subprogram or it is small and automatic inlining optimization level 03 is specified Calls to subprograms in with ed units are normally not inlined To achieve this level of inlining the following conditions must all be true e The optimization level is at least o1 e The called subprogram is suitable for inlining It must be small enough and not contain nested subprograms or anything else gcc cannot support in inlined subprograms e Thecall appears in a body
36. need to use quotes around binder name f binder name COnN tains spaces or other separator characters As an example GNATBIND bar x y Will instruct gnatmake to use bar x y as your binder Binder switches that are normally ap pended by gnatmake tO gnatbind are now appended to the end of bar x y GNATLINK linker name Program used for linking The default is gnatlink You need to use quotes around linker nameif linker name CON tains spaces or other separator characters As an example GNATLINK lan x y Will instruct gnatmake to use lan x y as your linker Linker switches that are normally ap pended by gnatmake to gnatlink are now appended to the end of lan x y a Consider all files in the make process even the GNAT in ternal system files for example the predefined Ada library 116 SSS 28 May 2002 Chapter 6 The GNAT Make Program gnatmake files as well as any locked files Locked files are files whose ALI file is write protected By default gnatmake does not check these files because the assumption is that the GNAT internal files are properly up to date and alsothat any write protected ALI files have been properly installed Note that if there is an installation problem such that one of these files is not up to date it will be properly caught by the binder You may have to specify this switch if you are working on GNAT itself a is also useful in conjunction with if you need to recompile an
37. not in a package spec e Thereis a pragma Inline for the subprogram e The gnatn switch is used in the scc command line Note that specifying the gnatn switch causes additional compilation dependencies Consider the following 330 A383 May 2002 Chapter 25 Performance Considerations package R is procedure Q pragma Inline Q end R package body R is end R with R procedure Main is begin R Q end Main With the default behavior no gnatn Switch specified the compilation of the Main procedure depends only on its own source main adb and the spec of the package in file r ads This means that editing the body of r does not require recompiling Main On the other hand the call R Q is not inlined under these circum stances If the gnatn Switch is present when main is compiled the call will be inlined if the body of o is small enough but now Main depends on the body of r in r adb as well as on the spec This means that if this body is edited the main program must be recompiled Note that this extra dependency occurs whether or not the call isin fact inlined by gcc Theuse of front end inlining with anatN generates similar additional dependencies Note The fno inline switch can be used to prevent all inlining This switch overrides all other conditions and ensures that no inlining occurs The extra dependences resulting from gnatn will still be active even if this switch is used to suppre
38. of the child project see Section 10 3 Project File Syntax page 147 An inherited source file retains any switches specified in the parent project For example if the project Utilities contains the specification and the body of an Ada package util ro then the project Modified _ Utilities Can contain a new body for package util ro The original body of ucii ro will not be considered in program builds However the package specification will still be found in the project utilities A child project can haveonl y one parent but it may import any number of other projects A project is not allowed to import directly or indirectly at the same time a child project and any of its ancestors 10 7 External References in Project Files A project file may contain references to external variables such refer ences are called external references An external variable is either defined as part of the environment an environment variable in Unix for example or else specified on the command line via the xvbl value switch If both then the command line valueis used An external reference is denoted by the built in function external which returns a string value This function has two forms e external external variable name e external external variable name default value Each parameter must be a string literal For example 159 GNAT User s Guide for Unix Platforms external USER external 0S Linux In the form
39. page 17 Note that brackets coding is always accepted even if one of the other options is specified so for example gnatws specifies that both brackets and uTF 8 encodings will be recognized The units that are with ed directly or indirectly will be scanned using the specified representation scheme and so if one of the non brackets scheme is used it must be used consistently throughout the program However since brackets encoding is always recognized it may be conveniently used in stan dard libraries allowingthese libraries to be used with any of GNAT User s Guide for Unix Platforms the available coding schemes scheme If no gnatw param eter is present then the default representation is Brackets encoding only Note that the wide character representation that is specified explicitly or by default for themain program also acts as the default encoding used for Wide Text I O files if not specifically overridden by a WCEM form parameter 3 2 12 File Naming Control gnatkn Activates file name krunching n a decimal integer in the range 1 999 indicates the maximum allowable length of a file name not including the ads or adb extension The default is not to enable file name krunching For thesourcefilenamingrules See Section 2 3 FileNaming Rules page 19 3 2 13 Subprogram Inlining Control gnatn gnatN Then hereis intended to suggest the first syllable of the word inline GNAT recogniz
40. q n i file Gnatmem must be supplied with the executable to examine followed by its run time inputs For example if a program is executed with the command my program argi arg2 then it can berun under gnatmem control using the command gnatmem my program argi arg2 The program is transparently executed under the control of the de bugger Section 23 1 The GNAT Debugger GDB page 273 This does not affect the behavior of the program except for sensitive real time programs When the program has completed execution gnatmem OUt puts a report containing general allocation deallocation information and potential memory leak For better results the user program should be compiled with debugging options Section 3 2 Switches for gcc page 38 Here is a simple example of use HHHK HHK K KK KKK KKK debut CC 247 GNAT User s Guide for Unix Platforms gnatmem test_gm Global information Total number of allocations y gt 45 Total number of deallocations 6 Final Water Mark non freed mem 11 29 Kilobytes High Water Mark 11 40 Kilobytes Allocation Root 2 Number of non freed allocations 11 Final Water Mark non freed mem 1 16 Kilobytes High Water Mark 1 27 Kilobytes Backtrace test gm adb 23 test gm alloc The first block of output give general information In this case the Ada construct new was executed 45 times and only 6 calls to an unchecked deallocation routine occurred Subsequent paragraphs d
41. system exceptions spec system parameters body gnat heap sort a body interfaces c streams spec interfaces c streams body system exception table spec system exception table body ada io exceptions spec system storage elements spec system storage elements body system machine state operations spec system machine state operations body system secondary_stack spec system stack checking spec system soft links spec system soft links body system stack checking body system secondary_stack body system standard library body 100 23 May 2002 Chapter 4 Binding Using gnatbind system string_ops spec system string_ops body ada tags spec ada tags body ada streams spec system finalization_root spec system finalization_root body system string_ops_concat_3 spec system string_ops_concat_3 body system traceback spec system traceback body ada exceptions body system unsigned_types spec system stream_attributes spec system stream_attributes body system finalization_implementation spec system finalization_implementation body ada finalization spec ada finalization body ada finalization list_controller spec ada finalization list_controller body system file_control_block spec system file_io spec system file_io body ada text_io spec ada text_io body hello body END E
42. system__file_control_block___elabs _elabb ada__text_io___elabs ada__text_io___elabb system__file_io_ __gnat_SDP_Table_Build amp st 23 ea 23 __gnat_set_globals 1 Main Priority 1 Time_Slice_Value b WC_Encoding es Locking Policy AS Queuing Policy HE Tasking Dispatching Policy 0 Finalization routine address not used anymore 0 Unreserve_All_Interrupts 0 Exception_Tracebacks gnat inside elab final code 1 if ada__exceptions_E 0 ada__exceptions___elabs gt if system__exceptions_E 0 system__exceptions___elabs system__exceptions_E if interfaces__c_streams_E 0 interfaces__c_streams___elabs interfaces__c_streams_E 1 if system__exception_table_E 0 _elabb system__exception_table_E system__exception_table_ if ada__io_exceptions_E 0 ada__io_exceptions___elabs 9 ___ 53 May 2002 Chapter 4 Binding Using gnatbind ada__io_exceptions_E gt if system stack checking E 0 system stack checking elabs gt if system soft links E 0 system soft links elabb system soft links E gt system__stack_checking_E 1 if system__secondary_stack_E 0 system__secondary_stack___elabb system__secondary_stack_E if ada tags E 0 ada tags elabs if ada tags E 0 1 elabb ada
43. the external name of this procedure will be ada hello 268 May 2002 Chapter 22 Other Utility Programs 22 4 Ada Mode for Glide The Glide mode for programming in Ada both Ada83 and Ada95 helps the user in Understanding existing code and facilitates writing new code It furthermore provides some utility functions for easier integration of standard E macs features when programming in Ada 22 4 1 General Features e Full ntegrated Development Environment e support of project files for the configuration directories com pilation options e compiling and stepping through error messages e running and debugging your applications within Glide e easy to use for beginners by pull down menus e user configurable by many user option variables 22 4 2 Ada Mode Features That Help Understanding Code e functions for easy and quick stepping through Ada code e getting cross reference information for identifiers e g find the defin ing place by a keystroke e displaying an index menu of types and subprograms and move point to the chosen one e automatic color highlighting of the various entities in Ada code 22 4 3 Glide Support for Writing Ada Code e Switching between spec and body files with possible autogeneration of body files e automatic formating of subprograms parameter lists e automatic smart indentation accor
44. type OS Type is Linux Unix NT VMS OS OS Type external 0S Linux package Compiler is case 0S is when Linux Unix gt for Default_Switches Ada use gnath when NT gt for Default_Switches Ada use gnatP when others gt end case end Compiler end MyProj The syntax of a case construction is based on the Ada case statement although there is no nu11 construction for empty alternatives Following the reserved word case there is the case variable a typed string variable thereserved word is and then a sequence of one or more alternatives Each alternative comprises the reserved word when either a list of literal strings separated by the character or the reserved 154 23 May 2002 Chapter 10 GNAT Project Manager word others and the gt token Each literal string must belong to the string type that is the type of the case variable An others alternative if present must occur last The end case sequence terminates the case construction After each gt there are zero or more constructions The only con structions allowed in a case construction are other case constructions and attribute declarations String type declarations variable declara tions and package declarations are not allowed The value of the case variable is often given by an external reference see Section 10 7 External References in Project Files page 159 10 4 Objects and Sources in
45. 2 ok ei ga Se ees Aene 225 gnatstub 0 eee eee eee 259 gnatIref sori ease ete G ug eda t 209 GNU Free Documentation License 333 GNU make iie ERES 241 GN Ds en ettet be tete tn en 9 H Inline 5o 4r v PREX ER 25 330 Inlinihg speet ose men Rs 36 Intel CPU package body 320 Intel CPU package specification 314 Interfaces quy s 109 283 Interfacing to Ada 28 Interfacing to Assembler 29 Interfacing to C 0 29 Interfacing to C 29 Interfacing to COBOL 29 Interfacing to Fortran 29 Internal trees writing to file 67 Hatin id 4230022022 025324 28 15 16 Latil 2 xke na ae RR AE 16 Latin 3ce o Deed ee EA AE ENG 16 Latinzd ies D RLEAA ERA 16 Latin Diaries be cate tate ke barer 16 LR i ishist gin ctgach ine ERREUR ls 15 Library browser 229 Library tasks elaboration issues 192 Library building installing 233 License GNU Free Documentation 333 Linker libraries 120 23 May 2002 M Machine_Overflows 61 Main Program esses 89 MAR Gas Eina fare dins teg tiu vent atone 241 Makefile sd os p enn Pob ENT OR 241 Mixed Language Programming 27 Multiple units syntax checking 63 n gnatmem 249 No code generated 37 No_Entry_Calls_In_Elaborat
46. 5812234 Leer LIRE 24 S ppress 52s BL Lead 60 327 Suppressing checks 60 Systeti s ped DeL Ep 109 283 System I0 gas poc shed aad 72 T Task switching 280 Tasks ssi es ons Eau Sn 279 Time Shemg wae CR RL 62 Time stamp checks in binder 103 tracebacks i cor oes Gallet ae 284 traceback non symbolic 284 traceback symbolic 290 Tree file pere 262 Typographical conventions 3 U Unsuppress ee sess 61 327 Upper Half Coding 17 GNAT User s Guide for Unix Platforms V Validity Checking 52 Version skew avoided by gnatmake 6 Volatile parameter 304 MIS n L a to Ld t P eri D E S 15 W Warning messages 45 WATT ES u eee sis nates 103 Writing internal trees 67 Z Zero Cost Exceptions 84 23 May 2002 Table of Contents About This Guide L What This Guide ContaiNS c c c c c 1 What You Should Know before Reading This Guide 3 Related Information 0 0 cece n 3 CONVENE OMS c b e a car ate RUD ee res 3 1 Getting Started with GNAT 5 1 1 Running GNU d prb eR PIROhsU SUN Rr UEPELOMS 5 12 RunningaSimpleAdaProgramM 5 13 Runninga Program with MultipleUnits 7 14
47. Accessing Not Allocated Storage e GNAT Debug Pools Accessing Deallocated Storage e GNAT Debug Pools Freeing Not Allocated Storage e GNAT Debug Pools Freeing Deallocated Storage For types associated with a Debug Pool dynamicallocation is performed usingthe standard GNAT allocation routine References to all allocated chunks of memory are kept in an internal dictionary The deallocation strategy consists in not releasing the memory to the underlying system but rather to fill it with a memory pattern easily recognizable during debugging sessions The memory pattern is the old IBM hexadecimal convention 162DEADBEEF X Upon each dereference a check is made that the access value denotes a properly allocated memory location Here is a complete example of use of pebug Pools that includes typical in stances of memory corruption with Gnat Io use Gnat Io with Unchecked Deallocation 255 GNAT User s Guide for Unix Platforms with Unchecked_Conversion with GNAT Debug_Pools with System Storage Elements with Ada Exceptions use Ada Exceptions procedure Debug_Pool_Test is type T is access Integer type U is access all T P GNAT Debug_Pools Debug_Pool for T Storage_Pool use P procedure Free is new Unchecked_Deallocation Integer T function UC is new Unchecked_Conversion U T A B aliased T procedure Info is new GNAT Debug Pools Print Info Put Line begin Info P A new Integer B new Integer
48. Assembler 300 24 5 Inlining Inline Assembler Code 301 24 6 Other asm Functionality c 303 24 6 1 Theclobber Parameter 303 24 6 2 Thevolatile Parameter 304 24 7 A Complete Exampl Qa 304 24 7 1 Check cPUProcedUre 304 24 7 2 intel cPU Package Specification 314 24 7 3 Intel cpu Package Bogy 320 25 Performance Considerations 327 25 1 Controlling Run Time CheckS 327 25 2 Optimization LevAS 88258 328 25 3 Debugging Optimized Code 328 25 4 Inliningof SubprograMs 330 AppendixA GNU Free Documentation License viij 59 May 2002 GNAT User s Guide for Unix Platforms 273 May 2002
49. B A Info P Free A begin Put Line Integer Image B all exception when E others gt Put Line raised amp Exception Name E end begin Free B exception when E others gt Put Line raised amp Exception Name E end B UC A Access begin Put Line Integer Image B alD exception when E others gt Put Line raised amp Exception Name E end begin Free B 256 28 May 2002 Chapter 19 Finding Memory Problems with GNAT Debug Pool exception when E end Info P others gt Put Line raised amp Exception Name E end Debug_Pool_Test The debug pool mechanism provides the following precise diagnostics on the execution of this erroneous program Debug Pool info Total allocated bytes 0 Total deallocated bytes 0 Current Water Mark 0 High Water Mark 0 Debug Pool info Total allocated bytes 8 Total deallocated bytes 0 Current Water Mark 8 High Water Mark 8 raised raised raised raised GNAT DEBUG_POOLS ACCESSING_DEALLOCATED_STORAGE GNAT DEBUG_POOLS FREEING_DEALLOCATED_STORAGE GNAT DEBUG_POOLS ACCESSING_NOT_ALLOCATED_STORAGE GNAT DEBUG_POOLS FREEING_NOT_ALLOCATED_STORAGE Debug Pool info Total allocated bytes 8 Total deallocated bytes 4 Current Water Mark 4 High Water Mark 8 257 GNAT User s Guide for Un
50. Import Ada E053 ada io exceptions E E017 Boolean pragma Import Ada E017 system exceptions E E024 Boolean pragma Import Ada E024 system secondary stack E E030 Boolean pragma Import Ada E030 system stack checking E E028 Boolean pragma Import Ada E028 system soft links E E035 Boolean pragma Import Ada E035 ada tags E E033 Boolean pragma Import Ada E033 ada streams E E046 Boolean pragma Import Ada E046 system finalization root E E048 Boolean pragma Import Ada E048 system finalization implementation E E044 Boolean pragma Import Ada E044 ada finalization E E057 Boolean pragma Import Ada E057 ada finalization list controller E E055 Boolean pragma Import Ada E055 system file control block E E042 Boolean pragma Import Ada E042 system file io E E006 Boolean pragma Import Ada E006 ada text io E Set Globals is a library routine that stores away the value of the indicated set of global values in global variables within the library procedure Set Globals Main Priority Integer Time Slice Value Integer WC Encoding Character Locking Policy Character GNAT User s Guide for Unix Platforms Queuing_Policy Character Task_Dispatching_Policy Character Adafinal System Address Unreserve_All_Interrupts Integer Exception_Tracebacks Integer pragma Import C
51. MyPack MyChild use mypack mychild spec Implementation You can use the Implementation attribute an associative array to define the source file name for an individual Ada compilation unit s body possibly a subunit The array in dex must bea string literal that identifies the Ada unit case 163 GNAT User s Guide for Unix Platforms insensitive The value of this attribute must be a string that identifies the file that contains this unit s body or sub unit case sensitive or insensitive depending on the operating system for Implementation MyPack MyChild use mypack mychild 10 11 Library Projects Library projects are projects whose object code is placed in a library Note that this facility is not yet supported on all platforms To create a library project you need to define in its project file two project level attributes Library Name and Library Dir Additionally you may define the library related attributes Library Kind Library_ Version and Library Elaboration The Library Name attribute has a string value that must start with a letter and include only letters and digits The Library Dir attribute has a string value that designates the path absolute or relative of the directory where the library will reside It must designate an existing directory and this directory needs to be different from the project s object directory It also needs to be writable If both Library Name and Library Dir are specified a
52. Project Files Each project has exactly one object directory and one or more source directories The source directories must contain at least one source file unless the project file explicitly specifies that no source files are present see Section 10 4 4 Source File Names page 157 10 4 1 Object Directory The object directory for a project is the directory containing the com piler s output such as aut files and object files for the project s imme diate sources Note that for inherited sources when extending a parent project the parent project s object directory is used The object directory is given by the value of the attribute object Dir in the project file for Object_Dir use objects Theattribute object Dir has a string value the path name of the object directory The path name may be absolute or relative to the directory of the project file This directory must already exist and be readable and writable By default when the attribute object Dir is not given an explicit value or when its value is the empty string the object directory is the same as the directory containing the project file 10 4 2 Exec Directory The exec directory for a project is the directory containing the executa bles for the project s main subprograms The exec directory is given by the value of the attribute Exec Dir in the project file 155 GNAT User s Guide for Unix Platforms for Exec Dir use executables The attrib
53. Project Manager Each simple attribute has a default value the empty string for string valued attributes and the empty list for string list valued attributes Similar to variable declarations an attribute declaration defines a new value for an attribute Examples of simple attribute declarations for Object_Dir use objects for Source Dirs use units test drivers A simple attribute declaration starts with the reserved word for fol lowed by the name of the attribute followed by the reserved word use followed by an expression whose kind depends on the attribute fol lowed by a semicolon Attributes may be referenced in expressions The general form for such a reference iS lt entity gt lt attribute gt the entity for which the attribute is defined followed by an apostrophe followed by the name of the attribute For associative array attributes a litteral string between parentheses need to be supplied as index Examples are project Object_Dir Naming Dot Replacement Imported Project Source Dirs Imported Project Naming Casing Builder Default_Switches Ada The entity may be e project for an attribute of the current project e Thename of an existing package of the current project e Thename of an imported project e Thename of a parent project extended by the current project e An imported parent project name followed by a dot followed by a package name Example project Prj is for Sourc
54. Usingthegnatmake UtilltY eee eee eee 8 15 Introduction to Glide and GVD 9 15 1 Building a New Program with Glide 9 15 2 Simple Debugging with GVD 11 15 3 Other Glide FeatUreS 13 2 TheGNAT Compilation Model 15 2 1 SourceRepresentatiO0N 15 2 2 Foreign Language Representation 16 22 1 Latnelic esce eor eon 16 2 2 2 Other 8 Bit CodES 16 2 2 3 Wide Character Encodings 17 2 3 File Naming RUIGS 2 nics os see ree tetas RP Rr 19 2 4 Using Other FileNames 20 2 Alternative File Naming Schemes 21 2 6 Generating Object FileS 2 2 23 2 7 Source Dependencie S cece eee eee eee eee 24 2 8 TheAda Library Information Fil S 26 2 9 Binding an AdaProgramM 26 2 10 MixedLanguageProgramming 27 2 10 1 InterfacingtOC 27 2 10 2 Calling Conventions 28 2 11 Building Mixed Ada amp C Programs 30 2 11 1 InterfacingtOC 30 2 112 Linkinga Mixed C amp Ada Program 31 2 11 3 ASimpleExample 32 2 11 4 Adapting the Run Time to a New C Comp
55. Ut i1s Here is the exact chain of events we are worrying about 1 In the body of Dec1s a call is made from within the body of a library task to a subprogram in the packageut iis Sincethis call may occur at elaboration time given that the task is activated at elaboration time we have to assume the worst i e that the call does happen at elaboration time 2 This means that the body and spec of ut i 1 must be elaborated before the body of Dec1s so that this call does not cause an access before elaboration 3 Within the body of util specifically within the body of util Put_ val there may be calls to any unit with ed by this package 4 Onesuch with ed package is package Dec1s so there might be a call to a subprogram in Decls in Put val In fact there is such a call in this example but we would have to assume that there was such a call even if it were not there since we are not supposed to write the body of Dec1s knowing what is in the body of utils certainly in the case of the static elaboration model the compiler does not know what is in other bodies and must assume the worst 5 This means that the spec and body of Dec1s must also be el aborated before we elaborate the unit containing the call but that unit is Decls This means that the body of Dec1s must be elaborated before itself and that s a circularity Indeed if you add an explicit pragma Elaborate All for utils in the body of necis you will get a true Ada Refe
56. a Value Outputs gt Unsigned_32 Asm_Output a Result return Result end Incr Value Unsigned_32 begin Value 5 Put Line Value before is amp Value Img Value Incr Value Put_Line Value after is amp Value Img end Increment The outputs parameter to Asm specifies that the result will bein the eax register and that it is to be stored in the Result variable The Inputs parameter looks much like the outputs parameter but with an Asm Input attribute The constraint indicating an output value is not present You can have multiple input variables in the same way that you can have more than one output variable The parameter count 960 1 etc now starts at the first input state ment and continues with the output statements When both parame ters use the same variable the compiler will treat them as the same n operand which is the case here Just as the outputs parameter causes the register to be stored into the target variable after execution of the assembler statements so does the Inputs parameter cause its variable to be loaded into the register before execution of the assembler statements 300 3 May 2002 Chapter 24 Inline Assembler Thus the effect of the Asm invocation is 1 load the 32 bit value of value into eax 2 execute the incl eax instruction 3 store the contents of eax into the Result variable The resulting assembler file with 02 optimization contai
57. a dedaration in several senses e Thevariable name does not need to be defined previously e The declaration establishes the kind string versus string list of the variable and later declarations of the same variable need to be consistent with this A string variable declaration typed or untyped declares a variable whose valueis a string This variablemay be used as a string expression File Name readme txt Saved File Name File Name amp saved A string list variable declaration declares a variable whose valueis a list of strings Thelist may contain any number zero or more of strings 150 23 May 2002 Chapter 10 GNAT Project Manager Empty_List List_With_One_Element gnaty List With Two Elements List With One Element amp gnatg Long List main ada packi_ ada packi ada pack2_ ada pack2 ada util ada util ada The same typed variable may not be declared more than once at project level and it may not be declared more than once in any package it is in effect a constant or a readonly variable The same untyped variable may be declared several times In this case the new value replaces the old one and any subsequent reference to the variable uses the new value However as noted above if a variable has been declared as a string all subsequent dedarations must give
58. a full list of the induded object files This switch option is most useful when you want to see what set of object files are being used in the link step Very verbose mode Requests that the compiler operate in verbose mode when it compiles the binder file and that the system linker run in verbose mode o exec name b target 112 exec name specifies an alternate name for the generated ex ecutable program If this switch is omitted the executable has the same name as the main unit For example gnat link try ali creates an executable called try Compile your program to run on target which is the name of a system configuration You must have a GNAT cross compiler built if target is not the same as your host system 23 May 2002 Chapter 5 Linking Using gnat 1ink Bdir Load compiler executables for example gnat 1 the Ada com piler from dir instead of the default location Only use this switch when multiple versions of the GNAT compiler are available See the gcc manual page for further details You would normally use the b or v switch instead GCC compiler name Program used for compiling the binder file The default S gcc You need to use quotes around compiler name if compiler name COntains spaces or other separator char acters As an example Gcc foo x y will instruct gnatlinktOUSefoo x y as your compiler Note that switch c is always inserted after your command name Thus in the above exampl
59. all link steps performed by gnatmake 6 4 Notes on the Command Line This section contains some additional useful notes on the operation of the gnatmake command e If gnatmake finds no ALI files it recompiles the main program and all other units required by the main program This means that 121 GNAT User s Guide for Unix Platforms gnatmake Can be used for the initial compile as well as during sub sequent steps of the development cycle e If you enter gnatmake file adb where file adb is a subunit or body of a generic unit gnatmake recompiles file adb because it finds no ALI and stops issuing a warning e In gnatmake the switch 1 is used to specify both source and library file paths Use ar instead if you just want to specify source paths only and ao if you want to spedify library paths only e gnatmake examines both an ALI file and its corresponding object file for consistency If an ALI is more recent than its correspond ing object or if the object file is missing the corresponding source will be recompiled Note that gnatmake expects an ALI and the corresponding object file to bein the same directory e gnatmake Will ignore any files whose ALI file is write protected This may conveniently be used to exdude standard libraries from consideration and in particular it means that the use of the f switch will not recompile these files unless a is also specified e gnatmake has been designed to make the
60. all units in the partition The Elab_Spec and Elab_Body attributes generate references to the implicit elaboration procedures generated by the compiler for each unit that requires elaboration if not E040 then Interfaces C_Streams Elab_Spec end if E040 True if not E008 then Ada Exceptions Elab_Spec end if if not E014 then System Exception Table Elab Body E014 True end if if not E053 then Ada Io Exceptions Elab Spec E053 True end if if not E017 then System Exceptions Elab Spec E017 True end if if not E030 then System Stack Checking Elab Spec end if if not E028 then System Soft Links Elab Body E028 True end if E030 True if not E024 then System Secondary_Stack Elab_Body E024 True end if if not E035 then Ada Tags Elab_Spec end if if not E035 then Ada Tags Elab Body EO35 True end if 87 GNAT User s Guide for Unix Platforms if not E033 then Ada Streams Elab_Spec E033 True end if if not E046 then System Finalization_Root Elab_Spec end if E046 True if not E008 then Ada Exceptions Elab_Body E008 True end if if not E048 then System Finalization_Implementation Elab_Spec end if if not E048 then System Finalization_Implementation Elab_Body E048 True end if if not E044 then Ada Finalization Elab_Spec end if E044 True if not E057 then Ada Finalization List_Control
61. allowed in identifiers with upper case and lowercase equivalence IBM PC code page 437 This code page is the normal default for PCs in the U S It corresponds to the original IBM PC character set This set has some but not all of the extended Latin 1 letters but these letters do not have the same encoding as Latin 1 In this mode these letters are allowed in identifiers with uppercase and lowercase equivalence 16 273 May 2002 Chapter 2 The GNAT Compilation Model IBM PC code page 850 This code page is a modification of 437 extended to include all the Latin 1 letters but still not with the usual Latin 1 encoding In this mode all these letters are allowed in identifiers with uppercase and lowercase equivalence Full Upper 8 bit Any character in the range 80 F F allowed in identifiers and all are considered distinct In other words there are no uppercase and lowercase equivalences in this range This is useful in conjunction with certain encoding schemes used for some foreign character sets eg the typical method of representing Chinese characters on the PC NoU pper Half No upper half characters in the range 80 FF are allowed in identifiers This gives Ada 83 compatibility for identifier names For precise data on the encodings permitted and the uppercase and lowercase equivalences that are recognized see the file
62. alternative format is allowed for loops For exam ple both of the following are permitted 57 GNAT User s Guide for Unix Platforms Clear while J lt 10 loop A J 0 end loop Clear Clear while J lt 10 loop A J 0 end loop Clear m check maximum line length If the letter m appears in the string after gnaty then the length of source lines must not exceed 79 characters indud ing any trailing blanks The value of 79 allows convenient display on an 80 character wide device or window allowing for possi ble special treatment of 80 character lines Mnnn set maximum line length If the sequence Mnnn where nnn is a decimal number ap pears in the string after gnaty then the length of lines must not exceed the given value n check casing of entities in Standard If the letter n appears in the string after gnaty then any identifier from Standard must be cased to match the presen tation in the Ada Reference Manual for example Integer and ASCII NUL o check order of subprogram bodies If the letter o appears in the string after gnaty then all subprogram bodies in a given scope e g a package body must bein alphabetical order The ordering rule uses normal Ada rules for comparing strings ignoring casing of letters except that if thereis a trailing numeric suffix then the value of this suffix is used in the ordering e g J unk2 comes before J unk10 p check pragma casing If theletter p ap
63. app_main end App_Proj Building an executable is achieved through the command gnatmake P app app_proj which will generate the app_main executable in the directory where app_proj gpr resides If an imported project file uses the standard extension gpr then as illustrated above the with clause can omit the extension Our example specified an absolute path for each imported project file Alternatively you can omit the directory if either e The imported project file is in the same directory as the importing project file or e You have defined an environment variable ADA PROJECT PATH that includes the directory containing the needed project file Thus if we define ADA_PROJECT_PATH to include gui and comm then our project file app_proj gpr could be written as follows with gui_proj comm_proj project App_Proj is for Main use app_main end App_Proj Importing other projects raises the possibility of ambiguities For exam ple the same unit might be present in different imported projects or it might be present in both the importing project and an imported project Both of these conditions are errors Note that in the current version of the Project Manager it is illegal to have an ambiguous unit even if the unit is never referenced by the importing project This restriction may be relaxed in a future release 10 2 4 Extending a Project A common situation in large software systems is to have multi ple impl
64. been modified since they were last compiled or sources that depend on such modified sources sothat version skew is avoided gnatmake hello adb The result is an executable program called ne11o which can be run by entering hello assuming that the current directory is on the search path for executable programs and if all has gone well you will see Hello WORLD appear in response to this command 6 28 May 2002 O o Chapter 1 Getting Started with GNAT 1 3 Running a Program with Multiple Units Consider a slightly more complicated example that has three files a main program and the spec and body of a package package Greetings is procedure Hello procedure Goodbye end Greetings with Ada Text_I0 use Ada Text_I0 package body Greetings is procedure Hello is begin Put Line Hello WORLD end Hello procedure Goodbye is begin Put Line Goodbye WORLD end Goodbye end Greetings with Greetings procedure Gmain is begin Greetings Hello Greetings Goodbye end Gmain Following the one unit per file rule place this program in the following three separate files greetings ads spec of package Greetings greetings adb body of package Greetings gmain adb body of main program To build an executable version of this program we could
65. case insensitive literals True or False If the value is true then the corresponding lines are included and if the value is false they are excluded The test expression symbol Defined is true only if the symbol has been defined in the definition file or by a D switch on the command line Otherwise the test is false The equality tests are case insensitive as are all the preprocessor lines If the symbol referenced is not defined in the symbol definitions file then the effect depends on whether or not switch u is specified If so then the symbol is treated as if it had the valuefalse and thetest fails If this switch is not specified then it is an error to reference an undefined symbol It is also an error to reference a symbol that is defined with a value other than True Or False 227 GNAT User s Guide for Unix Platforms The use of the not operator inverts the sense of this logical test so that the lines are included only if the symbol is not defined The then keyword is optional as shown The must be the first non blank character on a line but otherwise the format is free form Spaces or tabs may appear between the and the keyword The keywords and the symbols are case insensitive as in normal Ada code Comments may be used on a preprocessor line but other than that no other tokens may appear on a preprocessor line Any number of e1sif clauses can be present including none at all The else is optional
66. command is simply run which causes the program to run exactly as if the debugger were not present The following section describes some of the additional commands that can be given to cps 2 74 T ML 28 May 2002 Chapter 23 Running and Debugging Ada Programs 23 3 Introduction to GDB Commands GDB contains a large repertoire of commands The manual Debugging with GDB includes extensive documentation on the use of these com mands together with examples of their use Furthermore the command help invoked from within cps activates a simple help facility which sum marizes the available commands and their options In this section we summarize a few of the most commonly used commands to give an idea of what apa is about You should create a simple program with debug ging information and experiment with the use of these epg commands on the program as you read through the following section Set args arguments The arguments list above is a list of arguments to be passed tothe program on a subsequent run command just as though the arguments had been entered on a normal invocation of the program The set args command is not needed if the program does not require arguments run The run command causes execution of the program to start from the beginning If the program is already running that is to say if you are currently positioned at a breakpoint then a prompt
67. commands that GDB provides Important additional capabilities including conditional breakpoints the ability to execute command sequences on a breakpoint the ability to debug at the machine instruction level and many other features are described in detail in Debugging with GDB Note that most commands trace 276 can be abbreviated for example c for continue bt for back 23 May 2002 Chapter 23 Running and Debugging Ada Programs 23 4 Using Ada E xpressions GDB supports a fairly large subset of Ada expression syntax with some extensions The philosophy behind the design of this subset is e That cpp should provide basic literals and access to operations for arithmetic dereferencing field selection indexing and subprogram calls leaving more sophisti cated computations to subprograms writ ten into the program which therefore may be called from GDB e That type safety and strict adherence to Ada language restrictions are not particularly important to the GDB User e That brevity is important to the GDB user Thus for brevity the debugger acts as if there were implicit with and use clauses in effect for all user written packages thus making it unnecessary to fully qualify most names with their packages regardless of context Where this causes ambiguity GDB asks the user s intent For details on the supported Ada syntax see Debugging with GDB 23 5 Calling User Defined Subprograms An important capabilit
68. depends on the setting of other options For example gnatvif or gnatVfi the order does not matter specifies that floating point parameters of mode in should be validity checked e gnatVa All validity checks All the above validity checks are turned on That is gnatva is equivalent to gnatVcdfimorst e gnatVn No validity checks This switch turns off all validity checking induding the default checking for case statements and left hand side subscripts The gnatv switch may be followed by a string of letters to turn on a series of validity checking options For example gnatvcr specifies that 53 GNAT User s Guide for Unix Platforms in addition to the default validity checking copies and function return expressions be validity checked In order to make it easier to specify a set of options the upper case letters corI1MorRsT may be used to turn off the corresponding lower case option so for example gnatvam turns on all validity checking options except for checking of in out procedure arguments The specification of additional validity checking generates extra code and in the case of gnatva the code expansion can be substantial How ever these additional checks can be very useful in smoking out cases of uninitialized variables incorrect use of unchecked conversion and other errors leading to invalid values The use of pragma Initialize_ Scalars is useful in conjunction with the extra validity checking since this ensures that
69. each step of the build process Thelist of dependencies are handled automatically by gnatmake The Makefile is simply used to call gnatmake in each of the appropriate directories Note that you should also read the example on how to automatically create the list of directories see Section 17 2 Automatically Creating a List of Directories page 243 which might help you in case your project has a lot of subdirectories 7 This Makefile is intended to be used with the following directory 4 configuration The sources are split into a series of csc computer software components Each of these csc is put in its own directory Their name are referenced by the directory names They will be compiled into shared library although this would also work with static libraries The main program and possibly other packages that do not belong to any csc is put in the top level directory where the Makefile is toplevel_dir _ first_csc sources _ lib will contain the library X second_csc sources lib will contain the library HH Vote 241 GNAT User s Guide for Unix Platforms 7 Although this Makefile is build for shared library it is easy to modify to build partial link objects instead modify the lines with shared and gnatlink below 7 With this makefile you can change any file in the system or add any new file and everything will be recompiled correctly only the relevant shared
70. end P1 procedure P2 is begin Pi end P2 begin P2 end STB 292 28 May 2002 Chapter 24 Inline Assembler 24 Inline Assembler If you need to write low level software that interacts directly with the hardware Ada provides two ways to incorporate assembly language code into your program First you can import and invoke external routines written in assembly language an Ada feature fully supported by GNAT However for small sections of code it may be simpler or more efficient to include assembly language statements directly in your Ada source program using the facilities of the implementation defined pack age System Machine_ Code Which incorporates the gcc nline Assembler ThelnlineAssembler approach offers a number of advantages including the following e Noneed to use non Ada tools e Consistent interface over different targets e Automatic usage of the proper calling conventions e Access to Ada constants and variables e Definition of intrinsic routines e Possibility of inlining a subprogram comprising assembler code e Code optimizer can take Inline Assembler code into account This chapter presents a series of examples to show you how to use the Inline Assembler Although it focuses on the Intel x86 the general approach applies also to other processors It is assumed that you are familiar with Ada and with assembly langua
71. few examples abcde fghi will match any of thetwostrings abcde and fghi abc d will match any string like abd abcd abccd abcccd and so on a z will match any string which has only lowercase characters in it and at least one character 12 5 Examples of gnatxref Usage 12 5 1 General Usage For the following examples we will consider the following units 216 23 May 2002 Chapter 12 The Cross Referencing Tools gnatxref and gnat find main ads with Bar package Main is procedure Foo in Integer C Integer private D Integer end Main main adb 1 package body Main i procedure Foo in Integer is begin C B D B Bar Print Bar Print end Foo end Main bar ads 1 package Bar is 2 procedure Print B Integer 3 end bar The first thing to do is to recompile your application for instance in that case just by doing a gnatmake main SO that GNAT generates the cross referencing information You can then issue any of the following commands gnatxref main adb gnatxref generates cross reference information for main adb and every unit with ed by main adb The output would be B Type Integer Decl bar ads 2 22 B Type Integer Decl main ads 3 20 Body main adb 2 20 217 GNAT User s Guide for Unix Platforms Ref main adb 4 13 5 13 6 19 Bar Type Unit Decl bar ads 1 9 Ref main adb 6 8 7 8 main ads 1
72. find all other source files that are needed the most common beingthe specs of units the compiler examines thefollowing directories in the following order 71 GNAT User s Guide for Unix Platforms 1 Thedirectory containing the source file of the main unit being com piled the file name on the command line 2 Each directory named by an 1 switch given on the gcc command line in the order given 3 Each of the directories listed in the value of the ADA INCLUDE PATH environment variable Construct this value exactly as the PATH environment variable a list of directory names separated by colons semicolons when working with the NT version 4 Thecontent of the ada_source_path file which is part of the GNAT installation tree and is used to store standard libraries such as the GNAT Run TimeLibrary RTL source files Section 16 2 Installing an Ada Library page 234 Specifying the switch 1 inhibits the use of the directory containing the source file named in the command line You can still have this directory on your search path but in this case it must be explicitly requested with a I switch Specifying the switch nostdinc inhibits the search of the default location for the GNAT Run Time Library RTL source files Thecompiler outputs its object files and ALI files in the current work ing directory Caution The object file can be redirected with the o switch however gcc and gnat1 have not been coordinated on thi
73. first for example movw 4 eax Intel Destination first for example mov eax 4 24 2 A Simple Example of Inline Assembler The following example will generate a single assembly language state ment nop Which does nothing Despite its lack of run time effect the example will be useful in illustrating the basics of the Inline Assembler facility with System Machine_Code use System Machine_Code procedure Nothing is begin Asm nop end Nothing Asm S a procedure declared in package system Machine Code here it takes one parameter a template string that must be a static expression and that will form the generated instruction Asm may be regarded as a compile time procedure that parses the template string and additional parameters none here from which it generates a sequence of assembly language instructions The examples in this chapter will illustrate several of the forms for invoking Asm a complete specification of the syntax is found in the GNAT Reference Manual 294 883 May 2002 Chapter 24 Inline Assembler Under the standard GNAT conventions the Nothing procedure should bein a file named nothing adb You can build the executable in the usual way gnatmake nothing H owever the interesting aspect of this example is not its run time behavior but rather the generated assembly code To see this output invoke the compiler as follows gcc c S fomit frame pointer gnatp nothing adb where the opti
74. have to force the expansion of o since in some cases make won t be able to do it itself aa lib libaa so wildcard aa o bb lib libbb so wildcard bb o cc lib libcc so wildcard cc o Make sure all of the shared libraries are in the path before starting the program run LD_LIBRARY_PAT H pwd aa lib pwd bb lib pwd cc lib MAIN clean RM rf CSC_LIST lib RM CSC_LIST ali RM CSC_LIST o RM o ali MAIN 17 2 Automatically Creating a List of Directories In most makefiles you will have to specify a list of directories and store it in a variable For small projects it is often easier to specify each of them by hand since you then have full control over what is the proper order for these directories which ones should be induded However in larger projects which might involve hundreds of subdi rectories it might be more convenient to generate this list automatically The example below presents two methods The first one although less general gives you more control over the list It involves wildcard characters that are automatically expanded by make Its shortcoming is that you need to explicitly specify some of the organization of your project such as for instance the directory tree depth whether some directories are found in a separate tree The second method is the most general one It requires an external program called find which is standard on a
75. if check status word value check if we can get the control word Asm the assembler code 23 May 2002 Chapter 24 Inline Assembler fnstcw 40 save the control word output into Register register must be a memory location Outputs gt Unsigned_16 Asm_output m Register check the relevant bits if Register and 16 103F 16 003F then return False no control word end if check control word value FPU found return True end Has_FPU The processor supports the CPUID instruction if it is possible to change the value of ID flag bit in the EFLAGS register function Has_CPUID return Boolean is Original_Flags Modified_Flags Processor_Register EFLAG contents before and after changing the ID flag begin try flipping the ID flag in the EFLAGS register Asm the assembler code pushfl amp LF amp HT amp push EFLAGS on stack pop AAeax amp LF amp HT amp pop EFLAGS into eax movl AAeax 0 amp LF amp HT amp save EFLAGS content xor 0x200000 4A4eax amp LF amp HT amp flip ID flag push eax amp LF amp HT amp push EFLAGS on stack popfl amp LF amp HT amp load EFLAGS register pushfl amp LF amp HT amp push EFLAGS on stack pop 41 save EFLAGS content 321 GNAT User s Guide for Unix Platforms 322 output values may be anything Original Flags is 0 Modified Flags is 1 Outputs
76. is green The color argument can be any name accepted by html d If the ada files depend on some other files using for instance the with command the latter will also be converted to html Only the files in the user project will be converted to html not the files in the run time library itself D This command is the same as d above but gnathtm will also look for files in the run time library and generate html files for them f By default gnathtml will generate html links only for global entities with ed units global variables and types If you specify the f on the command line then links will be gener ated for local entities too l number If this switch is provided and number is not 0 then gnathtm1 will number the html files every number line Idir Specify a directory to search for library files a1i files and source files You can provide several I switches on the command line and the directories will be parsed in the order of the command line 270 28 May 2002 o dir p file sc color t file Chapter 22 Other Utility Programs Specify the output directory for html files By default gnathtml will saved the generated html files in a subdirec tory named htm1 If you are using Emacs and the most recent Emacs Ada mode which provides a full Integrated Development E
77. is to list this expanded code in a form very dose to normal 67 GNAT User s Guide for Unix Platforms 68 Ada source Thisis very useful in understanding theimplica tions of various Ada usage on the efficiency of the generated code There are many cases in Ada e g the use of con trolled types where simple Ada statements can generate a lot of run time code By using gnatG you can identify these cases and consider whether it may be desirable to modify the coding approach to improve efficiency The format of the output is very similar to standard Ada source and is easily understood by an Ada programmer The following special syntactic additions correspond to low level features used in the generated code that do not have any exact analogies in pure Ada source form The following is a partial list of these special constructions See the specifica tion of package sprint in file sprint ads for a full list new xxx storage_pool yyy Shows the storage pool being used for an alloca tor at end procedure name Shows the finalization cleanup procedure for a scope if expr then expr else expr Conditional expression equivalent to the x y z construction in C target source A conversion with floating point truncation in stead of rounding target source A conversion that bypasses normal Ada semantic checking In particular enumeration types and fixed point types are treated simply as integers target s
78. least one year after the last time you distribute an Opaque copy directly or through your agents or retailers of that edition to the public 335 GNAT User s Guide for Unix Platforms It is requested but not required that you contact the authors of the Document well before redistributing any large number of copies to give them a chance to provide you with an updated version of the Document 4 MODIFICATIONS You may copy and distribute a Modified Version of the Document under the conditions of sections 2 and 3 above provided that you release the Modified Version under precisely this License with the Modified Version filling the role of the Document thus licensing distribution and modification of the Modified Version to whoever possesses a copy of it In addition you must do these things in the Modified Version A Usein the Title Page and on the covers if any a title distinct from that of the Document and from those of previous versions which should if there were any be listed in the History section of the Document You may use the same title as a previous version if the original publisher of that version gives permission B List on the Title Page as authors one or more persons or enti ties responsible for authorship of the modifications in the Modified Version together with at least five of the principal authors of the Document all of its principal authors if it has less than five C State on the Title page the
79. n processes to carry out the re compilations On a mul tiprocessor machine compilations will occur in parallel In the event of compilation errors messages from various com pilations might get interspersed but gnatmake will give you the full ordered list of failing compiles at the end If this is problematic rerun the make process with n set to 1 to get a clean list of messages Keep going Continue as much as possible after a compilation error To ease the programmer s task in case of compilation errors the list of sources for which the compile fails is given when gnatmake terminates If gnatmake is invoked with several file names and with this switch if there are compilation errors when building an executable gnatmake will not attempt to build the following executables Link only Can be combined with b to binding and linking Linking will not be performed if combined with c but not with b When not combined with b all the units in the closure of the main program must have been previously com piled and must be up to date and the main program need to have been bound The root unit specified by file name may be given without extension with the source extension or if noGNAT Project Fileis specified with the ALI file extension Specifies that the minimum necessary amount of recompi lations be performed In this mode gnatmake ignores time 23 May 2002 Chapter 6 The GNAT Make Program gnatmake stamp differences wh
80. named my1ibinit in the previous example are called before the library services are used Any number of libraries can be used simultaneously as long as the elaboration proce dure of each library is called Below is an example of C program that uses our my1ib library include mylib interface h int main void 237 GNAT User s Guide for Unix Platforms First elaborate the library before using it mylibinit Main program using the library exported entities do_something do_something_else Library finalization at the end of the program mylibfinal return 0 Note that this same library can be used from an equivalent Ada main program In addition if the libraries are installed as detailed in Sec tion 16 2 Installing an Ada Library page 234 it is not necessary to invoke the library elaboration and finalization routines The binder will ensure that this is done as part of the main program elaboration and finalization phases 16 4 3 The Finalization Phase Invoking any library finalization procedure generated by gnatbind shuts down the Ada run time permanently Consequently the finalization of all Ada libraries must be performed at the end of the program Nocall to these libraries nor the Ada run time should be made past the finalization phase 16 4 4 Restrictions in Libraries The pragmas listed below should be used with caution inside libraries as they can create incompa
81. of incorrect memory references Chapter 20 Creating Sample Bodies Using gnatstub page 259 discusses gnatstub a utility that generates empty but compilable bodies for library units Chapter 21 Reducing the Size of Ada Executables with gnatelim page 261 describes gnatelim a tool which detects unused subpro grams and helps the compiler to create a smaller executable for the program Chapter 22 Other Utility Programs page 267 discusses several other GNAT utilities including gnatpsta Chapter 23 Running and Debugging Ada Programs page 273 de scribes how to run and debug Ada programs Chapter 24 Inline Assembler page 293 shows how tousetheinline assembly facility in an Ada program 23 May 2002 A Out This Guide e Chapter 25 Performance Considerations page 327 reviews the trade offs between using defaults or options in program develop ment What You Should Know before Reading This Guide This user s guide assumes that you are familiar with Ada 95 language as described in the International Standard ANSI ISO I E C 8652 1995 Jan 1995 Related Information For further information about related tools refer to the following docu ments e GNAT Reference Manual which contains all reference material for the GNAT implementation of Ada 95 e Ada 95 Language Reference Manual which contains all reference material for the Ada 95 programming language e Debugging with GDB contains all details
82. of non freed allocations Final Water Mark non freed mem High Water Mark Backtrace test_gm adb 11 test_gm my_alloc test_gm adb 21 test_gm b_test_gm c 52 main Allocation Root 4 Number of non freed allocations Final Water Mark non freed mem High Water Mark Backtrace 1 3 91 Kilobytes 3 91 Kilobytes 1 12 Bytes 12 Bytes s secsta adb 181 system secondary_stack ss_init s secsta adb 283 lt system__secondary_stack___elabb gt b_test_gm c 33 adainit The allocation root 1 of the first example has been split in 2 roots 1 and 8 thanks to the more precise associated backtrace 23 May 2002 Chapter 18 Finding Memory Problems with gnatmem 18 5 GDB and GMEM Modes The main advantage of the GMEM mode is that it is a lot faster than the GDB mode where the application must be monitored by a cps script But the avEM mode is available only for DEC Unix Linux x86 Solaris sparc and x86 and Windows 95 98 NT 2000 x86 The main advantage of the cpp mode is that it is available on all sup ported platforms But it can be very slow if the application does a lot of allocations and deallocations 18 6 Implementation Note 18 6 1 gnatmem Using cpB Mode gnatmem executes the user program under the control of GDB using a script that sets breakpoints and gathers information on each dynamic allocation and deallocation The output of the script is then analyzed by gnatmem in order tolocate memory leaks andtheir origin in the progra
83. of the Gnatelim Options unit in the compiler source file gnatelim options adb 263 GNAT User s Guide for Unix Platforms gnatelim Sends its output to the standard output stream and all the tracing and debug information is sent to the standard error stream In order to produce a proper GNAT configuration file gnat adc redirection must be used gnatelim Main_Prog gt gnat adc or gnatelim Main_Prog gt gt gnat adc In order to append the gnatelim output to the existing contents of gnat adc 21 6 Correcting the List of Eliminate Pragmas In some rare cases it may happen that gnatelim will try to eliminate subprograms which are actually called in the program In this case the compiler will generate an error message of the form file adb 106 07 cannot call eliminated subprogram My Prog You will need to manually remove the wrong Eliminate pragmas from the gnat adc file It is advised that you recompile your program from scratch after that because you need a consistent gnat adc file during the entire compilation 21 7 Making Your Executables Smaller In order to get a smaller executable for your program you now have to recompile the program completely with the new gnat adc file created by gnatelim in your current directory gnatmake f Main_Prog you will need f option for gnatmake to recompile everything with the set of pragmas Eliminate you have obtained with gnatelim Be aware that th
84. out of date with respect tothesource file Note that this is the mode that is automatically used by gnatmake because in this case the checking against sources has already been performed by gnatmake in the course of compilation i e before binding 4 4 Binder Error Message Control The following switches provide control over the generation of error mes sages from the binder V mn Mxxx 102 Verbose mode In the normal mode brief error messages are generated to stderr If this switch is present a header is written to stdout and any error messages are directed to stdout All that is written to stderr is a brief summary message Generate brief error messages to staerr even if verbose mode is specified This is relevant only when used with the v Switch Limits the number of error messages to n a decimal integer in the range 1 999 The binder terminates immediately if this limit is reached Renamesthe generated main program from maintoxxx This is useful in the case of some cross building environments where the actual main program is separate from the one generated by gnatbind 23 May 2002 WS We Chapter 4 Binding Using gnatbind Suppress all warning messages Treat any warning messages as fatal errors The binder performs a number of consistency checks indud ing e Check that time stamps of a given source unit are con sistent e Check that checksums of a given source unit are consis ten
