When to use inline function and when not to use it

Question

I know that inline is a hint or request to compiler and its used to avoid function call overheads.

So on what basis one can determine whether a function is a candidate for inlining or not ? In which case one should avoid inlining ?

Answer 1

The best way to find out is to profile your program and mark small functions that get called lots of times and burn through CPU cycles that as inline. The keyword here is "small" - once the function call overhead is negligible compared to the time spent in the function, it's pointless to inline them.

The other use I'd suggest is if you've got small functions that get called in performance critical code often enough to make a cache miss relevant, you should probably inline those as well. Again, it's something the profiler should be able to tell you.