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1. 6 IN SOLIB CALL TRAMPOLINE 46 IN SOLIB DYNSYM RESOLVE CODE 46 IN SOLIB RETURN TRAMPOLINE 46 inferior created id e p paese 92 INNER THAN 2 2 2 9 ga asides ea asa hahaa 46 insert or remove hardware breakpoint 5 insert or remove hardware watchpoint 5 ENT MAX e bo errestan aed ead ae uei dois 29 INT MIN xeu tate eR ER ERRRMRO RARE REPRE 29 INTEGER TU ADDRESS i065 Gan sa n Rh terere 4T IS ABSOLUTE PATH ome tas 72 IS DIE SEPARAT R 2 22 2 9 d gn ans 72 ISATTY 2122 ier bd arbor er doe aid edd and 29 item output functions 0005 13 K KERNEL U ADDR cs eric Rr RR ERR ers 60 KERNEL U ADDR HPUX z 6bluereeevd RR RR 61 L L SEE eete RES bL Ia Glo Peis weeded 30 language parser coceen trier ere RRECRIA d d 26 language support e ier RR REDE 26 legal papers for code contributions 90 length of SubOxp 5 B ee es AS 26 Peel ct wince adenine asekaqnt naaseewareesae 19 l biberty libratyi ei 3 eA Peete d 63 line wrap in output esee 67 TG joie Acree doit andre ganas Peut E sewn veiut iE Sees 30 list output functions s iesiere iss urrerieissp sti d LITTLE BREAKPDINT eu 2a eae ha taka ee 40 long long data type erresis eee ce eee ee 30 LONG MAX iz 23 000 c cats Dick Hoe ee detod heat Reba aaah ae 29 LONGEST 4232 hee Eum dbo Rp eR 29 longjmp debii ses cere etre Rer R ti 4 look p symbol 2122213 bp d
2. ui out field string uiout what b dll pathname ui out text uiout NX The following example from print_one_breakpoint shows how to use ui_out_field_ int and ui_out_spaces The original code was annotate_field 5 if b gt forked_inferior_pid 0 printf filtered process Ad b gt forked_inferior_pid It became annotate field 5 if b forked inferior pid 0 1 ui out text uiout process ui out field int uiout what b forked inferior pid ui out spaces uiout 1 F Here s an example of using ui_out_field_string The original code was annotate_field 5 if b gt exec_pathname NULL printf_filtered program s b gt exec_pathname It became annotate field 5 if b exec pathname NULL 1 ui out text uiout program V ui out field string uiout what b exec pathname ui out text uiout NX Finally here s an example of printing an address The original code annotate_field 4 printf filtered As hex string custom unsigned long b gt address 8 It became annotate field 4 ui out field core addr uiout Address b gt address 4 3 Console Printing 4 4 TUI Chapter 5 libgdb 19 5 libgdb 5 1 libgdb 1 0 libgdb 1 0 was an abortive project of years ago The theory was to provide an API to GDB s functionality 5 2 libgdb 2 0 libgdb 2 0 is an ongoing effort to update GDB so that is bet
3. 0 000 eee eee e ee eens 70 13 4 9 Pile Names vie ree Rex Bale E Ros 70 ii 13 4 10 Include Eles Ree RE ere 71 13 4 11 Clean Design and Portable Implementation 71 ld POLtine GODB ieiese4 49 dcxdecaneeweeesss ss 73 15 Versions and Branches 74 I5 WerstOWSIllSe fade oath Sede ede hou tate teed attests apiece cco eked 74 15 2 Release Branches 0 00 cc cece ce eee e eee e eens ens 75 15 3 Vendor Branches 0 00 0 e cece cece hee 75 15 4 Experimental Branches 0 000 e eee eee sees 75 15 1 Guidelines a end oe hak oie v len d d beh bad Red 5 MSA Ds UPA SS Cm 76 16 Releasing GDP s i ccssssessssseidnades ens TT 16 1 Branch Commit Policy tiers annaa aaea E 77 16 2 Obsoleting code cen Vetere ad eee e Rm ade 77 16 3 Before the Branch ueseeeeeeee Rn 78 16 3 1 Review the bug data base 0 0 ee eee eee 78 16 3 2 Check all cross targets build 0 00000 78 16 4 Cut the Branch a sessie oce mh ERR e gue ween 78 16 5 Stabilize the branch i obere cade O ee ede does 80 16 6 Create 3 Release aper e deh headers dade Geen 80 16 6 1 Create a release candidate 0 c cece ee ce eee 80 16 6 2 Sanity check the tar ball 0 000 220000 83 16 6 3 Make a release candidate available 0 83 16 6 4 Make a formal release available sess 84 10 0 5 Cleanup es uie ed ne x tm
4. 39 ADDRESS CLASS TYPE FLAGS sss 35 ADDRESS CLASS TYPE FLAGS byte size dwarf2 addr class sss 39 ADDRESS CLASS TYPE FLAGS P 39 ADDRESS CLASS TYPE FLAGS TO NAME 39 ADDRESS CLASS TYPE FLAGS TO NAME P 39 ADDRESS TU PUXNTER 22 0I bI 35 40 ADJUST BREAKPOINT ADDRESS 41 algorit ims ve ou vuoe d teet hdd add erectos 2 ALIGN STACK ON STARTUP 29 allocate symtab iov ler ere elena od 26 assumptions about targets 0 fal ATTR NORETURM terurai nnr Ose bed ks eel sy 30 B BELIEVE PCC PROMOTION 0 40 BED brary ie oc testes esate 62 BIG BREAKPOIME cese an ais aad ee Res 40 BITIS BIG ENDIAM iL vec dees toi oe RR 40 BPT VECTOR 4 226 28 be yuh keen ceo bes ewesemfemes 54 BREAKPOINT 6205 4 dg rieka ea dove ew doe 4 40 breakpoint address adjusted 41 BREAKPOINT_FROM PCi riser dee RR reRIRecEEewR 40 breakpoints 322 Pied a a a n 3 bug gdb mailing list 0 000 89 Appendix B Index C C data types ze Ro PR rrr re ETE 70 call stack frame ii sc ccuaceedee becueed epee ee 2 CALL DUMMY LOCATION ci cise ated ee 41 CANNOT_FETCH_REGISTER 41 CANNOT_STEP_HW_WATCHPOINTS 6 CANNOT STORE REGISTER osse 42 CC HAS LONG LONG sous lee RR 30 Char icue ge na SERRE DU EROR RTRR UR LE 32 CHI
5. is basically the same as a TYPE CODE INT type that is initialized in c lang c for an FT INTEGER fundamental type The difference is that the builtin type is not associated with any particular objfile and only one instance exists while c lang c builds as many TYPE CODE INT types as needed with each one associated with some particular objfile 6 4 Object File Formats 6 4 1 a out The a out format is the original file format for Unix It consists of three sections text data and bss which are for program code initialized data and uninitialized data respec tively The a out format is so simple that it doesn t have any reserved place for debugging information Hey the original Unix hackers used adb which is a machine language de bugger The only debugging format for a out is stabs which is encoded as a set of normal symbols with distinctive attributes The basic a out reader is in dbxread c 6 4 2 COFF The COFF format was introduced with System V Release 3 SVR3 Unix COFF files may have multiple sections each prefixed by a header The number of sections is limited Chapter 6 Symbol Handling 24 The COFF specification includes support for debugging Although this was a step for ward the debugging information was woefully limited For instance it was not possible to represent code that came from an included file The COFF reader is in coffread c 6 4 8 ECOFF ECOFF is an extended CO
6. void REGISTER CONVERT TO RAW struct type type int reg char Target Macro from char to Convert the value of register number reg to type which should always be DEPRECATED_ REGISTER VIRTUAL TYPE reg The buffer at from holds the register s value in raw format the macro should convert the value to virtual format and place it at to Note that REGISTER CONVERT TO VIRTUAL and REGISTER CONVERT TO RAWWM take their reg and type arguments in different orders 9 6 Using Different Register and Memory Data Representations Maintainer s note The way GDB manipulates registers is undergoing significant change Many of the macros and functions refered to in this section are likely to be subject to further Chapter 9 Target Architecture Definition 38 revision See A R Index and Bug Tracking Database for further information cagney 2002 05 06 Some architectures can represent a data object in a register using a form that is different to the objects more normal memory representation For example e The Alpha architecture can represent 32 bit integer values in floating point registers e The x86 architecture supports 80 bit floating point registers The long double data type occupies 96 bits in memory but only 80 bits when stored in a register In general the register representation of a data type is determined by the architecture or GDB s interface to the architecture while the memory representation is determined by the Applicat
7. iD mem erie er RE E Rd does 67 Write Pri racio truri eee ue pP PY ea Pire ae 53 WIILING bLests deiade eee uree e Oe one 88 X x86 debug registers crc ricsrcsrcsrerroridiod 6 XCOEF formatz Be5eie ae VELIS REIS 24
8. Builtin Types e g builtin type void builtin type char 23 6 4 Object File Formats 0 0 0 ce eee RR 23 GAN AOU sese eyes eet de Ee eee thas PUE QUE nea 23 O42 CORE cata ie etd ee eh ees 23 64 3 HOOP E sca Vases dates Ro vd qe A UR RR ae 24 GAA XCOEDR La detiene oe edet d mage 24 64 5 DEus A cs Bertin awa ach eh eo de 24 GAG PEE scat ete tee het eee eee Meee ne ee nat 24 6AT DOM Mr 24 6 4 8 Other File Formats ssseeseeee e 24 6 5 Debugging File Formats ssseeeeeee eee 24 MEE o EP 25 65 2 CORFE tia esaet pte x ORE ews VOLARE au e dare ee 25 6 5 3 Mips debug Third Eye 539293403 Praten dd dede Each ose 25 6 54 DWARE 1 52 13 eve iere Reto Ree e d 25 6 5 5 DWARF 2 einer kn e EE vau eb e Eb ERE aud 25 6 530 OM c aso cect htt bot ot oe pee oh nae SIM d Rite 25 6 6 Adding a New Symbol Reader to GDB 00 00 c eee eee 25 Language Support eres 26 7 1 Adding a Source Language to GDB 000 eens 26 Host Definition soosse ach Rohan OO Rode ie wees 27 8 1 Adding a New Host 0 0 c cece eee sinpi e 28 8 2 Host Conditionals 0 eee eee ene ee 28 Target Architecture Definition 31 9 1 Operating System ABI Variant Handling 31 9 2 Registers and Memory ssssessses enn 33 9 3 Pointers Are Not Always Addresses 0 000 eee eeee 33 9 4 Address Class s ossa noaea ee oe be Lee eel s 35 9 5 Raw and Virtual
9. GDB is a debugger It s not designed to be a front panel for embedded systems It s not a text editor It s not a shell It s not a programming environment GDB is an interactive tool Although a batch mode is available GDB s primary role is to interact with a human programmer GDB should be responsive to the user A programmer hot on the trail of a nasty bug and operating under a looming deadline is going to be very impatient of everything including the response time to debugger commands GDB should be relatively permissive such as for expressions While the compiler should be picky or have the option to be made picky since source code lives for a long time usually the programmer doing debugging shouldn t be spending time figuring out to mollify the debugger GDB will be called upon to deal with really large programs Executable sizes of 50 to 100 megabytes occur regularly and we ve heard reports of programs approaching 1 gigabyte in size GDB should be able to run everywhere No other debugger is available for even half as many configurations as GDB supports 2 Overall Structure GDB consists of three major subsystems user interface symbol handling the symbol side and target system handling the target side The user interface consists of several actual interfaces plus supporting code The symbol side consists of object file readers debugging info interpreters symbol table management source language expression
10. H 0 9 9 ce e 0000 00 00 is used as a date to pump prime the version in update mechanism e 90 and the previous branch version are used as fairly arbitrary initial branch version number Update the web and news pages Something Tweak cron to track the new branch The file gdbadmin cron crontab contains gdbadmin s cron table This file needs to be updated so that e a daily timestamp is added to the file version in e the new branch is included in the snapshot process Chapter 16 Releasing GDB 80 See the file gdbadmin cron README for how to install the updated cron table The file gdbadmin ss README should also be reviewed to reflect any changes That file is copied to both the branch and current snapshot directories Update the NEWS and README files The NEWS file needs to be updated so that on the branch it refers to changes in the current release while on the trunk it also refers to changes since the current release The README file needs to be updated so that it refers to the current release Post the branch info Send an announcement to the mailing lists e GDB Announcement mailing list e GDB Discsussion mailing list and GDB Discsussion mailing list Pragmatics The branch creation is sent to the announce list to ensure that people people not subscribed to the higher volume discussion list are alerted The announcement should include e the branch tag e how to
11. gt type bptypes int b gt type type internal error bptypes table does not describe type d int b gt type ui out field string uiout type bptypes int b gt type description annotate field 2 ui out field string uiout disp bpdisps int b disposition annotate field 3 ui out field fmt uiout enabled Ac bpenables int b enable This example also from print one breakpoint shows how to produce a complicated output field using the print expression functions which requires a stream to be passed It also shows how to automate stream destruction with cleanups The original code was annotate field 5 print expression b exp gdb stdout The new version is struct ui stream stb ui out stream new uiout struct cleanup old chain make cleanup ui out stream delete stb annotate field 5 print expression b gt exp stb gt stream ui_out_field_stream uiout what local_stream This example also from print_one_breakpoint shows how to use ui_out_text and ui_out_field_string The original code was annotate_field 5 if b dll pathname NULL printf filtered any library else printf filtered library s b dll pathname Chapter 5 libgdb 18 It became annotate field 5 if b dll pathname NULL 1 ui out field string uiout what lt any library gt ui out spaces uiout 1 else ui_out_text uiout library
12. struct cleanup old make cleanup ui out stream delete mybuf do cleanups old If the function already has the old cleanup chain set for other kinds of cleanups you just have to add your cleanup to it mybuf ui out stream new uiout make cleanup ui out stream delete mybuf Note that with cleanups in place you should not call ui out stream delete directly or you would attempt to free the same buffer twice Chapter 4 User Interface 15 4 2 5 Utility Output Functions void ui out field skip struct ui out uiout const char fldname Function This function skips a field in a table Use it if you have to leave an empty field without disrupting the table alignment The argument fldname specifies a name for the missing filed void ui out text struct ui out uiout const char string Function This function outputs the text in string in a way that makes it easy to be read by humans For example the console implementation of this method filters the text through a built in pager to prevent it from scrolling off the visible portion of the screen Use this function for printing relatively long chunks of text around the actual field data the text it produces is not aligned according to the table s format Use ui out field string to output a string field and use ui out message described below to output short messages void ui out spaces struct ui_out uiout int nspaces Function This function outputs n
13. type doesn t even have an enumeration for I O watchpoints this feature is not yet available to GDB running on x86 2 x86 processors can enable watchpoints locally for the current task only or globally for all the tasks For each debug register there s a bit in the DR7 Debug Control register that determines whether the associated address is watched locally or globally The current implementation of x86 watchpoint support in GDB always sets watchpoints to be locally enabled since global watchpoints might interfere with the underlying OS and are probably unavailable in many platforms 3 9 Observing changes in GDB internals In order to function properly several modules need to be notified when some changes occur in the GDB internals Traditionally these modules have relied on several paradigms the most common ones being hooks and gdb events Unfortunately none of these paradigms was versatile enough to become the standard notification mechanism in GDB The fact that they only supported one client was also a strong limitation A new paradigm based on the Observer pattern of the Design Patterns book has there fore been implemented The goal was to provide a new interface overcoming the issues with the notification mechanisms previously available This new interface needed to be strongly typed easy to extend and versatile enough to be used as the standard interface when adding new notifications See Appendix A GDB Observers pa
14. 16 4 Cut the Branch Create the branch u 5 1 v 5 2 V echo v sed s N g D date u Y m 7 d Chapter 16 Releasing GDB 79 echo u V D 5 1 5_2 2002 03 03 echo cvs f d ext sources redhat com cvs src rtag D D gmt gdb V D branchpoint insight dejagnu cvs f d ext sources redhat com cvs src rtag D 2002 03 03 gmt gdb 5 2 2002 03 03 branchpoint insight dejagnu echo echo cvs f d ext sources redhat com cvs src rtag b r gdb_ V D branchpoint gdb V branch insight dejagnu cvs f d ext sources redhat com cvs src rtag b r gdb 5 2 2002 03 03 branchpoint gdb 5 2 branch insight dejagnu echo e by using D YYYY MM DD gmt the branch is forced to an exact date time e the trunk is first taged so that the branch point can easily be found e Insight which includes GDB and dejagnu are all tagged at the same time e version in gets bumped to avoid version number conflicts e the reading of cvsrc is disabled using f Update version in u 5 1 v 5 2 V echo v sed s N g echo u v V 5 1 5 2 cd tmp echo cvs f d ext sources redhat com cvs src co r gdb V branch src gdb version in cvs f d ext sources redhat com cvs src co r gdb 5 2 branch src gdb version in echo src gdb version in cd src gdb echo u 90 0000 00 00 cvs gt version in cat version in 1 90 0000 00 00 cvs cvs f commit version in
15. 40 BREAKPOINT FROM PC pcptr lenptr Use the program counter to determine the contents and size of a breakpoint instruction It returns a pointer to a string of bytes that encode a breakpoint instruction stores the length of the string to lenptr and adjusts the pro gram counter if necessary to point to the actual memory location where the breakpoint should be inserted Although it is common to use a trap instruction for a breakpoint it s not required for instance the bit pattern could be an invalid instruction The breakpoint must be no longer than the shortest instruction of the architecture Replaces all the other BREAKPOINT macros Chapter 9 Target Architecture Definition 41 MEMORY INSERT BREAKPOINT addr contents cache MEMORY REMOVE BREAKPOINT addr contents cache Insert or remove memory based breakpoints Reasonable defaults default memory insert breakpoint and default nemory remove breakpoint respectively have been provided so that it is not necessary to define these for most architectures Architectures which may want to define MEMORY INSERT BREAKPOINT and MEMORY REMOVE BREAKPOINT will likely have instructions that are oddly sized or are not stored in a conventional manner It may also be desirable from an efficiency standpoint to define custom break point insertion and removal routines if BREAKPOINT FROM PC needs to read the target s memory for some reason ADJUST BREAKPOINT ADDRESS addres
16. BFD This is beyond the scope of this document You must then arrange for the BFD code to provide access to the debugging symbols Generally GDB will have to call swapping routines from BFD and a few other BFD internal routines to locate the debugging information As much as possible GDB should not depend on the BFD internal data structures For some targets e g COFF there is a special transfer vector used to call swapping routines since the external data structures on various platforms have different sizes and layouts Specialized routines that will only ever be implemented by one object file format may be called directly This interface should be described in a file bfd libxyz h which is included by GDB Chapter 7 Language Support 26 7 Language Support GDB s language support is mainly driven by the symbol reader although it is possible for the user to set the source language manually GDB chooses the source language by looking at the extension of the file recorded in the debug info c means C f means Fortran etc It may also use a special purpose language identifier if the debug format supports it like with DWARF 7 1 Adding a Source Language to GDB To add other languages to GDB s expression parser follow the following steps Create the expression parser This should reside in a file lang exp y Routines for building parsed expres sions into a union exp element list are in parse c
17. BFD will identify a variety of file types including a out coff and several vari ants thereof as well as several kinds of core files access to sections of files BFD parses the file headers to determine the names virtual addresses sizes and file locations of all the various named sections in files such as the text section or the data section GDB simply calls BFD to read or write section x at byte offset y for length z specialized core file support BFD provides routines to determine the failing command name stored in a core file the signal with which the program failed and whether a core file matches i e could be a core dump of a particular executable file locating the symbol information GDB uses an internal interface of BFD to determine where to find the symbol information in an executable file or symbol file GDB itself handles the reading of symbols since BFD does not understand debug symbols but GDB uses BFD s cached information to find the symbols string table etc 12 2 opcodes The opcodes library provides GDB s disassembler It s a separate library because it s also used in binutils for objdump 12 3 readline 12 4 mmalloc Chapter 12 Support Libraries 63 12 5 libiberty The libiberty library provides a set of functions and features that integrate and improve on functionality found in modern operating systems Broadly speaking such features can be divided into three groups supplemental functi
18. DUMMY FRAME TOS sp Used in call function by hand to notify the target dependent code of the top of stack value that will be passed to the the inferior code This is the value of the SP after both the dummy frame and space for parameters results have been allocated on the stack See unwind dummy id page 53 SDB REG TO REGNUM Define this to convert sdb register numbers into GDB regnums If not defined no conversion will be done enum return value convention gdbarch return value struct gdbarch gdbarch struct type valtype struct regcache regcache void readbuf const void writebuf Given a function with a return value of type rettype return which return value convention that function would use GDB currently recognizes two function return value conventions RETURN VALUE REGISTER CONVENTION where the return value is found in registers and RETURN VALUE STRUCT CONVENTION where the return value is found in memory and the address of that memory location is passed in as the function s first parameter If the register convention is being used and writebuf is non NULL also copy the return value in writebuf into regcache If the register convention is being used and readbuf is non NULL also copy the return value from regcache into readbuf regcache contains a copy of the registers from the just returned function Chapter 9 Target Architecture Definition 51 See DEPRECATED_EXTRACT_STRUCT_VALUE_ADDRESS page 43 for a
19. FP eme RR RuR ad 53 TARGET READ PG 2sis ew deor he pee 53 TARGET READ SP 222 Seeds RPepe me R dup aug as 53 TARGET REGION OK FOR HW WATCHPOINT 5 TARGET REGION SIZE OK FOR HW WATCHPOINT 5 target remove hw breakpoint 5 target remove watchpoint 9 TARGET SHORT BIT 222mm REP adislouace 52 target stopped data address 6 TARGET VIRTUAL FRAME POINTER 53 TARGET WRLTE PO sec Rx RITE RA 53 TCP remote support eeeese esee 28 TBEPEILES 3219 4 bau Soe died daa nce d du 54 terminal devices ssr cid saeco pete AEA 22 29 Lest SUILC zo det owed e dab Me eds 86 test suite organization ise ne 87 trimming language dependent code 27 tuple output functions 000 qr CYPE ie eee deed a acne ed diea dab ds 3T type CodeS amp Lettere De eter Taie 28 ngu EE 70 U U REGS OFFSET ordered r Oxide ea beeen ees 61 i out functions seris trespas bl p Redes oe he 10 ui_out functions usage examples 15 ui out field core addr 14 ui o t field fmt gasa vbt us LP PR 13 ui out field fmt int iecore 13 ur out field int 2 2 wes ah bari ER 13 ui out field skip ooo ss ienakter okait 15 ui out field stream sees 14 ui out field string tekpre deg 14 WI gut flush onRI pP ud ae duane 15 ui out list begin RR keep os 13 ui out list end hs sic 4h 3 werd sh ded ected
20. Register Representations 36 9 6 Using Different Register and Memory Data Representations 37 9 7 Frame Interpretation ssessleeeeeee nnn 38 9 8 Inferior Call Setup ssueeessseeeesee re 39 9 9 Compiler Characteristics sssseeeeeee een 39 9 10 Target Conditionals secese rnenika nenia a a e 39 9 11 Adding a New Target 0 0 cece eee eee aa a 54 9 12 Converting an existing Target Architecture to Multi arch 55 9 12 1 Preparations wi need mide tian eden bea od eod eA dde 55 9 12 2 Add the multi arch initialization code Lis 55 ii 9 12 3 Update multi arch incompatible mechanisms 56 9 12 4 Prepare for multi arch level to one 00005 56 9 12 5 Set multi arch level one issesleess else ee eee 56 9 12 6 Convert remaining macros sseeesee ees 56 9 12 7 Set multi arch level to two cee eee eee 57 9 12 8 Delete the TM file lusus 57 10 Target Vector Definition 57 10 1 File Targets ere een eee Chetan Pad cae 57 10 2 Standard Protocol and Remote Stubs 004 5T 10 3 ROM Monitor Interface 0 0 0c nh 57 10 4 Custom Protocols 0 0 cece eee nn 58 10 5 Transport Layer 0 ccac 4 emet one x ieee deena eae 58 10 6 Builtin Simulator se saaat aaao cece eee aE EE ARS 58 11 Native Debugging eee 58 11 1 Native core file Support 0c cec
21. Renesas D10V is a 16 bit VLIW processor whose instructions are 32 bits long If the D10V used ordinary byte addresses to refer to code locations then the processor would only be able to address 64kb of instructions However since instructions must be aligned on four byte boundaries the low two bits of any valid instruction s byte address are always zero byte addresses waste two bits So instead of byte addresses the D10V uses word addresses byte addresses shifted right two bits to refer to code Thus the D10V can use 16 bit words to address 256kb of code space However this means that code pointers and data pointers have different forms on the D10V The 16 bit word 0xC020 refers to byte address 0xC020 when used as a data address but refers to byte address 0x30080 when used as a code address The D10V also uses separate code and data address spaces which also affects the correspondence between pointers and addresses but we re going to ignore that here this example is already too long To cope with architectures like this the D10V is not the only one GDB tries to dis tinguish between addresses which are byte numbers and pointers which are the targets representation of an address of a particular type of data In the example above 0xC020 is the pointer which refers to one of the addresses 0xC020 or 0x30080 depending on the type imposed upon it GDB provides functions for turning a pointer into an address and vice versa in t
22. a struct cmd_list_element as it s first argument You can use the return value from add_com or add_cmd to deprecate the command immediately after it is created The first time a command is used the user will be warned and offered a replacement if one exists Note that the replacement string passed to deprecate_cmd should be the full name of the command i e the entire string the user should type at the command line 4 2 UI Independent Output the ui out Functions The ui_out functions present an abstraction level for the GDB output code They hide the specifics of different user interfaces supported by GDB and thus free the programmer from the need to write several versions of the same code one each for every UI to produce output 4 2 1 Overview and Terminology In general execution of each GDB command produces some sort of output and can even generate an input request Output can be generated for the following purposes e to display a result of an operation e to convey info or produce side effects of a requested operation e to provide a notification of an asynchronous event including progress indication of a prolonged asynchronous operation e to display error messages including warnings e to show debug data e to query or prompt a user for input a special case This section mainly concentrates on how to build result output although some of it also applies to other kinds of output Generation of output that dis
23. adjusted breakpoint is initially set and each time that that breakpoint is hit CALL DUMMY LOCATION See the file inferior h This method has been replaced by push dummy code see push dummy code page 50 CANNOT FETCH REGISTER regno A C expression that should be nonzero if regno cannot be fetched from an inferior process This is only relevant if FETCH INFERIOR REGISTERS is not defined Chapter 9 Target Architecture Definition 42 CANNOT STORE REGISTER regno A C expression that should be nonzero if regno should not be written to the target This is often the case for program counters status words and other special registers If this is not defined GDB will assume that all registers may be written int CONVERT REGISTER P regnum Return non zero if register regnum can represent data values in a non standard form See Chapter 9 Using Different Register and Memory Data Representa tions page 31 DECR_PC_AFTER_BREAK Define this to be the amount by which to decrement the PC after the program encounters a breakpoint This is often the number of bytes in BREAKPOINT though not always For most targets this value will be 0 DISABLE_UNSETTABLE_BREAK addr If defined this should evaluate to 1 if addr is in a shared library in which breakpoints cannot be set and so should be disabled PRINT FLOAT INFO If defined then the info float command will print information about the processor s floating point un
24. and files listed below but these mostly exist for historical reasons and will eventually disappear gdb config arch xyz mh This file once contained both host and native configuration information see Chapter 11 Native Debugging page 58 for the machine xyz The host con figuration information is now handed by Autoconf Host configuration information included a definition of XM_FILE xm xyz h and possibly definitions for CC SYSV DEFINE XM CFLAGS XM ADD FILES XM CLIBS XM CDEPS etc see Makefile in New host only configurations do not need this file gdb config arch xm xyz h This file once contained definitions and includes required when hosting gdb on machine xyz Those definitions and includes are now handled by Autoconf New host and native configurations do not need this file Maintainer s note Some hosts continue to use the xm xyz h file to define the macros HOST_FLOAT_FORMAT HOST DOUBLE FORMAT and HOST LONG DOUBLE FORMAT That code also needs to be replaced with either am Autoconf or run time test Generic Host Support Files There are some generic versions of routines that can be used by various systems These can be customized in various ways by macros defined in your xm xyz h file If these routines work for the xyz host you can just include the generic file s name with o not sre in XDEPFILES Otherwise if your machine needs custom support routines you will
