From: Ken Brown <kbrown@cornell.edu>
To: cygwin@cygwin.com
Subject: Re: Bug in collation functions?
Date: Thu, 29 Oct 2015 21:58:00 -0000 [thread overview]
Message-ID: <563268A4.6000005@cornell.edu> (raw)
In-Reply-To: <56324E82.7000402@redhat.com>
On 10/29/2015 12:51 PM, Eric Blake wrote:
> On 10/29/2015 10:13 AM, Ken Brown wrote:
>
>> Never mind. My test case was flawed, because it didn't check for the
>> possibility that wcscoll might return 0. Here's a revised definition of
>> the "compare" function:
>>
>> void
>> compare (const wchar_t *a, const wchar_t *b, const char *loc)
>> {
>> setlocale (LC_COLLATE, loc);
>> int res = wcscoll (a, b);
>> char c = res < 0 ? '<' : res > 0 ? '>' : '=';
>> printf ("\"%ls\" %c \"%ls\" in %s locale\n", a, c, b, loc);
>> }
>>
>> With this change (and the use of NORM_IGNORESYMBOLS) the test returns
>> the following on Cygwin:
>>
>> $ ./wcscoll_test
>> "11" > "1.1" in POSIX locale
>> "11" = "1.1" in en_US.UTF-8 locale
>> "11" > "1 2" in POSIX locale
>> "11" < "1 2" in en_US.UTF-8 locale
>>
>> It still differs from Linux, but it's good enough to make the emacs test
>> pass. Moreover, this behavior actually seems more reasonable to me than
>> the Linux behavior. After all, if you're ignoring punctuation, how can
>> you decide which of "11" or "1.1" comes first?
>
> Careful. POSIX is proposing some wording that say that normal locales
> should always implement a fallback of last resort (and that locales that
> do not do so should have a special name including '@', to make it
> obvious). It is not standardized yet, but worth thinking about.
>
> http://austingroupbugs.net/view.php?id=938
> http://austingroupbugs.net/view.php?id=963
>
> The intent of that wording is that if ignoring punctuation could cause
> two strings to otherwise compare equal, the fallback of a total ordering
> on all characters means that the final result of strcoll() will not be 0
> unless the two strings are identical.
In that case, I think Cygwin should start by using NORM_IGNORESYMBOLS in
non-POSIX locales, with the goal of eventually moving toward emulating
glibc. I don't know what fallback glibc uses or how hard it would be to
implement this on Cygwin.
Here's a tangentially related issue, also motivated by a failing emacs
test: Should setlocale return null to indicate an error if it's given an
invalid locale name? This happens on Linux but not on Cygwin, as the
following modified test case shows:
$ cat wcscoll_test.c
#include <wchar.h>
#include <stdio.h>
#include <locale.h>
void
compare (const wchar_t *a, const wchar_t *b, const char *loc)
{
if (! setlocale (LC_COLLATE, loc))
printf ("Unable to set locale to %s\n", loc);
else
{
int res = wcscoll (a, b);
char c = res < 0 ? '<' : res > 0 ? '>' : '=';
printf ("\"%ls\" %c \"%ls\" in %s locale\n", a, c, b, loc);
}
}
int
main ()
{
compare (L"11", L"1.1", "POSIX");
compare (L"11", L"1.1", "en_US.UTF-8");
compare (L"11", L"1 2", "POSIX");
compare (L"11", L"1 2", "en_US.UTF-8");
compare (L"11", L"1 2", "en_DE.UTF-8");
}
On Cygwin (with NORM_IGNORESYMBOLS), the output is
"11" > "1.1" in POSIX locale
"11" = "1.1" in en_US.UTF-8 locale
"11" > "1 2" in POSIX locale
"11" < "1 2" in en_US.UTF-8 locale
"11" < "1 2" in en_DE.UTF-8 locale
but on Linux it is
"11" > "1.1" in POSIX locale
"11" < "1.1" in en_US.UTF-8 locale
"11" > "1 2" in POSIX locale
"11" < "1 2" in en_US.UTF-8 locale
Unable to set locale to en_DE.UTF-8
Ken
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next prev parent reply other threads:[~2015-10-29 18:42 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-10-29 7:41 Ken Brown
2015-10-29 7:50 ` Eric Blake
2015-10-29 12:58 ` Corinna Vinschen
2015-10-29 15:35 ` Corinna Vinschen
2015-10-29 15:51 ` Ken Brown
2015-10-29 16:14 ` Corinna Vinschen
2015-10-29 16:14 ` Ken Brown
2015-10-29 16:51 ` Ken Brown
2015-10-29 18:09 ` Eric Blake
2015-10-29 21:58 ` Ken Brown [this message]
2015-10-30 8:05 ` Ken Brown
2015-10-30 14:07 ` Ken Brown
2015-10-30 19:11 ` Corinna Vinschen
2015-10-30 19:14 ` Ken Brown
2015-10-30 21:13 ` Corinna Vinschen
[not found] ` <5634F6BA.7070301@cornell.edu>
2015-11-02 11:14 ` Corinna Vinschen
2015-10-29 16:17 ` Eric Blake
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