Compilers have pretty good heuristics when it comes to inlining.  Just make sure the function is static so the compiler knows it's inline-safe.  I mean, adding an 'inline' keyword doesn't hurt but it's just a hint to the compiler - one that gcc and clang happily ignore.

If you want to _force_ inlining, there's `__attribute__((always_inline))` but there's hardly ever a reason to use it.