Question

I need a macro to pass the __FILE__ and __LINE__ to a function which has default arguments. This has opened up a can of worms, since default args with macros are either not possible or very messy, and I need to support both GCC and MSVC if possible:

class Class
{
#ifdef _DEBUG

   int Function(int a, int b = 10, int c = 20) { return a + b + c; }

#else

   int DebugFunction(const char* filename, int lineNo, int a, int b = 10, int c = 20)
   {
      printf("%s (%i) a:%i b:%i c:%i\n", filename, lineNo, a, b, c);
      return a + b + c;
   }

   //Not possible
   #define Function( DebugFunction(__FILE__, __LINE__

#endif
}

I’ve tried \escaping the ( to no avail. The codebase is huge, so fixing up the missing default args or creating multiple macros isn’t a popular option.

Any solutions?

Answer 1

You can make a variadic macro:

#define Function(...) DebugFunction(__FILE__, __LINE__, __VA_ARGS__)

Since you cannot “overload” macros, this might be your best bet.