85. pinpoint the construct in your program that is the likely source of the problem Thefollowing strategies are presented in increasing order of difficulty corresponding to your experience in using GNAT and your familiarity with compiler internals 1 Run gcc with the gnatf This first switch causes all errors on a given lineto be reported In its absence only the first error on a line is displayed The gnatdo switch causes errors to be displayed as soon as they are encountered rather than after compilation is terminated If GNAT terminates prematurely or goes into an infinite loop the last error message displayed may help to pinpoint the culprit 2 Run acc with the v verbose switch In this mode scc produces ongoing information about the progress of the compilation and pro vides the name of each procedure as code is generated This switch allows you to find which Ada procedure was being compiled when it encountered a code generation problem 3 Run gcc with the gnatdc switch This is a GNAT specific switch that does for the front end what v does for the back end The system prints the name of each unit either a compilation unit or nested unit as it is being analyzed 4 Finally you can start gdb directly on the gnat1 executable gnati is the front end of GNAT and can be run independently normally it is just called from acc You can use gdb on gnat1 as you would on a C program but see Section 23 1 The GNAT Debugger GDB p
86. pragma Export C u00010 gnat__heap_sort_aB pragma Export C u00011 gnat__heap_sort_aS pragma Export C u00012 systemS pragma Export C u00013 system exception tableB pragma Export C u00014 system__exception_tableS pragma Export C u00015 gnat__htableB pragma Export C u00016 gnat__htableS pragma Export C u00017 system__exceptionsS pragma Export C u00018 system__machine_state_operationsB pragma Export C u00019 system__machine_state_operationsS pragma Export C u00020 system__machine_codeS pragma Export C u00021 system__storage_elementsB pragma Export C u00022 system__storage_elementsS pragma Export C u00023 system secondary stackB pragma Export C u00024 system secondary stackS pragma Export C u00025 system parametersB pragma Export C u00026 system parameters S pragma Export C u00027 system soft linksB pragma Export C u00028 system soft linksS pragma Export C u00029 system stack checkingB pragma Export C u00030 system stack checkingS pragma Export C u00031 system tracebackB pragma Export C u00032 system tracebackS pragma Export C u00033 ada__streamsS pragma Export C u00034 ada__tagsB pragma Export C u00035 ada tagsS pragma Export C u00036 system string opsB pragma Export C u00037 system string opsS pragma Export C u00038 interfacesS
87. program Now save the file choose the File menu item and then the save buffer Selection You will see a message at the bottom of the buffer confirming that the file has been saved You are now ready to attempt to build the program Select the ada item from the top menu bar Although we could choose simply to compile the file we will instead attempt to do a build which invokes gnatmake since if the compile is successful we want to build an executable Thus select Ada build This will fail because of the compilation error and you will notice that the Glide window has been split the top window contains the source file and the bottom window contains the output from the GNAT tools Glide allows you to navigate from a compilation error to the source file position corresponding to the error dick the middle mouse button or simultaneously press the left and right buttons on a two button mouse on the diagnostic line in the tool window The focus will shift to the source window and the cursor will be positioned on the character at which the error was detected Correct the error type in a semicolon to terminate the statement Although you can again savethefile explicitly you can also simply invoke Ada gt Build and you will be prompted to save the file This time the build will succeed the tool output window shows you the options that are supplied by default The GNAT tools output e g object and ALI files executable will go in the dire
88. program which depends upon all the packages that comprise the interface of the library This dummy main program can then be given to gnatmake in order to build all the necessary objects Here is an example of such a dummy program and the generic commands used to build an archive or a shared library with My_Lib Service1 with My_Lib Service2 with My_Lib Service3 233 GNAT User s Guide for Unix Platforms procedure My_Lib_Dummy is begin null end compiling the library gnatmake c my_lib_dummy adb we don t need the dummy object itself rm my_lib_dummy o my_lib_dummy ali create an archive with the remaining objects ar rc libmy_lib a o some systems may require ranlib to be run as well or create a shared library gcc shared o libmy_lib so o some systems may require the code to have been compiled with fPIC When the objects are grouped in an archive or a shared library the user needs to specify the desired library at link time unless a pragma linker_options has been used in one of the sources pragma Linker_Options lmy_lib 16 2 Installing an Ada Library In the GNAT model installing a library consists in copying into a specific location the files that make up this library It is possible to install the sources in a different directory from the other files ALI objects archives since the source path and the object path can easily be specified separately For general purpose libra
89. s aunit that does not meet one of the above four criteria then the binder gnatbind will issue a warning similar to that in the following example warning x ads has dynamic elaboration checks and with s warning y ads which has static elaboration checks These warnings indicate that the rule has been violated and that as a result elaboration checks may be missed in the resulting executable file This warning may be suppressed using the ws binder switch in the usual manner Oneuseful application of this mixing ruleisin the case of a subsystem which does not itself with units from the remainder of the application In this case the entire subsystem can be compiled with dynamic checks 199 GNAT User s Guide for Unix Platforms to resolve a circularity in the subsystem while allowing the main appli cation that uses this subsystem to be compiled using the more reliable default static model 11 9 What to Do If the Default Elaboration Behavior Fails If the binder cannot find an acceptable order it outputs detailed diag nostics For example error elaboration circularity detected info proc body must be elaborated before pack body info reason Elaborate_All probably needed in unit pack body info recompile pack body with gnatwl info for full details info proc body info is needed by its spec info proc spec info which is withed by info pack body info pack body must be
90. same that you generally used in a Unix shell command line or in a DOS session Here is a more formal grammar term elmt matches elmt elmt elmt concatenation elmt then elmt any string of O or more characters lt matches any character char char matches any character listed char char matches any character in range full regular expression regexp term item item item item Thesecond set of regular expressions is much more powerful This is the type of regular expressions recognized by utilities such a grep The following is the form of a regular expression expressed in Ada reference manual style BNF is as follows term term alternation term or term item item concatenation item then item elmt match elmt elmt zero or more elmt s elmt one or more elmt s elmt matches elmt or nothing 215 GNAT User s Guide for Unix Platforms elmt elmt elmt elmt elmt elmt elmt char nschar nschar matches given character nschar nschar matches any character listed nschar nschar matches any character not listed char char matches chars in given range char matches given character matches any single character regexp parens used for grouping any character including special characters any character except Following are a
91. source files in the system default directory 23 May 2002 Chapter 6 The GNAT Make Program gnatmake nostdlib Do not look for library files in the system default directory RTS rts path Specifies the default location of the runtime library We look for the runtime in the following directories and stop as soon as a valid runtime is found adainclude or ada source path and adalib or ada_object_path present e current directory rts path e lt default search dir gt rts_path e default search dir rts rts path The selected path is handled like a normal RTS path 6 3 Mode Switches for gnatmake The mode switches referred to as mode switches allow the inclusion of switches that are to be passed to the compiler itself the binder or the linker The effect of a mode switch is to cause all subsequent switches up to the end of the switch list or up to the next mode switch to be interpreted as switches to be passed on to the designated component of GNAT cargs switches Compiler switches Here switches is a list of switches that are valid switches for gcc They will be passed on to all compile steps performed by gnatmake bargs switches Binder switches Here switches isa list of switches that are valid switches for gcc They will be passed on to all bind steps performed by gnatmake largs switches Linker switches Here switches is a list of switches that are valid switches for gcc They will be passed on to
92. space between p and proj proj may include directory information proj must be writeable There may be only one switch p When a switch P is specified no switch c may be specified 23 May 2002 Chapter 9 HandlingArbitrary FileNaming Conventions Usinggnatname v Verbose mode Output detailed explanation of behavior to stdout This includes name of the file written the name of the directories to search and for each filein those directories whose name matches at least one of the Naming Patterns an indication of whether the file contains a unit and if so the name of the unit v v Very Verbose mode In addition to the output produced in verbose mode for each file in the searched directories whose name matches none of the Naming Patterns an indication is given that there is no match 9 4 Examples of gnatname Usage gnatname equivalent to gnatname d x gnatname c home me names adc d sources a z ada In this example the directory home me must already exist and be writeable In addition the directory home me sources specified by d sources must exist and be readable Note the optional spaces after c and d gnatname P home me proj dsources dsources plus Dcommon dirs txt body spec x Note that several switches a may be used even in conjunction with one or several switches D Several Naming Patterns are used in this example 135 GNAT User s Guide for Unix Platfo
93. stack frames Natural Len will receive the actual number of stack frames returned begin Call_Chain TB Len Text IO Put In STB P1 for K in 1 Len loop Text IO0 Put Debug Utilities Image TB K Text I0 Put C 7 end loop Text IO New Line end P1 procedure P2 is begin P1 end P2 begin P2 end STB gnatmake stb stb In STB P1 1640040 F1E4 4 1640040 14F21 1630040 170B8 1640040 171Cit M o 289 GNAT User s Guide for Unix Platforms 16 0040_1461 16 0040_11C4 16 0040_11F1 16 77E8_92A4 23 13 2 Symbolic Traceback A symbolic traceback is a stack traceback in which procedure names are associated with each code location Note that this feature is not supported on all platforms See GNAT Traceback Symbolic spec in g trasym ads for a complete list of currently supported platforms Note that the symbolictraceback requires that the program be compiled with debug information If it is not compiled with debug information only the non symbolic information will be valid 23 13 2 1 Tracebacks From Exception Occurrences 290 r r ur r urr 28 May 2002 Chapter 23 Running and Debugging Ada Programs with Ada Text_I0 with GNAT Traceback Symbolic procedure STB is procedure P1 is begin raise Constraint_Error end P1 procedure P2 is begin P1 end P2 procedure P3 is begin P2 end P3 begin P3 exception when E others gt Ada Text_I
94. system is ported from a foreign compilation environment to GNAT with file names that do not usethe default GNAT conventions Instead of changing all the file names which for a variety of reasons might not be possible you can define the relevant file naming scheme in the Naming package in your project file For example the following package models the Apex file naming rules package Naming is for Casing use lowercase for Dot Replacement use for Specification Suffix Ada use 1 ada for Implementation Suffix Ada use 2 ada end Naming You can define the following attributes in package Naming Casing This must be a string with one of the three values lowercase uppercase Of mixedcase these strings are case insensitive If Casing is not specified then the default is lowercase Dot Replacement This must be a string whose value satisfies the following conditions e t must not be empty e t cannot start or end with an alphanumeric character e t cannot bea single underscore e t cannot start with an underscore followed by an al phanumeric e It cannot contain a dot except if it the entire string IS N If Dot Replacement is not specified then the default is 162 28 May 2002 Chapter 10 GNAT Project Manager Specification Suffix This is an associative array indexed by the p
95. tags E ada__tags if ada__streams_E 0 ada__streams___elabs ada streams E t gt if system__finalization_root_E 0 system__finalization_root___elabs system__finalization_root_E 1 if ada exceptions E 0 elabb ada exceptions Et ada exceptions gt if system finalization implementation E 0 system finalization implementation gt if system finalization implementation E 0 system finalization implementation system finalization implementation Et gt if ada__finalization_E 0 ada__finalization___elabs 97 GNAT User s Guide for Unix Platforms gt ada__finalization_E 1 if ada__finalization__list_controller_E 0 ada__finalization__list_controller___elabs ada__finalization__list_controller_E 1 if system__file_control_block_E 0 i system__file_control_block___elabs system__file_control_block_E if system file io E 0 system file io elabb system file io E gt if ada__text_io_E 0 ada__text_io___elabs if ada__text_io_E 0 ada__text_io___elabb ada__text_io_E gnat inside elab final code 0 int main argc argv envp gt int argc char argv char envp gnat_argc argc gnat_argv argv gnat_envp envp _ gnat_initialize adainit __gnat_break_start ada hello system standard library adafinal
96. task type and the elaboration of the task itself i e the creation of the task happen at the same ti me A good rule of style in Ada 95 is to always create explicit task types By followingthe additional step of placing task objects in separate packages from the task type dec laration many elaboration problems are avoided Here is another modified example of the example program package Decls is task type Lib Task Type is entry Start 196 28 May 2002 Chapter 11 Elaboration Order Handling in GNAT end Lib_Task_Type type My_Int is new Integer function Ident M My Int return My Int end Decls with Utils package body Decls is task body Lib_Task_Type is begin accept Start Utils Put_Val 2 end Lib_Task_Type function Ident M My_Int return My_Int is begin return M end Ident end Decls with Decls package Utils is procedure Put_Val Arg Decls My_Int end Utils with Text I0 package body Utils is procedure Put Val Arg Decls My Int is begin Text I0 Put Line Decls My_Int Image Decls Ident Arg end Put Val end Utils with Decls package Declst is Lib_Task Decls Lib_Task_Type end Declst with Declst procedure Main is begin Declst Lib_Task Start 197 GNAT User s Guide for Unix Platforms end What wehavedonehereistoreplacethe task declaration in package Decls Wit
97. the imported project can be used by the immediate sources of the importing project and recursively Thus if A imports B and 8 imports c the immediate sources of A may depend on the immediate sources of c even if A does not import c explicitly However this is not recommended because if and when B ceases to import c some sources in a will nolonger compile A side effect of this capability is that cyclic dependences are not per mitted if A imports B directly or indirectly then B is not allowed to import a 158 28 May 2002 Chapter 10 GNAT Project Manager 10 6 Project E xtension During development of a large system it is sometimes necessary to use modified versions of some of the source files without changing the original sources This can be achieved through a facility known as project extension project Modified_Utilities extends baseline utilities gpr is The project file for the project being extended the parent is identified by the literal string that follows the reserved word extends which itself follows the name of the extending project the child By default a child project inherits all the sources of its parent H ow ever inherited sources can be overridden a unit with the same name as one in the parent will hide the original unit Inherited sources are consi dered to be sources but not immediate sources
98. the program using the gcc command You must compile the following files e the body file adb for a library level subprogram or generic sub program e the spec file aas for a library level package or generic package that has no body e the body file aab for a library level package or generic package that has a body You need not compile the following files e the spec of alibrary unit which has a body e subunits because they are compiled as part of compiling related units GNAT package specs when the corresponding body is compiled and subunits when the parent is compiled If you attempt to compile any of these files you will get one of the following error messages where fff is the name of the file you compiled No code generated for file fff package spec No code generated for file fff subunit The basic command for compiling a file containing an Ada unit is gcc c switches file name wherefile nameisthenameof theAda file usually havingan extension ads for a spec or adb for a body You specify the c switch to tell gcc to compile but not link the file The result of a successful compilation is an object file which has the same name as the source file but an extension of o and an Ada Library Information ALI file which also has the same name as the source file but with a1i asthe extension GNAT creates these two output files in the current directory but you may specify a sourc
99. the unit being com piled depends either directly or indirectly pass exit codes If this switch is not used the exit code returned by gcc when compiling multiple files indicates whether all source files have been successfully used to generate object files or not When pass exit codes iS used gcc exits with an extended exit status and allows an integrated development environ ment to better react to a compilation failure Those exit status are 5 There was an error in at least one source file 3 At least one source file did not generate an object file 2 The compiler died unexpectedly internal error for example 0 An object file has been generated for every source file 3 2 15 Debugging Control gnatdx gnatG Activate internal debugging switches x is a letter or digit or string of letters or digits which specifies the type of de bugging outputs desired Normally these are used only for internal development or system debugging purposes You can find full documentation for these switches in the body of the Debug unit in the compiler source file debug adb This switch causes the compiler to generate auxiliary output containing a pseudo source listing of the generated expanded code Like most Ada compilers GNAT works by first trans forming the high level Ada code into lower level constructs For example tasking operations aretransformed into callsto the tasking run time routines A unique capability of GNAT
100. then Ada Text_I0 Put_Line DE end if Page Size Extension if Features PSE True then Ada Text_I0 Put_Line PSE end if Time Stamp Counter if Features TSC True then Ada Text IO Put Line TSC end if Model Specific Registers if Features MSR True then Ada Text IO Put Line MSR end if Physical Address Extension if Features PAE True then Ada Text IO Put Line PAE end if Machine Check Extension if Features MCE True then Ada Text IO Put Line MCE end if CMPXCHG8 instruction supported if Features CX8 True then Ada Text IO Put Line CX8 end if on chip APIC hardware support if Features APIC True then Ada Text IO Put Line APIC end if Fast System Call if Features SEP True then Ada Text IO Put Line SEP Debugging Extension Page Size Extension Time Stamp Counter Model Specific Registers Physical Address Extension Machine Check Extension CMPXCHG8 instruction on chip APIC hardware support Fast System Call 23 May 2002 end if Memory Type Range Registers if Features MTRR True then Ada Text_I0 Put_Line MTTR end if Page Global Enable if Features PGE True then Ada Text_I0 Put_Line PGE end if Machine Check Architecture if Features MCA True then Ada Text_I0 Put_Line MCA end if Chapter 24 Inline Assembler Memory Type Range Registers Page Global Enab
101. use g 01 f end Builder package Compiler is for Switches main adb use 02 end Compiler end Proj2 If you issue the command gnatmake PProj2 00 main then the compiler will be invoked on main adb with the following se quence of switches g 01 02 00 with the last o switch having precedence over the earlier ones several other switches such as c are added implicitly The switches g and o1 are contributed by package Builder 02 is contributed by the package compiler and oo comes from the com mand line The g switch will also be passed in the invocation of gnatlink A final example illustrates switch contributions from packages in different project files project Proj3 is for Source Files use pack ads pack adb package Compiler is for Default Switches Ada use gnata end Compiler end Proj3 with Proj3 project Proj4 is for Source Files use foo main adb bar main adb package Builder is for Switches foo main adb use s g end Builder end Proj4 168 28 May 2002 Chapter 10 GNAT Project Manager Ada source file with Pack procedure Foo_Main is end Foo_Main If the command is gnatmake PProj4 foo_main adb cargs gnato then the switches passed to the compiler for foo_main adb are g contributed by the
102. use four sepa rate steps to compile bind and link the program as follows gcc c gmain adb GNAT User s Guide for Unix Platforms gcc c greetings adb gnatbind gmain gnatlink gmain Note that there is no required order of compilation when using GNAT In particular it is perfectly fine to compile the main program first Also it is not necessary to compile package specs in the case where there is an accompanying body you only need to compile the body If you want to submit these files to the compiler for semantic checking and not code generation then use the gnatc Switch gcc c greetings ads gnatc Although the compilation can be done in separate steps as in the above example in practice it is almost always more convenient to use the gnatmake tool All you need to know in this case is the name of the main program s source file The effect of the above four commands can be achieved with a single one gnatmake gmain adb Inthenext section we discuss the advantages of using gnatmake in more detail 1 4 Using the gnatmake Utility If you work on a program by compiling single components at a time using gcc you typically keep track of the units you modify In order to build a consistent system you compile not only these units but also any units that depend on the units you have modified For example in the preceding case if you edit gmain adb you only need to recompile that file But if you edit greeting
103. use of Ada libraries par ticularly convenient Assume you have an Ada library organized as follows obj dir contains the objects and ALI files for of your Ada compilation units whereas include dir Contains the specs of these units but no bodies Then to compile a unit stored in main adb which uses this Ada library you would just type gnatmake alinclude dir aLobj dir main e Usinggnatmake along with the m minimal recompilation switch provides an extremely powerful tool you can freely update the com ments format of your source files without having to recompile every thing Note however that adding or deleting lines in a source files may render its debugging info obsolete If the file in question is a spec the impact is rather limited as that debugging info will only be useful during the elaboration phase of your program For bodies the impact can be more significant In all events your debugger will warn you if a source file is more recent than the corresponding object and therefore obsolescence of debugging information will go unnoticed 6 5 How gnatmake Works Generally gnatmake automatically performs all necessary recompila tions and you don t need to worry about how it works However it may be useful to have some basic understanding of the gnatmake approach and in particular to understand how it uses the results of previous com pilations without incorrectly depending on them 122
104. utility to provide an automatic way to handle configuration pragmas following the semantics for compila tions that is files with multiple units described in the RM See section see Section 7 2 Operating gnatchop in Compilation Mode page 125 for details However for most purposes it will be more convenient to edit the gnat adc file that contains configuration pragmas directly as described in the following section 8 2 The Configuration Pragmas Files In GNAT a compilation environment is defined by the current directory at the time that a compile command is given This current directory is searched for a file whose name is gnat aac If this file is present it is expected to contain one or more configuration pragmas that will be applied to the current compilation However if the switch gnata is used gnat adc is not considered Configuration pragmas may be entered into the gnat adc file either by running gnatchop on a source file that consists only of configuration pragmas or more conveniently by direct editing of the gnat adc file which is a standard format source file In addition to gnat adc one additional file containing configuration pragmas may be applied to the current compilation using the switch gnatecpath path must designate an existing file that contains only configuration pragmas These configuration pragmas are in addition to those found in gnat adc provided gnat
105. we describe the switches in more detail in functionally grouped sections b target Compile your program to run on target which is the name of a system configuration You must have a GNAT cross compiler built if target is not the same as your host system Bdir Load compiler executables for example gnat 1 the Ada com piler from dir instead of the default location Only use this switch when multiple versions of the GNAT compiler are available See the scc manual page for further details You would normally use the b or v switch instead c Compile Always use this switch when compiling Ada pro grams Note for some other languages when using scc notably in the case of C and C it is possible to use use gcc without a c switch to compile and link in one step In the case of GNAT you cannot use this approach because the binder must berun and gcc cannot be used torun the GNAT binder g Generate debugging information This information is stored in the object file and copied from there to the final executable file by the linker where it can be read by the debugger You must usethe g switch if you plan on using the debugger 38 8 May 2002 Idir sr o file Chapter 3 Compiling Using gcc Direct GNAT to search the dir directory for source files needed by the current compilation see Secti
106. will ask for confirmation that you want to abandon the current execution and restart breakpoint location The breakpoint command sets a breakpoint that is to say a point at which execution will halt and cps will await further commands location is either a line number within a file given in the format ile linenumber or it is the name of a subprogram If you request that a breakpoint beset on a sub program that is overloaded a prompt will ask you to specify on which of those subprograms you want to breakpoint You can also specify that all of them should be breakpointed If the program is run and execution encounters the breakpoint then the program stops and cpp signals that the breakpoint was encountered by printingtheline of code before which the program is halted breakpoint exception name A special form of the breakpoint command which breakpoints whenever exception name is raised If name is omitted then a breakpoint will occur when any exception is raised print expression This will print the value of the given expression Most simple Ada expression formats are properly handled by cpp so the 275 GNAT User s Guide for Unix Platforms continue step next list backtrace up down frame n expression can contain function calls variables operators and attribute references Continues execution following a breakpoint until the next breakpoint or the termination of the program Executes a single line a
107. 0 Put_Line GNAT Traceback Symbolic Symbolic_Traceback H end STB gnatmake g stb bargs E largs lgnat laddr2line lintl stb 0040149F in stb pi at stb adb 8 004014B7 in stb p2 at stb adb 13 004014CF in stb p3 at stb adb 18 004015DD in ada stb at stb adb 22 00401461 in main at b stb adb 168 004011C4 in __mingw_CRTStartup at crti c 200 004011F1 in mainCRTStartup at crti c 222 TTES92A4 in at 0 The exact sequence of linker options may vary from platform to plat form The above 1args section is for Windows platforms By contrast 291 GNAT User s Guide for Unix Platforms under Unix there is no need for the 1args section Differences across platforms are due to details of linker implementation 23 13 2 2 Tracebacks From Anywhere in a Program It is possible to get a symbolic stack traceback from anywhere in a pro gram just as for non symbolic tracebacks The first step is to obtain a non symbolic traceback and then call symbolic Traceback to compute the symbolic information Here is an example with Ada Text_I0 with GNAT Traceback with GNAT Traceback Symbolic procedure STB is use Ada use GNAT Traceback use GNAT Traceback Symbolic procedure P1 is Tracebacks_Array 1 10 We are asking for a maximum of 10 stack frames Len Natural Len will receive the actual number of stack frames returned begin Call_Chain TB Len Text I0 Put Line Symbolic Traceback TB 1 Len
108. 000000 bytes Note that with w1 option it is not possible to set the stack commit size because the coma is a separator for this option 5 4 Setting Heap Size from gnatlink It is possible to specify the program heap size from gnat link Assuming that the underlying linker is GNU Id there is two ways to do so e Using X1inker linker option gnatlink hello Xlinker heap 0x10000 0x1000 This set the heap reserve size to 0x10000 bytes and the heap commit size to 0x1000 bytes e using w1 linker option gnatlink hello Wl heap 0x1000000 This set the heap reserve size to 0x1000000 bytes Note that with w1 option it is not possible to set the heap commit size because the coma is a separator for this option 114 28 May 2002 Chapter 6 The GNAT Make Program gnatmake 6 The GNAT Make Program gnatmake A typical development cycle when working on an Ada program consists of the following steps E dit some sources to fix bugs Add enhancements Compile all sources affected Rebind and relink 5 Test The third step can be tricky because not only do the modified files have to be compiled but any files depending on these files must also be recompiled The dependency rules in Ada can be quite complex espe cially in the presence of overloading use clauses generics and inlined subprograms gnatmake automatically t
109. 1E1B6E Version_32 16 23C2E789 Version_32 16 0F1BD6A1 Version 32 16 7C25DE96 Version 32 16 39ADFFA2 Version 32 16 571DE3E7 Version_32 16 5EB646AB Version_32 16 4249379B Version 32 16 0357E00A Version 32 16 3784FB72 Version_32 16 2E723019 Version 32 16 623358EA Version 32 16 107F9465 Version 32 16 6843F68A Version 32 16 63305874 Version 32 16 31E56CE1 Version_32 16 02917970 Version 32 16 6CCBA70E Version 32 16 41CD4204 Version_32 16 572E3F58 Version_32 16 20729FF5 Version_32 16 1D4F93E8 Version 32 16 30B2EC3D Version_32 16 34054F96 Version 32 16 5A199860 Version 32 16 0E7F912B Version 32 16 5760634A Version 32 16 5D851835 Export pragmas export the version numbers names ending in B for body or S that they can be located in a link The information provided here is sufficient to track down the exact versions of units used in a given build pragma Export C u00001 helloB pragma Export C u00002 system__standard_libraryB 79 GNAT User s Guide for Unix Platforms pragma Export C u00003 system__standard_libraryS pragma Export C u00004 adaS pragma Export C u00005 ada__text_ioB pragma Export C u00006 ada__text_ioS pragma Export C u00007 ada__exceptionsB pragma Export C u00008 ada__exceptionsS pragma Export C u00009 gnatS
110. 2 6 Examples of gnatfind Usage gnatfind f xyz main adb Find declarations for all entities xyz referenced at least once in main adb The references are search in every library file in the search path The directories will be printed as well as the switch is set The output will look like directory main ads 106 14 xyz lt declaration directory main adb 24 10 xyz lt body directory foo ads 45 23 xyz lt declaration that is to say one of the entities xyz found in main adb is declared at line 12 of main ads and its body is in main adb and another one is declared at line 45 of foo ads gnatfind fs xyz main adb This is the same command as the previous one instead gnat find will display the content of the Ada source filelines The output will look like directory main ads 106 14 xyz lt declaration procedure xyz directory main adb 24 10 xyz lt body procedure xyz is directory foo ads 45 23 xyz lt declaration xyz Integer This can make it easier to find exactly the location your are looking for gnatfind r x main ads 123 foo adb Find references to all entities containing an x that are ref erenced on line 123 of main ads The references will be searched only in main adb and foo adb gnatfind main ads 123 Find declarations and bodies for all entities that are refer enced on line 123 of main ads This is the same as gnat find main adb 123 219 GNAT User s Guide for Unix Platfor
111. 3 as been added to the sources 235 GNAT User s Guide for Unix Platforms 16 4 Creating an Ada Library to be Used in a Non Ada Context The previous sections detailed how to create and install a library that was Usable from an Ada main program Using this library in a non Ada context is not possible because the elaboration of the library is automatically done as part of the main program elaboration GNAT also provides the ability to build libraries that can be used both in an Ada and non Ada context This section describes how to build such a library and then how to use it from a C program The method for interfacing with the library from other languages such as Fortran for instance remains the same 16 4 1 Creating the Library e Identify the units representing the interface of the library Here is an example of simple library interface package Interface is procedure Do_Something procedure Do_Something_Else end Interface e Usepragma Export Of pragma Convention for the exported entities Our package Interface is then updated as follow package Interface is procedure Do_Something pragma Export C Do Something do something procedure Do Something Else pragma Export C Do Something Else do something else end Interface e Compile all the units composing the library e Bind the library objects This step is performed by invoking gnatbind with the L lt prefix gt Switch gnatbind will then generate the
112. 32 Asm Output g Var_Out where the compiler since it does not analyze the Asm template string does not know you are using the ebx register In such cases you need to supply the clobber parameter to Asm to identify the registers that will be used by your assembly code Asm movl 40 hebx amp LF amp HT amp movl 4ebx 1 Inputs gt Unsigned_32 Asm_Input g Var_In Outputs gt Unsigned_32 Asm_Output g Var_Out Clobber gt ebx The Clobber parameter is a static string expression specifying the register s you are using Note that register names are not prefixed by a percent sign Also if more than one register is used then their names are separated by commas e g eax ebx The clobber parameter has several additional uses 1 Use the register name cc to indicate that flags might have changed 2 Use the register name memory if you changed a memory location 303 GNAT User s Guide for Unix Platforms 24 6 2 The volatile Parameter Compiler optimizations in the presence of Inline Assembler may some times have unwanted effects For example when an Asm invocation with an input variable is inside a loop the compiler might move the load ing of the input variable outside the loop regarding it as a one time initialization If this effect is not desired you can disable such optimizations by setting the volatile parameter to True for example Asm movl 40 hebx amp LF amp HT amp
113. 4888214 8148032 61 NUR AR NAMEN 16 8 BCC eee ees 38 GNATLINK linker name gnatmake g gnatlink NERONE ted NTA SAE 112 COE EA eee ea 116 gnat83 gcc ees 64 LINK gnatlink Mo T A ree KE 113 gnata gcc Vas pudet ra er Rt end Seb KEDE 51 SSRIS BCC pea Sed tern eae ipee Rd 39 cgnatb ECC ac spero erbe pere 44 RTS gnatbind 107 gnatc SOC cons cse Deep eR LEES 63 RTS gnatfind 212 guatD gcc ier ere ie eee 69 RIS SNatl1S 230 gnatdc sWitch 282 RTS gnatmake 121 TgnatE SOC rescue ieu cedes 61 70 RTS gnatxref 210 gnatem BCC 0000200 71 83 gnathtml 270 gnatf BCC occcnm ec ieee ree 44 A gnatbind 104 gnatG gcc eee eee 67 A gnatlink 112 8Nati gcc acer awh nana ecu 64 a gnatls Ls toy er 9 Shed 230 gnatk gcc ccce 66 a gnatmake 116 gnatl Beeli oe epe eePr pere eed 43 A gnatmake 120 gnatm Cte nee gare 44 al gnatmake 0 120 gnatn gcc eee eee 66 330 aL gnatmake 120 gnatN gcc een n 66 a0 gnatmake 120 gnatn switch 25 b ge ea 20502 PES dr t EE 38 gnatN switch 25 B SCS o ar ian citer A ree d
114. 6 C Type Integer Decl main ads 4 5 Modi main adb 4 8 Ref main adb 7 19 D Type Integer Decl main ads 6 5 Modi main adb 5 8 Foo Type Unit Decl main ads 3 15 Body main adb 2 15 Main Type Unit Decl main ads 2 9 Body main adb 1 14 Print Type Unit Decl bar ads 2 15 Ref main adb 6 12 7 12 that is the entity Main is declared in main ads line 2 col umn 9 its body is in main adb line 1 column 14 and is not referenced any where The entity Print is declared in bar ads line 2 column 15 and it it referenced in main adb line 6 column 12 and line 7 column 12 gnatxref packagel adb package2 ads gnatxref Will generates cross reference information for packagel adb package2 ads and any other package with ed by any of these 12 5 2 Using gnatxref with vi gnatxref Can generate a tags file output which can be used directly from vi Note that the standard version of vi will not work properly with overloaded symbols Consider using another free implementation of vi such as vim gnatxref v gnatfind adb gt tags will generate the tags file for gnat find itself if the sources are in the search path 218 SSS 23 May 2002 Chapter 12 The Cross Referencing Tools gnatxref and gnat find From vi you can then use the command tag entity replacing entity by whatever you are looking for and vi will display a new file with the corresponding declaration of entity 1
115. Ada amp C Programs Building a mixed application containing both Ada and C code may be a challenge for the unaware programmer As a matter of fact this interfacing has not been standardized in the Ada 95 reference manual due to the immaturity and lack of standard of C at the time This section gives a few hints that should makethis task easier In particular the first section addresses the differences with interfacing with C The second section looks into the delicate problem of linking the complete application from its Ada and C parts The last section give some hints on how the GNAT run time can be adapted in order to allow inter language dispatching with a new C compiler 2 11 1 Interfacing to C GNAT supports interfacing with C compilers generating code that is compatible with the standard Application Binary Interface of the given platform 30 esses 28 May 2002 Chapter 2 The GNAT Compilation Model Interfacing can be done at 3 levels simple data subprograms and classes In the first 2 cases GNAT offer a specific Convention CPP that behaves exactly like Convention c Usually C mangle names of subprograms and currently GNAT does not provide any help to solve the demangling problem This problem can be addressed in 2 ways e by modifying the C code in order to force a C convention using the extern C Syntax e by figuring out the mangled name and use it as the Link Name argument of the pragma import Interfa
116. Elaboration in GNAT External Calls The previous section discussed the case in which the execution of a par ticular thread of elaboration code occurred entirely within a single unit This is the easy case to handle because a programmer has direct and total control over the order of elaboration and furthermore checks need only be generated in cases which are rare and which the compiler can easily detect The situation is more complex when separate compilation is taken into account Consider the following 188 eee 28 May 2002 Chapter 11 Elaboration Order Handling in GNAT package Math is function Sqrt Arg Float return Float end Math package body Math is function Sqrt Arg Float return Float is begin end Sqrt end Math with Math package Stuff is X Float Math Sqrt 0 5 end Stuff with Stuff procedure Main is begin end Main where main is the main program When this program is executed the elaboration code must first be executed and one of the jobs of the binder is to determine the order in which the units of a program are to be elaborated In this case we have four units the spec and body of Math the spec of stuff and the body of main In what order should the four separate sections of elaboration code be executed There aresome restrictions in the order of elaboration that the binder can choose In particular if unit U has a with for a package x then you are assured t
117. GNAT User s Guide for Unix Platforms GNAT The GNU Ada 95 Compiler Document revision level 1 540 2 8 GNAT Version 3 15p Date 2002 05 22 04 20 30 Ada Core Technologies Inc Copyright 1995 2001 Free Software Foundation Permission is granted to copy distribute and or modify this document under the terms of the GNU Free Documentation License Version 1 1 or any later version published by the Free Software Foundation with the Invariant Sections being GNU Free Documentation License with the Front Cover Texts being GNAT User s Guide for Unix Platforms and with no Back Cover Texts A copy of the license is included in the section entitled GNU Free Documentation License About This Guide About This Guide This guide describes the use of GNAT a compiler and software develop ment toolset for the full Ada 95 programming language It describes the features of the compiler and tools and details how to use them to build Ada 95 applications What This Guide Contains This guide contains the following chapters Chapter 1 Getting Started with GNAT page 5 describes how to get started compiling and running Ada programs with the GNAT Ada programming environment Chapter 2 The GNAT Compilation Model page 15 describes the compilation model used by GNAT Chapter 3 Compiling Using gcc page 37 describes how to compile Ada programs with gcc the Ada compiler Chapter 4 Binding Using gnatbind page 75
118. GNAT User s Guide for Unix Platforms 254 23 May 2002 Chapter 19 Finding Memory Problems with GNAT Debug Pool 19 Finding Memory Problems with GNAT Debug Pool The use of unchecked deallocation and unchecked conversion can easily lead to incorrect memory references The problems generated by such references are usually difficult to tackle because the symptoms can be very remote from the origin of the problem In such cases it is very helpful to detect the problem as early as possible This is the purpose of the Storage Pool provided by GNAT Debug_Pools In order to usethe GNAT specific debugging pool the user must associate a debug pool object with each of the access types that may be related to suspected memory problems See Ada Reference Manual 13 11 type Ptr is access Some_Type Pool GNAT Debug Pools Debug Pool for Ptr Storage Pool use Pool GNAT Debug Pools is derived from of a GNAT specific kind of pool the Checked Pool Such pools like standard Ada storage pools allow the user to redefine allocation and deallocation strategies They also provide a checkpoint for each dereference through the use of the primi tive operation Dereference which is implicitly called at each dereference of an access value Oncean access type has been associated with a debug pool operations on values of thetype may raisefour distinct excepti ons which correspond to four potential kinds of memory corruption e GNAT Debug Pools
119. LABORATION ORDER BEGIN Object file option list hello o L L usr local gnat lib gcc lib alpha dec osf5 1 2 8 1 adalib usr local gnat lib gcc lib alpha dec osf5 1 2 8 1 adalib libgnat a lexc END Object file option list Here again the C code is exactly what is generated by the binder The functions of the various parts of this code correspond in an obvious man ner with the commented Ada code shown in the example in the previous section GNAT User s Guide for Unix Platforms 4 3 Consistency Checking Modes As described in the previous section by default gnatbina checks that object files are consistent with one another and are consistent with any source files it can locate The following switches control binder access to sources S Require source files to be present In this mode the binder must be able to locate all source files that are referenced in order to check their consistency In normal mode if a source file cannot be located it is simply ignored If you specify this switch a missing source file is an error Exdude source files In this mode the binder only checks that ALI files are consistent with one another Source files are not accessed The binder runs faster in this mode and there is still a guarantee that the resulting program is self consistent If a source file has been edited since it was last compiled and you specify this switch the binder will not de tect that the object fileis
120. PREPROCESS to invoke gnatprep e PSTA or STANDARD to invoke gnatpsta e STUB toinvoke gnatstub e XREF toinvoke gnatxref Note that the compiler is invoked using the command gnatmake f u Following the command you may put switches and arguments for the invoked tool gnat bind C main ali gnat ls a main gnat chop foo txt In addition for command BIND FIND LS or LIST LINK and XREF the project file related switches P x and vPx may be used in addition to the switches of the invoking tool For each of these command there is possibly a package in the main project that corresponds to the invoked tool 170 AA 28 May 2002 Chapter 10 GNAT Project Manager e package Binder for command BIND invoking gnatbind e package Finder for command FIND invoking gnat find e package natis for command LS or LIST invoking gnat1s e package Linker for command LINK invoking gnatlink e package cross Reference for command XREF invoking gnat1ink Package cGnat1s has a unique attribute switches a simple variable with a string list value It contains switches for the invocation of gnat1s project Proji is package gnatls is for Switches use a v end gnatls end Proji All other packages contains a switch Default Switches an associative array indexed by the programming language case insensitive and hav ingastringlist value Default Switches Ada contains theswitches for the invocation of the tool corresponding t
121. SOURCE_DIRS OBJECT LIST subst space OBJECT_DIRS ADA INCLUDE PATH SOURCE_LIST ADA OBJECT PATH OBJECT_LIST export ADA INCLUDE_PATH export ADA_OBJECT_PATH all gnatmake main_unit 246 TK gt amp L gt C T _oo o o O O UU VU VU UPUP PP woo ocowvy 28 May 2002 Chapter 18 Finding Memory Problems with gnatmem 18 Finding Memory Problems with gnatmem gnatmem is a tool that monitors dynamic allocation and deallocation activity in a program and displays information about incorrect deallo cations and possible sources of memory leaks Gnatmem provides three type of information e General information concerning memory management such as the total number of allocations and deallocations the amount of allo cated memory and the high water mark i e the largest amount of allocated memory in the course of program execution e Backtraces for all incorrect deallocations that is to say deal locations which do not correspond to a valid allocation e Information on each allocation that is potentially the origin of a memory leak The gnatmem command has two modes It can be used with gab or with instrumented allocation and deallocation routines The later mode is called the cmem mode Both modes produce the very same output 18 1 Running gnatmem GDB Mode The gnatmem command has the form gnatmem q n o file user program program argl or gnatmem
122. Shift_Right_ Arithmetic The corresponding subprogram dedaration must have two formal parameters The first one must be a signed integer type or a modular type with a binary modulus and the GNAT User s Guide for Unix Platforms second parameter must be of type Natural The return type must be the same as the type of the first argument The size of this type can only be 8 16 32 or 64 e binary arithmetic operators The correspond ing operator declaration must have parameters and result type that have the same root numeric type for example all three arelong float types This simplifies the definition of operations that use type checking to perform dimensional checks type Distance is new Long Float type Time is new Long Float type Velocity is new Long Float function D Distance T Time return Velocity pragma Import Intrinsic This common idiom is often programmed with a generic defi nition and an explicit body The pragma makes it simpler to introduce such dedarations It incurs no overhead in compi lation time or code size because it is implemented as a single machine instruction e Stdcall This is relevant only to NT Win95 implementations of GNAT and specifies that the Stdcall calling sequence will be used as defined by the NT API e Stubbed This is a special convention that indicates that the com piler should provide a stub body that raises Program Error 2 11 Building Mixed
123. System String_Ops_Concat_3 UET_Address System Stream_Attributes UET_Address System File_Control_Block UET_Address Ada Finalization List_Controller UET_Address Table of addresses of elaboration routines Used for zero cost exception handling to make sure these addresses are included in the top level procedure address table EA aliased constant array 1 23 of System Address adainit Code Address Do Finalize Code Address Ada Exceptions Elab_Spec Address System Exceptions Elab_Spec Address Interfaces C_Streams Elab_Spec Address System Exception_Table Elab_Body Address Ada Io_Exceptions Elab_Spec Address System Stack_Checking Elab_Spec Address System Soft_Links Elab_Body Address System Secondary_Stack Elab_Body Address Ada Tags Elab_Spec Address Ada Tags Elab_Body Address Ada Streams Elab_Spec Address System Finalization_Root Elab_Spec Address Ada Exceptions Elab_Body Address System Finalization_Implementation Elab_Spec Address System Finalization Implementation Elab Body Address Ada Finalization Elab Spec Address Ada Finalization List Controller Elab Spec Address System File_Control_Block Elab_Spec Address System File_Io Elab_Body Address Ada Text_Io Elab_Spec Address Ada Text_Io Elab_Body Address Start of processing for adainit begin Call SDP_Table_Build to build the top level proce
124. This is the most complete command it sets DIRs to the following value DIRS a a aa a aa aaa a ab a ac b b ba b ba baa b bb b bc THEE DIRS shell find ROOT_DIRECTORY type d print 244 8 May 2002 Chapter 17 Using the GNU make Utility 17 3 Generating the Command Line Switches Once you have created the list of directories as explained in the previous section see Section 17 2 Automatically Creating a List of Directories page 243 you can easily generate the command line arguments to pass to gnatmake For the sake of completeness this example assumes that the source path is not the same as the object path and that you have two separate lists of directories see Automatically creating a list of directories to create these variables SOURCE_DIRS OBJECT DIRS GNATMAKE SWITCHES patsubst aIl SOURCE_DIRS GNATMAKE SWITCHES patsubst a0 OBJECT_DIRS all gnatmake GNATMAKE_SWITCHES main unit 17 4 Overcoming Command Line Length Limits One problem that might be encountered on big projects is that many operating systems limit the length of the command line It is thus hard to give gnatmake the list of source and object directories This example shows how you can set up environment variables which will make gnatmake behave exactly as if the directories had bee
125. Unix Platforms gnatwi gcc 48 aghatwl gcc eae ye ia 49 egnatul gcc tweet aad ues 49 gnatuwL gcc te 49 gnatwo gec 49 gnatwD gec 49 gnatwp gcc isin ves 1804490409966464 4 49 sgnatwP gcc ee eed 50 Tgnatwrd gcc Eee 50 gnatwR gec 50 gnatus gcc eene 50 gnatwu gcc rises er UL A n a 50 sgnatw gcc coiere eere 51 zgnat gcc ileluir4pariuel9eu 70 h gnatbind 103 104 h gnatls arris eased RII Dg 230 h gnatname 134 L ECC c Bie OR hie Pitas 39 I gnathtml 2604022380404400 een 270 i gnatmake ae llam n ues 118 I gnatmake 0 120 i gnatmem wel pee E 249 IEEE hed etu xx reete 39 I gnatmake 0 120 j snatmake cireng bau 118 K gnatbind 104 k gnatchop sa sans ceg cini adonar 127 k gnatnake zs coche exe ls 118 1 gnatbind 104 1 gnathtml eraren e a Ang 270 1 gnatmake 118 L Snatmake a vsere sees 120 largs gnatmake 121 m gnatbind 102 M gnatbind 102 m gnatmake 118 M gnatmake 119 n gnatbind 105 n gnatlink a ERAI 112 n gnatmake 04 119 nostdinc gnatmake
126. __io_exceptions___elabs extern void system__exception_table_ extern void system__stack_checking___elabs extern void system__soft_links___elabb extern void system__secondary_stack___elabb O extern void ada__tags___elabs extern void ada__tags___elabb extern void ada__streams___elabs extern void system__finalization_root___elabs _elabb extern void system finalization implementation extern void ada exceptions extern void ada finalization elabs extern void ada finalization list controller elabs extern void system file control block elabs extern void system file io elabb extern void ada text io elabs extern void ada text io elabb void ea 23 O f adainit system__standard_library__adafinal ada__exceptions___elabs system__exceptions___elabs interfaces__c_streams___elabs system__exception_table___elabb ada__io_exceptions___elabs system__stack_checking___elabs system__soft_links___elabb system__secondary_stack___elabb elabs elabb ada__tags ada__tags _elabs extern void system__finalization_implementation___elabb O 95 GNAT User s Guide for Unix Platforms ada__streams___elabs system__finalization_root___elabs ada__exceptions___elabb _elabs _elabb system__finalization_implementation_ system__finalization_implementation__ ada__finalization___elabs ada__finalization__list_controller___elabs
127. a aes DASE 274 Introduction to GDB Commands 275 Using Ada ExpreSsiONS eee es 277 Calling User Defined Subprograms 277 Using the Next Command in a Function 278 Breaking on Ada ExceptiOnNS 278 Ada TASKS ves uri 2842 od oe E RR Ra RO d 279 Debugging Generic UnNitS eee eee eee 280 GNAT Abnormal Termination or Failureto Terminate siete Gah quuni AD do a d die waa SE ELA Ae EHE EL s 281 Naming Conventions for GNAT SourceFiles 282 Getting Internal Debugging Information 283 Stack T Eacebdck sz s issus S rove tS Eee IA 284 23 13 11 Non Symbolic Traceback 284 23 13 1 1 Tracebacks From an Unhandled E XCODUIUIA A oe aaa vb 284 23 13 1 2 Tracebacks From Exception OCCUIENCOS 287 vii GNAT User s Guide for Unix Platforms 23 13 1 3 Tracebacks From Anywhere in a Program since Scere D e e Ee ARN 288 23 13 2 SymbolicTraceback 290 23 13 2 1 Tracebacks From Exception OCGUEFEE ICOS Lie Ir Eph re RR rr 290 23 13 2 2 Tracebacks From Anywhere in a P OO AN ise eer cea one ws 292 24 InlineAssembler 293 24 1 Basic Assembler Syntax 293 24 2 A Simple Example of Inline Assembler 294 24 3 Output Variables in Inline Assembler 296 24 4 Input Variables in Inline
128. a new default path to the runtime library at com pilation time with the switch RTS rts path You can easily choose and change the runtime you want your program to be compiled with This switch is recognized by gcc gnatmake gnatbind gnatls gnatfind and gnatxref It is possible to install a library before or after the standard GNAT library by reordering the lines in the configuration files In general a library must be installed before the GNAT library if it redefines any part of it 16 3 Using an Ada Library In order to use a Ada library you need to make sure that this library is on both your source and object path Section 3 3 Search Paths and the Run Time Library RTL page 71 and Section 4 11 Search Paths for gnatbind page 108 For instance you can use the library mylib installed in dir my lib src and dir my lib obj with the following commands gnatmake al dir my lib src a0 dir my lib obj my appl V largs lmy lib This can be simplified down to the following gnatmake my appl when the following conditions are met e dir my_lib_src has been added by the user to the environment variable ADA INCLUDE PATH or by the administrator to the file ada source path e dir my lib obj has been added by the user to the environment variable ADA_OBJ ECTS PATH or by the administrator to the file ada object path e a pragma linker options as mentioned in Section 16 1 Creating an Ada Library page 23
129. a useful convention When writing nlineAssembler instructions you need to precede each register and variable name with a percent sign Since the assembler already requires a percent sign at the beginning of a register name you need two consecutive percent signs for such names in the Asm template string thus s eax In the generated assembly code one of the percent signs will be stripped off Names such as 0 1 2 etc denote input or output variables operands you later define using Input or output parameters to Asm An output variableis illustrated in the third statement in the Asm template string movl 4Aeax 0 The intent is to store the contents of the eax register in a variable that can be accessed in Ada Simply writing movi eax Flags would not necessarily work since the compiler might optimize by using a register to hold Flags and the expansion of the mov1 instruction would not be aware of this optimization The solution is not to store the result directly but rather to advise the compiler to choose the correct operand form that is the purpose of the o output variable Information about the output variable is supplied in the outputs parameter to Asm Outputs gt Unsigned 32 Asm Output g Flags The output is defined by the Asm output attribute of the target type the general format is Type Asm Output constraint string variable name The constraint string directs the compiler how to store access the associat
130. a warning message to alert you to a possible error Second if the compiler detects a situation that is sureto raise an exception at run time it generates a warning message The following shows an example of warning messages e adb 4 24 warning creation of object may raise Storage_Error e adb 10 17 warning static value out of range e adb 10 17 warning Constraint_Error will be raised at run time GNAT considers a large number of situations as appropriate for the generation of warning messages As always warn ings are not definite indications of errors For example if you do an out of range assignment with the deliberate in tention of raising a constraint Error exception then the warning that may be issued does not indicate an error Some of the situations for which GNAT issues warnings at least some of the time are given in the following list which is not necessarily complete e Possible infinitely recursive calls e Out of range values being assigned e Possible order of elaboration problems e Unreachable code e Fixed point type declarations with a null range GNAT User s Guide for Unix Platforms e Variables that are never assigned a value e Variables that are referenced before being initialized e Task entries with no corresponding accept statement e Duplicate accepts for the same task entry in a select e Objects that take too much storage e Unchecked conversion between types of differing sizes e Missing return s
131. aac is present and switch gnatA is not used It is allowed to specify several switches gnatec however only the last one on the command line will be taken into account 132 May 2002 Chapter 9 HandlingArbitrary File Naming Conventions Usinggnatname 9 Handling Arbitrary File Naming Conventions Using gnatname 9 1 Arbitrary File Naming Conventions The GNAT compiler must be able to know the source file name of a compilation unit When using the standard GNAT default file naming conventions ads for specs adb for bodies the GNAT compiler does not need additional information When the source file names do not follow the standard GNAT default file naming conventions the GNAT compiler must be given additional information through a configuration pragmas file see Chapter 8 Con figuration Pragmas page 131 or a project file When the non standard file naming conventions are well defined a small number of pragmas Source_File Name Specifying a naming pattern see Section 2 5 Alter native File Naming Schemes page 21 may be sufficient H owever if the file naming conventions are irregular or arbitrary a number of pragma Source_File_ Name for individual compilation units must be defined To help maintain the correspondence between compilation unit names and source file names within the compiler GNAT provides a tool gn
132. ad 38 gnato BCC skr iania a 60 327 b gnatbind 102 sgaatp ECC iste pa et tremens 60 327 b gnatlink 0000 112 gnatq gcc unen 44 B gnatlink ssssssssss 113 gnatR gcc v eee eee 70 b gnatmake 117 gt gt Mars gcc genado reed 62 bargs gnatmake 121 gnatt gcc vi eect ede t 67 PR fede en ut ost uin fibi Doer 38 sgnatI ECS a pue prions ge Pe den 62 c gnatbind 104 gnatu gcc eee sees eese 67 C gnatbind 104 gnatU ECC cer Re ree eve ees 43 c gnatchop 197 3gnatv GCC essor eem ttes 43 C gnat link aior ede 112 gnatW gec uns eee 65 c gnatmake 117 gnatwa gec 47 C gnatmake 117 gnatwA gec 47 c gnatname 134 gnatwc gcc cnn xha enn 47 cargs gnatmake 121 grnatwC gcc nee 48 d gnathtml ss 9665906444 883860164 270 gnatwe gcc 48 d gnatls o bep Go 230 gnatwf gcc 48 d gnatname 134 gnatwF gcc 48 D gnatname 0 134 gnatwh gcc orrn hioin piver iera 48 e gnatbind ssori yap ee cani peN 104 gnatwH gcc 48 341 GNAT User s Guide for
133. ada method2 this v printf in A method2 a value d Wn a value gt A A void 1 a value 1010 printf in A A a value d In a value gt Ada sources package body Simple_Cpp_Interface is procedure Ada_Method2 This in out A V Integer is begin Method1 This This A_Value V end Ada_Method2 end Simple_Cpp_Interface package Simple_Cpp_Interface is type A is limited record O_Value Integer A Value Integer end record pragma Convention C A procedure Method1 This in out A pragma Import C Method1 23 May 2002 Chapter 2 The GNAT Compilation M odel procedure Ada Method2 This in out A V Integer pragma Export C Ada_Method2 end Simple_Cpp_Interface 2 11 4 Adapting the Run Time to a New C Compiler GNAT offers the capability to derive Ada 95 tagged types directly from preexisting C classes and See Interfacing with C in the GNAT reference manual The mechanism used by GNAT for achieving such a goal has been made user configurable through a GNAT library unit Interfaces CPP The default version of this file is adapted to the GNU C compiler Internal knowledge of the virtual table layout used by the new C compiler is needed to configure properly this unit Thelnterface of this unit is known by the compiler and cannot be changed except for thevalueof theconstants definingthe characteristics of the virtual table CPP DT Prologue Size CPP DT En
