Predefined Macros for function name __func__

You’re assuming __func__ is a macro, but it’s not. It’s a conditionally-supported predefined identifier, so you can’t check it with #if defined or #ifdef.

If the compilers have no way of telling you whether this is supported (they could via a _FUNC_SUPPORTED or something, I’m not saying they actually are doing this), you’ll have to check the compiler instead of the actual identifier.

Something along the lines:

#ifndef __FUNCTION_NAME__
    #ifdef WIN32   //WINDOWS
        #define __FUNCTION_NAME__   __FUNCTION__  
    #else          //*NIX
        #define __FUNCTION_NAME__   __func__ 
    #endif
#endif