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1. manager thread New Thread 31075 initial thread New Thread 31077 Switching to Thread 31077 Opened Program received signal SIGINT Interrupt OxAOIVeeCil im Lide incwarcysilersye O From Iiloy lioe sion gdb d6Quit gdb break myfn Breakpoint 1 at 0x40071llcb file testload cpp line 52 gdb p globalvar S1 1 gdb p mypoint 2 sfPoint 0x0 gdb c Continuing Switching to Thread 31075 initial thread Program received signal SIGINT Interrupt Cx40L7eeCGiL im _ libe naneslesp O from lib Mile So 6 gdb c Continuing Figure 4 1 Listing from a running GDB debugging session can look at its value and check that the object has the correct position 1000 0 0 Variables and objects can also have their values set by GDB commands Saphira Tutorial on Loadable Files Switching to Thread 31077 Breakpoint 1 myfn a 1000 at testload 11 GIs DZ warning Source file is more recent than executable 52 Current language auto currently c gdb bt 0 myfn a 1000 at testload cpp 52 1 0x4003c59a in eval fexpr e 0x805bd68 at src control expr c 1450 2 0x40037ea7 in do eval e 0x805bd68 at egi y 829 3 0x40039d58 in yyparse at egi y 2144 4 0x4003776b in parse command at egi y 510 5 0x4003437d in run process p 0x40064848 at src basic process c 603 6 0x40034404 in run all processes at src basic process c 629 7 0x4004842. prints the message Opened 1 using the sfMessage call Unloading the shared object file can be accomplished with the unload command Generally under UNIX systems there s no need to explicitly unload a file since re loading the same file will cause an automatic unload first The unload command is mainly a convenience for MS Windows systems where a shared object file cannot be recompiled if it is in use If there is an error in your shared object code you can make changes recompile and relink the code and then reload it using the load command again The new function definitions will replace the old ones One possible problem with this process is that the Saphira client may be invoking some functions of the shared object usually in a microtask Reloading does not update function or other pointers into the original loaded object that may exist The microtask must be exited before the reload operation is performed since otherwise it will try to execute nonexistent function code as the original loaded object code is unloaded automatically One consequence of reloading is that the previous values of any global variables in the shared object file are lost and the variable is reset to its initialization value For example the variable nopen is always initialized to 0 when testload so is loaded Even though it is incremented by the call to sfLoadInit it gets reset to its initialization value whenever test load so is reloaded and so never increments a
3. flag You must include this variable defined in os h for each particular OS in order to create a shared object file Makefile for the loadable tutorial SRCD OBUD gt INCD ohandler include BIND bin IIPS og ff 5 5 lie INRIUND EE AN check which OS we have include INCD os h SHELL bin sh INCLUDE IS INCD IS ARIAD include AT AT TG TG GT EH TE HHH HH all LIBD testload so touch all OBJD testload o SRCD testload cpp CC CFLAGS c SRCD testload cpp INCLUDE o OBJD testload o LIBD testload so 0BJD testload o LD SHARED o LIBD testload so OBJD testload o Figure 3 1 Makefile for the testload cpp program Saphira Tutorial on Loadable Files 8 3 1 Loading Shared Objects into a Saphira Client Shared object files with extensions ending in so can be loaded into a Saphira client using the Colbert interaction window The loadlib command will attempt to load a shared object file using the current directory first and then the default directories which always include SAPHIRA lib To load the example testload so use the following command loadlib testload Note that the extension so isn t necessary in specifying the file for the Loadlib command The loadlib command if successful prints out the name of the file loaded and then declares whether it found an sfLoadInit function to evaluate In this case when sfLoadInit is evaluated it
4. 6c in update and comm at src basic toplevel c 779 8 0x400482a6 in sfDoToplevel at src basic toplevel c 652 9 O0x40047beb in doact signum 0 at src basic toplevel c 213 10 0x40047c15 in dotop a 0x0 at src basic toplevel c 233 11 0x4007db85 in pthread start thread arg 0xbf7ffe40 at manager c 241 gdb n 53 sfSMessage Argument to myfn is d a gdb n 81 p x x p y yy p th th type sfPOINT gdb n 54 mypoint new sfPoint a 0 0 gdb n 55 return a 2 gdb p mypoint S9 SEP On Oe lt cObbded gdb p mypoint 4 lt sfArtifact gt lt sfDrawable gt visible 1 color 0 vptr 0x40058280 p lt sfPosition gt x 1000 y 0 th 0 type 1 id 0 newflags 1 static newid 1 lt No data fields gt gdb Figure 4 2 Breakpoint execution from GDB