25. are identical and no special handling is needed However they do occasionally differ For example e The x86 architecture supports an 80 bit long double type However when we store those values in memory they occupy twelve bytes the floating point number occupies the first ten and the final two bytes are unused This keeps the values aligned on four byte boundaries allowing more efficient access Thus the x86 80 bit floating point type is the raw representation and the twelve byte loosely packed arrangement is the virtual representation e Some 64 bit MIPS targets present 32 bit registers to GDB as 64 bit registers with garbage in their upper bits GDB ignores the top 32 bits Thus the 64 bit form with garbage in the upper 32 bits is the raw representation and the trimmed 32 bit representation is the virtual representation In general the raw representation is determined by the architecture or GDB s interface to the architecture while the virtual representation can be chosen for GDB s convenience Chapter 9 Target Architecture Definition 37 GDB s register file registers holds the register contents in raw format and the GDB remote protocol transmits register values in raw format Your architecture may define the following macros to request conversions between the raw and virtual format int REGISTER CONVERTIBLE int reg Target Macro Return non zero if register number reg s value needs different raw and virtual forma
26. bytes beyond the innermost stack address reserved by the ABI A function is permitted to use this scratch area instead of allocating extra stack space When performing an inferior function call to ensure that it does not modify this area GDB adjusts the innermost stack address by frame red zone size bytes before pushing parameters onto the stack By default zero bytes are allocated The value must be aligned see frame align page 43 The AMD64 nee x86 64 ABI documentation refers to the red zone when de scribing this scratch area DEPRECATED_FRAME_CHAIN frame Given frame return a pointer to the calling frame Chapter 9 Target Architecture Definition 44 DEPRECATED FRAME CHAIN VALID chain thisframe Define this to be an expression that returns zero if the given frame is an outer most frame with no caller and nonzero otherwise Most normal situations can be handled without defining this macro including NULL chain pointers dummy frames and frames whose PC values are inside the startup file e g crt0 0 inside main or inside start DEPRECATED FRAME INIT SAVED REGS frame See frame h Determines the address of all registers in the current stack frame storing each in frame gt saved_regs Space for frame gt saved_regs shall be allocated by DEPRECATED FRAME INIT SAVED REGS using frame saved regs zalloc FRAME FIND SAVED REGS is deprecated FRAME NUM ARGS fi For the frame described by
27. check out the branch using CVS e the date number of weeks until the release e the branch commit policy still holds 16 5 Stabilize the branch Something goes here 16 6 Create a Release The process of creating and then making available a release is broken down into a number of stages The first part addresses the technical process of creating a releasable tar ball The later stages address the process of releasing that tar ball When making a release candidate just the first section is needed 16 6 1 Create a release candidate The objective at this stage is to create a set of tar balls that can be made available as a formal release or as a less formal release candidate Freeze the branch Send out an e mail notifying everyone that the branch is frozen to gdb patches sources redhat comn j Establish a few defaults b gdb_5_2 branch v 5 2 t sourceware snapshot tmp gdbadmin tmp echo t b v sourceware snapshot tmp gdbadmin tmp gdb 5 2 branch 5 2 mkdir p t b v Chapter 16 Releasing GDB 81 cd t b v pwd sourceware snapshot tmp gdbadmin tmp gdb 5 2 branch 5 2 which autoconf home gdbadmin bin autoconf Notes e Check the autoconf version carefully You want to be using the ver sion taken from the binutils snapshot directory which can be found at ftp sources redhat com pub binutils It is very unlikely that a system installed version of autoconf e g usr bin autoconf i
28. clean design for GDB If the maintainers don t have time to put the patch in when it arrives or if there is any question about a patch it goes into a large queue with everyone else s patches and bug reports The legal issue is that to incorporate substantial changes requires a copyright assign ment from you and or your employer granting ownership of the changes to the Free Soft ware Foundation You can get the standard documents for doing this by sending mail to gnu gnu org and asking for it We recommend that people write in All programs owned by the Free Software Foundation as NAME OF PROGRAM so that changes in many programs not just GDB but GAS Emacs GCC etc can be contributed with only one piece of legalese pushed through the bureaucracy and filed with the FSF We can t start merging changes until this paperwork is received by the FSF their rules which we follow since we maintain it for them Technically the easiest way to receive changes is to receive each feature as a small context diff or unidiff suitable for patch Each message sent to me should include the changes to C code and header files for a single feature plus ChangeLog entries for each directory where files were modified and diffs for any changes needed to the manuals gdb doc gdb texinfo or gdb doc gdbint texinfo If there are a lot of changes for a single feature they can be split down into multiple messages In this way if we read and l
29. code required for this native support of this machine On some machines it doesn t exist at all There are some generic versions of routines that can be used by various systems These can be customized in various ways by macros defined in your nm xyz h file If these routines work for the xyz host you can just include the generic file s name with 0 not s c in NATDEPFILES Otherwise if your machine needs custom support routines you will need to write routines that perform the same functions as the generic file Put them into xyz nat c and put xyz nat o into NATDEPFILES inftarg c This contains the target_ops vector that supports Unix child processes on sys tems which use ptrace and wait to control the child procfs c This contains the target_ops vector that supports Unix child processes on sys tems which use proc to control the child fork child c This does the low level grunge that uses Unix system calls to do a fork and exec to start up a child process Chapter 11 Native Debugging 59 infptrace c This is the low level interface to inferior processes for systems using the Unix ptrace call in a vanilla way 11 1 Native core file Support core aout c fetch_core_registers Support for reading registers out of a core file This routine calls register_addr see below Now that BFD is used to read core files virtually all machines should use core aout c and s
30. defining 1386_USE_GENERIC_ WATCHPOINTS e Add i386 nat o to the value of the Make variable NATDEPFILES see Chapter 11 Na tive Debugging page 58 or TDEPFILES see Chapter 9 Target Architecture Definition page 31 e Provide implementations for the 1386 DR LOW macros described below Typically each macro should call a target specific function which does the real work The x86 watchpoint support works by maintaining mirror images of the debug registers Values are copied between the mirror images and the real debug registers via a set of macros which each target needs to provide I386 DR LOW SET CONTROL val Set the Debug Control DR7 register to the value val I386 DR LOW SET ADDR idx addr Put the address addr into the debug register number idx I386 DR LOW RESET ADDR idx Reset i e zero out the address stored in the debug register number idx I386 DR LOW GET STATUS Return the value of the Debug Status DR6 register This value is used im mediately after it is returned by I386 DR LOW GET STATUS so as to support per thread status register values For each one of the 4 debug registers whose indices are from 0 to 3 that store addresses a reference count is maintained by GDB to allow sharing of debug registers by several watchpoints This allows users to define several watchpoints that watch the same expression but with different conditions and or commands without wasting debug registers which a
31. description of how return values that use the struct convention are handled Maintainer note This method replaces separate predicate extract store meth ods By having only one method the logic needed to determine the return value convention need only be implemented in one place If GDB were written in an OO language this method would instead return an object that knew how to perform the register return value extract and store Maintainer note This method does not take a gcc_p parameter and such a parameter should not be added If an architecture that requires per compiler or per function information be identified then the replacement of rettype with struct value function should be persued Maintainer note The regcache parameter limits this methods to the inner most frame While replacing regcache with a struct frame_info frame parameter would remove that limitation there has yet to be a demonstrated need for such a change SKIP_PERMANENT_BREAKPOINT Advance the inferior s PC past a permanent breakpoint GDB normally steps over a breakpoint by removing it stepping one instruction and re inserting the breakpoint However permanent breakpoints are hardwired into the inferior and can t be removed so this strategy doesn t work Calling SKIP_PERMANENT_ BREAKPOINT adjusts the processor s state so that execution will resume just after the breakpoint This macro does the right thing even when the breakpoint is in the delay slot of a bran
32. fatal This means that changes such as adding a new architec tures or within reason support for a new host are considered acceptable 16 2 Obsoleting code Before anything else poke the other developers and around the source code to see if there is anything that can be removed from GDB an old target an unused file Obsolete code is identified by adding an OBSOLETE prefix to every line Doing this means that it is easy to identify something that has been obsoleted when greping through the sources The process is done in stages this is mainly to ensure that the wider GDB community has a reasonable opportunity to respond Remember everything on the Internet takes a week 1 Post the proposal on the GDB mailing list Creating a bug report to track the task s state is also highly recommended Wait a week or so Post the proposal on the GDB Announcement mailing list Wait a week or so C ges oe bo Go through and edit all relevant files and lines so that they are prefixed with the word OBSOLETE 6 Wait until the next GDB version containing this obsolete code has been released Chapter 16 Releasing GDB 78 7 Remove the obsolete code Maintainer note While removing old code is regrettable it is hopefully better for GDB s long term development Firstly it helps the developers by removing code that is either no longer relevant or simply wrong Secondly since it removes any history associated with the file effect
33. fi return the number of arguments that are being passed If the number of arguments is not known return 1 DEPRECATED FRAME SAVED PC frame Given frame return the pc saved there This is the return address This method is deprecated See unwind pc page 44 CORE ADDR unwind pc struct frame info this frame Return the instruction address in this frame s caller at which execution will resume after this frame returns This is commonly refered to as the return address The implementation which must be frame agnostic work with any frame is typically no more than ULONGEST pc frame unwind unsigned register this frame D10V PC REGNUM amp pc return di0v make iaddr pc See DEPRECATED_FRAME_SAVED PC page 44 which this method re places CORE ADDR unwind sp struct frame info this frame Return the frame s inner most stack address This is commonly refered to as the frame s stack pointer The implementation which must be frame agnostic work with any frame is typically no more than ULONGEST sp frame unwind unsigned register this frame D10V SP REGNUM amp sp return di0v make daddr sp See TARGET_READ_SP page 53 which this method replaces FUNCTION EPILOGUE SIZE For some COFF targets the x sym x misc x fsize field of the function end symbol is 0 For such targets you must define FUNCTION EPILOGUE SIZE to expand into the standard size of a function s epilogue Chapter 9 Target A
34. first create a ui stream object by calling ui out stream new pass the stream member of that ui stream object to value print and similar functions and finally call ui out field stream to output the field you constructed When the ui stream object is no longer needed you should destroy it and free its memory by calling ui out stream delete struct ui stream ui out stream new struct ui_out uiout Function This function creates a new ui stream object which uses the same output methods as the ui out object whose pointer is passed in uiout It returns a pointer to the newly created ui stream object void ui out stream delete struct ui_stream streambuf Function This functions destroys a ui stream object specified by streambuf void ui out field stream struct ui out uiout const char Function fieldname struct ui stream streambuf This function consumes all the data accumulated in streambuf gt stream and out puts it like ui out field string does After a call to ui out field stream the accumulated data no longer exists but the stream is still valid and may be used for producing more fields Important If there is any chance that your code could bail out before completing output generation and reaching the point where ui out stream delete is called it is necessary to set up a cleanup to avoid leaking memory and other resources Here s a skeleton code to do that struct ui stream mybuf ui out stream new uiout
35. h Also add the printed representations of your operators to op print tab Add a place of call Add a call to lang parse and lang_error in parse exp 1 defined in parse c Use macros to trim code The user has the option of building GDB for some or all of the languages If the user decides to build GDB for the language lang then every file dependent on language h will have the macro _LANG_lang defined in it Use ifdefs to leave out large routines that the user won t need if he or she is not using your language Note that you do not need to do this in your YACC parser since if GDB is not build for lang then lang exp tab o the compiled form of your parser is not linked into GDB at all See the file configure in for how GDB is configured for different languages Edit Makefile in Add dependencies in Makefile in Make sure you update the macro variables such as HFILES and OBJS otherwise your code may not get linked in or worse yet it may not get tarred into the distribution 8 Host Definition With the advent of Autoconf it s rarely necessary to have host definition machinery any more The following information is provided mainly as an historical reference Chapter 8 Host Definition 28 8 1 Adding a New Host GDB s host configuration support normally happens via Autoconf New host specific defini tions should not be needed Older hosts GDB still use the host specific definitions
36. handler corresponding to osabi to fine tune the gdbarch structure specified by gdbarch If a handler corresponding to osabi has not been registered for gdbarch s architecture a warning will be issued and the debugging session will continue with the defaults already established for gdbarch Chapter 9 Target Architecture Definition 33 9 2 Registers and Memory GDB s model of the target machine is rather simple GDB assumes the machine includes a bank of registers and a block of memory Each register may have a different size GDB does not have a magical way to match up with the compiler s idea of which registers are which however it is critical that they do match up accurately The only way to make this work is to get accurate information about the order that the compiler uses and to reflect that in the REGISTER NAME and related macros GDB can handle big endian little endian and bi endian architectures 9 3 Pointers Are Not Always Addresses On almost all 32 bit architectures the representation of a pointer is indistinguishable from the representation of some fixed length number whose value is the byte address of the object pointed to On such machines the words pointer and address can be used interchangeably However architectures with smaller word sizes are often cramped for address space so they may choose a pointer representation that breaks this identity and allows a larger code address space For example the
37. is either a pointer or a C reference type See Chapter 9 Pointers Are Not Always Addresses page 31 BELIEVE PCC PROMOTION Define if the compiler promotes a short or char parameter to an int but still reports the parameter as its original type rather than the promoted type BITS BIG ENDIAN Define this if the numbering of bits in the targets does not match the endianness of the target byte order A value of 1 means that the bits are numbered in a big endian bit order 0 means little endian BREAKPOINT This is the character array initializer for the bit pattern to put into memory where a breakpoint is set Although it s common to use a trap instruction for a breakpoint it s not required for instance the bit pattern could be an invalid instruction The breakpoint must be no longer than the shortest instruction of the architecture BREAKPOINT has been deprecated in favor of BREAKPOINT FROM PC BIG BREAKPOINT LITTLE BREAKPOINT Similar to BREAKPOINT but used for bi endian targets BIG BREAKPOINT and LITTLE BREAKPOINT have been deprecated in favor of BREAKPOINT FROM PC DEPRECATED REMOTE BREAKPOINT DEPRECATED LITTLE REMOTE BREAKPOINT DEPRECATED BIG REMOTE BREAKPOINT Specify the breakpoint instruction sequence for a remote target DEPRECATED_ REMOTE BREAKPOINT DEPRECATED BIG REMOTE BREAKPOINT and DEPRECATED_ LITTLE REMOTE BREAKPOINT have been deprecated in favor of BREAKPOINT_ FROM PC see BREAKPOINT FROM PC page
38. it is not possible to use one of the specialized versions see below void ui out field int struct ui out uiout const char fldname Function int value This function outputs a value of an int variable It uses the 4d output conversion specification fldname specifies the name of the field void ui out field fmt int struct ui out uiout int width enum Function ui_align alignment const char fldname int value This function outputs a value of an int variable It differs from ui out field int in that the caller specifies the desired width and alignment of the output fldname specifies the name of the field 1 The function cast is not portable ISO C Chapter 4 User Interface 14 void ui out field core addr struct ui out uiout const char Function fldname CORE ADDR address This function outputs an address void ui out field string struct ui out uiout const char Function fldname const char string This function outputs a string using the As conversion specification Sometimes there s a need to compose your output piece by piece using functions that operate on a stream such as value print or fprintf symbol filtered These functions accept an argument of the type struct ui file a pointer to a ui file object used to store the data stream used for the output When you use one of these functions you need a way to pass their results stored in a ui file object to the ui out functions To this end you
39. name with the name matching that used in the actual function definition All external functions should have a declaration in a header file that callers include except for initialize functions which must be external so that init c construction works but shouldn t be visible to random source files Where a source file needs a forward declaration of a static function that declaration must appear in a block near the top of the source file 13 4 8 Internal Error Recovery During its execution GDB can encounter two types of errors User errors and internal errors User errors include not only a user entering an incorrect command but also problems arising from corrupt object files and system errors when interacting with the target Internal errors include situations where GDB has detected at run time a corrupt or erroneous situation When reporting an internal error GDB uses internal error and gdb assert GDB must not call abort or assert Pragmatics There is no internal warning function Either the code detected a user error recovered from it and issued a warning or the code failed to correctly recover from the user error and issued an internal error 13 4 9 File Names Any file used when building the core of GDB must be in lower case Any file used when building the core of GDB must be 8 3 unique These requirements apply to both source and generated files Pragmatics The core of GDB must be buildable on many platforms includi
40. need to write routines that perform the same functions as the generic file Put them into xyz xdep c and put xyz xdep o into XDEPFILES ser unix c This contains serial line support for Unix systems This is always included via the makefile variable SER HARDWIRE override this variable in the mh file to avoid it ser go32 c This contains serial line support for 32 bit programs running under DOS using the DJGPP a k a GO32 execution environment ser tcp c This contains generic TCP support using sockets 8 2 Host Conditionals When GDB is configured and compiled various macros are defined or left undefined to control compilation based on the attributes of the host system These macros and their Chapter 8 Host Definition 29 meanings or if the meaning is not documented here then one of the source files where they are used is indicated are GDBINIT FILENAME The default name of GDB s initialization file normally gdbinit NO STD REGS This macro is deprecated SIGWINCH HANDLER If your host defines SIGWINCH you can define this to be the name of a function to be called if SIGWINCH is received SIGWINCH HANDLER BODY Define this to expand into code that will define the function named by the expansion of SIGWINCH_HANDLER ALIGN STACK ON STARTUP Define this if your system is of a sort that will crash in tgetent if the stack happens not to be longword aligned when main is called This is a rare s
41. read or may be called alone if all symbols are simply being discarded xyz symfile read struct sym fns sf CORE ADDR addr int mainline Called from symbol file add to actually read the symbols from a symbol file into a set of psymtabs or symtabs sf points to the struct sym fns originally passed to xyz sym init for possible initialization addr is the offset between the file s specified start address and its true address in memory mainline is 1 if this is the main symbol table being read and 0 if a secondary symbol file e g shared library or dynamically loaded file is being read In addition if a symbol reading module creates psymtabs when xyz symfile read is called these psymtabs will contain a pointer to a function xyz psymtab to symtab which can be called from any point in the GDB symbol handling code Xyz psymtab to symtab struct partial symtab pst Called from psymtab to symtab or the PSYMTAB TO SYMTAB macro if the psymtab has not already been read in and had its pst gt symtab pointer set The argument is the psymtab to be fleshed out into a symtab Upon return pst gt readin should have been set to 1 and pst gt symtab should contain a Chapter 6 Symbol Handling 22 pointer to the new corresponding symtab or zero if there were no symbols in that part of the symbol file 6 2 Partial Symbol Tables GDB has three types of symbol tables e Full symbol tables symtabs These contain the main information ab
42. single release branch and identifies that branch using the Cvs branch tags gdb major minor YYYY MMDD branchpoint gdb major minor branch Egdb major minor YYYY MMDD release Pragmatics To help identify the date at which a branch or release is made both the branchpoint and release tags include the date that they are cut YYYY MMDD in the tag The branch tag denoting the head of the branch does not meed this 15 3 Vendor Branches To avoid version conflicts vendors are expected to modify the file gdb version in to include a vendor unique alphabetic identifier an official GDB release never uses alphabetic characters in its version identifer E g 66 2widgit2 or 6 2 Widgit Inc Patch 2 15 4 Experimental Branches Chapter 15 Versions and Branches 76 15 4 1 Guidelines GDB permits the creation of branches cut from the CVS repository for experimental develop ment Branches make it possible for developers to share preliminary work and maintainers to examine significant new developments The following are a set of guidelines for creating such branches a branch has an owner The owner can set further policy for a branch but may not change the ground rules In particular they can set a policy for commits be it adding more reviewers or deciding who can commit all commits are posted All changes committed to a branch shall also be posted to the GDB patches mailing list While commentary on such changes a
43. some chips Typically these work by having dedicated register into which the breakpoint address may be stored If the PC shorthand for program counter ever matches a value in a breakpoint registers the CPU raises an exception and reports it to GDB Another possibility is when an emulator is in use many emulators include circuitry that watches the address lines coming out from the processor and force it to stop if the address matches a breakpoint s address A third possibility is that the target already has the ability to do breakpoints somehow for instance a ROM monitor may do its own software breakpoints So although these are not literally hardware breakpoints from GDB s point of view they work the same GDB need not do anything more than set the breakpoint and wait for something to happen Since they depend on hardware resources hardware breakpoints may be limited in num ber when the user asks for more GDB will start trying to set software breakpoints On some architectures notably the 32 bit x86 platforms GDB cannot always know whether there s enough hardware resources to insert all the hardware breakpoints and watchpoints On those platforms GDB prints an error message only when the program being debugged is continued Software breakpoints require GDB to do somewhat more work The basic theory is that GDB will replace a program instruction with a trap illegal divide or some other instruction that will cause an exception a
44. some of the specific target definitions that they use 3 1 Frames A frame is a construct that GDB uses to keep track of calling and called functions FRAME FP in the machine description has no meaning to the machine independent part of GDB except that it is used when setting up a new frame from scratch as follows Chapter 3 Algorithms 3 create new frame read register DEPRECATED FP REGNUM read pc Other than that all the meaning imparted to DEPRECATED FP REGNUM is imparted by the machine dependent code So DEPRECATED FP REGNUM can have any value that is convenient for the code that creates new frames create new frame calls DEPRECATED INIT EXTRA FRAME INFO if it is defined that is where you should use the DEPRECATED FP REGNUM value if your frames are nonstandard Given a GDB frame define DEPRECATED FRAME CHAIN to determine the address of the calling function s frame This will be used to create a new GDB frame struct and then DEPRECATED INIT EXTRA FRAME INFO and DEPRECATED INIT FRAME PC will be called for the new frame 3 2 Breakpoint Handling In general a breakpoint is a user designated location in the program where the user wants to regain control if program execution ever reaches that location There are two main ways to implement breakpoints either as hardware breakpoints or as software breakpoints Hardware breakpoints are sometimes available as a builtin debugging features with
45. store typed address eee BUIUCUIOI 3146 11 diranen ana a ee dad fede struct value converting register contents to submitting patches 5 0 eee eee eens sym fns SUTUCLUFG ses csc m rr Rer wee Ee symbol files 2e eRop IRR ee ERIPIP AR symbol lookup es rreRR LEHRER RS symbol reading sicca csrersicsurierererrscceri SYMBOL RELOADING DEFAULT SYMBOLS CAN START WITH DOLLAR Symitabs purea eere PE anes system dependencies 0 e ee ee eee T table output functions 0005 targetes sd eked Adee c trnk rin wide dee encodes target architecture definition target vector 2 2 2 x gp er deed e aie Sane eerste eh dins TARGET_CAN_USE_HARDWARE_WATCHPOINT target changed oi weds adduced TARGET CHAR BIT 3 i ev sonia geese dices darn TARGET_CHAR_SIGNED 000000 0eee TARGET COMPLEX BIT eem ege TARGET D UBLE BIT eo erena mI emen TARGET DOUBLE COMPLEX BIT TARGET FLOAT BIT aienea Ree eme bes TARGET HAS HARDWARE WATCHPOINTS 103 target insert hw breakpoint 5 target insert watchpoint 5 TARGET INT BIT igus zeige mer RR REPE 52 TARGET L NG BIT ibn Rn Ree eps 52 TARGET_LONG_DOUBLE_BIT 52 TARGET_LONG_LONG_BIT 52 TARGET PRINT INSN 5 en ee RR RES 53 TARGET PTR BIT 4 46irxs negra oie dau 52 TARGET READ
46. the gdb info or gdb p exp tab c They were generated and yes gdb info 1 was also generated only something strange with CVS means that they didn t get supressed Fixing it would be nice though Create compressed versions of the release cp src tar cp src bz2 1s F dejagnu dejagnu gdb 5 2 tar bz2 gdb gdb 5 2 tar insight insight 5 2 tar for m in gdb insight do bzip2 v 9 c m v tar m v tar bz2 gzip v 9 c m v tar gt m v tar gz done Note e A pipe such as bunzip2 lt xxx bz2 gzip 9 gt xxx gz is not since in that mode gzip does not know the name of the file and hence can not include it in the compressed file This is also why the release process runs tar and bzip2 as separate passes 16 6 2 Sanity check the tar ball Pick a popular machine Solaris PPC and try the build on that bunzip2 lt gdb 5 2 tar bz2 tar xpf cd gdb 5 2 configure make gdb gdb gdb gdb GNU gdb 5 2 gdb b main Breakpoint 1 at 0x80732bc file main c line 734 gdb run Starting program tmp gdb 5 2 gdb gdb Breakpoint 1 main argc 1 argv Oxbffff8b4 at main c 734 734 catch errors captured main amp args RETURN MASK ALL gdb print args 1 argc 136426532 argv Ox821b7f0 gdb 16 6 3 Make a release candidate available If this is a release candidate then the only remaining steps are 1 Commit version in and ChangeLog 2 Tweak v
47. 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 List on the Title Page as authors one or more persons or entities 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 fewer than five unless they release you from this requirement State on the Title page the name of the publisher of the Modified Version as the publisher Preserve all the copyright notices of the Document Add an appropriate copyright notice for your modifications adjacent to the other copyright notices 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 Preserve in that license notice the full lists of Invariant Sections and required Cover Texts given in the Document s license notice Include an unaltered copy of this License Preserve the section Entitled History Preserve 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 Docu ment create one stating the title year authors and publisher of the Document as given on its Title Page then add
