c++ - Predefined Macros for function name __func__

Question

I am attempting to build a debug log message function that records the file, line, and function of of where the log message was called from.

#define DEBUG_PANIC(p) CLogging::Debuglogf( "Debug marker (%s) - ::%s() in file: %s(%d)", p, __func__ , __FILE__, __LINE__ );

The above code works on some compilers but not all. My code needs to be cross compatible with GCC as well as Microsoft Visual studios. I have added the below defines to help with compatibility.

#ifndef __FUNCTION_NAME__
    #if defined __func__ 
        // Undeclared 
        #define __FUNCTION_NAME__   __func__ 
    #elif defined __FUNCTION__ 
        // Undeclared
        #define __FUNCTION_NAME__   __FUNCTION__  
    #elif defined __PRETTY_FUNCTION__
        // Undeclared
        #define __FUNCTION_NAME__   __PRETTY_FUNCTION__
    #else
        // Declared
        #define __FUNCTION_NAME__   "N/A"   
    #endif // __func__ 

#endif // __FUNCTION_NAME__

#define DEBUG_PANIC(p) CLogging::Debuglogf( "Debug marker (%s) - ::%s() in file: %s(%d)", p, __FUNCTION_NAME__, __FILE__, __LINE__ );

The problem with the above code snippet is that it is the #else macro is active on all compilers while the other macros are not. in other words #if defined __func__ is false on compilers where __func__ is a predefined macro.

My question is

• How do I create a cross compiler macro to find the function name ?
• How can I tell if a __func__ can be used?

Answer 1

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