134. age 27 The following switch is used in this situation n No main program The main program is not in Ada In this case most of the functions of the binder are still required but instead of generating a main program the binder generates a file con taining the following callable routines adainit You must call this routine to initialize the Ada part of the program by calling the necessary elaboration routines A call to adainit is required before the first call to an Ada subprogram Note that it is assumed that the basic execution environment must be setup to be appropriate for Ada execution at the point wherethe first Ada subprogram is called In particular if the Ada code will do any floating point operations then the FPU must be setup in an appropriate manner For the case of the x86 for example full precision mode is required The procedure GNAT Float_Control Reset may be used to ensure that the FPU is in theright state adafinal You must call this routine to perform any library level final ization required by the Ada subprograms A call to adafinal is required after the last call to an Ada subprogram and before the program terminates If the n switch is given more than one ALI file may appear on the command linefor gnatbind Thenormal closurecalculation is performed for each of the specified units Calculatingthe dosure means finding out the set of units involved by tracing with references The reason it is necessary to
135. age 273 for caveats Thewhere command is the first line of attack the variable 1ineno seen by print lineno used by the second phase of gnat1 and by the gcc backend indicates the source line at which the execution stopped and input file name indicates the name of the source file 23 11 Naming Conventions for GNAT Source Files In order to examine the workings of the GNAT system the following brief description of its organization may be helpful e Files with prefix sc contain the lexical scanner e All files prefixed with par are components of the parser The num bers correspond to chapters of the Ada 95 Reference Manual For example parsing of select statements can befound in par ch9 adb e All files prefixed with sem perform semantic analysis The num bers correspond to chapters of the Ada standard For example all 282 SSS 28 May 2002 Chapter 23 Running and Debugging Ada Programs issues involving context clauses can be found in sem ch10 aab In addition some features of the language require sufficient special processing to justify their own semantic files sem_aggr for aggre gates sem_disp for dynamic dispatching etc e All files prefixed with exp perform normalization and expansion of the intermediate representation abstract syntax tree or AST these files use the same numbering scheme as the parser and se mantics files For example the construction of record initialization procedures is d
136. agma Consider the following example Unit A with s unit B and calls B Func in elab code Unit B with s unit C and B Func calls C Func Now if weput a pragma Elaborate B in unita this ensures that the body of B is elaborated before the call but not the body of c so the call to c Func could still cause Program _ Error to be raised The effect of a pragma Elaborate_A11 is stronger it requires not only that the body of the named unit be elaborated before the unit doing the with but also the bodies of all units that the named unit uses following with links transitively For example if we put a pragma Elaborate All B in unit a then it requires not only that the body of B be elaborated before a but also the body of c because B with s c We are now in a position to give a usage rule in Ada 95 for avoiding elaboration problems at least if dynamic dispatching and access to sub program values are not used We will handle these cases separately later Theruleis simple If a unit has elaboration code that can directly or indirectly make a call to a subprogram in a with ed unit or instantiate a generic unit in a with ed unit then if the with ed unit does not have pragma Pure Or Preelaborate then the dient should have a pragma Elaborate All for the witn ed unit By following this rule a dient is assured that calls can be made without risk of an exception If this rule is not followed then a program may be in one of four states
137. aised during program execution 23 13 1 Non Symbolic Traceback Note this feature is not supported on all platforms See GNAT Traceback spec ing traceb ads for a complete list of supported platforms 23 13 1 1 Tracebacks From an Unhandled E xception A runtime non symbolic traceback is a list of addresses of call instruc tions To enable this feature you must use the E gnatbind s option With this option a stack traceback is stored as part of exception infor mation It is possible to retrieve this information using the standard Ada Exception Exception Information routine Let s have a look at a simple example 284 i 28 May 2002 Chapter 23 Running and Debugging Ada Programs procedure STB is procedure P1 is begin raise Constraint_Error end P1 procedure P2 is begin Pi end P2 begin P2 end STB gnatmake stb bargs E stb Execution terminated by unhandled exception Exception name CONSTRAINT ERROR Message stb adb 5 Call stack traceback locations 0x401373 0x40138b 0x40139c 0x401335 Ox4011c4 0x4011f1 0x77e892a4 As we see the traceback lists a sequence of addresses for the unhan dled exception coNsSTAINT ERROR raised in procedure P1 It is easy to guess that this exception come from procedure P1 To translate these addresses into the source lines where the calls appear the addr21ine tool described below is invaluable The use of this tool requires the program to be compiled with debug informa
138. akes care of the third and fourth steps of this process It determines which sources need to be compiled compiles them and binds and links the resulting object files Unlike some other Ada make programs the dependencies are always accurately recomputed from the new sources The source based ap proach of the GNAT compilation model makes this possible This means that if changes to the source program cause corresponding changes in dependencies they will always be tracked exactly correctly by gnatmake R WN H 6 1 Running gnatmake The usual form of the gnatmake command is gnatmake switches file name file names mode_switches The only required argument is one file name which specifies a com pilation unit that is a main program Several file names can be spec ified this will result in several executables being built If switches are present they can be placed before the first file name between file names or after the last file name If mode switches are present they must always be placed after the last file name and all switches If you are using standard file extensions adb and ads then the extension may be omitted from the file name arguments However if you are using non standard extensions then it is required that the extension be given A relative or absolute directory path can be specified in a file name in which case the input source file will be searched for in the specified directory only Otherwise the input
139. akes into account all the Ada 95 rules that estab lish dependencies among units These include dependencies that result from inlining subprogram bodies and from genericinstantiation Unlike some other Ada make tools gnatmake does not rely on the dependencies that were found by the compiler on a previous compilation which may possibly be wrong when sources change gnatmake determines the exact set of dependencies from scratch each time it is run 1 5 Introduction to Glide and GVD Although it is possible to develop programs using only the command line interface gnatmake etc a graphical Interactive Development En vironment can make it easier for you to compose navigate and debug programs This section describes the main features of Glide the GNAT graphical IDE and also shows how to use the basic commands in GVD the GNU Visual Debugger Additional information may be found in the on line help for these tools 1 5 1 Building a New Program with Glide The simplest way to invoke Glide is to enter glide at the command prompt It will generally be useful to issue this as a background com mand thus allowing you to continue using your command window for other purposes while Glide is running glide amp Glide will start up with an initial screen displaying the top level menu items as well as some other information The menu selections are as follows e Buffers e Files e Tools e Edit e Search e Mule e Glide GNAT User s Guid
140. ality in the Ada 95 Reference Manual Any unit can be compiled in semantics checking only mode induding units that would not normally be compiled sub units and specifications where a separate body is present 3 2 10 Compiling Ada 83 Programs gnat83 Although GNAT is primarily an Ada 95 compiler it accepts this switch to specify that an Ada 83 program is to be com piled in Ada83 mode I f you specify this switch GNAT rejects most Ada 95 extensions and applies Ada 83 semantics where this can be done easily It is not possible to guarantee this switch does a perfect job for example some subtletests such as are found in earlier ACVC tests that have been removed from the ACVC suite for Ada 95 may not compile correctly However for most purposes using this switch should help to ensure that programs that compile correctly under the gnat 83 switch can be ported easily to an Ada 83 compiler This is the main use of the switch With few exceptions most notably the need to use lt gt on unconstrained generic formal parameters the use of the new Ada 95 keywords and the use of packages with optional bod ies it is not necessary to use the gnat 83 Switch when com piling Ada 83 programs because with rare exceptions Ada 95 is upwardly compatible with Ada 83 This means that a correct Ada 83 program is usually also a correct Ada 95 program 3 2 11 Character Set Control gnatic Normally GNAT recognizes the Latin 1 charac
141. alue If no value is given on the command line then symbol is considered to be True This switch can be used in place of a definition file Causes a Source Reference pragma to be generated that references the original input file so that error messages will use the file name of this original file The use of this switch implies that preprocessor lines arenot to be removed from the 225 GNAT User s Guide for Unix Platforms file so its use will force b mode if c has not been specified explicitly Note that if the file to be preprocessed contains multiple units then it will be necessary to gnat chop the output file from gnatprep Ifa Source Reference pragma is present in the preprocessed file it will be respected by gnatchop r SO that the final chopped files will correctly refer to the original input source file for gnatprep s Causes a sorted list of symbol names and values to be listed on the standard output file u Causes undefined symbols to be treated as having the value FALSE in the context of a preprocessor test In the absence of this option an undefined symbol in a if or elsif test will be treated as an error Note if neither b nor c is present then preprocessor lines and deleted lines are completely removed from the output unless r is specified in which case b is assumed 14 3 Form of Definitions File The definitions file contains lines of the form symbol value where symbol is an identifier follow
142. an define a project Tasking Proj that inherits seq Proj tasking pack adb tasking proj gpr project Tasking Proj extends seq seq_proj is end Tasking Proj The version of pack adb used in a build depends on which project file is specified Note that we could have designed this using project import rather than project inheritance a base project would contain the sources for pack ads and proc adb a sequential project would import base and add pack adb and likewise a tasking project would import base and add a different version of pack adb The choice depends on whether 146 sss 28 May 2002 Chapter 10 GNAT Project Manager other sources in the original project need to be overridden If they do then project extension is necessary otherwise importing is sufficient 10 3 Project File Syntax This section describes the structure of project files A project may be an independent project entirely defined by a single project file Any Ada source file in an independent project depends only on the predefined library and other Ada source files in the same project A project may also depend on other projects in either or both of the following ways e t may import any number of projects e t may extend at most one other project The dependence relation is a directed acydic graph the subgraph re flecting the extends relation is a tree A project s immediate sources are the source files
143. as a Front Cover Text and a passage of up to 25 words as a Back Cover Text to the end of the list of Cover Texts in the Modified Version Only one passage of F ront Cover Text and one of Back Cover Text may be added by or through arrange ments made by any one entity If the Document already indudes a cover text for the same cover previously added by you or by arrangement made by the same entity you are acting on behalf of you may not add another but you may replacethe old one on explicit permission from the previous publisher that added the old one Theauthor s and publisher s of the Document do not by this License give permission to use their names for publicity for or to assert or imply endorsement of any Modified Version 5 COMBINING DOCUMENTS You may combine the Document with other documents released un der this License under the terms defined in section 4 above for modified 337 GNAT User s Guide for Unix Platforms versions provided that you include in the combination all of the I nvari ant Sections of all of the original documents unmodified and list them all as Invariant Sections of your combined work in its license notice The combined work need only contain one copy of this License and multiple identical Invariant Sections may be replaced with a single copy Iftherearemultiplel nvariant Sections with thesamename but different contents makethetitle of each such section unique by adding at the end of it in paren
144. as in Ada The marking the start of a preprocessor line must be the first non blank character on the line i e it must be preceded only by spaces or horizontal tabs Symbol substitution outside of preprocessor lines is obtained by using the sequence symbol anywhere within a source line except in a comment or within a string literal The identifier following the s must match one of the symbols defined in the symbol definition file and the result is to substitute the value of the symbol in place of ssymbol in the output file Note that although the substitution of strings within a string literal is not possible it is possible to have a symbol whose defined value is a string literal So instead of setting XY Z to he11o and writing Header String XYZ you should set XYZ to hello and write Header String XYZ and then the substitution will occur as desired 228 28 May 2002 Chapter 15 The GNAT Library Browser gnat1s 15 The GNAT Library Browser gnatls gnat1s is a tool that outputs information about compiled units It gives the relationship between objects unit names and source files It can also be used to check the source dependencies of a unit as well as various characteristics 15 1 Running gnat1s The gnat1s command has the form gnatls switches object or ali file The main argument is the list of object or a1i f
145. as will generate an object file nothing out 24 3 Output Variables in Inline Assembler The examples in this section showing how to access the processor flags illustrate how to specify the destination operands for assembly language statements with Interfaces use Interfaces with Ada Text_I0 use Ada Text_I0 with System Machine_Code use System Machine_Code procedure Get_Flags is Flags Unsigned_32 use ASCII begin Asm pushfl amp LF amp HT amp push flags on stack popl eax amp LF amp HT amp load eax with flags movl eax 40 store flags in variable Outputs gt Unsigned 32 Asm Output g Flags Put Line Flags register amp Flags Img end Get Flags In order to havea nicely aligned assembly listing we have separated multiple assembler statements in the Asm template string with linefeed ASCII LF and horizontal tab ASCII HT characters The resulting section of the assembly output file is APP pushfl popl eax movl eax 40 ebp NO_APP It would have been legal to write the Asm invocation as Asm pushfl popl eax movl 4eax 0 but in the generated assembler file this would come out as APP pushfl popl eax movl eax 40 ebp NO_APP 296 3 May 2002 Chapter 24 Inline Assembler which is not so convenient for the human reader We use Ada comments at the end of each line to explain what the assembler instructions actually do This is
146. asks Generally the model of execution of an Ada program is that all units are elaborated and then execution of the program starts However the declaration of library tasks definitely does not fit this model The reason for this is that library tasks start as soon as they are dedared more precisely as soon as the statement part of the endosing package body is reached that is to say before elaboration of the program is complete This means that if such a task calls a subprogram or an entry in another task the callee may or may not be elaborated yet and in the standard Reference Manual model of dynamic elaboration checks you can even get timing dependent Program_Error exceptions since there can be a race between the elaboration code and the task code The static model of elaboration in GNAT seeks to avoid all such dy namic behavior by being conservative and the conservative approach in 192 28 May 2002 Chapter 11 Elaboration Order Handling in GNAT this particular case is to assume that all the code in a task body is po tentially executed at elaboration time if a task is declared at the library level This can definitely result in unexpected circularities Consider the following example package Decls is task Lib_Task is entry Start end Lib_Task type My_Int is new Integer function Ident M My Int return My Int
147. ater access by other units including Ada Command Line gnat argc Integer 4 28 May 2002 Chapter 4 Binding Using gnatbind gnat_argv System Address gnat_envp System Address The actual variables are stored in a library routine This is useful for some shared library situations where there are problems if variables are not in the library pragma Import C gnat_argc pragma Import C gnat_argv pragma Import C gnat_envp The exit status is similarly an external location gnat_exit_status Integer pragma Import C gnat_exit_status GNAT_Version constant String GNAT Version 3 15w 20010315 pragma Export C GNAT_Version __gnat_version This is the generated adafinal routine that performs finalization at the end of execution In the case where Ada is the main program this main program makes a call to adafinal at program termination procedure adafinal pragma Export C adafinal adafinal This is the generated adainit routine that performs initialization at the start of execution In the case where Ada is the main program this main program makes a call to adainit at program startup procedure adainit pragma Export C adainit adainit This routine is called at the start of execution It is a dummy routine that is used by t
148. atname to generate the required pragmas for a set of files 9 2 Running gnatname The usual form of the gnatname command is gnatname switches naming_patterns All of the arguments are optional When used with no arguments gnatname Will create a file gnat adc iN the current working directory that contains configuration pragmas for all compilation units in the current directory To find all compilation units gnatname Will use the GNAT compiler in syntax check only mode on all regular files For those files that contain an Ada compilation unit a pragma Source File Name Will be generated Oneor several Naming Patterns may be given as arguments to gnatname Each Naming Pattern is enclosed between double quotes A Naming Pattern is a regular expression similar to the wildcard patterns used in file names by the Unix shells or the DOS prompt Examples of Naming Patterns are x 12 ada ad sb 133 GNAT User s Guide for Unix Platforms body spec For a more complete description of the syntax of Naming Patterns see the second kind of regular expressions described in g regexp ads the Glob regular expressions SpecifyingnoNamingPattern is equivalent to specifying the single N am ing Pattern 9 3 Switches for gnatname Switches for gnatname must precede any specified Naming Pattern You may specify any of the following switches to gnatname c file d dir D file P proj Create a conf
149. aty then all key words must be in lower case with the exception of keywords such as digits used as attribute names to which this check does not apply 1 check layout If the letter appears in the string after gnaty then layout of statement and declaration constructs must follow the rec ommendations in the Ada Reference M anual as indicated by the form of the syntax rules For example an else keyword must be lined up with the corresponding i f keyword There are two respects in which the style rule enforced by this check option are more liberal than those in the Ada Reference Manual First in the case of record declarations it is permissible to put the record keyword on the same line as the type keyword and then the end in end record Must line up under type For example either of the following two layouts is acceptable 56 23May2002 Chapter 3 Compiling Using gcc type q is record a integer b integer end record type q is record a integer b integer end record Second in the case of a block statement a permitted alterna tive is to put the block label on the same lineas the declare Or begin keyword and then line the ena keyword up under the block label For example both the following are permit ted Block declare A Integer 3 begin Proc A A end Block Block declare A Integer 3 begin Proc A A end Block The same
150. be able to specify more than one ALI file is that a given program may invoke two or more quite separate groups of Ada units Thebinder takes the name of its output file from thelast specified ALI file unless overridden by the use of the V o i1eV ouTPUT fileN The output is an Ada unit in source form that can be compiled with GNAT unless the C switch is used in which case the output is a C source file which must be compiled using the C compiler This compilation occurs automatically as part of the gnat link processing 105 GNAT User s Guide for Unix Platforms Currently the GNAT run time requires a FPU using 80 bits mode precision Under targets where this is not the default it is required to call GNAT Float Control Reset before using floating point numbers this indudefloat computation float input and output in theAda code A side effect is that this could be the wrong mode for the foreign code where floating point computation could be broken after this call 4 8 Binding Programs with No Main Subprogram Itispossibletohavean Ada program which does not have a main subpro gram This program will call the elaboration routines of all the packages then the finalization routines Thefollowing switch is used to bind programs organized in this man ner z Normally the binder checks that the unit name given on the command line corresponds to a suitable main subprogram When this switch is used a list of ALI files can be given and t
151. bly containing a gnat adc file is the representation of a compilation environment For more information on the gnat adc file see the section on handling of configuration pragmas see Section 8 1 Handling of Configuration Pragmas page 132 Second in compilation mode if gnatchop is given a file that starts with configuration pragmas and contains one or more units then these configuration pragmas are prepended to each of the chopped files This behavior provides the required behavior described in the RM for the actions to be taken on compiling such a file namely that the pragmas apply to all units in the compilation but not to subsequently compiled units Finally if configuration pragmas appear between units they are ap pended to the previous unit This results in the previous unit being illegal since the compiler does not accept configuration pragmas that follow a unit This provides the required RM behavior that forbids con figuration pragmas other than those preceding the first compilation unit of a compilation For most purposes gnatchop will be used in default mode The com pilation mode described above is used only if you need exactly accurate behavior with respect to compilations and you have files that contain multiple units and configuration pragmas In this circumstance the use of gnat chop with the compilation mode switch provides the required be havior and is for example the mode in which GNAT processe
152. boration The trouble is that it becomes impossible to tell at compile time which procedure is being called This means that it is not possible for the binder to analyze the elaboration requirements in this case If at the point at which the access value is created i e the evaluation Of P Access for a Subprogram P the body of the subprogram is known to have been elaborated then the access value is safe and its use does not require a check This may be achieved by appropriate arrangement of the order of declarations if the subprogram is in the current unit or if the subprogram is in another unit by using pragma Pure Preelaborate Or Elaborate_Body on the referenced unit 204 2893 May 2002 Chapter 11 Elaboration Order Handling in GNAT If the referenced body is not known to have been elaborated at the point the access val ue is created then any use of the access value must do a dynamic check and this dynamic check will fail and raise a Program _ Error exception if the body has not been elaborated yet GNAT will generate the necessary checks and in addition if the gnatw1 Switch is set will generate warnings that such checks are required The use of dynamic dispatching for tagged types similarly generates a requirement for dynamic checks and premature calls to any primitive operation of a tagged type before the body of the operation has been elaborated will result in the raising of Program Error 11 11 Summary of Pro
153. bout the point of elaboration of such units and in par ticular does not need to check any calls to any subprograms in this unit pragma Preelaborate This pragma places slightly less stringent restrictions on a unit than does pragma Pure but these restrictions are still sufficient to ensure that there are no elaboration problems with any calls to the unit pragma Elaborate_Body This pragma requires that the body of a unit be elaborated immediately after its spec Suppose a unit a has such a pragma and unit B does a with of unit a Recall that the standard rules require the spec of unit a to be elaborated before the with ing unit given the pragma in a we also know that the body of a will be elaborated before p so that calls to A are Safe and do not need a check Note that unlike pragma Pure and pragma Preelaborate the use of Elaborate Body does not guarantee that the program is free of elabo ration problems because it may not be possible to satisfy the requested elaboration order Let s go back to the example with unit_1andunit_ 2 If a programmer marks Unit_1 as Elaborate Body and not unit 2 then the order of elaboration will be Spec of Unit_2 Spec of Unit 1 Body of Unit 1 Body of Unit 2 Now that means that the call to Func 1 in unit 2 need not be checked it must be safe But the call to Func 2 in unit 1 may still fail if Expression 1 is equal to 1 and the programmer must still take re sponsibility for this not being
154. brary search path switches aldir aLdir aOdir Adir Idir Ldir nostdinc 120 When looking for source files also look in directory air The order in which source files search is undertaken is de scribed in Section 3 3 Search Paths and the Run TimeLi brary RTL page 71 Consider dir as being an externally provided Ada library In structs gnatmake to skip compilation units whose a11 files have been located in directory air This allows you to have missing bodies for the units in air and to ignore out of date bodies for the same units You still need to specify the loca tion of the specs for these units by usingthe switches ardir or Idir Note this switch is provided for compatibility with previous versions of gnatmake The easier method of caus ingstandard libraries to be exduded from consideration is to write protect the corresponding ALI files When searching for library and object files look in directory dir Theorder in which library files aresearched is described in Section 4 11 Search Paths for gnatbind page 108 Equivalent to andir aldir Equivalent to aodir aidir Do not look for source files in the directory containing the source file named in the command line Do not look for ALI or object files in the directory where gnatmake was invoked Add directory dir tothe list of directories in which thelinker will search for libraries This is equivalent to 1args Ldir Do not look for
155. by using the gnatmake util ity program that given the name of the main program automatically performs the necessary compilation binding and linking steps 1 2 Running a Simple Ada Program Any text editor may be used to prepare an Ada program If Glide is used the optional Ada mode may be helpful in laying out the program The program text is anormal text file We will suppose in our initial example that you have used your editor to prepare the following standard format text file with Ada Text_I0 use Ada Text I0 procedure Hello is begin Put_Line Hello WORLD end Hello This file should be named hello adb With the normal default file naming conventions GNAT requires that each file contain a single com pilation unit whose file name is the unit name with periods replaced by hyphens the extension is ads for a spec and adb for a body You can override this default file naming convention by use of the special pragma Source File Name see Section 2 4 Using Other File Names page 20 Alternatively if you want to rename your files according to this default convention which is probably more convenient if you will be using GNAT for all your compilations then the gnat chop utility can be GNAT User s Guide for Unix Platforms used to generate correctly named source files see Chapter 7 Renaming Files Using gnatchop page 125 You can compile the program using the following command is used
156. call to B within the body of c is correct but the call to a within the body of B is incorrect because the body of a has not been elaborated so Program Error will be raised on the call to a In this case GNAT will generate a warning that Program Error may be raised at the point of the call Let s look at the warning 186 23May 2002 Chapter 11 Elaboration Order Handling in GNAT procedure x is function return Integer function B return Integer function C return Integer function B return Integer is begin return A end gt gt gt warning call to A before body is elaborated may raise Program Error gt gt gt warning B called at line 7 gt gt gt warning C called at line 9 function C return Integer is begin return B end 9 X Integer C 10 11 function return Integer is begin return 1 end 12 13 begin 14 null 15 end Note that the message here says may raise instead of the direct case where the message says will be raised That s because whether a is actually called depends in general on run time flow of control For example if the body of B said function B return Integer is begin if some condition depending on input data then return A else return 1 end if end B then we could not know until run time whether the incorrect call toA
157. called untyped variables Typed variables are particularly useful in case Constructions see Section 10 3 8 case Constructions page 154 A string type declaration starts with the reserved word type followed by the name of the string type case insensitive followed by the reserved word is followed by a parenthesized list of one or more string literals separated by commas followed by a semicolon The string literals in the list are case sensitive and must all be differ ent They may indude any graphic characters allowed in Ada induding spaces A string type may only be dedared at the project level not insidea package A string type may be referenced by its name if it has been declared in the same project file or by its project name followed by a dot followed by the string type name 10 3 5 Variables A variable may be dedared at the project filelevel or in a package Here are some examples of variable dedarations This OS OS external 0S a typed variable declaration That OS Linux an untyped variable declaration A typed variable declaration includes the variable name followed by a colon followed by the name of a string type followed by followed by a simple string expression An untyped variable dedaration indudes the variable name followed by followed by an expression Note that despite the terminology this form of declaration resembles more an assignment than a declaration in Ada It is
158. cc can be moved to the body The default is that such warnings are not generated This switch also ac tivates warnings on unreferenced formals it is includes the effect of gnatwf This warning can also be turned on using gnatwa gnatwU suppress warnings on unused entities This switch suppresses warnings for unused en tities and packages It also turns off warnings on unreferenced formals and thus indudes the effect of gnatwF A string of warning parameters can be used in the same parameter For example gnatwaLe Would turn on all optional warnings except for elaboration pragma warnings and also specify that warnings should be treated as errors w This switch suppresses warnings from the gcc backend It may be used in conjunction with gnatws to ensure that all warnings are sup pressed during the entire compilation process 3 2 2 Debugging and Assertion Control gnata The pragmas Assert and Debug normally have no effect and are ignored This switch where a stands for assert causes Assert and Debug pragmas to be activated The pragmas have the form pragma Assert Boolean expression static string expression pragma Debug procedure call The Assert pragma causes Boolean expression to be tested If the result is True the pragma has no effect other than possible side effects from evaluating the expression If the result is False the exception Assert Failure de dared in the package syste
159. cedures for Elaboration Control First compile your program with the default options using none of the special elaboration control switches If the binder successfully binds your program then you can be confident that apart from issues raised by the use of access to subprogram types and dynamic dispatching the program is free of elaboration errors If it is important that the program be portable then use the gnatw1 switch to generate warnings about missing Elaborate A11 pragmas and supply the missing pragmas If the program fails to bind using the default static elaboration han dling then you can fix the program to eliminate the binder message or recompile the entire program with the gnatE switch to generate dy namic elaboration checks and if you are surethere really are no elabo ration problems use a global pragma suppress Elaboration Checks 11 12 Other Elaboration Order Considerations This section has been entirely concerned with the issue of finding a valid elaboration order as defined by the Ada Reference Manual In a case where several elaboration orders are valid the task is to find one of the possible valid elaboration orders and the static model in GNAT will ensure that this is achieved The purpose of the elaboration rules in the Ada Reference Manual is to make sure that no entity is accessed before it has been elaborated For a subprogram this means that the spec and body must have been elaborated before the s
160. cessor_Type 2 00 and 2 0100 and 2 0100 then Signature Family Signature Model Type_Found True Ada Text_I0 Put_Line x486SL processor end if x486DX2 Write Back if Signature Processor Type 24004 and 2 0100 and 2401114 then Signature Family Signature Model Type Found True Ada Text IO Put Line Write Back Enhanced x486DX2 processor end if x486DX4 if Signature Processor Type 2 00 and 2 0100 and 2 1000 then Signature Family Signature Model Type_Found True Ada Text_I0 Put_Line x486DX4 processor end if x486DX4 Overdrive if Signature Processor_Type 2 01 and 2 0100 and 2 1000 then Signature Family Signature Model Type_Found True Ada Text_I0 Put_Line x486DX4 OverDrive processor end if Pentium 60 66 if Signature Processor_Type 2 00 and 2 0101 and 2 0001 then Signature Family Signature Model Type_Found True Ada Text_I0 Put_Line Pentium processor 60 66 end if Pentium 75 90 100 120 133 150 166 200 if Signature Processor Type 2 00 and Signature Family 2 0101 and 308 gt 8283 May 2002 Chapter 24 Inline Assembler Signature Model 2 0010 then Type_Found True Ada Text I0 Put Line Pentium processor 75 90 100 120 133 150 166 200 end if Pentium OverDrive 60 66 if Signature Processor Type 2 01 and 2 0101 and 2 0001 then Signature Famil
161. ch u is used on the command line then invoking gnatmake with no main on the command line will result in all immediate sources of the project file being checked and potentially recompiled Depending on the presence of the switch u sources from other project files on which the immediate sources of the main project file depend are also checked and potentially recompiled n other words the 169 GNAT User s Guide for Unix Platforms u switch is applied to all of the immediate sources of themain project file 10 13 2 The GNAT Driver and Project Files A number of GNAT tools other than gnatmake are project aware gnatbind gnat find gnatlink gnatls and gnatxref However none of these tools can be invoked directly with a project file switch P They need to be invoke through the gnat driver The gnat driver is a front end that accepts a number of commands and call the corresponding tool It has been designed initially for VMS to convert VMS style qualifiers to Unix style switches but it is now available to all the GNAT supported platforms On non VMS platforms the gnat driver accepts the following com mands case insensitive e BIND toinvoke gnatbind e CHOP toinvoke gnatchop e COMP or COMPILE toinvoke the compiler e ELIM toinvoke gnatelim e FIND toinvoke gnat find e KR or KRUNCH toinvoke gnatkr e LINK toinvoke gnatlink e LS or LIST to invoke gnatis e MAKE toinvoke gnatmake e NAME toinvoke gnatname e PREP or
162. ches The command lines for gnatxref is gnatxref switches sourcefile1 sourcefile2 where sourcefilel sourcefile2 identifies the source files for which areport is to be generated The with ed units will be processed too You must provide at least one file These file names are considered to be regular expressions so for instance specifying source adb is the same as giving every file in the current directory whose name starts with source and whose extension is adb The switches can be a If this switch is present gnatfind and gnatxref will parse the read only files found in the library search path Other wise these files will beignored This option can be used to protect Gnat sources or your own libraries from being parsed 209 GNAT User s Guide for Unix Platforms aIDIR aODIR nostdinc nostdlib RTS rts IDIR pFILE 210 thus making gnat find and gnatxref much faster and their output much smaller When looking for source files also look in directory DIR The order in which source file search is undertaken is the same as for gnatmake When searching for library and object files look in directory DIR Theorder in which library files are searched is the same as for gnatmake Do not look for sources in the system default directory Do not look for library files in the system default directory path Specifies the default location of the runtime library
163. chopped contain duplicated units This switch bypasses this check and causes all but the last instance of such duplicated units to be skipped 23 May 2002 Chapter 7 Renaming Files Using gnat chop GCC XXXX Specify the path of the GNAT parser to be used When this switch is used no attempt is made to add the prefix to the GNAT parser executable 7 5 Examples of gnatchop Usage gnatchop w hello s ada ichbiah files Chops the source file hello s ada The output files will be placed in the directory ichbiah files overwriting any files with matching names in that directory no files in the current diredory are modified gnatchop archive Chops the source file archive into the current directory One useful application of gnatchop is in sending sets of sources around for example in email messages Therequired sources are simply concatenated for example using a Unix cat command and then gnatchop is Used at the other end to reconstitute the original file names gnatchop filel file2 file3 direc Chops all units in files ilei file2 file3 placing the resulting files in the directory direc Note that if any units occur more than once anywhere within this set of files an error message is generated and no files are written To override this check use the w switch in which case the last occurrence in the last file will be the one that is output and earlier duplicate occurrences for a given unit will be skipped
164. cing at the class level can be achieved by using the GNAT specific pragmas such as cPP Classand CPP virtual Seethe GNAT Reference Manual for additional information 2 11 2 Linking a Mixed C amp Ada Program Usually the linker of the C development system must be used to link mixed applications because most C systems will resolve elaboration issues such as calling constructors on global class instances transpar ently during the link phase GNAT has been adapted to ease the use of a foreign linker for the last phase Three cases can be considered 1 Using GNAT and G GNU C compiler from the same GCC installation The c linker can simply be called by using the c specific driver called c Note that this setup is not very common because it may request recompiling the whole GCC tree from sources and it does not allow to upgrade easily to a new version of one compiler for one of the two languages without taking the risk of destabilizing the other c c file1 C c c file2 C gnatmake ada unit largs filel o file2 o LINK c 2 Using GNAT and G from 2 different GCC installations If both compilers are on the PATH the same method can be used It is important to be aware that environment variables such as CINCLUDE PATH GCC_EXEC PREFIX BINUTILS ROOT or GCC_ROOT will affect both compilers at the same time and thus may make one of the 2 compilers operate improperly if they are set for the other In particular it is im
165. csets adb in the GNAT compiler sources You will need to obtain a full source release of GNAT to obtain this file 2 2 3 Wide Character Encodings GNAT allows wide character codes to appear in character and string literals and also optionally in identifiers by means of the following possible encoding schemes Hex Coding In this encoding a wide character is represented by the fol lowing five character sequence ESCabcd Where a b c a are the four hexadecimal characters using uppercase letters of the wide character code For example ESC A345 is used to represent the wide character with code 16 A345 This scheme is compatible with use of the full Wide Character set U pper H alf Coding Thewide character with encoding 16 abca where the upper bit is on in other words a is in the range 8 F is repre sented as two bytes 16 ab and 16 cd The second byte cannot be a format control character but is not required to bein the upper half This method can be also used for shift JIS or EUC where the internal coding matches the external codi ng 17 GNAT User s Guide for Unix Platforms Shift J 1S Coding A widecharacter is represented by a two character sequence 16 ab and 16 cd with therestrictions described for upper half encoding as described above The internal character code is the corresponding J S character according tothe stan dard algorithm for Shift J IS conversion Only characters de fined in the IS code s
166. ctory from which Glide was launched To execute the program choose ada and then run You should see the program s output displayed in the bottom window Hello world 1 Hello world 2 Hello world 3 Hello world 4 Hello world 5 1 5 2 Simple Debugging with GVD This section describes how to set breakpoints examine modify variables and step through execution In order to enable debugging you need to pass the g switch to both the compiler and to gnat link If you are using the command line passing g to gnatmake will have this effect You can then launch GVD eg on the hello program by issuing the command gvd hello 11 GNAT User s Guide for Unix Platforms If you are using Glide then g is passed to the relevant tools by default when you do a build Start the debugger by selecting the ada menu item and then Debug GVD comes up in a multi part window One pane shows the names of files comprising your executable another pane shows the source code of the current unit initially your main subprogram another pane shows the debugger output and user interactions and the fourth pane the data canvas at the top of the window displays data objects that you have selected To the left of the source file pane you will notice green dots adjacent to some lines These are lines for which object code exists and where breakpoints can thus be set You set reset a breakpoint by clicking the green dot When a breakpoin
167. d package simple name package renaming renames lt project_ gt simple_name lt package_ gt simple_name typed string declaration type typed string gt simple name is literal string i literal string other declarative item attribute declaration typed variable declaration variable declaration case construction attribute declaration for attribute use expression attribute simple attribute gt simple name associative array attribute gt simple name literal string typed variable declaration typed variable gt simple name typed string name string expression variable declaration variable gt simple name expression expression term amp term term literal_string string_list lt variable_ gt name external_value 175 GNAT User s Guide for Unix Platforms attribute_reference literal_string same as Ada string_list lt string_ gt expression lt string gt expression external_value external literal string literal string attribute_reference attribute parent lt simple_attribute_ gt simple_name literal string attribute_parent project lt project_or_package gt simple_name lt project_ gt simple_name lt package_ gt simple_name case_construction case lt typed_variable_ gt name is dcase item end case case item when d
168. d and understand the generated main program It can also be debugged just like any other Ada code provided the g switch is used for gnatbind and gnatlink However for some purposes it may be convenient to generatethe main program in C rather than Ada This may for example be helpful when you are generating a mixed language program with the main program in C The GNAT compiler itself is an example The use of the c switch for both gnatbind and gnatlink will cause the program to be generated in C and compiled using the gnu C compiler The following shows the C code generated for the same Hello World program ifdef __STDC__ define PARAMS paramlist paramlist else define PARAMS paramlist endif extern void __gnat_set_globals PARAMS int int int int int int void PARAMS void int int extern void adafinal PARAMS void extern void adainit PARAMS void extern void system__standard_library__adafinal PARAMS void extern int main PARAMS int char char extern void exit PARAMS int extern void __gnat_break_start PARAMS void extern void _ada_hello PARAMS void extern void __gnat_initialize PARAMS void extern void __gnat_finalize PARAMS void extern void ada__exceptions___elabs PARAMS void extern void system__exceptions___elabs PARAMS void extern void interfaces__c_streams___elabs PARAMS void extern void system__exception_table___elabb PARAMS void e
169. d there but will run into a circularity using the safer static model we have descri bed Of course any Ada compiler must be able to operate in a mode con sistent with the requirements of the Ada Reference M anual and in par ticular must have the capability of implementing the standard dynamic model of elaboration with run time checks In GNAT this standard mode can be achieved either by the use of the gnatE Switch on the compiler gcc or gnatmake command or by the use of the configuration pragma pragma Elaboration Checks RM Either approach will cause the unit affected to be compiled using the standard dynamic run time elaboration checks described in the Ada Reference Manual The static model is generally preferable since it is dearly safer to rely on compile and link time checks rather than run time checks However in the case of legacy code it may be difficult to meet the requirements of the static model This issue is further dis cussed in Section 11 9 What to Do If the Default Elaboration Behavior Fails page 200 Note that the static model provides a strict subset of the allowed behavior and programs of the Ada Reference M anual soif you do adhere to the static model and no circularities exist then you are assured that your program will work using the dynamic model 11 7 Elaboration Issues for Library Tasks In this section we examine special elaboration issues that arise for pro grams that declare library level t
170. de for Unix Platforms project Release is for Object_Dir use release for Exec_Dir use for Main use proc package Compiler is for Default_Switches Ada use 02 end Compiler end Release The name of the project defined by debug gpr iS Debug case insensi tive and analogously the project defined by release gpr iS Release For consistency the file should have the same name as the project and the project file s extension should be gpr These conventions are not required but a warning is issued if they are not followed If the current directory is temp then the command gnatmake P common debug gpr generates object and ALI files in common debug and the proc exe cutable also in common debug using the switch settings defined in the project file Likewise the command gnatmake P common release gpr generates object and ALI files in common release and the proc exe cutable in common using the switch settings from the project file Source Files If a project file does not explicitly specify a set of source directories or a set of source files then by default the project s source files are the Ada source files in the project file directory Thus pack ads pack adb and proc adb are the source files for both projects Specifying the Object Directory Several project properties are model ed by Ada styleattributes you define the property by supplying the
171. describes how to per form binding of Ada programs with gnatbind the GNAT binding utility Chapter 5 Linking Using gnatlink page 111 describes gnatlink a program that provides for linking using the GNAT run time li brary to construct a program gnatlink can also incorporate foreign language object units into the executable Chapter 6 The GNAT Make Program gnatmake page 115 de scribes gnatmake a utility that automatically determines the set of sources needed by an Ada compilation unit and executes the neces sary compilations binding and link Chapter 7 Renaming Files Using gnatchop page 125 describes gnat chop a utility that allows you to preprocess a file that contains Ada source code and split it into one or more new files one for each compilation unit Chapter 8 Configuration Pragmas page 131 describes the config uration pragmas handled by GNAT Chapter 9 Handling Arbitrary File Naming Conventions Using gnatname page 133 shows how to override the default GNAT file naming conventions either for an individual unit or globally Chapter 10 GNAT Project Manager page 137 describes how to use project files to organize large projects Chapter 11 Elaboration Order Handling in GNAT page 177 de scribes how GNAT helps you deal with elaboration order issues GNAT User s Guide for Unix Platforms Chapter 12 The Cross Referencing Tools gnatxref and gnatfind page 209 discusses gna
172. ding to Ada syntax e automatic completion of identifiers e automatic casing of identifiers keywords and attributes e insertion of statement templates e filling comment paragraphs like filling normal text For moreinformation please refer tothe online Glide documentation available in the Glide gt Help Menu 269 GNAT User s Guide for Unix Platforms 22 5 Converting Ada Files to html with gnathtml This Perl script allows Ada source files to be browsed using standard Web browsers For installation procedure see the section See Sec tion 22 6 Installing gnathtml page 271 Ada reserved keywords are highlighted in a bold font and Ada com ments in a blue font Unless your program was compiled with the gcc gnatx Switch to suppress the generation of cross referencing informa tion user defined variables and types will appear in a different color you will be able to click on any identifier and go to its declaration The command line is as follow perl gnathtml pl switches ada files You can pass it as many Ada files as you want gnathtml will generate an html file for every ada file and a global file called index htm This file is an index of every identifier defined in the files The available switches are the following ones 83 Only the subset on the Ada 83 keywords will be highlighted not the full Ada 95 keywords set cc color This option allows you to change the color used for comments The default value
173. directly defined by that project either implicitly by residing in the project file s directory or explicitly through any of the source related attributes described below More generally a project proj s sources are the immediate sources of proj together with the immediate sources unless overridden of any project on which proj depends either directly or indirectly 10 3 1 Basic Syntax As seen in the earlier examples project files have an Ada like syntax The minimal project file is project Empty is end Empty The identifier Empty is the name of the project This project name must be present after the reserved word end at the end of the project file followed by a semi colon Any name in a project file such as the project name or a variable name has the same syntax as an Ada identifier The reserved words of project files are the Ada reserved words plus extends external and project Notethat the only Ada reserved words currently used in project file syntax are e case e end e for 147 GNAT User s Guide for Unix Platforms e is e others e package e renames e type e use e when e with Comments in project files havethe same syntax as in Ada two consecu tives hyphens through the end of the line 10 3 2 Packages A project file may contain packages The name of a package must be one of the identifiers case insensitive from a predefined list and a package with a given name may only appear once in a project f
174. does such optimizations but still the easiest conceptual model is to think of there being one variable per subprogram 11 3 Controlling the Elaboration Order in Ada 95 In the previous section we discussed the rules in Ada 95 which ensure that Program Error is raised if an incorrect elaboration order is chosen This prevents erroneous executions but we need mechanisms to spec ify a correct execution and avoid the exception altogether To achieve this Ada 95 provides a number of features for controlling the order of elaboration We discuss these features in this section First there are several ways of indicating to the compiler that a gi ven unit has no elaboration problems packages that do not require a body In Ada 95 a library package that does not require a body does not permit a body This means that if we have a such a package as in package Definitions is generic type m is new integer package Subp is type a is array 1 10 of m type b is array 1 20 of m end Subp end Definitions A package that with s Definitions may Safely instantiate Definitions Subp because the compiler can determine that 181 GNAT User s Guide for Unix Platforms there definitely is no package body to worry about in this case pragma Pure Places sufficient restrictions on a unit to guarantee that no call to any subprogram in the unit can result in an elabora tion problem This means that the compiler does not need to worry a
175. ds on all its subunit body files e Theprevious tworules meant that for purposes of computing depen dencies and recompilation a body and all its subunits are treated as an indivisible whole These rules are applied transitively if unit A witn s unit B whose elaboration calls an inlined procedure in package c the object file for unit A will depend on the body of c in file c adb The set of dependent files described by these rules includes all the files on which the unit is semantically dependent as described in the Ada 95 Language Reference Manual However it is a superset of what the ARM describes because it includes generic inline and subunit dependencies An object file must be recreated by recompiling the corresponding source file if any of the source files on which it depends are modified For example if the make utility is used to control compilation the rule for an Ada object file must mention all the source files on which the object file depends according to the above definition The de termination of the necessary recompilations is done automatically when one uses gnatmake 25 GNAT User s Guide for Unix Platforms 2 8 The Ada Library Information Files Each compilation actually generates two output files The first of these is the normal object file that has a o extension The second is a text file containing full dependency information It has the same name as the source file but an a1i extension Thi
176. dure table for zero cost exception handling omitted in longjmp setjump mode GNAT User s Guide for Unix Platforms SDP Table Build ST Address 23 EA Address 23 Call Set Globals to record various information for this partition The values are derived by the binder from information stored in the ali files by the compiler Set_Globals Main_Priority gt 1 Priority of main program 1 if no pragma Priority used Time_Slice_Value gt 1 Time slice from Time_Slice pragma 1 if none used WC_Encoding gt b Wide Character encoding used default is brackets Locking_Policy gt Locking Policy used default of space means not specified otherwise it is the first character of the policy name Queuing Policy a mnie Queuing Policy used default of space means not specified otherwise it is the first character of the policy name Task_Dispatching Policy D P Task_Dispatching_Policy used default of space means not specified otherwise first character of the policy name Adafinal gt System Null_Address Address of Adafinal routine not used anymore Unreserve_All_Interrupts gt 0 Set true if pragma Unreserve_All_Interrupts was used Exception_Tracebacks gt 0 Indicates if exception tracebacks are enabled Elab_Final_Code 1 23 May 2002 Chapter 4 Binding Using gnatbind Now we have the elaboration calls for
177. e E ach of the source directories must exist and be readable 10 4 4 Source File Names In a project that contains source files their names may be specified by the attributes Source Files a string list or source List File a string Source file names never include any directory information If the attribute source Files is given an explicit value then each element of the list is a source file name 156 5 28 May 2002 Chapter 10 GNAT Project Manager for Source_Files use main adb for Source Files use main adb packi ads pack2 adb If the attribute source Files is not given an explicit value but the attribute Source List File is given a string value then the source file names are contained in the text file whose path name absolute or relative to the directory of the project file is the value of the attribute Source List File Each linein the file that is not empty or is not a comment contains a source file name A comment line starts with two hyphens for Source List File use source list txt By default if neither the attribute source Files nor the attribute Source List File is given an explicit value then each file in the source directories that conforms to the project s naming scheme see Section 10 10 N aming Schemes page 162 is an immediate source of the project A warning is issued if both a
178. e mentations for a common interface in Ada terms multiple versions of GNAT User s Guide for Unix Platforms a package body for the same specification For example one implemen tation might be safe for use in tasking programs while another might only be used in sequential applications This can be modeled in GNAT using the concept of project extension If one project the child extends another project the parent then by default all source files of the par ent project are inherited by the child but the child project can override any of the parent s source files with new versions and can also add new files This facility is the project analog of extension in Object Oriented Programming Project hierarchies are permitted a child project may be the parent of yet another project and a project that inherits one project can also import other projects As an example suppose that directory seq contains the project file seq_proj gpr and the source files pack ads pack adb and proc adb seq pack ads pack adb proc adb seq_proj gpr Note that the project file can simply be empty that is no attribute or package is defined project Seq_Proj is end Seq_Proj implying that its source files are all the Ada source files in the project directory Suppose we want to supply an alternate version of pack adb in directory tasking but use the existing versions of pack ads and proc adb We c
179. e All other letters must be lowercase 5q4 ___ 23 May 2002 Chapter 3 Compiling Using gcc b blanks not allowed at statement end Ifthe letter b appears in thestring after gnaty then trailing blanks are not allowed at the end of statements The purpose of this rule together with h no horizontal tabs is to enforce a canonical format for the use of blanks to separate source tokens c check comments If the letter c appears in the string after gnaty then com ments must meet the following set of rules The that starts the column must either start in col umn one or else at least one blank must precede this sequence Comments that follow other tokens on a line must have at least one blank following the at the start of the comment Full line comments must have two blanks following the that starts the comment with the following excep tions A line consisting only of the characters possibly preceded by blanks is permitted A comment starting with x where x is a special character is permitted This alows proper processing of the output generated by specialized tools induding gnatprep Where is used and the SPARK annnota tion language where is used For the purposes of this rule a special character is defined as being in one of the ASCII ranges 16 21 16 2F or 16 3A 164 B3F A line consisting entirely of minus signs possibly pre ceded by blanks is permitted This allows the construc t
180. e Title Page means for a printed book the title page itself plus such following pages as are needed to hold legibly the material this License requires to appear in thetitle page For works in formats which do not have any title page as such Title Page means the text near the most prominent appearance of the work s title preceding the beginning of the body of the text 334 28 May 2002 Appendix A GNU Free Documentation License 2 VERBATIM COPYING You may copy and distribute the Document in any medium either commercially or noncommercially provided that this License the copy right notices and the license notice saying this License applies to the Document are reproduced in all copies and that you add no other con ditions whatsoever to those of this License You may not use technical measures to obstruct or control the reading or further copying of the copies you make or distribute However you may accept compensation in exchange for copies 1f you distribute a large enough number of copies you must also follow the conditions in section 3 You may also lend copies under the same conditions stated above and you may publicly display copies 3 COPYING IN QUANTITY If you publish printed copies of the Document numbering more than 100 and the Document s license notice requires Cover Texts you must enclose th