48. time The GDB testsuite uses the DejaGNU testing framework DejaGNU is built using Tcl and expect The tests themselves are calls to various Tcl procs the framework runs all the procs and summarizes the passes and fails 17 1 Using the Testsuite To run the testsuite simply go to the GDB object directory or to the testsuite s objdir and type make check This just sets up some environment variables and invokes DejaGNU s runtest script While the testsuite is running you ll get mentions of which test file is in use and a mention of any unexpected passes or fails When the testsuite is finished you ll get a summary that looks like this gdb Summary of expected passes 6016 of unexpected failures 58 of unexpected successes 5 of expected failures 183 of unresolved testcases 3 of untested testcases 5 The ideal test run consists of expected passes only however reality conspires to keep us from this ideal Unexpected failures indicate real problems whether in GDB or in the testsuite Expected failures are still failures but ones which have been decided are too hard to deal with at the time for instance a test case might work everywhere except on AIX and there is no prospect of the AIX case being fixed in the near future Expected failures should not be added lightly since you may be masking serious bugs in GDB Unexpected successes are expected fails that are passing for some reason while unresolved and unteste
49. use VALUE TO REGISTER with registers for which the CONVERT REGISTER P macro returns a non zero value void REGISTER CONVERT TO TYPE int regnum struct type type Target Macro char buf See mips tdep c It does not do what you want 9 7 Frame Interpretation Chapter 9 Target Architecture Definition 9 8 Inferior Call Setup 9 9 Compiler Characteristics 9 10 Target Conditionals This section describes the macros that you can use to define the target machine ADDR BITS REMOVE addr If a raw machine instruction address includes any bits that are not really part of the address then define this macro to expand into an expression that zeroes those bits in addr This is only used for addresses of instructions and even then not in all contexts For example the two low order bits of the PC on the Hewlett Packard PA 2 0 architecture contain the privilege level of the corresponding instruction Since instructions must always be aligned on four byte boundaries the pro cessor masks out these bits to generate the actual address of the instruction ADDR BITS REMOVE should filter out these bits with an expression such as Caddr amp 7 3 ADDRESS CLASS NAME TO TYPE FLAGS name type flags ptr If name is a valid address class qualifier name set the int referenced by type flags ptr to the mask representing the qualifier and return 1 If name is not a valid address class qualifier name return 0 The value for t
50. works correctly and M q fills the block consistently Put a blank line between the block comments preceding function or variable definitions and the definition itself Chapter 13 Coding TO In general put function body comments on lines by themselves rather than trying to fit them into the 20 characters left at the end of a line since either the comment or the code will inevitably get longer than will fit and then somebody will have to move it anyhow 13 4 6 C Usage Code must not depend on the sizes of C data types the format of the hosts floating point numbers the alignment of anything or the order of evaluation of expressions Use functions freely There are only a handful of compute bound areas in GDB that might be affected by the overhead of a function call mainly in symbol reading Most of GDB s performance is limited by the target interface whether serial line or system call However use functions with moderation A thousand one line functions are just as hard to understand as a single thousand line function Macros are bad M kay But if you have to use a macro make sure that the macro arguments are protected with parentheses Declarations like struct foo should be used in preference to declarations like typedef struct foo foo_ptr 13 4 7 Function Prototypes Prototypes must be used when both declaring and defining a function Prototypes for GDB functions must include both the argument type and
51. ARE SINGLE STEP must also be defined SOFTWARE SINGLE STEP signal insert breapoints p A function that inserts or removes depending on insert breapoints p break points at each possible destinations of the next instruction See sparc tdep c and rs6000 tdep c for examples SOFUN ADDRESS MAYBE MISSING Somebody clever observed that the more actual addresses you have in the debug information the more time the linker has to spend relocating them So whenever there s some other way the debugger could find the address it needs you should omit it from the debug info to make linking faster SOFUN ADDRESS MAYBE MISSING indicates that a particular set of hacks of this sort are in use affecting N S0 and N FUN entries in stabs format debugging in formation N S0 stabs mark the beginning and ending addresses of compilation units in the text segment N_FUN stabs mark the starts and ends of functions SOFUN ADDRESS MAYBE MISSING means two things Chapter 9 Target Architecture Definition 49 e N FUN stabs have an address of zero Instead you should find the addresses where the function starts by taking the function name from the stab and then looking that up in the minsyms the linker assembler symbol table In other words the stab has the name and the linker assembler symbol table is the only place that carries the address e N SO stabs have an address of zero too You just look at the N_FUN stabs that appear before
52. ARM Embedded ABI version 2 GDB OSABI ARM APCS Generic ARM Procedure Call Standard Here are the functions that make up the OS ABI framework const char gdbarch osabi name enum gdb_osabi osabi Function void void enum void Return the name of the OS ABI corresponding to osabi gdbarch_register_osabi enum bfd architecture arch unsigned Function long machine enum gdb_osabi osabi void init_osabi struct gdbarch info info struct gdbarch gdbarch Register the OS ABI handler specified by init osabi for the architecture machine type and OS ABI specified by arch machine and osabi In most cases a value of zero for the machine type which implies the architecture s default machine type will suffice gdbarch register osabi sniffer enum bfd architecture Function arch enum b fd flavour flavour enum gdb osabi sniffer bfd abfd Register the OS ABI file sniffer specified by sniffer for the BFD architecture flavour pair specified by arch and flavour If arch is b d arch unknown the sniffer is consid ered to be generic and is allowed to examine flavour flavoured files for any architec ture gdb_osabi gdbarch_lookup_osabi bfd abfd Function Examine the file described by abfd to determine its OS ABI The value GDB_OSABI_ UNKNOWN is returned if the OS ABI cannot be determined gdbarch_init_osabi struct gdbarch info info struct gdbarch Function gdbarch enum gdb_osabi osabi Invoke the OS ABI
53. B calls this observer immediately after connecting to the inferior and before any information on the inferior has been printed void solib_loaded struct so_list solib Function The shared library specified by solib has been loaded Note that when GDB calls this observer the library s symbols probably haven t been loaded yet Appendix B GNU Free Documentation License 93 void solib unloaded struct so list solib Function The shared library specified by solib has been unloaded Appendix B GNU Free Documentation License Version 1 2 November 2002 Copyright c 2000 2001 2002 Free Software Foundation Inc 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 functional and useful 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 non commercially 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 Public License which is a copyle
54. BLE Define this if the host C compiler supports long double This is set by the configure script PRINTF HAS LONG DOUBLE Define this if the host can handle printing of long double float point numbers via the printf format conversion specifier Lg This is set by the configure script SCANF HAS LONG DOUBLE Define this if the host can handle the parsing of long double float point numbers via the scanf format conversion specifier Lg This is set by the configure script LSEEK NOT LINEAR Define this if 1seek n does not necessarily move to byte number n in the file This is only used when reading source files It is normally faster to define CRLF SOURCE FILES when possible L SET This macro is used as the argument to 1seek or most commonly bfd seek FIXME should be replaced by SEEK SET instead which is the POSIX equiv alent NORETURN If defined this should be one or more tokens such as volatile that can be used in both the declaration and definition of functions to indicate that they never return The default is already set correctly if compiling with GCC This will almost never need to be defined ATTR_NORETURN If defined this should be one or more tokens such as __attribute noreturn that can be used in the declarations of functions to indicate that they never return T he default is already set correctly if compiling with GCC This will almost never need to be defined SEEK CUR SEEK SET Define these to appropr
55. D EXTRACT STRUCT VALUE ADDRESS regbuf When defined extract from the array regbuf containing the raw register state the CORE ADDR at which a function should return its structure value See gdbarch return value page 50 DEPRECATED EXTRACT STRUCT VALUE ADDRESS P Predicate for DEPRECATED EXTRACT STRUCT VALUE ADDRESS DEPRECATED FP REGNUM If the virtual frame pointer is kept in a register then define this macro to be the number greater than or equal to zero of that register This should only need to be defined if DEPRECATED TARGET READ FP is not defined DEPRECATED FRAMELESS FUNCTION INVOCATION fi Define this to an expression that returns 1 if the function invocation represented by fi does not have a stack frame associated with it Otherwise return 0 frame align address Define this to adjust address so that it meets the alignment requirements for the start of a new stack frame A stack frame s alignment requirements are typically stronger than a target processors stack alignment requirements see DEPRECATED_STACK_ALIGN page 51 This function is used to ensure that when creating a dummy frame both the initial stack pointer and if needed the address of the return value are correctly aligned Unlike DEPRECATED STACK ALIGN this function always adjusts the address in the direction of stack growth By default no frame based stack alignment is performed int frame red zone size The number of
56. De ibe aes 4 3 8 Watchpoints 4 1 geek eernivcb eere aces beta i 4 9 81 x86 WatChpOiits 2 3 is deter pt ded tend eique end 6 3 9 Observing changes in GDB internals ss lesse esses 9 4 User Interface eeee eene 9 4 1 Command Interpreter sesseeeeeseeeeee ene 9 4 2 Ul Independent Output the ui out Functions 10 4 2 Overview and Terminology 0 000000 cece eeeee 10 4 2 2 General Conventions 0 0 0 0 cece eee eee eee 11 4 2 3 Table Tuple and List Functions 11 4 2 4 Item Output Functions ssssesessse esee 13 4 2 5 Utility Output Functions lisse esses esses 15 4 2 6 Examples of Use of ui out functions 15 4 3 Console Printing essiens sue eect ra de Meee a on C ERR US 18 AAe WN Mer M eem 18 3 liptdhy stestcuisedsncdewawng che toe Rd 19 b libedb 3b ce cece a eun orte ro e EE aac ate E eee 19 5 2 libgdb 2 0 5 4 eop Eb E c p a eor RR date de d 19 5 3 The libgdb Model sseesseeeee ees 19 5A ODDS ppOLTU 2 eed aami ak ed ed d pen ede ud eode d a 19 0 9 J bgdb components reinserire ie moe Ea RC Ie etri 20 6 Symbol Handling 222499299 x Vr RS 20 6 1 Symbol Reading 0 cece n 20 6 2 Partial Symbol Tables 0 0 eee eee ete eee 22 nhu TT 23 Fundamental Types e g FT VOID FT_BOOLEAN 23 Type Codes e g TYPE CODE PTR TYPE CODE ARRAY 23
57. FF originally introduced for Mips and Alpha workstations The basic ECOFF reader is in mipsread c 6 4 4 XCOFF The IBM RS 6000 running AIX uses an object file format called XCOFF The COFF sections symbols and line numbers are used but debugging symbols are dbx style stabs whose strings are located in the debug section rather than the string table For more information see section Top in The Stabs Debugging Format The shared library scheme has a clean interface for figuring out what shared libraries are in use but the catch is that everything which refers to addresses symbol tables and breakpoints at least needs to be relocated for both shared libraries and the main executable At least using the standard mechanism this can only be done once the program has been run or the core file has been read 6 4 5 PE Windows 95 and NT use the PE Portable Executable format for their executables PE is basically COFF with additional headers While BFD includes special PE support GDB needs only the basic COFF reader 6 4 6 ELF The ELF format came with System V Release 4 SVRA Unix ELF is similar to COFF in being organized into a number of sections but it removes many of COFF s limitations The basic ELF reader is in elfread c 6 4 7 SOM SOM is HP s object file and debug format not to be confused with IBM s SOM which is a cross language ABI The SOM reader is in hpread c 6 4 8 Other File Fo
58. GDB Internals A guide to the internals of the GNU debugger John Gilmore Cygnus Solutions Second Edition Stan Shebs Cygnus Solutions Cygnus Solutions Revision TpXinfo 2004 02 19 09 Copyright c 1990 1991 1992 1993 1994 1996 1998 1999 2000 2001 2002 2003 2004 2005 Free Software Foundation Inc 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 no Invariant Sections with no Front Cover Texts and with no Back Cover Texts A copy of the license is included in the section entitled GNU Free Documentation License Table of Contents Scope of this Document 0006 1 1 JXiedqultemeltibsa 22 mee eere I er a en 1 2 Overall Structure a soss orba eR RR RU RH OR 1 2 1 The Symbol Side susrasa esigia aiaa adiaka a E aa eene 2 2 2 The Target Slide cr rer irin is RE EE ERG 2 2 9 Configurations 44 3 3 daw mia edd E ated e EUR EUR ea eee 2 3 XISOPU DS ossretews9r ku EE ER RER E SEES 2 SMaEocuIDI C r 2 3 2 Breakpoint Handling 22 44 oc rs rp o a de eu 3 3 3 Single Stepping cue we eee tre kiere tpe it ig Rn d ee 4 38 4 Signal Handling pesine niana ga cece hr 4 3 5 Thread Handling 0 0 0 cece nh 4 3 6 Inferior Function Calls sesio ni eaii eee eee ees 4 o4 Long jmp SUpport aeree eee karate prt We n ee e Rec
59. Insight is used since that contains more of the release than GDB dejagnu doesn t get tagged but I think we can live with that Mention the release on the trunk Just put something in the ChangeLog so that the trunk also indicates when the release was made Restart gdb version in If gdb version in does not contain an ISO date such as 2002 01 24 then the daily cronjob won t update it Having committed all the release changes it can be set to 5 2 0_0000 00 00 cvs which will restart things yes the _ is important it affects the snapshot process Don t forget the ChangeLog Merge into trunk The files committed to the branch may also need changes merged into the trunk Chapter 17 Testsuite 86 Revise the release schedule Post a revised release schedule to GDB Discussion List with an updated announcement The schedule can be generated by running ss schedule date s schedule The first parameter is approximate date time in seconds from the epoch of the most recent release Also update the schedule cronjob 16 7 Post release Remove any OBSOLETE code 17 Testsuite The testsuite is an important component of the GDB package While it is always worthwhile to encourage user testing in practice this is rarely sufficient users typically use only a small subset of the available commands and it has proven all too common for a change to cause a significant regression that went unnoticed for some
60. L U ADDR Define this to the address of the u structure the user struct also known as the u page in kernel virtual memory GDB needs to know this so that it can subtract this address from absolute addresses in the upage that are obtained via ptrace or from core files On systems that don t need this value set it to Zero Chapter 11 Native Debugging 61 KERNEL U ADDR HPUX Define this to cause GDB to determine the address of u at runtime by using HP style nlist on the kernel s image in the root directory ONE PROCESS WRITETEXT Define this to be able to when a breakpoint insertion fails warn the user that another process may be running with the same executable PROC NAME FMT Defines the format for the name of a proc device Should be defined in nm h only in order to override the default definition in procfs c PTRACE_ARG3_TYPE The type of the third argument to the ptrace system call if it exists and is different from int REGISTER_U_ADDR Defines the offset of the registers in the u area SHELL_COMMAND_CONCAT If defined is a string to prefix on the shell command used to start the inferior SHELL_FILE If defined this is the name of the shell to use to run the inferior Defaults to bin sh SOLIB_ADD filename from tty targ readsyms Define this to expand into an expression that will cause the symbols in filename to be added to GDB s symbol table If readsyms is zero symbols are not re
61. LD PREPARE TO STORE 60 Clean p sorssv ere er ePes rbeian mgonicgus 13 GIOATIUPS esiin dup icto ro REO Pt orn ead 64 CEEAR SOLIB pod 21222 urhe oid don Edda 62 GED n ani edatea naka ea i nan a X U RES 9 code pointers word addressed 39 coding standards J esee reb Exe mE ERE 67 COFF debugging info 25 COFF format 2x eter deadatagiaee IAE 29 command implementation 89 command interpreter leeeees eese 9 comment formatting 00002 69 compiler Warnings 4222 9x eR LEES 68 CU NVERT REGISTER P m gece 38 42 converting between pointers and addresses 33 converting integers to addresses 47 converting targets to multi arch 55 create new frame eee nen 2 CRLF SUURCE FILES 22 22cez6 4a pe Ree Res 29 current language se sels esee 27 D D10V addresses 0 cece leeren 33 data Output otc peudcietdidspeedinshdeusv eons 13 data pointer per architecture per module 65 DEBUG PIRACE n ouem bte 62 debugging GDB isa cis ce RISO ae ber Pees 89 DECR PC AFTER BREAK ossis coh 2000 42 DEFAULT PROMPT 22 Soe ewes a ae ak ee 29 deprecate cmd osa Rr Rep ES 10 DEPRECATED BIG REMOTE BREAKPOINT 40 DEPRECATED EXTRACT STRUCT VALUE ADDRESS 43 DEPRECATED EXTRACT STRUCT VALUE ADDRESS P nM 43 DE
62. Le Rot e a p eni ee aes 85 1676 WROSt Release eme iorum ates dns emu reta 86 14 eS ed ds oe ee ardua css qaid 86 17 1 Using the Testsuite sssssssseeesse ne 86 17 2 Testsuite Organization 0 000000 cece cece ren 87 I3 Writing TestS i22 diets weeded ted erm cea dd a laws rer 88 ES os oath ese tee bone ees eae ees 88 18 4 Getting Started 0 cee enit i Ssi E E ESKE 88 18 2 Debugging GDB with itself 0 0 0 c eee eee eee 89 18 3 Submitting Patches cocci see e ees etta 90 18 4 Obsolete Conditionals lesse RR 91 Appendix A GDB Currently available observers eee ee ee ee ee ee ee ee 91 A 1 Implementation rationale 00 0 cee cece eee 91 A2 Debugging Ee RH pad wage ed ERE ERE 92 A 3 normal stop Notifications isses 92 iv Appendix B GNU Free Documentation License E E E E E E T 93 B 1 ADDENDUM How to use this License for your documents 99 Chapter 2 Overall Structure 1 Scope of this Document This document documents the internals of the GNU debugger GDB It includes description of GDB s key algorithms and operations as well as the mechanisms that adapt GDB to specific hosts and targets 1 Requirements Before diving into the internals you should understand the formal requirements and other expectations for GDB Although some of these may seem obvious there have been proposals for GDB that have run counter to these requirements First of all
63. OLIB RETURN TRAMPOLINE pc name Define this to evaluate to nonzero if the program is stopped in the trampoline that returns from a shared library IN SOLIB DYNSYM RESOLVE CODE pc Define this to evaluate to nonzero if the program is stopped in the dynamic linker SKIP SOLIB RESOLVER pc Define this to evaluate to the nonzero address at which execution should continue to get past the dynamic linker s symbol resolution function A zero value indicates that it is not important or necessary to set a breakpoint to get through the dynamic linker and that single stepping will suffice Chapter 9 Target Architecture Definition 4T INTEGER TO ADDRESS type buf Define this when the architecture needs to handle non pointer to address con versions specially Converts that value to an address according to the current architectures conventions Pragmatics When the user copies a well defined expression from their source code and passes it as a parameter to GDB s print command they should get the same value as would have been computed by the target program Any deviation from this rule can cause major confusion and annoyance and needs to be justified carefully In other words GDB doesn t really have the freedom to do these conversions in clever and useful ways It has however been pointed out that users aren t complaining about how GDB casts integers to pointers they are complaining that they can t take an address from a disass
64. PRECATED FP REGNUM ciiasotirernspii treere 43 DEPRECATED FRAME CHAIN sees 43 DEPRECATED FRAME CHAIN VALID 44 DEPRECATED FRAME INIT SAVED REGS 44 DEPRECATED FRAME SAVED PC 44 DEPRECATED FRAMELESS FUNCTION INVOCATION Pigdggaeezpeeis d ebes ne CAG Seek eee eee 43 DEPRECATED_FUNCTION_START_OFFSET 45 DEPRECATED_GET_SAVED_REGISTER 45 DEPRECATED_IBM6000_TARGET 45 DEPRECATED_INIT_EXTRA_FRAME_INFO 46 DEPRECATED_INIT_FRAME_PC 46 DEPRECATED LITTLE REMOTE BREAKPOINT 40 DEPRECATED POP FRAME eeese 49 100 DEPRECATED_PUSH_ARGUMENTS 49 DEPRECATED_REG_STRUCT_HAS_ADDR 49 50 DEPRECATED_REGISTER_RAW_SIZE 37 47 DEPRECATED_REGISTER_VIRTUAL_SIZE 37 48 DEPRECATED_REMOTE_BREAKPOINT 40 DEPRECATED SIGTRAMP END 46 DEPRECATED_SIGTRAMP_START 46 DEPRECATED_STACK_ALIGN 51 DEPRECATED_USE_STRUCT_CONVENTION 9523 deprecating commands 005 10 GESTS Mois stn tava betes RP PEE MU Pp dudit ed 71 DEV TIY wakes RR Une Ph Ee pEuHLE add das 29 DIRNAME SEPARATOR eeseeeeeeess 72 DISABLE_UNSETTABLE_BREAK 42 discard cleanups 5535 64 s8eb eee aee Hes 64 do cl anups are 64 DOS textiles noms rie pA REY e p oe need 29 DW AT address elasS coccio coccio ce rerorsi
65. Since we can t depend upon everyone having Bison and YACC produces parsers that define a bunch of global names the following lines must be included at the top of the YACC parser to prevent the various parsers from defining the same global names define yyparse lang parse define yylex lang lex define yyerror lang error define yylval lang lval define yychar lang char define yydebug lang debug define yypact lang_pact define yyri lang ri define yyr2 lang r2 define yydef lang def define yychk lang _chk define yypgo lang _pgo define yyact lang_act define yyexca lang_exca define yyerrflag lang_errflag define yynerrs lang_nerrs At the bottom of your parser define a struct language_defn and initialize it with the right values for your language Define an initialize_lang routine and have it call add_language lang_language_defn to tell the rest of GDB that your language exists You l need some other supporting variables and functions which will be used via pointers from your lang_language_defn See the declaration of struct language defn in language h and the other exp y files for more information Add amy evaluation routines if necessary If you need new opcodes that represent the operations of the language add them to the enumerated type in expression h Add support code for these operations in the evaluate subexp function defined in the file eval c Add cases for new opcodes in two fun
66. Wtrigraphs Wformat Wformat nonliteral Since GDB uses the format printf attribute on all printf like functions these check not just printf calls but also calls to functions such as fprintf_unfiltered Wparentheses This warning includes uses of the assignment operator within an if statement Wpointer arith Wuninitialized Wunused label This warning has the additional benefit of detecting the absence of the case reserved word in a switch statement enum FD_SCHEDULED NOTHING_SCHEDULED sched switch sched 1 case FD SCHEDULED break NOTHING SCHEDULED break F Wunused function Pragmatics Due to the way that GDB is implemented most functions have unused pa rameters Consequently the warning Wunused parameter is precluded from the list The Chapter 13 Coding 69 macro ATTRIBUTE UNUSED is not used as it leads to false negatives it is not an error to have ATTRIBUTE UNUSED on a parameter that is being used The options Wall and Wunused are also precluded because they both include Wunused parameter Pragmatics GDB has not simply accepted the warnings enabled by Wall Werror W Instead it is selecting warnings when and where their benefits can be demonstrated 13 4 4 Formatting The standard GNU recommendations for formatting must be followed strictly A function declaration should not have its name in column zero A function de
67. a aoe ae 13 ui out message pr RE REUS 15 ui out Spaces Ressdzebh E aa i ae ees 15 ui out stream delete sess 14 ui out table begin s sese 12 ur out table body ER RRERRERaRA 12 ui out table end eee 12 ui out table header sees 12 i out text oco ERG PER Cad 15 ui out t ple begin ssiexe e e Rr ERES 12 ui out tuple end Ree ace bles 12 ui out wrap hint s aig od qe erodes 15 i Stream 1 26g ue wud psp ERR P dees 14 UINT MAX e anaiena aa on onn Bis Gut aaa sd recen 29 Appendix B Index ULONG MAX o drek caae4 seis dS SEER AS ORE CR ee RA 29 unwind Gummy id 2e rriki seinh 53 UNWIN PE 2 ss Sceive Sad seks aa Eee Rd fepe 44 Und Sp ereer ae ere ee aliene 44 USE PROG FS zerei PTPEXQ4gmq e o eEE e TY oe eee kee 61 UD eodd iu e OR a aS eo deu eee ee 30 using ui out functlons 2 1 ea Baa hoes 15 V value as address eens 34 value from pointer sees sess 34 VALUE TU REGISTER 2s 0 44 secu ei eesescedes 38 53 VARIABLES INSIDE BLOCK cellier 54 vendor branches lslllllll esee 75 virtual register representation 36 104 VOD PEE alsese Gand uate Roda rop RUP ton ECKEN amp 92 volatiles sceri adrener eisi ub Cr Sale nate ad 30 watchpoints ced hune PERS peeEP EP TE AY 4 watchpoints on x80 2isbneiele b bp metre 6 word addressed machines sus 33 Wrap here
68. ad but any necessary low level processing for filename is still done SOLIB CREATE INFERIOR HOOK Define this to expand into any shared library relocation code that you want to be run just after the child process has been forked START INFERIOR TRAPS EXPECTED When starting an inferior GDB normally expects to trap twice once when the shell execs and once when the program itself execs If the actual number of traps is something other than 2 then define this macro to expand into the number expected USE PROC FS This determines whether small routines in tdep c which translate register values between GDB s internal representation and the proc representation are compiled U REGS OFFSET This is the offset of the registers in the upage It need only be defined if the generic ptrace register access routines in infptrace c are being used that is infptrace c is configured in and FETCH INFERIOR REGISTERS is not defined If the default value from infptrace c is good enough leave it undefined Chapter 12 Support Libraries 62 The default value means that u u_ar0 points to the location of the registers l m guessing that define U REGS OFFSET O means that u u arO0 is the location of the registers CLEAR SOLIB See objfiles c DEBUG_PTRACE Define this to debug ptrace calls 12 Support Libraries 12 1 BFD BFD provides support for GDB in several ways identifying executable and core files
69. ad p6ucle oh peste ed ak ala beer ali ad Gane eis oboe ands 53 t ad Spu co ga ea ode Rena ur Se RD o dg 53 reading of symbols serors reniir nri ERa 20 red ZONE rnn aga Ea E E D tae 43 register data formats converting 37 register pTOUPS ieres se ues nesses ue Gd ERE Re AT register representation 00 000 eee 3T REGISTER_CONVERT_TO_RAW 37 48 REGISTER CONVERT TO TYPE 38 REGISTER CONVERT TO VIRTUAL 37 48 REGISTER CONVERTIBLE es 37 47 BREGISTER NAMB mms on deer bI RE dons D ERE is 50 register reggroup p e ise erre des 47 REGISTER TO VALUE 52 cR RR mme 38 AT register typ8c conseerestessekebe re ER 48 REGISTER U_ADDR eeLeenesweereeeeme RS 61 REGISTER VIRTUAL TYPE ES 48 regset from core section 48 regular expressions library 63 Release Branches 000 eevee 75 remote debugging support 0 28 REM TE BPT VECTOR 3 ihe Eee Red 54 representations raw and virtual registers 36 representations register and memory 3T requirements for GDB lesse sees 1 running the test suite llle esee 86 S SAVE DUMMY FRAME T08 sees 50 SCANF HAS LONG DOUBLE 30 SDB REG TO REGNUM i inkl Rer LU 50 secondary symbol file 21 SEEK CUR 34 2a PR xti des ditus 30 SEEK PET LI nes ea ee 30 separat
70. agent 3 frame pointer register 005 3 frame align ccce o m P idasi TRE 43 Appendix B Index FRAME EP denheRGucdGeac epe RRRuR E C 2 FRAME NUM ARGS ssc cceGe3 cress ered eases 44 frame POP sirit ienni epep dairi E RE pn 49 full symbol table 52 ponds ae tm Rs 22 function prototypes ee enra annn p eee 70 function sase boii ci ieee rbuses be etd edens 70 FUNCTION_EPILOGUE_SIZE 52 9 s 44 fundamental types 000 23 G GCC COMPILED FLAG SYMBUL 45 GCC2 COMPILED FLAG SYMBOL 45 GDB MULTI ARCH i uuu r9 ng re ure rada 45 gdb 08abD3 c ar eee RSS BP Ae Mpeg 32 GDB_OSABI_ARM_APCS 0000 32 GDB_OSABI_ARM_EABI_V1 32 GDB_OSABI_ARM_EABI_V2 32 GDB_OSABI_FREEBSD_AOUT 31 GDB_OSABI_FREEBSD_ELF 31 GDB OSABLE GUS2 wr pe LER EXER era 32 GDB OSABI HURD kk REG mc RER GRE sas 31 GDB OSABE LINUX 22m vL EDDY RR 31 GDB_OSABI_NETBSD_AOUT 31 GDB OSABI NETBSD ELE ene wer Rex 31 GDB OSABI NETWARE lesser 32 GDB OSABI SPB1 22 20D RP ERIS 31 GDB_OSABI SOLARIS dee ue dere iida hs 31 GDB OSABLE SVR csore see dis bes aay ER RAS Era 31 GDB_OSABI_UNKNOWN 004 31 GDB OSABEI WINGE 7 2v at cherie ated 32 GDB TARGET IS HPP 222 2 2 sung r 45 gdbarch datace ks saith teehee eee 65 gdbarc
71. alues to the inferior via 1386 DR_LOW_RESET_ADDR and I1386_DR_LOW_SET_CONTROL If a register is shared by several watchpoints each time a i386_remove_watchpoint is called it decre ments the reference count and only calls I386_DR_LOW_RESET_ADDR and I386_ DR_LOW_SET_CONTROL when the count goes to zero i386_insert_hw_breakpoint addr shadow i386_remove_hw_breakpoint addr shadow These functions insert and remove hardware assisted breakpoints The macros target_insert_hw_breakpoint and target_remove_hw_breakpoint are set to call these functions These functions work like i386_insert_watchpoint and i386_remove_watchpoint respectively except that they set up the debug registers to watch instruction execution and each hardware assisted breakpoint always requires exactly one debug register i386_stopped_by_hwbp void This function returns non zero if the inferior has some watchpoint or hardware breakpoint that triggered It works like 1386 stopped data address except that it doesn t record the address whose watchpoint triggered 1386 cleanup dregs void This function clears all the reference counts addresses and control bits in the mirror images of the debug registers It doesn t affect the actual debug registers in the inferior process Chapter 4 User Interface 9 Notes 1 x86 processors support setting watchpoints on I O reads or writes However since no target supports this as of March 2001 and since enum target hw bp
