Loop efficiency comparison, while(true) VS for(;;)

[Winston]

As the title describes it all, i don't actually get why many people prefer for(;;) i've heard it's more efficient, but how does that work?

[Ianmac45]

it's the same in my experiences.......

the only thing i can think of is that the computer doesn't have to do any work when going to the next cycle for the for(;;) loop. with the while(true) loop, in each cycle the computer has to check to see if true is ... well, true

i hope that helps with this oh-so-complicated question/task

[smurfiness]

  Quote

this oh-so-complicated question/task

*LOL*

Personally, I think it's just that they want to look smarter. while(true) looks like a newbie mistake. for(;;) looks like you know what you're doing. I doubt either is any more efficient than the other. If the for loop actually is more efficient, the difference would be measured in thousandths (if even that much) of a second.

[kjordan2001]

Well, at least in C using gcc as the compiler, there is no difference. The assembly code output is identical.

While loop:

        .file   "infwhile.c"
        .section        .rodata
.LC0:
        .string "Hello world\n"
        .text
.globl main
        .type   main, @function
main:
        pushl   %ebp
        movl    %esp, %ebp
        subl    $8, %esp
        andl    $-16, %esp
        movl    $0, %eax
        addl    $15, %eax
        addl    $15, %eax
        shrl    $4, %eax
        sall    $4, %eax
        subl    %eax, %esp
.L2:
        movl    $.LC0, (%esp)
        call    printf
        jmp     .L2
        .size   main, .-main
        .section        .note.GNU-stack,"",@progbitsident  "GCC: (GNU) 3.4.4 (Gentoo 3.4.4-r1, ssp-3.4.4-1.0, pie-8.7.8)"

For loop:

        .file   "inffor.c"
        .section        .rodata
.LC0:
        .string "Hello world\n"
        .text
.globl main
        .type   main, @function
main:
        pushl   %ebp
        movl    %esp, %ebp
        subl    $8, %esp
        andl    $-16, %esp
        movl    $0, %eax
        addl    $15, %eax
        addl    $15, %eax
        shrl    $4, %eax
        sall    $4, %eax
        subl    %eax, %esp
.L2:
        movl    $.LC0, (%esp)
        call    printf
        jmp     .L2
        .size   main, .-main
        .section        .note.GNU-stack,"",@progbitsident  "GCC: (GNU) 3.4.4 (Gentoo 3.4.4-r1, ssp-3.4.4-1.0, pie-8.7.8)"

And the code to produce those was just

for(;;) { printf("Hello world\n"); }

while (1) { printf("Hello world\n"); }

How this works out in other languages, I can't be sure. It also depends on how the compiler interprets it. But an infinite loop is just calling the same block of code over and over. So that means once you reach the end of the code, you jump back up to the start of it, which is what we see here. There is no real difference between a for loop and a while loop in assembly, although they can differ some depending on how the compiler handles it. I've heard some people state that while loops are faster, but whether or not that's true, I don't know. It shouldn't be that way, but depending on the code and the compiler, it may be true.