181. e including infor mation on line numbers and on declared types and variables This information is separate from the generated code It makes the object files considerably larger but it does not add to the size of the actual executable that will be loaded into memory and has no impact on run time performance The generation of debug information is triggered by the use of the g switch in the gcc or gnatmake command used to carry out the compilations It is important to emphasize that the use of these options does not change the generated code The debugging information is written in standard system formats that are used by many tools induding debuggers and profilers The format of the information is typically designed to describe C types and semantics but GNAT implements a translation scheme which allows 273 GNAT User s Guide for Unix Platforms full details about Ada types and variables to be encoded into these stan dard C formats Details of this encoding scheme may be found in the file exp_dbug ads in the GNAT source distribution However the de tails of this encoding are in general of no interest to a user since GDB automatically performs the necessary decoding When a program is bound and linked the debugging information is collected from the object files and stored in the executable image of the program Again this process significantly increases the size of the generated executable file but it does not increase the size o
182. e information in this file along with the list of non Ada objects and linker options constructs a Unix linker command file to create the executable The arguments following mainprog ali are passed to the linker un interpreted They typically indude the names of object files for units written in other languages than Ada and any library references required to resolve references in any of these foreign language units or in pragma Import Statements in any Ada units linker options is an optional list of linker specific switches The default linker called by gnatlink is gcc which in turn calls the appro priate system linker usually called 14 Standard options for the linker such as imy 1ib Or Ldir can be added as is For options that are not recognized by gcc as linker options the gcc switches xiinker Or w1 Shall be used Refer to the GCC documentation for details Here is an example showing how to generate a linker map assuming that the underlying linker is GNU Id gnatlink my prog Wl Map MAPFILE Using linker options it is possible to set the program stack and heap size See see Section 5 3 Setting Stack Size from gnatlink page 113 and see Section 5 4 Setting Heap Size from gnatlink page 114 gnatlink determines the list of objects required by the Ada program and prepends them to the list of objects passed to the linker gnat link also gathers any arguments set by the use of pragma Linker Options and adds them to the list
183. e T is array 1 1000 of Integer type Ptr is access T procedure Free is new Unchecked_Deallocation T Ptr A Ptr procedure My_Alloc is begin A new T end My_Alloc procedure My_DeAlloc is B Ptr A begin Free B end My_DeAlloc begin My_Alloc for I in 1 5 loop for J in I 5 loop My Alloc end loop My Dealloc end loop end The program needs to be compiled with debugging option gnatmake g test gm gnatmem is invoked simply with gnatmem test gm which produces the following output Global information Total number of allocations Total number of deallocations Final Water Mark non freed mem 250 18 5 53 00 Kilobytes 23 May 2002 Chapter 18 Finding Memory Problems with gnatmem High Water Mark 56 90 Kilobytes Allocation Root 1 Number of non freed allocations i 11 Final Water Mark non freed mem 42 97 Kilobytes High Water Mark 46 88 Kilobytes Backtrace test_gm adb 11 test_gm my_alloc Allocation Root 2 Number of non freed allocations 1 Final Water Mark non freed mem 10 02 Kilobytes High Water Mark 10 02 Kilobytes Backtrace s secsta adb 81 system secondary_stack ss_init Allocation Root 3 Number of non freed allocations 1 Final Water Mark non freed mem 12 Bytes High Water Mark 12 Bytes Backtrace s secsta adb 181 system secondary_stack ss_init Note that the GNAT run time contains itself a certain numbe
184. e all run time checks enabled except overflow and elaboration checks These options are suitable for most program development purposes This chapter describes how you can modify these choices and also provides some guidelines on debugging optimized code 25 1 Controlling Run Time Checks By default GNAT generates all run time checks except arithmetic over flow checking for integer operations and checks for access before elab oration on subprogram calls The latter are not required in default mode because all necessary checking is done at compile time Two gnat switches gnatp and gnato allow this default to be modified See Section 3 2 5 Run Time Checks page 60 Our experience is that the default is suitable for most development purposes We treat integer overflow specially because these are quite expensive and in our experience are not as important as other run time checks in the development process Note that division by zero is not considered an overflow check and divide by zero checks are generated where required by default Elaboration checks are off by default and also not needed by default since GNAT uses a static elaboration analysis approach that avoids the need for run time checking This manual contains a full chapter dis cussing the issue of elaboration checks and if the default is not satisfac tory for your use you should read this chapter Note that the setting of the switches controls the default setting of
185. e copies in covers that carry clearly and legibly all these Cover Texts Front Cover Texts on the front cover and Back Cover Texts on the back cover Both covers must also dearly and legibly identify you as the publisher of these copies The front cover must present the full title with all words of the title equally prominent and visible You may add other material on the covers in addition Copying with changes limited to the covers as long as they preserve the title of the Document and satisfy these conditions can be treated as verbatim copying in other respects If the required texts for either cover are too voluminous to fit legibly you should put the first ones listed as many as fit reasonably on the actual cover and continue the rest onto adjacent pages If you publish or distribute Opaque copies of the Document numbering more than 100 you must either include a machine readable Transpar ent copy along with each Opaque copy or state in or with each Opaque copy a publicly accessible computer network location containing a com plete Transparent copy of the Document free of added material which the general network using public has access to download anonymously at no charge using public standard network protocols If you use the latter option you must take reasonably prudent steps when you begin distribution of Opaque copies in quantity to ensure that this Transpar ent copy will remain thus accessible at the stated location until at
186. e desired order 208 23May 2002 Chapter 12 The Cross Referencing Tools gnatxref and gnat find 12 The Cross Referencing Tools gnatxref and gnatfind Thecompiler generates cross referencing information unless you set the gnatx switch which are saved in the ali files This information indicates where in the source each entity is dedared and referenced Note that entities in package Standard are not included but entities in all other predefined units are included in the output Before using any of these two tools you need to compile successfully your application so that GNAT gets a chance to generate the cross referencing information The two tools gnatxref and gnatfind take advantage of this infor mation to provide the user with the capability to easily locate the dec laration and references to an entity These tools are quite similar the difference being that gnat find is intended for locating definitions and or references to a specified entity or entities whereas gnatxref is oriented to generating a full report of all cross references To use these tools you must not compile your application using the gnatx switch on the gnatmake command line See I nfo file gnat_ug node The GNAT Make Program gnatmake Otherwise cross referencing information will not be generated 12 1 gnatxref Swit
187. e file in any directory using an absolute or relative path specification containing the directory information gcc is actually a driver program that looks at the extensions of the file arguments and loads the appropriate compiler For example the GNU 37 GNAT User s Guide for Unix Platforms C compiler is cc1 and the Ada compiler is gnat 1 These programs are in directories known to the driver program in some configurations via environment variables you set but need not be in your path The gcc driver also calls the assembler and any other utilities needed to complete the generation of the required object files It is possible to supply several file names on the same gcc command This causes gcc to call the appropriate compiler for each file For exam ple the following command lists three separate files to be compiled gcc c x adb y adb z c calls gnat 1 the Ada compiler twice to compile x adb and y adb and cc1 the C compiler once to compile z c The compiler generates three object files x o y o and z o and the two ALI files x ali and y ali from the Ada compilations Any switches apply to all the files listed except for gnatx switches which apply only to Ada compilations 3 2 Switches for gcc The gcc command accepts switches that control the compilation process These switches are fully described in this section First we briefly list all the switches in alphabetical order then
188. e for Unix Platforms e Help For this introductory example you will need to create a new Ada source file First select the Files menu This will pop open a menu with around a dozen or so items To create a file select the open file choice Depending on the platform you may see a pop up window where you can browse to an appropriate directory and then enter the file name or else simply see a line at the bottom of the Glide window where you can likewise enter the file name Note that in Glide when you attempt to open a non existent file the effect is to create a file with that name For this example enter he11o adb as the name of the file A new buffer will now appear occupying the entire Glide window with the file name at the top The menu selections are slightly different from the ones you saw on the opening screen there is an Entities item and in place of Glide there is now an Ada item Glide uses the file extension to identify the source language so adb indicates an Ada source file You will enter some of the source program lines explicitly and use the syntax oriented template mechanism to enter other lines First type the following text with Ada Text I0 use Ada Text IO procedure Hello is begin Observe that Glide uses different colors to distinguish reserved words from identifiers Also after the procedure Hello is line the cursor is automatically indented in anticipation of dedarations When you enter begin Glide r
189. e guarantee its consistency If you would like to use some existing set of files as gnatelim output you must make sure that the set of files is complete and consistent You can use the m switch to check if there are missed tree files Note that gnate1im needs neither object nor ALI files 21 5 Running gnatelim gnatelim has the following command line interface gnatelim options name name Should be a full expanded Ada name of a main subprogram of a program partition gnatelim options q Quiet mode by default gnatelim generates to the standard error stream a trace of the source file names of the compi lation units being processed This option turns this trace off v Verbose mode gnatelim version information is printed as Ada comments to the standard output stream a Also look for subprograms from the GNAT run time that can be eliminated m Check if any tree files are missing for an accurate result T dir When looking for tree files also look in directory dir b bind file Specifies bind file as the bind file to process If not set the name of the bind file is computed from the full expanded Ada name of a main subprogram dx Activate internal debugging switches x is a letter or digit or string of letters or digits which specifies the type of de bugging mode desired Normally these are used only for internal development or system debugging purposes You can find full documentation for these switches in the body
190. e name finally followed by a semi colon Most of the packages have an attribute Default Switches This attribute is an associative array and its value is a string list The index of the associative array is the name of a programming language case insensitive This attribute indicates the switch or switches to be used with the corresponding tool Some packages also have another attribute switches an associative array whose value is a string list The index is the name of a source 160 Q P o mtczv Ur o vr Ur u 8 May 2002 Chapter 10 GNAT Project Manager file This attribute indicates the switch or switches to be used by the corresponding tool when dealing with this specific file Further information on these switch related attributes is found in Section 10 13 1 1 Switches and Project Files page 166 A package may be declared as a renaming of another package e g from the project file for an imported project with global apex gpr project Example is package Naming renames Apex Naming end Example Packages that are renamed in other project files often come from project files that have no sources they are just used as templates Any modi fication in the template will be reflected automatically in all the project files that rename a package from the template In addition to the tool oriented packages you can also declare a pack age named Naming to establish specialized source
191. e set of Eliminate pragmas is specific to each pro gram It is not recommended to merge sets of Eliminate pragmas cre ated for different programs in one gnat adc file 21 8 Summary of the gnatelim Usage Cycle Here is a quick summary of the steps to be taken in order to reduce the sizeof your executables with gnatelim You may useother GNAT options to control the optimization level to produce the debugging information to set search path etc 1 Produce a bind file and a set of tree files 264 CCC 28May 2002 Chapter 21 Reducing the Size of Ada Executables with gnatelim gnatmake c Main_Prog gnatbind main_prog gnatmake f c gnatc gnatt Main_Prog 2 Generate a list of Eliminate pragmas gnatelim Main_Prog gt gt gnat adc 3 Recompile the application gnatmake f Main_Prog 265 GNAT User s Guide for Unix Platforms 2 v r r r ir 23May 2002 Chapter 22 Other Utility Programs 22 Other Utility Programs This chapter discusses some other utility programs available in the Ada environment 22 1 Using Other Utility Programs with GNAT The object files generated by GNAT are in standard system format and in particular the debugging information uses this format This means programs generated by GNAT can be used with existing utilities that depend on these formats In general any utility program that works with C will also often work with Ada programs gen
192. e the compiler command that will be used by gnatlink Will be oo c x y If several GCC compiler _ name are used only the last compiler name is taken into account However all the additional switches are also taken into account Thus GCC foo x y GCC bar z t is equivalent to Gcc bar x y z t LINK name name is the name of the linker to be invoked This is es pecially useful in mixed language programs since languages such as c require their own linker to be used When this switch is omitted the default name for the linker is gcc When this switch is used the specified linker is called instead of gcc with exactly the same parameters that would have been passed to gcc soif the desired linker requires differ ent parameters it is necessary to use a wrapper script that massages the parameters before invoking the real linker It may be useful to control the exact invocation by using the verbose switch 5 3 Setting Stack Size from gnatlink It is possible to specify the program stack size from gnat1ink Assuming that the underlying linker is GNU Id there is two ways to do so e Using Xlinker linker option gnatlink hello Xlinker stack 0x10000 0x1000 This set the stack reserve sizeto 0x10000 bytes andthe stack commit size to 0x1000 bytes e using w1 linker option gnatlink hello Wl stack 0x1000000 113 GNAT User s Guide for Unix Platforms This set the stack reserve size to 0x1
193. e_Dirs use project Source_Dirs amp units for Source_Dirs use project Source_Dirs amp test drivers end Prj Inthe first attribute declaration initially the attribute source Dirs has the default value an empty string list After this dedaration source _ Dirs S a string list of one element units After the second attribute declaration Source Dirs is a string list of two elements units and test drivers 153 GNAT User s Guide for Unix Platforms Note this example is for illustration only In practice the project file would contain only one attribute declaration for Source Dirs use units test drivers 10 3 7 Associative Array Attributes Some attributes are defined as associative arrays An associative array may be regarded as a function that takes a string as a parameter and delivers a string or string list value as its result Here are some examples of associative array attribute declarations for Implementation main use Main ada for Switches main ada use v gnatv for Switches main ada use Builder Switches main ada amp g Like untyped variables and simple attributes associative array at tributes may be declared several times Each dedaration supplies a new value for the attribute replacing the previous setting 10 3 8 case Constructions A case construction is used in a project file to effect conditional behavior Here is a typical example project MyProj is
194. eans that any arbitrary part of the program may be executed as part of the elaboration code It is even possible to write a program which does all its work at elaboration time with a null main program although stylistically this would usually be considered an inappropriate way to structure a program An important concern arises in the context of elaboration code we have to be sure that it is executed in an appropriate order What we have is a series of elaboration code sections potentially one section for each unit in the program It is important that these execute in the correct order Correctness here means that taking the above example of the declaration of sqrt Half if some other piece of elaboration code references Sqrt Half then it must run after the section of elaboration code that contains the declaration of sqrt Half 177 GNAT User s Guide for Unix Platforms There would never be any order of elaboration problem if we made a rule that whenever you with a unit you must elaborate both the spec and body of that unit before elaborating the unit doing the with ing with Unit 1 package Unit 2 is would requirethat both the body and spec of unit 1 be elaborated before the spec of unit 2 However a rule like that would be far too restrictive In particular it would make it impossible to have routines in separate packages that were mutually recursive You might think that a dever enough compiler could look at the actua
195. earched is the same as for gnatmake Do not look for sources in the system default directory Do not look for library files in the system default directory path Specifies the default location of the runtime library Same meaning as the equivalent gnatmake flag see Section 6 2 Switches for gnatmake page 116 If this switch is set then gnatfind will output the parent type reference for each matching derived types By default gnat find accept the simple regular expression set for pattern If this switch is set then the pattern will be considered as full Unix style regular expression If this switch is set the output file names will be preceded by their directory if the file was found in the search path If this switch is not set the directory will not be printed If this switch is set information is output only for library level entities ignoring local entities The use of this switch may accelerate gnat find and gnatxref Equivalent to aoDIR aIDIR 23 May 2002 Chapter 12 The Cross Referencing Tools gnatxref and gnat find pFILE Specify a project file see Section 10 1 1 Project Files page 137 to use By default gnatxref and gnatfind will try to locate a project filein the current directory If a project fileis either specified or found by the tools then the content of the source directory and object directory lines are added as if they had been specified respectively by at
196. eased under this License The Cover Texts are certain short passages of text that are listed as Front Cover Texts or Back Cover Texts in the notice that says that the Document is released under this License A Transparent copy of the Document means a machine readable copy represented in a format whose specification is available to the general public whose contents can be viewed and edited directly and straightforwardly with generic text editors or for images composed of pixels generic paint programs or for drawings some widely available drawing editor and that is suitable for input to text formatters or for automatic translation to a variety of formats suitable for input to text formatters A copy made in an otherwise Transparent file format whose markup has been designed to thwart or discourage subsequent modifi cation by readers is not Transparent A copy that is not Transparent is called Opaque Examples of suitable formats for Transparent copies include plain ASCII without markup Texinfo input format LaTeX input format SGML or XML usinga publidy available DTD and standard conformi ng simpleHTML designed for human modification Opaqueformats indude PostScript PDF proprietary formats that can be read and edited only by proprietary word processors SGML or XML for which the DTD and or processing tools are not generally available and the machine generated HTML produced by some word processors for output purposes only Th
197. eceding the compilation unit from the source of the library unit dec laration into the body stub hg Put a sample comment header into the body stub IDIR I These switches have the same meaning as in calls to gcc They define the source search path in the call to gcc issued by gnatstub to compile an argument source file 259 GNAT User s Guide for Unix Platforms in ln 260 nis a decimal natural number Set the indentation level in the generated body sampleton i0 means noindentation the default indentation is 3 Do not removethe tree file i e the snapshot of the compiler internal structures used by gnat stub after creating the body stub nis a decimal positive number Set the maxi mumlinelength in the body stub to n the default is 78 Quiet mode do not generate a confirmation when a body is successfully created or a message when a body is not required for an argument unit Reuse the tree file if it exists instead of creating it in stead of creating thetree filefor the library unit dedaration gnatstub tries to find it in the current directory and use it for creating a body If the tree file is not found no body is created x alsoimplies k whether or not k is set explicitly Overwrite the existing tree file if the current directory al ready contains the file which according to the GNAT file name rules should be considered as a tree file for the argu ment source file gnatstub will refuse t
198. ecognizes that there are no dedarations and thus places begin flush left But after the begin line the cursor is again indented where the statement s will be placed The main part of the program will bea for loop Instead of entering the text explicitly however use a statement template Select the ada item on the top menu bar move the mouse to the statements item and you will see a large selection of alternatives Choose for loop You will be prompted at the bottom of the buffer for a loop name simply press the key since a loop name is not needed You should see the beginning of a for loop appear in the source program window You will now be prompted for the name of the loop variable enter a line with the identifier ina lower case Note that by default Glide capitalizes the name you can override such behavior if you wish although this is outside the scope of this introduction Next Glide prompts you for the loop range enter a linecontainingi 5 and you will see this also appear in the source program together with the remaining elements of the for loop syntax Next enter the statement with an intentional error a missing semi colon that will form the body of the loop 10 28 May 2002 Chapter 1 Getting Started with GNAT Put_Line Hello World amp Integer Image 1 Finally type end Hello as the last line in the
199. ect Files gt One Window If a window is occupied by one buffer and you want tosplit the window to bring up a second buffer perform the following steps e Select Files gt Split Window this will produce two windows each of which holds the original buffer these are not copies but rather different views of the same buffer contents e With the focus in one of the windows select the desired buffer from the Bu fers menu To exit from Glide choose Files Exit GNAT User s Guide for Unix Platforms 14 23 May 2002 Chapter 2 The GNAT Compilation Model 2 The GNAT Compilation Model This chapter describes the compilation model used by GNAT Although similar to that used by other languages such as C and C this model is substantially different from the traditional Ada compilation models which are based on a library The model is initially described without reference to the library based model If you have not previously used an Ada compiler you need only read the first part of this chapter The last section describes and discusses the differences between the GNAT model and the traditional Ada compiler models If you have used other Ada compilers this section will help you to understand those differences and the advantages of the GNAT model 2 1 Source Representation Ada source programs are represented in standard text files using Latin 1 codi
200. ect of this setting is to write long format error messages to stdout the standard output file The same program compiled with the gnatv switch would generate 3 funcion X Q Integer gt gt gt Incorrect spelling of keyword function 4 return Integer l gt gt gt should be is The vertical bar indicates the location of the error and the gt gt gt prefix can be used to search for error messages When this switch is used the only source lines output are those with errors gnatl The 1 stands for list This switch causes a full listing of the fileto be generated The output might look as follows procedure E is V Integer funcion X Q Integer l gt gt gt Incorrect spelling of keyword function return Integer l gt gt gt should be is begin return Q Q end begin end E When you specify the gnatv or gnat1 switches and stan dard output is redirected a brief summary is written to stderr standard error giving the number of error mes sages and warning messages generated gnatU This switch forces all error messages to be preceded by the unique string error This means that error messages take GNAT User s Guide for Unix Platforms gnatb gnatmn e adb 3 e adb 5 a few more characters in space but allows easy searching for and identification of error messages The stands for brief This switch causes GNAT to generate the brief forma
201. ed to provide the Ada component of the program The output is written to stdout This list includes the files explicitly supplied and referenced by the user as well as implicitly ref erenced run time unit files The latter are omitted if the corresponding units reside in shared libraries The directory names for the run time units depend on the system configu ration Set name of output file to file instead of the normal b mainprog adb default Note that file denote the Ada binder generated body filename In C mode you would nor mally give file an extension of c because it will be a C source program Note that if this option is used then linking must be done manually It is not possible to use gnatlink in this case since it cannot locate the binder file Generate list of pragma Rerstrictions that could be applied to the current unit This is useful for code audit purposes and also may be used to improve code generation in some cases 23 May 2002 Chapter 4 Binding Using gnatbind 4 7 Binding with Non Ada Main Programs In our description so far we have assumed that the main program is in Ada and that the task of the binder is to generate a corresponding function main that invokes this Ada main program GNAT also supports the building of executable programs where the main program is not in Ada but some of the called routines are written in Ada and compiled usingGNAT see Section 2 10 Mixed LanguageProgramming p
202. ed prefixes so if this debugger is used the encoding is largely hidden from the user of the compiler gnatR 0 1 2 31 s gnatx 70 This switch controls output from the compiler of a listing showing representation information for dedared types and objects For gnatRo no information is output equivalent to omitting the gnatr switch For gnatri which is the default so gnatR with no parameter has the same effect size and alignment information is listed for dedared array and record types For anatR2 size and alignment informa tion is listed for all expression information for values that are computed at run time for variant records These symbolic ex pressions have a mostly obvious format with n being used to represent the value of the n th discriminant See source files repinfo ads adb in the cnar sources for full detalis on the format of gnatR3 output If the switch is followed by an S e g gnatR2s then the output is to a file with the name ile rep Wherefileis the name of the corresponding source file Normally the compiler generates full cross referencing in formation in the az file This information is used by a 23 May 2002 Chapter 3 Compiling Using gcc number of tools induding gnatfind and gnatxref The gnatx switch suppresses this information This saves some Space and may slightly speed up compilation but means that these tools cannot be used 3 2 16 Units to Sources Mapping Files
203. ed variable In the example Unsigned 32 Asm Output m Flags the m memory constraint tells the compiler that thevariable Flags should be stored in a memory variable thus preventing the optimizer from keeping it in a register In contrast Unsigned 32 Asm Output r Flags uses the x register constraint telling the compiler to store the variablein a register If the constraint is preceded by the equal character it tells the compiler that the variable will be used to store data into it In the Get_Flags example we used the g global constraint al lowing the optimizer to choose whatever it deems best There area fairly large number of constraints but the ones that are most useful for the Intel x86 processor are the following 297 GNAT User s Guide for Unix Platforms output constraint global i e can be stored anywhere m in memory a constant a use eax b use ebx c use ecx d use edx S use esi D use edi r use one of eax ebx ecx or edx q use one of eax ebx ecx edx esi or edi The full set of constraints is described in the gcc and as documen tation note that it is possible to combine certain constraints in one constraint string You specify the association of an output variable with an assembler operand through the sn notation where n is a non negative integer Thus in Asm pushfl amp LF amp HT amp push flags on stack popl eax amp LF amp HT amp load eax wit
204. ed_8 end record for Unsigned_Register use record Li at 0 range O 7 H1 at O range 8 15 L2 at O range 16 23 H2 at O range 24 31 end record for Unsigned_Register Size use 32 31633 May 2002 Chapter 24 Inline Assembler Intel_Processor constant String 1 12 GenuineIntel indicates an Intel manufactured processor a register type to hold the processor signature type Processor_Signature is record Stepping Natural range 0 15 Model Natural range O 15 Family Natural range O 15 Processor Type Natural range 0 3 Reserved Natural range 0 262143 end record for Processor Signature use record Stepping at O range 0 3 Model at O range 4 T Family at O range 8 11 Processor_Type at O range 12 13 Reserved at O range 14 31 end record for Processor_Signature Size use 32 a processor register to hold the processor feature flags type Processor_Features is record FPU Boolean floating point unit on chip VME Boolean virtual mode extension DE Boolean debugging extension PSE Boolean page size extension TSC Boolean time stamp counter 317 GNAT User s Guide for Unix Platforms 318 MSR PAE MCE CX8 APIC Res_1 SEP MTRR PGE MCA CMOV PAT Res 2 MMX FXSR Res 3 Boolean Boolean Boolean Boolean Boolean Boolean Boolean Boolean Boolean Boolea
205. elaborated before proc body info reason pragma Elaborate in unit proc body In this case we have a cycle that the binder cannot break On the one hand thereis an explicit pragma Elaboratein proc for pack This means that the body of pack must be elaborated before the body of proc On the other hand there is elaboration code in pack that calls a subprogram in proc This means that for maximum safety there should really be a pragma Elaborate All in pack for proc which would requirethat the body of proc be elaborated before the body of pack Clearly both requirements cannot be satisfied Faced with a circularity of this kind you have three different options Fix the program Themost desirable option from the point of view of long term maintenance is to rearrange the program so that the elab oration problems are avoided One useful technique is to place the elaboration code into separate child packages An other is to move some of the initialization code to explicitly called subprograms where the program controls the order of initialization explicitly Although this is the most desirable option it may be impractical and involve too much modifica tion especially in the case of complex legacy code 200 May 2002 Chapter 11 Elaboration Order Handling in GNAT Perform dynamic checks If the compilations are done
206. em__stack_checkingB 0x476457A0 system__stack_checkingS 0x5299FCED system__tracebackB 0x2971EBDE system__tracebacksS 0x2E9C3122 ada__streamsS 0x7C25DE96 ada__tagsB Ox39ADFFA2 ada__tagsS 0x769A0464 system__string_opsB Ox5EB646AB system__string_opss 0x63CED018 interfacesS 0x0357E00A interfaces__c_streamsB 0x3784FB72 interfaces__c_streamsS 0x2E723019 system__file_ioB 0x623358EA system__file_ioS 0x31F873E6 ada__finalizationB 0x6843F68A ada__finalizationS 0x63305874 system__finalization_rootB 0x31E56CE1 GNAT User s Guide for Unix Platforms unsigned system__finalization_rootS 0x23169EF3 unsigned system__finalization_implementationB Ox6CCBATOE unsigned system__finalization_implementationS 0x604AA587 unsigned system__string_ops_concat_3B 0x572E3F58 unsigned system string ops concat 3S 0x01F57876 unsigned system stream attributesB 0x1D4F93E8 Ox30B2EC3D unsigned ada io exceptionsS8 0x34054F96 unsigned system stream attributesS unsigned system unsigned typesS 0x7B9E7FE3 unsigned system file control blockS8 Ox2FF8764A8 unsigned ada finalization list controllerB 0x57606344 unsigned ada finalization list controllerS8 0x5D851835 BEGIN ELABORATION ORDER ada spec gnat spec gnat heap sort a spec gnat htable spec gnat htable body interfaces spec system spec system parameters spec system standard library spec ada exceptions spec
207. en the only modifications to a source file consist in adding removing comments empty lines spaces or tabs This means that if you have changed the comments in a source file or have simply reformatted it using this switch will tell gnatmake not to recompile files that depend on it provided other sources on which these files depend have un dergone no semantic modifications M Check if all objects are up to date If they are output the object dependences to stdout in a form that can be directly exploited in a Makefile By default each source file is pre fixed with its relative or absolute directory name This name is whatever you specified in the various ar and I switches If you use gnatmake M q see below only the source file names without relative paths are output If you just specify the m switch dependencies of the GNAT inter nal system files are omitted Thisistypically what you want If you also specify the a switch dependencies of the GNAT internal files are also listed Note that dependencies of the objects in external Ada libraries see switch aLdir in the following list are never reported n Don t compile bind or link Checks if all objects are up to date If they are not the full name of the first file that needs to be recompiled is printed Repeated use of this option fol lowed by compiling the indicated source file will eventually result in recompiling all required units o exec name Outpu
208. entire application including run time files using special configuration pragma settings such as a non standard Float Representation pragma By default gnatmake a compiles all GNAT internal files with gcc c gnatpg rather than gcc c Bind only Can be combined with c to do compilation and binding but no link Can be combined with 1 to do binding and linking When not combined with c all the units in the closure of the main program must have been previously compiled and must be up to date The root unit specified by file name may be given without extension with the source extension or if no GNAT Project File is specified with the ALI file extension Compile only Do not perform binding except when b is also specified Do not perform linking except if both b and 1 are also specified If the root unit specified by file name is not a main unit this is the default Otherwise gnatmake will attempt binding and linking unless all objects are up to date and the executable is more recent than the objects Use a mapping file A mapping file is a way to commu nicate to the compiler two mappings from unit names to file names without any directory information and from file namesto path names with full directory information These mappings are used by the compiler to short circuit the path search When gnatmake is invoked with this switch it will create a mapping file initially populated by the project man ager if P is used other
209. ents ada replaced by a gnat replaced by g 222 T 28 May 2002 Chapter 13 File Name Krunching Using gnatkr interfaces replaced by i system replaced by s These system files have a hyphen in the second character position That is why normal user files replace such a character with a tilde to avoid confusion with system file names As an example of this special rule consider ada strings wide fixed adb which gets krunched as follows ada strings wide fixed 22 a strings wide fixed 18 a string wide fixed 17 a strin wide fixed 16 a stri wide fixed 15 a stri wide fixe 14 a str wide fixe 13 a str wid fixe 12 a str wid fix 11 a st wid fix 10 a st wi fix 9 a st wi fi 8 Final file name a stwifi adb Of course no file shortening algorithm can guarantee uniqueness over all possible unit names and if file name krunching is used then it is your responsibility to ensure that no name clashes occur Theutility program gnatkr is supplied for conveniently determining the krunched name of a file 13 4 Examples of gnatkr Usage gnatkr gnatkr gnatkr gnatkr gnatkr very_long_unit_name ads gt velounna ads grandparent parent child ads gt grparchi ads Grandparent Parent Child gt grparchi very_long_unit_name ads count 6 gt vlunna ads very_long_unit_name ads count 0 gt very_long_unit_name ads 223 GNAT User s Guide for Unix Pla
210. equivalent of an Ada attribute definition dause in the project file A project s object directory is such a property the corresponding attribute is object Dir and its value is a string expression A directory may be specified either as absolute or as relative in the latter case it is relative to the project file directory Thus the compiler s output is directed to common debug for the Debug project and to common release for the Release project If object pirisnot specified then the default is the project file directory 140 28 May 2002 Chapter 10 GNAT Project Manager Specifying the Exec Directory A project s exec directory is another property the corresponding at tribute is Exec Dir and its value is also a string expression either specified as relative or absolute If Exec Dir is not specified then the default is the object directory which may also be the project file direc tory if attribute object Dir is not specified Thus the executable is placed in common debug for the Debug project attribute Exec Dir not specified and in common for the Release project Project File Packages A GNAT tool integrated with the Project Manager is modeled by a cor responding package in the project file The Debug project defines the packages Builder for gnatmake and compiler the Release project defi
211. er Pack2 Pure 11 Elab call 1 begin declare pragma Suppress Elaboration Check Pack2 F20 1 pragma Suppress Elaboration Check 2 begin X1 Pack2 F2 1 Elab call 2 end end Pack1 with Pack1 package body Pack2 is function F2 return Integer is begin return Pack1 F1 end F2 function Pure x integer return integer is begin return x 3 3 x 202 23May202 Chapter 11 Elaboration Order Handling in GNAT end end Pack2 with Pack1 Ada Text 10 procedure Proc3 is begin Ada Text_I0 Put_Line Pack1 X1 Img 101 end Proc3 In the absence of any pragmas an attempt to bind this pro gram produces the following diagnostics error elaboration circularity detected info info info info info info info info info info info info pack1 body must be elaborated before pack1 body reason Elaborate_All probably needed in unit pack1 body recompile packi body with gnatwl for full details pack1 body must be elaborated along with its spec pack1 spec which is withed by pack2 body which must be elaborated along with its spec pack2 spec which is withed by pack1 body Thesources of the circularity are the two calls to Pack2 Pure and Pack2 F2 in the body of Packi We can see that the call to F2 is safe even t
212. erated by GNAT This includes software utilities such as gprof a profiling program gdb the FSF debugger and utilities such as Purify 22 2 The gnatpsta Utility Program Many of the definitions in package Standard are implementation dependent However the source of this package does not exist as an Ada source file so these values cannot be determined by inspecting the source They can be determined by examining in detail the coding of estand adb which creates the image of Standard in the compiler but this is awkward and requires a great deal of internal knowledge about the system The gnatpsta utility is designed to deal with this situation It is an Ada program that dynamically determines the values of all the relevant parameters in Standard and prints them out in the form of an Ada source listing for Standard displaying all the values of interest This output is generated to stdout To determine the value of any parameter in package Standard simply run gnatpsta with no qualifiers or arguments and examine the output This is preferable to consulting documentation because you know that the values you are getting are the actual ones provided by the executing system 22 3 The External Symbol Naming Scheme of GNAT In order to interpret the output from GNAT when using tools that are originally intended for use with other languages it is useful to under 267 GNAT User s Guide for Unix Platforms stand the conve
213. es and processes Inline pragmas However for theinliningto actually occur optimization must be enabled To enable inlining across unit boundaries this is inlining a call in one unit of a subprogram declared in a with ed unit you must also specify this switch In the ab sence of this switch GNAT does not attempt inlining across units and does not need to access the bodies of subprograms for which pragma Inline is specified if they are not in the current unit If you specify this switch the compiler will access these bod ies creating an extra source dependency for the resulting ob ject file and where possible the call will be inlined For fur ther details on when inlining is possible see See Section 25 4 nlining of Subprograms page 330 The front end inlining activated by this switch is generally more extensive and quite often more effective than the stan dard gnatn inlining mode It will also generate additional dependencies 3 2 14 Auxiliary Output Control 23 May 2002 gnatt gnatu Chapter 3 Compiling Using gcc Causes GNAT to write the internal tree for a unit to a file with the extension adt This not normally required but is used by separate analysis tools Typically these tools do the necessary compilations automatically so you should not have to spedify this switch in normal operation Print a list of units required by this compilation on stdout The listing indudes all units on which
214. es or if you need to be sure what version of the compiler you are executing Execute ver version of the compiler This is the gcc version not the GNAT version Assertions enabled Pragma Assert and pragma Debug to be activated Avoid processing gnat adc If a gnat adc file is present it will beignored 39 GNAT User s Guide for Unix Platforms gnatb Generate brief messages to stderr even if verbose mode set gnatc Check syntax and semantics only no code generation at tempted gnatC Compress debug information and external symbol name ta ble entries gnatD Output expanded source files for source level debugging This switch also suppress generation of cross reference in formation see gnatx gnatecpath Specify a configuration pragma file see Section 8 2 The Configuration Pragmas Files page 132 gnatempath Specify a mapping file see Section 3 2 16 Units to Sources Mapping Files page 71 gnatE Full dynamic elaboration checks gnatf Full errors Multipleerrors per line all undefined references gnatF Externals names are folded to all uppercase gnatg Internal GNAT implementation mode This should not be used for applications programs it is intended only for use by the compiler and its run time library For documentation see the GNAT sources gnatG List generated expanded code in source form gnatic Identifier character set c 1 2 3 4 8 9 p f n w gnath Output usage
215. esent the wide character with code 16 A345 It is also possible though not required to use the 23 May 2002 Chapter 2 The GNAT Compilation Model Brackets coding for upper half characters For example the code 16 A3 can be represented as A3 This scheme is compatible with use of the full Wide_Character set and is also the method used for wide character encoding in the standard ACVC Ada Compiler Validation Capability test suite distributions Note Some of these coding schemes do not permit the full use of the Ada 95 character set For example neither Shift J 1S nor EUC allow the use of the upper half of the Latin 1 set 2 3 File Naming Rules The default file name is determined by the name of the unit that the file contains The name is formed by taking the full expanded name of the unit and replacing the separating dots with hyphens and using lowercase for all letters An exception arises if the file name generated by the above rules starts with one of the characters a g i or s and the second character is a minus In this case the character tilde is used in place of the minus The reason for this special rule is to avoid clashes with the standard names for child units of the packages System Ada I nterfaces and GNAT which use the prefixes s a i and g respectively The file extension is ads for a spec and adb for a body The following list shows some examples of these rules main ads Main s
216. et table can be used with this encoding method EUC Coding A wide character is represented by a two character sequence 16 ab and 16 cd with both characters being in the upper half The internal character code is the corresponding J IS character according to the EUC encoding algorithm Only characters defined in the IS code set table can be used with this encoding method UTF 8 Coding A wide character is represented using UCS Transformation Format 8 UTF 8 as defined in Annex R of ISO 10646 l Am 2 Depending on the character value the represen tation is a one two or three byte sequence 16 0000 16 007f 2 Oxxxxxxx 16 0080 16 07ff 2 110xxxxx 2 10xxxxxx 16 0800 16 ffff 2 1110xxxx 2 10xxxxxx 2 10xxxxxx where the xxx bits correspond to the left padded bits of the 16 bit character value Note that all lower half ASCII char acters are represented as ASCII bytes and all upper half characters and other wide characters are represented as sequences of upper half The full UTF 8 scheme allows for encoding 31 bit characters as 6 byte sequences but in this implementation all UTF 8 sequences of four or more bytes length will be treated as illegal Brackets Coding 18 In this encoding a wide character is represented by the fol lowing eight character sequence abcd Where a b c a are the four hexadecimal characters using uppercase letters of the wide character code For example A345 is used to repr
217. except for the issue of comments and pragmas In default mode the rule is that any pragmas between units belong to the previous unit except that configuration pragmas always belong to the following unit Any comments belong to the following unit These rules almost always result in theright choice of the split point without needing to mark it explicitly and most users will find this default to be what they want In this default mode it is incorrect to submit a file containing only configuration pragmas or one that ends in configuration pragmas to gnat chop However using a special option to activate compilation mode gnatchop Can perform another function which is to provide exactly the semantics required by the RM for handling of configuration pragmas in a compilation In the absence of configuration pragmas at the main file 125 GNAT User s Guide for Unix Platforms level this option has no effect but it causes such configuration pragmas to be handled in a quite different manner First in compilation mode if gnat chop is given a file that consists of only configuration pragmas then this file is appended to the gnat aac fileinthecurrent directory This behavior provides the required behavior described in the RM for the actions to be taken on submitting such a file to the compiler namely that these pragmas should apply to all subsequent compilations in the same compilation environment Using GNAT the current directory possi
218. f the executable program itself Furthermore if this program is run in the normal manner it runs exactly as if the debug information were not present and takes no more actual memory However if the program is run under control of cpp the debugger is activated The image of the program is loaded at which point it is ready to run If a run command is given then the program will run exactly as it would have if cbB were not present This is a crucial part of the cps design philosophy cps is entirely non intrusive until a breakpoint is encountered If no breakpoint is ever hit the program will run exactly as it would if no debugger were present When a breakpoint is hit GpB accesses the debugging information and can respond to user commands to inspect variables and more generally to report on the state of execution 23 2 Running GDB Thedebugger can belaunched directly and simply from glide or through its graphical interface gvd It can also be used directly in text mode Here is described the basic use of cpg in text mode All the commands described below can be used in the gvd console window eventhough there is usually other more graphical ways to achieve the same goals The command to run de graphical interface of the debugger is gvd program The command to run cps in text mode is gdb program where program is the name of the executable file This activates the debugger and results in a prompt for debugger commands The simplest
219. f the stated restriction is in fact met that is to say no task receives an entry call before elaboration of all units is completed 11 8 Mixing Elaboration Models So far we have assumed that the entire program is either compiled using the dynamic model or static model ensuring consistency It is possible to mix the two models but rules have to be followed if this mixing is done to ensure that elaboration checks are not omitted The basic rule is that a unit compiled with the static mode cannot be with ed by a unit compiled with the dynamic modd The reason for this is that in the static model a unit assumes that its clients guarantee to use the equivalent of pragma Elaborate A11 so that no elabora tion checks are required in inner subprograms and this assumption is violated if the dient is compiled with dynamic checks The precise rule is as follows A unit that is compiled with dynamic checks can only with a unit that meets at least one of the following criteria e Thewith ed unit is itself compiled with dynamic elaboration checks that is with the gnatE switch e The with ed unit is an internal GNAT implementation unit from the System Interfaces Ada or GNAT hierarchies e Thewith ed unit has pragma Preelaborate or pragma Pure e The with ing unit that is the dient has an explicit pragma Elaborate All for the with ed unit If this rule is violated that is if a unit with dynamic elaboration checks with
220. file in one project may depend on com pilation units in source files in other projects To obtain this behavior the dependent project must import the projects containing the needed source files This effect is embodied in syntax similar to an Ada with clause but the with ed entities are strings denoting project files As an example suppose that the two projects GUI Proj and Comm _ Proj are defined in the project files gui_proj gpr and comm proj gpr in directories gui and comm respectively Assume that the source files for GUI_Proj are gui ads and gui adb and that the source files for Comm Proj are comm ads and comm adb with each set of files located in its respective project file directory Diagrammaticall y gui gui_proj gpr gui ads gui adb comm comm_proj gpr comm ads comm adb We want to develop an application in directory app that with s the packages GUI and comm Using the properties of the corresponding project files e g the switch settings and object directory Skeletal code for a main procedure might be something like the following 144 M __ M o o vuvuvcCCc ov 0Q Q vu 28 May 2002 Chapter 10 GNAT Project Manager with GUI Comm procedure App_Main is begin end App_Main Here is a project file app_proj gpr that achieves the desired effect with gui gui_proj comm comm proj project App_Proj is for Main use
221. file naming conven tions see Section 10 10 Naming Schemes page 162 10 9 Variables from Imported Projects An attribute or variable defined in an imported or parent project can be used in expressions in the importing extending project Such an attribute or variable is prefixed with the name of the project and if relevant the name of package where it is defined with imported project Main extends base is Vari Imported Var Var2 Base Var amp new package Builder is for Default_Switches Ada use Imported Builder Ada_Switches amp gnatg amp v end Builder package Compiler is for Default_Switches Ada use Base Compiler Ada Switches end Compiler end Main In this example e vari is a copy of the variable var defined in the project file imported gpr 161 GNAT User s Guide for Unix Platforms e thevalueof var2 is a copy of the value of variable var defined in the project file base gpr concatenated with new e attributeDefault Switches Ada in packageBuilderisastring list that includes in its value a copy of variableada Switches defined in the Builder package in project file imported gpr plus two new elements gnatg and v e attributeDefault Switches Ada in package Compiler is a copy of the variable Ada Switches defined in the compiler package in project file base gpr the project being extended 10 10 Naming Schemes Sometimes an Ada software
222. fter a breakpoint If the next state ment is a subprogram call execution continues into the first statement of the called subprogram Executes a single line If this line is a subprogram call executes and returns from the call Lists a few lines around the current source location In prac tice it is usually more convenient to have a separate edit window open with the relevant source file displayed Suc cessive applications of this command print subsequent lines The command can be given an argument which is a line num ber in which case it displays a few lines around the specified one Displays a backtrace of the call chain This command is typ ically used after a breakpoint has occurred to examine the sequence of calls that leads to the current breakpoint The display indudes one line for each activation record frame corresponding to an active subprogram At a breakpoint eps can display the values of variables local tothe current frame The command up can be used to exam inethe contents of other active frames by moving the focus up the stack that is to say from calleeto caller one frame at a time Moves the focus of cps down from the frame currently being examined totheframe of its callee the reverse of the previous command Inspect the frame with the given number The value 0 de notes the frame of the current breakpoint that is to say the top of the call stack The above list is a very short introduction to the
223. g a lower level of optimization does not improve the reliability of the code generator which in practice is highly reliable at all optimization levels 25 3 Debugging Optimized Code Since the compiler generates debugging tables for a compilation unit before it performs optimizations the optimizing transformations may invalidate some of the debugging data You therefore need to anticipate certain anomalous situations that may arise while debugging optimized code This section describes the most common cases 1 The hopping Program Counter Repeated step or next com mands show the PC bouncing back and forth in the code This may result from any of the following optimizations 328 3 May 2002 Chapter 25 Performance Considerations e Common subexpression elimination using a single instance of code for a quantity that the source computes several times Asa result you may not be ableto stop on what looks like a statement e Invariant code motion moving an expression that does not change within a loop to the beginning of the loop e Instruction scheduling moving instructions so as to overlap loads and stores typically with other code or in general to move computations of values closer to their uses Often this causes you to pass an assignment statement without the assignment happening and then later bounce back to the statement when the value is actually needed Placing a breakpoint on a line of code and then
224. ge named Naming will be described below see Section 10 10 Naming Schemes page 162 Source Language s Since the project files do not specify a Languages attribute by default the GNAT tools assume that the language of the project file is Ada More generally a projec can comprise source files in Ada C and or other languages 10 2 2 Using External Variables Instead of supplying different project files for debug and release we can define a single project file that queries an external variable set ei ther on the command line or via an environment variable in order to conditionally define the appropriate settings Again assume that the source files pack ads pack adb and proc adb are located in direc tory common The following project file ouild gpr queries the ex ternal variable named sTYLE and defines an object directory and switch settings based on whether the value is deb debug or rel release where the default is deb 142 K 28 May 2002 Chapter 10 GNAT Project Manager project Build is for Main use proc type Style_Type is deb rel Style Style_Type external STYLE deb case Style is when deb gt for Object_Dir use debug when rel gt for Object_Dir use release for Exec_Dir use end case package Builder is case Style is when deb g
225. ge programming 24 1 Basic Assembler Syntax The assembler used by GNAT and gcc is based not on the Intel assembly language but rather on a language that descends from the AT amp T Unix assembler as and which is often referred to as AT amp T syntax The following table summarizes the main features of as syntax and points out the differences from the Intel conventions See the gcc as and gas an as macro pre processor documentation for further information Register names gcc as Prefix with 96 for example seax Intel No extra punctuation for example eax Immediate operand gcc as Prefix with for example 4 Intel No extra punctuation for example 4 Address gcc as Prefix with for example 1oc Intel No extra punctuation for example 1oc 293 GNAT User s Guide for Unix Platforms Memory contents gcc as No extra punctuation for example loc Intel Square brackets for example 1oc Register contents gcc as Parentheses for example eax Intel Square brackets for example eax Hexadecimal numbers gcc as Leading Ox C language syntax for example oxao Intel Trailing h for example Aon Operand size gcc as Explicit in op code for example movw to move a 16 bit word Intel Implicit deduced by assembler for example mov Instruction repetition gcc as Split into two lines for example rep stosl Intel Keep on one line for example rep stos1 Order of operands gcc as Source
226. ggnatbind 75 4 1 Runningegnatbind iie elo hehe ER dace 75 4 2 Generating the Binder Program inC 92 4 3 Consistency Checking Modes 102 4 4 Binder Error Message Control 102 45 Elaboration Control eee cene 103 4 6 Output Controdl c 104 4 7 Binding with Non Ada Main Programs 105 4 8 Binding Programs with No Main Subprogram 106 4 9 Summary of Binder Switch Ss 106 4 10 Command Line ACCESS ccc s 108 4 11 Search Paths for gnatbind 108 4 12 Examples of gnatbindUSaQge 109 23 May 2002 Linking Using gnatlink LID 5 1 RunninggnatlinkK 2 00000000404060 111 52 Switches TO gab link cose edd aen 2460603 Re nr 112 5 3 Setting Stack Sizefromgnatlink 113 5 4 SettingHeapSizefromgnatlink 114 The GNAT Make Program gnatmake 115 6 1 Running enattakeieess oti sende Ue per RuENNC EE ULURREE 115 6 2 Switchesforgnatmake 2020 222044 116 6 3 Mode Switches for gnatmake 121 6 4 Notes onthe Command Line 121 6 5 How gnatmake WOrKS c cence nne 122 6 6 Examples of gnatmake USaYe 123 Renaming Files Using g
227. gna gna gna Output representation information for dedared types and objects ts Syntax check only tt Tree output file to be generated cT nnn Set time slice to specified number of microseconds tu List units for this compilation tu Tag all error messages with the unique string error tv Verbose mode Full error output with sourcelinesto stdout tV Control level of validity checking See separate section de scribing this feature UWXXXXXX Warning mode where xxx is a string of options describing the exact warnings that are enabled or disabled See separate section on warning control twe Wide character encoding method e n h u s e 8 tx Suppress generation of cross reference information ty Enable built in style checks See separate section describing this feature tzm Distribution stub generation and compilation m r c for re cei ver caller stubs t83 Enforce Ada 83 restrictions 41 GNAT User s Guide for Unix Platforms pass exit codes Catch exit codes from the compiler and use the most mean ingful as exit status You may combine a sequence of GNAT switches into a single switch For example the combined switch gnatofi3 is equivalent to specifying the following sequence of switches gnato gnatf gnati3 The following restrictions apply to the combination of switches in this manner e Theswitch gnatc if combined with other switches must come first in the string e Theswitch g
228. gnatpn instead of gnatp The Incr function is still compiled as usual but at the point in Increment Where our function used to be called pushl edi call increment incr 1 the code for the function body directly appears movl esi eax APP incl eax NO_APP movl eax fedx thus saving the overhead of stack frame setup and an out of line call 302 88 May 2002 Chapter 24 Inline Assembler 24 6 Other asm Functionality This section describes two important parameters to the asm procedure Clobber which identifies register usage and volatile which inhibits unwanted optimizations 24 6 1 The Clobber Parameter One of the dangers of intermixing assembly language and a compiled language such as Ada is that the compiler needs to be aware of which registers are being used by the assembly code n some cases such as the earlier examples the constraint string is sufficient to indicate register usage e g a for the eax register But more generally the compiler needs an explicit identification of the registers that are used by the nline Assembly statements Using a register that the compiler doesn t know about could bea side effect of an instruction like mull storing its result in both eax and edx It can also arise from explicit register usage in your assembly code for example Asm movl 40 ebx amp LF amp HT amp movl 4ebx 1 Inputs gt Unsigned 32 Asm Input g Var In Outputs gt Unsigned