72. ams do not need to be in a consistent style Since GDB is used to debug programs written in many different styles it s worth having a mix of styles in the testsuite for instance some GDB bugs involving the display of source lines would never manifest themselves if the programs used GNU coding style uniformly 18 Hints Check the README file it often has useful information that does not appear anywhere else in the directory 18 1 Getting Started GDB is a large and complicated program and if you first starting to work on it it can be hard to know where to start Fortunately if you know how to go about it there are ways to figure out what is going on This manual the GDB Internals manual has information which applies generally to many parts of GDB Information about particular functions or data structures are located in comments with those functions or data structures If you run across a function or a global variable which does not have a comment correctly explaining what is does this can be thought of as a bug in GDB feel free to submit a bug report with a suggested comment if you can figure out what the comment should say If you find a comment which is actually wrong be especially sure to report that Comments explaining the function of macros defined in host target or native dependent files can be in several places Sometimes they are repeated every place the macro is defined Chapter 18 Hints 89 Sometimes they
73. an item describing the Modified Version as stated in the previous sentence 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 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 years before the Document itself or if the original publisher of the version it refers to gives permission For any section Entitled Acknowledgements or Dedications Preserve the Title of the section and preserve in the section all the substance and tone of each of the contributor acknowledgements and or dedications given therein 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 Delete any section Entitled Endorsements Such a section may not be included in the Modified Version Do not retitle any existing section to be Entitled Endorsements or to conflict in title with any Invariant Section Preserve any Warranty Disclaimers If the Modified Version includes new front matter sections or appendices that qualify as Secondary Sections and contain no material copied from the Document you may at Appendix B GNU Free Documentation License 97 your option designate some or all of these se
74. and after the N_SO stab and guess the starting and ending addresses of the compilation unit from them PC LOAD SEGMENT If defined print information about the load segment for the program counter Defined only for the RS 6000 PC REGNUM If the program counter is kept in a register then define this macro to be the number greater than or equal to zero of that register This should only need to be defined if TARGET READ PC and TARGET WRITE PC are not defined PARM BOUNDARY If non zero round arguments to a boundary of this many bits before pushing them on the stack stabs argument has addr gdbarch type Define this to return nonzero if a function argument of type type is passed by reference instead of value This method replaces DEPRECATED REG STRUCT HAS ADDR see DEPRE CATED_REG_STRUCT_HAS_ADDR page 50 PROCESS_LINENUMBER_HOOK A hook defined for XCOFF reading PROLOGUE_FIRSTLINE_OVERLAP Only used in unsupported Convex configuration PS_REGNUM If defined this is the number of the processor status register This definition is only used in generic code when parsing ps DEPRECATED_POP_FRAME If defined used by frame_pop to remove a stack frame This method has been superseeded by generic code push_dummy_call gdbarch function regcache pc_addr nargs args sp struct return struct addr Define this to push the dummy frame s call to the inferior function onto the stack In addition to pushing
75. arch_nozel struct gdbarch gdbarch int total 1 struct nozel data gdbarch data gdbarch nozel handle data gt total nozel A module can on demand create architecture dependant data structures using post_ init In the below the nozel s total is computed on demand by nozel_post_init using in formation obtained from the architecture static void nozel_post_init struct gdbarch gdbarch struct nozel data GDBARCH_OBSTACK_ZALLOC gdbarch struct nozel nozel gt total gdbarch gdbarch return data extern int nozel_total struct gdbarch gdbarch 1 struct nozel data gdbarch data gdbarch nozel handle return data gt total Chapter 13 Coding 67 13 3 Wrapping Output Lines Output that goes through printf_filtered or fputs_filtered or fputs_demangled needs only to have calls to wrap_here added in places that would be good breaking points The utility routines will take care of actually wrapping if the line width is exceeded The argument to wrap_here is an indentation string which is printed only if the line breaks there This argument is saved away and used later It must remain valid until the next call to wrap here or until a newline has been printed through the filtered functions Don t pass in a local variable and then return It is usually best to call wrap here after printing a comma or space If you call it before printing a space make sure that your indentation properly a
76. are watchpoints e The value of the expression to be watched depends on data held in registers as opposed to memory e Too many different watchpoints requested On some architectures this situation is impossible to detect until the debugged program is resumed Note that x86 debug Chapter 3 Algorithms 5 registers are used both for hardware breakpoints and for watchpoints so setting too many hardware breakpoints might cause watchpoint insertion to fail e No hardware assisted watchpoints provided by the target implementation Software watchpoints are very slow since GDB needs to single step the program being debugged and test the value of the watched expression s after each instruction The rest of this section is mostly irrelevant for software watchpoints When the inferior stops GDB tries to establish among other possible reasons whether it stopped due to a watchpoint being hit For a data write watchpoint it does so by evaluating for each watchpoint the expression whose value is being watched and testing whether the watched value has changed For data read and data access watchpoints GDB needs the target to supply a primitive that returns the address of the data that was accessed or read see the description of target stopped data address below if this primitive returns a valid address GDB infers that a watchpoint triggered if it watches an expression whose evaluation uses that address GDB uses several macros and primiti
77. are where the macro is used Sometimes there is a header file which supplies a default definition of the macro and the comment is there This manual also documents all the available macros Start with the header files Once you have some idea of how GDB s internal symbol tables are stored see symtab h gdbtypes h you will find it much easier to understand the code which uses and creates those symbol tables You may wish to process the information you are getting somehow to enhance your understanding of it Summarize it translate it to another language add some perhaps trivial or non useful feature to GDB use the code to predict what a test case would do and write the test case and verify your prediction etc If you are reading code and your eyes are starting to glaze over this is a sign you need to use a more active approach Once you have a part of GDB to start with you can find more specifically the part you are looking for by stepping through each function with the next command Do not use step or you will quickly get distracted when the function you are stepping through calls another function try only to get a big picture understanding perhaps using the comment at the beginning of the function being called of what it does This way you can identify which of the functions being called by the function you are stepping through is the one which you are interested in You may need to examine the data structures generated at ea
78. as support for figuring out that the target is doing a longjmp and for stopping at the target of the jump if we are stepping This is done with a few specialized internal breakpoints which are visible in the output of the maint info breakpoint command To make this work you need to define a macro called GET_LONGJMP_TARGET which will examine the jmp_buf structure and extract the longjmp target address Since jmp_buf is target specific you will need to define it in the appropriate tm target h file Look in tm sun4os4 h and sparc tdep c for examples of how to do this 3 8 Watchpoints Watchpoints are a special kind of breakpoints see Chapter 3 Algorithms page 2 which break when data is accessed rather than when some instruction is executed When you have data which changes without your knowing what code does that watchpoints are the silver bullet to hunt down and kill such bugs Watchpoints can be either hardware assisted or not the latter type is known as software watchpoints GDB always uses hardware assisted watchpoints if they are available and falls back on software watchpoints otherwise Typical situations where GDB will use software watchpoints are e The watched memory region is too large for the underlying hardware watchpoint sup port For example each x86 debug register can watch up to 4 bytes of memory so trying to watch data structures whose size is more than 16 bytes will cause GDB to use softw
79. atches directly to the GDB maintainers 18 4 Obsolete Conditionals Fragments of old code in GDB sometimes reference or set the following configuration macros They should not be used by new code and old uses should be removed as those parts of the debugger are otherwise touched STACK END ADDR This macro used to define where the end of the stack appeared for use in interpreting core file formats that don t record this address in the core file itself This information is now configured in BFD and GDB gets the info portably from there The values in GDB s configuration files should be moved into BFD configuration files if needed there and deleted from all of GDB s config files Any foo xdep c file that references STACK END ADDR is so old that it has never been converted to use BFD Now that s old Appendix A GDB Currently available observers A 1 Implementation rationale An observer is an entity which is interested in being notified when GDB reaches certain states or certain events occur in GDB The entity being observed is called the subject To receive notifications the observer attaches a callback to the subject One subject can have several observers observer c implements an internal generic low level event notification mechanism This generic event notification mechanism is then re used to implement the exported high level notification management routines for all possible notifications The current implementa
80. atchlevel of 50 At the time each new release branch is created the mainline s major and minor version numbers are updated GDb s release branch is similar When the branch is cut the patchlevel is changed from 50 to 90 As draft releases are drawn from the branch the patchlevel is incremented Once the first release major minor has been made the patchlevel is set to 0 and updates have an incremented patchlevel For snapshots and Cvs check outs it is also possible to identify the Cvs origin major minor 50 YYYY MMDD drawn from the HEAD of mainline CVS e g 6 1 50 20020302 major minor 90 YY YY MM DD major minor 91 YYYY MMDD drawn from a release branch prior to the release e g 6 1 90 20020304 major minor 0 Y Y Y Y MMDD major minor 1 YYYY MMDD drawn from a release branch after the release e g 6 2 0 20020308 Chapter 15 Versions and Branches 75 If the previous GDB version is 6 1 and the current version is 6 2 then substituting 6 for major and 1 or 2 for minor here s an illustration of a typical sequence lt HEAD gt 6 1 50 20020302 cvs lt gdb_6_2 branch gt 6 2 50 20020303 cvs 6 1 90 draft 1 T 6 1 91 NR 2 ee T EEN ETE ee 6 2 uud M Mn T EN 6 2 1 UE OCT mud eid 6 2 50 20020311 cvs lt gdb_6_3 branch gt 6 3 50 20020312 cvs 6 2 90 draft 1 15 2 Release Branches GDB draws a release series 6 2 6 2 1 from a
81. b will be read in find pc function find pc line and other find pc functions handle this e Dy its name e g the user asks to print a variable or set a breakpoint on a function Global names and file scope names will be found in the psymtab which will cause the symtab to be pulled in Local names will have to be qualified by a global name or a file scope name in which case we will have already read in the symtab as we evaluated the qualifier Or a local symbol can be referenced when we are in a local scope in which case the first case applies lookup symbol does most of the work here The only reason that psymtabs exist is to cause a symtab to be read in at the right moment Any symbol that can be elided from a psymtab while still causing that to happen should not appear in it Since psymtabs don t have the idea of scope you can t put local symbols in them anyway Psymtabs don t have the idea of the type of a symbol either so types need not appear unless they will be referenced by name It is a bug for GDB to behave one way when only a psymtab has been read and another way if the corresponding symtab has been read in Such bugs are typically caused by a psymtab that does not contain all the visible symbols or which has the wrong instruction address ranges Chapter 6 Symbol Handling 23 The psymtab for a particular section of a symbol file objfile could be thrown away after the symtab has been read in The symtab s
82. bol format the length of the prefix and pointers to four functions These functions are called at various times to process symbol files whose identification matches the specified prefix The functions supplied by each module are Xyz symfile init struct sym fns sf Called from symbol file add when we are about to read a new symbol file This function should clean up any internal state possibly resulting from half read previous files for example and prepare to read a new symbol file Note that the symbol file which we are reading might be a new main symbol file or might be a secondary symbol file whose symbols are being added to the existing symbol table The argument to xyz symfile init is a newly allocated struct sym fns whose bfd field contains the BFD for the new symbol file being read Its private field has been zeroed and can be modified as desired Typically a struct of private information will be malloc d and a pointer to it will be placed in the private field There is no result from xyz symfile init but it can call error if it detects an unavoidable problem xyz new init O Called from symbol file add when discarding existing symbols This function needs only handle the symbol reading module s internal state the symbol table data structures visible to the rest of GDB will be discarded by symbol file add It has no arguments and no result It may be called after xyz symfile init if a new symbol table is being
83. call to u out table begin otherwise the ui out functions will signal an internal error The output of the tuples that represent the table rows must follow the call to ui out table body and precede the call to ui out table end You build a tuple by calling ui_ out tuple begin and ui out tuple end with suitable calls to functions which actually output fields between them void ui out tuple begin struct ui out uiout const char id Function This function marks the beginning of a tuple output id points to an optional string that identifies the tuple it is copied by the implementation and so strings in malloced storage can be freed after the call void ui out tuple end struct ui out uiout Function This function signals an end of a tuple output There should be exactly one call to ui out tuple end for each call to ui out tuple begin otherwise an internal GDB error will be signaled Chapter 4 User Interface 13 struct cleanup make cleanup ui out tuple begin end struct ui_out Function uiout const char id This function first opens the tuple and then establishes a cleanup see Chapter 13 Coding page 64 to close the tuple It provides a convenient and correct implemen tation of the non portable code sequence struct cleanup old cleanup ui out tuple begin uiout old cleanup make cleanup void void ui out tuple end uiout void ui out list begin struct ui out uiout co
84. ccounts for the leading space that will print if the line wraps there Any function or set of functions that produce filtered output must finish by printing a newline to flush the wrap buffer before switching to unfiltered printf output Symbol reading routines that print warnings are a good example 13 4 GDB Coding Standards GDB follows the GNU coding standards as described in etc standards texi This file is also available for anonymous FTP from GNU archive sites GDB takes a strict interpretation of the standard in general when the GNU standard recommends a practice but does not require it GDB requires it GDB follows an additional set of coding standards specific to GDB as described in the following sections 13 4 1 ISO C GDB assumes an ISO IEC 9899 1990 a k a ISO C90 compliant compiler GDB does not assume an ISO C or POSIX compliant C library 13 4 2 Memory Management GDB does not use the functions malloc realloc calloc free and asprintf GDB uses the functions xmalloc xrealloc and xcalloc when allocating memory Unlike malloc et al these functions do not return when the memory pool is empty Instead they unwind the stack using cleanups These functions return NULL when requested to allocate a chunk of memory of size zero Pragmatics By using these functions the need to check every memory allocation is removed These functions provide portable behavior GDB does not use the function free GDB uses the fun
85. ch or jump SKIP_PROLOGUE pc A C expression that returns the address of the real code beyond the function entry prologue found at pc SKIP_TRAMPOLINE_CODE pc If the target machine has trampoline code that sits between callers and the functions being called then define this macro to return a new PC that is at the start of the real function SP_REGNUM If the stack pointer is kept in a register then define this macro to be the number greater than or equal to zero of that register or 1 if there is no such register STAB_REG_TO_REGNUM Define this to convert stab register numbers as gotten from r declarations into GDB regnums If not defined no conversion will be done DEPRECATED_STACK_ALIGN addr Define this to increase addr so that it meets the alignment requirements for the processor s stack Unlike frame_align page 43 this function always adjusts addr upwards By default no stack alignment is performed STEP_SKIPS_DELAY addr Define this to return true if the address is of an instruction with a delay slot If a breakpoint has been placed in the instruction s delay slot GDB will single step Chapter 9 Target Architecture Definition 52 over that instruction before resuming normally Currently only defined for the Mips STORE RETURN VALUE type regcache valbuf A C expression that writes the function return value found in valbuf into the regcache type is the type of the value that is to be retu
86. ch stage with reference to the comments in the header files explaining what the data structures are supposed to look like Of course this same technique can be used if you are just reading the code rather than actually stepping through it The same general principle applies when the code you are looking at calls something else just try to understand generally what the code being called does rather than worrying about all its details A good place to start when tracking down some particular area is with a command which invokes that feature Suppose you want to know how single stepping works As a GDB user you know that the step command invokes single stepping The command is invoked via command tables see command h by convention the function which actually performs the command is formed by taking the name of the command and adding _command or in the case of an info subcommand info For example the step command invokes the step command function and the info display command invokes display info When this convention is not followed you might have to use grep or M x tags search in emacs or run GDB on itself and set a breakpoint in execute command If all of the above fail it may be appropriate to ask for information on bug gdb But never post a generic question like I was wondering if anyone could give me some tips about understanding GDB if we had some magic secret we would put it in this manual Suggestions for
87. chitecture Definition 36 else return NULL int somearch_address_class_name_to_type_flags char name int type_flags_ptr 1 if strcmp name short 0 type flags ptr TYPE FLAG ADDRESS CLASS 1 return 1 else return 0 The qualifier short is used in GDB s type expressions to indicate the presence of one of these short pointers E g if the debug information indicates that short_ptr_var is one of these short pointers GDB might show the following behavior gdb ptype short_ptr_var type int short 9 5 Raw and Virtual Register Representations Maintainer note This section is pretty much obsolete The functionality described here has largely been replaced by pseudo registers and the mechanisms described in Chapter 9 Using Different Register and Memory Data Representations page 31 See also Bug Tracking Database and ARI Index for more up to date information Some architectures use one representation for a value when it lives in a register but use a different representation when it lives in memory In GDB s terminology the raw representation is the one used in the target registers and the virtual representation is the one used in memory and within GDB struct value objects Maintainer note Notice that the same mechanism is being used to both convert a register to a struct value and alternative register forms For almost all data types on almost all architectures the virtual and raw representations
88. ction xfree to return memory to the memory pool Consistent with ISO C this function ignores a request to free a NULL pointer Pragmatics On some systems free fails when passed a NULL pointer GDB can use the non portable function alloca for the allocation of small temporary values such as strings Pragmatics This function is very non portable Some systems restrict the memory being allocated to no more than a few kilobytes Chapter 13 Coding 68 GDB uses the string function xstrdup and the print function xstrprintf Pragmatics asprintf and strdup cam fail Print functions such as sprintf are very prone to buffer overflow errors 13 4 3 Compiler Warnings With few exceptions developers should include the configuration option enable gdb build warnings Werror when building GDB The exceptions are listed in the file gdb MAINTAINERS This option causes GDB when built using GCC to be compiled with a carefully selected list of compiler warning flags Any warnings from those flags being treated as errors The current list of warning flags includes Wimplicit Since GDB coding standard requires all functions to be declared using a pro totype the flag has the side effect of ensuring that prototyped functions are always visible with out resorting to Wstrict prototypes Wreturn type Such code often appears to work except on instruction set architectures that use register windows Wcomment
89. ctions as invariant To do this add their titles to the list of Invariant Sections in the Modified Version s license notice These titles 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 the text has been approved by an organization as the authoritative definition of a standard You may add a passage of up to five words 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 Front Cover Text and one of Back Cover Text may be added by or through arrangements made by any one entity If the Document already includes 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 replace the old one on explicit permission from the previous publisher that added the old one The author 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 under this License under the terms defined in section 4 above for modified versions provided that you include in the combination al
90. ctions from parse c prefixify_subexp and length of subexp These compute the number of exp elements that a given operation takes up Chapter 8 Host Definition 27 Update some existing code Add an enumerated identifier for your language to the enumerated type enum language in defs h Update the routines in language c so your language is included These rou tines include type predicates and such which in some cases are language dependent If your language does not appear in the switch statement an error is reported Also included in language c is the code that updates the variable current_ language and the routines that translate the language lang enumerated iden tifier into a printable string Update the function initialize language to include your language This function picks the default language upon startup so is dependent upon which languages that GDB is built for Update allocate symtab in symfile c and or symbol reading code so that the language of each symtab source file is set properly This is used to deter mine the language to use at each stack frame level Currently the language is set based upon the extension of the source file If the language can be better inferred from the symbol information please set the language of the symtab in the symbol reading code Add helper code to print subexp in expprint c to handle any new ex pression opcodes you have added to expression
91. d cases often indicate some minor catastrophe such as the compiler being unable to deal with a test program Chapter 17 Testsuite 87 When making any significant change to GDB you should run the testsuite before and after the change to confirm that there are no regressions Note that truly complete testing would require that you run the testsuite with all supported configurations and a variety of compilers however this is more than really necessary In many cases testing with a single configuration is sufficient Other useful options are to test one big endian Sparc and one little endian x86 host a cross config with a builtin simulator powerpc eabi mips elf or a 64 bit host Alpha If you add new functionality to GDB please consider adding tests for it as well this way future GDB hackers can detect and fix their changes that break the functionality you added Similarly if you fix a bug that was not previously reported as a test failure please add a test case for it Some cases are extremely difficult to test such as code that handles host OS failures or bugs in particular versions of compilers and it s OK not to try to write tests for all of those DejaGNU supports separate build host and target machines However some GDB test scripts do not work if the build machine and the host machine are not the same In such an environment these scripts will give a result of UNRESOLVED like this UNRESOLVED gdb base example e
92. ddresses These have default definitions appropriate for architectures on which all pointers are simple unsigned byte addresses CORE ADDR POINTER TO ADDRESS struct type type char buf Target Macro Assume that buf holds a pointer of type type in the appropriate format for the current architecture Return the byte address the pointer refers to This function may safely assume that type is either a pointer or a C reference type Chapter 9 Target Architecture Definition 35 void ADDRESS TO POINTER struct type type char buf Target Macro CORE ADDR addr Store in buf a pointer of type type representing the address addr in the appropriate format for the current architecture This function may safely assume that type is either a pointer or a C reference type 9 4 Address Classes Sometimes information about different kinds of addresses is available via the debug infor mation For example some programming environments define addresses of several different sizes If the debug information distinguishes these kinds of address classes through either the size info e g DW AT byte size in DWARF 2 or through an explicit address class at tribute e g DW AT address class in DWARF 2 the following macros should be defined in order to disambiguate these types within GDB as well as provide the added information to a GDB user when printing type expressions int ADDRESS CLASS TYPE FLAGS int byte size int Target Macro dwar
93. debugged executes In most cases they are the same machine in which case a third type of Native attributes come into play Defines and include files needed to build on the host are host support Examples are tty support system defined types host byte order host float format Defines and information needed to handle the target format are target dependent Ex amples are the stack frame format instruction set breakpoint instruction registers and how to set up and tear down the stack to call a function Information that is only needed when the host and target are the same is native depen dent One example is Unix child process support if the host and target are not the same doing a fork to start the target process is a bad idea The various macros needed for finding the registers in the upage running ptrace and such are all in the native dependent files Another example of native dependent code is support for features that are really part of the target environment but which require include files that are only available on the host system Core file handling and setjmp handling are two common cases When you want to make GDB work native on a particular machine you have to include all three kinds of information 3 Algorithms GDB uses a number of debugging specific algorithms They are often not very complicated but get lost in the thicket of special cases and real world issues This chapter describes the basic algorithms and mentions
94. dressprint 1 if nr printable breakpoints gt 0 annotate field 4 if TARGET ADDR BIT 32 ui out table header uiout 10 ui left addr Address 5 else ui out table header uiout 18 ui left addr Address 5 if nr_printable_breakpoints gt 0 annotate_field 5 ui_out_table_header uiout 40 ui_noalign what What 6 ui_out_table_body uiout if nr_printable_breakpoints gt 0 Chapter 4 User Interface 17 annotate breakpoints table O This example from the print one breakpoint function shows how to produce the actual data for the table whose structure was defined in the above example The original code was annotate record annotate field 0 printf filtered 3d b number annotate field 1 if int b gt type gt sizeof bptypes sizeof bptypes 0 Cint b gt type bptypes int b gt type type internal error bptypes table does not describe type d int b gt type printf filtered 14s bptypes int b gt type description annotate_field 2 printf filtered 4s bpdisps int b disposition annotate field 3 printf filtered 3c bpenables int b gt enable This is the new version annotate record ui out tuple begin uiout bkpt annotate field 0 ui out field int uiout number b gt number annotate field 1 if int b gt type gt sizeof bptypes sizeof bptypes 0 Cint b
