linux 64 简单结构体传递-优快云博客

本文探讨了C语言中结构体的使用，并通过一个具体的例子展示了如何将C语言代码编译为汇编语言，进而深入理解结构体成员赋值的过程。此过程对于理解数据结构在底层内存中的布局具有重要意义。

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struct context {
    int a;
    int b;
    int c;
};

void f(struct context *s1, struct context *s2)
{
    s2->a = s1->a;
    s2->b = s1->b;
    s2->c = s2->c;
}

int main()
{
    struct context s1 , s2;
    s1.a = 1;
    s2.a = 2;

    s1.b = 3;
    s2.b = 4;
    
    s1.c = 5;
    s2.c = 6;
   
    f(&s1, &s2);
    return 0;
}

编译为汇编

gcc -masm=intel -S struct.c -o struct.s

struct.s 代码 (注意 64位系统指针占用 8 个字节)

	.file	"struct.c"
	.intel_syntax
	.text
.globl f
	.type	f, @function
f:
.LFB2:
	push	%rbp
.LCFI0:
	mov	%rbp, %rsp
.LCFI1:
	mov	QWORD PTR [%rbp-8], %rdi
	mov	QWORD PTR [%rbp-16], %rsi
	mov	%rax, QWORD PTR [%rbp-8]
	mov	%edx, DWORD PTR [%rax]
	mov	%rax, QWORD PTR [%rbp-16]
	mov	DWORD PTR [%rax], %edx
	mov	%rax, QWORD PTR [%rbp-8]
	mov	%edx, DWORD PTR [%rax+4]
	mov	%rax, QWORD PTR [%rbp-16]
	mov	DWORD PTR [%rax+4], %edx
	mov	%rax, QWORD PTR [%rbp-16]
	mov	%edx, DWORD PTR [%rax+8]
	mov	%rax, QWORD PTR [%rbp-16]
	mov	DWORD PTR [%rax+8], %edx
	leave
	ret
.LFE2:
	.size	f, .-f
.globl main
	.type	main, @function
main:
.LFB3:
	push	%rbp
.LCFI2:
	mov	%rbp, %rsp
.LCFI3:
	sub	%rsp, 32
.LCFI4:
	mov	DWORD PTR [%rbp-16], 1
	mov	DWORD PTR [%rbp-32], 2
	mov	DWORD PTR [%rbp-12], 3
	mov	DWORD PTR [%rbp-28], 4
	mov	DWORD PTR [%rbp-8], 5
	mov	DWORD PTR [%rbp-24], 6
	lea	%rsi, [%rbp-32]
	lea	%rdi, [%rbp-16]
	call	f
	mov	%eax, 0
	leave
	ret
.LFE3:
	.size	main, .-main
	.section	.eh_frame,"a",@progbits
.Lframe1:
	.long	.LECIE1-.LSCIE1
.LSCIE1:
	.long	0x0
	.byte	0x1
	.string	"zR"
	.uleb128 0x1
	.sleb128 -8
	.byte	0x10
	.uleb128 0x1
	.byte	0x3
	.byte	0xc
	.uleb128 0x7
	.uleb128 0x8
	.byte	0x90
	.uleb128 0x1
	.align 8
.LECIE1:
.LSFDE1:
	.long	.LEFDE1-.LASFDE1
.LASFDE1:
	.long	.LASFDE1-.Lframe1
	.long	.LFB2
	.long	.LFE2-.LFB2
	.uleb128 0x0
	.byte	0x4
	.long	.LCFI0-.LFB2
	.byte	0xe
	.uleb128 0x10
	.byte	0x86
	.uleb128 0x2
	.byte	0x4
	.long	.LCFI1-.LCFI0
	.byte	0xd
	.uleb128 0x6
	.align 8
.LEFDE1:
.LSFDE3:
	.long	.LEFDE3-.LASFDE3
.LASFDE3:
	.long	.LASFDE3-.Lframe1
	.long	.LFB3
	.long	.LFE3-.LFB3
	.uleb128 0x0
	.byte	0x4
	.long	.LCFI2-.LFB3
	.byte	0xe
	.uleb128 0x10
	.byte	0x86
	.uleb128 0x2
	.byte	0x4
	.long	.LCFI3-.LCFI2
	.byte	0xd
	.uleb128 0x6
	.align 8
.LEFDE3:
	.ident	"GCC: (GNU) 4.1.2 20070115 (prerelease) (SUSE Linux)"
	.section	.note.GNU-stack,"",@progbits

转载于:https://my.oschina.net/tsh/blog/1475546