229. gs 141 Main Subprograms 142 Source File Naming Conventions 142 Source Language S 142 10 2 2 Using External Variables 142 10 2 3 Importing Other ProjectS 144 10 2 4 ExtendingaProject 145 Project FileSyntax esses eee 147 10 3 1 BasicSyntax 147 10 3 2 PackaY6S 85 148 10 3 3 EXpresSsiONS Rt RR vs 149 10 3 4 StringTYpES 4258 149 10 3 5 Variabl6 S 150 10 3 6 AttribUteS 151 10 3 7 Associative Array Attributes 154 10 3 8 case ConstructioNS 154 Objects and Sources in Project FileS 155 10 4 1 Object Diredt0Ory 155 1042 Exec Direct0ry 155 10 4 3 Source Directorie S 156 10 4 4 SourceFileNam amp Ss 156 Importing Projects rell eer e Re ace 157 Project EXtenSiON c c yy Ra 159 External References in Project Files 159 Packages in Project FIleS 160 Variables from Imported ProjectS 161 Naming SchemMeS eee ecce ccs 162 Library Preis oan nae cost
230. h a task type dedaration Then we introduce a separate package Declst to contain the actual task object This separates the elaboration issues for the task type declaration which causes no trouble from the elaboration issues of the task object which is also unproblematic since it is now independent of the elaboration of Utils This separation of concerns also corresponds to a gen erally sound engineering principle of separating declarations from instances This version of the program also compiles binds links and executes generating the expected output e Use No_Entry_Calls_ln_Elaboration_Code restriction The previous two approaches described how a program can be re structured to avoid the special problems caused by library task bod ies in practice however such restructuring may bedifficult to apply to existing legacy code so we must consider solutions that do not require massive rewriting Let us consider more carefully why our original sample program works under the dynamic model of elaboration The reason is that the code in the task body blocks immediately on the accept state ment Now of course there is nothing to prohibit elaboration code from making entry calls for example from another library level task so we cannot tell in isolation that the task will not execute the accept statement during elaboration However in practice it is very unusual to see elaboration code make any entry calls and the pattern of tasks start
231. h flags movl 4A4eax 40 store flags in variable Outputs gt Unsigned 32 Asm Output g Flags 0 will be replaced in the expanded code by the appropriate operand whatever the compiler decided for the Flags variable In general you may have any number of output variables e Count the operands starting at 0 thus 20 1 etc e Specify the outputs parameter as a parenthesized comma separated list of Asm output attributes For example Asm movl A4Aeax 40 amp LF amp HT amp movl 4ebx 1 amp LF amp HT amp movl ecx 42 Outputs gt Unsigned_32 Asm_Output g Var A 0 Var_A Unsigned_32 Asm_Output g Var B 1 Var_B Unsigned_32 Asm_Output g Var_C 2 Var_C where var A Var B and var care variables in the Ada program 298 28 May 2002 Chapter 24 Inline Assembler As a variation on theGet Flags example we can use the constraints string to direct the compiler to store the eax register into the Flags variable instead of including the store instruction explicitly in the Asm template string with Interfaces use Interfaces with Ada Text_I0 use Ada Text IO with System Machine Code use System Machine Code procedure Get Flags 2 is Flags Unsigned 32 use ASCII begin Asm pushfl amp LF amp HT amp push flags on stack popl A4Aeax save flags in eax Outputs
232. h s a unit v compiling unit x in syntax check only mode does not access the source file containing unit v Normally GNAT allows only a single unit in a source file However this restriction does not apply in syntax check only mode and it is possible to check a file containing multiple compilation units concatenated together This is primarily used by the gnat chop utility see Chapter 7 Renaming Files Using gnatchop page 125 3 2 9 Using gcc for Semantic Checking gnatc The c stands for check Causes the compiler to operate in semantic check mode with full checking for all illegalities specified in the Ada 95 Reference Manual but without gen eration of any object code no object file is generated Because dependent files must be accessed you must follow theGNAT semanticrestrictions on filestructuringto operate in this mode e The needed source files must be accessible see Sec tion 3 3 Search Paths andthe Run TimeLibrary RTL page 71 e Each file must contain only one compilation unit e Thefilenameand unit name must match see Secti on 2 3 File Naming Rules page 19 The output consists of error messages as appropriate No object fileis generated An aut fileis generated for usein the GNAT User s Guide for Unix Platforms context of cross reference tools but this file is marked as not being suitable for binding since no object file is generated The checking corresponds exactly to the notion of leg
233. hat the spec of x is elaborated before U but you are not assured that the body of x is elaborated before U This means that in the above case the binder is allowed to choose the order spec of Math spec of Stuff body of Math body of Main but that s not good because now the call to Math Sqrt that happens during the elaboration of the stuff spec happens before the body of Math Sqrt is elaborated and hence causes Program Error exception to be raised At first glance one might say that the binder is misbehaving because obviously you want to elaborate the body of something you with GNAT User s Guide for Unix Platforms first but that is not a general rule that can be followed in all cases Consider package X is package Y is with X package body Y is with Y package body X is This is a common arrangement and apart from the order of elabora tion problems that might arise in connection with elaboration code this works fine A rule that says that you must first elaborate the body of anything you with cannot work in this case the body of x with s y which means you would have to elaborate the body of v first but that with s x which means you have to elaborate the body of x first but and we have a loop that cannot be broken It is true that the binder can in many cases guess an order of elabo ration that is unlikely to cause a Program Error exception to be raised and it tries to do so in the abo
234. he debugger to breakpoint at the start of execution procedure Break_Start pragma Import C Break_Start __gnat_break_start 77 GNAT User s Guide for Unix Platforms 78 This is the actual generated main program it would be suppressed if the no main program switch were used As required by standard system conventions this program has the external name main function main argc Integer argv System Address envp System Address return Integer pragma Export C main main The following set of constants give the version identification values for every unit in the bound partition This identification is computed from all dependent semantic units and corresponds to the string that would be returned by use of the Body_Version or Version attributes type Version_32 is mod 2 32 u00001 constant Version_32 u00002 constant Version_32 u00003 constant Version 32 u00004 constant Version 32 u00005 constant Version 32 u00006 constant Version 32 u00007 constant Version 32 u00008 constant Version 32 u00009 constant Version 32 u00010 constant Version 32 u00011 constant Version 32 u00012 constant Version 32 u00013 constant Version 32 u00014 constant Version 32 u00015 constant Version 32 u00016 constant Version 32 u00017 constant Version 32 u00018 constant Version 32 u00019 consta
235. he execution of the program consists of elaboration of these units in an appropriate order 4 9 Summary of Binder Switches The following are the switches available with gnatbind a0 Specify directory to be searched for ALI files aI Specify directory to be searched for source file A Generate binder program in Ada default b Generate brief messages to stderr even if verbose mode set c Check only no generation of binder output file C Generate binder program in C e Output complete list of elaboration order dependencies E Store tracebacks in exception occurrences when the target supports it This is the default with the zero cost excep tion mechanism This option is currently supported on the following targets all x86 ports Solaris Windows HP UX AIX PowerPC VxWorks and Alpha VxWorks See also the packages GNAT Traceback and GNAT Traceback Symbolic for more information Note that on x86 ports you must not use fomit frame pointer gcc option 106 23 May 2002 SE LXXX Mxyz mn n nostdinc nostdlib RTS rts o file static shared E Tn Chapter 4 Binding Using gnatbind Output usage help information Specify directory to be searched for source and ALI files Do not look for sources in the current directory where gnatbind was invoked and do not look for ALI files in the directory containingtheALI filenamed in the gnatbind com mand line Output chosen elaboratio
236. he object files for a program Each object file has the same name as the corresponding source file except that the extension is o as usual You may wish to compile other files for the purpose of checking their syntactic and semantic correctness For example in the case where a package has a separate spec and body you would not normally compile the spec However it is convenient in practice to compile the spec to make sure it is error free before compiling dients of this spec because such compilations will fail if there is an error in the spec GNAT provides an option for compiling such files purely for the pur poses of checking correctness such compilations are not required as part of the process of building a program To compile a file in this checking mode use the gnatc switch 2 7 Source Dependencies A given object file dearly depends on the source file which is compiled to produce it Here we are using depends in the sense of a typical make utility in other words an object file depends on a source file if changes to the source file require the object file to be recompiled In addition to this basic dependency a given object may depend on additional source files as follows e If a file being compiled with s a unit x the object file depends on the file containing the spec of unit x This includes files that are with ed implicitly either because they are parents of with ed child units or they arerun time units required by t
237. he tags file is output to the standard output thus you will have to redirect it to a file All these switches may be in any order on the command line and may even appear after the file names They need not be separated by spaces thus you can say gnatxref ag instead of gnatxref a g 12 2 gnatfind Switches The command line for gnat find is gnatfind switches pattern sourcefile line column filet file2 where pattern An entity will be output only if it matches the regular ex pression found in pattern see See Section 12 4 Regular Expressions in gnatfind and gnatxref page 215 Omitting the pattern is equivalent to specifying which will match any entity Note that if you do not provide a pattern you haveto provide both a sourcefile and a line Entity names are given in Latin 1 with uppercase lowercase equivalencefor matching purposes At thecurrent timethere is no support for 8 bit codes other than Latin 1 or for wide characters in identifiers sourcefile gnatfind Will look for references bodies or dedarations of symbols referenced in sourcefile atline 1ine and column column See see Section 12 6 Examples of gnatfind Usage page 219 for syntax examples line is a decimal integer identifying the line number containing the reference to the entity or entities to be located column is a decimal integer identifying the exact location on theline of the first character of the
238. helanguage constructs used in a particular unit 24 28 May 2002 Chapter 2 The GNAT Compilation Model e Ifa file being compiled instantiates a library level generic unit the object file depends on both the spec and body files for this generic unit e If a file being compiled instantiates a generic unit defined within a package the object file depends on the body file for the package as well as the spec file e f a file being compiled contains a call to a subprogram for which pragma Inline applies and inlining is activated with the gnatn switch the object file depends on the file containing the body of this subprogram as well as on the file containing the spec Note that for inlining to actually occur as a result of the use of this switch it is necessary to compile in optimizing mode The use of gnatN activates a more extensive inlining optimization that is performed by thefront end of the compiler Thisinlining does not require that the code generation be optimized Like gnatn the use of this switch generates additional dependencies e f an object file O depends on the proper body of a subunit through inlining or instantiation it depends on the parent unit of the sub unit This means that any modification of the parent unit or one of its subunits affects the compilation of O e Theobject file for a parent unit depen
239. hough F 2 calls F1 because the call appears after the elaboration of the body of F1 Therefore the pragma 1 is safe and will remove the warning on the call It is also possible to use pragma 2 because there are no other potentially unsafe calls in the block The call to Pure is safe because this function does not depend on the state of Pack2 Therefore any call to this function is safe anditis correct to place pragma 3 in the corresponding package spec Finally we could place pragma 4 in the spec of Pack2 to disable warnings on all calls to functions declared therein Note that this is not necessarily safe and requires more detailed examination of the subprogram bodies involved In particular a call to F2 requires that r1 be already elaborated It is hard to generalize on which of these four approaches should be taken Obviously if it is possible to fix the program so that the default 203 GNAT User s Guide for Unix Platforms treatment works this is preferable but this may not always be practi cal It is certainly simple enough to use gnatE but the danger in this case is that even if the GNAT binder finds a correct elaboration order it may not always do so and certainly a binder from another Ada com piler might not A combination of testing and analysis for which the warnings generated with the gnatw1 Switch can be useful must be used to ensure that the program is free of errors One switch that is useful in this te
240. hows the distinction X1 Integer Integer Last X2 Integer range 1 5 5 X1 X1 1 gnato required to catch the Constraint_Error X2 X2 1 range check gnato has no effect here Here the first addition results in a value that is outside the base range of Integer and hence requires an overflow check for detection of the constraint error The second increment operation results in a violation of the explicit range con straint and such range checks are always performed Ba sically the compiler can assume that in the absence of the 6O 1 _ 23 May 2002 Chapter 3 Compiling Using gcc gnato switch that any value of type xxx is in range of the base type of xxx Note that the gnato switch does not affect the code gener ated for any floating point operations it applies only to inte ger semantics For floating point GNAT has the Machine _ Overflows attribute set to False and the normal mode of operation is to generate IEEE NaN and infinite values on overflow or invalid operations such as dividing 0 0 by 0 0 Thereason that we distinguish overflow checking from other kinds of range constraint checking is that a failure of an overflow check can generate an incorrect value but cannot cause erroneous behavior This is unlike the situation with a constraint check on an array subscript where failure to perform the check can result in random memory description or the range check on a case state
241. ices that are easily handled e Using a common set of source files but generating object files in different directories via different switch settings e Using amostly shared set of source files but with different versions of some unit or units The destination of an executable can be controlled inside a project file using the o switch In the absence of such a switch either inside the project file or on the command line any executable files generated by gnatmake Will be placed in the directory Exec Dir specified in the project file If no Exec Dir is specified they will be placed in the object directory of the project You can use project files to achieve some of the effects of a source ver sioning system for example defining separate projects for the different sets of sources that comprise different releases but the P roject M anager is independent of any source configuration management tools that might be used by the developers The next section introduces the main features of GNAT s project fa cility through a sequence of examples subsequent sections will present the syntax and semantics in more detail 10 2 Examples of Project Files This section illustrates some of the typical uses of project files and ex plains their basic structure and behavior 10 2 1 Common Sources with Different Switches and Different Output Directories Assume that the Ada source files pack ads pack adb and proc adb are in the
242. identifier for the entity reference Columns are numbered from 1 filel file2 The search will be restricted to these files If none are given then the search will bedonefor every library filein the search path These file must appear only after the pattern or source file These file names are considered to be regular expressions so for instance specifying source adb is the same as giving every file in the current directory whose name starts with source and whose extension is adb 211 GNAT User s Guide for Unix Platforms Not that if you specify at least one file in this part gnat find may sometimes not be able to find the body of the subpro grams At least one of sourcefile or pattern has to be present on the com mand line The following switches are available a aIDIR aODIR nostdinc nostdlib RTS rts IDIR 212 If this switch is present gnat find and gnatxref will parse the read only files found in the library search path Other wise these files will be ignored This option can be used to protect Gnat sources or your own libraries from being parsed thus making gnat find and gnatxref much faster and their output much smaller When looking for source files also look in directory DIR The order in which source file search is undertaken is the same as for gnatmake When searching for library and object files look in directory DIR Theorder in which library files are s
243. iguration pragmas file file instead of the default snat adc There may be zero one or more space between c and file file may include directory infor mation file must be writeable There may be only one switch c When a switch c is specified no switch P may be specified see below Look for source files in directory dir There may be zero one or more spaces between a and dir When a switch ais specified the current working directory will not be searched for source files unless it is explictly specified with a a or D switch Several switches a may be specified If aix isarel ative path it is relative to the directory of the configuration pragmas file specified with switch c or to the directory of the project file specified with switch p or if neither switch c nor switch p are specified it is relative to the current working directory The directory specified with switch c must exist and be readable Look for source files in all directories listed in text file file There may be zero one or more spaces between a and dir ile must bean existing readabletext file Each non empty line in iie must be a directory Specifying switch D is equivalent to specifying as many switches d as there are non empty lines in file Output usage help information The output is written to stdout Create or update project file proj There may be zero one or more
244. ike to place their object files into build subdirectories of the source directories Furthermore we would like to have to have two separate subdirectories in build release and debug which will contain the object files compiled with different set of compilation flags In other words we have the following structure main progi build debug release prog2 build debug release Here are the project files that we need to create in a directory main to maintain this structure 1 We create a common project with a package compiler that specifies the compilation switches File common gpr project Common is for Source_Dirs use No source files 172 28 May 2002 Chapter 10 GNAT Project Manager type Build_Type is release debug Build Build Type External BUILD debug package Compiler is case Build is when release for Default Switches Ada use 02 when debug gt for Default_Switches Ada use g end case end Compiler end Common 2 We create separate projects for the two programs File progi gpr with common project Progi is for Source Dirs use progi for Object Dir use progi build amp Common Build package Compiler renames Common Compiler end Progi File prog2 gpr w
245. ile The predefined list indudes the following packages e Naming e Builder e Compiler e Binder e Linker e Finder e Cross Reference e gnatls The complete list of the package names and their attributes can be found in file pxj attr adb In its simplest form a package may be empty project Simple is package Builder is end Builder end Simple A package may contain attri bute declarations variable declarations and case constructions as will be described below When thereis ambiguity between a project nameand a package name the name always designates the project To avoid possible confusion it is always a good idea to avoid naming a project with one of the names allowed for packages or any name that starts with gnat 148 28 May 2002 Chapter 10 GNAT Project Manager 10 3 3 Expressions An expression is either a string expression or a string list expression A string expression is either a simplestring expression or a compound string expression A simple string expression is one of the following e A literal string e g comm my_proj gpr e A string valued variable reference see Section 10 3 5 Variables page 150 e A string valued attribute reference see Section 10 3 6 Attributes page 151 e An external reference see Section 10 7 External References in Project Files page 159 A compound string expression is a concatenation of string expressions using amp Path amp amp
246. ile name ruleis used for subunits as well The separate rule for subunits can also be used to implement the rather unusual case of a compilation environment eg a single direc tory which contains a subunit and a child unit with the same unit name Although both units cannot appear in the same partition the Ada Ref erence Manual allows but does not require the possibility of the two units coexisting in the same environment Thefile nametranslation works in the following steps e If there is a specific source File Name pragma for the given unit then this is always used and any general pattern rules are ignored e If thereis a pattern type source File Name pragma that applies to the unit then the resulting file name will be used if the file exists If more than one pattern matches the latest one will be tried first and the first attempt resulting in a reference toa file that exists will be used e f no pattern type Source File Name pragma that applies to the unit for which the corresponding file exists then thestandard GNAT default naming rules are used As an example of the use of this mechanism consider a commonly used scheme in which file names are all lower case with separating periods copied unchanged tothe resulting filename and specs end with 1 ada and bodies end with 2 ada GNAT will follow this scheme if the following two pragmas appear pragma Source File Name Spec File Name gt 1 ada 22
247. iler PRETEREA 35 Models cort rV Re A DM USUS Ui 35 GNAT User s Guide for Unix Platforms 2 13 Comparison between GNAT and Conventional Ada 3 1 3 2 3 3 3 4 Library Models 25 222236 2849252305 2 XI O dd EEN 36 3 Compiling Usinggcc 37 CompilingPrograMS c ceca Dex rU 37 SWITCHES TOF G Cz Los acc uiid i6 dace a e nd Rot eee G 38 3 2 1 Output and Error Message Control 42 3 2 2 Debugging and Assertion Control 51 3 2 3 Validity Checking 52 3 2 4 Style Cheking 54 3 25 Run TimeCheckS 60 3 2 6 Stack Overflow Checking 61 3 2 7 Run TimeControl 62 3 2 8 Using gcc for Syntax Checking 62 3 2 9 Using gcc for Semantic Checking 63 3 2 10 Compiling Ada 83 Programs 64 3 2 11 Character Set Control 64 3 212 FileNamingControl 66 3 2 13 Subprogram Inlining Control 66 3 2 14 Auxiliary Output Control 66 3 2 15 DebuggingControl 67 3 2 16 Units to Sources Mapping Files 71 Search Paths and the Run Time Library RTL 71 Order of Compilation ISSUES 73 Examples re anness ea er t ae qe d Ld ande EA ne 73 3 5 4 Binding Usin
248. iles see Section 2 8 The Ada Library I nformation Files page 26 for which information is requested In normal mode without additional option gnat1s produces a four column listing Each line represents information for a specific object The first column gives the full path of the object the second column gives the name of the principal unit in this object the third column gives the status of the source and the fourth column gives the full path of the source representing this unit Hereis a simple example of use gnatls o demo1 o demo1 DIF demo1 adb demo2 o demo2 OK demo2 adb hello o hi OK hello adb instr child o instr child MOK instr child adb instr o instr OK instr adb tef o tef DIF tef adb text io example o text io example OK text io example adb tgef o tgef DIF tgef adb The first line can be interpreted as follows the main unit which is contained in object file emo1 o is demol whose main source is in demo1 adb Furthermore the version of the source used for the compi lation of demol has been modified DIF Each source file has a status qualifier which can be OK unchanged The version of the source file used for the compilation of the specified unit corresponds exactly to the actual source file MOK slightly modified The version of the source file used for the compilation of the specified unit differs from the actual source file but not enough to require recompilation If you use gnat
249. iles generated by compiling the RTL are needed by the binder and the linker and are kept together in one directory typically different from the directory containing the sources In a normal installation you need not spedify these directory names when compiling or binding Either the environment variables or the built in defaults causethese files to be found Besides simplifying access tothe RTL a major useof search paths isin compiling sources from multiple directories This can make development environments much more flexible 4 12 Examples of gnatbind Usage This section contains a number of examples of using the GNAT binding utility gnatbind gnatbind hello The main program Hello source program in hello adb iS bound using the standard switch settings The generated main program is b hello adb This is the normal default use of the binder gnatbind hello o mainprog adb The main program Hello source program in he11o adb is bound using the standard switch settings The generated main program is mainprog adb with the associated spec in mainprog ads Notethat you must specify the body here not 109 GNAT User s Guide for Unix Platforms the spec in the case where the output is in Ada Note that if this option is Used then linking must be done manually since gnatlink will not be able to find the generated file gnatbindmain C o mainprog c x The main program main source program in main adb iS bound exc
250. iling a subset of these source files The files you need to compile are the following e f a package spec has no body compile the package spec to produce the object file for the package e f a package has both a spec and a body compile the body to produce the object file for the package The source file for the package spec need not be compiled in this case because there is only one object file which contains the code for both the spec and body of the package 23 GNAT User s Guide for Unix Platforms e For a subprogram compile the subprogram body to produce the object file for the subprogram The spec if one is present is as usual in a separate file and need not be compiled e n thecase of subunits only compile the parent unit A single object file is generated for the entire subunit tree which indudes all the subunits e Compile child units independently of their parent units though of course the spec of all the ancestor unit must be present in order to compile a child unit e Compile generic units in the same manner as any other units The object files in this case are small dummy files that contain at most the flag used for elaboration checking This is because GNAT always handles generic instantiation by means of macro expansion How ever it is still necessary to compile generic units for dependency checking and elaboration purposes The preceding rules describe the set of files that must be compiled to generate t
251. information The output is written to stdout gnatkn Limit filenames to n 1 999 characters k krunch gnatl Output full source listing with embedded error messages gnatmn Limit number of detected errors to n 1 999 gnatn Activate inlining across unit boundaries for subprograms for which pragma inline is specified gnatN Activate front end inlining fno inline Suppresses all inlining even if other optimization or inlining switches are set fstack check Activates stack checking See separate section on stack checking for details of the use of this option 4 28 May 2002 Chapter 3 Compiling Using gcc gnato Enable numeric overflow checking which is not normally enabled by default Not that division by zero is a separate check that is not controlled by this switch division by zero checking is on by default gnatp Suppress all checks gnatq Don t quit try semantics even if parse errors gnatQ Don t quit generate a1i and tree files even if illegalities gnatP Enable polling This is required on some systems no tably Windows NT to obtain asynchronous abort and asyn chronous transfer of control capability See the description of pragma Polling in the GNAT Reference Manual for full details gnatR 0 1 2 3 s gna gna gna gna gna gna gna gna gna gna
252. information possible on each re quested units including special characteristics such as 230 23 May 2002 Chapter 15 The GNAT Library Browser gnat1s Preelaborable Theunit is preelaborable in the Ada 95 sense No Elab Code No elaboration code has been produced by the compiler for this unit Pure The unit is pure in the Ada 95 sense Elaborate_Body The unit contains a pragma Elaborate_B ody Remote Types The unit contains a pragma Remote Types Shared Passive The unit contains a pragma Shared_Passive Predefined This unit is part of the predefined environment and cannot be modified by the user Remote Call Interface The unit contains a pragma Re mote Call nterface 15 3 Example of gnatls Usage Example of using the verbose switch Note how the source and object paths are affected by the I switch gnatls v I demo o GNATLS 3 10w 970212 Copyright 1999 Free Software Foundation Inc Source Search Path Current Directory home comar local adainclude Object Search Path lt Current_Directory gt home comar local lib gcc lib mips sni sysv4 2 7 2 adalib demo1 o Unit gt Name gt demo1 231 GNAT User s Guide for Unix Platforms Kind gt subprogram body Flags gt No_Elab_Code Source gt demo1 adb modified The following is an exa
253. ing at elaboration time and then immediately blocking on accept or select statements is very common What this means is that the compiler is being too pessimistic when it analyzes the whole package body as though it might be executed at elaboration time If we know that the elaboration code contains no entry calls a very safe assumption most of the time that could almost be made the default behavior then we can compile all units of the program under control of the following configuration pragma pragma Restrictions No_Entry_Calls_In_Elaboration_Code This pragma can be placed in the gnat adc file in the usual man ner If we take our original unmodified program and compile it in the presence of a gnat adc containing the above pragma then once again we can compile bind link and execute obtaining the expected result In the presence of this pragma the compiler does not trace calls in a task body that appear after the first accept or select Statement and therefore does not report a potential circu larity in theoriginal program 198 28 May 2002 Chapter 11 Elaboration Order Handling in GNAT Thecompiler will check to the extent it can that the aboverestricti on is not violated but it is not always possible to do a complete check at compile time so it is important to use this pragma only i
254. ing is used gnatE switch used for com pilation This is because in the default static elaboration mode all necessary Elaborate A11 pragmas are implicitly inserted These implicit pragmas are still respected by the binder in p mode so a safe elaboration order is assured 103 GNAT User s Guide for Unix Platforms 4 6 Output Control The following switches allow additional control over the output gener ated by the binder A o file 104 Generate binder program in Ada default The binder pro gram is named b mainprog adb by default This can be changed with o gnatbind option Check only Do not generate the binder output file In this mode the binder performs all error checks but does not gen erate an output file Generate binder program in C The binder program is named b_mainprog c This can be changed with o gnatbind op tion Output complete list of elaboration order dependencies showing the reason for each dependency This output can be rather extensive but may be useful in diagnosing problems with elaboration order The output is written to stdout Output usage information The output is written to stdout Output linker options to stdout Includes library search paths contents of pragmas Ident and Linker_Options and libraries added by gnatbind Output chosen elaboration order The output is written to stdout Output full names of all the object files that must be link
255. ing normal Ada case insensitive rules for its syntax and value is one of the following e Empty corresponding to a null substitution e A string literal using normal Ada syntax e Any sequence of characters from the set letters digits period un derline Comment lines may also appear in the definitions file starting with the usual and comments may be added to the definitions lines 14 4 Form of Input Text for gnatprep The input text may contain preprocessor conditional inclusion lines as well as general symbol substitution sequences The preprocessor condi tional indusion commands have the form 226 33 May 2002 Chapter 14 Preprocessing Using gnatprep if expression then lines elsif expression then lines elsif expression then lines else lines end if In this example expression is defined by the following grammar expression lt symbol gt expression lt symbol gt lt value gt expression lt symbol gt symbol expression lt symbol gt Defined expression not expression expression expression and expression expression expression or expression expression expression and then expression expression expression or else expression expression expression For the first test expression symbol gt the symbol must have either the value true or false that is to say the right hand of the symbol defi nition must be one of the
256. ion of box comments where lines of minus signs are used to form the top and bottom of the box If a comment starts and ends with is permitted as long as at least one blank follows the initial To gether with the preceding rule this allows the construc tion of box comments as shown in thefollowing example This is a box comment with two text lines e check end exit labels If theletter e appears in thestringafter gnaty then optional labels on ena statements ending subprograms and on exit statements exiting named loops are required to be present 55 GNAT User s Guide for Unix Platforms f no form feeds or vertical tabs If the letter f appears in the string after gnaty then neither form feeds nor vertical tab characters are not permitted in the source text h no horizontal tabs If the letter h appears in the string after gnaty then hor izontal tab characters are not permitted in the source text Together with the b no blanks at end of line check this enforces a canonical form for the use of blanks to separate source tokens i check if then layout If the letter i appears in the string after gnaty then the keyword then must appear either on the same line as corre sponding i or on a line on its own lined up under the i with at least one non blank line in between containing all or part of the condition to be tested k check keyword casing If the letter k appears in the string after gn
257. ion_Code etii ton ath seuss haga A EAT E rtm eie Ss 198 Object file list 91 Order of elaboration 177 Other Ada compilers 28 Overflow checks 60 327 P Parallel make 118 Performance ee dare na ee Kaere 327 pragma Elaborate 183 pragma Elaborate_All 183 pragma Elaborate_Body 182 pragma Inline 330 pragma Preelaborate 182 pragma P res ocu dus 182 pragma Suppress 327 pragma Unsuppress 327 Pragmas configuration 131 Preelaborate 000 182 PUE ant eal Vb aie Ve G QU et VARE 182 REE inibi SA Sah ait 39 S SDP Table Build 84 Search paths for gnatmake 120 Shift JIS Coding 18 Source file end 15 Source files suppressing search 120 Source files use by binder 76 Source File Name pragma 20 21 Source Reference 128 Stack Overflow Checking 61 stack traceback 284 stack unwinding 284 Std6all succi gato en Ee d RR 30 Stderr rper Dei 42 43 Stdout ive erba ERE eH i 43 storage pool memory corruption 255 St bbed o ru Sasat appui taada R 30 Style checking 5 54 SUB rug obe pe Rape Sod 15 Subunits
258. is gnatbind switches mainprog ali switches where mainprog adb is the Ada file containing the main program unit body If no switches are specified gnatbind constructs an Ada package in two files which names are b ada main ads and b ada main adb For example if given the parameter hello ali for a main program con tained in file hello adb the binder output files would be b hello ads and b hello adb When doing consistency checking the binder takes into consideration any source files it can locate For example if the binder determines that the given main program requires the package Pack whose a1i file iS pack ali and whose corresponding source spec file is pack ads it attempts to locate the source file pack ads using the same search path conventions as previously described for the acc command If it can locatethis source file it checks that the time stamps or source checksums 75 GNAT User s Guide for Unix Platforms of the source and its references to in a1i files match In other words any ali files that mentions this spec must have resulted from compiling this version of the source file or in the case where the source checksums match a version close enough that the difference does not matter The effect of this consistency checking which includes source files is that the binder ensures that the program is consistent with the latest version of the source files that can be loca
259. is parsing operation The exact file names will of course depend on the environment host target and location of files on the host system BEGIN Object file option list hello o zuo xh L usr local gnat lib gcc lib i686 pc linux gnu 2 8 1 adalib usr local gnat lib gcc lib i686 pc linux gnu 2 8 1 adalib libgnat a END Object file option list end ada main The Ada code in the above example is exactly what is generated by the binder We have added comments to more dearly indicate the function of each part of the generated Aaa Main package The code is standard Ada in all respects and can be processed by any tools that handle Ada In particular it is possible to use the debugger in Ada mode to debug the generated Ada Main package For example suppose that for reasons that you do not understand your program is blowing up during elaboration of the body of Ada Text 1o Tochasethis bug down you can place a breakpoint on the call Ada Text Io Elab Body and trace the elaboration routine for this package to find out where the problem might be more usually of course you would be debugging elaboration code in your own application 91 GNAT User s Guide for Unix Platforms 4 2 Generating the Binder Program in C In most normal usage the default mode of gnatbina which is to generate the main package in Ada as described in the previous section In par ticular this means that any Ada programmer can rea
260. iscrete choice list gt case construction attribute declaration discrete choice list literal string literal string name simple name simple name simple name identifier same as Ada 276 23May 2002 Chapter 11 Elaboration Order Handling in GNAT 11 Elaboration Order Handling in GNAT This chapter describes the handling of elaboration code in Ada 95 and in GNAT and discusses how the order of elaboration of program units can be controlled in GNAT either automatically or with explicit program ming features 11 1 Elaboration Code in Ada 95 Ada 95 provides rather general mechanisms for executing code at elab oration time that is to say before the main program starts executing Such code arises in three contexts Initializers for variables Variables declared at the library level in package specs or bodies can require initialization that is performed at elabo ration time as in Sqrt_Half Float Sqrt 0 5 Package initialization code Code in a BEGIN END Section at the outer level of a package body is executed as part of the package body elaboration code Library level task allocators Tasks that are declared using task allocators at the library level start executing immediately and hence can execute at elaboration time Subprogram calls are possible in any of these contexts which m
261. isplay information on all allocation roots An allocation root is a specific point in the execution of the program that generates some dynamic allocation such as a new construct This root is represented by an execution backtrace or subprogram call stack By default the backtrace depth for allocations roots is 1 so that a root corresponds exactly to a source location The backtrace can be made deeper to make the root more specific 18 2 Running gnatmem GMEM Mode The gnatmem command has the form gnatmem q n i gmem out user program program argl The program must have been linked with the instrumented versi on of the allocation and deallocation routines This is done with linking with the libgmem a library For better results the user program should be compiled with debugging options Section 3 2 Switches for gcc page 38 For example to build my program 243 23 May 2002 Chapter 18 Finding Memory Problems with gnatmem gnatmake g my program largs lgmem When running my_program the file gmem out is produced This file contains information about all allocations and deallocations done by the program It is produced by the instrumented allocations and dealloca tions routines and will be used by gnatmem Gnatmem must be supplied with the gmem out file and the executable to examine followed by its run
262. it a string value Similarly if a variable has been dedared as a string list all subsequent declarations must give it a string list value A variable reference may take several forms e Thesimple variable name for a variablein the current package if any or in the current project e A context name followed by a dot followed by the variable name A context may be one of the following e Thename of an existing package in the current project e Thename of an imported project of the current project e The name of an ancestor project i e a project extended by the current project either directly or indirectly e An imported parent project name followed by a dot followed by a package name A variable reference may be used in an expression 10 3 6 Attributes A project and its packages may have attributes that definethe project s properties Some attributes have values that are strings others have values that are string lists There are two categories of attributes simple attributes and associa tive arrays see Section 10 3 7 Associative Array Attributes page 154 The names of the attributes are restricted there is a list of project attributes and a list of package attributes for each package The names are not case sensitive The project attributes are as follows all are simple attributes Attribute N ame Value Source Files string list 151 GNAT User s Guide for Unix Platforms Source Dirs string list Source Lis
263. itch tells GNAT to con tinue with semanticanalysis even if syntax errors have been found This may enablethe detection of more errors in a sin gle run On the other hand the semantic analyzer is more likely to encounter some internal fatal error when given a syntactically invalid tree 23 May 2002 gnatQ Chapter 3 Compiling Using gcc In normal operation mode the a1i file is not generated if any illegalities are detected in the program The use of gnatQ forces generation of the ali file This file is marked as being in error so it cannot be used for binding purposes but it does contain reasonably complete cross reference infor mation and thus may be useful for use by tools e g seman tic browsing tools or integrated development environments that are driven from the a1i file In addition if gnatt is also specified then the tree file is generated even if there are illegalities It may be useful in this case to also specify anatq to ensure that full semantic processing occurs The resulting tree file can be processed by ASIS for the purpose of providing partial information about illegal units but if the error causes the tree to be badly malformed then ASIS may crash during the analysis In addition to error messages which correspond toillegalities as defined in the Ada 95 Reference Manual the compiler detects two kinds of warning situations First the compiler considers some constructs suspicious and generates
264. ith common project Prog2 is for Source Dirs use prog2 for Object Dir use prog2 build amp Common Build package Compiler renames Common Compiler end Prog2 3 We create a wrapping project Main 173 GNAT User s Guide for Unix Platforms File main gpr with common with prog1 with prog2 project Main is package Compiler renames Common Compiler end Main 4 Finally we need to create a dummy procedure that withs either explicitly or implicitly all the sources of our two programs Now we can build the programs using the command gnatmake Pmain dummy for the Debug mode or gnatmake Pmain XBUILD release for the Release mode 10 15 Project File Complete Syntax project context clause project declaration context clause with clause with clause with literal string literal string project declaration project project simple name extends literal string is declarative item end project simple name declarative item package declaration typed string declaration other declarative item package declaration package package simple name package completion 174 28 May 2002 Chapter 10 GNAT Project Manager package_completion package_body package_renaming package body is dother declarative item en
265. ix Platforms 258 88 May 2002 Chapter 20 Creating Sample Bodies Using gnat stub 20 Creating Sample Bodies Using gnatstub gnatstub creates body stubs that is empty but compilable bodies for library unit declarations To create a body stub gnat stub has to compile the library unit dec laration Therefore bodies can be created only for legal library units Moreover if a library unit depends semantically upon units located out side the current directory you have to provide the source search path when calling gnat stub see the description of gnat stub Switches below 20 1 Running gnatstub gnatstub has the command line interface of the form gnatstub switches filename directory where filename iS the name of the source file that contains a library unit declaration for which a body must be created This name should follow the GNAT file name conventions Nocrunching is allowed for this file name The file name may contain the path information directory indicates the directory to place a body stub default is the current directory switches iS an optional sequence of switches as described in the next section 20 2 Switches for gnatstub f If the destination directory already contains a file with a name of the body file for the argument spec file replace it with the generated body stub hs Put the comment header i e all the comments pr
266. ization list_controller spec ada finalization list_controller body system file control block spec system file io spec system file io body ada text io spec ada text io body hello body END ELABORATION ORDER end ada_main The following source file name pragmas allow the generated file names to be unique for different main programs They are needed since the package name will always be Ada Main pragma Source File Name ada main Spec File Name gt b hello ads pragma Source File Name ada main Body File Name gt b hello adb Generated package body for Ada Main starts here package body ada main is 2 8 May 2002 Chapter 4 Binding Using gnatbind The actual finalization is performed by calling the library routine in System Standard_Library Adafinal procedure Do_Finalize pragma Import C Do_Finalize system__standard_library__adafinal procedure adainit is These booleans are set to True once the associated unit has been elaborated It is also used to avoid elaborating the same unit twice E040 Boolean pragma Import Ada E040 interfaces c streams E E008 Boolean pragma Import Ada E008 ada exceptions E E014 Boolean pragma Import Ada E014 system exception table E E053 Boolean pragma
267. ize We get to the main program of the partition by using pragma Import because if we try to with the unit and call it Ada style then not only do we waste time recompiling it but also we don t really know the right switches e g identifier character set to be used to compile it procedure Ada_Main_Program pragma Import Ada Ada_Main_Program _ada_hello Start of processing for main begin Save global variables gnat_argc argc gnat_argv argv gnat_envp envp Call low level system initialization Initialize Call our generated Ada initialization routine adainit This is the point at which we want the debugger to get control Break Start Now we call the main program of the partition Ada_Main_Program Perform Ada finalization adafinal Perform low level system finalization 23 May 2002 Chapter 4 Binding Using gnatbind Finalize Return the proper exit status return gnat_exit_status end This section is entirely comments so it has no effect on the compilation of the Ada_Main package It provides the list of object files and linker options as well as some standard libraries needed for the link The gnatlink utility parses this b hello adb file to read these comment lines to generate the appropriate command line arguments for the call to the system linker The BEGIN END lines are used for sentinels for th
268. l elaboration code and determine an appropriate correct order of elabora tion but in the general case this is not possible Consider the following example In the body of unit 1 we have a procedure Func_1 that references thevariablesart 1i which is declared in the elaboration code of the body of Unit 1 Sqrt 1 Float Sqrt 0 1 The elaboration code of the body of unit 1 also contains if expression 1 1 then Q Unit 2 Func 2 end if Unit 2is exactly parallel it has a procedure runc 2 that references the variable sqrt 2 which is declared in the elaboration code of the body Unit 2 Sqrt_2 Float Sqrt 0 1 The elaboration code of the body of unit 2 also contains 278 28 May 2002 Chapter 11 Elaboration Order Handling in GNAT if expression_2 2 then Q Unit_1 Func_1 end if Now the question is which of the following orders of elaboration is ac ceptable Spec of Unit_1 Spec of Unit_2 Body of Unit_1 Body of Unit_2 or Spec of Unit_2 Spec of Unit_1 Body of Unit_2 Body of Unit_1 If you carefully analyze the flow here you will see that you cannot tell at compile time the answer to this question If expression 1 is not equal to 1 and expression 2 iS not equal to 2 then either order is acceptable because neither of the function calls is executed If both tests evaluate to t
269. l detailed effects of these flags Theswitches that print the source of the program reconstructed from theinternal tree areof general interest for user programs as arethe op tions to print the full internal tree and the entity table the symbol table information The reconstructed source provides a readable version of the program after the front end has completed analysis and expansion and is useful when studying the performance of specific constructs For 283 GNAT User s Guide for Unix Platforms example constraint checks are indicated complex aggregates are re placed with loops and assignments and tasking primitives are replaced with run time calls 23 13 Stack Traceback Traceback is a mechanism to display the sequence of subprogram calls that leads to a specified execution point in a program Often but not always the execution point is an instruction at which an exception has been raised This mechanism is also known as stack unwinding because it obtains its information by scanning the run time stack and recovering the activation records of all active subprograms Stack unwinding is one of the most important tools for program debugging The first entry stored in traceback corresponds to the deepest calling level that is to say the subprogram currently executing the instruction from which we want to obtain the traceback Note that thereis noruntime performance penalty when stack traceback is enabled and no exception are r
270. le Machine Check Architecture Conditional Move Instruction Supported if Features CMOV True then Ada Text IO Put Line u CMOV end if Page Attribute Table if Features PAT True then Ada Text_I0 Put_Line PAT end if 36 bit Page Size Extension if Features PSE_36 True then Ada Text_I0 Put_Line end if MMX technology supported if Features MMX True then Ada Text_I0 Put_Line MMX end if Fast FP Save and Restore if Features FXSR True then Ada Text_I0 Put_Line end if FXSR Conditional Move PSE_36 Instruction Supported Page Attribute Table 36 bit Page Size Extension MMX technology supported Fast FP Save and Restore 313 GNAT User s Guide for Unix Platforms Ada Command_Line Set_Exit_Status Ada Command_Line Success exception when others gt Ada Command_Line Set_Exit_Status Ada Command_Line Failure raise end Check_CPU 24 7 2 Intel cPU Package Specification file intel cpu ads ae ae dic ae a ae ae k a ake ac a ale ae ae RICE kk k WARNING for 32 bit Intel processors only akk kk kk kk kkk kkk kk kk k kk kk k k kkk k 2 This package contains a number of subprograms that are useful in determining the Intel x86 CPU and the features it supports on which the program is running The package is based upon the information given in the Intel 314
271. le not the main project file is a library project file it will check all immediate sources of the project and rebuild the library if any of the sources have been recompiled All ALT files will also be copied from the object directory to the library directory To build executables gnatmake will use the library rather than the individual object files 10 12 Switches Related to Project Files The following switches are used by GNAT tools that support project files Pproject Indicates the name of a project file This project file will be parsed with the verbosity indicated by vpx if any and using the external references indicated by x switches if any There must be only one P switch on the command line Since the Project Manager parses the project file only after all the switches on the command line are checked the order of the switches P vpx or x is not significant Xname value Indicates that external variable name has the value va1ue The Project Manager will use this value for occurrences of external name when parsing the project file If name Or value includes a space then name value should be put between quotes X0S NT X user John Doe Several x switches can be used simultaneously If several X switches specify the same name only the last one is used 165 GNAT User s Guide for Unix Platforms An external variable specified with a x switch takes prece dence ove
272. ler Elab_Spec end if E057 True if not E055 then System File_Control_Block Elab_Spec E055 True end if if not E042 then System File_Io Elab_Body E042 True end if if not E006 then Ada Text_Io Elab_Spec end if if not E006 then Ada Text_Io Elab_Body E006 True end if 88 23 May 2002 Chapter 4 Binding Using gnatbind Elab_Final_Code 0 end adainit procedure adafinal is begin Do_Finalize end adafinal main is actually a function as in the ANSI C standard defined to return the exit status The three parameters are the argument count argument values and environment pointer function main argc Integer argv System Address envp System Address return Integer is The initialize routine performs low level system initialization using a standard library routine which sets up signal handling and performs any other required setup The routine can be found in file gt a init c procedure initialize pragma Import C initialize __gnat_initialize The finalize routine performs low level system finalization using a standard library routine The routine is found in file a final c and in the standard distribution is a dummy routine that does nothing so really this is a hook for special user finalization procedure finalize GNAT User s Guide for Unix Platforms pragma Import C finalize __gnat_final
273. li files See Section 2 8 The Ada Library I nfor mation Files page 26 In order to use other packages Chapter 2 The GNAT Compilation Model page 15 requires a certain number of sources to be available to the compiler The minimal set of sources required includes the specs of all the packages that make up the visible part of the library as well as all the sources upon which they depend The bodies of all visible generic units must also be provided Although it is not strictly manda tory it is recommended that all sources needed to recompile the library be provided so that the user can make full use of inter unit inlining and source level debugging This can also make the situation easier for users that need to upgrade their compilation toolchain and thus need to recompile the library from sources The compiled code can be provided in different ways The simplest way is to provide directly the set of objects produced by the compiler during the compilation of the library It is also possible to group the objects into an archive using whatever commands are provided by the operating system Finally it is also possible to create a shared library see option shared in the GCC manual There are various possibilities for compiling the units that make up the library for example with a Makefile Chapter 17 Using the GNU make Utility page 241 or with a conventional script For simple libraries it is also possible to create a dummy main
274. library elaboration proce dure named prefix init andtherun ti mefinalization procedure named prefix final 236 28 May 2002 Chapter 16 GNAT and Libraries generate the binder file in Ada gnatbind Lmylib interface generate the binder file in C gnatbind C Lmylib interface e Compile the files generated by the binder gcc c b interface adb e Createthe library Theprocedure is identical tothe procedure explained in Section 16 1 Creating an Ada Library page 233 except that o interface o needs to be added to the list of objects create an archive file ar cr libmylib a b interface o other object files create a shared library gcc shared o libmylib so b interface o other object files e Provide a foreign view of the library interface The example below shows the content of mylib interface h note that there is no rule for the naming of this file any name can be used the library elaboration procedure extern void mylibinit void the library finalization procedure extern void mylibfinal void the interface exported by the library extern void do something void extern void do something else void 16 4 2 Using the Library Libraries built as explained above can be used from any program pro vided that the elaboration procedures
275. ll Unix systems All the directories found under a given root directory will be added to the list The examples below are based on the following directory hierarchy All the directories can contain any number of files GNAT User s Guide for Unix Platforms ROOT DIRECTORY gt a gt aa gt aaa gt ab gt ac gt b gt ba gt baa gt bb gt bc This Makefile creates a variable called DIRS that can be reused any time you need this list see the other examples in this section The root of your project s directory hierarchy ROOT_DIRECTORY HEHE First method specify explicitly the list of directories This allows you to specify any subset of all the directories you need HHH DIRS a aa a ab b ba Second method use wildcards Note that the argument s to wildcard below should end with a Since wildcards also return file names we have to filter them out to avoid duplicate directory names We thus use make s dir and sort functions It sets DIRs to the following value note that the directories aaa and baa are not given unless you change the arguments to wildcard DIRS a a b a aa a ab a ac b ba b bb b bc HHH DIRS sort dir wildcard ROOT_DIRECTORY ROOT_DIRECTORY Third method use an external program This command is much faster if run on local disks avoiding NFS slowdowns
276. llowing an order of compilation to be chosen that guarantees that gnatmake Will recompute a correct set of new dependencies if necessary When invoking gnatmake with several file names if a unit is im ported by several of the executables it will be recompiled at most once 6 6 Examples of gnatmake Usage gnatmake hello adb Compileall files necessary to bind and link the main program hello adb containing unit Hello and bind and link the resulting object files to generate an executable file hello gnatmake mainl main2 main3 Compile all files necessary to bind and link the main pro grams maini adb containing unit Maini main2 adb con taining unit Main2 and main3 adb containing unit Main3 and bind and link the resulting object files to generate three executable files main1 main2 and main3 gnatmake qMain Unit cargs 02 bargs 1 Compileall files necessary to bind and link the main program unit Main Unit from file main unit aab All compilations will be done with optimization level 2 and the order of elab oration will be listed by the binder gnatmake will operate in quiet mode not displaying commands it is executing 123 GNAT User s Guide for Unix Platforms 124 23 May 2002 Chapter 7 Renaming Files Using gnat chop 7 Renaming Files Using gnatchop This chapter discusses how to handle files with
277. lts in the processor registers Asm the assembler code cpuid execute CPUID zero stored in eax vendor ID string returned in ebx ecx and edx Inputs gt Unsigned_32 Asm_input a 0 ebx is stored in Ebx ecx is stored in Ecx edx is stored in Edx Outputs gt Unsigned Register Asm output b Ebx Unsigned_Register Asm_output c Ecx Unsigned_Register Asm_output d Edx 323 GNAT User s Guide for Unix Platforms 324 now build the vendor ID string Vendor_ID 1 Character Val Ebx L1 Vendor_ID 2 Character Val Ebx H1 Vendor_ID 3 Character Val Ebx L2 Vendor_ID 4 Character Val Ebx H2 Vendor_ID 5 Character Val Edx L1 Vendor_ID 6 Character Val Edx H1 Vendor_ID 7 Character Val Edx L2 Vendor_ID 8 Character Val Edx H2 Vendor_ID 9 Character Val Ecx L1 Vendor_ID 10 Character Val Ecx H1 Vendor_ID 11 Character Val Ecx L2 Vendor_ID 12 Character Val Ecx H2 return string return Vendor_ID end Vendor_ID function Signature return Processor_Signature is Result Processor_Signature processor signature returned begin execute CPUID storing the results in the Result variable Asm the assembler code cpuid execute CPUID one is stored in eax processor signature returned in eax Inputs gt Unsigned_32 Asm_input a 1 eax is stored in Result
