GCC func gets evaluated to an empty string

Given the following code in a project I'm working on:

/* Pre-definitions in a pre-definitions file to be included in the project */
#ifdef  WIN32
#define __FUNCNAME__ __FUNCTION__
#else
#define __FUNCNAME__ __func__  
#endif

/* My definitions */
#define MAC() \
     MAC1()

#define MAC1() \
     myPrintFunction(__FUNCNAME__)

/* My print function */
void myPrintFunction(const char * functionName)
{
     printf("\n func name: %s \n",functionName);
}

/* Macro usage example function */
void myFunction()
{
     if (some_condition)
     {
         MAC();
     }
}

The function name is presented as an empty string. Any idea why, and how can I fix it?

Code compiled and tested on Linux machine, using GCC compiler.

Solution

Use __func__ out of the box. It's been part of the C standard since C99. Change your compiler settings to use at least that standard.

Note that __func__ is not a macro but a predefined identifier which takes the form such that writing it anywhere within a function body is exactly equivalent to using it at that point, having first written

static const char __func__[] = "function-name";

just after the opening brace of a function body.

Formally the behaviour of your current code is undefined. Any symbol containing two consecutive underscores is reserved by the system. (That includes macro names, function names, and variable names.)

GCC __func__ gets evaluated to an empty string

GCC func gets evaluated to an empty string