[Bug 37402] New: WINAPI is not correct

https://bugs.winehq.org/show_bug.cgi?id=37402

Bug ID: 37402
           Summary: WINAPI is not correct
           Product: Wine
           Version: unspecified
          Hardware: x86
                OS: Linux
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: -unknown
          Assignee: [e-mail]
          Reporter: [e-mail]
      Distribution: ---

I've found a strang bug while testing my program.
I used few WINAPI funcs for codepage converting (the file path was in UTF-8,
and to open it, I needed to convert it to the Windows's awkward wchar_t and
back). I hadn't a copy of Windows that time, so I tested it on wine. There's
the tested code:

char* WcharToUTF8(wchar_t *in)
{
    uint64_t len = WideCharToMultiByte(CP_UTF8, MB_ERR_INVALID_CHARS, in, -1,
NULL, 0, NULL, NULL);
    char *out = (char*)calloc((len + 1) * 6, sizeof(char));
    WideCharToMultiByte(CP_UTF8, MB_ERR_INVALID_CHARS, in, -1, out, len, NULL,
NULL);
    return out;
}

It worked on wine. On wine it returns correctly converted string. On real
Windows it returns nothing, and empty string crashes the program.
After replasing MB_ERR_INVALID_CHARS with 0 it worked on both wine and Windows.

char* WcharToUTF8(wchar_t *in)
{
    uint64_t len = WideCharToMultiByte(CP_UTF8, 0, in, -1, NULL, 0, NULL,
NULL);
    char *out = (char*)calloc(len + 1, sizeof(char));
    WideCharToMultiByte(CP_UTF8, 0, in, -1, out, len, NULL, NULL);
    return out;
}

Also, the code was stolen from MSDN page about codepages, and there was a note
about "nothing will work correctly WITHOUT MB_ERR_INVALID_CHARS".

Windows bug? Wine bug? Wine did work as said in MSDN, Windows did not.