By far my favorite trick is the one described here https://www.chiark.greenend.org.uk/~sgtatham/coroutines.html https://www.chiark.greenend.org.uk/~sgtatham/cor

By far my favorite trick is the one described here https://www.chiark.greenend.org.uk/~sgtatham/coroutines.html https://www.chiark.greenend.org.uk/~sgtatham/coroutines.html Effectively generators a la python or javascript, implemented using a set of macros that expand to a Duff's device control structure. #define crBegin(state) \ int *__state_ptr__ = &(state); \ *__state_ptr__ = 0; \ switch(*__state_ptr__) { case 0: #define yield(x) \ do { \ *__state_ptr__ = __LINE__; \ return x; \ case __LINE__:; \ } while (0) #define crFinish } struct counter_frame { int state; int i; }; int counter(struct counter_frame *frame) { crBegin(frame->state); frame->i = 0; while (1) { yield(frame->i++); } crFinish; } int main() { struct counter_frame my_counter; while (1) { printf("%d\n", counter(&my_counter)); } return 0; }