msvcrt: Implement _wperror

[Piotr Caban]

On 06/21/16 12:37, Hugh McMaster wrote:
> On Tuesday, 21 June 2016 7:04 PM UTC+10, Piotr Caban wrote:
>> This is not how the function works. It shouldn't print wchar_t string to
>> stderr. Probably the simplest implementation is to convert input
>> parameter and call _perror (CP_ACP is not the correct encoding, you can
>> use MSVCRT_wcstombs).
>
> I don't understand. The MSDN page [1] contradicts your statement.
> "The perror function prints an error message to stderr. _wperror is a wide-character version
> of _perror; the string argument to _wperror is a wide-character string. _wperror and _perror
> behave identically otherwise."
The function is not writing wide-characters to stderr. It can be easily 
tested, e.g. do something like this:
freopen("test.txt", "wb", stderr);
errno = 3;
_wperror(L"test");
and see what's in the file when run on Windows/with your implementation. 
It will also display incorrectly when _wperror is run inside wine's cmd 
window.

> Also, if we convert the wide string to multibyte, there is a risk any non-Unicode characters
> supplied as input will not display correctly. So, IMHO converting to a multibyte string is a
> bad approach.
This is something that is worth testing. Anyway the conversion needs to 
be done.

> Still, if that's what you want, I'll do it.
I want the function to be implemented correctly.

Thanks,
Piotr