Question

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while (1) Vs. for (;;) Is there a speed difference?

Hi,

Which is better,faster and more optimized way to implement infinite loop – for(;;) or while(1)? and why?

Answer 1

In any normal compiler, there should be absolutely no difference. For example, here’s what LLVM-clang generates (with the -O3 flag) for while (1) {}:

    .file   "test.c"
    .text
    .globl  main
    .align  16, 0x90
    .type   main,@function
main:
    pushl   %ebp
    movl    %esp, %ebp
    .align  16, 0x90
.LBB0_1:
    jmp .LBB0_1

Note the jmp .LBB0_1 part, which is the actual infinite loop. For the for (;;) kind, it generates absolutely the same code.

You can also try with other compilers for fun, but it’s best just stop worrying about it.

---

OK, I just had to try with gcc as well:

    .file   "test.c"
    .text
.globl main
    .type   main, @function
main:
    pushl   %ebp
    movl    %esp, %ebp
.L2:
    jmp .L2