[PATCH] wchar.h: tweak wcwidth prototype parameter wchar_t -> wint_t

[Thomas Wolff]

Hi Brian,

Am 31.05.2026 um 05:50 schrieb Brian Inglis via Cygwin:
> On 2026-05-28 22:58, Thomas Wolff wrote:
>> to make it compliant with newlib and the manual page;
>> fixes cases of wrong width calculation:
>> https://cygwin.com/pipermail/cygwin/2026-April/259597.html
>> as mentioned in
>> https://cygwin.com/pipermail/cygwin/2026-May/259734.html
>> as described in
>> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=125451#c14
> > attachment: 
> 0001-wchar.h-tweak-wcwidth-prototype-parameter-wchar_t-wi.patch
>
> The existing wcwidth declaration in newlib/libc/include/wchar.h agrees 
> with
> POSIX 8 SUS V5.
>
> It is the man doc, definition, and implementation in
> newlib/libc/string/wcwidth.c which need changed to match the 
> specification and return codes in:
>
>     https://pubs.opengroup.org/onlinepubs/9799919799/functions/wcwidth.html
Your argument overlooks one significant deviation: in POSIX, wchar_t has 
32 bits, in cygwin only 16.
So to make wcwidth work for *all* Unicode character code points, the 32 
bit version must be used.
I tested positively that this fixes the broken test case with gcc 16 I 
had reported to the cygwin list.