Fstream does not recognise relative path [duplicate] - c++

Question

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://learn.microsoft.com/fr-fr/windows/desktop/api/fileapi/nf-fileapi-getfileinformationbyhandle
https://learn.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;
}
Executable run under visual:
CreateFileA fails
Executable run directly from cmd line:
CreateFileA works
Why is CreateFileA failing only when the executable is run under Visual Studio?

Answer 1

When you run an application from VisualStudio the default working directory is a project location, which is defined by VS macro $(ProjectDir). You can change it by openning the project properties: Right click on the project in Solution Explorer and select Properties from the context menu. There select Debugging and change Working Directory property. For example, in your case the solution could be $(OutDir) or absolute path to the required location.