95. e data and code address spaces 33 serial line supportcs cene deed te cone ae 28 SHELL_COMMAND_CONCAT 00 61 SHELE EILE 2c ebbe sr pb neice ang ees 61 Appendix B Index SIGWINCH HANDLER n n b Rs SIGWINCH HANDLER BODY SKIP PERMANENT BREAKPOINT SKIP PROLOGUE 2 546 ERU ra Rab ee E SKIP S OLIB RESOLVER ssec du e Pes SKIP TRAMPOLINE CODE 2 n mmo SLASH STRING 24i ker RR dieters Gigi dunt ata alana software breakpoints 00 000 eee cence software watchpoints e eee asis S FTWARE SINGLE STEP 2ssso ser nn SOFTWARE SINGLE STEP P 52 52 5 9 n S FUN ADDRESS MAYBE MISSING S LIB ADD ostenie dE eR RR TEES SOLIB CREATE INFERIOR HOOK solib dJoaded seoed ranei Gen ie anh eal b duras SOLD unloaded 2 22 helene teeta an Dans SOM debugging info NOM format Ls i sienta etui nis cance QU E Us source code formatting 000 SP REGNUM 2 2 zii RR Eger RR REG ERE spaces separate data and code address SIAB REG TO REGNUM 2 n rn arm mn stabs debugging info 000005 stabs_argument_has_addr stack aligument 2o vence bee da ae START INFERIOR TRAPS EXPECTED STEP SKIPS DELAY 2 22 93 m Rn STOP SIGNAL 9 Tna 4 REDE SIOPPED BY WATCHPOLNT ta ews nen STORE RETURN VALUE 22e ng mean
96. e eee eee essel 59 11 2 Uifabees i sene bd bee Cem Hs Bad a eh ee tae ee 59 TES 1G swe eda ETT 60 WA WINS ze Re RE Lepus pe a eee pee RR REG pCHEDR ane 60 11 5 shared JiDraries oso i oT T Reb d uS inde fant 60 11 6 Native Conditionals 0 000 cece eee eee eee 60 12 Support Libraries 00060 62 IPXMMIDDRP C bee Dake dad od a euskal oe 62 12 2 0DCOde8 c oneb rb PURO odd deo ebd Rabe dua 62 12 3 Xeadline 5 ccs sean Rt dent Redon ca ale ete cR Un 62 2A mmal e aea dede er aaah a eee bs Ac t 62 12 5 bIDerty a eet tne ect Dre oni Detox tc vn dta 63 12 5 obstacks in GDB sepius ae aipear iaa ae a Baa 63 120 PMT Ker ra bep p oa Vr pes t bee 63 12 7 ANGI oss otio ee tutae estet astute one eee eu E 64 13 COGiING usur se Ria Aa OR AUREUP EXE Rd de 64 13 1 Cleanups ue nter RbRECOpCREDR IRR EY ERU EE 64 13 2 Per architecture module data liiis lessen 65 13 38 Wrapping Output LinNeSi ess asa ssa pandas aaraa esee 67 13 4 GDB Coding Standards nnaasesssnrasesesrrsnesssnna 67 lA ISO 2214s batten dg re ad Eod Beh EU a E 67 13 4 2 Memory Management s sese 67 13 4 8 Compiler Warnings sssseesseees mia dina 68 13 4 4 Formatting i sse RR RPIREPER SG ch ERR HAGO LEG 69 134 5 COMMENTS 2252 hee dae 1g aed aded nd 69 13216 XUSBBe cec ed tr e ete Re d RR EUR eR ORG 70 13 4 7 Function Prototypes 0 0 eee eee eee ee 70 13 4 8 Internal Error Recovery
97. e err REP ees 62 OS ABI varl nt8 i esee eb mop ol OS9K_VARIABLES_INSIDE_BLOCK 54 P PARM BOUNDARY 2 2222 rese urhe 49 parse exp 1 ssec tp Rp CREE End 27 partial symbol table 3 502022 rre 22 PC LOAD SEGMENT sos omm r3 Re 49 PC REGNUM chistes de iere OP Red aes 49 PE COFF forniat es pascio exe mere 24 per architecture module data 65 pointer representation lesse esee 33 POINTER T ADDRESS 2639 09D RR s 34 47 portability ios 2ixenkRRRASRSRE MEAE RPRRU RP TUS 72 portable file name handling 72 porting to new machines 73 prefixify subeXp oi 2d c e ears 26 PRINT FLOAT INFO 22 nM DER Rei 42 print registers infO zie s mex 42 102 print subexp i RR Rb eR E YGG 27 PRINT VECTOR INFO he cos cee ne Rma 42 PRINTF_HAS_LONG_DOUBLE m 30 PRINTF_HAS_LONG_LONG 00 4 30 PROG NAME FMT 45 ehem inb de ESI PPIRSGu 61 PROCESS LINENUMBER HOOK ssessse 49 program COUMTE sosio eere Geek dae tee 3 PROLOGUE FIRSTLINE OVERLAP 49 prompl ivre err Cv PU PR CPC PE MERE 29 PS REGNUM acidi trieercibetuuesimervxseeddeedne 49 PSV Mba ox sec i tented Redeem Rage uere 22 PTRACE ARGS TYPE i4 unseren ARR ei eE 61 push dumny call sci i eid teehee epe er Pes 49 push dummy Code 4 9 RE RS EXE RELY EUN 50 R raw register representation 36 T ad pi sce uiae a opo y ry a gr Sr or Ep qe 53 Te
98. eader files will be available on the host machine Target code must bring along its own Chapter 13 Coding 72 header files written from scratch or explicitly donated by their owner to avoid copyright problems Insertion of new ifdef s will be frowned upon It s much better to write the code portably than to conditionalize it for various systems New ifdef s which test for specific compilers or manufacturers or operating systems are unacceptable All ifdef s should test for features The information about which configu rations contain which features should be segregated into the configuration files Experience has proven far too often that a feature unique to one particular system often creeps into other systems and that a conditional based on some predefined macro for your current sys tem will become worthless over time as new versions of your system come out that behave differently with regard to this feature Adding code that handles specific architectures operating systems target interfaces or hosts is not acceptable in generic code One particularly notorious area where system dependencies tend to creep in is handling of file names The mainline GDB code assumes Posix semantics of file names absolute file names begin with a forward slash slashes are used to separate leading directories case sensitive file names These assumptions are not necessarily true on non Posix systems such as MS Windows To avoid syste
99. eanup close file file blah blah discard cleanups old return file Some functions e g fputs filtered or error specify that they should not be called when cleanups are not in place This means that any actions you need to reverse in the case of an error or interruption must be on the cleanup chain before you call these functions since they might never return to your code they longjmp instead 13 2 Per architecture module data The multi arch framework includes a mechanism for adding module specific per architecture data pointers to the struct gdbarch architecture object A module registers one or more per architecture data pointers using struct gdbarch data edbarch data register pre init Function gdbarch data pre init ftype pre init pre_init is used to on demand allocate an initial value for a per architecture data pointer using the architecture s obstack passed in as a parameter Since pre init can be called during architecture creation it is not parameterized with the architecture and must not call modules that use per architecture data struct gdbarch data gdbarch data register post init Function gdbarch data post init ftype post init post_init is used to obtain an initial value for a per architecture data pointer after Since post init is always called after architecture creation it both receives the fully initialized architecture and is free to call modules that use per arch
100. ecome very complicated so they are implemented as functions here instead and the macro is simply defined to call the function This is vastly preferable since it is easier to understand and debug gdb arch tdep c gdb arch tdep h This often exists to describe the basic layout of the target machine s processor chip registers stack etc If used it is included by ttt tdep h It can be shared among many targets that use the same processor gdb config arch tm ttt h tm h is a link to this file created by configure Contains macro definitions about the target machine s registers stack frame format and instructions New targets do not need this file and should not create it Chapter 9 Target Architecture Definition 55 gdb config arch tm arch h This often exists to describe the basic layout of the target machine s processor chip registers stack etc If used it is included by tm ttt h It can be shared among many targets that use the same processor New targets do not need this file and should not create it If you are adding a new operating system for an existing CPU chip add a config tm os h file that describes the operating system facilities that are unusual extra symbol table info the breakpoint instruction needed etc Then write a arch tm os h that just includes tm arch h and config tm os h 9 12 Converting an existing Target Architecture to Mul
101. ectly included An external declaration should only appear in one include file An external declaration should never appear in a c file Exception a declaration for the _initialize function that pacifies Wmissing declaration A typedef definition should only appear in one include file An opaque struct declaration can appear in multiple h files Where possible a h file should use an opaque struct declaration instead of an include All h files should be wrapped in ifndef INCLUDE_FILE_NAME_H define INCLUDE_FILE_NAME_H header body endif 13 4 11 Clean Design and Portable Implementation In addition to getting the syntax right there s the little question of semantics Some things are done in certain ways in GDB because long experience has shown that the more obvious ways caused various kinds of trouble You can t assume the byte order of anything that comes from a target including values object files and instructions Such things must be byte swapped using SWAP_TARGET_AND_ HOST in GDB or one of the swap routines defined in bfd h such as bfd_get_32 You can t assume that you know what interface is being used to talk to the target system All references to the target must go through the current target ops vector You can t assume that the host and target machines are the same machine except in the native support modules In particular you can t assume that the target machine s h
102. els 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 or absence of markup has been arranged to thwart or discourage subsequent modification by readers is not Transparent An image format is not Transparent if used for any substantial amount of text A copy that is not Transparent is called Opaque Examples of suitable formats for Transparent copies include plain ASCII without markup Texinfo input format La TEX input format SGML or XML using a publicly available DTD and standard conforming simple HTML PostScript or PDF designed for human modification Examples of transparent image formats include PNG XCF and JPG Opaque formats include 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 PostScript or PDF produced by some word processors for output purposes only The 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 the title page For works in formats which do not have any title page as such Title Page means the text near the mos
103. embly listing and give it to x i Adding an architecture method like INTEGER_TO_ADDRESS certainly makes it possible for GDB to get it right in all circumstances See Chapter 9 Pointers Are Not Always Addresses page 31 NO_HIF_SUPPORT Specific to the a29k POINTER TO ADDRESS type buf Assume that buf holds a pointer of type type in the appropriate format for the current architecture Return the byte address the pointer refers to See Chapter 9 Pointers Are Not Always Addresses page 31 REGISTER CONVERTIBLE reg Return non zero if reg uses different raw and virtual formats See Chapter 9 Raw and Virtual Register Representations page 31 REGISTER TO VALUE regnum type from to Convert the raw contents of register regnum into a value of type type See Chap ter 9 Using Different Register and Memory Data Representations page 31 DEPRECATED REGISTER RAW SIZE reg Return the raw size of reg defaults to the size of the register s virtual type See Chapter 9 Raw and Virtual Register Representations page 31 register reggroup p gdbarch regnum reggroup Return non zero if register regnum is a member of the register group reggroup By default registers are grouped as follows float reggroup Any register with a valid name and a floating point type vector reggroup Any register with a valid name and a vector type general reggroup Any register with a valid name and a type other than vector or floating
104. er of columns in the table nr rows is the number of rows in the table tblid is an optional string identifying the table The string pointed to by tblid is copied by the implementation of ui out table begin so the application can free the string if it was malloced The companion function ui out table end described below marks the end of the table s output void ui out table header struct ui out uiout int width enum Function ui_align alignment const char colhdr ui out table header provides the header information for a single table column You call this function several times one each for every column of the table after ui out table begin but before ui out table body The value of width gives the column width in characters The value of alignment is one of left center and right and it specifies how to align the header left justify center or right justify it colhdr points to a string that specifies the column header the implementation copies that string so column header strings in malloced storage can be freed after the call void ui out table body struct ui_out uiout Function This function delimits the table header from the table body void ui out table end struct ui_out uiout Function This function signals the end of a table s output It should be called after the table body has been produced by the list and field output functions There should be exactly one call to ui out table end for each
105. ersion in and ChangeLog to read L M N 0000 00 00 cvs so that the ver sion update process can restart 3 Make the release candidate available in ftp sources redhat com pub gdb snapshots branchf 4 Notify the relevant mailing lists gdb sources redhat com and gdb testers sources redhat comf that the candidate is available Chapter 16 Releasing GDB 84 16 6 4 Make a formal release available And you thought all that was required was to post an e mail Install on sware Copy the new files to both the release and the old release directory cp bz2 gz ftp pub gdb old releases cp bz2 gz ftp pub gdb releases Clean up the releases directory so that only the most recent releases are available e g keep 5 2 and 5 2 1 but remove 5 1 cd ftp pub gdb releases rm Update the file README and message in the releases directory vi README rm f message 1n README message Update the web pages htdocs download ANNOUNCEMENT This file which is posted as the official announcement includes e General announcement e News If making an M N 1 release retain the news from earlier M N release e Errata htdocs index html1 htdocs news index html htdocs download index html These files include e announcement of the most recent release e news entry remember to update both the top level and the news directory These pages also need to be regenerate usin
106. et doesn t define its own printing routine it defaults to an accessor function for the global pointer deprecated tm print insn This usually points to a function in the opcodes library see Chapter 12 Opcodes page 62 info is a structure of type disassemble info defined in include dis asm h used to pass information to the instruction decoding routine struct frame id unwind dummy id struct frame info frame Given frame return a struct frame id that uniquely identifies an inferior function call s dummy frame The value returned must match the dummy frame stack value previously saved using SAVE DUMMY FRAME TOS See SAVE DUMMY FRAME TOS page 50 DEPRECATED USE STRUCT CONVENTION gcc p type If defined this must be an expression that is nonzero if a value of the given type being returned from a function must have space allocated for it on the stack gcc p is true if the function being considered is known to have been compiled by GCC this is helpful for systems where GCC is known to use different calling convention than other compilers This method has been deprecated in favour of gdbarch return value see gdbarch return value page 50 VALUE TO REGISTER type regnum from to Convert a value of type type into the raw contents of register regnum s See Chapter 9 Using Different Register and Memory Data Representations page 31 Chapter 9 Target Architecture Definition 54 VARIABLES INSIDE BLOCK desc
107. ete sects REX es 22 ESEEK NOT LINEAR 2 92 2 2 di e eek 30 Appendix B Index M Make clean p s c iis e e REX e ETIN 64 making a new release of gdb 77 memory representation sse 37 MEMORY_INSERT_BREAKPOINT 41 MEMORY REMOVE BREAKPOINT 41 minimal symbol table 002204 22 Imsyrptabs usted ep RR 22 mm p sienikseesepicePerieeRebtpiescr esaduns 29 multi arch data i22 cato ree RR Ren 65 N NAME OF MALLOC e ts kere aa eas 54 NATDEPPULES 64 incited ie aglosicoeaa ten Re 58 native conditionals 00000 60 native core filles 2 2 oes cda Ses nerak 59 native debugging 4o orette y ERR eREEEES 58 nesting level in ui out functions 11 Netware Loadable Module format 24 NO HIE SUPPORT 22i na R eRR dan ee ae 47 NO_STD REGS iiu PAR EA RARE 29 NORETURN 22s neck Dae Rx ERE ook 30 normal Stop Ge rege e korea PORE pes 92 normal stop observer 2e eeeeee 92 notification about inferior execution stop 92 notifications about changes in internals 9 O object file formats css ceo rr Rege 23 observer pattern interface 0005 9 observers implementation rationale 91 obsolete code sis clseses La ieee dees ed oe 91 ObStackS c ines se bonos pai EE bebe ode 63 ONE PROCESS WRITETEXT i ole 61 op print tab d 9 e o ERREEEERR 27 opcodes library i a os
108. f2 addr class Returns the type flags needed to construct a pointer type whose size is byte_size and whose address class is dwarf2 addr class This function is normally called from within a symbol reader See dwarf2read c char ADDRESS CLASS TYPE FLAGS TO NAME int type flags Target Macro Given the type flags representing an address class qualifier return its name int ADDRESS CLASS NAME to TYPE FLAGS int name int Target Macro vartype flags ptr Given an address qualifier name set the int refererenced by type flags ptr to the type flags for that address class qualifier Since the need for address classes is rather rare none of the address class macros defined by default Predicate macros are provided to detect when they are defined Consider a hypothetical architecture in which addresses are normally 32 bits wide but 16 bit addresses are also supported Furthermore suppose that the DWARF 2 information for this architecture simply uses a DW AT byte size value of 2 to indicate the use of one of these short pointers The following functions could be defined to implement the address class macros somearch address class type flags int byte size int dwarf2 addr class 1 if byte size 2 return TYPE FLAG ADDRESS CLASS 1 else return 0 static char somearch_address_class_type_flags_to_name int type flags 1 if type flags amp TYPE FLAG ADDRESS CLASS 1 return short Chapter 9 Target Ar
109. fficient used to satisfy the specifiers in the supplied format When a character string argument is not used in a ui_out function call a NULL pointer has to be supplied instead 4 2 3 Table Tuple and List Functions This section introduces ui_out routines for building lists tuples and tables The routines to output the actual data items fields are presented in the next section To recap A tuple is a sequence of fields each field containing information about an object a list is a sequence of fields where each field describes an identical object Use the table functions when your output consists of a list of rows tuples and the console output should include a heading Use this even when you are listing just one object but you still want the header Tables can not be nested Tuples and lists can be nested up to a maximum of five levels The overall structure of the table output code is something like this ui_out_table_begin ui_out_table_header ui_out_table_body ui_out_tuple_begin ui_out_field_ ui_out_tuple_end ui_out_table_end Here is the description of table tuple and list related ui_out functions Chapter 4 User Interface 12 void ui out table begin struct ui out uiout int nbrofcols int Function nr rows const char tblid The function ui out table begin marks the beginning of the output of a table It should always be called before any other ui out function for a given table nbrofcols is the numb
110. finition should have its name in column zero Declaration static void foo void Definition void foo void 1 Pragmatics This simplifies scripting Function definitions can be found using function name There must be a space between a function or macro name and the opening parenthesis of its argument list except for macro definitions as required by C There must not be a space after an open paren bracket or before a close paren bracket While additional whitespace is generally helpful for reading do not use more than one blank line to separate blocks and avoid adding whitespace after the end of a program line as of 1 99 some 600 lines had whitespace after the semicolon Excess whitespace causes difficulties for diff and patch utilities Pointers are declared using the traditional K amp R C style void foo and not void foo void foo 13 4 5 Comments The standard GNU requirements on comments must be followed strictly Block comments must appear in the following form with no or only lines and no leading Wait for control to return from inferior to debugger If inferior gets a signal we may decide to start it up again instead of returning That is why there is a loop in this function When this function actually returns it means the inferior should be left Stopped and GDB should read more commands Note that this format is encouraged by Emacs tabbing for a multi line comment
111. ft 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 License is not limited to software manuals it can be used for any textual work regardless of subject matter or whether it is published as a printed book We recommend this License principally for works whose purpose is instruction or reference APPLICABILITY AND DEFINITIONS This License applies to any manual or other work in any medium that contains a notice placed by the copyright holder saying it can be distributed under the terms of this License Such a notice grants a world wide royalty free license unlimited in duration to use that work under the conditions stated herein The Document below refers to any such manual or work Any member of the public is a licensee and is addressed as you You accept the license if you copy modify or distribute the work in a way requiring permission under copyright law A Modified Version of the Document means any work containing the Document or a portion of it either copied verbatim or with modifications and or translated into another language A Secondary Section is a named appendix or a front matter section of the Document that deals exclusively with the relationship of the publishers or authors of the Document to
112. g index sh download onlinedocs You need to find the magic command that is used to generate the online docs from the tar bz2 The best way is to look in the output from one of the nightly cron jobs and then just edit accordingly Something like ss update web docs ftp pub gdb releases gdb 5 2 tar bz2 PWD www www sourceware htdocs gdb download onlinedocs gdb download ari Just like the online documentation Something like bin sh ss update web ari ftp pub gdb releases gdb 5 2 tar bz2 PWD www www sourceware htdocs gdb download ari gdb Chapter 16 Releasing GDB 85 Shadow the pages onto gnu Something goes here Install the GDB tar ball on GNU At the time of writing the GNU machine was gnudist gnu org in ftp gnu gdb Make the ANNOUNCEMENT Post the ANNOUNCEMENT file you created above to e GDB Announcement mailing list e General GNU Announcement list but delay it a day or so to let things get out e GDB Bug Report mailing list 16 6 5 Cleanup The release is out but you re still not finished Commit outstanding changes In particular you ll need to commit any changes to e gdb ChangeLog e gdb version in e gdb NEWS e gdb README Tag the release Something like d date u Y m 7 d echo d 2002 01 24 cd insight src gdb amp amp cvs f q update cd insight src amp amp cvs f q tag gdb_5_2 d release
113. gcc p For dbx style debugging information if the compiler puts variable declarations inside LBRAC RBRAC blocks this should be defined to be nonzero desc is the value of n desc from the N RBRAC symbol and gcc p is true if GDB has no ticed the presence of either the GCC COMPILED SYMBOL or the GCC2_COMPILED_ SYMBOL By default this is 0 OS9K VARIABLES INSIDE BLOCK desc gcc p Similarly for OS 9000 Defaults to 1 Motorola M68K target conditionals BPT VECTOR Define this to be the 4 bit location of the breakpoint trap vector If not defined it will default to Oxf REMOTE_BPT_VECTOR Defaults to 1 NAME_OF_MALLOC A string containing the name of the function to call in order to allocate some memory in the inferior The default value is malloc 9 11 Adding a New Target The following files add a target to GDB gdb config arch ttt mt Contains a Makefile fragment specific to this target Specifies what object files are needed for target ttt by defining TDEPFILES and TDEPLIBS Also specifies the header file which describes ttt by defining TM_FILE tm ttt h You can also define TM_CFLAGS TM_CLIBS TM_CDEPS but these are now deprecated replaced by autoconf and may go away in future versions of GDB gdb ttt tdep c Contains any miscellaneous code required for this target machine On some machines it doesn t exist at all Sometimes the macros in tm ttt h b
114. ge 91 for a brief description of the observers cur rently implemented in GDB The rationale for the current implementation is also briefly discussed 4 User Interface GDB has several user interfaces Although the command line interface is the most common and most familiar there are others 4 1 Command Interpreter The command interpreter in GDB is fairly simple It is designed to allow for the set of commands to be augmented dynamically and also has a recursive subcommand capability where the first argument to a command may itself direct a lookup on a different command list For instance the set command just starts a lookup on the setlist command list while set thread recurses to the set thread cmd list To add commands in general use add cmd add com adds to the main command list and should be used for those commands The usual place to add commands is in the _initialize_xyz routines at the ends of most source files To add paired set and show commands use add setshow cmd or add setshow cmd full The former is a slightly simpler interface which is useful when you don t need to Chapter 4 User Interface 10 further modify the new command structures while the latter returns the new command structures for manipulation Before removing commands from the command set it is a good idea to deprecate them for some time Use deprecate cmd on commands or aliases to set the deprecated flag deprecate_cmd takes
115. h each Opaque copy a computer network location from which the general network using public has access to download using public standard network protocols a complete Transparent copy of the Document free of added material 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 Transparent copy will remain thus accessible at the stated location until at 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 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 Appendix B GNU Free Documentation License 96 N O Use in 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
116. h_in_function_epilogue_p 46 gdbarch init osabizi 2 e red RR d tn ted 32 gdbarch register osabi 2 2 229 32 gdbarch_register_osabi_sniffer 32 gdbarch return valley 2 2 02 csteieetavaee ed 50 GDBINIT_FILENAME ccert anere sore ds 29 generic host support 000s ee eee 28 GET LONGJMP TARGET 4 45 60 H hardware breakpoints 000 2000 3 hardware watchpoints lssless esses 4 HAVE CONTINUABLE WATCHPOINT 6 HAVE DOS BASED FILE SYSTEM 72 HAVE LONG DOUBLE 4 222 rhe han 30 HAVE MMAP Loro oe tt IRELERV REI EXE VOR SS 29 HAVE NONSTEPPABLE WATCHPOINT 6 HAVE_STEPPABLE_WATCHPOINT 6 HAVE TERMI 4 242292 dob gh d hn 29 hog eie leseCReR T XEM EVUWEDIPLPERREL 2 101 I 1386 cleanup dregs o n ga Re eng 8 1386 DR LUW GET STATUS 2 ee n 7 1386_DR_LOW_RESET_ADDR 542005038 20 4 7 1386 DR LOW SET ADDR 6 502 264 4834 5 402 Pde sae T I386 DR LOW SET CONTROL 7 i386 insert hw breakpoint 8 i386 insert watchpoint 8 1386 region ok for watchpoint 7 i386_remove_hw_breakpoint 8 i386 remove watchpoint 8 1386 stopped by hwbp c Rei 8 1386 stopped by watchpoint 8 1386 stopped data address 7 I386 USE GENERIC WATCHPOINTS
117. he appropriate way for the current architecture Unfortunately since addresses and pointers are identical on almost all processors this distinction tends to bit rot pretty quickly Thus each time you port GDB to an architecture which does distinguish between pointers and addresses you ll probably need to clean up some architecture independent code Here are functions which convert between pointers and addresses 3 Some D10V instructions are actually pairs of 16 bit sub instructions However since you can t jump into the middle of such a pair code addresses can only refer to full 32 bit instructions which is what matters in this explanation Chapter 9 Target Architecture Definition 34 CORE ADDR extract typed address void buf struct type type Function Treat the bytes at buf as a pointer or reference of type type and return the address it represents in a manner appropriate for the current architecture This yields an address GDB can use to read target memory disassemble etc Note that buf refers to a buffer in GDB s memory not the inferior s For example if the current architecture is the Intel x86 this function extracts a little endian integer of the appropriate length from buf and returns it However if the current architecture is the D10V this function will return a 16 bit integer extracted from buf multiplied by four if type is a pointer to a function If type is not a pointer or reference type then this functio
118. heir titles with the Front Cover Texts being list and with the Back Cover Texts being list If you have Invariant Sections without Cover Texts or some other combination of the three merge those two alternatives to suit the situation 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 Public License to permit their use in free software Index ADDRESS_CLASS_TYPE_FLAGS_TO_NAME 35 edbarch data eie he ie nO E oyi oes 66 initialize lang uage l l59 eb un 2T A aout formal imm RE ERE une D 23 POAC sass inu Scie bd Sees dro nig n E dns aMier ang qub 9 add C m iade ehe du ite ethos irode a Rods 9 add s tshow cmd iile pe c e deiert REY E Ya 9 add setshow cmd full ss 9 add symtab fhnS certe ean eased eas 20 adding ew host x 21222 xe FRE etes 28 adding a symbol reading module 20 adding target priri 9 Rm E OPE 54 adding debugging info reader 25 adding source language 04 26 ADDR BITS REMOVE e reE ERE REX Rees 39 address classes ssleleeeseeeeeseees 35 address representation 00 00 ee 33 address spaces separate data and code 33 ADDRESS CLASS NAME to TYPE FLAGS 35 ADDRESS CLASS NAME TO TYPE FLAGS 39 ADDRESS CLASS NAME TO TYPE FLAGS P