278. luding source files from the consistency checking generating the file mainprog c gnatbind x main program C omainprog c This command is exactly the same as the previous example Switches may appear anywhere in the command line and single letter switches may be combined into a single switch gnatbind n math dbase C o ada control c Themain program is in a language other than Ada but calls tosubprograms in packages Math and Dbase appear This call to gnatbind generates the file ada control c containing the adainit and adafinal routines to be called before and after accessing the Ada units 110 AAAS 28 May 2002 Chapter 5 Linking Using gnat 1ink 5 Linking Using gnatlink This chapter discusses gnatlink a utility program used to link Ada programs and build an executable file This is a simple program that invokes the Unix linker via the gcc command with a correct list of object files and library references gnat1ink automatically determines the list of files and references for the Ada part of a program It uses the binder file generated by the binder to determine this list 5 1 Running gnatlink The form of the gnat 1ink command is gnatlink switches mainprog ali non Ada objects linker options mainprog ali references the ALI file of the main program The ali extension of this file can be omitted From this reference gnatlink locates the corresponding binder file b mainprog adb and using th
279. lue of such variables In simple cases a project s source files depend only on other source files in the same project or on the predefined libraries Dependence is in the technical sense for example one Ada unit with ing another However the Project Manager also allows much more sophisticated ar rangements with the sourcefiles in one project depending on sourcefiles in other projects e Oneproject can import other projects containing needed source files e You can organize GNAT projects in a hierarchy a child project can extend a parent project inheriting the parent s source files and optionally overriding any of them with alternative versions 137 GNAT User s Guide for Unix Platforms More generally the Project Manager lets you structure large develop ment efforts into hierarchical subsystems with build decisions deferred to the subsystem level and thus different compilation environments switch settings used for different subsystems The Project Manager is invoked through the pprojectfile switch to gnatmake or to the gnat front driver If you want to define on the command line an external variable that is queried by the project file additionally use the xvbl value switch The Project Manager parses and interprets the project file and drives the invoked tool based on the project settings The Project Manager supports a wide range of development strate gies for systems of all sizes Some typical pract
280. m Gnatmem works by recording each address returned by the allocation procedure gnat malloc along with the backtrace at the allocation point On each deallocation the deallocated address is matched with the corresponding allocation At the end of the processing the unmatched allocations are considered potential leaks All the allocations associated with the same backtrace are grouped together and form an allocation root Theallocation roots are then sorted so that those with the biggest number of unmatched allocation are printed first A delicate aspect of this technique is to distinguish between the data produced by the user program and the data produced by the gdb script Currently on systems that allow probing the terminal the gdb command tty is used to force the program output to be redirected to the current terminal while the gdb Output is directed to a file or to a pipe in order to be processed subsequently by gnatmem 18 6 2 gnatmem Using GMEM Mode This mode use the same algorithm to detect memory leak as the GDB mode of gnatmem the only difference is in the way data are gathered In GMEM mode the program is linked with instrumented version of gnat _ malloc and gnat free routines Information needed to find memory leak are recorded by these routines in file gmem out This mode also require that the stack traceback be available this is only implemented on some platforms Section 18 5 GDB and GMEM Modes page 253 253
281. m Assertions is raised passing static string expression if present as the message as sociated with the exception If no string expression is given d GNAT User s Guide for Unix Platforms the default is a string giving the file name and line number of the pragma The Debug pragma causes procedure to be called Note that pragma Debug May appear within a declaration sequence al lowing debugging procedures to be called between dedara tions 3 2 3 Validity Checking The Ada 95 Reference Manual has specific requirements for checking for invalid values In particular RM 13 9 1 requires that the evaluation of invalid values for example from unchecked conversions not result in erroneous execution In GNAT the result of such an evaluation in normal default mode is to either use the value unmodified or to raise Constraint_E rror in those cases where use of the unmodified value would cause erroneous execution The cases where unmodified values might lead to erroneous execution are case statements where a wild jump might result from an invalid value and subscripts on the left hand side where memory corruption could occur as a result of an invalid value The gnatvx switch allows more control over the validity checking mode The x argument here is a string of letters which control which validity checks are performed in addition to the default checks described above e gnatVc Validity checks for copies The right hand side of a
282. maini adb use 02 for Switches main2 adb use g end Builder For the Builder package the file names should designate source files for main subprograms For the Binder and Linker packages the file names should designate aut or source files for main subprograms n each case just the file name without explicit extension is acceptable 166 28 May 2002 Chapter 10 GNAT Project Manager For each tool used in a program build gnatmake the compiler the binder and the linker its corresponding package contributes a set of switches for each file on which the tool is invoked based on the switch related attributes defined in the package In particular the switches that each of these packages contributes for a given file comprise e the value of attribute switches f if it is specified in the package for the given file e otherwise the value of Default Switches Ada if it is specified in the package If neither of these attributes is defined in the package then the package does not contribute any switches for the given file When gnatmake is invoked on a file the switches comprise two sets in the following order those contributed for the file by the Builder package and the switches passed on the command line When gnatmake invokes a tool compiler binder linker on a file the switches passed to the tool c
283. make with 229 GNAT User s Guide for Unix Platforms the qualifier m minimal recompilation a file marked MOK will not be recompiled DIF modified No version of the source found on the path corresponds to the source used to build this object file not found No source file was found for this unit HID hidden unchanged version not first on PATH The version of the source that corresponds exactly to the source used for compilation has been found on the path but it is hidden by another version of the same source that has been modified 15 2 Switches for gnat1s gnat 1s recognizes the following switches a Consider all units including those of the predefined Ada li brary Especially useful with d d List sources from which specified units depend on h Output the list of options 0 Only output information about object files s Only output information about source files u Only output information about compilation units aOdir aldir Idir z nostdinc Source path manipulation Same meaning as the equiva lent gnatmake flags see Section 6 2 Switches for gnatmake page 116 RTS rts path Specifies the default location of the runtime library Same meaning as the equivalent gnatmake flag see Section 6 2 Switches for gnatmake page 116 v Verbose mode Output the complete source and object paths Do not use the default column layout but instead use long format giving as much as
284. ment where failure to perform the check can cause a wild jump Note again that gnato is off by default so overflow checking is not performed in default mode This means that out of the box with the default settings GNAT does not do all the checks expected from the language description in the Ada Reference Manual If you want all constraint checks to be performed as described in this Manual then you must explicitly use the gnato switch either on the gnatmake or gcc command gnatE Enables dynamicchecks for access before elabor ation on sub program calls and generic instantiations For full details of the effect and use of this switch See Chapter 3 Compiling Using gcc page 37 The setting of these switches only controls the default setting of the checks You may modify them using either suppress to remove checks Or Unsuppress to add back suppressed checks pragmas in the program source 3 2 6 Stack Overflow Checking For most operating systems gcc does not perform stack overflow check ing by default This means that if the main environment task or some other task exceeds the available stack space then unpredictable behav ior will occur To activate stack checking compile all units with the gcc option fstack check For example gcc c fstack check packagei adb 61 GNAT User s Guide for Unix Platforms Units compiled with this option will generate extra instructions to check that any use of the stack for pr
285. mple of use of the dependency list Note the use of the s switch which gives a straight list of source files This can be useful for building specialized scripts gnatls d demo2 o demo2 0 demo2 OK demo2 adb OK gen_list ads OK gen_list adb OK instr ads OK instr child ads gnatls d s a demol o demo1 adb home comar local adainclude ada ads home comar local adainclude a finali ads home comar local adainclude a filico ads home comar local adainclude a stream ads home comar local adainclude a tags ads gen_list ads gen_list adb home comar local adainclude gnat ads home comar local adainclude g io ads instr ads home comar local adainclude system ads home comar local adainclude s exctab ads home comar local adainclude s finimp ads home comar local adainclude s finroo ads home comar local adainclude s secsta ads home comar local adainclude s stalib ads home comar local adainclude s stoele ads home comar local adainclude s stratt ads home comar local adainclude s tasoli ads home comar local adainclude s unstyp ads home comar local adainclude unchconv ads 232 SSS 23May2002 Chapter 16 GNAT and Libraries 16 GNAT and Libraries This chapter addresses some of the issues related to building and using a library with GNAT It also shows how the GNAT run time library can be recompiled 16 1 Creating an Ada Library In the GNAT environment a library has two components e Source files e Compiled code and A
286. ms gnatfindmydir main adb 123 45 Find the declaration for the entity referenced at column 45 in line 123 of file main adb in directory mydir Note that it is usual to omit the identifier name when the column is given since the column position identifies a Unique reference The column has to be the beginning of the identifier and should not point to any character in the middle of the identi fier 220 28 May 2002 Chapter 13 File Name Krunching Using gnatkr 13 File Name Krunching Using gnatkr This chapter discusses the method used by the compiler to shorten the default file names chosen for Ada units so that they do not exceed the maximum length permitted It also describes the gnatkr utility that can be used to determine the result of applying this shortening 13 1 About gnatkr The default file naming rule in GNAT is that the file name must be derived from the unit name The exact default rule is as follows e Takethe unit name and replace all dots by hyphens e f such a replacement occurs in the second character position of a name and the first character is a g s or i then replace the dot by the character tilde instead of a minus The reason for this exception is to avoid clashes with the standard names for children of System Ada Interfaces and GNAT which use the prefixes s a i and g respectively The gnatknn s
287. multiple units by using the gnat chop utility This utility is also useful in renaming files to meet the standard GNAT default file naming conventions 7 1 Handling Files with Multiple Units The basic compilation model of GNAT requires that a file submitted to the compiler have only one unit and there be a strict correspondence between the file name and the unit name Thegnatchop utility allows both of these rules to berelaxed allowing GNAT to process files which contain multiple compilation units and files with arbitrary file names gnatchop reads the specified file and generates one or more output files containing one unit per file The unit and the file name correspond as required by GNAT If you want to permanently restructure a set of foreign files so that they match the GNAT rules and do the remaining development using the GNAT structure you can simply use gnatchop once generate the new set of files and work with them from that point on Alternatively if you want to keep your files in the foreign format perhaps to maintain compatibility with some other Ada compilation sys tem you can set up a procedure where you use gnat chop each time you compile regarding the source files that it writes as temporary files that you throw away 7 2 Operating gnatchop in Compilation Mode The basic function of gnat chop is to take a file with multiple units and split it intoseparate files Theboundary between files is reasonably clear
288. n Boolean Boolean PSE_36 Boolean Natural range 0 Boolean Boolean Natural range 0 end record for Processor_Features use record FPU VME DE PSE TSC MSR PAE MCE CX8 APIC Res_1 SEP MTRR PGE MCA CMOV PAT PSE_36 Res_2 MMX FXSR Res_3 at at at at at at at at at at at at at at at at at at at at at at 0 range range range range range range range range range range range range range range range range range range range range range OO 0000000000000000 00 0o range WONNNF BRP BP BBB Hu FPF PF UU NN OOP 0 DH DO WAN OTH PFPWBNH RE o model specific registers physical address extension machine check extension cmpxchg8 instruction on chip apic hardware reserved for extensions fast system call memory type range registers page global enable machine check architecture conditional move supported page attribute table 36 bit page size extension reserved for extensions MMX technology supported fast FP save and restore reserved for extensions 23 May 2002 Chapter 24 Inline Assembler end record for Processor_Features Size use 32 function Has_FPU return Boolean return True if a FPU is found use only if CPUID is not supported function Has_CPUID return Boolean return True if the processor supports the CPUID instruction function CPUID_Level return Natural return the CPUID support level O 1 or 2 can o
289. n be used to specify theti me slicing value to be used for task switching between equal priority tasks The value nnn is given in microseconds as a decimal integer Setting the time slicing value is only effective if the under lying thread control system can accommodate time slicing Check the documentation of your operating system for de tails Note that the time slicing value can also be set by use of pragma Time_Slice or by use of the t switch in the gnat bind step The pragma overrides a command line argument if both are present and the t switch for gnatbind overrides both the pragma and the scc command line switch 3 2 8 Using gcc for Syntax Checking gnats 62 E May 2002 Chapter 3 Compiling Using gcc The s stands for syntax Run GNAT in syntax checking only mode For example the command gcc c gnats x adb compiles file x adb in syntax check only mode You can check a series of files in a single command and can use wild cards to specify such a group of files Note that you must specify the c compile only flag in addition to the gnats flag You may use other switches in conjunction with gnats In particular gnat1 and gnatv are useful to control the for mat of any generated error messages Theoutput is simply the error messages if any Noobject file or ALI fileis generated by a syntax onl y compilation Also no units other than the one specified are accessed For example if a unit x wit
290. n both directions The C class A has 2 methods The first method is exported to Ada by the means of an extern C wrapper function Thesecond method calls an Ada subprogram On the Ada side The C calls is modelized by a limited record with a layout comparable to the C class The Ada subprogram in turn calls the c method So from the C main program the code goes back and forth between the 2 languages Here are the compilation commands for native configurations gnatmake c simple_cpp_interface c c cpp_main C c c ex7 C gnatbind n simple_cpp_interface gnatlink simple cpp interface o cpp_main LINK CPLUSPLUS lstdc ex7 o cpp main o Here are the corresponding sources 32 SSAA 3 May 2002 Chapter 2 The GNAT Compilation Model cpp_main C include ex7 h extern C void adainit void void adafinal void void method1 A t void method1 A t 1 t methodi int main O 1 A obj adainit obj method2 3030 adafinal O exT h class Origin public int o value 3 class A public Origin i public void method1 void virtual void method2 int v AO int a value gt lex7 C include ex7 h include lt stdio h gt extern C void ada_method2 A t int v 33 GNAT User s Guide for Unix Platforms void A method1 void a_value 2020 printf in A methodi a value d n a_value void A method2 int v 1
291. n compiling specs except for package specs with no bodies because these are compiled as needed by clients If you attempt a useless compilation you will receive an error message It is also useless to compile subunits because they are compiled as needed by the parent e Therearenoorder of compilation requirements performing a com pilation never obsoletes anything The only way you can obsolete something and require recompilations is to modify one of the source files on which it depends e Thereisno library as such apart from the ALI files see Section 2 8 The Ada Library Information Files page 26 for information on the format of these files For now we find it convenient to create separate ALI files but eventually the information therein may be incorporated into the object file directly e When you compile a unit the source files for the specs of all units that it witn all its subunits and the bodies of any generics it in stantiates must be available reachable by the search paths mecha nism described above or you will receive a fatal error message 3 5 Examples The following are some typical Ada compilation command line examples gcc c xyz adb Compile body in file xyz adb with all default options gcc c 02 gnata xyz def adb Compile the child unit package in file xyz def adb with ex tensive optimizations and pragma Assert Debug statements enabled gcc c gnatc abc def adb Compile the sub
292. n order Binds the units for library building In this case the adainit and adafinal procedures See see Section 4 7 Binding with Non Ada Main Programs page 105 are renamed to xxxinit and xxxfinal Implies n See see Chapter 16 GNAT and Libraries page 233 for more details Rename generated main program from main to xyz Limit number of detected errors to n 1 999 No main program Do not look for sources in the system default directory Do not look for library files in the system default directory path Specifies the default location of the runtime library Same meaning as the equivalent gnatmake flag see Section 6 2 Switches for gnatmake page 116 Name the output file file default is o xxx adb Note that if this option is used then linking must be done manually gnatlink cannot be used Output object list Pessimistic worst case elaboration order Require all source files to be present Link against a static GNAT run time Link against a Shared GNAT run time when available Tolerate time stamp and other consistency errors Set the time slice value to n microseconds A value of zero means no time slicing and also indicates to the tasking run time to match as dose as possible to the annex D require ments of the RM 107 GNAT User s Guide for Unix Platforms v Verbose mode Write error messages header summary out put to stdout wx Warning mode x s e for suppress treat as e
293. n speci fied on the command line but have a much higher length limit or even none on most systems It assumes that you have created a list of directories in your M akefile using one of the methods presented in Section 17 2 Automatically Cre ating a List of Directories page 243 For the sake of completeness we assume that the object path where the ALI files are found is different from the sources patch Note a small trick in the Makefile below for efficiency reasons we create two temporary variables SOURCE LIST and OBJ ECT LIST that are expanded immediately by make This way we overcome the standard make behavior which is to expand the variables only when they are actually used GNAT User s Guide for Unix Platforms In this example we create both ADA_INCLUDE_PATH and ADA_OBJECT_PATH This is the same thing as putting the I arguments on the command line the equivalent of using al on the command line would be to define only ADA_INCLUDE_PATH the equivalent of aO is ADA_OBJECT_PATH You can of course have different values for these variables Note also that we need to keep the previous values of these variables since they might have been set before running make to specify where the GNAT library is installed see Automatically creating a list of directories to create these variables SOURCE_DIRS OBJECT_DIRS empty space empty empty SOURCELLIST subst space 8
294. name of the publisher of the Modified Version as the publisher D Preserve all the copyright notices of the Document E Add an appropriate copyright notice for your modifications adjacent to the other copyright notices F Include immediately after the copyright notices a license notice giving the public permission to use the Modified Version under the terms of this License in the form shown in the Addendum below G Preserve in that license notice the full lists of Invariant Sections and required Cover Texts given in the Document s license notice H Include an unaltered copy of this License l Preserve the section entitled History and its title and add to it an item stating at least the title year new authors and publisher of the Modified Version as given on the Title Page If there is no section entitled History in the Document create one stating thetitle year authors and publisher of the Document as given on its Title Page then add an item describing the Modified Version as stated in the previous sentence J Preserve the network location if any given in the Document for public access to a Transparent copy of the Document and likewise the network locations given in the Document for previous versions 336 33 May 2002 Appendix A GNU Free Documentation License it was based on These may be placed in the History section You may omit a network location for a work that was published at least four year
295. natchop 125 7 1 Handling Files with Multiple Units 125 7 2 Operating gnatchop in Compilation Mode 125 7 3 CommandLinefor gnatchop 126 7 4 Switchesforgnatchop 5 127 7 5 Examples of gnatchop USage 129 Configuration Pragmas 131 8 1 Handling of Configuration Pragmas 132 8 2 The Configuration Pragmas FileS 132 Handling Arbitrary File Naming Conventions Using gnatname een nn nnn nnne 133 9 1 Arbitrary FileNaming Conventions 133 9 2 RUNNING enethamessia usas E ae ELSE oU wend 133 9 3 Switches for gnatname 2 2044 134 9 4 Examples of gnatname USaYge 135 GNAT User s Guide for Unix Platforms 10 GNAT Project Manager 137 10 1 10 2 10 3 10 4 10 5 10 6 10 7 10 8 10 9 10 10 10 11 10 12 10 13 Enigo oltla dlo a 02h 137 10 1 1 Proget Files oor Eee E Ono 137 Examples of Project FIlES 138 10 2 1 Common Sources with Different Switches and Different Output Directories 138 Source PICS sae ted tti set En ER ERES 140 Specifying the Object Directory 140 Specifying the Exec Directory 141 Project File PackageS 141 Specifying Switch Settin
296. nats if combined with other switches must come first in the string e Oncea y appears in the string that is a use of the gnaty switch then all further characters in the switch are interpreted as style modifiers See description of gnaty e Oncea d appears in thestring that is a use of the gnata switch then all further characters in the switch are interpreted as debug flags see description of gnatd e Oncea w appears in the string that is a use of the gnatw switch then all further characters in the switch are interpreted as warning mode modifiers see description of gnatw e Oncea V appears inthe string that is a use of the gnatv switch then all further characters in the switch are interpreted as validity checking options see description of gnatv 3 2 1 Output and Error Message Control The standard default format for error messages is called brief format Brief format messages are written to stderr the standard error file and havethe following form e adb 3 04 Incorrect spelling of keyword function e adb 4 20 should be is Thefirst integer after the file name is the line number in the file and the second integer is the column number within the line g1ide can parse the error messages and point to the referenced character The following switches provide control over the error message format 42 eee 28 May 2002 Chapter 3 Compiling Using gcc gnatv Thev stands for verbose The eff
297. nd 103 x gnatbind 102 z gnatbind 106 z gnatmake 120 Jat finalize mes 89 gnat initialize 89 gnat set globals 84 86 23 May 2002 A Access before elaboration 60 Access to subprogram 204 ACVC Ada 83 tests 64 NE ERR SER aoe aes eer on ae 109 283 Ada 83 compatibility 64 Ada 95 Language Reference Manual 3 Ada expressions 277 Ada Library Information files 26 Ada Characters Latin_1 16 ADA INCLUDE PATH 244520208 908412584 72 ADA_OBJECTS_PATH 109 adafin l s Dessel 89 105 adainit cielncsecss nu em eem ted 83 105 ati NES 14356 es ive eri nl BER bee 26 AnfexA seas bee step ana 283 Annex Bil a e deus 283 Arbitrary File Naming Conventions 133 ASM 7450436 elt gk ha glee hates San E E ERE 29 ASSert rr td eSI eve ES 51 AssertionS n enneunen c cece eee eee 51 Binder consistency checks 103 Binder output file 28 Binder multiple input files 105 Breakpoints and tasks 279 Conan a oer Ee pe Yt AP ea ee 29 nap 29 Calling Conventions 28 Check elaboration 61 Check overflowW 60 Check CPU procedure 304 Checks access before elaboration 60 Check
298. nd are legal then the project file defines a library project Theoptional library related attributes are checked only for such project files TheLibrary Kind attribute has a string valuethat must be one of the following case insensitive Static dynamic Of relocatable If this attribute is not specified the library is a static library Otherwise the library may be dynamic or relocatable Depending on the operating system there may or may not be a distinction between dynamic and relocatable libraries For example on Unix there is no such distinction The Library Version attribute has a string value whose inter pretation is platform dependent On Unix it is used only for dy namic relocatable libraries as the internal name of the library the soname If the library file name built from the Library Name is different from the Library Version then the library file will be a sym bolic link to the actual file whose name will be Library Version Example on Unix 164 SSS 28 May 2002 body Chapter 10 GNAT Project Manager project Plib is Version 1 for Library_Dir use lib_dir for Library_Name use dummy for Library_Kind use relocatable for Library_Version use libdummy so amp Version end Plib Directory lib dir will contain the internal library file whose name will be Libdummy so 1 and libdummy so will be a symbolic link to libdummy so 1 When gnatmake detects that a project fi
299. nes only the compiler package The Ada package syntax is not to be taken literally Although pack ages in project files bear a surface resemblance to packages in Ada source code the notation is simply a way to convey a grouping of properties for a named entity Indeed the package names permitted in project files are restricted to a predefined set corresponding to the project aware tools and the contents of packages are limited to a small set of constructs The packages in the example above contain attribute definitions Specifying Switch Settings Switch settings for a project aware tool can be specified through at tributes in the package corresponding to the tool The example above illustrates one of the relevant attributes Default Switches defined in the packages in both project files Unlikesimple attributes like source _ Dirs Default Switches is known as an associative array When you define this attribute you must supply an index a literal string and the effect of the attribute definition is to set the value of the array at the specified index For the Default Switches attribute the index is a programming language in our case Ada and the value specified after use must be a list of string expressions The attributes permitted in project files are restricted to a predefined set Some may appear at project level others in packages For any attribute that is an associate array the index must always be a literal string
300. ng Latin 1 is an 8 bit code that includes the familiar 7 bit ASCII set plus additional characters used for representing foreign languages see Section 2 2 Foreign Language Representation page 16 for support of non USA character sets The format effector characters are repre sented using their standard ASCII encodings as follows VT Vertical tab 16 0B HT Horizontal tab 16 09 CR Carriage return 16 0D LF Line feed 16 0A FF Form feed 16 0C Source files are in standard text file format In addition GNAT will recognize a wide variety of stream formats in which the end of physical physical lines is marked by any of the following sequences LF CR CR LF or LF cR This is useful in accommodating files that are imported from other operating systems The end of a source file is normally represented by the physical end of file However the control character 16 1A suB is also recognized as signalling the end of the source file Again this is provided for compati bility with other operating systems where this code is used to represent the end of file Each file contains a single Ada compilation unit including any prag mas associated with the unit For example this means you must place a package declaration a package spec and the corresponding body in separate files An Ada compilation which is a sequence of compilation GNAT User s Guide for Unix Platforms units is represented using a sequence of files Similarly y
301. nit Subprogram Name a simple or expanded name of a subprogram declared within this compilation unit The effect of an Eliminate pragma placed in the GNAT configuration file gnat adc is e f the subprogram Subprogram Name is declared within the library unit Library Unit Name thecompiler will not generate codefor this subprogram This applies to all overloaded subprograms denoted by Subprogram Name 261 GNAT User s Guide for Unix Platforms e fasubprogram marked by the pragma Eliminate is Used called in a program the compiler will produce an error message in the place where it is called 21 3 Tree Files A tree file stores a snapshot of the compiler internal data structures at the very end of a successful compilation It contains all the syntactic and semantic information for the compiled unit and all the units upon which it depends semantically To use tools that make use of tree files you need to first produce the right set of tree files GNAT produces correct tree files when gnatt gnatc options are set in a gcc call The tree files have an adt extension Therefore to produce a tree file for the compilation unit contained in a file named foo adb you must use the command gcc c gnatc gnatt foo adb and you will get the tree file oo aat compilation 21 4 Preparing Tree and Bind Files for gnatelim A set of tree files covering the program to be analyzed with gnatelim and the bind file for the main subp
302. nly be called if the CPUID instruction is supported function Vendor_ID return String return the processor vendor identification string can only be called if the CPUID instruction is supported function Signature return Processor_Signature return the processor signature can only be called if the CPUID instruction is supported function Features return Processor_Features return the processors features can only be called if the CPUID instruction is supported private ID_Flag constant Num_Bits 21 ID flag bit end Intel_CPU 319 GNAT User s Guide for Unix Platforms 24 7 3 Intel cPU Package Body 320 package body Intel CPU is There is a FPU present if we can set values to the FPU Status and Control Words function Has FPU return Boolean is Register Unsigned 16 processor register to store a word begin check if we can change the status word Asm the assembler code finit amp LF amp HT amp reset status word movw 0x5A5A A ax amp LF amp HT amp set value status word fnstsw 40 amp LF HT amp save status word movw W4Aax 40 store status word output stored in Register register must be a memory location Outputs gt Unsigned 16 Asm output m Register tell compiler that we used eax Clobber gt eax if the status word is zero there is no FPU if Register O then return False no status word end
303. ns _increment__incr 1 subl 4 esp movl 8 esp eax APP incl eax NO_APP movl eax edx movl ecx hesp addl 4 esp ret 24 5 Inlining Inline Assembler Code For a short subprogram such as the Incr function in the previous section the overhead of the call and return creating deleting the stack frame can be significant compared to the amount of code in the subprogram body A solution is to apply Ada s Inline pragma to the subprogram which directs the compiler to expand invocations of the subprogram at the point s of call instead of setting up a stack frame for out of line calls Here is the resulting program 301 GNAT User s Guide for Unix Platforms with Interfaces use Interfaces with Ada Text I0 use Ada Text IO with System Machine Code use System Machine Code procedure Increment 2 is function Incr Value Unsigned 32 return Unsigned 32 is Result Unsigned 32 begin Asm incl 40 Inputs gt Unsigned 32 Asm Input a Value Outputs gt Unsigned 32 Asm Output a Result return Result end Incr pragma Inline Increment Value Unsigned 32 begin Value 5 Put Line Value before is amp Value Img Value Increment Value Put Line Value after is amp Value Img end Increment 2 Compile the program with both optimization 02 and inlining en abled
304. ns The name is formed by taking the full expanded name of the unit and replacing the separating dots with hyphens and using lowercase for all letters except that a hyphen in the second character position is replaced by a tilde if the first character is a i g or s The extension is ads for a specification and adb for a body Krunching does not affect the extension but the file name is shortened to the specified length by following these rules e Thename is divided into segments separated by hyphens tildes or underscores and all hyphens tildes and underscores are eliminated If this leaves the name short enough we are done e If the name is too long the longest segment is located left most if there are two of equal length and shortened by dropping its last character This is repeated until the name is short enough As an example consider the krunching of our strings wide_fixed adb to fit the name into 8 characters as required by some operating systems our strings wide_fixed 22 our strings wide fixed 19 our string wide fixed 18 our strin wide fixed 17 our stri wide fixed 16 our stri wide fixe 15 our str wide fixe 14 our str wid fixe 13 our str wid fix 12 ou str wid fix 11 ou st wid fix 10 ou st wi fix 9 ou st wi fi 8 Final file name oustwifi adb e Thefile names for all predefined units are always krunched to eight characters Thekrunching of these predefined units uses the follow ing special prefix replacem
305. nsibility of the programmer to make sure that the re sulting program has no elaboration anomalies The pragma Suppress Elaboration Check can be used with different granularity to suppress warnings and break elaboration cir cularities e Placethe pragma that names the called subprogram in the dedarative part that contains the call e Placethe pragma in the dedarative part without nam ing an entity This disables warnings on all calls in the corresponding declarative region e Place the pragma in the package spec that declares the called subprogram and name the subprogram This dis ables warnings on all elaboration calls to that subpro gram e Place the pragma in the package spec that declares the called subprogram without naming any entity This 201 GNAT User s Guide for Unix Platforms disables warnings on all elaboration calls to all subpro grams declared in this spec These four cases are listed in order of decreasing safety and therefore require increasing programmer care in their appli cation Consider the following program package Pack1 is function F1 return Integer X1 Integer end Pack1 package Pack2 is function F2 return Integer function Pure x integer return integer pragma Suppress Elaboration_Check On gt Pure 3 pragma Suppress Elaboration_Check 4 end Pack2 with Pack2 package body Pack1 is function Fi return Integer is begin return 100 end F1 Val integ
306. nstead of names and the with clause identifies project files rather than packages Each literal string is the file name or path name absolute or relative of a project file If a string is simply a file name with no path then its location is determined by the project path e If the environment variable ADA PROJECT PATH exists then the project path includes all the directories in this environment vari able plus the directory of the project file e f the environment variable ADA PROJECT PATH does not exist then the project path contains only one directory namely the one where the project file is located If a relative pathname is used as in with tests proj then the path is relative to the directory where the importing project file is located Any symbolic link will be fully resolved in the directory of the importing project file before the imported project file is looked up When the with ed project file name does not have an extension the default is gpr If a file with this extension is not found then the file name as specified in the with dause no extension will be used In the above example if a file project1 gpr is found then it will be used otherwise if a file project1 exists then it will be used if neither file exists this is an error A warning is issued if the name of the project file does not match the name of the project this check is case insensitive Any source file that is an immediate source of
307. nt Version 32 u00020 constant Version 32 u00021 constant Version 32 u00022 constant Version 32 u00023 constant Version 32 16 7880BEB3 16 0D24CBDO 16 3283DBEB 16 2359F9ED 16 664FB847 16 68E803DF 16 5572E604 16 46B173D8 16 156A40CF 16 033DABE0 16 6AB38FEA 16 22B6217D 16 68A22947 16 18CC4A56 16 08258E1B 16 367D5222 16 20C9ECA4 16 50D32CB6 16 39A8BB77 16 5CF8FA2B 16 2F 1EB794 16 31AB6444 16 1574B6E9 23 May 2002 u00024 u00025 u00026 u00027 u00028 u00029 u00030 u00031 u00032 u00033 u00034 u00035 u00036 u00037 u00038 u00039 u00040 u00041 u00042 u00043 u00044 u00045 u00046 u00047 u00048 u00049 u00050 u00051 u00052 u00053 u00054 u00055 u00056 u00057 The following constant constant constant constant constant constant constant constant constant constant constant constant constant constant constant constant constant constant constant constant constant constant constant constant constant constant constant constant constant constant constant constant constant constant with symbolic for spec so Chapter 4 Binding Using gnatbind Version 32 16 5109C189 Version_32 16 56D770CD Version 32 16 02F9DE3D Version 32 16 08AB6B2C Version 32 16 3FA37670 Version 32 16 476457A0 Version 32 16 73
308. ntel CPU Vendor ID Intel CPU Intel Processor then Ada Text IO Put Line xxx This is a Intel compatible processor Ada Text IO Put Line xxx Some information may be incorrect end if check if Intel With the CPUID instruction present we can assume at least a x486 processor If the CPUID support level is lt 1 then we have to leave it at that if Intel_CPU CPUID_Level lt 1 then 23 May 2002 Chapter 24 Inline Assembler Ok this is a x486 processor we still can get the Vendor ID Ada Text_I0 Put_Line x486 type processor Ada Text_I0 Put_Line Vendor ID is amp Intel CPU Vendor ID We can also check if there is a FPU present if Intel_CPU Has_FPU then Ada Text_I0 Put_Line Floating Point support else Ada Text_I0 Put_Line No Floating Point support end if check for FPU Program done Ada Command_Line Set_Exit_Status Ada Command_Line Success return end if check CPUID level With a CPUID level of 1 we can use the processor signature to determine it s exact type Signature Intel_CPU Signature Ok now we go into a lot of messy comparisons to get the processor type For clarity no attememt to try to optimize the comparisons has been made Note that since Intel_CPU does not support getting cache info we cannot distinguish between P5 and Celeron types yet 307 GNAT User s Guide for Unix Platforms x486SL if Signature Pro
309. ntions used to generate link names from the Ada entity names All link names are in all lowercase letters With the exception of library procedure names the mechanism used is simply to use the full expanded Ada name with dots replaced by double underscores For example suppose we have the following package spec package QRS is MN Integer end QRS The variable ww has a full expanded Ada name of ors mn so the corre sponding link name is qrs__mn Of course if a pragma Export is used this may be overridden package Exports is Vari Integer pragma Export Vari C External Name gt vari name Var2 Integer pragma Export Var2 C Link Name gt var2 link name end Exports In this case the link name for var is whatever link name the C com piler would assign for the C function vari name This typically would be either vari name Of vari name depending on operating system conventions but other possibilities exist The link name for var2 is var2 link name andthis is not operating system dependent One excepti on occurs for library level procedures A potential ambigu ity arises between the required name mainfor the C main program and the name we would otherwise assign to an Ada library level procedure called main which might well not be the main program To avoid this ambiguity we attach the prefix aaa to such names So if we have a library level procedure such as procedure Hello S String
310. nvironment for compiling checking running and debugging applications you may be using adp files to give the directories where Emacs can find sources and object files Using this switch you can tell gnathtml to use these files This allows you to get an html version of your application even if it is spread over multiple directories This option allows you to change the color used for symbol definitions The default valueis red The color argument can be any name accepted by html This switch provides the name of a file This file contains a list of file names to be converted and the effect is exactly as though they had appeared explicitly on the command line This is the recommended way to work around the command linelength limit on some systems 22 6 Installing gnathtm1 Perl needs to be installed on your machine to run this script Perl is freely available for almost every architecture and Operating System via the Internet On Unix systems you may want to modify the first line of the scri pt gnathtml to explicitly tell the Operating system where Perl is The syntax of this lineis tt full path name to perl Alternatively you may run the script using the following command line perl gnathtml pl switches files 271 GNAT User s Guide for Unix Platforms 2Q2J um Vv V vc cK C OeOC cC c rc mCc vc C rr OYAmn T 7 28 May 2002 Chapter 23 Running and Debugging Ada P
311. o be turned on using gnatwa e Assignment of an item to itself e Type conversion that converts an expression to its own type e Useofthe attribute Base where typ Base iS the same as typ e Useof pragma Pack when all components are placed by a record representation clause gnatwR suppress warnings on redundant constructs This switch suppresses warnings for redundant constructs gnatws suppress all warnings This switch completely suppresses the output of all warning messages from the GNAT front end Note that it does not suppress warnings from the gcc back end To suppress these back end warn ings as well use the switch w in addition to gnatws gnatwu activate warnings on unused entities This switch activates warnings to be generated for entities that are defined but not referenced and for units that are with ed and not referenced In the case of packages a warning is also gen erated if no entities in the package are refer enced This means that if the package is refer enced but the only references are in use dauses Or renames dedarations a warning is still gener ated A warning is also generated for a generic package that is with ed but never instantiated In the case where a package or subprogram body is compiled and there is a witn on the corre sponding spec that is only referenced in the body a warningis also generated noting that the with 50 m 8 May 2002 Chapter 3 Compiling Using g
312. o create the tree file needed to create a body sampler unless t option is set Verbose mode generate version information 23 May 2002 Chapter 21 Reducing the Size of Ada Executables with gnatelim 21 Reducing the Size of Ada E xecutables with gnatelim 21 1 About gnatelim When a program shares a set of Ada packages with other programs it may happen that this program uses only a fraction of the subprograms defined in these packages The code created for these unused subpro grams increases the size of the executable gnatelimtracks unused subprograms in an Ada program and outputs a list of GNAT specific Eliminate pragmas see next section marking all the subprograms that are declared but never called By placing the list of Eliminate pragmas in the GNAT configuration file gnat adc and recompiling your program you may decrease the size of its executable because the compiler will not generate the code for eliminated subpro grams gnatelim needs as its input data a set of tree files see Section 21 3 Tree Files page 262 representing all the components of a program to process and a bind file for a main subprogram see Section 21 4 Prepar ing Tree and Bind Files for gnatelim page 262 21 2 Eliminate Pragma The simplified syntax of the Eliminate pragma used by gnatelimis pragma Eliminate Library_Unit_Name Subprogram_Name where Library Unit Name full expanded Ada name of a library u
313. o represent the program internally But tree nodes are represented simply by an integer value which in turn is an index into a table of nodes Using the print command on a tree node would simply print this integer value which is not very useful But the PN routine defined in file treepr adb in the GNAT sources takes a tree node as input and displays a useful high level representation of the tree node which includes the syntactic category of the node its position in the source the integers that denote descendant nodes and parent node as well as varied semantic information To study this example in more detail you might want to look at the body of the PN procedure in the stated file 23 6 Using the Next Command in a Function When you use the next command in a function the current source loca tion will advance to the next statement as usual A special case arises in the case of a return Statement Part of the code for a return statement is the epilog of the func tion This is the code that returns to the caller There is only one copy of this epilog code and it is typically associated with the last return statement in the function if there is more than one return In some implementations this epilog is associated with the first statement of the function The result is that if you use the next command from a return state ment that is not the last return statement of the function you may see a strange apparent jump to the last retu
314. o the package project Proj is for Source Dirs use package gnatls is for Switches use a v end gnatls package Binder is for Default Switches Ada use C e end Binder package Linker is for Default Switches Ada use C end Linker package Finder is for Default Switches Ada use a f end Finder package Cross Reference is for Default Switches Ada use a f d u end Cross Reference end Proj With the above project file commands such as 171 GNAT User s Guide for Unix Platforms gnat ls Pproj main gnat xref Pproj main gnat bind Pproj main ali will set up the environment properly and invoke the tool with the switches found in the package corresponding to the tool 10 13 3 Glide and Project Files Glide will automatically recognize the gpr extension for project files and will convert them to its own internal format automatically H owever it doesn t provide a syntax oriented editor for modifying these files The project file will be loaded as text when you select the menu item ada gt Project gt Edit You can edit this text and save the gpr file when you next select this project file in Glide it will be automatically reloaded 10 14 An Extended Example Suppose that we have two programs prog1 and prog2 with the sources in the respective directories We would like to build them with a single gnatmake command and we would l
315. ocedure calls or for declaring local vari ables in declare blocks do not exceed the available stack space If the space is exceeded then a Storage_Error exception is raised For declared tasks the stack size is always controlled by the size given in an applicablestorage size pragma or is set to the default size if no pragma is used For the environment task the stack size depends on system defaults and is unknown to the compiler The stack may even dynamically grow on some systems precluding the normal Ada semantics for stack over flow In the worst case unbounded stack usage causes unbounded stack expansion resulting in the system running out of virtual memory Thestack checking may still work correctly if a fixed size stack is allo cated but this cannot be guaranteed To ensure that a clean exception is signalled for stack overflow set the environment variable GNAT STACK _ LIMIT to indicate the maximum stack area that can be used as in SET GNAT_STACK_LIMIT 1600 The limit is given in kilobytes so the above dedaration would set the stack limit of the environment task to 1 6 megabytes Note that the only purpose of this usage is to limit the amount of stack used by the environment task If it is necessary to increase the amount of stack for the environment task then this is an operating systems issue and must be addressed with the appropriate operating systems commands 3 2 7 Run Time Control gnatT nnn Thegnatt switch ca
316. of arguments presented tothe linker 111 GNAT User s Guide for Unix Platforms 5 2 Switches for gnatlink The following switches are available with the gnat link utility A C The binder has generated code in Ada This is the default If instead of generating a file in Ada the binder has gener ated one in C then thelinker needs to know aboutit Usethis switch to signal to gnat1ink that the binder has generated C code rather than Ada code On some targets the command line length is limited and gnatlink Will generate a separate file for the linker if the list of object files is too long The flag forces this file to be generated even if the limit is not exceeded This is useful in some cases to deal with special situations where the command line length is exceeded The option to indude debugging information causes the Ada bind file in other words b mainprog adb to be com piled with g In addition the binder does not delete the b mainprog adb b mainprog o and b mainprog ali files Without g the binder removes these files by default The same procedure apply if a C bind file was generated using C gnatbind option in this case the filenames are b mainprog c and b_mainprog o Do not compile the file generated by the binder This may be used when a link is rerun with different options but there is no need to recompile the binder file Causes additional information to be output induding
317. of the features it supports lt with Intel_CPU Intel CPU detection functions with Ada Text_I0 Standard text I 0 with Ada Command_Line To set the exit status procedure Check_CPU is Type_Found Boolean False Flag to indicate that processor was identified Features Intel_CPU Processor_Features The processor features Signature Intel_CPU Processor_Signature The processor type signature Ada Text IO Put Line Ada Command_Line Command_Name amp check Intel CPU version and features v1 0 Ada Text IO Put Line distribute freely but no warranty whatsoever Ada Text IO New Line We can safely start with the assumption that we are on at least a x386 processor If the CPUID instruction is present then we have a later processor type if Intel CPU Has CPUID False then 305 GNAT User s Guide for Unix Platforms No CPUID instruction so we assume this is indeed a x386 processor We can still check if it has a FP co processor if Intel_CPU Has_FPU then Ada Text_I0 Put_Line x386 type processor with a FP co processor else Ada Text_I0 Put_Line x386 type processor without a FP co processor end if check for FPU Program done Ada Command_Line Set_Exit_Status return end if check for CPUID Ada Command Line Success If CPUID is supported check if if it is not display a warning this is a true Intel processor if I
318. ompilation In particular e When a unit is with ed the unit seen by the compiler corresponds to the source version of the unit that is currently accessible to the compiler e Inlining requires the appropriate source files for the package or subprogram bodies to beavailabletothe compiler Inliningis always effective independent of the order in which units are complied e Compiling a unit never affects any other compilations The editing of sources may cause previous compilations to be out of date if they depended on the source file being modified The most important result of these differences is that order of compila tion is never significant in GNAT There is no situation in which one is required to do one compilation before another What shows up as order of compilation requirements in the traditional Ada library becomes in GNAT simple source dependencies in other words there is only a set of rules saying what source files must be present when a fileis compiled 36 28 May 2002 Chapter 3 Compiling Using gcc 3 Compiling Using gcc This chapter discusses how to compile Ada programs using the gcc com mand It also describes the set of switches that can be used to control the behavior of the compiler 3 1 Compiling Programs The first step in creating an executable program is to compile the units of
319. omprise three sets in the following order 1 the applicable switches contributed for the file by the Builder pack age in the project file supplied on the command line 2 those contributed for the file by the package in the relevant project file see below corresponding to the tool and 3 the applicable switches passed on the command line The term applicable switches reflects the fact that gnatmake switches may or may not be passed toindividual tools depending on the individual Switch gnatmake may invoke the compiler on source files from different projects The Project Manager will use the appropriate project file to determine the compiler package for each source file being compiled Likewise for the Binder and Linker packages As an example consider the following package in a project file project Proj1 is package Compiler is for Default_Switches Ada use g for Switches a adb use 01 for Switches b adb use 02 gnaty end Compiler end Proj1 If gnatmake iS invoked with this project file and it needs to compile say the files a adb b adb and c adb then a adb will be compiled with the switch 01 b adb with switches 02 and gnaty and c adb with g 167 GNAT User s Guide for Unix Platforms Another example illustrates the ordering of the switches contributed by different packages project Proj2 is package Builder is for Switches main adb
320. on 3 3 Search Paths and the Run Time Library RTL page 71 Except for the source file named in the command line do not look for source files in the directory containing the source file named in the command line see Section 3 3 Search Paths and the Run Time Library RTL page 71 This switch is used in gcc to redirect the generated object file and its associated ALI file Beware of this switch with GNAT because it may cause the object file and ALI file to have different names which in turn may confuse the binder and the linker n controls the optimization level n 0 No optimization the default setting if no o ap pears n 1 Normal optimization the default if you specify o without an operand Extensive optimization n 3 Extensive optimization with automatic inlining This applies only to inlining within a unit For details on control of inter unit inlining see See Section 3 2 13 Subprogram Inlining Control page 66 N RTS rts path V ver gnata gnatA Specifies the default location of the runtime library Same meaning as the equivalent gnatmake flag see Section 6 2 Switches for gnatmake page 116 Used in place of c to cause the assembler source file to be generated using s as the extension instead of the object file This may be useful if you need to examine the generated assembly code Show commands generated by the acc driver Normally used only for debugging purpos
321. on Pragmas page 132 GNAT allows completely arbitrary file names to be specified using the source file name pragma However if the file name specified has an extension other than ads or adb it is necessary to usea special syntax when compiling the file The name in this case must be preceded by the special sequence x followed by a space and the name of the language here ada as in gcc c x ada peculiar file name sim gnatmake handles non standard file names in the usual manner the non standard file namefor the main program is simply used as the argument to gnatmake Note that if the extension is also non standard then it must be induded in the gnatmake command it may not be omitted 2 5 Alternative File Naming Schemes Intheprevious section wedescribed theuseof thesource File Name pragma to allow arbitrary namesto beassigned to individual source files However this approach requires one pragma for each file and especially in large systems can result in very long anat adc files and also create a maintenance probl em GNAT also provides a facility for specifying systematic file naming schemes other than the standard default naming scheme previously de scribed An alternative scheme for naming is specified by the use of Source File Name pragmas having the following format pragma Source File Name Spec File Name gt FILE NAME PATTERN Casing gt CASING_SPEC Dot_Replacement gt STRING_LITERAL
322. on the use of the GNU source l evel debugger e GNU Emacs Manual contains full information on the extensible editor and programming environment E macs Conventions Following are examples of the typographical and graphic conventions used in this guide e Functions utility program names standard names and classes e Option flags e File Names button names and field names e Variables e Emphasis e optional information or parameters e Examples are described by text and then shown this way Commands that are entered by the user are preceded in this manual by the characters s dollar sign followed by space If your system uses this sequence as a prompt then the commands will appear exactly as GNAT User s Guide for Unix Platforms you see them in the manual If your system uses some other prompt then the command will appear with the replaced by whatever prompt character you are using A m gt g qQ Q O UO e8 May 2002 Chapter 1 Getting Started with GNAT 1 Getting Started with GNAT This chapter describes some simple ways of using GNAT to build exe cutable Ada programs 1 1 Running GNAT Three steps are needed to create an executable file from an Ada source file 1 The source file s must be compiled 2 The file s must be bound using the GNAT binder 3 All appropriate object files must be linked to produce an executable All three steps are most commonly handled
323. one in exp_ch3 adb e The files prefixed with bind implement the binder which verifies the consistency of the compilation determines an order of elabora tion and generates the bind file e Thefiles atree ads and atree adb detail the low level data struc tures used by the front end e The files sinfo ads and sinfo adb detail the structure of the abstract syntax tree as produced by the parser e The files einfo ads and einfo adb detail the attributes of all entities computed during semantic analysis e Library management issues are dealt with in files with prefix lib e Ada files with the prefix a are children of Aaa as defined in Annex A e Files with prefix i arechildren of Interfaces as defined in Annex B e Files with prefix s are children of system This indudes both language defined children and GNAT run time routines e Files with prefix g are children of Nat These are useful general purpose packages fully documented in their specifications All the other c files are modifications of common gcc files 23 12 Getting Internal Debugging Information Most compilers have internal debugging switches and modes GNAT does also except GNAT internal debugging switches and modes are not secret A summary and full description of all the compiler and binder debug flags are in the file ebug adb You must obtain the sources of the compiler to see the ful
324. ons are c compile only no bind or link S generate assembler listing fomit frame pointer do not set up separate stack frames gnatp do not add runtime checks This gives a human readable assembler version of the code The resulting file will have the same name as the Ada source file but with a s extension In our example the file nothing s has the following contents file nothing adb gcc2 compiled ___gnu_compiled_ada text align 4 globl ada nothing APP nop NO_APP jmp Li align 2 0x90 Li ret The assembly code you included is clearly indicated by the compiler between the 4APP and No_app delimiters The character before the APP and NOAPP can differ on different targets For example Linux uses ZAPP while on NT you will see APP If you make a mistake in your assembler code such as using the wrong size modifier or using a wrong operand for the instruction GNAT will report this error in a temporary file which will be deleted when the compilation is finished Generating an assembler file will help in such ada nothing 295 GNAT User s Guide for Unix Platforms cases since you can assemblethis file separately using the as assembler that comes with gcc Assembling the file using the command as nothing s will give you error messages whose lines correspond to the assembler input file so you can easily find and correct any mistakes you made If there are no errors
325. ote that there is no specific option to test out parameters but any reference within the subprogram will betested in the usual manner and if an invalid value is copied back any reference to it will be subject to validity checking e gnatVo Validity checks for operator and attribute operands Arguments for predefined operators and attributes are validity checked This includes all operators in package standard the shift operators defined as intrinsic in package Interfaces and operands for attributes such as Pos e gnatvr Validity checks for function returns The expression in return statements in functions is validity checked e gnatVs Validity checks for subscripts All subscripts expressions are checked for validity whether they appear on the right side or left side in default mode only left side subscripts are validity checked e gnatvt Validity checks for tests Expressions used as conditions in i while Or exit statements are checked as well as guard expressions in entry calls e gnatVf Validity checks for floating point values In the absence of this switch validity checking occurs only for dis crete values If gnatvt is specified then validity checking also applies for floating point values and NaN s and infinities are con sidered invalid as well as out of range values for constrained types Note that this means that standard IEEE infinity mode is not al lowed Theexact contexts in which floating point values are checked
