#ifdef vs #if - which is better/safer as a method for enabling/disabling compilation of particular sections of code?

Question

This may be a matter of style, but there\'s a bit of a divide in our dev team and I wondered if anyone else had any ideas on the matter...

Basically, we have some de

Answer 1

I like #define DEBUG_ENABLED (0) when you might want multiple levels of debug. For example:

#define DEBUG_RELEASE (0)
#define DEBUG_ERROR (1)
#define DEBUG_WARN (2)
#define DEBUG_MEM (3)
#ifndef DEBUG_LEVEL
#define DEBUG_LEVEL (DEBUG_RELEASE)
#endif
//...

//now not only
#if (DEBUG_LEVEL)
//...
#endif

//but also
#if (DEBUG_LEVEL >= DEBUG_MEM)
LOG("malloc'd %d bytes at %s:%d\n", size, __FILE__, __LINE__);
#endif

Makes it easier to debug memory leaks, without having all those log lines in your way of debugging other things.

Also the #ifndef around the define makes it easier to pick a specific debug level at the commandline:

make -DDEBUG_LEVEL=2
cmake -DDEBUG_LEVEL=2
etc

If not for this, I would give advantage to #ifdef because the compiler/make flag would be overridden by the one in the file. So you don't have to worry about changing back the header before doing the commit.