Date created: 2024-10-06

Description

Inline functions are a [[c-compiler-suggestion|suggestion for the compiler]] to place the function code inline to where it's been executed. This is done for optimisation reasons.

Go wild here

Consider a simple C function like

inline uint8_t vga_entry_colour(enum vga_colour fg, enum vga_colour bg) {
	return fg | bg << 4;
}

All it does is a simple [[bitwise-operations|bitwise operation]]. If this function was declared as a simple function (not inline), every time we call it, the CPU would have to do all the regular things, jump to an address, prepare the stack, execute, pop the stack, return.

If the function is inline though, this gives the suggestion to the compiler to place the function code inline wherever it's being called, meaning the CPU doesn't have to do all the regular function-call things. This has the potential to improve performance if the function is being called many many times over.