119. hould always be searched before the psymtab so the psymtab will never be used in a bug free environment Currently psymtabs are allocated on an obstack and all the psymbols themselves are allocated in a pair of large arrays on an obstack so there is little to be gained by trying to free them unless you want to do a lot more work 6 3 Types Fundamental Types e g FT VOID FT BOOLEAN These are the fundamental types that GDB uses internally Fundamental types from the various debugging formats stabs ELF etc are mapped into one of these They are ba sically a union of all fundamental types that GDB knows about for all the languages that GDB knows about Type Codes e g TYPE CODE PTR TYPE CODE ARRAY Each time GDB builds an internal type it marks it with one of these types The type may be a fundamental type such as TYPE CODE INT or a derived type such as TYPE CODE PTR which is a pointer to another type Typically several FT types map to one TYPE CODE type and are distinguished by other members of the type struct such as whether the type is signed or unsigned and how many bits it uses Builtin Types e g builtin type void builtin type char These are instances of type structs that roughly correspond to fundamental types and are created as global types for GDB to use for various ugly historical reasons We eventually want to eliminate these Note for example that builtin type int initialized in gdbtypes c
120. hould just provide fetch core registers in xyz nat c or REGISTER_U_ADDR in nm xyz h core aout c register addr If your nm xyz h file defines the macro REGISTER U ADDR addr blockend regno it should be defined to set addr to the offset within the user struct of GDB register number regno blockend is the offset within the upage of u u_ arO If REGISTER U ADDR is defined core aout c will define the register addr function and use the macro in it If you do not define REGISTER U ADDR but you are using the standard fetch core registers you will need to define your own version of register addr put it into your xyz nat c file and be sure xyz nat o is in the NATDEPFILES list If you have your own fetch core registers you may not need a separate register addr Many custom fetch core registers implementations simply locate the registers themselves When making GDB run native on a new operating system to make it possible to debug core files you will need to either write specific code for parsing your OS s core files or customize bfd trad core c First use whatever include files your machine uses to define the struct of registers that is accessible possibly in the u area in a core file rather than machine reg h and an include file that defines whatever header exists on a core file e g the u area or a struct core Then modify trad unix core file p to use these values to set up the sect
121. i out builder using its own versions of the ui file gdb_stderr gdb_stdtarg and gdb_stdout streams e The client creates a separate custom ui out builder that is only used while making direct queries to libgdb Chapter 6 Symbol Handling 20 When the client receives input intended for the CLI it simply passes it along Since the cli out builder is installed by default all the CLI output in response to that command is routed pronounced rooted through to the client controlled gdb_stdout et al streams At the same time the client is kept abreast of internal changes by virtue of being a libgdb observer The only restriction on the client is that it must wait until libgdb becomes idle before initiating any queries using the client s custom builder 5 5 libgdb components Observer gdb events h gdb events provides the client with a very raw mechanism that can be used to implement an observer At present it only allows for one observer and that observer must internally handle the need to delay the processing of any event notifications until after libgdb has finished the current command Builder ui out h ui out provides the infrastructure necessary for a client to create a builder That builder is then passed down to libgdb when doing any queries Event Loop event loop h event loop currently non re entrant provides a simple event loop A client would need to either plug its self into this l
122. iate value for the system 1seek if not already defined STOP SIGNAL This is the signal for stopping GDB Defaults to SIGTSTP Only redefined for the Convex USG Means that System V prior to SVR4 include files are in use FIXME This symbol is abused in infrun c regex c and utils c for other things at the moment lint Define this to help placate lint in some situations volatile Define this to override the defaults of volatile or Chapter 9 Target Architecture Definition 31 9 Target Architecture Definition GDB s target architecture defines what sort of machine language programs GDB can work with and how it works with them The target architecture object is implemented as the C structure struct gdbarch The structure and its methods are generated using the Bourne shell script gdbarch sh 9 1 Operating System ABI Variant Handling GDB provides a mechanism for handling variations in OS ABIs An OS ABI variant may have influence over any number of variables in the target architecture definition There are two major components in the OS ABI mechanism sniffers and handlers A sniffer examines a file matching a BFD architecture flavour pair the architecture may be wildcarded in an attempt to determine the OS ABI of that file Sniffers with a wildcarded architecture are considered to be generic while sniffers for a specific architecture are considered to be specific A match from a specif
123. ibute However you may accept compensation in exchange for copies If 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 or copies in media that commonly have printed covers of the Document numbering more than 100 and the Document s license notice requires Cover lexts you must enclose the 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 clearly 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 Transparent copy along with each Opaque copy or state in or wit
124. ic sniffer overrides a match from a generic sniffer Multiple sniffers for an architecture flavour may exist in order to differentiate between two different operating systems which use the same basic file format The OS ABI framework provides a generic sniffer for ELF format files which examines the EI_OSABI field of the ELF header as well as note sections known to be used by several operating systems A handler is used to fine tune the gdbarch structure for the selected OS ABI There may be only one handler for a given OS ABI for each BFD architecture The following OS ABI variants are defined in osabi h GDB_OSABI_UNKNOWN The ABI of the inferior is unknown The default gdbarch settings for the architecture will be used GDB_OSABI_SVR4 UNIX System V Release 4 GDB_OSABI_HURD GNU using the Hurd kernel GDB_OSABI_SOLARIS Sun Solaris GDB_OSABI_OSF1 OSF 1 including Digital UNIX and Compaq Tru64 UNIX GDB_OSABI_LINUX GNU using the Linux kernel GDB_OSABI_FREEBSD_AOUT FreeBSD using the a out executable format GDB_OSABI_FREEBSD_ELF FreeBSD using the ELF executable format GDB_OSABI_NETBSD_AOUT NetBSD using the a out executable format Chapter 9 Target Architecture Definition 32 GDB_OSABI_NETBSD_ELF NetBSD using the ELF executable format GDB_OSABI_WINCE Windows CE GDB OSABI G032 DJGPP GDB OSABI NETWARE Novell NetWare GDB OSABI ARM EABI V1 ARM Embedded ABI version 1 GDB OSABI ARM EABI V2
125. if necessary for instance for prototypes gdb lang Language specific tests for any language lang besides C Examples are gdb cp and gdb java gdb platform Non portable tests The tests are specific to a specific configuration host or target such as HP UX or eCos Example is gdb hp for HP UX Chapter 18 Hints 88 gdb compiler Tests specific to a particular compiler As of this writing June 1999 there aren t currently any groups of tests in this category that couldn t just as sensibly be made platform specific but one could imagine a gdb gcc for tests of GDB s handling of GCC extensions gdb subsystem Tests that exercise a specific GDB subsystem in more depth For instance gdb disasm exercises various disassemblers while gdb stabs tests pathways through the stabs symbol reader 17 3 Writing Tests In many areas the GDB tests are already quite comprehensive you should be able to copy existing tests to handle new cases You should try to use gdb test whenever possible since it includes cases to handle all the unexpected errors that might happen However it doesn t cost anything to add new test procedures for instance gdb base exprs exp defines a test expr that calls gdb test multiple times Only use send gdb and gdb expect when absolutely necessary such as when GDB has several valid responses to a command The source language progr
126. ike the feature we can add it to the sources with a single patch command do some testing and check it in If you leave out the ChangeLog we have to write one If you leave out the doc we have to puzzle out what needs documenting Etc etc The reason to send each change in a separate message is that we will not install some of the changes They ll be returned to you with questions or comments If we re doing our job correctly the message back to you will say what you have to fix in order to make the change acceptable The reason to have separate messages for separate features is so that the acceptable changes can be installed while one or more changes are being reworked If multiple features are sent in a single message we tend to not put in the effort to sort out Appendix A GDB Currently available observers 91 the acceptable changes from the unacceptable so none of the features get installed until all are acceptable If this sounds painful or authoritarian well it is But we get a lot of bug reports and a lot of patches and many of them don t get installed because we don t have the time to finish the job that the bug reporter or the contributor could have done Patches that arrive complete working and well designed tend to get installed on the day they arrive The others go into a queue and get installed as time permits which since the maintainers have many demands to meet may not be for quite some time Please send p
127. improving the manual are always welcome of course 18 2 Debugging GDB with itself If GDB is limping on your machine this is the preferred way to get it fully functional Be warned that in some ancient Unix systems like Ultrix 4 2 a program can t be running in one process while it is being debugged in another Rather than typing the command gdb gdb which works on Suns and such you can copy gdb to gdb2 and then type gdb gdb2 Chapter 18 Hints 90 When you run GDB in the GDB source directory it will read a gdbinit file that sets up some simple things to make debugging gdb easier The info command when executed without a subcommand in a GDB being debugged by gdb will pop you back up to the top level gdb See gdbinit for details If you use emacs you will probably want to do a make TAGS after you configure your distribution this will put the machine dependent routines for your local machine where they will be accessed first by M Also make sure that you ve either compiled GDB with your local cc or have run fixincludes if you are compiling with gcc 18 3 Submitting Patches Thanks for thinking of offering your changes back to the community of GDB users In general we like to get well designed enhancements Thanks also for checking in advance about the best way to transfer the changes The GDB maintainers will only install cleanly designed patches This manual summa rizes what we believe to be
128. ion Binary Interface For almost all data types on almost all architectures the two representations are iden tical and no special handling is needed However they do occasionally differ Your ar chitecture may define the following macros to request conversions between the register and memory representations of a data type int CONVERT REGISTER P int reg Target Macro Return non zero if the representation of a data value stored in this register may be different to the representation of that same data value when stored in memory When non zero the macros REGISTER T0 VALUE and VALUE TO REGISTER are used to perform any necessary conversion void REGISTER TO VALUE int reg struct type type char from Target Macro char to Convert the value of register number reg to a data object of type type The buffer at from holds the register s value in raw format the converted value should be placed in the buffer at to Note that REGISTER TO VALUE and VALUE TO REGISTER take their reg and type ar guments in different orders You should only use REGISTER TO VALUE with registers for which the CONVERT REGISTER P macro returns a non zero value void VALUE TO REGISTER struct type type int reg char from Target Macro char to Convert a data value of type type to register number reg raw format Note that REGISTER TO VALUE and VALUE TO REGISTER take their reg and type ar guments in different orders You should only
129. ion in insight src gdb version in cp gdb src gdb ChangeLog insight src gdb ChangeLog dejagnu src dejagnu configure in Dejagnu is more complicated The version number is a parameter to AM INIT AUTOMAKE Tweak it to read something like gdb 5 1 91 Don t forget to re generate configure Don t forget to include a ChangeLog entry emacs dejagnu src dejagnu configure in c x 4a C X c S c X c c cd dejagnu src dejagnu amp amp autoconf Do the dirty work This is identical to the process used to create the daily snapshot for m in gdb insight do cd m src amp amp gmake f src release m tar done m dejagnu cd m src amp amp gmake f src release m tar bz2 If the top level source directory does not have src release GDB version 5 3 1 or earlier try these commands instead for m in gdb insight do cd m src amp amp gmake f Makefile in m tar done m dejagnu cd m src amp amp gmake f Makefile in m tar bz2 Check the source files You re looking for files that have mysteriously disappeared distclean has the habit of deleting files it shouldn t Watch out for the version in update cronjob cd gdb src amp amp cvs f q n update M djunpack bat gdb 5 1 91 tar proto toplev lots of generated files M gdb ChangeLog M gdb NEWS M gdb README Chapter 16 Releasing GDB 83 M gdb version in lots of generated files Don t worry about
130. ion information for the data segment stack segment any other segments in the core file perhaps shared library contents or control information registers segment and if there are two discontiguous sets of registers e g integer and float the reg2 segment This section information basically delimits areas in the core file in a standard way which the section reading routines in BFD know how to seek around in Then back in GDB you need a matching routine called fetch core registers If you can use the generic one it s in core aout c if not it s in your xyz nat c file It will be passed a char pointer to the entire registers segment its length and a zero or a char pointer to the entire regs2 segment its length and a 2 The routine should suck out the supplied register values and install them into GDB s registers array If your system uses proc to control processes and uses ELF format core files then you may be able to use the same routines for reading the registers out of processes and out of core files 11 2 ptrace Chapter 11 Native Debugging 60 11 3 proc 11 4 win32 11 5 shared libraries 11 6 Native Conditionals When GDB is configured and compiled various macros are defined or left undefined to control compilation when the host and target systems are the same These macros should be defined or left undefined in nm system h CHILD PREPARE TO STORE If the machine st
131. it print registers info gdbarch frame regnum all If defined pretty print the value of the register regnum for the specified frame If the value of regnum is 1 pretty print either all registers all is non zero or a select subset of registers all is zero The default method prints one register per line and if all is zero omits floating point registers PRINT VECTOR INFO If defined then the info vector command will call this function to print information about the processor s vector unit By default the info vector command will print all vector registers the reg ister s type having the vector attribute DWARF REG TO REGNUM Convert DWARF register number into GDB regnum If not defined no conver sion will be performed DWARF2 REG TO REGNUM Convert DWARF 2 register number into GDB regnum If not defined no con version will be performed ECOFF REG TO REGNUM Convert ECOFF register number into GDB regnum If not defined no conversion will be performed END OF TEXT DEFAULT This is an expression that should designate the end of the text section Chapter 9 Target Architecture Definition 43 EXTRACT RETURN VALUE type regbuf valbuf Define this to extract a function s return value of type type from the raw register state regbuf and copy that in virtual format into valbuf This method has been deprecated in favour of gdbarch return value see gdbarch return value page 50 DEPRECATE
132. itecture data care needs to be taken to ensure that those other modules do not try to call back to this module as that will create in cycles in the initialization call graph Chapter 13 Coding 66 These functions return a struct gdbarch data that is used to identify the per architecture data pointer added for that module The per architecture data pointer is accessed using the function void gdbarch data struct gdbarch gdbarch struct gdbarch data Function data handle Given the architecture arch and module data handle data handle returned by gdbarch data register pre init or gdbarch data register post init this function returns the current value of the per architecture data pointer If the data pointer is NULL it is first initialized by calling the corresponding pre_init or post init method The examples below assume the following definitions struct nozel int total static struct gdbarch data nozel handle A module can extend the architecture vector adding additional per architecture data using the pre init method The module s per architecture data is then initialized during architecture creation In the below the module s per architecture nozel is added An architecture can specify its nozel by calling set gdbarch nozel from gdbarch init static void nozel pre init struct obstack obstack 1 struct nozel data OBSTACK ZALLOC obstack struct nozel return data extern void set_gdb
133. ituation but is known to occur on several different types of systems CRLF SOURCE FILES Define this if host files use r n rather than Nn as a line terminator This will cause source file listings to omit r characters when printing and it will allow r n line endings of files which are sourced by gdb It must be possible to open files in binary mode using 0 BINARY or for fopen rb DEFAULT PROMPT The default value of the prompt string normally gdb DEV TTY The name of the generic TTY device defaults to dev tty FOPEN RB Define this if binary files are opened the same way as text files HAVE MMAP In some cases use the system call mmap for reading symbol tables For some machines this allows for sharing and quick updates HAVE TERMIO Define this if the host system has termio h INT MAX INT MIN LONG MAX UINT MAX ULONG MAX Values for host side constants ISATTY Substitute for isatty if not available LONGEST This is the longest integer type available on the host If not defined it will default to long long or long depending on CC HAS LONG LONG Chapter 9 Target Architecture Definition 30 CC HAS LONG LONG Define this if the host C compiler supports long long This is set by the configure script PRINTF HAS LONG LONG Define this if the host can handle printing of long long integers via the printf format conversion specifier 11 This is set by the configure script HAVE LONG DOU
134. ively clearing the slate the developer has a much freer hand when it comes to fixing broken files 16 3 Before the Branch The most important objective at this stage is to find and fix simple changes that become a pain to track once the branch is created For instance configuration problems that stop GDB from even building If you can t get the problem fixed document it in the gdb PROBLEMS file Prompt for gdb NEWS People always forget Send a post reminding them but also if you know something interesting happened add it yourself The schedule script will mention this in its e mail Review gdb README Grab one of the nightly snapshots and then walk through the gdb README looking for anything that can be improved The schedule script will mention this in its e mail Refresh any imported files A number of files are taken from external repositories They include e texinfo texinfo tex e config guess et al see the top level MAINTAINERS file e etc standards texi etc make stds texi Check the ARI A R L is an awk script Awk Regression Index that checks for a number of errors and coding conventions The checks include things like using malloc instead of xmalloc and file naming problems There shouldn t be any regressions 16 3 1 Review the bug data base Close anything obviously fixed 16 3 2 Check all cross targets build The targets are listed in gdb MAINTAINERS
135. l of the Invariant Sections of all of the original documents unmodified and list them all as Invariant Sections of your combined work in its license notice and that you preserve all their Warranty Disclaimers The combined work need only contain one copy of this License and multiple identical Invariant Sections may be replaced with a single copy If there are multiple Invariant Sections with the same name but different contents make the title of each such section unique by adding at the end of it in parentheses 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 vari ous original documents forming one section Entitled History likewise combine any sections Entitled Acknowledgements and any sections Entitled Dedications You must delete all sections Entitled Endorsements 6 COLLECTIONS OF DOCUMENTS You may make a collection consisting of the Document and other documents 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 fro
136. m dependent code where you need to take apart or construct a file name use the following portable macros HAVE DOS BASED FILE SYSTEM This preprocessing symbol is defined to a non zero value on hosts whose filesys tems belong to the MS DOS MS Windows family Use this symbol to write conditional code which should only be compiled for such hosts IS DIR SEPARATOR c Evaluates to a non zero value if c is a directory separator character On Unix and GNU Linux systems only a slash is such a character but on Windows both and V will pass IS ABSOLUTE PATH file Evaluates to a non zero value if file is an absolute file name For Unix and GNU Linux hosts a name which begins with a slash is absolute On DOS and Windows d foo and x bar are also absolute file names FILENAME CMP f1 f2 Calls a function which compares file names fl and f2 as appropriate for the underlying host filesystem For Posix systems this simply calls strcmp on case insensitive filesystems it will call strcasecmp instead DIRNAME SEPARATOR Evaluates to a character which separates directories in PATH style lists typically held in environment variables This character is on Unix on DOS and Windows SLASH STRING This evaluates to a constant string you should use to produce an absolute filename from leading directories and the file s basename SLASH STRING is on most systems but might be NN for some Windo
137. m such a collection and distribute it individu ally 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 Appendix B GNU Free Documentation License 98 7T AGGREGATION WITH INDEPENDENT WORKS 10 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 is called an aggregate if the copyright resulting from the compilation is not used to limit the legal rights of the compilation s users beyond what the individual works permit When the Document is included in an aggregate this License does not apply to the other works in the aggregate which 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 half of the entire aggregate the Document s Cover Texts may be placed on covers that bracket the Document within the aggregate or the electronic equivalent of covers if the Document is in electronic form Otherwise they must appear on printed covers that bracket the whole aggregate 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 permissio
138. n 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 and all the license notices in the Document and any Warranty Disclaimers provided that you also include the original English version of this License and the original versions of those notices and disclaimers In case of a disagreement between the translation and the original version of this License or a notice or disclaimer the original version will prevail If a section in the Document is Entitled Acknowledgements Dedications or His tory the requirement section 4 to Preserve its Title section 1 will typically require changing the actual title TERMINATION You may not copy modify sublicense or distribute the Document except as expressly provided for 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 parties 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 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 ma
139. n will signal an internal error CORE ADDR store typed address void buf struct type type Function CORE ADDR addr Store the address addr in buf in the proper format for a pointer of type type in the current architecture Note that buf refers to a buffer in GDB s memory not the inferior s For example if the current architecture is the Intel x86 this function stores addr unmodified as a little endian integer of the appropriate length in buf However if the current architecture is the D10V this function divides addr by four if type is a pointer to a function and then stores it in buf If type is not a pointer or reference type then this function will signal an internal error CORE ADDR value as address struct value val Function Assuming that val is a pointer return the address it represents as appropriate for the current architecture This function actually works on integral values as well as pointers For pointers it performs architecture specific conversions as described above for extract typed address CORE ADDR value from pointer struct type type CORE ADDR Function addr Create and return a value representing a pointer of type type to the address addr as appropriate for the current architecture This function performs architecture specific conversions as described above for store typed address Here are some macros which architectures can define to indicate the relationship between pointers and a
140. nargs the code should push struct addr when struct return and the return address bp addr function is a pointer to a struct value on architectures that use function descriptors this contains the function descriptor value Returns the updated top of stack pointer Chapter 9 Target Architecture Definition 50 This method replaces DEPRECATED PUSH ARGUMENTS CORE ADDR push dummy code gdbarch sp funaddr using gcc args nargs value type real pc bp addr Given a stack based call dummy push the instruction sequence including space for a breakpoint to which the called function should return Set bp addr to the address at which the breakpoint instruction should be in serted real pc to the resume address when starting the call sequence and return the updated inner most stack address By default the stack is grown sufficient to hold a frame aligned see frame align page 43 breakpoint bp_addr is set to the address reserved for that breakpoint and real pc set to funaddr This method replaces CALL DUMMY LOCATION DEPRECATED REGISTER SIZE REGISTER NAME i Return the name of register i as a string May return NULL or NUL to indicate that register i is not valid DEPRECATED REG STRUCT HAS ADDR gcc p type Define this to return 1 if the given type will be passed by pointer rather than directly This method has been replaced by stabs argument has addr see stabs argument has addr page 49 SAVE
141. nd then when it s encountered GDB will take the exception and stop the program When the user says to continue GDB will restore the original instruction single step re insert the trap and continue on Since it literally overwrites the program being tested the program area must be writable so this technique won t work on programs in ROM It can also distort the behavior of programs that examine themselves although such a situation would be highly unusual Also the software breakpoint instruction should be the smallest size of instruction so it doesn t overwrite an instruction that might be a jump target and cause disaster when the program jumps into the middle of the breakpoint instruction Strictly speaking the Chapter 3 Algorithms 4 breakpoint must be no larger than the smallest interval between instructions that may be jump targets perhaps there is an architecture where only even numbered instructions may jumped to Note that it s possible for an instruction set not to have any instructions usable for a software breakpoint although in practice only the ARC has failed to define such an instruction The basic definition of the software breakpoint is the macro BREAKPOINT Basic breakpoint object handling is in breakpoint c However much of the interesting breakpoint action is in infrun c 3 3 Single Stepping 3 4 Signal Handling 3 5 Thread Handling 3 6 Inferior Function Calls 3 7 Longjmp Support GDB h
142. ng April 2001 setting verbosity level is not yet implemented and is always returned as zero So calling ui out message with a verbosity argument more than zero will cause the message to never be printed Chapter 4 User Interface if found_a_breakpoint 1 annotate breakpoints headers annotate field 0 printf filtered Num annotate field 1 printf filtered Type ms annotate field 2 printf filtered Disp annotate field 3 printf filtered Enb if addressprint 1 annotate field 4 printf filtered Address ys annotate_field 5 printf_filtered What n annotate_breakpoints_table Here s the new version nr_printable_breakpoints if addressprint ui_out_table_begin ui 6 nr_printable_breakpoints BreakpointTable else ui_out_table_begin ui 5 nr_printable_breakpoints BreakpointTable if nr_printable_breakpoints gt 0 annotate_breakpoints_headers if nr_printable_breakpoints gt 0 annotate_field 0 ui_out_table_header uiout 3 ui_left number Num 1 if nr_printable_breakpoints gt 0 annotate_field 1 ui_out_table_header uiout 14 ui_left type Type 2 if nr_printable_breakpoints gt 0 annotate_field 2 ui_out_table_header uiout 4 ui_left disp Disp 3 if nr_printable_breakpoints gt 0 annotate_field 3 ui out table header uiout 3 ui left enabled Enb 4 if ad
