strxfrm output stability

[Joseph Myers]

On Wed, 9 Sep 2015, Florian Weimer wrote:

> On 09/08/2015 11:33 PM, Joseph Myers wrote:
> > On Tue, 8 Sep 2015, Florian Weimer wrote:
> > 
> >> Why is it acceptable to change the strxfrm output between glibc
> >> releases, as implied by several bug reports (e.g. bug 18927)?  Doesn't
> >> this break backwards compatibility in a major way?
> > 
> > I think strxfrm output is much like the layout of lots of internal types - 
> > it's valid within a process (as long as LC_COLLATE is the same at both 
> > calls), but not necessarily stable over time (type sizes, alignment, 
> > offsets of public fields etc. need to be stable, but the internal layout 
> > of an opaque type need not be).  It's inevitable that fixing incorrect 
> > collation, updating collation for new national and international standards 
> > and for new Unicode characters, etc. will involve changing the output.
> 
> Okay, fair enough.  Can we put this into the documentation?

I think it would be reasonable to include this information in the 
documentation of collation (as well as referring to the issue in 
documentation for distributors).

-- 
Joseph S. Myers
joseph@codesourcery.com