326. otential elaboration problem e Split library tasks into separate packages Write separate packages so that library tasks are isolated from other declarations as much as possible Let us look at a variation on the above program package Decls1 is task Lib_Task is entry Start end Lib_Task end Decls1 with Utils package body Decls1 is task body Lib_Task is begin accept Start Utils Put_Val 2 end Lib_Task end Decls1 package Decls2 is type My_Int is new Integer function Ident M My Int return My Int end Decls2 195 GNAT User s Guide for Unix Platforms with Utils package body Decls2 is function Ident M My_Int return My_Int is begin return M end Ident end Decls2 with Decls2 package Utils is procedure Put_Val Arg Decls2 My_Int end Utils with Text I0 package body Utils is procedure Put Val Arg Decls2 My Int is begin Text IO Put Line Decls2 My_Int Image Decls2 Ident Arg end Put Val end Utils with Declsi procedure Main is begin Decls1 Lib_Task Start end All we have done is to split Dec1s into two packages one containing the library task and one containing everything else Now there is no cyde and the program compiles binds links and executes using the default static model of elaboration e Dedare separate task types A significant part of the problem arises because of the use of the single task declaration form This means that the elaboration of the
327. ou will place each subunit or child unit in a separate file 2 2 Foreign Language Representation GNAT supports the standard character sets defined in Ada 95 as well as several other non standard character sets for use in localized versions of the compiler see Section 3 2 11 Character Set Control page 64 2 2 1 Latin 1 The basic character set is Latin 1 This character set is defined by ISO standard 8859 part 1 The lower half character codes 16 00 16 7F is identical to standard ASCII coding but the upper half is used to represent additional characters These include extended letters used by European languages such as French accents the vowels with umlauts used in German and the extra letter A ring used in Swedish For a complete list of Latin 1 codes and their encodings see the source file of library unit Ada Characters Latin_1in file a chlat1 ads You may use any of these extended characters freely in character or string literals In addition the extended characters that represent letters can be used in identifiers 2 2 2 Other 8 Bit Codes GNAT also supports several other 8 bit coding schemes Latin 2 Latin 2 letters allowed in identifiers with uppercase and lowercase equivalence Latin 3 Latin 3 letters allowed in identifiers with uppercase and lowercase equivalence Latin 4 Latin 4 letters allowed in identifiers with uppercase and lowercase equivalence Latin 5 Latin 4 letters Cyrillic
328. ource Combines the above two cases x y x mod y x y x rem y A division or multiplication of fixed point values which are treated as integers without any kind of scaling free expr storage_pool xxx Shows the storage pool associated with a free statement 23 May 2002 Chapter 3 Compiling Using gcc freeze typename actions Shows the point at which typename is frozen with possible associated actions to be performed at the freeze point reference itype Reference and hence definition to internal type itype function name arg arg arg Intrinsic function call labelname label Dedaration of label 1abeiname expr amp amp expr amp amp expr amp amp expr A multiple concatenation same effect as expr amp expr amp expr but handled more efficiently constraint error Raisethe constraint Error exception expression reference A pointer tothe result of evaluating expression target type source expression An unchecked conversion of source expression to target type numerator denominator Used to represent internal real literals that have no exact representation in base 2 16 for example the result of compile time evaluation of the expression 1 0 27 0 gnatD This switch is used in conjunction with gnatG to cause the expanded source as described above to be written to files with names xxx dg where xxx is the normal file name for example if the source file name is
329. ovided no compilation copyright is daimed for the compilation Such a compilation is called an aggregate and this License does not apply to the other self contained works thus compiled with the Document on account of their being thus compiled if they are not themselves derivative works of the Document If the Cover Text requirement of section 3 is applicable to these copies of the Document then if the Document is less than one quarter of the entire aggregate the Document s Cover Texts may be placed on covers that surround only the Document within the aggregate Otherwise they must appear on covers around the whole aggregate 338 83 May 2002 Appendix A GNU Free Documentation License 8 TRANSLATION Translation is considered a kind of modification so you may distribute translations of the Document under the terms of section 4 Replacing Invariant Sections with translations requires special permission from their copyright holders but you may include translations of some or all Invariant Sections in addition to the original versions of these Invariant Sections You may include a translation of this License provided that you also include the original English version of this License In case of a disagreement between the translation and the original English version of this License the original English version will prevail 9 TERMINATION You may not copy modify sublicense or distribute the Document ex cept as expressly provided fo
330. package Proj4 Builder and gnato passed on the command line When the imported package Pack is compiled the switches used are g from Proj4 Builder gnata contributed from package Proj3 Compiler and gnato from the command line 10 13 1 2 Project Files and Main Subprograms When using a project file you can invoke gnatmake with several main subprograms by specifying their source files on the command line Each of these needs to be an immediate source file of the project gnatmake Pprj maini main2 main3 When usinga project file you can alsoinvoke gnatmake without explicitly specifying any main and the effect depends on whether you have defined the Main attribute This attribute has a string list value where each element in the list is the name of a source file the file extension is optional containing a main subprogram If the Main attribute is defined in a project file as a non empty string list and the switch u is not used on the command line then invoking gnatmake With this project file but without any main on the command line is equivalent to invoking gnatmake with all the file names in the Main attribute on the command line Example project Prj is for Main use maini main2 main3 end Prj With this project file gnatmake Pprj is equivalent to gnatmake Pprj mainl main2 main3 When the project attribute Main is not specified or is specified as an empty string list or when the swit
331. pears in the string after gnaty then pragma names must be written in mixed case that is theinitial letter and any letter following an underscore must be uppercase All other letters must be lowercase r check references If the letter r appears in the string after gnaty then all identifier references must be cased in the same way as the 58 8 May 2002 Chapter 3 Compiling Using scc corresponding declaration No specific casing style is im posed on identifiers The only requirement is for consistency of references with declarations s check separate specs If theletter s appearsinthestring after gnaty then separate declarations specs are required for subprograms a body is not allowed to serve as its own declaration The only exception is that parameterless library level procedures are not required to have a separate declaration This exception covers the most frequent form of main program procedures t check token spacing If the letter t appears in the string after gnaty then the following token spacing rules are enforced e Thekeywords abs and not must be followed by a space e Thetoken gt must be surrounded by spaces e Thetoken lt gt must be preceded by a space or a left paren thesis e Binary operators other than must be surrounded by spaces There is no restriction on the layout of the binary operator e Colon mu
332. pec main adb Main body arith functions ads Arith_F unctions package spec arith functions adb Arith_F unctions package body unc spec ads Func Spec child package spec unc spec adb Func Spec child package body main sub adb Sub subunit of Main a bad adb A Bad child package body 19 GNAT User s Guide for Unix Platforms Following these rules can result in excessively long file names if corre sponding unit names are long for example if child units or subunits are heavily nested An option is available to shorten such long file names called file name krunching This may be particularly useful when programs being developed with GNAT are to be used on operating sys tems with limited file name lengths See Section 13 2 Using gnatkr page 221 Of course no file shortening algorithm can guarantee uniqueness over all possible unit names if file name krunching is used it is your responsibility to ensure no name clashes occur Alternatively you can specify the exact file names that you want used as described in the next section Finally if your Ada programs are migrating from a compiler with a different naming convention you can use the gnatchop utility to produce source files that follow the GNAT naming conventions For details see Chapter 7 Renaming Files Using gnatchop page 125 2 4 Using Other File Names In the previous section we have de
333. portant that the link command has access to the proper gcc library 1ibgcc a that is to say the one that is part of the C compiler installation The implicit link command as suggested in the gnatmake command from the former example can be replaced by an explicit link command with full verbosity in order to verify which library is used gnatbind ada_unit gnatlink v v ada unit filel o file2 o LINK c 31 GNAT User s Guide for Unix Platforms If there is a problem due to interfering environment variables it can be workaround by using an intermediate script The following example shows the proper script to use when GNAT has not been installed at its default location and g has been installed at its default location gnatlink v v ada unit filei o file2 o LINK my script cat my script bin sh unset BINUTILS_ROOT unset GCC_ROOT ctt 3 Using a non GNU C compiler The same set of command as previously described can be used to insure that the c linker is used Nonetheless you need to add the path to libgcc explicitely since some libraries needed by GNAT are located in this directory gnatlink ada unit filei o file2 o LINK my script cat my script bin sh CC gcc print libgcc file name Where CC is the name of the non GNU C compiler 2 11 3 A Simple Example The following example provided as part of the GNAT examples show how to achieve procedural interfacing between Ada and C i
334. r of allo cations that have no corresponding deallocation as shown here for root 2 and root 1 This is anormal behavior when the number of non freed allocations is one it locates dynamic data structures that the run time needs for the complete lifetime of the program Note also that there is only one allocation root in the user program with a single line back trace test gm adb 11 test gm my alloc whereas a careful analysis of the program shows that My Alloc is called at 2 different points in the source line 21 and line 24 If those two allocation roots need to be distinguished the backtrace depth parameter can be used gnatmem 3 test gm which will give the following output Global information Total number of allocations 18 Total number of deallocations i 5 Final Water Mark non freed mem 53 00 Kilobytes High Water Mark 56 90 Kilobytes 251 GNAT User s Guide for Unix Platforms Allocation Root 1 Number of non freed allocations Final Water Mark non freed mem High Water Mark Backtrace test_gm adb 11 test_gm my_alloc test_gm adb 24 test_gm b_test_gm c 52 main Allocation Root 2 Number of non freed allocations Final Water Mark non freed mem High Water Mark Backtrace 10 39 06 Kilobytes 42 97 Kilobytes 1 10 02 Kilobytes 10 02 Kilobytes s secsta adb 81 system secondary_stack ss_init s secsta adb 283 lt system__secondary_stack___elabb gt b_test_gm c 33 adainit Allocation Root 3 Number
335. r the value of the same name in the environment vPX Indicates the verbosity of the parsing of GNAT project files vPo means Default no output for syntactically correct project files vP1 means Medium vp2 means High The default is Default If several vPx switches are present only the last one is used 10 13 Tools Supporting Project Files 10 13 1 gnatmake and Project Files This section covers twotopics related to gnatmake and project files defin ing switches for gnatmake and for the tools that it invokes and the use of the Main attribute 10 13 1 1 Switches and Project Files For each of the packages Builder Compiler Binder and Linker you can specify a Default Switches attribute a Switches attribute or both as their names imply these switch related attributes affect which switches are used for which files when gnatmake is invoked As will be ex plained below these package contributed switches precede the switches passed on the gnatmake command line The Default Switches attribute is an associative array indexed by language name case insensitive and returning a string list For exam ple package Compiler is for Default Switches Ada use gnaty v end Compiler The switches attribute is also an associative array indexed by a file name which may or may not be case sensitive depending on the oper ating system and returning a string list For example package Builder is for Switches
336. r under this License Any other attempt to copy modify sublicense or distribute the Document is void and will automatically terminate your rights under this License However par ties who have received copies or rights from you under this License will not have their licenses terminated so long as such parties remain in full compliance 10 FUTURE REVISIONS OF THIS LICENSE The Free Software Foundation may publish new revised versions of the GNU Free Documentation License from time to time Such new versions will be similar in spirit to the present version but may differ in detail to address new problems or concerns See http www gnu org copyleft Each version of the License is given a distinguishing version number If the Document specifies that a particular numbered version of this Li cense or any later version applies to it you have the option of following the terms and conditions either of that specified version or of any later version that has been published not as a draft by the Free Software Foundation If the Document does not specify a version number of this License you may choose any version ever published not as a draft by the Free Software Foundation 339 GNAT User s Guide for Unix Platforms ADDENDUM How to use this License for your documents To use this License in a document you have written include a copy of the License in the document and put the following copyright and license notices just after the ti
337. re Model Type Found True Ada Text IO Put Line Pentium Pro processor end if Pentium II processor model 3 if Signature Processor Type 2 00 and 2 0110 and 2100114 then Signature Family Signature Model Type Found True Ada Text IO Put Line Pentium II processor model 3 end if Pentium II processor model 5 or Celeron processor if Signature Processor Type 2 00 and 2 0110 and 2101014 then Signature Family Signature Model Type Found True Ada Text IO Put Line Pentium II processor model 5 or Celeron processor end if Pentium Pro OverDrive processor if Signature Processor Type 2 01 and 2 0110 and 21400114 then Signature Family Signature Model Type Found True Ada Text IO Put Line Pentium Pro OverDrive processor end if If no type recognized we have an unknown Display what we do know 23 May 2002 Chapter 24 Inline Assembler if Type_Found False then Ada Text_I0 Put_Line Unknown processor end if if Features FPU True then Ada Text_I0 Put_Line Floating Point unit available else Ada Text_I0 Put_Line no Floating Point unit end if check for FPU Ada Text IO Put Line Supported features Virtual Mode Extension if Features VME True then Ada Text IO Put Line VME Virtual Mode Extension end if 311 GNAT User s Guide for Unix Platforms 312 Debugging Extension if Features DE True
338. re not generated Note that gnatwa does not affect the setting of this warning option gnatwH suppress warnings on hiding This switch suppresses warnings on hiding dec larations gnatwi activate warnings on implementation units This switch activates warnings for a with of an internal GNAT implementation unit defined as any unit from the ada Interfaces GNAT Or System hierarchies that is not documented in either the Ada Reference Manual or the GNAT Programmer s Reference Manual Such units are intended only for internal implementation pur poses and should not be with ed by user pro grams The default is that such warnings are 43 28 May 2002 Chapter 3 Compiling Using gcc generated This warning can also be turned on using gnatwa gnatwI disable warnings on implementation units This switch disables warnings for a witn of an internal GNAT implementation unit gnatwl activate warnings on elaboration pragmas This switch activates warnings on missing pragma Elaborate All statements See the section in this guide on elaboration checking for details on when such pragma should be used The default is that such warnings are not generated This warning can also be turned on using gnatwa gnatwL suppress warnings on elaboration pragmas This switch suppresses warnings on missing pragma Elaborate All s
339. ref and Gravel nd aes ie pui canes iR IUE LE re 209 12 1 gnatxref SWItCchES cc 209 12 2 gnatfindSWItCchES L c 211 12 3 Project Files for gnatxref and gnatfind 213 12 4 Regular Expressions in gnatfind and gnatxref 215 12 5 Examples of gnatxref USaYe 216 12 5 1 General USage 216 12 5 2 Using gnatxref with Vi 218 12 6 Examples of gnat find USaQde 219 13 FileName Krunching Using gnatkr 221 13 1 JDOUE GH ECK xeric an ean AB tus xn DA RR EX LA tate 221 132 USING GEEK es At cool cae a ida ius du SEA 221 13 3 KrunchingMethod 227 egere coe cee nat keane 222 13 4 Examples of gnatkr USaYe 223 14 Preprocessing Usinggnatprep 225 14 1 USINnYJgnatprep 20602444 225 14 2 Switchesforgnatprep 225 14 3 Form of Definitions File 226 14 4 Form of Input Text for gnatprep 226 GNAT User s Guide for Unix Platforms 15 TheGNAT Library Browser gnatls 229 15 1 RUNNINYgnatls 0000404044 229 15 2 Switches Tor gnat Isen ere EE RE sal AO Oe badd xx do 230 15 3 Exampleofgnat1ls USage 231 16 GNAT and Libraries 233 16 1 CreatinganAdaLibrary
340. rence Manual circularity that makes the program illegal 194 28 May 2002 Chapter 11 Elaboration Order Handling in GNAT In practice we have found that problems with the static model of elaboration in existing code often arise from library tasks so we must address this particular situation Note that if we compile and run the program above using the dy namic model of elaboration that is to say use the gnatE switch then it compiles binds links and runs printing the expected result of 2 Therefore in some sense the circularity here is only apparent and we need to capture the properties of this program that distinguish it from other library level tasks that have real elaboration problems We have four possible answers to this question e Use the dynamic model of elaboration If we use the gnatE switch then as noted above the program works Why is this If we examine the task body it is apparent that the task cannot proceed past the accept Statement until after elaboration has been completed because the corresponding entry call comes from the main program not earlier This is why the dynamic model works here But that s really giving up on a precise analysis and we prefer to take this approach only if we cannot solve the problem in any other manner So let us examine two ways to reorganize the program to avoid the p
341. ries it is possible for the system administrator to put those libraries in the default compiler paths To achieve this he must specify their location in the configuration files ada_source_path and ada object path that must be located in the GNAT installation tree at the same place as the gcc spec file The location of the gcc spec file can be determined as follows gcc v The configuration files mentioned above have simple format each linein them must contain one unique directory name Those names are added to the corresponding path in their order of appearance in the file The names can be either absolute or relative in the latter case they are relative to where theses files are located 234 c 28 May 2002 Chapter 16 GNAT and Libraries ada_source_path and ada_object_path might actually not be present in a GNAT installation in which case GNAT will look for its run time library in the directories adainclude for the sources and adalib for the objects and ALI files When the files exist the compiler does not look in adaindude and adalib at all and thus the ada source path file must contain the location for the GNAT run time sources which can simply be adaindude In the same way the ada object path file must contain the location for the GNAT run time objects which can simply be adalib You can also specify
342. rms 136 833 May 2002 Chapter 10 GNAT Project Manager 10 GNAT Project Manager 10 1 Introduction This chapter describes GNAT s Project Manager a facility that lets you configure various properties for a collection of source files In particular you can specify e Thedirectory or set of directories containing the source files and or the names of the specific source files themselves e Thedirectory in which the compiler s output aL1 files object files tree files will be placed e Thedirectory in which the executable programs will be placed e Switch settings for any of the project enabled tools gnatmake com piler binder linker gnat1s gnatxref gnatfind you can apply these settings either globally or to individual units e Thesourcefiles containing the main subprogram s to be built e The source programming language s currently Ada and or C e Sourcefilenaming conventions you can specify these either globally or for individual units 10 1 1 Project Files A project is a specific set of values for these properties You can define a project s settings in a project file a text file with an Ada like syntax a property value is either a string or a list of strings Properties that are not explicitly set receive default values A project file may interrogate the values of external variables user defined command line switches or environment variables and it may specify property settings condition ally based on the va
343. rn statement or to the start of the function You should simply ignore this odd jump Thevaluereturned is always that from the first return statement that was stepped through 23 7 Breaking on Ada Exceptions You can set breakpoints that trip when your program raises selected exceptions break exception Set a breakpoint that trips whenever any task in the pro gram raises any exception break exception name Set a breakpoint that trips whenever any task in the pro gram raises the exception name 278 3 May 2002 Chapter 23 Running and Debugging Ada Programs break exception unhandled Set a breakpoint that trips whenever any task in the pro gram raises an exception for which there is no handler info exceptions info exceptions regexp The info exceptions command permits the user to examine all defined exceptions within Ada programs With a regu lar expression regexp as argument prints out only those exceptions whose name matches regexp 23 8 Ada Tasks GDB allows the following task related commands info tasks This command shows a list of current Ada tasks as in the following example gdb info tasks ID TID P ID Thread Pri State Name 8088000 0 807e000 15 Child Activation Wait main_task 80a4000 1 80ae000 15 Accept Select Wait b 809a800 1 80a4800 15 Child Activation Wait a 80ae800 3 80b8000 15 Running c In this listing the asterisk before the first task indicates it to be the currently running task Thefi
344. rogram does not have to be in the current directory T gnatelim option may be used to provide the search path for tree files and b option may be used to point to the bind file to process see Section 21 5 Running gnatelim page 263 If you do not have the appropriate set of tree files and the right bind file you may create them in the current directory using the following procedure Let Main Prog bethe name of a main subprogram and suppose this subprogram is in a file named main prog adb To create a bind file for gnatelim run gnatbind for the main subpro gram gnatelim can work with both Ada and C bind files when both are present it uses the Ada bind file The following commands will build the program and create the bind file gnatmake c Main Prog gnatbind main prog To create a minimal set of tree files covering the whole program call gnatmake for this program as follows gnatmake f c gnatc gnatt Main Prog 262 28 May 2002 Chapter 21 Reducing the Size of Ada Executables with gnatelim The c gnatmake option turns off the bind and link steps that are useless anyway because the sources are compiled with gnatc option which turns off code generation The f gnatmake option forces recompilation of all the needed sources This sequence of actions will create all the data needed by gnatelim from scratch and therefor
345. rogramming languagename case insensitive whosevalueis a string that must satisfy the following conditions e t must not be empty e t cannot start with an alphanumeric character e t cannot start with an underscore followed by an al phanumeric character If Specification Suffix Ada is not specified then the default is ads Implementation Suffix This is an associative array indexed by the programming language name case insensitive whose valueis a string that must satisfy the following conditions e t must not be empty e t cannot start with an alphanumeric character e t cannot start with an underscore followed by an al phanumeric character e t cannot be a suffix of Specification Suffix If implementation Suffix Ada is not specified then the default is adb Separate Suffix This must be a string whose value satisfies the same condi tions as Implementation Suffix If Separate Suffix Ada is not specified then it defaults to same value as Implementation Suffix Ada Specification You can use the Specification attribute an associative ar ray to definethe source file name for an individual Ada com pilation unit s spec The array index must be a string literal that identifies the Ada unit case insensitive The value of this attribute must bea stringthat identifies thefilethat con tains this unit s spec case sensitive or insensitive depending on the operating system for Specification
346. rograms 23 Running and Debugging Ada Programs This chapter discusses how to debug Ada programs An incorrect Ada program may be handled in three ways by the GNAT compiler 1 The illegality may be a violation of the static semantics of Ada In that case GNAT diagnoses the constructs in the program that are illegal It is then a straightforward matter for the user to modify those parts of the program 2 The illegality may be a violation of the dynamic semantics of Ada In that case the program compiles and executes but may generate incorrect results or may terminate abnormally with some exception 3 When presented with a program that contains convoluted errors GNAT itself may terminate abnormally without providing full diag nostics on the incorrect user program 23 1 The GNAT Debugger GDB GDB is a general purpose platform independent debugger that can be used to debug mixed language programs compiled with ccc and in par ticular is capable of debugging Ada programs compiled with GNAT The latest versions of GDB are Ada aware and can handle complex Ada data structures The manual Debugging with GDB contains full details on the usage of GDB indudinga section on its usageon programs This manual should be consulted for full details The section that follows is a brief introduction to the philosophy and use of apa When GNAT programs are compiled the compiler optionally writes debugging information into the generated object fil
347. rror x Exdude source files check object consistency only z No main subprogram You may obtain this listing by running the program gnatbina with no arguments 4 10 Command Line Access The package Ada Command Line provides access to the command line arguments and program name In order for this interface to operate correctly the two variables int gnat_argc char gnat argv are dedared in one of the GNAT library routines These variables must be set from the actual argc and argv values passed to the main pro gram With no n present gnatbind generates the C main program to automatically set these variables If the n switch is used there is no automatic way to set these variables If they are not set the procedures in Ada Command Line Will not be available and any attempt to use them will raise Constraint Error If command line access is required your main program must set gnat argc and gnat argv from the argc and argv Values passed to it 4 11 Search Paths for gnatbina The binder takes the name of an ALI file as its argument and needs to locate source files as well as other ALI files to verify object consistency For source files it follows exactly the same search rules as gcc see Section 3 3 Search Paths and the Run Time Library RTL page 71 For ALI files the directories searched are 1 The directory containing the ALI file named in the command line unless the switch 1 is specified 2 All directorie
348. rst column lists the task 1D that is used to refer to tasks in the following commands Ne break linespec task taskid break linespec task taskid if These commands are like the break thread line spec Specifies source lines Use the qualifier task taskid with a breakpoint command to specify that you only want cps to stop the program when a particular Ada task reaches this breakpoint taskid is one of the numeric task identifiers assigned by cpp shown in the first column of the info tasks display If you donot specify task taskid when you set a breakpoint the breakpoint applies to all tasks of your program You can use the task qualifier on conditional breakpoints as well in this case place task taskid before the breakpoint condition before the i 279 GNAT User s Guide for Unix Platforms task taskno This command allows to switch to the task referred by tas kno In particular This allows to browse the backtrace of the specified task It is advised to switch back to the original task before continuing execution otherwise the scheduling of the program may be perturbated For more detailed information on the tasking support see Debugging with GDB 23 9 Debugging Generic Units GNAT always uses code expansion for generic instantiation This means that each time an instantiation occurs a complete copy of the original code is made with appropriate substitutions of formals by actuals
349. rue then neither order is acceptable and in fact there is no correct order If one of the two expressions is true and the other is false then one of the above orders is correct and the other is incorrect For example if expression 1 1 and expression 2 2 then the call to Func_2 will occur but not the call to Func 1 This means that it is essential to elaborate the body of unit 1 before the body of unit 2 sothe first order of elaboration is correct and the second is wrong By making expression 1 and expression 2 depend on input data or perhaps the time of day we can make it impossible for the compiler or binder to figure out which of these expressions will be true and hence it is impossible to guarantee a safe order of elaboration at run time 11 2 Checking the Elaboration Order in Ada 95 In some languages that involve the same kind of elaboration problems e g J ava and C the programmer is expected to worry about these or dering problems himself and it is common to write a program in which an incorrect elaboration order gives surprising results because it refer ences variables beforethey areinitialized Ada 95is designed to bea safe 179 GNAT User s Guide for Unix Platforms language and a programmer beware approach is dearly not sufficient Consequently the language provides three lines of defense Standard rules Some standard rules restrict the possible choice of elabora tion order In particular if you with a
350. ry depends on the way the GNAT environment has been installed and can be determined by means of the command gnatls v Thelast entry in the object search path usually contains the gnat library This Makefile contains its own documentation and in particular the set of instructions needed to rebuild a new library and to use it 239 GNAT User s Guide for Unix Platforms 240 K k Mb b M M m V M orowoymwuwv uur o 28 May 2002 Chapter 17 Using the GNU make Utility 17 Using the GNU make Utility This chapter offers some examples of makefiles that solve specific prob lems It does not explain how to write a makefile see the GNU make documentation nor does it try to replace the gnatmake utility see Chap ter 6 The GNAT Make Program gnatmake page 115 All the examples in this section are specific to the GNU version of make Although make is a standard utility and the basic language is the same these examples use some advanced features found only in GNU make 17 1 Using gnatmake in a Makefile Complex project organizations can be handled in a very powerful way by using GNU make combined with gnatmake For instance here is a Makefile which allows you to build each subsystem of a big project into a separate shared library Such a makefile allows you to signifi cantly reduce the link time of very big applications while maintaining full coherence at
351. s division by zero 60 Checks elaboration 180 Checks overloW 327 Checks suppressing 60 COBOL thee eee cei ee ete Nea 29 code page 437 0 16 code page 850 17 Combining GNAT switches 42 Command line length 112 Compilation model 15 Configuration pragmas 131 Consistency checks in binder 103 Convention Ada 28 Convention sm ssss sells 29 Convention Assembler 29 Convention C 0 cece eee eee 29 Convention C 29 Convention COBOL 29 Convention Fortran 29 Convention Stdceall 30 Convention Stubbed 30 Conventions 3 CR eis ene dpt Ue este 15 Cynllic zzz ssi em m USA 16 Deb g irera ki e nee dun Fat 51 Debug Pool 0 ce eee eee 255 Debugger vce a ees eee es 273 Debugging ir bb ited 273 Debugging Generic Units 280 Debugging information including 112 Debugging options 67 Dependencies producing list 119 Dependency rules 115 Division by zerO 60 GNAT User s Guide for Unix Platforms Elaborate oin de ER 183 Elaborate_All 183 Elaborate_Body 182
352. s Ada program is compiled to generate the object file for the main program The name of the Ada file is b xxx aab with the corre sponding spec b xxx ads where xxx is the name of the main program unit Finally the linker is used to build the resulting executable program using the object from the main program from the bind step as well as the object files for the Ada units of the program 2 10 Mixed Language Programming 2 10 1 Interfacing to C There aretwo ways to build a program that contains some Ada files and some other language files depending on whether the main program is in Ada or not If themain program is in Ada you should proceed as follows 1 Compile the other language files to generate object files For in stance gcc c filei c gcc c file2 c 2 Compilethe Ada units to produce a set of object files and ALI files For instance gnatmake c my main adb 3 Run the Ada binder on the Ada main program For instance gnatbind my main ali 4 LinktheAda main program the Ada objects and the other language objects For instance 27 GNAT User s Guide for Unix Platforms gnatlink my_main ali filel o file2 o The three last steps can be grouped in a single command gnatmake my_main adb largs filel o file2 o If the main program is in some language other than Ada Then you may have more than one entry point in the Ada subsystem You must use a special option of the binder to generate callable routines to initiali
353. s ads you must recompile both greetings adb and gmain adb because both files contain units that depend on greetings ads gnatbind Will warn you if you forget one of these compilation steps sothat it is impossibleto generate an inconsistent program as a result of forgetting to do a compilation Nevertheless it is tedious and error prone to keep track of dependencies among units One approach to handle the dependency bookkeeping is to use a makefile However makefiles present maintenance problems of their own if the dependencies change as you change the program you must make sure that the makefile is kept up to date manually which is also an error prone process Thegnatmaxe utility takes care of these details automatically Invoke it using either one of the following forms gnatmake gmain adb gnatmake gmain 28 May 2002 Chapter 1 Getting Started with GNAT The argument is the name of the file containing the main program you may omit the extension gnatmake examines the environment automat ically recompiles any files that need recompiling and binds and links the resulting set of object files generating the executable file gmain In a large program it can be extremely helpful to use gnatmake because working out by hand what needs to be recompiled can be difficult Note that gnatmake t
354. s before the Document itself or if the original publisher of the version it refers to gives permission K In any section entitled Acknowledgements or Dedications pre serve the section s title and preserve in the section all the substance and tone of each of the contributor acknowledgements and or dedi cations given therein L Preserve all the Invariant Sections of the Document unaltered in their text and in their titles Section numbers or the equivalent are not considered part of the section titles M Delete any section entitled Endorsements Such a section may not be induded in the Modified Version N Do not retitle any existing section as Endorsements or to conflict in title with any Invariant Section If the Modified Version includes new front matter sections or appen dices that qualify as Secondary Sections and contain no material copied from the Document you may at your option designate some or all of these sections as invariant To do this add their titles to the list of Invariant Sections in the Modified Version s license notice Thesetitles must be distinct from any other section titles You may add a section entitled Endorsements provided it contains nothing but endorsements of your Modified Version by various parties for example statements of peer review or that thetext has been approved by an organization as the authoritative definition of a standard You may add a passage of up to five words
355. s displayed in the de bugger interaction window along with a message confirming normal program termination 12 55 May 2002 Chapter 1 Getting Started with GNAT 1 5 3 Other Glide Features You may have observed that some of the menu selections contain abbre viations e g C x c f for open file intheriles menu These are shortcut keys that you can use instead of selecting menu items The stands for ca thus c x c means followed by Ctt and this sequence can be used instead of selecting Files and then open file To abort a Glide command type curg If you want Glide to start with an existing source file you can either launch Glide as above and then open the file via Files gt Open file or else simply pass the name of the source file on the command line glide hello adb amp While you are using Glide a number of buffers exist You create some explicitly e g when you open create a file Others arise as an effect of the commands that you issue e g the buffer containing the output of the tools invoked during a build If a buffer is hidden you can bring it into a visible window by first opening the Buffers menu and then selecting the desired entry If a buffer occupies only part of the Glide screen and you want to expand it to fill the entire screen then click in the buffer and then sel
356. s file is known as the Ada Library Information ali file The following information is contained in the ali file e Version information indicates which version of GNAT was used to compile the unit s in question e Main program information induding priority and time slice set tings as well as the wide character encoding used during compila tion e List of arguments used in the gcc command for the compilation e Attributes of theunit induding configuration pragmas used an in dication of whether the compilation was successful excepti on model used etc e A list of relevant restrictions applying to the unit used for consis tency checking e Categorization information eg use of pragma Pure e Information on all witn ed units including presence of Elaborate Or Elaborate All pragmas e Information from any Linker Options pragmas used in the unit e Information on the use of Body Version Or Version attributes in the unit e Dependency information This is a list of files together with time stamp and checksum information These arefiles on which theunit depends in the sense that recompilation is required if any of these units are modified e Cross reference data Contains information on all entities refer enced in the unit Used by tools like gnatxref and gnatfind to provide cross reference information For a full detailed description of the format of the a1i file see the source of the body of unit Lib wri
357. s oh ne Sse aay nes e Sy 164 Switches Related to Project FileS 165 Tools Supporting Project FileS 166 10 13 1 gnatmake and Project Files 166 10 13 1 1 Switches and Project Files 166 10 13 1 2 Project Files and Main Subprograms 169 10 13 2 TheGNAT Driver and Project Files 170 23 May 2002 10 13 3 Glideand Project FileS 172 10 14 An Extended Example Q Q 172 10 15 Project File Complete Syntax 174 11 Elaboration Order Handling in GNAT 177 11 1 Elaboration CodeinAda95 177 11 2 Checking the Elaboration Order in Ada 95 179 11 3 Controlling the Elaboration Order in Ada 95 181 11 4 Controlling Elaboration in GNAT Internal Calls 184 11 5 Controlling Elaboration in GNAT External Calls 188 11 6 Default Behavior in GNAT Ensuring Safety 190 11 7 Elaboration Issues for Library TaskS 192 11 8 Mixing Elaboration ModedlS 199 11 9 What to Dolf the Default Elaboration Behavior Fails iive MU ah haute N e AL ED cime dine sve tetas 200 11 10 Elaboration for Access to Subprogram Values 204 11 11 Summary of Procedures for Elaboration Control 205 11 12 Other Elaboration Order Considerations 205 12 TheCross Referencing Tools gnatx
358. s so the ALI file will not gotothe right place Therefore you should avoid using the o switch The packages Ada System and Interfaces and their children make up the GNAT RTL together with the simple system 10 package used in the Hello World example The sources for these units are needed by the compiler and are kept together in one directory Not all of the bodies are needed but all of the sources are kept together anyway In anormal installation you need not specify these directory names when compiling or binding Either the environment variables or the built in defaults cause these files to be found In addition to the language defined hierarchies System Ada and In terfaces the GNAT distribution provides a fourth hierarchy consisting of child units of GNAT This is a collection of generally useful routines See the GNAT Reference Manual for further details Besides simplifying access tothe RTL a major useof search pathsisin compiling sources from multiple directories This can make development environments much more flexible 72 28 May 2002 Chapter 3 Compiling Using gcc 3 4 Order of Compilation Issues If in our earlier example there was a spec for the hello procedure it would be contained in the file ne11o aa s yet this file would not have to be explicitly compiled This is the result of the model we chose to implement library management Some of the consequences of this model are as follows e Thereis no point i
359. s specified by 1 switches on the gnatbina command line in theorder given 108 28 May 2002 Chapter 4 Binding Using gnatbind 3 Each of the directories listed in the value of the ADA OBJECTS PATH environment variable Construct this value exactly as the PATH environment variable a list of directory names separated by colons semicolons when working with the NT version of GNAT 4 The content of the ada_object_path file which is part of the GNAT installation tree and is used to store standard libraries such as the GNAT Run Time Library RTL unless the switch nostdlib is specified Section 16 2 Installing an Ada Library page 234 In the binder the switch x is used to specify both source and library file paths Use axr instead if you want to specify source paths only and ao if you want to specify library paths only This means that for the binder Idir is equivalent to ardir aodir The binder generates the bind file a C language source file in the current working directory The packages Ada System and Interfaces and their children make up the GNAT Run Time Library together with the package GNAT and its children which contain a set of useful additional library functions provided by GNAT The sources for these units are needed by the com piler and are kept together in one directory The ALI files and object f
360. s the ACVC tests 7 3 Command Line for gnatchop The gnatchop command has the form gnatchop switches file name file name file name directory The only required argument is the file name of the file to be chopped There are no restrictions on the form of this file name The file itself contains one or more Ada units in normal GNAT format concatenated together As shown more than one file may be presented to be chopped 126 28 May 2002 Chapter 7 Renaming Files Using gnat chop When run in default mode gnat chop generates one output file in the current directory for each unit in each of the files directory if specified gives the name of the directory to which the output files will be written If it is not specified all files are written to the current directory For example given a file called hellofiles containing procedure hello with Text_I0 use Text IO procedure hello is begin Put Line Hello end hello the command gnatchop hellofiles generates two files in the current directory one called hello ads con taining the single line that is the procedure spec and the other called hello adb containing the remaining text The original file is not af fected The generated files can be compiled in the normal manner 7 4 Switches for gnatchop gnatchop recognizes the following
361. sadvantage of this approach is that no such order may exist If the binder does not generate any diagnostics then it means that it has found an elaboration order that is guaranteed to be safe However the binder may still be relying on implicitly generated Elaborate A11 pragmas so portability to other compilers than GNAT is not guaranteed If it is important to guarantee portability then the compilations should use the gnatw1 warn on elaboration problems switch This will cause warning messages to be generated indicating the missing Elaborate All pragmas Consider the following source program with k package j is m integer k r end whereit is dear that there should bea pragma E1aborate A11 for unit x An implicit pragma will be generated and it is likely that the binder will be able to honor it However it is safer to include the pragma explicitly in the source If this unit is compiled with the gnatwl switch then the compiler outputs a warning with k package j is m integer k r gt gt gt warning call to r may raise Program Error gt gt gt warning missing pragma Elaborate All for k end and these warnings can be used as a guide for supplying manually the missing pragmas 191 GNAT User s Guide for Unix Platforms This default mode is morerestrictive than the Ada Reference M anual and it is possible to construct programs which will compile using the dynamic model describe
362. scribed the default rules used by GNAT to determine the file name in which a given unit resides It is often convenient to follow these default rules and if you follow them the compiler knows without being explicitly told where to find all the files it needs H owever in some cases particularly when a program is imported from another Ada compiler environment it may be more convenient for the programmer to specify which file names contain which units GNAT allows arbitrary file names to be used by means of the Source_File_Name pragma The form of this pragma is as shown in the following examples pragma Source_File_Name My_Utilities Stacks Spec_File_Name gt myutilst_a ada pragma Source_File_name My_Utilities Stacks Body_File_Name gt myutilst ada As shown in this example the first argument for the pragma is the unit name in this example a child unit The second argument has the form of a named association The identifier indicates whether the file name is for a spec or a body the file name itself is given by a string literal Thesource file name pragma is a configuration pragma which means that normally it will be placed in the gnat adc file used to hold config uration pragmas that apply to a complete compilation environment For 20 RR 23 May 2002 Chapter 2 The GNAT Compilation Model more details on how the gnat ade fileis created and used see Section 8 1 Handling of Configurati
363. source file will first be searched in the directory where gnatmake was invoked and if it is not 115 GNAT User s Guide for Unix Platforms found it will be search on the source path of the compiler as described in Section 3 3 Search Paths and the Run TimeLibrary RTL page 71 When several file names are specified if an executable needs to be rebuilt and relinked all subsequent executables will be rebuilt and relinked even if this would not be absolutely necessary All gnatmake output except when you specify m is to stderr The output produced by the m switch is send to stdout 6 2 Switches for gnatmake You may specify any of the following switches to gnatmake GCC compiler name Program used for compiling The default is gcc You need to use quotes around compiler name if compiler name COn tains spaces or other separator characters As an example GCC foo x y will instruct gnatmake tO USe foo x y as your compiler Note that switch c is always inserted after your command name Thus in the above example the compiler command that will be used by gnatmake will be oo c x y If several GCC compiler_ name are used only the last compiler_name is taken into account How ever all the additional switches are also taken into account Thus GCC foo x y GCC bar z t is equivalent to GCC bar x y z t GNATBIND binder name Program used for binding The default is gnatbina You
364. spec of the generic unit has been elaborated before the instantiation but not the body If this rule is violated then the exception Program Error is raised The idea is that if the body has been elaborated then any variables it references must have been elaborated by checking for the body being elaborated we guarantee that none of its references causes any trouble As we noted above this is a little too restrictive because a subprogram that has no non local references in its body may in fact be safe to call However it really would be unsafe to rely on this because it would mean 180 23 May 2002 Chapter 11 Elaboration Order Handling in GNAT that the caller was aware of details of the implementation in the body This goes against the basic tenets of Ada A plausible implementation can be described as follows A Boolean variable is associated with each subprogram and each generic unit This variable is initialized to False and is set to True at the point body is elaborated Every call or instantiation checks the variable and raises Program Error if the variable is False Note that one might think that it would be good enough to have one Boolean variable for each package but that would not deal with cases of trying to call a body in the same package as the call that has not been elaborated yet Of course a compiler may be able to do enough analysis to optimize away some of the Boolean variables as unnecessary and GNAT indeed
365. ss the resulting inlining actions 331 GNAT User s Guide for Unix Platforms 3323 May 2002 Appendix A GNU Free Documentation License Appendix A GNU Free Documentation License Version 1 1 March 2000 Copyright 2000 Free Software Foundation I nc 59 Temple Place Suite 330 Boston MA 02111 1307 USA Everyone is permitted to copy and distribute verbatim copies of this license document but changing it is not allowed 0 PREAMBLE The purpose of this License is to make a manual textbook or other written document free in the sense of freedom to assure everyone the effective freedom to copy and redistribute it with or without modifying it either commercially or noncommercially Secondarily this License preserves for the author and publisher a way to get credit for their work while not being considered responsible for modifications made by others This License is a kind of copyleft which means that derivative works of the document must themselves be free in the same sense It complements the GNU General PublicLicense which is a copyleft license designed for free software We have designed this License in order to use it for manuals for free software because free software needs free documentation a free program should come with manuals providing the same freedoms that the software does But this Licenseis not limited to software manuals it can beused for any textual work regardless of subject matter or whether
366. ssages as fatal errors The switch gnaty on its own that is not followed by any letters or dig its is equivalent tognaty3abcefhiklmprst that is all checking options are enabled with the exception of gnatyo with an indentation level of 3 This is the standard checking option that is used for the GNAT sources 3 2 5 Run Time Checks If you compile with the default options GNAT will insert many run time checks into the compiled code including code that performs range checking against constraints but not arithmetic overflow checking for integer operations induding division by zero or checks for access before elaboration on subprogram calls All other run time checks as required by the Ada 95 Reference M anual are generated by default Thefollowing gcc Switches refine this default behavior gnatp Suppress all run time checks as though pragma Suppress all checks had been present in the source Use this switch to improve the performance of the code at the expense of safety in the presence of invalid data or program bugs gnato Enables overflow checking for integer operations This causes GNAT to generate slower and larger executable pro grams by adding code to check for overflow resulting in rais Ing Constraint_Error as required by standard Ada seman tics These overflow checks correspond to situations in which thetrue valueof the result of an operation may be outside the base range of the result type The following example s
367. ssignments and the initializing values of object declarations are validity checked e gnatVd Default RM validity checks Some validity checks are done by default following normal Ada se mantics RM 13 9 1 9 11 A check is done in case statements that the expression is within the range of the subtype If it is not Constraint E rror is raised For assignments to array components a check is done that the expression used as index is within the range If it is not Constraint Error is raised Both these validity checks may be turned off using switch gnatvp They are turned on by default If gnatvp is specified a subsequent switch anatva will leave the checks turned on Switch gnatvp should be used only if you are sure that all such expressions have valid values If you use this switch and invalid values are present then the program is erroneous and wild jumps or memory overwriting may occur e gnatvi Validity checks for in mode parameters Arguments for parameters of mode in are validity checked in func tion and procedure calls at the point of call 52 8 May 2002 Chapter 3 Compiling Using gcc e gnatVm Validity checks for in out mode parameters Arguments for parameters of mode in out are validity checked in procedure calls at the point of call The m here stands for modify since this concerns parameters that can be modified by the call N
368. st be surrounded by spaces e Colon equal assignment must be surrounded by spaces e Comma must bethefirst non blank character on theline or be immediately preceded by a non blank character and must be followed by a space e f the token preceding a left paren ends with a letter or digit then a space must separate the two tokens e A right parenthesis must either be the first non blank character on a line or it must be preceded by a non blank character e A semicolon must not be preceded by a space and must not be followed by a non blank character e A unary plus or minus may not be followed by a space e A vertical bar must be surrounded by spaces In the above rules appearing in column one is always per mitted that is counts as meeting either a requirement for a required preceding space or as meeting a requirement for no preceding space Appearing at the end of a lineis also always permitted that is counts as meeting either a requirement for a following space or as meeting a requirement for no following space MJ Uo 59 GNAT User s Guide for Unix Platforms If any of these style rules is violated a message is generated giving de tails on theviolation Theinitial characters of such messages are always style Note that these messages are treated as warning messages so they normally do not prevent the generation of an object file The gnatwe switch can be used to treat warning messages including style me
369. state even if maintenance changes some bodies of some subprograms Conversely if a program that does not follow this rule happens to besafe at some point this state of affairs may deteriorate silently as a result of maintenance changes You may have noticed that the above discussion did not mention the use Of Elaborate Body This was a deliberate omission If you with an Elaborate Body unit it still may be the case that code in the body makes calls to some other unit so it is still necessary to use Elaborate A11 on such units 11 4 Controlling Elaboration in GNAT Internal Calls In the case of internal calls i e calls within a single package the programmer has full control over the order of elaboration and it is up to 184 K T 28 May 2002 Chapter 11 Elaboration Order Handling in GNAT the programmer to elaborate declarations in an appropriate order For example writing function One return Float Q Float One function One return Float is begin return 1 0 end One will obviously raise Program Error at run time because function One will be called before its body is elaborated In this case GNAT will generate a warning that the call will raise Program Error procedure y is function One return Float Q Float One gt gt gt warning cannot call One before body is elaborated gt gt gt warning
370. stepping over it may therefore not always cause all the expected side effects 2 The big leap More commonly known as cross jumping in which two identical pieces of code are merged and the program counter suddenly jumps to a statement that is not supposed to be executed simply because it and the code following translates to the same thing as the code that was supposed to be executed This effect is typically seen in sequences that end in a jump such as a goto a return Of a break in a C switch statement 3 The roving variable The symptom is an unexpected value in a variable There are various reasons for this effect e In a subprogram prologue a parameter may not yet have been moved to its home e A variable may be dead and its register re used Thisis proba bly the most common cause e As mentioned above the assignment of a value to a variable may have been moved e A variable may be eliminated entirely by value propagation or other means In this case GCC may incorrectly generate debuggi ng information for the variable In general when an unexpected value appears for a local variable or parameter you should first ascertain if that value was actually computed by your program as opposed to being incorrectly reported by the debugger Record fields or array elements in an object desig nated by an access value are generally less of a problem once you have ascertained that the access value is sensible Typically this
371. sting is the p pessimistic elaboration order switch for gnatbind Normally the binder tries to find an order that has the best chance of of avoiding elaboration problems With this switch the binder plays a devil s advocate role and tries to choose the order that has the best chance of failing If your program works even with this switch then it has a better chance of being error free but this is still not a guarantee For an example of this approach in action consider the C tests exe cutable tests from the ACVC suite If these are compiled and run with the default treatment then all but one of them succeed without gener ating any error diagnostics from the binder However there is one test that fails and this is not surprising because the whole point of this test is to ensure that the compiler can handle cases where it is impossible to determine a correct order statically and it checks that an exception is indeed raised at run time This one test must be compiled and run using the gnatE switch and then it passes Alternatively the entire suite can be run using this switch It is never wrong to run with the dynamic elaboration switch if your code is correct and we assume that the C tests are indeed correct it is less efficient but efficiency is not a factor in running the ACVC tests 11 10 Elaboration for Access to Subprogram Values The introduction of access to subprogram types in Ada 95 complicates the handling of ela
372. stub 88 259 vi 0 P rU 0vuo 6 L w_wpp rr r 23 May 2002 21 Reducing the Size of Ada E xecutables with gnatelim ooooconcaconnanonnnannas 261 21 1 21 2 21 3 21 4 21 5 21 6 21 7 21 8 22 1 22 2 22 3 22 4 22 5 22 6 About gnat LL tds os deoa r dnra dd t 261 Eliminate Pragma sesini aneres krida eruak ure 261 Tr Files tel casei 4 epe EE EE dA RESI FEES 262 Preparing Tree and Bind Files for gnatelim 262 Ru nrnllhggiatelims ceu aci iau R RA 263 Correcting the List of Eliminate Pragmas 264 Making Your Executables Smaller 264 Summary of the gnatelim Usage Cyde 264 22 Other Utility Programs 267 Using Other Utility Programs with GNAT 267 The gnatpsta Utility Program 267 The External Symbol Naming Scheme of GNAT 267 Ada Mode for a1ide lesen nnn 269 22 4 1 General Features 269 22 4 2 Ada Mode Features That Help Understanding COS zz 22 20 Ub reds pina sss 3 den ae dod 269 22 4 3 Glide Support for Writing Ada Code 269 Converting Ada Files to html with gnathtml 270 Installing abate E ott Sacs 271 23 Running and Debugging Ada Programs 273 23 1 23 2 23 3 23 4 23 5 23 6 23 7 23 8 23 9 23 10 The GNAT Debugger GDB 273 Running GDB iacere Ee ea d
373. sure elaboration of the GNAT components Consult the documentation of the other Ada compiler for further details on elaboration However it is not possible to mix the tasking run time of GNAT and DEC Ada 83 All thetasking operations must either be entirely within GNAT compiled sections of the program or entirely within DEC Ada 83 compiled sections of the program Asm Equivalent to Ada Assembler Equivalent to Ada COBOL Data will be passed according to the conventions described in section B 4 of the Ada 95 Reference Manual C Data will be passed according to the conventions described in section B 3 of the Ada 95 Reference Manual CPP This stands for C For most purposes this is identical to C See the separate description of the specialized GNAT pragmas relating to C interfacing for further details Fortran Data will be passed according to the conventions described in section B 5 of the Ada 95 Reference Manual Intrinsic This applies to an intrinsic operation as defined in the Ada 95 Reference Manual If a a pragma Import Intrinsic applies to a subprogram this means that the body of the subprogram is provided by the compiler itself usually by means of an efficient code sequence and that the user does not supply an explicit body for it In an application program the pragma can only be applied to the following two sets of names which the GNAT compiler recognizes e Rotate L eft Rotate Right Shift Left Shift Right
