What are C macros useful for?

Question

I have written a little bit of C, and I can read it well enough to get a general idea of what it is doing, but every time I have encountered a macro it has thrown me complet

Answer 1

Macros .. for when your &#(*$& compiler just refuses to inline something.

That should be a motivational poster, no?

In all seriousness, google preprocessor abuse (you may see a similar SO question as the #1 result). If I'm writing a macro that goes beyond the functionality of assert(), I usually try to see if my compiler would actually inline a similar function.

Others will argue against using #if for conditional compilation .. they would rather you:

if (RUNNING_ON_VALGRIND)

rather than

#if RUNNING_ON_VALGRIND

.. for debugging purposes, since you can see the if() but not #if in a debugger. Then we dive into #ifdef vs #if.

If its under 10 lines of code, try to inline it. If it can't be inlined, try to optimize it. If its too silly to be a function, make a macro.