143. ng DJGPP and MacOS HFS Every time an unfriendly file is introduced to the build process both Chapter 13 Coding 71 Makefile in and configure in need to be modified accordingly Compare the convo luted conversion process needed to transform COPYING into copying c with the conversion needed to transform version in into version c Any file non 8 3 compliant file that is not used when building the core of GDB must be added to gdb config djgpp fnchange 1st Pragmatics This is clearly a compromise When GDB has a local version of a system header file ex string h the file name based on the POSIX header prefixed with gdb_ gdb_string h These headers should be relatively independent they should use only macros defined by configure the compiler or the host they should include only system headers they should refer only to system types They may be shared between multiple programs e g GDB and GDBSERVER For other files is used as the separator 13 4 10 Include Files A c file should include defs h first A c file should directly include the h file of every declaration and or definition it directly refers to It cannot rely on indirect inclusion A h file should directly include the h file of every declaration and or definition it directly refers to It cannot rely on indirect inclusion Exception The file defs h does not need to be dir
144. ng integer defaults to 2 TARGET LONG BIT TARGET PTR BIT Number of bits in a pointer defaults to TARGET INT BIT TARGET SHORT BIT Number of bits in a short integer defaults to 2 TARGET CHAR BIT Chapter 9 Target Architecture Definition 53 TARGET READ PC TARGET WRITE PC val pid TARGET READ SP TARGET READ FP These change the behavior of read pc write pc and read sp For most targets these may be left undefined GDB will call the read and write register functions with the relevant REGNUM argument These macros are useful when a target keeps one of these registers in a hard to get at place for example part in a segment register and part in an ordinary register See unwind sp page 44 which replaces TARGET READ SP TARGET VIRTUAL FRAME POINTER pc regp offsetp Returns register offset pair representing the virtual frame pointer in use at the code address pc If virtual frame pointers are not used a default definition simply returns DEPRECATED FP REGNUM with an offset of zero TARGET HAS HARDWARE WATCHPOINTS If non zero the target has support for hardware assisted watchpoints See Chapter 3 Algorithms page 2 for more details and other related macros TARGET PRINT INSN addr info This is the function used by GDB to print an assembly instruction It prints the instruction at address addr in debugged memory and returns the length of the instruction in bytes If a targ
145. ng with or For example dyncall is a millicode routine that handles inter space procedure calls on PA RISC DEPRECATED INIT EXTRA FRAME INFO fromleaf frame If additional information about the frame is required this should be stored in frame extra info Space for frame extra info is allocated using frame extra info zalloc DEPRECATED INIT FRAME PC fromleaf prev This is a C statement that sets the pc of the frame pointed to by prev By default INNER THAN 1hs rhs Returns non zero if stack address Ihs is inner than nearer to the stack top stack address rhs Define this as 1hs lt rhs if the target s stack grows downward in memory or 1hs gt rsh if the stack grows upward Egdbarch in function epilogue p gdbarch pc Returns non zero if the given pc is in the epilogue of a function The epilogue of a function is defined as the part of a function where the stack frame of the function already has been destroyed up to the final return from function call instruction DEPRECATED SIGTRAMP START pc DEPRECATED_SIGTRAMP_END pc Define these to be the start and end address of the sigtramp for the given pc On machines where the address is just a compile time constant the macro expansion will typically just ignore the supplied pc IN SOLIB CALL TRAMPOLINE pc name Define this to evaluate to nonzero if the program is stopped in the trampoline that connects to a shared library IN S
146. ns data Plus various strings such as directory names strings debug format strings names of types An essential and convenient property of all data on obstacks is that memory for it gets allocated with obstack_alloc at various times during a debugging sesssion but it is released all at once using the obstack free function The obstack free function takes a pointer to where in the stack it must start the deletion from much like the cleanup chains have a pointer to where to start the cleanups Because of the stack like structure of the obstacks this allows to free only a top portion of the obstack There are a few instances in GDB where such thing happens Calls to obstack free are done after some local data is allocated to the obstack Only the local data is deleted from the obstack Of course this assumes that nothing between the obstack alloc and the obstack free allocates anything else on the same obstack For this reason it is best and safest to use temporary obstacks Releasing the whole obstack is also not safe per se It is safe only under the condition that we know the obstacks memory is no longer needed In GDB we get rid of the obstacks only when we get rid of the whole objfile s for instance upon reading a new symbol file 12 6 gnu regex Regex conditionals C ALLOCA NFAILURES RE NREGS Chapter 13 Coding 64 SIGN EXTEND CHAR SWITCH ENUM BUG SYNTAX TABLE Sword Sparc 12 7 include 13 Coding This chapter covers
147. nst char id Function This function marks the beginning of a list output id points to an optional string that identifies the list it is copied by the implementation and so strings in malloced storage can be freed after the call void ui out list end struct ui out uiout Function This function signals an end of a list output There should be exactly one call to ui out list end for each call to ui out list begin otherwise an internal GDB error will be signaled struct cleanup make cleanup ui out list begin end struct ui_out Function uiout const char id Similar to make cleanup ui out tuple begin end this function opens a list and then establishes cleanup see Chapter 13 Coding page 64 that will close the list list 4 2 4 Item Output Functions The functions described below produce output for the actual data items or fields which contain information about the object Choose the appropriate function accordingly to your particular needs void ui out field fmt struct ui out uiout char fldname char Function format This is the most general output function It produces the representation of the data in the variable length argument list according to formatting specifications in format a printf like format string The optional argument fldname supplies the name of the field The data items themselves are supplied as additional arguments after format This generic function should be used only when
148. nvolves e The addition of a arch_gdbarch_init function that creates the architecture Static struct gdbarch diOv gdbarch init info arches struct gdbarch info info struct gdbarch list arches The above is from the original example and uses K amp R C GDB has since converted to ISO C but lets ignore that Chapter 9 Target Architecture Definition 56 struct gdbarch gdbarch there is only one di0v architecture if arches NULL return arches gt gdbarch gdbarch gdbarch alloc amp info NULL return gdbarch e per architecture dump function to print any architecture specific information Static void mips dump tdep struct gdbarch current gdbarch struct ui file file 1 code to print architecture specific info e A change to _initialize_arch_tdep to register this new architecture void _initialize_mips_tdep void gdbarch_register bfd_arch_mips mips_gdbarch_init mips_dump_tdep e Add the macro GDB_MULTI_ARCH defined as 0 zero to the file config arch tm arch h 9 12 3 Update multi arch incompatible mechanisms Some mechanisms do not work with multi arch They include FRAME_FIND_SAVED_REGS Replaced with DEPRECATED_FRAME_INIT_SAVED_REGS At this stage you could also consider converting the macros into functions 9 12 4 Prepare for multi arch level to one Temporally set GDB_MULTI_ARCH to GDB_MULTI_ARCH_PARTIAL and then build and start GDB the change should n
149. ol to code that runs in the target system GDB provides several sample stubs that can be integrated into target programs or operating systems for this purpose they are named stub c The GDB user s manual describes how to put such a stub into your target code What follows is a discussion of integrating the SPARC stub into a complicated operating system rather than a simple program by Stu Grossman the author of this stub The trap handling code in the stub assumes the following upon entry to trap_low 1 991 and 9612 contain pc and npc respectively at the time of the trap 2 traps are disabled 3 you are in the correct trap window As long as your trap handler can guarantee those conditions then there is no rea son why you shouldn t be able to share traps with the stub The stub has no require ment that it be jumped to directly from the hardware trap vector That is why it calls exceptionHandler which is provided by the external environment For instance this could set up the hardware traps to actually execute code which calls the stub first and then transfers to its own trap handler For the most point there probably won t be much of an issue with sharing traps as the traps we use are usually not used by the kernel and often indicate unrecoverable error conditions Anyway this is all controlled by a table and is trivial to modify The most important trap for us is for ta 1 Without that we can t single step o
150. ons functions that may be missing in some environments and operating systems replacement functions providing a uniform and easier to use interface for commonly used standard functions and extensions which provide additional functionality beyond standard functions GDB uses various features provided by the libiberty library for instance the C de mangler the IEEE floating format support functions the input options parser getopt the obstack extension and other functions 12 5 1 obstacks in GDB The obstack mechanism provides a convenient way to allocate and free chunks of memory Each obstack is a pool of memory that is managed like a stack Objects of any nature size and alignment are allocated and freed in a LIFO fashion on an obstack see libiberty s documenatation for a more detailed explanation of obstacks The most noticeable use of the obstacks in GDB is in object files There is an obstack associated with each internal representation of an object file Lots of things get allocated on these obstacks dictionary entries blocks blockvectors symbols minimal symbols types vectors of fundamental types class fields of types object files section lists object files section offets lists line tables symbol tables partial symbol tables string tables symbol table private data macros tables debug information sections and entries import and export lists som unwind information hppa dwarf2 location expressio
151. oop or implement a new event loop that GDB would use The event loop will eventually be made re entrant This is so that GDB can better handle the problem of some commands blocking instead of returning Library gdb h libgdb is the most obvious component of this system It provides the query interface Each function is parameterized by a ui out builder The result of the query is constructed using that builder before the query function returns 6 Symbol Handling Symbols are a key part of GDB s operation Symbols include variables functions and types 6 1 Symbol Reading GDB reads symbols from symbol files The usual symbol file is the file containing the program which GDB is debugging GDB can be directed to use a different file for symbols with the symbol file command and it can also read more symbols via the add file and load commands or while reading symbols from shared libraries Symbol files are initially opened by code in symfile c using the BFD library see Chapter 12 Support Libraries page 62 BFD identifies the type of the file by examining its header find sym fns then uses this identification to locate a set of symbol reading functions Chapter 6 Symbol Handling 21 Symbol reading modules identify themselves to GDB by calling add_symtab_fns during their module initialization The argument to add symtab fns is a struct sym fns which contains the name or name prefix of the sym
152. ores all registers at once in the child process then define this to ensure that all values are correct This usually entails a read from the child Note that this is incorrectly defined in xm system h files currently FETCH INFERIOR REGISTERS Define this if the native dependent code will provide its own routines fetch inferior registers and store inferior registers in host nat c If this symbol is not defined and infptrace c is included in this configura tion the default routines in infptrace c are used for these functions FPO REGNUM This macro is normally defined to be the number of the first floating point register if the machine has such registers As such it would appear only in target specific code However proc support uses this to decide whether floats are in use on this target GET LONGJMP TARGET For most machines this is a target dependent parameter On the DECstation and the Iris this is a native dependent parameter since setjmp h is needed to define it This macro determines the target PC address that 1ongjmp will jump to assum ing that we have just stopped at a longjmp breakpoint It takes a CORE ADDR as argument and stores the target PC value through this pointer It examines the current state of the machine as needed I386 USE GENERIC WATCHPOINTS An x86 based machine can define this to use the generic x86 watchpoint support see Chapter 3 Algorithms page 2 KERNE
153. ot be committed GDB may not build and once built it may die with an internal error listing the architecture methods that must be provided Fix any build problems patch es Convert all the architecture methods listed which are only macros into functions patch es Update arch gdbarch init to set all the missing architecture methods and wrap the corresponding macros in if GDB MULTI ARCH patch es 9 12 5 Set multi arch level one Change the value of GDB MULTI ARCH to GDB MULTI ARCH PARTIAL a single patch Any problems with throwing the switch should have been fixed already 9 12 6 Convert remaining macros Suggest converting macros into functions and setting the corresponding architecture method in small batches Chapter 10 Target Vector Definition 57 9 12 7 Set multi arch level to two This should go smoothly 9 12 8 Delete the TM file The tm arch h can be deleted arch mt and configure in updated 10 Target Vector Definition The target vector defines the interface between GDB s abstract handling of target systems and the nitty gritty code that actually exercises control over a process or a serial port GDB includes some 30 40 different target vectors however each configuration of GDB includes only a few of them 10 1 File Targets Both executables and core files have target vectors 10 2 Standard Protocol and Remote Stubs GDB s file remote c talks a serial protoc
154. out symbols and addresses e Partial symbol tables psymtabs These contain enough information to know when to read the corresponding part of the full symbol table e Minimal symbol tables msymtabs These contain information gleaned from non debugging symbols This section describes partial symbol tables A psymtab is constructed by doing a very quick pass over an executable file s debugging information Small amounts of information are extracted enough to identify which parts of the symbol table will need to be re read and fully digested later when the user needs the information The speed of this pass causes GDB to start up very quickly Later as the detailed rereading occurs it occurs in small pieces at various times and the delay therefrom is mostly invisible to the user The symbols that show up in a file s psymtab should be roughly those visible to the debugger s user when the program is not running code from that file T hese include external symbols and types static symbols and types and enum values declared at file scope The psymtab also contains the range of instruction addresses that the full symbol table would represent The idea is that there are only two ways for the user or much of the code in the debugger to reference a symbol e Dy its address e g execution stops at some address which is inside a function in this file The address will be noticed to be in the range of this psymtab and the full symta
155. owner name YYYYMMDD branch gdb owner name yyyymmdd mergepoint The tagged point on the mainline that was used when merging the branch on yyyymmdd To merge in all changes since the branch was cut use a command sequence like Chapter 16 Releasing GDB 77 cvs rtag owner_name yyyymmdd mergepoint gdb cvs update jowner __name YYYYMMDD branchpoint jowner __name yyyymmdd mergepoint Similar sequences can be used to just merge in changes since the last merge For further information on Cvs see Concurrent Versions System 16 Releasing GDB 16 1 Branch Commit Policy The branch commit policy is pretty slack GDB releases 5 0 5 1 and 5 2 all used the below e The gdb MAINTAINERS file still holds e Don t fix something on the branch unless until it is also fixed in the trunk If this isn t possible mentioning it in the gdb PROBLEMS file is better than committing a hack e When considering a patch for the branch suggested criteria include Does it fix a build Does it fix the sequence break main run when debugging a static binary e The further a change is from the core of GDB the less likely the change will worry anyone e g target specific code e Only post a proposal to change the core of GDB after you ve sent individual bribes to all the people listed in the MAINTAINERS file Pragmatics Provided updates are restricted to non core functionality there is little chance that a broken change will be
156. parsing type and value printing The target side consists of execution control stack frame analysis and physical target manipulation The target side symbol side division is not formal and there are a number of excep tions For instance core file support involves symbolic elements the basic core file reader is in BFD and target elements it supplies the contents of memory and the values of reg isters Instead this division is useful for understanding how the minor subsystems should fit together Chapter 3 Algorithms 2 2 1 The Symbol Side The symbolic side of GDB can be thought of as everything you can do in GDB without having a live program running For instance you can look at the types of variables and evaluate many kinds of expressions 2 2 The Target Side The target side of GDB is the bits and bytes manipulator Although it may make reference to symbolic info here and there most of the target side will run with only a stripped executable available or even no executable at all in remote debugging cases Operations such as disassembly stack frame crawls and register display are able to work with no symbolic info at all In some cases such as disassembly GDB will use symbolic info to present addresses relative to symbols rather than as raw numbers but it will work either way 2 3 Configurations Host refers to attributes of the system where GDB runs Target refers to the system where the program being
157. plays the results of an operation involves one or more of the following e output of the actual data e formatting the output as appropriate for console output to make it easily readable by humans e machine oriented formatting a more terse formatting to allow for easy parsing by pro grams which read GDB s output e annotation whose purpose is to help legacy GUIs to identify interesting parts in the output The ui out routines take care of the first three aspects Annotations are provided by separate annotation routines Note that use of annotations for an interface between a GUI and GDB is deprecated Chapter 4 User Interface 11 Output can be in the form of a single item which we call a field a list consisting of identical fields a tuple consisting of non identical fields or a table which is a tuple consisting of a header and a body In a BNF like form table header lt body gt lt header gt column column gt lt width gt lt alignment gt lt title gt lt body gt lt row gt 4 2 2 General Conventions Most ui_out routines are of type void the exceptions are ui_out_stream_new which returns a pointer to the newly created object and the make_cleanup routines The first parameter is always the ui_out vector object a pointer to a struct ui_out The format parameter is like in printf family of functions When it is present there must also be a variable list of arguments su
158. point float_reggroup Chapter 9 Target Architecture Definition 48 save reggroup restore reggroup all reggroup Any register with a valid name DEPRECATED REGISTER VIRTUAL SIZE reg Return the virtual size of reg defaults to the size of the register s virtual type Return the virtual size of reg See Chapter 9 Raw and Virtual Register Rep resentations page 31 DEPRECATED REGISTER VIRTUAL TYPE reg Return the virtual type of reg See Chapter 9 Raw and Virtual Register Rep resentations page 31 struct type register type gdbarch reg If defined return the type of register reg This function superseeds DEPRECATED_ REGISTER VIRTUAL TYPE See Chapter 9 Raw and Virtual Register Represen tations page 31 REGISTER CONVERT TO VIRTUAL reg type from to Convert the value of register reg from its raw form to its virtual form See Chapter 9 Raw and Virtual Register Representations page 31 REGISTER CONVERT TO RAW type reg from to Convert the value of register reg from its virtual form to its raw form See Chapter 9 Raw and Virtual Register Representations page 31 const struct regset regset from core section struct gdbarch gdbarch const char sect name size t sect size Return the appropriate register set for a core file section with name sect name and size sect size SOFTWARE SINGLE STEP P Define this as 1 if the target does not have a hardware single step mechanism The macro SOFTW
159. r do breakpoints Everything else is unnecessary for the proper operation of the debugger stub From reading the stub it s probably not obvious how breakpoints work They are simply done by deposit examine operations from GDB 10 3 ROM Monitor Interface Chapter 11 Native Debugging 58 10 4 Custom Protocols 10 5 Transport Layer 10 6 Builtin Simulator 11 Native Debugging Several files control GDB s configuration for native support gdb config arch xyz mh Specifies Makefile fragments needed by a native configuration on machine xyz In particular this lists the required native dependent object files by defining NATDEPFILES Also specifies the header file which describes native support on xyz by defining NAT_FILE nm xyz h You can also define NAT_CFLAGS NAT_ADD_FILES NAT_CLIBS NAT_CDEPS etc see Makefile in Maintainer s note The mh suffix is because this file originally contained Makefile fragments for hosting GDB on machine xyz While the file is no longer used for this purpose the mh suffix remains Perhaps someone will eventually rename these fragments so that they have a mn suffix gdb config arch nm xyz h nm h is a link to this file created by configure Contains C macro defini tions describing the native system environment such as child process control and core file support gdb xyz nat c Contains any miscellaneous C
160. rchitecture Definition 45 DEPRECATED FUNCTION START OFFSET An integer giving the offset in bytes from a function s address as used in the values of symbols function pointers etc and the function s first genuine instruction This is zero on almost all machines the function s address is usually the ad dress of its first instruction However on the VAX for example each function starts with two bytes containing a bitmask indicating which registers to save upon entry to the function The VAX call instructions check this value and save the appropriate registers automatically Thus since the offset from the function s address to its first instruction is two bytes DEPRECATED FUNCTION START OFFSET would be 2 on the VAX GCC COMPILED FLAG SYMBOL GCC2 COMPILED FLAG SYMBOL If defined these are the names of the symbols that GDB will look for to detect that GCC compiled the file The default symbols are gcc compiled and gcc2_compiled respectively Currently only defined for the Delta 68 GDB MULTI ARCH If defined and non zero enables support for multiple architectures within GDB This support can be enabled at two levels At level one only definitions for previously undefined macros are provided at level two a multi arch definition of all architecture dependent macros will be defined GDB TARGET IS HPPA This determines whether horrible kludge code in dbxread c and partial stab h is used to mangle mul
161. re in short supply GDB maintains the reference counts internally targets don t have to do anything to use this feature The x86 debug registers can each watch a region that is 1 2 or 4 bytes long The ia32 architecture requires that each watched region be appropriately aligned 2 byte region on 2 byte boundary 4 byte region on 4 byte boundary However the x86 watchpoint support in GDB can watch unaligned regions and regions larger than 4 bytes up to 16 bytes by allocating several debug registers to watch a single region This allocation of several registers per a watched region is also done automatically without target code intervention The generic x86 watchpoint support provides the following API for the GDB s application code 1386 region ok for watchpoint addr len The macro TARGET REGION OK FOR Hu WATCHPOINT is set to call this function It counts the number of debug registers required to watch a given region and returns a non zero value if that number is less than 4 the number of debug registers available to x86 processors 1386 stopped data address addr p The target function target stopped data address is set to call this function This function examines the breakpoint condition bits in the DR6 Debug Status Chapter 3 Algorithms 8 register as returned by the 1386 DR LOW GET STATUS macro and returns the address associated with the first bit that is set in DR6 1386 stopped by watchpoint void The mac
162. re encouraged people should remember that the changes only apply to a branch all commits are covered by an assignment This ensures that all changes belong to the Free Software Foundation and avoids the possibility that the branch may become contaminated a branch is focused A focused branch has a single objective or goal and does not contain unnec essary or irrelevant changes Cleanups where identified being be pushed into the mainline as soon as possible a branch tracks mainline This keeps the level of divergence under control It also keeps the pressure on developers to push cleanups and other stuff into the mainline a branch shall contain the entire GDB module The GDB module gdb should be specified when creating a branch branches of individual files should be avoided See Tags page 76 a branch shall be branded using version in The file gdb version in shall be modified so that it identifies the branch owner and branch name e g 6 2 50 20030303_owner_name or 6 2 Owner Name 15 4 2 Tags To simplify the identification of GDB branches the following branch tagging convention is strongly recommended owner name YYYYMMDD branchpoint owner name YYYYMMDD branch The branch point and corresponding branch tag YYYYMMDD is the date that the branch was created A branch is created using the sequence cvs rtag owner name YYYYMMDD branchpoint gdb cvs rtag b r owner name YYYYMMDD branchpoint N
163. rmats Other file formats that have been supported by GDB include Netware Loadable Modules nlmread c 6 5 Debugging File Formats This section describes characteristics of debugging information that are independent of the object file format Chapter 7 Language Support 25 6 5 1 stabs stabs started out as special symbols within the a out format Since then it has been encapsulated into other file formats such as COFF and ELF While dbxread c does some of the basic stab processing including for encapsulated versions stabsread c does the real work 6 5 2 COFF The basic COFF definition includes debugging information The level of support is minimal and non extensible and is not often used 6 5 3 Mips debug Third Eye ECOFF includes a definition of a special debug format The file mdebugread c implements reading for this format 6 5 4 DWARF 1 DWARF 1 is a debugging format that was originally designed to be used with ELF in SVR4 systems The DWARF 1 reader is in dwarfread c 6 5 5 DWARF 2 DWARF 2 is an improved but incompatible version of DWARF 1 The DWARF 2 reader is in dwarf2read c 6 5 6 SOM Like COFF the SOM definition includes debugging information 6 6 Adding a New Symbol Reader to GDB If you are using an existing object file format a out COFF ELF etc there is probably little to be done If you need to add a new object file format you must first add it to
164. rned This method has been deprecated in favour of gdbarch return value see dbarch return value page 50 SYMBOL RELOADING DEFAULT The default value of the symbol reloading variable Never defined in current sources TARGET CHAR BIT Number of bits in a char defaults to 8 TARGET CHAR SIGNED Non zero if char is normally signed on this architecture zero if it should be unsigned The ISO C standard requires the compiler to treat char as equivalent to either signed char or unsigned char any character in the standard execution set is supposed to be positive Most compilers treat char as signed but char is unsigned on the IBM S 390 RS6000 and PowerPC targets TARGET COMPLEX BIT Number of bits in a complex number defaults to 2 TARGET FLOAT BIT At present this macro is not used TARGET DOUBLE BIT Number of bits in a double float defaults to 8 TARGET CHAR BIT TARGET DOUBLE COMPLEX BIT Number of bits in a double complex defaults to 2 TARGET DOUBLE BIT At present this macro is not used TARGET FLOAT BIT Number of bits in a float defaults to 4 TARGET CHAR BIT TARGET INT BIT Number of bits in an integer defaults to 4 TARGET CHAR BIT TARGET LONG BIT Number of bits in a long integer defaults to 4 TARGET CHAR BIT TARGET LONG DOUBLE BIT Number of bits in a long double float defaults to 2 TARGET DOUBLE BIT TARGET LONG LONG BIT Number of bits in a long lo
165. ro STOPPED_BY_WATCHPOINT is set to call this function The argu ment passed to STOPPED_BY_WATCHPOINT is ignored This function examines the breakpoint condition bits in the DR6 Debug Status register as returned by the I386 DR LOW GET STATUS macro and returns true if any bit is set Otherwise false is returned 1386 insert watchpoint addr len type 1386 remove watchpoint addr len type Insert or remove a watchpoint The macros target insert watchpoint and target remove watchpoint are set to call these functions 1386 insert watchpoint first looks for a debug register which is already set to watch the same region for the same access types if found it just increments the reference count of that debug register thus implementing debug register sharing between watchpoints If no such register is found the function looks for a vacant de bug register sets its mirrored value to addr sets the mirrored value of DR7 Debug Control register as appropriate for the len and type parameters and then passes the new values of the debug register and DR7 to the inferior by calling I1386_DR_LOW_SET_ADDR and I386_DR_LOW_SET_CONTROL If more than one debug register is required to cover the given region the above process is repeated for each debug register i386_remove_watchpoint does the opposite it resets the address in the mir rored value of the debug register and its read write and length bits in the mirrored value of DR7 then passes these new v
