Re: Bug in collation functions?

[Ken Brown <kbrown@cornell.edu>]

On 10/29/2015 4:30 AM, Corinna Vinschen wrote:
> On Oct 29 08:50, Corinna Vinschen wrote:
>> On Oct 28 21:58, Eric Blake wrote:
>>> On 10/28/2015 04:14 PM, Ken Brown wrote:
>>>> It's my understanding that collation is supposed to take whitespace and
>>>> punctuation into account in the POSIX locale but not in other locales.
>>>
>>> Not quite right. It is up to the locale definition whether whitespace
>>> affects collation.  But you are correct that in the POSIX locale,
>>> whitespace must not be ignored in collation.
>>>
>>>> This doesn't seem to be the case on Cygwin.  Here's a test case using
>>>> wcscoll, but the same problem occurs with strcoll.
>>>
>>> That's because the locale definitions are different in cygwin than they
>>> are in glibc.  But it is not a bug in Cygwin; POSIX allows for different
>>> systems to have different locale definitions while still using the same
>>> locale name like en_US.UTF-8.
>>
>> Btw, strcoll and wcscoll in Cygwin are implemented using the Windows
>> function CompareStringW with the LCID set to the locale matching the
>> POSIX locale setting.  I'm rather glad I didn't have to implement this
>> by myself... :}
>
> OTOH, CompareString has a couple of flags to control its behaviour, see
> https://msdn.microsoft.com/en-us/library/windows/desktop/dd317761%28v=vs.85%29.aspx
>
> Right now Cygwin calls CompareStringW with dwCmpFlags set to 0, but there
> are flags like NORM_IGNORENONSPACE, NORM_IGNORESYMBOLS.  I'm open to a
> discussion how to change the settings to more closely resemble the rules
> on Linux.
>
> E.g.  wcscoll simply calls wcscmp rather than CompareStringW for the
> C/POSIX locale anyway.  So, would it makes sense to set the flags to
> NORM_IGNORESYMBOLS in other locales?

I think so.  That's what the native Windows build of emacs does in this 
situation.  (I came across the issue because one of the tests in the 
emacs test suite was failing on Cygwin.)

Ken


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