5. SAPHIRA TUTORIAL Compiling Loading and Debugging C Files Unix Systems Software version 8 0 Saphira Aria September 2001 OKurt Konolige SRI International konolige Qai sri com http www ai sri com konolige Saphira Tutorial on Loadable Files 1 Introduction 2 Shared Object Files under UNIX 2 1 Compiling and Linking C C Source Files 2 2 Writing C or C Client Programs 3 Compiling and Linking Client Programs under UNIX 3 1 Loading Shared Objects into a Saphira Client 3 2 Initializations on Loading 4 Debugging C Code under UNIX 4 1 Setting a Breakpoint 4 2 Debugging from a Breakpoint Coo wm mY BR KRO Saphira Tutorial on Loadable Files 3 1 Introduction This tutorial introduces loadable object files as a means of extending the functionality of Saphira A simple example of such a file compiled from C code is given The source and makefile for the sample object file can be found in the Saphira tutor loadable directory Saphira Tutorial on Loadable Files 4 2 Shared Object Files under UNIX Most UNIX systems allow object files to be dynamically loaded into a running program using the d1 functions dlopen dlsym dlclose Object files can be compiled from any source but usually come from C or C programs A special linking operation on these object files creates shareable object files which contain information that allows them to be loaded into an executing program Typically they will have the suffix so Saph
6. are a common parent directory The ohandler include directory contains header files and ohandler lib has the Saphira libraries and is where compiled shared objects typically are deposited Next the file handler include os h is read in This file determines the operating system type and sets some system library variables appropriately NOTE os h also sets the CONFIG variable to the particular OS of the machine which is important for handling some of the system routines correctly One peculiarity of os h is that it relies on the conditional preprocessing facilities of gnu make gmake Not all native makes support this facility If you get errors during the preprocessing phase of the compilation from os h switch to gmake The makefile produces the file testload so in the Saphira library directory S SAPHIRA lib testload so is a shared object file which is loadable under Colbert The C source is compiled as usual make sure the g flag is present so that debugging symbols are added to the object file Under some UNIXes the source must be compiled as position independent PIC in order to create a shared object file This detail is handled by the PICFLAG variable set by os h Next the LD command is invoked to create a shared object file with the extension so Saphira expects this extension for UNIX shareable objects and cannot load objects with any other extensions The most critical part of the linking operation is the inclusion of the SHARED
7. bove I Within the Colbert interaction window several functions and variables from the shared object file are made available Evaluating myfn for example will set up a new point artifact and then return its argument plus 2 3 2 Initializations on Loading There is one peculiarity of shared object files that are dynamically loaded Unlike other object files variables which are declared globally initialized may not be initialized when the file is loaded For example the following line in the test load cpp example initialized a global variable int globalvar 1 The variable globalvar may not be set to 1 upon loading the resultant shared object file In fact under the Linux system it typically is under MS Windows it isn t The only way to initialize variables securely is with the sfLoadInit function Saphira Tutorial on Loadable Files 9 4 Debugging C Code under UNIX The Colbert interaction window is a handy facility for debugging clients because you can query the values of variables start and stop activities and so on Often it may be necessary to invoke a more heavy duty debugging apparatus especially for complicated C programs The Gnu debugger gdb can be useful especially when started in Emacs Here are a few tips for interacting with the Gnu debugger To start up give gdb the name of the client executable usually saphira At the debugger prompt type run to start the client Before running the program the Saphira libra
8. e file available to the Colbert evaluator through use of sfAddEvalXXX function calls For information on the effect of these calls see the Colbert User s Manual The sfLoadExit function is called when the file is unloaded and typically cleans up by getting rid of micro tasks that are invoked by the file etc These functions have the keyword SFEXPORT as part of their definition For UNIX this keyword is defined as the empty string and doesn t affect the compilation or loading process It s necessary under MS Windows however and it s good practice to include it so that your code will compile and run under either OS Saphira Tutorial on Loadable Files 5 include Saphira h global integer variables on some systems these will not be initialized on load int nopen 0 int globalvar 1 string variable char buf 80 char mystring we need to set aside space explicitly for a string ptr C global functions Set up functions to create and manipulate a point artifact This point will draw on the screen SfPoint mypoint int sets up a point artifact myfn int a sfMessage Argument to myfn is d a mypoint new SfPoint a 0 0 return a 2 void prints values of a point artifact ea aes 210 SfPoint pt SfPoint p sfMessage Point x d y d th d int pt gt p getX int pt gt p getY int pt gt p getTh void sets the X and Y values of a point
