Answer 1

The "inline" keyword is a hint to the compiler that you want it to take the function body and "copy-and-paste" it wherever that function is used, as if it's a macro. This reduces the overhead of having to jump to a function address at the cost of using up more memory to insert the function everywhere. Generally it's used with small functions that don't really do too much (e.g., min, max).

Nowadays, you don't really need to use it; the compiler is smarter than you and will usually do whatever it wants regardless (which is why it's a "hint"-- the compiler will often just ignore it). Any decent compiler will inline functions for you as it sees fit, whether or not you tell it to.