GCC Warns About Function Pointer to Object Pointer Cast

Question

Clearly casting between function pointers and object pointers is undefined behaviour in the general sense, but POSIX (see: dlsym) and WinAPI (see: GetProcAddress) require this.

Given this, and given the fact that such code is targeting a platform-specific API anyway, its portability to platforms where function pointers and object pointers aren't compatible is really irrelevant.

But -Wpedantic warns about it anyway, and #pragma GCC diagnostic ignored "-Wpedantic" has no effect:

warning: ISO C++ forbids casting between pointer-to-function and pointer-to-object [enabled by default]

I want to keep -Wpedantic enabled, since it does give good warnings, but I don't want to have real warnings and errors lost amidst a sea of irrelevant warnings about function pointer to object pointer casts.

Is there a way to accomplish this?

Running GCC 4.8.0 on Windows (MinGW):

gcc (rubenvb-4.8.0) 4.8.0

CODE SAMPLE

#include <windows.h>
#include <iostream>


int main (void) {

    std::cout << *reinterpret_cast<int *>(GetProcAddress(LoadLibraryA("test.dll"),"five")) << std::endl;

}

Emits (with -Wpedantic):

warning_demo.cpp: In function 'int main()':
warning_demo.cpp:7:87: warning: ISO C++ forbids casting between pointer-to-funct
ion and pointer-to-object [enabled by default]
  std::cout << *reinterpret_cast<int *>(GetProcAddress(LoadLibraryA("test.dll"),
"five")) << std::endl;

       ^

Answer 1

I think you could use g++'s system_header directive here:

wrap_GetProcAddress.h:

#ifndef wrap_GetProcAddress_included
#define wrap_GetProcAddress_included

#pragma GCC system_header

template <typename Result>
Result GetProcAddressAs( [normal parameters] )
{
    return reinterpret_cast<Result>(GetProcAddressAs( [normal parameters] ));
}

#endif