Question

I am writing a header-only library, and I can’t make up my mind between declaring the functions I provide to the user static or inline. Is there any reason why I should prefer one to the other in that case?

Answer 1

They both provide different functionalities.

There are two implications of using the inline keyword(§ 7.1.3/4):

1. It hints the compiler that substitution of function body at the point of call is preferable over the usual function call mechanism.
2. Even if the inline substitution is omitted, the other rules(especially w.r.t One Definition Rule) for inline are followed.

The static keyword on the function forces the inline function to have an internal linkage(inline functions have external linkage) Each instance of such a function is treated as a separate function(address of each function is different) and each instance of these functions have their own copies of static local variables & string literals(an inline function has only one copy of these)