When compiling, you should be able to specify an option to your compiler. For example, you can call GCC with the -DDEBUG option.
In this case, you would be better using:
#ifdef DEBUG
#endif
or:
#if defined(DEBUG)
#endif
if this is not the way you’re doing it now. I’m surprised that you don’t have a global header file for your project. Something along the lines of:
#undef DEBUG
#define DEBUG 1
in a file called “debug.h”. In your C programs, you can include this by using #include "debug.h"