为什么写入标准输出时 WriteFile 会崩溃?

问题描述

这是一个使用 WinAPI 的 WriteFile(在 Microsoft Visual C++ 2008 Express 中编译)的Hello world"程序:

Here's a "Hello world" program that uses WinAPI's WriteFile (compiled in Microsoft Visual C++ 2008 Express):

int _tmain(int argc, _TCHAR* argv[])
{
    wchar_t str[] = L"Hello world";

    HANDLE out = GetStdHandle(STD_OUTPUT_HANDLE);
    if(out && out!=INVALID_HANDLE_VALUE)
    {
        WriteFile(out, str, sizeof(str), NULL, NULL);
        CloseHandle(out);
    }

    return 0;
}

如果在控制台窗口中执行，它会愉快地迎接世界.但是，如果您尝试重定向其标准输出，如

If executed in a console window, it happily greets the world. If you try to redirect its standard output, however, as in

hello.exe > output.txt

程序在 WriteFile 中崩溃(NULL 指针异常).尽管如此，output.txt 仍然存在并包含完整的正确输出.

the program crashes in WriteFile (NULL pointer exception). Nonetheless, output.txt exists and contains the correct output in its entirety.

崩溃时的调用栈:

KernelBase.dll!_WriteFile@20()  + 0x75 bytes
kernel32.dll!_WriteFileImplementation@20()  + 0x4e bytes
srgprc2.exe!wmain(int argc=1, wchar_t * * argv=0x00483d88)  Line 15 + 0x16 bytes    C++

消息:srgprc2.exe 中 0x75ce85ea (KernelBase.dll) 处的未处理异常:0xC0000005:访问冲突写入位置 0x00000000."

The message: "Unhandled exception at 0x75ce85ea (KernelBase.dll) in srgprc2.exe: 0xC0000005: Access violation writing location 0x00000000."

这里发生了什么?谢谢！

What's going on here? Thanks!

推荐答案

WriteFile的第四个参数不是可选的.您传递的是 NULL，这是不允许的.

The fourth parameter to WriteFile is not optional. You are passing NULL, which is not allowed.

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