Using gcc/g++ instrument functions with MinGW?

Question

Hello,

i try to use the gcc instrument functions with g++ compiler of MinGW, but i always got linker issues. Is it possible to use the instrument functions with MinGW/MSYS?

The linker failure output:

$ g++ instrumentFunctions.cpp -o iftest -finstrument-functions >> iflog.txt
C:/Users/HELLHO~1/AppData/Local/Temp/ccUwxrxt.o:instrumentFunctions.cpp:(.text+0x4e): undefined reference to `__cyg_prof
ile_func_enter'
C:/Users/HELLHO~1/AppData/Local/Temp/ccUwxrxt.o:instrumentFunctions.cpp:(.text+0x158): undefined reference to `__cyg_pro
file_func_exit'
C:/Users/HELLHO~1/AppData/Local/Temp/ccUwxrxt.o:instrumentFunctions.cpp:(.text+0x179): undefined reference to `__cyg_pro
file_func_enter'
C:/Users/HELLHO~1/AppData/Local/Temp/ccUwxrxt.o:instrumentFunctions.cpp:(.text+0x18c): undefined reference to `__cyg_pro
file_func_exit'
C:/Users/HELLHO~1/AppData/Local/Temp/ccUwxrxt.o:instrumentFunctions.cpp:(.text+0x1a7): undefined reference to `__cyg_pro
file_func_enter'
C:/Users/HELLHO~1/AppData/Local/Temp/ccUwxrxt.o:instrumentFunctions.cpp:(.text+0x1bf): undefined reference to `__cyg_pro
file_func_exit'
C:/Users/HELLHO~1/AppData/Local/Temp/ccUwxrxt.o:instrumentFunctions.cpp:(.text+0x1db): undefined reference to `__cyg_pro
file_func_enter'
C:/Users/HELLHO~1/AppData/Local/Temp/ccUwxrxt.o:instrumentFunctions.cpp:(.text+0x1f3): undefined reference to `__cyg_pro
file_func_exit'
C:/Users/HELLHO~1/AppData/Local/Temp/ccUwxrxt.o:instrumentFunctions.cpp:(.text+0x22f): undefined reference to `__cyg_pro
file_func_enter'
C:/Users/HELLHO~1/AppData/Local/Temp/ccUwxrxt.o:instrumentFunctions.cpp:(.text+0x27a): undefined reference to `__cyg_pro
file_func_exit'
C:/Users/HELLHO~1/AppData/Local/Temp/ccUwxrxt.o:instrumentFunctions.cpp:(.text+0x29b): undefined reference to `__cyg_pro
file_func_enter'
C:/Users/HELLHO~1/AppData/Local/Temp/ccUwxrxt.o:instrumentFunctions.cpp:(.text+0x2e4): undefined reference to `__cyg_pro
file_func_exit'
C:/Users/HELLHO~1/AppData/Local/Temp/ccUwxrxt.o:instrumentFunctions.cpp:(.text+0x2ff): undefined reference to `__cyg_pro
file_func_enter'
C:/Users/HELLHO~1/AppData/Local/Temp/ccUwxrxt.o:instrumentFunctions.cpp:(.text+0x326): undefined reference to `__cyg_pro
file_func_exit'
C:/Users/HELLHO~1/AppData/Local/Temp/ccUwxrxt.o:instrumentFunctions.cpp:(.text+0x341): undefined reference to `__cyg_pro
file_func_enter'
C:/Users/HELLHO~1/AppData/Local/Temp/ccUwxrxt.o:instrumentFunctions.cpp:(.text+0x368): undefined reference to `__cyg_pro
file_func_exit'
C:/Users/HELLHO~1/AppData/Local/Temp/ccUwxrxt.o:instrumentFunctions.cpp:(.text$printf[_printf]+0x16): undefined referenc
e to `__cyg_profile_func_enter'
C:/Users/HELLHO~1/AppData/Local/Temp/ccUwxrxt.o:instrumentFunctions.cpp:(.text$printf[_printf]+0x43): undefined referenc
e to `__cyg_profile_func_exit'
C:/Users/HELLHO~1/AppData/Local/Temp/ccUwxrxt.o:instrumentFunctions.cpp:(.text$_ZSt3minIjERKT_S2_S2_[unsigned int const&
 std::min<unsigned int>(unsigned int const&, unsigned int const&)]+0x15): undefined reference to `__cyg_profile_func_ent
er'
C:/Users/HELLHO~1/AppData/Local/Temp/ccUwxrxt.o:instrumentFunctions.cpp:(.text$_ZSt3minIjERKT_S2_S2_[unsigned int const&
 std::min<unsigned int>(unsigned int const&, unsigned int const&)]+0x42): undefined reference to `__cyg_profile_func_exi
t'
collect2: ld returned 1 exit status

g++ command i use:

g++ iftest.cpp -o iftest -finstruction-functions

Listing of my testsource:

#include <stdio.h>

  void __cyg_profile_func_enter( void *, void * ) __attribute__ ((no_instrument_function));

  void __cyg_profile_func_enter(void *func, void *callsite)
  {
    printf("%p\n", (int)func);
  }


  void func_c( void )
  {
    return;
  }

  void func_b( void )
  {
    func_c();

    return;
  }

  void func_a( void )
  {
    func_b();
    return;
  }


  int main()
  {
    func_a();
    func_c();
  }

Answer 1

You need to give the __cyg* functions "C" linkage. A function defined in C++ normally gets a mangled name which can't be used from libraries not written in C++. You can ask the compiler to give a function the name C would give it by using an `extern "C"{} block. The following should compile fine.

#include <stdio.h>

extern "C" {
  void __cyg_profile_func_enter( void *, void * ) __attribute__ ((no_instrument_function));

  void __cyg_profile_func_enter(void *func, void *callsite)
  {
    printf("enter %p\n", func);
  }
  void __cyg_profile_func_exit( void *, void * ) __attribute__ ((no_instrument_function));

  void __cyg_profile_func_exit(void *func, void *callsite)
  {
    printf("exit %p\n", func);
  }

}
  void func_c( void )
  {
    return;
  }

  void func_b( void )
  {
    func_c();

    return;
  }

  void func_a( void )
  {
    func_b();
    return;
  }


  int main()
  {
    func_a();
    func_c();
  }

Answer 2

Thanks for your hint, it work's fine.