DMARC-Filter:	OpenDMARC Filter v1.4.2 delorie.com 56OFaBCr1498048
Authentication-Results:	delorie.com; dmarc=pass (p=none dis=none) header.from=cygwin.com
Authentication-Results:	delorie.com; spf=pass smtp.mailfrom=cygwin.com
DKIM-Filter:	OpenDKIM Filter v2.11.0 delorie.com 56OFaBCr1498048
Authentication-Results:	delorie.com;
	dkim=pass (1024-bit key, unprotected) header.d=cygwin.com header.i=@cygwin.com header.a=rsa-sha256 header.s=default header.b=O4vI+gvS
X-Recipient:	archive-cygwin AT delorie DOT com
DKIM-Filter:	OpenDKIM Filter v2.11.0 sourceware.org 78768385AC1C
DKIM-Signature:	v=1; a=rsa-sha256; c=relaxed/relaxed; d=cygwin.com;
	s=default; t=1753371370;
	bh=1VV2KOOYyFMN65fDRJReSvQOvlpPcu4M4PdvHa82PyE=;
	h=Date:To:Subject:References:In-Reply-To:List-Id:List-Unsubscribe:
	List-Archive:List-Post:List-Help:List-Subscribe:From:Reply-To:Cc:
	From;
	b=O4vI+gvSYTbCW+R6kNr6obVKFPobHqGXwAMJgc+HaYg1Sd4eIMNMB2itiFq8FjGqn
	+F/y7OU48E6H2XwgR/VtU6dtv05PnCYx1wCo3sD0dXg6AkzgYRo5Nz9jDq25f8iRun
	bJ4PYKX9YdW52Tu3Qn42j/+ziSsjlHy8UiFBZ1k4=
X-Original-To:	cygwin AT cygwin DOT com
Delivered-To:	cygwin AT cygwin DOT com
Date:	Thu, 24 Jul 2025 17:35:06 +0200
To:	Thomas Wolff <towo AT towo DOT net>
Subject:	Re: readdir() returns inaccessible name if file was created with
	invalid UTF-8
Message-ID:	<aIJSqk4abV6QdeVS@calimero.vinschen.de>
Mail-Followup-To:	Thomas Wolff <towo AT towo DOT net>, cygwin AT cygwin DOT com
References:	<96f2253b-791b-b8a0-97dd-8d257eefb9b1 AT t-online DOT de>
	<03c4fae7-7322-572c-ae72-52e300f0b438 AT t-online DOT de>
	<aFxRfI4NdZ8y5IlK AT calimero DOT vinschen DOT de>
	<f78c615c-aefe-b3d0-aada-5f9d0cf73a0a AT t-online DOT de>
	<aF5y15iQ840LxLYJ AT calimero DOT vinschen DOT de>
	<ca205dbd-907f-4552-9e5c-2cb0050f83a3 AT towo DOT net>
	<aH-MtwqARmDmLwoo AT calimero DOT vinschen DOT de>
	<91f26856-72b0-483b-8d04-bd90a27b6be0 AT towo DOT net>
	<4ab2c1b7-3164-4556-ba36-29814ecf5766 AT towo DOT net>
	<68f65634-8f4e-436b-ba6a-d30bdf882aaa AT towo DOT net>
MIME-Version:	1.0
In-Reply-To:	<68f65634-8f4e-436b-ba6a-d30bdf882aaa@towo.net>
X-BeenThere:	cygwin AT cygwin DOT com
X-Mailman-Version:	2.1.30
List-Id:	General Cygwin discussions and problem reports <cygwin.cygwin.com>
List-Unsubscribe:	<https://cygwin.com/mailman/options/cygwin>,
	<mailto:cygwin-request AT cygwin DOT com?subject=unsubscribe>
List-Archive:	<https://cygwin.com/pipermail/cygwin/>
List-Post:	<mailto:cygwin AT cygwin DOT com>
List-Help:	<mailto:cygwin-request AT cygwin DOT com?subject=help>
List-Subscribe:	<https://cygwin.com/mailman/listinfo/cygwin>,
	<mailto:cygwin-request AT cygwin DOT com?subject=subscribe>
From:	Corinna Vinschen via Cygwin <cygwin AT cygwin DOT com>
Reply-To:	cygwin AT cygwin DOT com
Cc:	Corinna Vinschen <corinna-cygwin AT cygwin DOT com>, cygwin AT cygwin DOT com
Errors-To:	cygwin-bounces~archive-cygwin=delorie DOT com AT cygwin DOT com
Sender:	"Cygwin" <cygwin-bounces~archive-cygwin=delorie DOT com AT cygwin DOT com>
X-MIME-Autoconverted:	from base64 to 8bit by delorie.com id 56OFaBCr1498048

Thomas,

On Jul 23 05:44, Thomas Wolff via Cygwin wrote:
> > > Am 22.07.2025 um 15:05 schrieb Corinna Vinschen:
> > > > mbrtowc() is inherently a bad idea when it comes to UTF-16. It's a
> > > > function which only works really correctly for the unicode base plane,
> > > > or if wchar_t is big enough.
> > > > 
> > > > It's the reason we don't use mbrtowc() if possible.  It's better
> > > > to call
> > > > mbstowcs() or friends and allow at least 3 chars in the wchar_t buffer.
> > > > You can't change that in mintty by any chance?
> > [...]
> OK, suppose I'd consider to switch to mbs[[n]r]towcs, collecting bytes until
> the function gives me a result.
> This would work fine as long as I receive only valid sequences. But look at
> input string test case
> char nonbmp[] = {0xF8, 0x88, 0x8A, 0xAF, 0x2D, 0}; // an invalid sequence
> followed by a valid char
> The functions only return -1 and (in the case of mbsnrtowcs) do not advance
> the input pointer.
> So how am I supposed to recognize that the invalid sequence has ended and a
> valid character has arrived?

Apart from that, you probably still have a problem in mintty: GB18030.

The problem with GB18030 is, that you need all four bytes to generate
the high surrogate.

Consider the following GB18030 string: 0x90 0x30 0x81 0x30

This string translates into a UTF-16 surrogate pair: 0xd800 0xdc00.

If you run a tweaked version of your test applicaton from
https://cygwin.com/pipermail/cygwin/2025-July/258513.html:

  setlocale (LC_CTYPE, "zh_CN.gb18030");
  mb (0x90);
  mb (0x30);
  mb (0x81);
  mb (0x30);

Then the output is:

  90 -> 0000 : -2
  30 -> 0000 : -2
  81 -> 0000 : -2
  30 -> D800 : 0

However, if you notice this situation...

  if (ret_from_mbrtowc == 0 && codeset == gb18030
      && (pwc & 0xfc00) == 0xd800)

...you can just add a fake NUL byte:

    mbrtowc (&wc, '\0', 1, &mbstate);

If you do that, the above sequence becomes:

  90 -> 0000 : -2
  30 -> 0000 : -2
  81 -> 0000 : -2
  30 -> D800 : 0
  00 -> DC00 : 1

I hope this helps, if you didn't already handle GB18030 differently
in mintty.


Corinna

-- 
Problem reports:      https://cygwin.com/problems.html
FAQ:                  https://cygwin.com/faq/
Documentation:        https://cygwin.com/docs.html
Unsubscribe info:     https://cygwin.com/ml/#unsubscribe-simple

- Raw text -