What does __inline__ mean ?

Question

I am trying to learn C. Reading through some code, I came across a line like this:

__inline__ void () ...

What does the __inline__

Answer 1

basically, it's a hint to the compiler; it's a suggestion that where this function is used it might be possible to insert the code directly.

the idea is that doing so could be more efficient, since it avoids the overhead of a function call; but, ultimately, the compiler uses a combination of code size, optimization options specified, and a little bit of voodoo to decide whether to actually respect this hint.

the voodoo bit is most confusing part. :) don't necessarily rely on __inline__ (or the more standard inline) to work; optimize your algorithms or reorganize your code instead if you really care about speed.