GCC Warns About Function Pointer to Object Pointer Cast

c++, c++11, gcc, gcc-pedantic, mingw

Solution

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

Problem

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; ^ ```

Original source