Use an absolute path in test_process_output_fail_to_start

[eminence]

This test is designed to ensure that running a non-existent executable
results in a correct error message (FileNotFound in this case of this
test). However, if you try to run an executable that doesn't exist, and
that requires searching through the $PATH, and one of the $PATH components
is not readable, then a PermissionDenied error will be returned, instead
of FileNotFound.

Using an absolute path skips the $PATH search logic in exec, thus by-passing the logic in exec that would have returned a PermissionDenied

In the specific case of my machine, /usr/bin/games was part of $PATH, but my user account wasn't in the games group (thus being unable to read /usr/bin/games)

See the man pages for execv and execve for more details.

I've tested this on Linux and OSX, and I am fairly certain that there will be no problems on Windows

[huonw]

Aren't paths in a different format on windows?

[eminence]

Yes, but I don't think that matters in this case. Recall that we don't actually want to run this thing, only to confirm it doesn't exist. I don't have easy access to a Windows machine with Rust, but I do have access to a Windows machine.

The following code snippet gives CreateProcess an absolute path (with a forward slash), and CreateProcess is correctly returning ERROR_FILE_NOT_FOUND. So I believe this will work just fine for this rust test

#include <Windows.h>
#include <stdio.h>

int main() {

    STARTUPINFO si;
    PROCESS_INFORMATION pi;

    ZeroMemory( &si, sizeof(si) );
    si.cb = sizeof(si);
    ZeroMemory( &pi, sizeof(pi) );

    if( !CreateProcess( NULL,           // No module name (use command line)
                "/does_not_exist",      // Command line
                NULL,                   // Process handle not inheritable
                NULL,                   // Thread handle not inheritable
                FALSE,                  // Set handle inheritance to FALSE
                0,                      // No creation flags
                NULL,                   // Use parent's environment block
                NULL,                   // Use parent's starting directory
                &si,                    // Pointer to STARTUPINFO structure
                &pi )                   // Pointer to PROCESS_INFORMATION structure
      )
    {
        const DWORD err = GetLastError();
        if (err == ERROR_FILE_NOT_FOUND) {
            printf("FileNotFound\n");
        } else {
            printf( "CreateProcess failed (%d).\n", err );
        }
    }
    return;

}

d:\temp\> test.exe
FileNotFound

Also note that if I give a path to something that does exist, but also using unix-style forward slashes, CreateProcess will run the thing. I am not sure, however, where this behavior is documented.

[eminence]

I finally got around to testing this on Windows, and this test passes there too