Is is the opposite. The original C compiler produced instructions very closely to the higher level language. As such, it produces code based on what you tell i

Is is the opposite. The original C compiler produced instructions very closely to the higher level language. As such, it produces code based on what you tell it, no more, no less. If you don't tell it what value to return from a subroutine, it does not generate the code to. It is quite common to have a function that does not return a value. The case shown here is not a case of the compiler doing 'what it likes', but the compiler not emitting any code for it. The fact that the return value from the function called last is still in the register used to return values when the function returns is simply a result of no code that touches that register in between. As someone else pointed out, if you look at the code generated for a PDP-11 all the quirky things like, pointers with pre or post increment operators make much more sense as they emit instructions that do just that.