为什么 setjmp() 在 windows 上接受 2 个参数，而在 linux 上只接受 1 个参数？

Question

此 setjmp.c 在 Microsoft Visual Studio Professional 2019（版本 16.10.1）

下的 windows 中构建

Rebuild started...
1>------ Rebuild All started: Project: setjmp, Configuration: Release x64 ------
1>setjmp.c
1>C:\Users\john\source\repos\setjmp\setjmp.c(48,10): warning C4013: 'setjmp' undefined; assuming extern returning int
1>Generating code
1>Previous IPDB not found, fall back to full compilation.
1>All 1 functions were compiled because no usable IPDB/IOBJ from previous compilation was found.
1>Finished generating code
1>setjmp.vcxproj -> C:\Users\john\source\repos\setjmp\x64\Release\setjmp.exe
1>Done building project "setjmp.vcxproj".
========== Rebuild All: 1 succeeded, 0 failed, 0 skipped ==========

实际的cl.exe C编译器命令是

1>    C:\Program Files (x86)\Microsoft Visual Studio19\Professional\VC\Tools\MSVC.29.30037\bin\HostX86\x64\CL.exe /c /Zi /nologo /W3 /WX- /diagnostics:column /sdl /O2 /Oi /GL /D NDEBUG /D _CONSOLE /D _UNICODE /D UNICODE /Gm- /EHsc /MD /GS /Gy /fp:precise /permissive- /Zc:wchar_t /Zc:forScope /Zc:inline /Fo"x64\Release\" /Fd"x64\Release\vc142.pdb" /external:env:EXTERNAL_INCLUDE /external:W3 /Gd /TC /FC /errorReport:prompt setjmp.c

源代码为

#include <stdio.h>
#include <stddef.h>
#include <stdint.h>

typedef         uint64_t QWORD;
typedef         uint32_t DWORD;
typedef         uint16_t WORD;
typedef         uint8_t  BYTE;

typedef struct MSTJMP_FLOAT128
{
    QWORD Part[2];
} MSTJMP_FLOAT128;

typedef struct JUMP_BUFFER
{
    QWORD Frame0;
    QWORD Rbx0;
    QWORD Rsp0;
    QWORD Rbp0;
    QWORD Rsi0;
    QWORD Rdi0;
    QWORD R120;
    QWORD R130;
    QWORD R140;
    QWORD R150;
    QWORD Rip0;
    DWORD MxCsr4;
    WORD FpCsr2;
    WORD Spare2;
    struct MSTJMP_FLOAT128 Xmm6x;
    struct MSTJMP_FLOAT128 Xmm7x;
    struct MSTJMP_FLOAT128 Xmm8x;
    struct MSTJMP_FLOAT128 Xmm9x;
    struct MSTJMP_FLOAT128 Xmm10x;
    struct MSTJMP_FLOAT128 Xmm11x;
    struct MSTJMP_FLOAT128 Xmm12x;
    struct MSTJMP_FLOAT128 Xmm13x;
    struct MSTJMP_FLOAT128 Xmm14x;
    struct MSTJMP_FLOAT128 Xmm15x;
} JUMP_BUFFER;

int main() {

    struct JUMP_BUFFER jumpbuffer;

   setjmp(&jumpbuffer, 0);

    return 0;
}

setjmp() 调用的反汇编是

setjmp(&jumpbuffer, 0);
00007FF641B51019  xor         edx,edx  
00007FF641B5101B  lea         rcx,[jumpbuffer]  
00007FF641B51020  call        __intrinsic_setjmp (07FF641B51C20h)

这导致 setjmp() 代码

--- d:\a01\_work\s\src\vctools\crt\vcruntime\src\eh\amd64\setjmp.asm ---------
00007FF82B6F0300  mov         qword ptr [rcx],rdx  
00007FF82B6F0303  mov         qword ptr [rcx+8],rbx  
00007FF82B6F0307  mov         qword ptr [rcx+18h],rbp

所以一切都正常运行，没有任何错误，因为 windows 在 setjmp.asm

中使用了 C 运行时内部函数

然而，在linux下，它会产生一个错误：

error: macro "setjmp" passed 2 arguments, but takes just 1

Google'ing 找到了这段代码：

#if defined(_WIN64)
/* On w64, setjmp is implemented by _setjmp which needs a second parameter.
 * If this parameter is NULL, longjump does no stack unwinding.
 * That is what we need for QEMU. Passing the value of register rsp (default)
 * lets longjmp try a stack unwinding which will crash with generated code. */
# undef setjmp
# define setjmp(env) _setjmp(env, NULL)
#endif

综上所述，windows可以带2个参数：

setjmp(&jumpbuffer, 0);

和 linux 可以带 1 个参数：

setjmp(&jumpbuffer);

为了验证 linux 喜欢那个 setjmp，我用 gdb 追踪如下：

Answer 1

你的问题是你没有 #include <setjmp.h> 所以编译器不知道函数签名并且 假设 setjmp 是返回 int 的函数并接受未知类型的未知数量的参数。当您声明 func() 时，它是一个在旧 C 标准中返回 int 的函数，您可以调用 func()、func(1, 2, 3) 或 func(1, "abc", 'd', 2, 3)... - 都是有效的

注意编译器输出中的警告

setjmp.c(48,10): warning C4013: 'setjmp' undefined; assuming extern returning int

也可以是reproducible on godbolt，MSVC也有同样的警告。你可以看到编译器没有报告任何错误，即使我添加了一些虚拟 setjmp 调用，如

setjmp(&jumpbuffer, 0);
setjmp();
setjmp(1, 2, "abc");
setjmp(&jumpbuffer, 0, 3, 4, 5);

见

Implicit function declarations sometimes work in C?
Why does declaration of function with int return type is not compulsory in C?
Are prototypes required for all functions in C89, C90 or C99?
warning: implicit declaration of function
Implicit function declarations in C
Is implicit function declaration legal in C89?
Is it portable to define and declare the function after calling it in main in C?

为什么 setjmp() 在 windows 上接受 2 个参数，而在 linux 上只接受 1 个参数？

Why does setjmp() take 2 args on windows but only 1 arg on linux?

c

ansi-c