Re: Function Instrumentation

[Venetis Ioannis <venetis at ceid dot upatras dot gr>]

>   I noticed the "-finstrument-functions" flag, and I was wondering if
it's
> currently working (on Linux x86 platforms).  Test programs I compile
(with
> dummy __cyg_profile_func_enter/exit routines) pretty much always seem to
> core dump.  Is there somewhere I could get more information?
>   Thanks a lot!
> --John Zedlewski

This is because you have the __cyg_profile_func_enter() and
__cyg_profile_func_exit() functions in the same source file with other
functions of your program. When you compile the source with the
-finstrument-functions flag these 2 functions will be also instrumented,
which means that they will be called recursevily and you will get a stack
overflow and of course a core. You have 2 options to solve this :

1) Put these 2 functions in a seperate source file, compile this file
   without the -finstrument-functions flag and link together all the
   object files.

2) A better way is to declare these 2 functions like this :

void  __attribute__((__no_instrument_function__))
__cyg_profile_func_enter(void *this_fn, void *call_site)
{
 printf("func_enter() : this_fn = %p, call_site = %p\n",
 this_fn, call_site);
} 

and:

void __attribute__((__no_instrument_function__))
__cyg_profile_func_exit(void *this_fn, void *call_site)
{
 printf("func_exit()  : this_fn = %p, call_site = %p\n",
 this_fn, call_site);
} 

gcc will not create calls to the instrumentation functions for all the
functions which have the no_instrument_function attribute. With this, you
can leave the profiling functions in the same source file with all other
functions you have.

Hope this helps.

Ioannis E. Venetis