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Subject: Re: Bug in collation functions?
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References: <20151029075050.GE5319@calimero.vinschen.de> <20151029083057.GH5319@calimero.vinschen.de> <56321815.7000203@cornell.edu> <20151029153516.GJ5319@calimero.vinschen.de> <56323F2E.4030807@cornell.edu> <56324598.9060604@cornell.edu> <56324E82.7000402@redhat.com> <563268A4.6000005@cornell.edu> <56329462.2090206@cornell.edu> <56329BE8.808@cornell.edu> <20151030120320.GO5319@calimero.vinschen.de>
From: Ken Brown <kbrown@cornell.edu>
Message-ID: <56337996.2000400@cornell.edu>
Date: Fri, 30 Oct 2015 10:07:18 -0400
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Hi Corinna,

On 10/30/2015 8:03 AM, Corinna Vinschen wrote:
> On Oct 29 18:21, Ken Brown wrote:
>> The fallback I had in mind is to return the shorter string if they have
>> different lengths and otherwise to revert to wcscmp.
 >
> I had a longer look into this suggestion and the below code and it took
> me some time to find out what bugged me with it:
>
> What about str/wcsxfrm?
>
> Per POSIX, calling strcmp on the result of strxfrm is equivalent to
> calling strcoll (analogue with wcs*).  If you extend *coll to perform an
> extra check on the length, you will have cases in which the above rule
> fails.  You can't perform the length test on the result of *xfrm and
> expect the same result as in *coll.
>
> In fact, when calling LCMapStringW with NORM_IGNORESYMBOLS (you would
> have to do this anyway if we add this flag in *coll), the resulting
> transformed strings created from the input strings "11" and "1.1" would
> be identical, so a length test on the xfrm string is not meaningful at
> all.
>
> The bottom line is, afaics, we must make sure that CompareStringW and
> LCMapStringW are called the same way, and their result/output has to be
> returned to the caller.  Performing an extra check in *coll which can't
> be reliably performed in *xfrm is not feasible.
>
> Does that make sense?

Yes, I see the problem, and I don't see a good way around it.  So I 
think we probably have to leave things as they are and live with the 
fact that we can't do comparisons that ignore whitespace and punctuation.

The alternative of allowing str/wcscoll to return 0 on unequal strings 
doesn't seem feasible in view of Eric's comments.

What about the other issue I raised: Should setlocale return null to 
indicate an error if it's given an invalid locale name like en_DE.UTF-8?

Ken

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