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Re: strxfrm output stability
- From: Paul Eggert <eggert at cs dot ucla dot edu>
- To: Florian Weimer <fweimer at redhat dot com>, Roland McGrath <roland at hack dot frob dot com>
- Cc: GNU C Library <libc-alpha at sourceware dot org>
- Date: Tue, 8 Sep 2015 14:35:16 -0700
- Subject: Re: strxfrm output stability
- Authentication-results: sourceware.org; auth=none
- References: <55EF4F95 dot 4020703 at redhat dot com> <20150908211805 dot 36E5E2C3A73 at topped-with-meat dot com> <55EF529E dot 7070108 at redhat dot com>
Florian Weimer wrote:
I don't see this documented anywhere
Exactly. Because the behavior is undocumented, applications cannot rely on
strxfrm calls being stable from one process to the next.
The manual suggests to store the strxfrm output and use it for sorting.
I expect that some applications put it into on-disk database indexes as
a result. This will lead to subtle breakage on glibc updates.
I'll go out on a limb and say that no sane application uses strxfrm, either on
disk or off. As far as I can tell, strxfrm is an invention of the C
standardization committee and is useless in real-world applications. So as a
practical matter it is not a big deal as to how stable it is.