Re: hppa nptl switch

[Mike Frysinger <vapier@gentoo.org>]

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On Tuesday 01 September 2009 11:50:27 Aurelien Jarno wrote:
> Carlos O'Donell a écrit :
> > On Tue, Sep 1, 2009 at 2:08 AM, Aurelien Jarno<aurelien@aurel32.net> 
wrote:
> >> Frans Pop a écrit :
> >>> Carlos O'Donell wrote:
> >>>>> In practice it shouldn't be problem at all.
> >>>>> Debian should make sure that binary/library compiled
> >>>>> against NPTL-hppa-glibc will require NPTL-hppa-glibc
> >>>>> by proper Depends: line like "libc6 (>= 2.10)".
> >>>>
> >>>> Does every package have to do this? I'm not very familiar with all the
> >>>> packaging requirements.
> >>>
> >>> It is something that should automatically get done correctly as long as
> >>> the libc-dev package defines the minimum version that way.
> >>>
> >>> The mechanism that determines this is in
> >>> /var/lib/dpkg/info/libc6.shlibs. Currently this has lines like:
> >>>    libc 6 libc6 (>= 2.9)
> >>
> >> No, as glibc uses symbols files, this file is actually not used.
> >> Nevertheless it is still possible to resolve all symbols to libc6 (>=
> >> 2.10).
> >
> > Once an application is rebuilt against a new libc, what prevents the
> > user from downgrading libc and breaking the application?
>
> If we make sure that the new programs are using symbols from version
> GLIBC_2.10, the program should refuse to start with a lower version of
> the glibc.

i think the question was one about packaging rather than general use ?  if you 
build a package against a newer glibc version but it only uses older symbols, 
then in theory it should work fine with older glibc versions.  if the symbol 
changes between versions, then it should have corresponding symbol version 
changes as well (which will automatically be recorded in the binary).
-mike

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