Question

I’d like to make a debug logging function with the same parameters as printf. But one that can be removed by the pre-processor during optimized builds.

For example:

Debug_Print('Warning: value %d > 3!\n', value); 

I’ve looked at variadic macros but those aren’t available on all platforms. gcc supports them, msvc does not.

Answer 1

I still do it the old way, by defining a macro (XTRACE, below) which correlates to either a no-op or a function call with a variable argument list. Internally, call vsnprintf so you can keep the printf syntax:

#include <stdio.h>  void XTrace0(LPCTSTR lpszText) {    ::OutputDebugString(lpszText); }  void XTrace(LPCTSTR lpszFormat, ...) {     va_list args;     va_start(args, lpszFormat);     int nBuf;     TCHAR szBuffer[512]; // get rid of this hard-coded buffer     nBuf = _vsnprintf(szBuffer, 511, lpszFormat, args);     ::OutputDebugString(szBuffer);     va_end(args); } 

Then a typical #ifdef switch:

#ifdef _DEBUG #define XTRACE XTrace #else #define XTRACE #endif 

Well that can be cleaned up quite a bit but it’s the basic idea.