24.9 Hints

ISO Standard: “The extent to which suggestions made by using the register storage-class specifier are effective (C90 6.5.1, C99 6.7.1).”
Implementation: The register storage class specifier generally has no effect.
ISO Standard: “The extent to which suggestions made by using the inline function specifier are effective (C99 6.7.4).”
Implementation: If -fno-inline or -O0 are specified, no functions will be inlined, even if specified with the inline specifier. Otherwise, the function may or may not be inlined dependent on the optimization heuristics of the compiler.