• 145 Posts
  • 11 Comments
Joined 9 months ago
Cake day: June 8th, 2024
  • kiri@ani.socialOPtoProgrammer Animemes@lemmy.world•C chanEnglish
    5·
    12 days ago

    There is one more intresting fact. If you use -O3 flag (for clang -O1, -O2, …) compiler performs tail recursion optimization and transforms the recursion into an infinite loop, so there is no stack overflow.

    Assembly

    gcc -O0

    	.file	"main.c"
	.text
	.globl	main
	.type	main, @function
main:
.LFB0:
	.cfi_startproc
	pushq	%rbp
	.cfi_def_cfa_offset 16
	.cfi_offset 6, -16
	movq	%rsp, %rbp
	.cfi_def_cfa_register 6
	movl	$0, %eax
	call	main
	nop
	popq	%rbp
	.cfi_def_cfa 7, 8
	ret
	.cfi_endproc
.LFE0:
	.size	main, .-main
	.ident	"GCC: (GNU) 14.2.1 20250207"
	.section	.note.GNU-stack,"",@progbits

    gcc -O3

    	.file	"main.c"
	.text
	.section	.text.startup,"ax",@progbits
	.p2align 4
	.globl	main
	.type	main, @function
main:
.LFB0:
	.cfi_startproc
	.p2align 1
	.p2align 4
	.p2align 3
.L2:
	jmp	.L2
	.cfi_endproc
.LFE0:
	.size	main, .-main
	.ident	"GCC: (GNU) 14.2.1 20250207"
	.section	.note.GNU-stack,"",@progbits

    clang -O1

    	.text
	.file	"main.c"
	.globl	main                            # -- Begin function main
	.p2align	4, 0x90
	.type	main,@function
main:                                   # @main
	.cfi_startproc
# %bb.0:
	.p2align	4, 0x90
.LBB0_1:                                # =>This Inner Loop Header: Depth=1
	jmp	.LBB0_1
.Lfunc_end0:
	.size	main, .Lfunc_end0-main
	.cfi_endproc
                                        # -- End function
	.ident	"clang version 19.1.7"
	.section	".note.GNU-stack","",@progbits
	.addrsig

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