Why is CreateFileA failing only when the executable is run under Visual Studio?

问题

I wrote a simple check_file_ref function using WinAPI to check whether two paths reference the same file. The code is fine. It's compiled with Visual Studio 2017 in C (flag /TC).

The weird thing is CreateFileA (winapi) always fails when the executable is run under Visual Studio (ie execute without debugging), returning an invalid file handle. Otherwise, it works as expected when the executable is run outside of Visual Studio.

The working dir is the same in any case.

main.c:

#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;
}