== What's the difference between extern and static inline ? ==

Let Linus explain :

• - "static inline" means "we have to have this function, if you use it
  • but don't inline it, then make a static version of it in this compilation unit"
  - "extern inline" means "I actually _have_ an extern for this function,
  • but if you want to inline it, here's the inline-version"

But also see Inline Functions in C.