raise(-1) has stopped returning an error recently
Sat Nov 27 07:24:02 GMT 2021
On 2021-11-25 05:54, Corinna Vinschen via Cygwin wrote:
> On Nov 24 11:01, Brian Inglis via Cygwin wrote:
>> On 2021-11-24 02:25, Corinna Vinschen via Cygwin wrote:
>>>> On Tue, Nov 23, 2021 at 11:18:25AM -0700, Brian Inglis wrote:
>>>>> Do Cygwin and/or Windows support surrogate pairs in UTF-8?
>>> You mean UTF-16. UTF-8 doesn't know surrogate pairs, UTF-16 does.
>>> Originally there was UCS-2, 16 bits, with only 65536 code points.
>>> However, Unicode left the BMP already with version 2.0 in 1996, so
>>> UTF-16 and surrogate pairs became necessary. Windows as well as Cygwin
>>> support them.
>> How does Cygwin support UTF-16 locales with surrogate pairs?
> UTF-16 locales? There's no such thing. UTF-16 is just the 16 bit
> representation for Unicode, and as such, is independent of the locale.
> On the user side, Cygwin only supports UTF-8 as Unicode representation.
> Internally you can then convert them to wchar_t which is UTF-16.
>> Are they the "native" locales inherited from Windows if others are not
>> specified e.g. UTF-8, some OEM SBCS or MBCS?
> Just try `locale -av' and you'll see all supported locales and their
> respective default codeset. All of them can be used with .utf8
> specifier to use UTF-8 instead of the default codeset. Some of them
> use UTF-8 as default codeset anyway, e. g., fa_IR or yo_NG.
>>>> There are 3 tests in surrogate-pair and only the 3rd one failed. So I guess
>>>> surrogate pairs in UTF-8 "mostly work".
>>> UTF-16. The surrogate stuff is evil at times. Have a look at the
>>> __utf8_wctomb function in
>>> Lone surrogate halfs in an input stream are a problem, for instance.
>> Thus the confusion with grep surrogate pair tests which appear to be running
>> under a UTF-8 locale: see attached surrogate pair extract from cygport
>> --debug grep.cygport check.
> An STC in plain C might be helpful.
I think I might finally have got the point of the test, not knowing much
about legacy UTF-16 UCS encoding nor surrogate pairs.
From what I can see:
𐐅 U+010405 f0 90 90 85 DESERET CAPITAL LETTER LONG OO
fails to match itself, presumably others do also.
Presumably this is converted internally on some platforms, including
Cygwin, to a UTF-16 surrogate pair, and a grep comparison fails,
although a bash comparison succeeds.
$ printf '\U10405\n' | iconv -f utf-8 -t utf-16be | xxd -g2
00000000: d801 dc05 000a
$ printf '\U10405\n' > t
$ grep -f t t; echo $?
$ oo=`printf '\U10405\n'`; [ $oo = $oo ] && echo same || echo diff
Take care. Thanks, Brian Inglis, Calgary, Alberta, Canada
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