How to implement a leveled debug system?

Question

by design, in the environment I'm working right now I can't use a debugger to try to detect bugs, so pretty much always when I need to debug a functionality I end up outputting some info.

To do that I've done the following:

#ifdef DEBUG
    #define printd(x) printf x
#else
    #define printd(x)
#endif

So when I need to print some debug info I use printd() instead of printf().

The problem I've found is that I need a leveled system, there are messages that may be important in a determined debug level, but irrelevant when debugging other parts of the code.

So my question is, how can I implement a leveled debug system? I value simplicity, I mean, I prefer my actual system than needing a lot of code or confusing code when using it. Something like printd(level, format, ...) would be awesome.

Answer 1

Sure, there are more elegant ways to do this, of course, but this works just fine

#ifdef DEBUG
 extern int g_debuglevel;
 #define printd(level, x) (level <= g_debuglevel) ? 0 : printf x
#else
 #define printd(level, x)
#endif

Although personally I prefer this

#ifdef DEBUG
 extern void printdf(level, fmt, ...);
 #define printd printfd
#else
 #define printd
#endif

where printdf is a function that tests the level and then calls vprintf passing along the fmt and va_args.