The compiler can assume that argc will not change within the loop so it can optimize it. I just looked up the assembly output from gcc and it pulls the argc>1 o

The compiler can assume that argc will not change within the loop so it can optimize it. I just looked up the assembly output from gcc and it pulls the argc>1 outside of the loop and replaced the printf with puts. So something like: if argc>1 for (;;) puts(argv[1]) else for (;;) puts("y") The replacing of printf with puts is based on gcc having specific knowledge about the printf library function.