166. s Given an address at which a breakpoint is desired return a breakpoint address adjusted to account for architectural constraints on breakpoint placement This method is not needed by most targets The FR V target see frv tdep c requires this method The FR V is a VLIW architecture in which a number of RISC like instructions are grouped packed together into an aggregate instruction or instruction bundle When the processor executes one of these bundles the component instructions are executed in parallel In the course of optimization the compiler may group instructions from dis tinct source statements into the same bundle The line number information associated with one of the latter statements will likely refer to some instruc tion other than the first one in the bundle So if the user attempts to place a breakpoint on one of these latter statements GDB must be careful to not place the break instruction on any instruction other than the first one in the bundle Remember though that the instructions within a bundle execute in parallel so the first instruction is the instruction at the lowest address and has nothing to do with execution order The FR V s ADJUST BREAKPOINT ADDRESS method will adjust a breakpoint s address by scanning backwards for the beginning of the bundle returning the address of the bundle Since the adjustment of a breakpoint may significantly alter a user s expecta tion GDB prints a warning when an
167. s 35 DW UAT pyte Siz oori getu ott aeiet pect endeds 35 DWARF 1 debugging info 25 DWARF 2 debugging info 25 DWARF_REG_TO_REGNUM 00 42 DWARF2_REG_TO_REGNUM 0 42 E ECOFF debugging info 25 ECOERE formats zx eere ROC RR 24 ECUFF REG TO REGNUM so aem ed 42 ELE fofi iemi ned bre odes aes 24 END F TEXT DEFAULT 2 2 n en 42 evaluate SUDEXP csse coda ad pe REEF ES 26 executable changed 0 cee essese 92 experimental branches 44 75 expression evaluation routines 26 expression parser 2 221 2eeBe dee ect Re ded 26 EXTRACT_RETURN_VALUE 0 04 43 extract typed address 34 F FDL GNU Free Documentation License 93 fetch core registers s esoose sss 59 FETCH INFERIOR REGISTERS 60 field output functions 0 00000 13 file names portability liess leeren 72 FILENAME OMP 24 22 22 nu dase adhd tam ackt leans 72 find pe funcbtion iio ise ai ates 22 find pe Vines veasegckaecns pata Rete 22 find sym fhs Et NER hea 20 finding symbol eoe mms 22 fine tuning gdbarch structure 31 FOPEN RB sia 2428 eda rm eq RET Ent eh RUCE Lied 29 EPO REGNUM ooro 252 005 hende emi dat bow dns de 60 Irae soci se duse anne Seen Rea iet iat 2 trame Chaini suae towels sobs ah ete news
168. s correct Check out the relevant modules for m in gdb insight dejagnu do mkdir p m amp amp cd m amp amp cvs q f d cvs src co P r b m done Note e The reading of cvsrc is disabled f so that there isn t any confusion between what is written here and what your local cvs really does Update relevant files gdb NEWS Major releases get their comments added as part of the mainline Minor releases should probably mention any significant bugs that were fixed Don t forget to include the ChangeLog entry emacs gdb src gdb NEWS cx 4a C X C S C X C C cp gdb src gdb NEWS insight src gdb NEWS cp gdb src gdb ChangeLog insight src gdb ChangeLog gdb README You ll need to update e the version e the update date e who did it emacs gdb src gdb README c x 4a e C S C X C C cp gdb src gdb README insight src gdb README cp gdb src gdb ChangeLog insight src gdb ChangeLog Maintainer note Hopefully the README file was reviewed before the initial branch was cut so just a simple substitute is needed to get it updated Chapter 16 Releasing GDB 82 Maintainer note Other projects generate README and INSTALL from the core documentation This might be worth pursuing gdb version in echo v gt gdb src gdb version in cat gdb src gdb version in 5 2 emacs gdb src gdb version in c x 4a Bump to version C X C S C X c c cp gdb src gdb vers
169. spaces spaces It is handy to align the text produced by ui out text with the rest of the table or list void ui out message struct ui out uiout int verbosity const char Function format This function produces a formatted message provided that the current verbosity level is at least as large as given by verbosity The current verbosity level is specified by the user with the set verbositylevel command void ui_out_wrap_hint struct ui_out uiout char indent Function This function gives the console output filter a paging filter a hint of where to break lines which are too long Ignored for all other output consumers indent if non NULL is the string to be printed to indent the wrapped text on the next line it must remain accessible until the next call to ui_out_wrap_hint or until an explicit newline is produced by one of the other functions If indent is NULL the wrapped text will not be indented void ui out flush struct ui out uiout Function This function flushes whatever output has been accumulated so far if the UI buffers output 4 2 6 Examples of Use of ui out functions This section gives some practical examples of using the ui out functions to generalize the old console oriented code in GDB The examples all come from functions defined on the preakpoints c file This example from the breakpoint_1 function shows how to produce a table The original code was As of this writi
170. stops due to a breakpoint and this breakpoint has a condition that is not met If the breakpoint has any associated commands list the commands are executed after the notification is emitted The following interfaces are available to manage observers extern struct observer observer attach event observer event _ftype Function f Using the function f create an observer that is notified when ever event occures return the observer extern void observer detach event struct observer observer Function Remove observer from the list of observers to be notified when event occurs extern void observer notify event void Function Send a notification to all event observers The following observable events are defined void normal stop struct bpstats bs Function The inferior has stopped for real void target changed struct target ops target Function The target s register contents have changed void executable changed void unused args Function The executable being debugged by GDB has changed The user decided to debug a different program or the program he was debugging has been modified since being loaded by the debugger by being recompiled for instance void inferior created struct target ops objfile int from tty Function GDB has just connected to an inferior For run GDB calls this observer while the infe rior is still stopped at the entry point instruction For attach and core GD
171. t prominent appearance of the work s title preceding the beginning of the body of the text A section Entitled XYZ means a named subunit of the Document whose title either is precisely XYZ or contains XYZ in parentheses following text that translates XYZ in another language Here XYZ stands for a specific section name mentioned below such as Acknowledgements Dedications Endorsements or History To Preserve the Title of such a section when you modify the Document means that it remains a section Entitled XYZ according to this definition The Document may include Warranty Disclaimers next to the notice which states that this License applies to the Document These Warranty Disclaimers are considered to be included by reference in this License but only as regards disclaiming warranties any other implication that these Warranty Disclaimers may have is void and has no effect on the meaning of this License Appendix B GNU Free Documentation License 95 2 VERBATIM COPYING You may copy and distribute the Document in any medium either commercially or noncommercially provided that this License the copyright notices and the license notice saying this License applies to the Document are reproduced in all copies and that you add no other conditions 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 distr
172. ted into infptrace c infptrace c can deal with variations between systems the same way any system independent file would hooks if defined etc and machines which are radically different don t need to use infptrace c at all All debugging code must be controllable using the set debug module command Do not use printf to print trace messages Use fprintf_unfiltered gdb_stdlog Do not use ifdef DEBUG 14 Porting GDB Most of the work in making GDB compile on a new machine is in specifying the configu ration of the machine This is done in a dizzying variety of header files and configuration scripts which we hope to make more sensible soon Let s say your new host is called an xyz e g sun4 and its full three part configuration name is arch xvend xos e g sparc sun sunos4 In particular e In the top level directory edit config sub and add arch xvend and xos to the lists of supported architectures vendors and operating systems near the bottom of the file Also add xyz as an alias that maps to arch xvend xos You can test your changes by running config sub xyz and config sub arch xvend xos which should both respond with arch xvend xos and no error messages You need to port BFD if that hasn t been done already Porting BFD is beyond the scope of this manual e To configure GDB itself edit gdb configure host to recognize your system and set gdb_host to xyz and unless
173. ter able to support graphical and other environments Since libgdb development is on going its architecture is still evolving The following components have so far been identified e Observer gdb events h e Builder ui out h e Event Loop event loop h e Library gdb h The model that ties these components together is described below 5 3 The libgdb Model A client of libgdb interacts with the library in two ways e Asan observer using gdb events receiving notifications from libgdb of any internal state changes break point changes run state etc e Asaclient querying libgdb using the ui out builder to obtain various status values from GDB Since libgdb could have multiple clients e g a GUI supporting the existing GDB CLI those clients must co operate when controlling libgdb In particular a client must ensure that libgdb is idle i e no other client is using libgdb before responding to a gdb event by making a query 5 4 CLI support At present GDB s CLI is very much entangled in with the core of libgdb Consequently a client wishing to include the CLI in their interface needs to carefully co ordinate its own and the CLI s requirements It is suggested that the client set libgdb up to be bi modal alternate between CLI and client query modes The notes below sketch out the theory e The client registers itself as an observer of libgdb e The client create and install cl
174. the Document s overall subject or to related matters and contains nothing that could fall directly within that overall subject Thus if the Document is in part a textbook of mathematics a Secondary Section may not explain any mathematics The relationship could be a matter of historical connection with the subject or with related Appendix B GNU Free Documentation License 94 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 released under this License If a section does not fit the above definition of Secondary then it is not allowed to be designated as Invariant The Document may contain zero Invariant Sections If the Document does not identify any Invariant Sections then there are none 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 Front Cover Text may be at most 5 words and a Back Cover Text may be at most 25 words A Transparent copy of the Document means a machine readable copy represented in a format whose specification is available to the general public that is suitable for revising the document straightforwardly with generic text editors or for images com posed of pix
175. ti arch This section describes the current accepted best practice for converting an existing target architecture to the multi arch framework The process consists of generating testing posting and committing a sequence of patches Each patch must contain a single change for instance e Directly convert a group of functions into macros the conversion does not change the behavior of any of the functions e Replace a non multi arch with a multi arch mechanism e g FRAME INFO e Enable multi arch level one e Delete one or more files There isn t a size limit on a patch however a developer is strongly encouraged to keep the patch size down Since each patch is well defined and since each change has been tested and shows no regressions the patches are considered fairly obvious Such patches when submitted by developers listed in the MAINTAINERS file do not need approval Occasional steps in the process may be more complicated and less clear The developer is expected to use their judgment and is encouraged to seek advice as needed 9 12 1 Preparation The first step is to establish control Build with Werror enabled and test the target so that there is a baseline against which the debugger can be compared At no stage can the test results regress or GDB stop compiling with Werror 9 12 2 Add the multi arch initialization code The objective of this step is to establish the basic multi arch framework It i
176. tinue the inferior after a watchpoint has been hit CANNOT STEP HV WATCHPOINTS If this is defined to a non zero value GDB will remove all watchpoints before stepping the inferior STOPPED BY WATCHPOINT wait status Return non zero if stopped by a watchpoint wait status is of the type struct target waitstatus defined by target h Normally this macro is defined to invoke the function pointed to by the to stopped by watchpoint member of the structure of the type target ops defined on target h that describes the target specific operations to stopped by watchpoint ignores the wait status argument GDB does not require the non zero value returned by STOPPED BY WATCHPOINT to be 10096 correct so if a target cannot determine for sure whether the inferior stopped due to a watchpoint it could return non zero just in case 3 8 1 x86 Watchpoints The 32 bit Intel x86 a k a ia32 processors feature special debug registers designed to facilitate debugging GDB provides a generic library of functions that x86 based ports can use to implement support for watchpoints and hardware assisted breakpoints This subsection documents the x86 watchpoint facilities in GDB To use the generic x86 watchpoint support a port should do the following e Define the macro I386 USE GENERIC WATCHPOINTS somewhere in the target dependent headers Chapter 3 Algorithms 7 e Include the config i386 nm i386 h header file after
177. tion of the generic observer provides support for contextual data This contextual data is given to the subject when attaching the callback In return the subject will provide this contextual data back to the observer as a parameter of the callback Note that the current support for the contextual data is only partial as it lacks a mechanism that would deallocate this data when the callback is detached This is not a problem so far as this contextual data is only used internally to hold a function pointer Later on if a certain observer needs to provide support for user level contextual data then the generic notification mechanism will need to be enhanced to allow the observer to provide a routine to deallocate the data when attaching the callback Appendix A GDB Currently available observers 92 The observer implementation is also currently not reentrant In particular it is therefore not possible to call the attach or detach routines during a notification A 2 Debugging Observer notifications can be traced using the command set debug observer 1 see sec tion Optional messages about internal happenings in Debugging with GDBN A 3 normal stop Notifications GDB notifies all normal stop observers when the inferior execution has just stopped the associated messages and annotations have been printed and the control is about to be returned to the user Note that the normal stop notification is not emitted when the execution
178. tiple symbol table files from HPPA s This should all be ripped out and a scheme like elfread c used instead GET_LONGJMP_TARGET For most machines this is a target dependent parameter On the DECsta tion and the Iris this is a native dependent parameter since the header file setjmp h is needed to define it This macro determines the target PC address that longjmp will jump to assum ing that we have just stopped at a longjmp breakpoint It takes a CORE ADDR as argument and stores the target PC value through this pointer It examines the current state of the machine as needed DEPRECATED GET SAVED REGISTER Define this if you need to supply your own definition for the function DEPRECATED GET SAVED REGISTER DEPRECATED IBM6000 TARGET Shows that we are configured for an IBM RS 6000 system This conditional should be eliminated FIXME and replaced by feature specific macros It was introduced in a haste and we are repenting at leisure I386 USE GENERIC WATCHPOINTS An x86 based target can define this to use the generic x86 watchpoint support see Chapter 3 Algorithms page 2 Chapter 9 Target Architecture Definition 46 SYMBOLS CAN START WITH DOLLAR Some systems have routines whose names start with Giving this macro a non zero value tells GDB s expression parser to check for such routines when parsing tokens that begin with On HP UX certain system routines millicode have names beginni
179. to the chain but not yet discarded or performed E g make cleanup a 0 1 struct cleanup old make cleanup b 0 make cleanup c 0 do cleanups old Chapter 13 Coding 65 will call c and bO but will not call aO The cleanup that calls aC will remain in the cleanup chain and will be done later unless otherwise discarded Your function should explicitly do or discard the cleanups it creates Failing to do this leads to non deterministic behavior since the caller will arbitrarily do or discard your functions cleanups This need leads to two common cleanup styles The first style is try finally Before it exits your code block calls do cleanups with the old cleanup chain and thus ensures that your code block s cleanups are always performed For instance the following code segment avoids a memory leak problem even when error is called and a forced stack unwind occurs by ensuring that the x ree will always be called struct cleanup old make cleanup null cleanup 0 data xmalloc sizeof blah make cleanup xfree data blah blah do cleanups old The second style is try except Before it exits your code block calls discard cleanups with the old cleanup chain and thus ensures that any created cleanups are not performed For instance the following code segment ensures that the file will be closed but only if there is an error FILE file fopen afile r struct cleanup old make cl
180. topics that are lower level than the major algorithms of GDB 13 1 Cleanups Cleanups are a structured way to deal with things that need to be done later When your code does something e g xmalloc some memory or open a file that needs to be undone later e g xfree the memory or close the file it can make a cleanup The cleanup will be done at some future point when the command is finished and control returns to the top level when an error occurs and the stack is unwound or when your code decides it s time to explicitly perform cleanups Alternatively you can elect to discard the cleanups you created Syntax struct cleanup old chain Declare a variable which will hold a cleanup chain handle old chain make cleanup function arg Make a cleanup which will cause function to be called with arg a char later The result old_chain is a handle that can later be passed to do cleanups or discard cleanups Unless you are going to call do cleanups or discard cleanups you can ignore the result from make cleanup do cleanups old chain Do all cleanups added to the chain since the corresponding make cleanup call was made discard cleanups old chain Same as do cleanups except that it just removes the cleanups from the chain and does not call the specified functions Cleanups are implemented as a chain The handle returned by make cleanups includes the cleanup passed to the call and any later cleanups appended
181. ts You should not use REGISTER CONVERT TO VIRTUAL for a register unless this macro returns a non zero value for that register int DEPRECATED REGISTER RAW SIZE int reg Target Macro The size of register number reg s raw value This is the number of bytes the register will occupy in registers or in a GDB remote protocol packet int DEPRECATED REGISTER VIRTUAL SIZE int reg Target Macro The size of register number reg s value in its virtual format This is the size a struct value s buffer will have holding that register s value struct type DEPRECATED REGISTER VIRTUAL TYPE int Target Macro reg This is the type of the virtual representation of register number reg Note that there is no need for a macro giving a type for the register s raw form once the register s value has been obtained GDB always uses the virtual form void REGISTER CONVERT TO VIRTUAL int reg struct type type Target Macro char from char to Convert the value of register number reg to type which should always be DEPRECATED_ REGISTER VIRTUAL TYPE reg The buffer at from holds the register s value in raw format the macro should convert the value to virtual format and place it at to Note that REGISTER CONVERT TO VIRTUAL and REGISTER CONVERT TO RAW take their reg and type arguments in different orders You should only use REGISTER CONVERT TO VIRTUAL with registers for which the REGISTER CONVERTIBLE macro returns a non zero value
182. two macros should return 0 for success non zero for failure O Common write HW watchpoint 1 Read HW watchpoint 2 Access read or write HW watchpoint 3 Execute HW breakpoint Chapter 3 Algorithms 6 target remove hw breakpoint addr shadow target insert hw breakpoint addr shadow Insert or remove a hardware assisted breakpoint at address addr Returns zero for success non zero for failure shadow is the real contents of the byte where the breakpoint has been inserted it is generally not valid when hardware break points are used but since no other code touches these values the implementa tions of the above two macros can use them for their internal purposes target stopped data address addr p If the inferior has some watchpoint that triggered place the address associated with the watchpoint at the location pointed to by addr_p and return non zero Otherwise return zero Note that this primitive is used by GDB only on targets that support data read or data access type watchpoints so targets that have support only for data write watchpoints need not implement these primitives HAVE STEPPABLE WATCHPOINT If defined to a non zero value it is not necessary to disable a watchpoint to step over it HAVE NONSTEPPABLE WATCHPOINT If defined to a non zero value GDB should disable a watchpoint to step the inferior over it HAVE CONTINUABLE WATCHPOINT If defined to a non zero value it is possible to con
183. ves to support hardware watchpoints TARGET HAS HARDWARE WATCHPOINTS If defined the target supports hardware watchpoints TARGET CAN USE HARDWARE WATCHPOINT type count other Return the number of hardware watchpoints of type type that are possible to be set The value is positive if count watchpoints of this type can be set zero if setting watchpoints of this type is not supported and negative if count is more than the maximum number of watchpoints of type type that can be set other is non zero if other types of watchpoints are currently enabled there are architectures which cannot set watchpoints of different types at the same time TARGET REGION OK FOR HW WATCHPOINT addr len Return non zero if hardware watchpoints can be used to watch a region whose address is addr and whose length in bytes is len TARGET REGION SIZE OK FOR HW WATCHPOINT size Return non zero if hardware watchpoints can be used to watch a region whose size is size GDB only uses this macro as a fall back in case TARGET REGION OK FOR HV WATCHPOINT is not defined target insert watchpoint addr len type target remove watchpoint addr len type Insert or remove a hardware watchpoint starting at addr for len bytes type is the watchpoint type one of the possible values of the enumerated data type target hw bp type defined by breakpoint h as follows enum target hw bp type 1 hw write hw read hw access hw execute F These
184. ws based ports Chapter 14 Porting GDB 73 In addition to using these macros be sure to use portable library functions whenever possible For example to extract a directory or a basename part from a file name use the dirname and basename library functions available in libiberty for platforms which don t provide them instead of searching for a slash with strrchr Another way to generalize GDB along a particular interface is with an attribute struct For example GDB has been generalized to handle multiple kinds of remote interfaces not by ifdefs everywhere but by defining the target ops structure and having a current target as well as a stack of targets below it for memory references Whenever something needs to be done that depends on which remote interface we are using a flag in the current target ops structure is tested e g target has stack or a function is called through a pointer in the current target ops structure In this way when a new remote interface is added only one module needs to be touched the one that actually implements the new remote interface Other examples of attribute structs are BFD access to multiple kinds of object file formats or GDB s access to multiple source languages Please avoid duplicating code For example in GDB 3 x all the code interfacing between ptrace and the rest of GDB was duplicated in dep c and so changing something was very painful In GDB 4 x these have all been consolida
185. xp This test script does not work on a remote host 17 2 Testsuite Organization The testsuite is entirely contained in gdb testsuite While the testsuite includes some makefiles and configury these are very minimal and used for little besides cleaning up since the tests themselves handle the compilation of the programs that GDB will run The file testsuite lib gdb exp contains common utility procs useful for all GDB tests while the directory testsuite config contains configuration specific files typically used for special purpose definitions of procs like gdb_load and gdb_start The tests themselves are to be found in testsuite gdb and subdirectories of those The names of the test files must always end with exp DejaGNU collects the test files by wildcarding in the test directories so both subdirectories and individual files get chosen and run in alphabetical order The following table lists the main types of subdirectories and what they are for Since DejaGNU finds test files no matter where they are located and since each test file sets up its own compilation and execution environment this organization is simply for convenience and intelligibility gdb base This is the base testsuite The tests in it should apply to all configurations of GDB but generic native only tests may live here The test programs should be in the subset of C that is valid K amp R ANSI ISO and C ifdefs are allowed
186. y 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 License 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 Appendix B Index 99 B 1 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 title page Copyright C year your name Permission is granted to copy distribute and or modify this document under the terms of the GNU Free Documentation License Version 1 2 or any later version published by the Free Software Foundation with no Invariant Sections no Front Cover Texts and no Back Cover Texts Free Documentation License A copy of the license is included in the section entitled GNU If you have Invariant Sections Front Cover Texts and Back Cover Texts replace the with Texts line with this with the Invariant Sections being list t
187. your desired target is already available also edit gdb configure tgt setting gdb_target to something appropriate for instance xyz Chapter 15 Versions and Branches 74 Maintainer s note Work in progress The file gdb configure host originally needed to be modified when either a new native target or a new host machine was being added to GDB Recent changes have removed this requirement The file now only needs to be modified when adding a new native configuration This will likely changed again in the future e Finally you ll need to specify and define GDB s host native and target dependent h and c files used for your configuration 15 Versions and Branches 15 1 Versions GDB s version is determined by the file gdb version in and takes one of the following forms major minor major minor patchlevel an official release e g 6 2 or 6 2 1 major minor patchlevel Y Y Y Y MM DD a snapshot taken at YYYY MM DD gmt e g 6 1 50 20020302 6 1 90 20020304 or 6 1 0 20020308 major minor patchlevel Y Y Y Y MM DD cvs a cvs check out drawn on YYYY MM DD e g 60 1 50 20020302 cvs 6 1 90 20020304 cvs or 6 1 0 20020308 cvs major minor patchlevel Y YY Y MM DD vendor a vendor specific release of GDB that while based on major minor patchlevel Y Y Y Y MM DD may include additional changes GDB s mainline uses the major and minor version numbers from the most recent release branch with a p
188. ype flags ptr should be one of TYPE FLAG ADDRESS CLASS 1 TYPE FLAG ADDRESS CLASS 2 or possibly some combination of these values or d together See Chapter 9 Address Classes page 31 ADDRESS CLASS NAME TO TYPE FLAGS P Predicate which indicates whether ADDRESS CLASS NAME TO TYPE FLAGS has been defined ADDRESS CLASS TYPE FLAGS byte size dwarf2 addr class Given a pointers byte size as described by the debug information and the possi ble DW AT address class value return the type flags used by GDB to represent this address class The value returned should be one of TYPE FLAG ADDRESS CLASS 1 TYPE FLAG ADDRESS CLASS 2 or possibly some combination of these values or d together See Chapter 9 Address Classes page 31 ADDRESS CLASS TYPE FLAGS P Predicate which indicates whether ADDRESS CLASS TYPE FLAGS has been de fined ADDRESS CLASS TYPE FLAGS TO NAME type flags Return the name of the address class qualifier associated with the type flags given by type flags ADDRESS CLASS TYPE FLAGS TO NAME P Predicate which indicates whether ADDRESS CLASS TYPE FLAGS TO NAME has been defined See Chapter 9 Address Classes page 31 Chapter 9 Target Architecture Definition 40 ADDRESS TO POINTER type buf addr Store in buf a pointer of type type representing the address addr in the ap propriate format for the current architecture This macro may safely assume that type

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