9. ira takes advantage of the dynamic load facility under UNIX Users can write C C programs that are then compiled into shared object files These object files can be loaded into a running Saphira client and the functions in them made available through the Colbert interface In this way the user can extend Saphira with new functions written in C C As of Saphira 8 x the Saphira library is written as a set of classes in C and is built on top of the Aria system from ActivMedia Robotics User programs access basic Saphira and Aria services through these classes User programs can also be written a mixture of C and C using standard interfacing between the languages Because of limitations in the syntax and semantics of Colbert it is not possible to express interfaces to C objects or their member functions directly Instead users must write C or C global functions accessing the C objects and then make these functions available for calling from Colbert The objects themselves can be passed around as NULL pointers within C programs and Colbert 2 1 Compiling and Linking C C Source Files To compile a loadable shared object file you must have installed the Saphira and Aria distributions according to the directions in the readme file In particular the environment variables SAPHIRA and ARIA must be set to the top levels of their respective distributions In addition Saphira and Aria distributions should be set up as subdirectories of a co
10. mmon directory After installing the Saphira distribution follow these steps to create a client or a shared object file 1 Write a C C program containing your code including calls to Saphira library functions Compile the program to produce an object file 3 Link the object file together with the relevant Saphira library to create an executable or shared object file In Saphira 8 x all the Saphira library routines are contained in a shared library In UNIX systems it is the shared library 1ibsf so Aria routines are also accessed through a shared library LibAria so 2 2 Writing C or C Client Programs To load new C C routines into Colbert you write one or more C C programs that contain your own functions and make calls to the Saphira library routines It may help to review Chapter 2 of the Saphira manual for an explanation of micro tasks and asynchronous user routines Note that there are very few remaining Saphira functions that are C functions and all Aria functions are written in C So user programs will generally have at least on C file to access the Saphira Aria libraries Figure 2 1 and Figure 2 2 show the C source code for the sample tutor loadable testload cpp example The header file Saphira h must be included at the beginning of the source file The rest of the file contains C and C function and variable definitions The sfLoadInit function is called after loading the file and it typically makes the objects in th
11. pawned Saphira itself uses one main thread to control its 100 ms main cycle At this point in the Saphira client window testload so is loaded The printf statement in sfInitLoad prints the Opened line on the GDB console 4 1 Setting a Breakpoint Since our user program is now loaded we can set a breakpoint First the Saphira client is interrupted by pressing Ctrl C in the GDB window actually you need two consecutive Ctrl C s in the Emacs GDB window A breakpoint is inserted at the myfn function It s also possible to scout around and check the values of variables for example the value of globalvar A subtle aspect of GDB is how it handles shared libraries and their symbols In this version of GDB under Linux shared object file symbols are automatically made available in the debugger The sharedlibrary command prints info about all shared libraries known by the debugger here all of the symbols in these files are loaded Under some OSes such as Solaris the symbols of shared object files are not automatically loaded into GDB when the shared object is dynamically loaded In this case you must interrupt the debugger with Ctrl C and issue the command sharedlibrary testload so to make its symbols visible to the debugger To continue from the break use the c command sometimes this has to be issued twice to continue apparently because of GDB s handling of threads 4 2 Debugging from a Breakpoint Continuing from the break
