Re: [PATCH] libnsl: Turn remaining symbols into compat symbols [BZ #22701]

[Florian Weimer <fweimer at redhat dot com>]

On 01/31/2018 12:21 PM, Szabolcs Nagy wrote:
> On 29/01/18 13:32, Florian Weimer wrote:
> > On 01/29/2018 02:30 PM, Andreas Schwab wrote:
> > > On Jan 11 2018, fweimer@redhat.com (Florian Weimer) wrote:
> > >
> > > >     [BZ #22701]
> > > >     * include/rpcsvc/nislib.h (__nis_default_ttl): Add
> > > >     libnsl_hidden_proto.
> > > >     * include/rpcsvc/yp.h (yp_xdrall): Declare with
> > > >     libnsl_hidden_proto.
> > > >     * include/rpcsvc/ypclnt.h (yp_maplist): Likewise.
> > > >     * nis/Makefile (libnsl-routines): Add nss-default only for
> > > >     build-obsolete-nsl.
> > > >     * nis/nis_defaults.c (__nis_default_ttl): Add
> > > >     libnsl_hidden_nolink_def.
> > > >     * nis/rpcsvc/ypclnt.h (yp_maplist): Remove #ifdef'ed-out
> > > >     declaration.
> > > >     * nis/yp_xdr.c (xdr_ypall): Add libnsl_hidden_nolink_def.
> > > >     * nis/ypclnt.c (yp_maplist): Likewise.
> > >
> > > Ok.
> >
> > Dmitry, is it okay to sneak this into glibc 2.27?  The change is 
> > mostly cosmetic; the important change was not installing libnsl.so and 
> > libnsl.a, and that is already on master.
>
> isn't this an internal abi break?

Not really, I think.

> if i install glibc-2.27 on top of an earlier glibc install
> without removing the previous libnss_nis.so.2, which references
> _nsl_default_nss, then the new libnsl.so.1 will not have that
> symbol so old libnss_nis.so.2 no longer works.
>
> either i have to --enable-obsolete-nsl in the new libc or
> remove the old libnss_nis.so.2 (and hope nothing needs it)
> before i run the new ldconfig.
>
> i thought 'installing over' previous libc is a valid use
> (i do this when testing in chroot)

A similar thing happens if you install a glibc over another glibc with 
different build flags, e.g. one that is using AT_PLATFORM directories.

We can certainly revert the change and reapply it for 2.28, maybe this 
time with a change which loads the NSS modules with RTLD_NOW, so that 
the missing GLIBC_PRIVATE symbol is detected at dlopen time and the NSS 
module is ignored (at least for now).

Thanks,
Florian