Search code examples
cgccavr

avr-gcc never returning main optimalization

Somewhere I read that if I never return from main() loop, I can spare ~66 Bytes with some compiler switch in avr-gcc, but I couldn't find the site anymore.

This is for embedded:

main() {
 while(1)
 {
   // do stuff
 }
}
Solution

  • For gcc you can use a special attribute to indicate that your function does not return:

    int main() __attribute__ ((noreturn)) {
    for (;;) {
         // do stuff
    }
    __builtin_unreachable ();
}

    Optionally you can add __builtin_unreachable (); to indicate that some part of the code can never be reached.

    Although in most cases properly recognised by optimisation flags, without such while(1) can generate more code than for(;;).