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

[Dmitry Antipov <antipov at dev dot rtsoft dot ru>]

(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