Custom control structure 'detach' with accidental return.

detach.c

#include <stdlib.h>
#include <unistd.h>
#include <stdio.h>

#define detach if (fork()); else for (;; exit(0))

int calculate () {
	detach {
		sleep(1);
		return 5;
	}
	return 4;
}

int main () {
	printf("Calculating.\n");
	printf("Calculated: %d\n", calculate());
	printf("Done.\n");

	return 0;
}