printf的是否需要在X86-64额外栈空间？ [英] Does printf require additional stack space on the x86-64?

问题描述

虽然我知道这是最好使用编译器内在函数，而对于这个问题， printf_chk ，也把数据 .RODATA 部分，我期待在获得汇编语言更深入的了解，并有兴趣在紧凑code。也有一些是关于的printf 我不明白。我知道放在哪里的参数，我知道如何使用％人的可变参数，但它似乎需要，我可以不占额外的堆栈空间。

While I know it is best to use compiler intrinsics, and for that matter, printf_chk, and also to put data in .rodata sections, I'm looking at gaining a deeper understanding of assembly language and am interested in compact code. There is something about printf I don't understand. I know where to put the parameters, and I know how to use %al for varargs, but it appears to be requiring additional stack space that I cannot account for.

这短节目

        .text
        .globl  main
main:
        movsd   value(%rip), %xmm0    # value to print
        movl    $format, %edi         # format string
        movl    $1, %eax              # one floating-point arg
        call    printf
        movl    $0, %eax              # return 0 from main
        ret
        .align 8
value:  .double 74.321 
format: .asciz "%g\n"

给出了一个段错误。

gives a segfault.

然而，当我添加额外的堆栈空间的框架，它工作正常：

However, when I add additional stack space to the frame, it works fine:

        .text
        .globl  main
main:
        subq    $8, %rsp              # ADD SOME STACK SPACE TO FRAME (WHY?)
        movsd   value(%rip), %xmm0    # value to print
        movl    $format, %edi         # format string
        movl    $1, %eax              # one floating-point arg
        call    printf
        movl    $0, %eax              # return 0 from main
        addq    $8, %rsp              # REMOVE ADDED STACK SPACE
        ret
        .align 8
value:  .double 74.321 
format: .asciz "%g\n"

难道是对齐问题？ （我得到了同样的问题时，值和格式是在 .RODATA 部分。）

推荐答案

的堆栈必须对齐的16字节，根据www.x86-64.org/documentation/abi.pdf并且还微软的 http://msdn.microsoft.com/en-us/library/ms235286 （v = VS.80）的.aspx

The stack must be 16-byte aligned, according to the www.x86-64.org/documentation/abi.pdf and also Microsoft's http://msdn.microsoft.com/en-us/library/ms235286(v=vs.80).aspx

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