12. ries libsf so aren t loaded so you can t set breakpoints in Saphira functions Similarly user shared object files aren t yet present After the client is running and you have loaded any shared object files into Colbert you can set breakpoints by interrupting back to the debugger prompt All of the Saphira library exported functions and variables can be examined and you can set breakpoints in the library functions The Saphira library has been compiled with the g option so its symbols are available to the debugger However not all the source code is not in the distribution so you may not be able to step through library functions Figure 4 1 shows typical output from the GDB debugger GDB is started by giving it the Saphira executable bin saphira Next Saphira itself is started with the run command At this point the Saphira client doesn t even have a window system available so it prints out messages on the console First it finds its home directory using the SAPHIRA environment variable and sets up the Colbert directory path from that Then it reads the activity file startup act from the Colbert directory You can change startup act to have any initial behavior you want but the default file loads the windowing system fltk so and fltkwin so after which messages will print on the Colbert window The rest of startup act loads some basic activities for the robot and then Saphira continues with its main loop and several threads are s
13. setpoint void p int x int y SfPoint pt SfPoint p pt gt p setX double x pt gt p setY double y sfMessage Point x d y d th d int pt gt p getX int pt gt p getY int pt gt p getTh Figure 2 1 Listing of the testload cpp program part one of two Saphira Tutorial on Loadable Files 6 He C global functions Set up an interface to the sonar buffers Md int get sonar dist int begang int endang int retang SfSonarDevice sd Sf sonar get the device if sd return 100000 large value no return double ret ArPose rpose SfROBOT gt getPose Aria occupancy function on the sonar current reading buffer double fdist sd gt getCurrent gt getClosestPolar double begang double endang rpose 100000 amp ret if retang miaeiveias EENES return int fdist sfLoadInit and sfLoadExit must be declared as exported fns under MS Windows SFEXPORT void sfLoadInit void this function is evaluated when the object file is loaded sfMessage Opened d nopen on open we should get a message printf Opened n let the console know too define constants and variables sfAddEvalConst SsfLEFT sfINT 0 sfAddEvalVar gv sfINT fvalue amp globalvar note indirection in the last argument sfAddEvalVar mypoint sfPTR fvalue amp mypoint note indirection in the last argument mystring buf se
14. t up string ptr mystring 0 A mysen abl Op sfAddEvalVar mystring sfSTRING fvalue amp mystring note the indirection in the last argument define functions any C global functions will give an error here if overloaded sfAddEvalFn myfn void myfn sfINT 1 sfINT sfAddEvalFn showpoint void showpoint sfVOID 1 sfPTR sfAddEvalFn setpoint void setpoint sfVOID 3 sfPTR sfINT sfINT sfAddEvalFn get sonar dist void get sonar dist sfINT 3 sfINT sfINT sfTypeRef sfINT last arg is pointer to int SFEXPORT void sfLoadExit void this should be evaluated on unload sfMessage Unloading d nopen Figure 2 2 Listing of the testload cpp program part two of two Saphira Tutorial on Loadable Files 7 3 Compiling and Linking Client Programs under UNIX After the client programs are written they must be compiled with a C or C compiler We recommend the gcc compiler for UNIX systems all sample programs have been compiled using this compiler Other C compilers provided with UNIX systems should also work however The compiler and linker are typically called using the make facility The file makefile in the Saphira tutor loadable directory is used to make the testload cpp program Figure 3 1 shows this makefile The first part of the makefile defines variables that are useful in compilation and linking Note that the Saphira and Aria top level directories have to sh
15. the user then evaluates myfn 1000 in the Colbert interaction window This interrupts the debugger and now the user can examine the stack change data values and so on debugging this function Figure 4 2 To find out where the breakpoint function is being called from issue the command bt backtrace This prints out the function call stack from the most recently called function Anything below the call to eval_fexpr is internal to Saphira and the Colbert interpreter and not particularly useful One nice feature of GDB is the ability to step through lines of your code Under Emacs a second buffer will open showing the position of the program counter in your source code Here we step through and GDB prints out each line as it is executed After the variable mypoint is set to an object pointer we Saphira Tutorial on Loadable Files 10 konolige dill saphira gdb bin saphira NU gdb 19991004 opyright 1998 Free Software Foundation Inc OQ Gr gdb run Starting program home konolige saphira bin saphira SIEVE ge SAPHIRA directory is home konolige saphira Started basic processes Load directory is home konolige saphira colbert Loading file home konolige saphira colbert startup act Loading shared object file home konolige saphira colbert lib fltk so No initializer Eval to void Loading shared object file home konolige saphira colbert lib fltkwin so Evaluating sfLoadInit Starting main frame New Thread 31076
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