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Message-ID: <a985ce12-d9a0-4eaa-9ccd-85cffdf15994@maxrnd.com>
Date: Mon, 29 Sep 2025 15:52:46 -0700
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Subject: Re: cygwin 3.6.4 breaks mbrtowc
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From: Mark Geisert via Cygwin <cygwin AT cygwin DOT com>
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Hello Thomas,
Apologies for the late response to your report.

On 7/21/2025 8:25 PM, Thomas Wolff via Cygwin wrote:
> mbrtowc is broken in 3.6.4 which breaks non-BMP display in mintty.
> Test case below.
> Thomas
> 
> #include <locale.h>
> #include <wchar.h>
> #include <stdio.h>
> 
> void mb(unsigned char c)
> {
>    wchar_t wc;
>    int ret = mbrtowc(&wc, &c, 1, 0);
>    printf("%02X -> %04X : %d\n", c, wc, ret);
> }
> 
> void main ()
> {
>    setlocale (LC_CTYPE, "");
> 
>    mb(0xF0);
>    mb(0x9F);
>    mb(0x98);
>    mb(0x8E);
> }

Running your testcase gives different output between 3.6.4 and 
3.7.0-dev-139 but I'm unsure the latter is correct.  Can you comment please?

On 3.6.4:
~ ./a
F0 -> 0000 : -2
9F -> 0000 : -2
98 -> 0000 : -2
8E -> D83D : 3

On 3.7.0-dev-139:
~ ./a
F0 -> 0000 : -2
9F -> 0000 : -2
98 -> D83D : 1
8E -> DE0E : 1

Thanks much,

..mark

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