374. switches c Causes gnatchop to operate in compilation mode in which configuration pragmas are handled according to strict RM rules See previous section for a full description of this mode gnatxxx This passes the given gnatxxx Switch to gnat which is used to parse the given file Not all xxx options make sense but for example the use of gnati2 allows gnatchop to process a source file that uses Latin 2 coding for identifiers h Causes gnatchop to generate a brief help summary to the standard output file showing usage information kmm Limit generated file names to the specified number mm of char acters This is useful if the resulting set of files is required to be interoperable with systems which limit the length of file names No space is allowed between the k and the numeric value The numeric value may be omitted in which case a 127 GNAT User s Guide for Unix Platforms 128 default of k8 suitable for use with DOS like file systems is used If no k switch is present then there is no limit on the length of file names Causes the file modification time stamp of the input fileto be preserved and used for the time stamp of the output file s This may be useful for preserving coherency of timestamps in an enviroment where gnat chop is used as part of a standard build process Causes output of informational messages indicating the set of generated files to be suppressed Warnings and error mes sages are unaffected
375. t for Default Switches Ada use g end case end Builder package Compiler is case Style is when deb gt for Default Switches Ada use gnata gnato gnatE when rel gt for Default Switches Ada use 02 end case end Compiler end Build Style Type is an example of a string type which is the project file analog of an Ada enumeration type but containing string literals rather than identifiers style is declared as a variable of this type The form external STYLE deb is known as an external refer ence its first argument is the name of an external variable and the second argument is a default value to be used if the external variable doesn t exist You can define an external variable on the command line GNAT User s Guide for Unix Platforms via the x switch or you can use an environment variable as an external variable Each case construct is expanded by the Project Manager based on the value of style Thus the command gnatmake P common build gpr XSTYLE deb is equivalent tothegnatmake invocation using the project file debug gpr in the earlier example So is the command gnatmake P common build gpr since deb is the default for STYLE Analogously gnatmake P common build gpr XSTYLE rel is equivalent to the gnatmake invocation using the project file release gpr in the earlier example 10 2 3 Importing Other Projects A compilation unit in a source
376. t contained in file 1ib writ adb in the GNAT compiler sources 2 9 Binding an Ada Program When using languages such as C and C once the source files have been compiled the only remaining step in building an executable program is linking the object modules together This means that it is possibletolink 26 28 May 2002 Chapter 2 The GNAT Compilation Model an inconsistent version of a program in which two units have included different versions of the same header The rules of Ada do not permit such an inconsistent program to be built For example if two dients have different versions of the same package it is illegal to build a program containing these two clients These rules are enforced by the GNAT binder which also determines an elaboration order consistent with the Ada rules The GNAT binder is run after all the object files for a program have been created It is given the name of the main program unit and from this it determines the set of units required by the program by reading the corresponding ALI files It generates error messages if the program is inconsistent or if no valid order of elaboration exists If no errors are detected the binder produces a main program in Ada by default that contains calls to the elaboration procedures of those compilation unit that require them followed by a call to the main pro gram Thi
377. t e Check that consistent versions of GNAT were used for compilation e Check consistency of configuration pragmas as required Normally failure of such checks in accordance with the con sistency requirements of the Ada Reference Manual causes error messages to be generated which abort the binder and prevent the output of a binder file and subsequent link to obtain an executable The t switch converts these error messages into warnings so that binding and linking can continue to completion even in the presence of such errors The result may be a failed link dueto missing symbols or a non functional executable which has undefined semantics This means that t should beused only in unusual situations with extreme care 4 5 Elaboration Control The following switches provide additional control over the elaboration order For full details see See Chapter 11 Elaboration Order Handling in GNAT page 177 P Normally the binder attempts to choose an elaboration or der that is likely to minimize the likelihood of an elaboration order error resulting in raising a Program Error exception This switch reverses the action of the binder and requests that it deliberately choose an order that is likely to maxi mize the likelihood of an elaboration error This is useful in ensuring portability and avoiding dependence on accidental fortuitous elaboration ordering Normally it only makes sense to usethe p switch if dynamic elaboration check
378. t File string Object Dir string Exec Dir string Main string list Languages string list Library Dir string Library Name string Library Kind string Library Elaboration string Library Version string The attributes for package Naming are as follows see Section 10 10 Naming Schemes page 162 Attribute Name Category Index Value Specification Suffix associative language string array name Implementation Suffix associative language string array name Separate Suffix simple n a string attribute j Casing simple n a string attribute Dot Replacement simple n a string attribute Specification associative Ada unit string array name Implementation associative Ada unit string array name Specification Exceptions associative language string list array name Implementation_ associative language string list Exceptions array name The attributes for package Builder Compiler Binder Linker Cross Reference and Finder are as follows see Section 10 13 1 1 Switches and Project Files page 166 Attribute Name Category Index Value Default_Switches associative language string list array name Switches associative filename string list array In addition package Builder has a single string attribute Local _ Configuration Pragmas and package Builder has a single string at tribute Global Configuration Pragmas The attribute for package Glide are not documented they are for inter nal use only 152 23 May 2002 Chapter 10 GNAT
379. t error messages to stderr the standard error file as well asthe verbose format message or full listing which as usual is written to stdout the standard output file The m stands for maximum n is a decimal integer in the range of 1 to 999 and limits the number of error messages to be generated For example using gnatm2 might yield 04 Incorrect spelling of keyword function 35 missing fatal error maximum errors reached compilation abandoned gnatf e adb 7 gnatq Thes stands for full Normally the compiler suppresses error messages that arelikely to beredundant This switch causes all error messages to be generated In particular in the case of references to undefined variables If a given variable is referenced several times the normal format of messages is 07 V is undefined more references follow where the parenthetical comment warns that there are ad ditional references to the variable v Compiling the same program with the gnat switch yields e adb 7 07 V is undefined e adb 8 07 V is undefined e adb 8 12 V is undefined e adb 8 16 V is undefined e adb 9 07 V is undefined e adb 9 12 V is undefined The q stands for quit really don t quit In normal oper ation mode the compiler first parses the program and de termines if there are any syntax errors If there are ap propriate error messages are generated and compilation is immediately terminated This sw
380. t executable name The name of the final executable program will be exec name If the o switch is omitted the default name for the executable will be the name of the input file in appropriate form for an executable file on the host system This switch cannot be used when invoking gnatmake with several file names q Quiet When this flag is not set the commands carried out by gnatmake are displayed s SWITCH_CHECK Recompile if compiler switches have changed since last com pilation All compiler switches but I and o aretaken into ac count in the following way orders between different first let ter switches are ignored but orders between same switches are taken into account For example o 02 is different than 02 0 but g o is equivalent to o g 119 GNAT User s Guide for Unix Platforms Unique Recompile at most the main file It implies c Com bined with f it is equivalent to calling the compiler directly Verbose Displays the reason for all recompilations gnatmake decides are necessary Nomain subprogram Bind and link the program even if the unit namegiven on the command lineis apackagename The resulting executable will execute the elaboration routines of the package and its closure then the finalization routines gcc switches The switch g or any uppercase switch other than a L or s or any switch that is more than one character is passed to gcc e g 0 gnato etc Source and li
381. t is set the dot is replaced by an x in a red circle Clicking the circle toggles the breakpoint off and the red circle is replaced by the green dot For this example set a breakpoint at the statement where put Line is invoked Start program execution by selecting the Run button on the top menu bar The start button will also start your program but it will cause program execution to break at the entry to your main subprogram Evidence of reaching the breakpoint will appear the source file line will be highlighted and the debugger interactions pane will display a relevant message You can examine the values of variables in several ways Move the mouse over an occurrence of Ind in the for loop and you will see the value now 1 displayed Alternatively right click on Ind and select Display Ind a box showing the variable s name and value will appear in the data canvas Although a loop index is a constant with respect to Ada semantics you can change its value in the debugger Right click in the box for Ina and select the Set value of Ind item Enter 2 as the new value and press ox The box for Ind shows the update Press the step button on the top menu bar this will step through one line of program text the invocation of Put Line and you can observe the effect of having modified Ind since the value displayed is 2 Remove the breakpoint and resume execution by selecting the cont button You will see the remaining output line
382. tains the call to the main program see Section 4 1 Running gnatbind page 75 The remaining entries are assorted runtime routines and the output will vary from platform to platform It is also possible to use cpp with these traceback addresses to debug the program For example we can break at a given code location as reported in the stack traceback gdb nw stb gdb break 0x401373 Breakpoint 1 at 0x401373 file stb adb line 5 Itisimportant to note that the stack traceback addresses do not change when debug information is included This is particularly useful because it makes it possible to release software without debug information to minimize object size get a field report that includes a stack traceback 286 28 May 2002 Chapter 23 Running and Debugging Ada Programs whenever an internal bug occurs and then be able to retrieve the se quence of calls with the same program compiled with debug information 23 13 1 2 Tracebacks From Exception Occurrences Non symbolic tracebacks are obtained by using the E binder argument The stack traceback is attached to the exception information string and can be retrieved in an exception handler within the Ada program by means of the Ada95 facilities defined in Ada Exceptions Here is a simple example with Ada Text_I0 with Ada Exceptions procedure STB is use Ada use Ada E
383. tatements See the sec tion in this guide on elaboration checking for de tails on when such pragma should be used gnatwo activate warnings on address clause overlays This switch activates warnings for possibly unin tended initialization effects of defining address dauses that cause one variable to overlap an other The default is that such warnings are gen erated This warning can also beturned on using gnatwa gnatwO suppress warnings on address clause overlays This switch suppresses warnings on possibly un intended initialization effects of defining address dauses that cause one variable to overlap an other gnatwp activate warnings on ineffective pragma Inlines This switch activates warnings for failure of front end inlining activated by gnatw toinlinea par ticular call There are many reasons for not be ing abletoinlinea call including most commonly that the call is too complex to inline This warn ing can also be turned on using gnatwa 49 GNAT User s Guide for Unix Platforms gnatwP suppress warnings on ineffective pragma Inlines This switch suppresses warnings on ineffective pragma Inlines If the inlining mechanism can not inline a call it will simply ignore the request silently gnatwr activate warnings on redundant constructs This switch activates warnings for redundant constructs The following is the current list of constructs regarded as redundant This warning can als
384. tatements along some execution paths in a function e Incorrect unrecognized pragmas e Incorrect external names e Allocation from empty storage pool e Potentially blocking operations in protected types e Suspicious parenthesization of expressions e Mismatching bounds in an aggregate e Attempt to return local value by reference e Unrecognized pragmas e Premature instantiation of a generic body e Attempt to pack aliased components e Out of bounds array subscripts e Wrong length on string assignment e Violations of style rules if style checking is enabled e Unused with clauses e Bit_Order usage that does not have any effect e Compile time biased rounding of floating point constant e Standard Duration used to resolve universal fixed ex pression e Dereference of possibly null value e Dedaration that is likely to cause storage error e Internal GNAT unit with ed by application unit e Values known to be out of range at compile time e Unreferenced labels and variables e Address overlays that could dobber memory e Unexpected initialization when address clause present e Badalignment for address dause e Useless type conversions e Redundant assignment statements e Accidental hiding of name by child unit 46 28 May 2002 Chapter 3 Compiling Using gcc e Unreachable code e Access before elaboration detected at compile time
385. ted at bind time Editing a source file without compiling files that depend on the source file cause error messages to be generated by the binder For example suppose you have a main program hello adb anda package P from file p ads and you perform the following steps 1 Enter gcc c hello adb to compile the main program 2 Enter gcc c p ads to compile package P 3 Edit file p ads 4 Enter gnatbind hello At this point the file p a1i contains an out of date time stamp be cause the file p ads has been edited The attempt at binding fails and the binder generates the following error messages error hello adb must be recompiled p ads has been modified error p ads has been modified and must be recompiled Now both files must be recompiled as indicated and then the bind can succeed generating a main program You need not normally be con cerned with the contents of this file but it is similar to the following which is the binder file generated for a simple hello world program The package is called Ada_Main unless this name is actually used as a unit name in the partition in which case some other unique name is used with System package ada_main is Elab_Final_Code Integer pragma Import C Elab_Final_Code __gnat_inside_elab_final_code The main program saves the parameters argument count argument values environment pointer in global variables for l
386. ter set in source program identifiers as described in the Ada 95 Ref erence Manual This switch causes GNAT to recognize al ternate character sets in identifiers c is a single character indicating the character set as follows 1 Latin 1 identifiers 2 Latin 2 letters allowed in identifiers 23 May 2002 gnatWe Chapter 3 Compiling Using gcc 3 Latin 3 letters allowed in identifiers 4 Latin 4 letters allowed in identifiers 5 Latin 5 Cyrillic letters allowed in identifiers 9 Latin 9 letters allowed in identifiers p IBM PC letters code page 437 allowed in iden tifiers 8 IBM PC letters code page 850 allowed in iden tifiers f Full upper half codes allowed in identifiers n No upper half codes allowed in identifiers w Wide character codes that is codes greater than 255 allowed in identifiers See Section 2 2 Foreign Language Representation page 16 for full details on the implementation of these character sets Specify the method of encoding for wide characters e is one of the following h Hex encoding brackets coding also recognized u Upper half encoding brackets encoding also rec ognized S Shift IS encoding brackets encoding also recog nized e EUC encoding brackets encoding also recog nized 8 UTF 8 encoding brackets encoding also recog nized b Brackets encoding only default value For full details on the these encoding methods see See Sec tion 2 2 3 Wide Character Encodings
387. tern extern extern extern extern extern extern extern extern extern extern extern extern extern char ada__exceptions_E char system__exceptions_E char interfaces__c_streams_E char system__exception_table_E char ada__io_exceptions_E char system__secondary_stack_E char system stack checking E char system soft links E char ada tags E char ada streams E char system finalization root E char system finalization implementation E char ada finalization E char ada finalization list controller E char system file control block E char system file io E 93 GNAT User s Guide for Unix Platforms extern char ada__text_io_E SDP SDP _SDP extern void __gnat_hello__SDP extern void __gnat_ada__text_io__SDP extern void __gnat_ada__exceptions__SDP extern void __gnat_gnat__heap_sort_a__SDP extern void __gnat_system__exception_table_ extern void __gnat_system__machine_state_operations__ extern void __gnat_system__secondary_stack__SDP extern void __gnat_system__parameters__SDP extern void __gnat_system__soft_links__SDP extern void __gnat_system__stack_checking__SDP extern void gnat system traceback SDP extern void gnat ada streams SDP extern void gnat ada tags SDP extern void gnat system string ops SDP extern void gnat interfaces c streams SDP extern void gnat system file io SDP extern void gnat ada finalization SDP extern
388. tforms 224 T AA 23May2002 Chapter 14 Preprocessing Using gnatprep 14 Preprocessing Using gnatprep The gnatprep utility provides a simple preprocessing capability for Ada programs It is designed for use with GNAT but is not dependent on any special features of GNAT 14 1 Using gnatprep To call gnatprep Use gnatprep bcrsu Dsymbol value infile outfile deffile where infile outfile deffile switches is the full name of the input file which is an Ada source file containing preprocessor directives is the full name of the output file which is an Ada source in standard Ada form When used with GNAT this file name will normally have an ads or adb suffix is the full name of a text file containing definitions of sym bols to be referenced by the preprocessor This argument is optional and can be replaced by the use of the D switch is an optional sequence of switches as described in the next section 14 2 Switches for gnatprep b Causes both preprocessor lines and the lines deleted by pre processing to be replaced by blank lines in the output source file preserving line numbers in the output file Causes both preprocessor lines and the lines deleted by pre processing to be retained in the output source as comments marked with the special string This option will result in line numbers being preserved in the output file Dsymbol value Defines a new symbol associated with v
389. the checks They may be modified using either pragma Suppress to remove 327 GNAT User s Guide for Unix Platforms checks or pragma Unsuppress to add back suppressed checks in the program source 25 2 Optimization Levels The default is optimization off This results in the fastest compile times but GNAT makes absolutely no attempt to optimize and the generated programs are consi derably larger and slower than when optimization is enabled You can use the on switch where n is an integer from 0 to 3 on the gcc command line to control the optimization level 00 no optimization the default 01 medium level optimization 02 full optimization 03 full optimization and also attempt automatic inlining of small subprograms within a unit see Section 25 4 Inlining of Subprograms page 330 Higher optimization levels perform more global transformations on the program and apply more expensive analysis algorithms in order to generate faster and more compact code The price in compilation time and the resulting improvement in execution time both depend on the particular application and the hardware environment You should experiment to find the best level for your application Note Unlike some other compilation systems gcc has been tested extensively at all optimization levels There are some bugs which appear only with optimization turned on but there have also been bugs which show up only in unoptimized code Selectin
390. the case If all units carry a pragma Elaborate Body then all problems are eliminated except for calls entirely within a body which arein any case fully under programmer control However usingthe pragma everywhere is not always possible In particular for our unit i Unit 2 example if we marked both of them as having pragma Elaborate Body then dearly there would be no possible elaboration order 182 28 May 2002 Chapter 11 Elaboration Order Handling in GNAT The above pragmas allow a server to guarantee safe use by clients and clearly this is the preferable approach Consequently a good rule in Ada 95 is to mark units as Pure Or Preelaborate if possible and if this is not possible mark them as Elaborate Body if possible As we have seen there are situations where neither of these three pragmas can be used So we also provide methods for clients to control the order of elaboration of the servers on which they depend pragma Elaborate unit This pragma is placed in the context clause after a with cause and it requires that the body of the named unit be elaborated before the unit in which the pragma occurs The idea is to use this pragma if the current unit calls at elab oration time directly or indirectly some subprogram in the named unit pragma Elaborate_All unit This is a stronger version of the Elaborate pr
391. theses the name of the original author or publisher of that section if known or else a unique number Make the same adjustment to the section titles in the list of Invariant Sections in the license notice of the combined work In the combination you must combine any sections entitled History in the various original documents formi ng one secti on entitled History likewise combine any sections entitled Acknowledgements and any sections entitled Dedications You must delete all sections entitled Endorsements Heading 6 COLLECTIONS OF DOCUMENTS You may make a collection consisting of the Document and other doc uments released under this License and replace the individual copies of this License in the various documents with a single copy that is included in the collection provided that you follow the rules of this License for verbatim copying of each of the documents in all other respects You may extract a single document from such a collection and dis tribute it individually under this License provided you insert a copy of this License into the extracted document and follow this License in all other respects regarding verbatim copying of that document 7 AGGREGATION WITH INDEPENDENT WORKS A compilation of the Document or its derivatives with other separate and independent documents or works in or on a volume of a storage or distribution medium does not as a whole count as a Modified Ver sion of the Document pr
392. tibilities with other Ada libraries e pragma Locking Policy e pragma Queuing Policy e pragma Task Dispatching Policy e pragma Unreserve All Interrupts When using a library that contains such pragmas the user must make sure that all libraries use the same pragmas with the same values Otherwise a Program Error Will be raised during the elaboration of the conflicting libraries The usage of these pragmas and its consequences for the user should therefore be well documented Similarly the traceback in exception occurrences mechanism should be enabled or disabled in a consistent manner across all libraries Oth 238 3 May 2002 Chapter 16 GNAT and Libraries erwise a Program_Error will be raised during the elaboration of the conflicting libraries If the version and Body Version attributes are used inside a li brary then it is necessary to perform a gnatbind step that mentions all ali files in all libraries so that version identifiers can be properly com puted In practice these attributes are rarely used so this is unlikely to be a consideration 16 5 Rebuilding the GNAT Run Time Library It may be useful to recompile the GNAT library in various contexts the most important one being the use of partition wide configura tion pragmas such as Normalize Scalar A special Makefile called Makefile adalib is provided to that effect and can be found in the directory containing the GNAT library The location of this directo
393. time inputs For example if a program is executed with the command my program argi arg2 then gmem out can be analysed by gnatmem using the command gnatmem i gmem out my program argi arg2 18 3 Switches for gnatmem gnatmem recognizes the following switches q Quiet Gives the minimum output needed to identify the origin of the memory leaks Omit statistical information n N is an integer literal usually between 1 and 10 which controls the depth of the backtraces defining allocation root The default value for N is 1 The deeper the backtrace the more precise the localization of the root Note that the total number of roots can depend on this parameter o file Direct thegdb output tothe specified file The gab script used to generate this output is also saved in the file gnatmem tmp i file Do the gnatmem processing starting from file which has been generated by a previous call to gnatmem with the o switch or gmem out produced by GMEM mode This is useful for post mortem processing 18 4 Example of gnatmem Usage This section is based on the cpe mode of gnatmem The same results can be achieved using GMEM mode See section Section 18 2 Running gnatmem GM EM M ode page 248 Thefirst example shows the use of gnatmem on a simple leaking program Suppose that we have the following Ada program 249 GNAT User s Guide for Unix Platforms with Unchecked_Deallocation procedure Test_Gm is typ
394. tion gnatmake g stb bargs E stb Execution terminated by unhandled exception Exception name CONSTRAINT ERROR Message stb adb 5 Call stack traceback locations 0x401373 0x40138b 0x40139c 0x401335 Ox4011c4 Ox4011f1 0x77e892a4 addr2line exe stb 0x401373 0x40138b 0x40139c 0x401335 0x4011c4 Ox4011f1 0x77e892a4 285 GNAT User s Guide for Unix Platforms 00401373 at d stb stb adb 5 0040138B at d stb stb adb 10 0040139C at d stb stb adb 14 00401335 at d stb b stb adb 104 004011C4 at build crt1 c 200 004011F1 at build crt1 c 222 77E892A4 in at 77 0 addr21ine has a number of other useful options functions to get the function name corresponding to any location demangle gnat to use the gnat decoding mode for the function names Note that for binutils version 2 9 x the option is simply demangle addr2line exe stb functions demangle gnat 0x401373 0x40138b 0x40139c 0x401335 Ox4011c4 0x4011f1 00401373 in stb p1 at d stb stb adb 5 0040138B in stb p2 at d stb stb adb 10 0040139C in stb at d stb stb adb 14 00401335 in main at d stb b stb adb 104 004011C4 in lt __mingw_CRTStartup gt at build crti c 200 004011F1 in lt mainCRTStartup gt at build crt1 c 222 From this traceback wecan see that the exception was raised in stb adb at line 5 which was reached from a procedure call in stb adb at line 10 and so on The b std adb is the binder file which con
395. tle page Copyright c YEAR YOUR NAME Permission is granted to copy distribute and or modify this doc ument under the terms of the GNU Free Documentation Li cense Version 1 1 or any later version published by the Free Software Foundation with the Invariant Sections being LIST THEIR TITLES with the Front Cover Texts being LIST and with the Back Cover Texts being LIST A copy of the license is included in the section entitled GNU Free Documentation License If you have no Invariant Sections write with no Invariant Sections instead of saying which ones are invariant 1f you have no Front Cover Texts write no Front Cover Texts instead of Front Cover Texts being LIST likewise for Back Cover Texts If your document contains nontrivial examples of program code we recommend releasing these examples in parallel under your choice of free software license such as the GNU General PublicLicense to permit their use in free software 340 28 May 2002 Index Index f gnathtml ch creuen ea ssa 270 GCC gnatchop 129 Tf gnatlink 112 GCC compiler_name gnatlink 113 f gnatmake 117 GCC compiler_name gnatmake 116 fno inline gcc 331 GNATBIND binder_name gnatmake fstack check 244039853
396. try Size CPP TSD Prologue Size CPP TSD Entry Size Read comments in the source of this unit for more details 2 12 Comparison between GNAT and C C Compilation Models The GNAT model of compilation is dose to the C and C models You can think of Ada specs as corresponding to header files in C As in C you don t need to compile specs they are compiled when they are used The Ada with is similar in effect to the include of a C header One notable difference is that in Ada you may compile specs sep arately to check them for semantic and syntactic accuracy This is not always possible with C headers because they are fragments of programs that have less specific syntactic or semantic rules Theother major difference is the requirement for running the binder which performs two important functions First it checks for consistency In C or C the only defense against assembling inconsistent programs lies outside the compiler in a makefile for example The binder satisfies the Ada requirement that it be impossible to construct an inconsistent program when the compiler is used in normal mode Theother important function of the binder is to deal with elaboration issues There are also elaboration issues in C that are handled auto matically This automatic handling has the advantage of being simpler to use but the C programmer has no control over elaboration Where gnatbind might complain there was no valid order of elaboration a C
397. ttributes source Files and Source List File are given explicit values In this case the attribute source _ Files prevails E ach source file name must be the name of one and only one existing source filein one of the source directories A Source Files attribute defined with an empty list as its value indicates that there are no source files in the project Except for projects that are dearly specified as containing no Ada source files Source Dirs Or Source Files specified as an empty list or Languages Specified without Aaa in the list for Source Dirs use for Source Files use for Languages use C C a project must contain at least one immediate source Projects with no source files are useful as template packages see Section 10 8 Packages in Project Files page 160 for other projects in particular to define a package Naming see Section 10 10 Naming Schemes page 162 10 5 Importing Projects An immediate source of a project P may depend on source files that are neither immediate sources of P nor in the predefined library To get this effect P must import the projects that contain the needed source files 157 GNAT User s Guide for Unix Platforms with projecti utilities gpr with namings apex gpr project Main is As can be seen in this example the syntax for importing projects is similar to the syntax for importing compilation units in Ada However project files use literal strings i
398. txref and gnat find two tools that provide an easy way to navigate through sources Chapter 13 File Name Krunching Using gnatkr page 221 de scribes the gnatkr file name krunching utility used to handle short ened file names on operating systems with a limit on the length of names Chapter 14 Preprocessing Using gnatprep page 225 describes gnatprep a preprocessor utility that allows a single source file to be used to generate multiple or parameterized source files by means of macro substitution Chapter 15 TheGNAT Library Browser gnatls page 229 describes gnat1s a utility that displays information about compiled units in duding dependences on the corresponding sources files and consis tency of compilations Chapter 16 GNAT and Libraries page 233 describes the process of creating and using Libraries with GNAT It also describes how to recompile the GNAT run time library Chapter 17 Using the GNU make Utility page 241 describes some techniques for using the GNAT toolset in Makefiles Chapter 18 Finding Memory Problems with gnatmem page 247 describes gnatmem a utility that monitors dynamic allocation and deallocation activity in a program and displays information about incorrect deallocations and sources of possible memory leaks Chapter 19 Finding Memory Problems with GNAT Debug Pool page 255 describes how to use the GNAT specific Debug Pool in order to detect as early as possible the use
399. ubprogram is called For an object this means that the object must have been elaborated before its value is read or written A violation of either of these two requirements is an access before elaboration order and this section has been all about avoiding Such errors 205 GNAT User s Guide for Unix Platforms In the case where more than one order of elaboration is possible in the sense that access before elaboration errors are avoided then any one of the orders is correct in the sense that it meets the requirements of the Ada Reference Manual and no such error occurs H owever it may be the case for a given program that there are con straints on the order of elaboration that come not from consideration of avoiding elaboration errors but rather from extra lingual logic require ments Consider this example with Init_Constants package Constants is X Integer 0 Y Integer 0 end Constants package Init_Constants is procedure Calc end Init_Constants with Constants package body Init_Constants is procedure Calc is begin null end begin Constants X 3 Constants Y 4 end Init_Constants with Constants package Calc is Z Integer Constants X Constants Y end Calc with Calc with Text_I0 use Text I0 procedure Main is begin Put Line Calc Z Img end Main In this example there is more than one valid order of elaboration For example both the following are correct orders
400. unit then its spec is always elaborated before the unit doing the with Similarly a parent spec is always elaborated before the child spec and finally a spec is always elaborated before its corresponding body Dynamic elaboration checks Dynamic checks are made at run time so that if some en tity is accessed before it is elaborated typically by means of a subprogram call then the exception Program Error is raised Elaboration control Facilities are provided for the programmer to specify the de sired order of elaboration Let s look at these facilities in more detail First therules for dynamic checking One possible rule would be simply to say that the exception is raised if you access a variable which has not yet been elaborated The trouble with this approach is that it could require expensive checks on every variable reference Instead Ada 95 has two rules which area little more restrictive but easier to check and easier to state Restrictions on calls A subprogram can only be called at elaboration time if its body has been elaborated The rules for elaboration given above guarantee that the spec of the subprogram has been elaborated before the call but not the body If this rule is violated then the exception Program Error is raised Restrictions on instantiations A generic unit can only be instantiated if the body of the generic unit has been elaborated Again the rules for elab oration given above guarantee that the
401. unit in file abc def adb in semantic checking only mode 73 GNAT User s Guide for Unix Platforms M EEES O May 2002 Chapter 4 Binding Using gnatbind 4 Binding Using gnatbind This chapter describes the GNAT binder gnatbind which is used to bind compiled GNAT objects The gnatbind program performs four separate functions 1 Checks that a program is consistent in accordance with the rules in Chapter 10 of the Ada 95 Reference Manual In particular error messages are generated if a program uses inconsistent versions of a given unit 2 Checks that an acceptable order of elaboration exists for the pro gram and issues an error message if it cannot find an order of elabo ration that satisfies the rules in Chapter 10 of the Ada 95 Language Manual 3 Generates a main program incorporating the given elaboration or der This program is a small Ada package body and spec that must be subsequently compiled using the GNAT compiler The necessary compilation step is usually performed automatically by gnatlink The two most important functions of this program are to call the elaboration routines of units in an appropriate order and to call the main program 4 Determines the set of object files required by the given main pro gram This information is output in the forms of comments in the generated program to be read by the gnatlink utility used to link the Ada application 4 1 Running gnatbind The form of the gnatbind command
402. using the gnatE dynamic elab oration check switch then GNAT behaves in a quite dif ferent manner Dynamic checks are generated for all calls that could possibly result in raising an exception With this switch the compiler does not generate implicit Elaborate __ A11 pragmas The behavior then is exactly as specified in the Ada 95 Reference Manual The binder will generate an exe cutable program that may or may not raise Program Error andthen it is the programmer s job to ensure that it does not raise an exception Note that it is important to compile all units with the switch it cannot be used selectively Suppress checks The drawback of dynamic checks is that they generate a significant overhead at run time both in space and time If you are absolutely sure that your program cannot raise any elaboration exceptions and you still want to use the dynamic elaboration model then you can use the configura tion pragma Suppress Elaboration Checks to suppress all such checks For example this pragma could be placed in the gnat adc file Suppress checks selectively When you know that certain calls in elaboration code cannot possibly lead to an elaboration error and the binder never theless generates warnings on those calls and inserts Elab orate All pragmas that lead to elaboration circularities it is possible to remove those warnings locally and obtain a pro gram that will bind Clearly this can beunsafe and it is the respo
403. ute Exec Dir has a string value the path name of the exec directory The path name may be absolute or relativetothe directory of the project file This directory must already exist and be writable By default when the attribute Exec_Dir is not given an explicit value or when its value is the empty string the exec directory is the same as the object directory of the project file 10 4 3 Source Directories The source directories of a project are specified by the project file at tribute source Dirs This attribute s valueis a string list If the attribute is not given an explicit value then there is only one source directory the one where the project file resides A Source Dirs attribute that is explicitly defined to be the empty list as in for Source Dirs use indicates that the project contains no source files Otherwise each stringinthestring list designates one or more source directories for Source_Dirs use sources test drivers If a string in the list ends with then the directory whose path name precedes the two asterisks as well as all its subdirectories recur sively are source directories for Source Dirs use system sources Herethe directory system sources and all of its subdirectories recur sively are source directories To specify that the source directories are the directory of the project file and all of its subdirectories you can declare source Dirs as follows for Source Dirs us
404. ve example of Math Stuff Spec the GNAT binder will by default elaborate the body of math right after its spec so all will be well H owever a program that blindly relies on the binder to be helpful can get into trouble as we discussed in the previous sections so GNAT pro vides a number of facilities for assisting the programmer in developing programs that are robust with respect to elaboration order 11 6 Default Behavior in GNAT Ensuring Safety The default behavior in GNAT ensures elaboration safety In its default mode GNAT implements the rule we previously described as the right approach Let s restate it If a unit has daboration code that can directly or indirectly make a call to a subprogram in a witn ed unit or instantiate a generic unit in awith ed unit then if thewitn ed unit does not havepragma Pure Or Preelaborate then theclient should havean elaborate A11 for the with ed unit 190 U U u u u i 28 May 2002 Chapter 11 Elaboration Order Handling in GNAT By following this rule a client is assured that calls and instantiations can be made without risk of an exception In this mode GNAT traces all calls that are potentially made from elaboration code and puts in any missing implicit Elaborate A11 prag mas The advantage of this approach is that no elaboration problems are possibleif the binder can find an elaboration order that is consistent with these implicit Elaborate A11 pragmas The di
405. void gnat system finalization root SDP extern void gnat system finalization implementation SDP extern void gnat system string ops concat 3 SDP extern void gnat system stream attributes extern void gnat system file control block SDP extern void gnat ada finalization list controller void st 23 amp gnat hello SDP gnat ada text io SDP amp gnat ada exceptions SDP SDP exception table amp gnat gnat heap sort a amp gnat system SDP amp gnat system machine state operations amp gnat system secondary stack SDP gnat system parameters SDP soft links SDP stack checking SDP amp gnat system traceback SDP amp gnat system amp gnat system amp gnat ada streams SDP amp gnat ada tags SDP amp gnat system string ops SDP gnat interfaces c streams SDP amp gnat system file io SDP _SDP SDP 23 May 2002 Chapter 4 Binding Using gnatbind amp __gnat_ada__finalization__SDP amp __gnat_system__finalization_root__SDP amp __gnat_system__finalization_implementation__SDP amp __gnat_system__string_ops_concat_3__SDP amp __gnat_system__stream_attributes__SDP amp __gnat_system__file_control_block__SDP amp __gnat_ada__finalization__list_controller__SDP elabs extern void system__exceptions___elabs extern void ada__exceptions_ extern void interfaces__c_streams___elabs _elabb extern void ada
406. wherever possible uninitialized variables have invalid values See also the pragma validity_Checks Which allows modification of the validity checking mode at the program source level and also allows for temporary disabling of validity checks 3 2 4 Style Checking The gnatyx switch causes the compiler to enforce specified style rules A limited set of style rules has been used in writing the GNAT sources themselves This switch allows user programs to activate all or some of these checks If the source program fails a specified style check an ap propriate warning message is given preceded by the character sequence style The string x is a sequence of letters or digits indicating the particular style checks to be performed The following checks are de fined 1 9 specify indentation level If a digit from 1 9 appears in the string after gnaty then proper indentation is checked with the digit indicating the indentation level required The general style of required indentation is as specified by the examples in the Ada Refer ence Manual Full line comments must be aligned with the starting on a column that is a multiple of the alignment level a check attribute casing If the letter a appears in the string after gnaty then at tribute names including the case of keywords such as digits used as attributes names must be written in mixed case that is the initial letter and any letter following an underscore must be uppercas
407. wiseinitially empty Each invocation of the compiler will add the newly accessed sources to the mapping file This will improve the source search during the next invocation of the compiler Force recompilations Recompile all sources even though some object files may be up to date but don t recompile pre defined or GNAT internal files or locked files files with a write protected ALI file unless the a switch is also speci fied 117 GNAT User s Guide for Unix Platforms 118 In normal mode gnatmake compiles all object files and ALI files into the current directory If the i switch is used then instead object files and ALI files that already exist are over written in place This means that once a large project is organized into separate diredories in the desired manner then gnatmake will automatically maintain and update this organization If no ALI files are found on the Ada objed path Section 3 3 Search Paths and the Run Time Library RTL page 71 the new object and ALI files are created in the directory containing the source being compiled If an other organization is desired where objects and sources are kept in different directories a useful technique is to create dummy ALI files in the desired directories When detecting such a dummy file gnatmake will be forced to recompile the corresponding source file and it will be put the resulting ob ject and ALI files in the directory where it found the dummy file Use
408. witch activates warnings for conditional ex pressions used in tests that are known to be True or False at compiletime The default is that such warnings are not generated This warning can also be turned on using gnatwa 47 GNAT User s Guide for Unix Platforms AAAS gnatwC suppress warnings on conditionals This switch suppresses warnings for conditional expressions used in tests that are known to be True or False at compile time gnatwe treat warnings as errors This switch causes warning messages to be treated as errors The warning string still ap pears but the warning messages are counted as errors and prevent the generation of an object file gnatwf activate warnings on unreferenced formals This switch causes a warningto be generated if a formal parameter is not referenced in the body of the subprogram This warning can alsobeturned on using gnatwa Or gnatwu gnatwF suppress warnings on unreferenced formals This switch suppresses warnings for unrefer enced formal parameters Note that the combina tion gnatwu followed by gnatwr has the effect of warning on unreferenced entities other than subprogram formals gnatwh activate warnings on hiding This switch activates warnings on hiding deda rations A dedaration is considered hiding if it is for a non overloadable entity and it declares an entity with the same name as some other entity that is directly or use visible The default is that such warnings a
409. witch of the compiler activates a krunching circuit that limits file names to nn characters where nn is a decimal integer For example using OpenVMS where the maximum file name length is 39 the value of nn is usually set to 39 but if you want to generate a set of files that would be usable if ported to a system with some different maximum filelength then a different value can be specified The default value of 39 for OpenVMS need not be specified The gnatkr utility can be used to determine the krunched name for a given file when krunched to a specified maxi mum length 13 2 Using gnatkr The gnatkr command has the form gnatkr name length name Can bean Ada name with dots or the GNAT name of the unit where the dots representing child units or subunit are replaced by hyphens The only confusion arises if a name ends in ads Or adb gnatkr takes this to be an extension if there are no other dots in the name and the whole name is in lowercase length represents the length of the krunched name The default when no argument is given is 8 characters A length of zero stands for unlimited in other words do not chop except for system files which are always 8 221 GNAT User s Guide for Unix Platforms The output is the krunched name The output has an extension only if the original argument was a file name with an extension 13 3 Krunching Method The initial file name is determined by the name of the unit that the file contai
410. with one parameter the function returns the value of the external variable given as parameter If this name is not present in the environment then the returned value is an empty string In the form with two string parameters the second parameter is the value returned when the variable given as the first parameter is not present in the environment In the example above if os is not the name of an environment variable and is not passed on the command line then the returned value will be Linux An external reference may be part of a string expression or of a string list expression to define variables or attributes type Mode_Type is Debug Release Mode Mode_Type external MODE case Mode is when Debug gt 10 8 Packages in Project Files Thepackageis the project filefeaturethat defines thesettings for project aware tools For each such tool you can declare a corresponding package the names for these packages are preset see Section 10 3 2 Packages page 148 but are not case sensitive A package may contain variable declarations attribute declarations and case constructions project Proj is package Builder is used by gnatmake for Default_Switches Ada use v g end Builder end Proj A package declaration starts with the reserved word package followed by the package name case insensitive followed by the reserved word is It ends with the reserved word end followed by the packag
411. would actually occur SO Program Error might or might not be raised It is possible for a compiler to do a better job of analyzing bodies to de 187 GNAT User s Guide for Unix Platforms termine whether or not Program Error might be raised but it certainly couldn t do a perfect job that would require solving the halting problem and is provably impossible and because this is a warning anyway it does not seem worth the effort to do the analysis Cases in which it would be relevant are rare In practice warnings of either of the forms given above will usually correspond to real errors and should be examined carefully and elimi nated In the rare case where a warning is bogus it can be suppressed by any of the following methods e Compile with the gnatws Switch set e Suppress Elaboration Checks for the called subprogram e Usepragmawarnings_off to turn warnings off for the call For the internal elaboration check case GNAT by default generates the necessary run time checks to ensure that Program Error is raised if any call fails an elaboration check Of course this can only happen if a warn ing has been issued as described above The use of pragma suppress Elaboration Checks may but is not guaranteed to suppress some of these checks meaning that it may be possible but is not guaranteed for a program to be able to call a subprogram whose body is not yet elaborated without raising a Program Error exception 11 5 Controlling
412. xceptions procedure P1 is K Positive 1 begin K K 1 exception when E others gt Text I0 Put Line Exception Information end P1 procedure P2 is begin P1 end P2 begin P2 end STB This program will output stb Exception name CONSTRAINT ERROR Message stb adb 12 287 GNAT User s Guide for Unix Platforms Call stack traceback locations 0x4015e4 0x401633 0x401644 0x401461 0x4011c4 0x4011f1 0x77e892a4 23 13 1 3 Tracebacks From Anywhere in a Program It is also possible to retrieve a stack traceback from anywhere in a pro gram For this you need to use the GNAT Traceback API This package includes a procedure called ca11 Chain that computes a complete stack traceback as well as useful display procedures described below It is not necessary to use the E gnatbind option in this case because the stack traceback mechanism is invoked explicitly In the following example we compute a traceback at a specific location in the program and we display it using GNAT Debug Utilities Image to convert addresses to strings 288 88 May 2002 Chapter 23 Running and Debugging Ada Programs with Ada Text_I0 with GNAT Traceback with GNAT Debug_Utilities procedure STB is use Ada use GNAT use GNAT Traceback procedure P1 is Tracebacks_Array 1 10 We are asking for a maximum of 10
413. xtern void ada__io_exceptions___elabs PARAMS void extern void system__stack_checking___elabs PARAMS void extern void system__soft_links___elabb PARAMS void extern void system__secondary_stack___elabb PARAMS void extern void ada__tags___elabs PARAMS void 92 o gt gt gt gt o r r 23 May 2002 extern extern extern extern extern extern extern extern extern extern extern extern extern extern extern extern extern void void void void void void void void void void void void int _ Chapter 4 Binding Using gnatbind ada__tags___elabb PARAMS void ada__streams___elabs PARAMS void system__finalization_root___elabs PARAMS void _elabb PARAMS void _elabs PARAMS void system__finalization_implementation___elabb PARAMS void ada__finalization___elabs PARAMS void ada__finalization__list_controller___elabs PARAMS void system__file_control_block___elabs PARAMS void system__file_io___elabb PARAMS void ada__text_io___elabs PARAMS void ada__text_io___elabb PARAMS void ada__exceptions_ system__finalization_implementation_ _gnat_inside_elab_final_code int gnat_argc char char gnat argv gnat envp int gnat exit status char gnat version GNAT Version 3 15w 20010315 void adafinal system standard library adafinal void adainit extern extern ex
414. y Signature Model Type Found True Ada Text_I0 Put_Line Pentium OverDrive processor 60 66 end if Pentium OverDrive 75 90 100 120 133 150 166 200 if Signature Processor Type 2 01 and 2 0101 and 2 0010 then Signature Family Signature Model Type_Found True Ada Text_I0 Put_Line Pentium OverDrive cpu 75 90 100 120 133 150 166 200 end if Pentium OverDrive processor for x486 processor based systems if Signature Processor_Type 2 01 and 2 0101 and 2 0011 then Signature Family Signature Model Type_Found True Ada Text_I0 Put_Line Pentium OverDrive processor for x486 processor based systems end if Pentium processor with MMX technology 166 200 if Signature Processor Type 2 00 and 2 0101 and 2 0100 then Signature Family Signature Model Type Found True Ada Text IO Put Line Pentium processor with MMX technology 166 200 end if Pentium OverDrive with MMX for Pentium 75 90 100 120 133 if Signature Processor Type 2 01 and GNAT User s Guide for Unix Platforms 310 2 0101 and 2 0100 then Signature Family Signature Model Type_Found True Ada Text IO Put Line Pentium OverDrive processor with MMX amp technology for Pentium processor 75 90 100 120 133 end if Pentium Pro processor 24004 and 2401104 and 2400014 then if Signature Processor Type Signature Family Signatu
415. y then gnatxref and gnatfind Will extract the information from it If multiple project files are found none of them is read and you have to use the p switch to specify the one you want to use The following lines can be included even though most of them have default values which can be used in most cases The lines can be entered in any order in the file Except for src_dir and obj_dir you can only have one instance of each line If you have multiple instances only the last one is taken into account 213 GNAT User s Guide for Unix Platforms src_dir DIR default specifies a directory where to look for source files Multiple src_dir lines can be specified and they will be searched in the order they are specified obj_dir DIR default specifies a directory where to look for object and library files Multiple obj_dir lines can be specified and they will be searched in the order they are specified comp_opt SWITCHES default creates a variable which can be referred to subsequently by using the s comp_opt notation This is intended to store the default switches given to gnatmake and gcc bind_opt SWITCHES default creates a variable which can be referred to subsequently by using the bind opt notation This is intended to store the default switches given to gnatbind link opt SWITCHES default creates a variable which can be referred to subsequently by using the
416. y adding to the spec of Calc pragma Elaborate_All Constants which requires that the body if any and spec of Constants as well as the body and spec of any unit with ed by constants be elaborated before calc is elaborated Clearly no automatic method can always guess which alternative you require and if you are working with legacy code that had constraints of this kind which were not properly specified by adding Elaborate Or Elaborate All pragmas then indeed it is possible that two different compilers can choose different orders Thegnatbind p Switch may be useful in smoking out problems This switch causes bodies to be elaborated as late as possible instead of as early as possible In the example above it would have forced the choice of the first elaboration order If you get different results when usingthis switch and particularly if one set of results is right and one is wrong as far as you are concerned it shows that you havesome missing Elaborate pragmas For the example above we have the following output gnatmake f q main 207 GNAT User s Guide for Unix Platforms main 7 gnatmake f q main bargs p main 0 It is of course quite unlikely that both these results are correct so it is up to you in a case like this to investi gate the source of the difference by looking at the two elaboration orders that are chosen and figuring out which is correct and then adding the necessary Elaborate_A11 pragmas to ensure th
417. y of cps is the ability to call user defined subpro grams while debugging This is achieved simply by entering a subpro gram call statement in the form call subprogram name parameters The keyword call can be omitted in the normal case where the subprogram name does not coincide with any of the predefined cps com mands The effect is to invoke the given subprogram passing it the list of parameters that is supplied The parameters can be expressions and can include variables from the program being debugged The subpro gram must be defined at the library level within your program and GDB will call the subprogram within the environment of your program execu tion which means that the subprogram is free to access or even modify variables within your program The most important use of this facility is in allowing the inclusion of debugging routines that are tailored to particular data structures in your program Such debugging routines can be written to provide a suitably high level description of an abstract type rather than a low level dump of its physical layout After all the standard GDB print command only knows the physical layout of your types not their abstract meaning Debugging routines can provide information at the desired semantic level and are thus enormously useful 277 GNAT User s Guide for Unix Platforms For example when debugging GNAT itself it is crucial to have access to the contents of the tree nodes used t
418. z and ao r By default gnat find will output only the information about the dedaration body or type completion of the entities If this switch is set the gnat f ind will locate every reference to the entities in the files specified on the command line or in every filein the search path if nofileis given on the command line s If this switch is set then gnatfina will output the content of the Ada source file lines were the entity was found t If this switch is set then gnat find will output the type hi erarchy for the specified type It act like d option but recur sively from parent type to parent type When this switch is set it is not possible to specify more than one file All these switches may be in any order on the command line and may even appear after the file names They need not be separated by spaces thus you can Say gnatxref ag instead of gnatxref a g As stated previously gnatfind will search in every directory in the search path You can force it to look only in the current directory if you specify at the end of the command line 12 3 Project Files for gnatxref and gnatfind Project files allow a programmer to specify how to compile its application where to find sources These files are used primarily by the Glide Ada mode but they can also be used by the two tools gnat xref and gnat find A project file name must end with adp If a single one is present in the current director
419. ze and finalize the Ada units see Section 4 7 Binding with Non Ada Main Programs page 105 Callstotheinitialization and finalization routi nes must be inserted in the main program or some other appropriate point in the code The call to initialize the Ada units must occur before the first Ada subprogram is called and the call to finalize the Ada units must occur after the last Ada subprogram returns You use the same procedure for building the program as described previously In this case however the binder only places the initialization and finalization subprograms into file b xxx adb instead of the main program So if the main program is not in Ada you should proceed as follows 1 Compile the other language files to generate object files For in stance gcc c filei c gcc c file2 c 2 Compilethe Ada units to produce a set of object files and ALI files For instance gnatmake c entry point adb gnatmake c entry point2 adb 3 Run the Ada binder on the Ada main program For instance gnatbind n entry point ali entry point2 ali 4 LinktheAda main program the Ada objects and the other language objects You only need to give the last entry point here For instance gnatlink entry point2 ali filei o file2 o 2 10 2 Calling Conventions GNAT follows standard calling sequence conventions and will thus interface to any other languagethat also follows these conventions The following Convention identifiers are recogni
420. zed by GNAT e Ada This indicates that the standard Ada calling sequence will be used and all Ada data items may be passed without any limitations in the case where GNAT is used to generate both the caller and callee It is also possibleto mix GNAT generated code and code gen erated by another Ada compiler In this case the data types should be restricted to simple cases induding primitive types Whether 28 23 May 2002 Chapter 2 The GNAT Compilation Model complex data types can be passed depends on the situation Prob ably it is safe to pass simple arrays such as arrays of integers or floats Records may or may not work depending on whether both compilers lay them out identically Complex structures involving variant records access parameters tasks or protected types are unlikely to be able to be passed Note that in the case of GNAT running on a platform that supports DEC Ada 83 a higher degree of compatibility can be guaranteed and in particular records are layed out in an identical manner in the two compilers Note alsothat if output from two different compilers is mixed the program is responsible for dealing with elaboration issues Probably the safest approach is to write the main program in the version of Ada other than GNAT so that it takes care of its own elaboration requirements and then call the GNAT generated adainit procedure to en

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