How to use '-finstrument-functions' in C++ programs ?

[Perret Yannick]

Hello,

I can see the same behavior with gcc 3.4.1.

At least an obvious way to prevent that problem is
to extract the __cyg_profile_func* stuff into a separated
source file that is compiled in C.
This object is then linked at the end with the C++ -compiled
objects you can have to build the final binary.
It works at least for my gcc 3.4.1.

You can also tell g++ that this part of the code is C by adding

extern "C"
{
/* the __cyg_profile_func... functions */

}

Also tested with 3.4.1.

Regards,
--
Yannick Perret


Dmitry Antipov wrote:

> (This letter was being previously posted to gcc-help list, which is 
> probably the
> better place to ask such questions. But since it wasn't answered 
> there, I posted it here).
>
> The following program
>
> #include <stdio.h>
>
> void __cyg_profile_func_enter (void *, void *) 
> __attribute__((no_instrument_function));
> void __cyg_profile_func_exit (void *, void *) 
> __attribute__((no_instrument_function));
>
> int depth = -1;
>
> void __cyg_profile_func_enter (void *func,  void *caller)
> {
>  int n;
>
>  depth++;
>  for (n = 0; n < depth; n++)
>    printf (" ");
>  printf ("-> %p\n", func);
> }
>
> void __cyg_profile_func_exit (void *func, void *caller)
> {
>  int n;
>
>  for (n = 0; n < depth; n++)
>    printf (" ");
>  printf ("<- %p\n", func);
>  depth--;
> }
>
> void bar(void)
> {
> }
>
> void foo (void)
> {
>  int x;
>  for (x = 0; x < 4; x++)
>    bar ();
> }
>
> int main (int argc, char *argv[])
> {
>  foo ();
>  bar ();
>  return 0;
> }
>
> works as expected if it's compiled as a C program ('gcc 
> -finstrument-functions self.c').
> But __cyg_* functions doesn't called if the program is compiled as C++ 
> program
> ('g++ -finstrument-fnctions self.cpp').
>
> Looking through generated assembly shows that the calls of __cyg_* 
> functions
> are emitted, but these functions itself are generated with mangled names.
> Here is a piece of 'nm' output:
>
>         U __cyg_profile_func_enter
>         U __cyg_profile_func_exit
> ...
> 00000050 T _Z23__cyg_profile_func_exitPvS_
> 00000000 T _Z24__cyg_profile_func_enterPvS_
> ...
>
> The documentation around '-finstrument-functions' says nothing about C 
> vs. C++
> differences, so I'm confused why it doesn't work for C++ also.
>
> GCC version is 3.4.3.
>
> Thanks,
> Dmitry
>