Macros can satisfy that in simple cases (like the NEXT_BYTE macro in x6502), and inline functions (like set_flags, get_flag, mem_abs, etc.) can handle more comp

Macros can satisfy that in simple cases (like the NEXT_BYTE macro in x6502), and inline functions (like set_flags, get_flag, mem_abs, etc.) can handle more complex cases. Both of these result in the code in the contents of the "function" being directly inserted into the calling block. (For inline functions, that's only true if you turn on optimizations, but I think even O1 on any C99 compiler turns on inlining). In general, if I need something to avoid function calls, I'll use macros as a shorthand for a complex expression (like NEXT_BYTE) and inline functions for anything that involves one or more full statements (like set_flags). Obviously I don't follow that too dogmatically, because mem_abs is an inline function.