为什么只有在Visual Studio下运行可执行文件时CreateFile才会失败？

Question

我用WinAPI写了一个简单的check_file_ref函数来检查两个路径是否引用同一个文件。代码很好。它是用C（Visual /TC）的Visual Studio 2017编译的。

奇怪的是CreateFileA（winapi）在Visual Studio下运行可执行文件时总是失败（即执行没有调试），返回一个无效的文件句柄。否则，当可执行文件在Visual Studio外部运行时，它按预期工作。

工作目录在任何情况下都是相同的。

main.c中：

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <windows.h>

/**
 * Check whether two paths reference the same file.
 * @param p1 File path 1.
 * @param p2 File path 2.
 * @return 0 same file, 1 different files, < 0 on failure.
 */
int
check_file_ref(char const * p1, char const * p2)
{
    if ( !p1 || !p2 )
        return -1;
    if ( p1 == p2 )
        return 0;
    if ( strcmp(p1, p2) == 0 )
        return 0;

    int ret;
    DWORD share, flags;
    HANDLE f1, f2;
    BY_HANDLE_FILE_INFORMATION s1, s2;

    ret = -1;
    share = FILE_SHARE_READ | FILE_SHARE_WRITE;
    flags = FILE_ATTRIBUTE_NORMAL;

    f1 = CreateFileA(p1, GENERIC_READ, share, NULL, OPEN_EXISTING, flags, NULL);
    f2 = CreateFileA(p2, GENERIC_READ, share, NULL, OPEN_EXISTING, flags, NULL);

    if ( f1 == INVALID_HANDLE_VALUE ) {
        fprintf(stderr, "Could not open %s file, error %d\n", p1, GetLastError());
        goto cleanup;
    }
    if ( f2 == INVALID_HANDLE_VALUE ) {
        fprintf(stderr, "Could not open %s file, error %d\n", p2, GetLastError());
        goto cleanup;
    }
    if ( GetFileInformationByHandle(f1, &s1) == 0 ) {
        fprintf(stderr, "Could not get %s file information, error %d\n", p1, GetLastError());
        goto cleanup;
    }
    if ( GetFileInformationByHandle(f2, &s2) == 0 ) {
        fprintf(stderr, "Could not get %s file information, error %d\n", p2, GetLastError());
        goto cleanup;
    }

/*
    The identifier (low and high parts) and the volume serial number uniquely
    identify a file on a single computer. To determine whether two open handles
    represent the same file, combine the identifier and the volume serial number
    for each file and compare them.

    See
    https://docs.microsoft.com/fr-fr/windows/desktop/api/fileapi/nf-fileapi-getfileinformationbyhandle
    https://docs.microsoft.com/fr-fr/windows/desktop/api/fileapi/ns-fileapi-_by_handle_file_information
*/
    ret = !(s1.dwVolumeSerialNumber == s2.dwVolumeSerialNumber
        &&  s1.nFileIndexLow == s2.nFileIndexLow
        && s1.nFileIndexHigh == s2.nFileIndexHigh);

cleanup:
    CloseHandle(f2);
    CloseHandle(f1);
    return ret;
}


int main()
{
    int ret;
    char workingDir[256];

    /* Both paths reference the same file.
       One is relative, the other absolute. */
    char * p1 = "hello.txt";
    char * p2 = "C:/Users/bro/source/repos/tests/x64/Debug/hello.txt";

    ret = GetModuleFileNameA(NULL, workingDir, sizeof(workingDir));
    printf("working dir: %s\n", (ret == 0 ? "err" : workingDir));

    /* Should return 0. */
    ret = check_file_ref(p1, p2);
    printf("p1: %s\n", p1);
    printf("p2: %s\n", p2);
    printf("check_file_ret ret %d ", ret);

    if      ( ret == 0 ) printf("(same file)\n");
    else if ( ret == 1 ) printf("(different files)\n");
    else                 printf("(error)\n");

    return 0;
}

可视化的可执行运行：

CreateFileA fails

可执行文件直接从cmd行运行：

CreateFileA works

为什么只有在Visual Studio下运行可执行文件时CreateFileA才会失败？

Answer 1

从VisualStudio运行应用程序时，默认工作目录是项目位置，由VS宏$(ProjectDir)定义。您可以通过打开项目属性来更改它：在解决方案资源管理器中右键单击项目，然后从上下文菜单中选择“属性”。选择Debugging并更改Working Directory属性。例如，在您的情况下，解决方案可能是$(OutDir)或所需位置的绝对路径。