Question

...../PluginLoader.h:34: multiple definition of 'Dummy_Func_For_Generating_FUNCTION_NAME_Macro()'

The above error is output for the below code. I have include guards in my file. And everything else compiles fine.

EDIT: What I was trying to achieve was to check if __PRETTY_FUNCTION__ was defined, and if it was, use it later in code via FUNCTION_NAME macro (For logging purposes). If __PRETTY_FUNCTION__ is not defined, use next best thing and so on. However, the responses I got made me realize that this impossible. So, if __PRETTY_FUNCTION__ and all these others are not macros, what are they? And how do I check if a certain implementation has one of them or not?

    void Dummy_Func_For_Generating_FUNCTION_NAME_Macro()
    {
#ifndef FUNCTION_NAME
    #ifdef __PRETTY_FUNCTION__
        #define FUNCTION_NAME __PRETTY_FUNCTION__
    #elif __FUNCTION__
        #define FUNCTION_NAME __FUNCTION__
    #elif __func__
        #define FUNCTION_NAME __func__
    #else
        #define FUNCTION_NAME ""
    #endif
#endif
    }

Answer 1

void Dummy_Func_For_Generating_FUNCTION_NAME_Macro() is a function, not a macro. Functions don’t create macros. Macros are resolved in preprocessor phase, and functions in compiler phase. Remove the function definition, and leave only #ifndef block.

Use compiler identifying macros to figure out which function identifying macro to use. For instance:

#ifdef _MSC_VER // Visual Studio
    #define FUNCTION_NAME __FUNCTION__
#endif