Bug#167409: glibc 2.3.1: breaks XEmacs builds; system breaks on revert to 2.2.5

[Daniel Jacobowitz <dan@debian.org>]

severity 167409 important
thanks

I'm not going to comment on the dumper problem, since I haven't looked
at it; the dumper has a history of being grossly non-portable, I'm not
surprised to see it break.  I want to explain something to you about
severity and compatibility, though.

On Sat, Nov 02, 2002 at 03:42:17PM +0900, Stephen J. Turnbull wrote:
> Package: glibc
> Version: 2.3.1
> Severity: critical
> 
> ... and yes, it is "critical", even if it only affects Emacs
> maintainers.  When it manifests, it's quite possible that the whole
> system will break.

> The real problem is that if you try to back up to glibc 2.2.5 (and I
> assume other earlier releases), you get an unusable system because
> tar, and therefore dpkg, breaks, complaining that "required GLIBC_2.3"
> is not available.  (That error message is probably inaccurate, but
> _you_ figure it out; I'm not going to rebreak my system to reproduce
> it.  Dammit, for libc, of all packages, it is not acceptable to break
> backward compatibility, even if upstream does!  There always has to be
> the escape hatch of reversion to previous.)  So do all the basic
> system utilities that aptitude upgraded at the same time.

First of all, you're misusing the term "backward compatibility".  Glibc
has a better track record than just about any other library for
backward compatibility: the ability to run things which were built
against an earlier version against the new version.

You're talking about _forward_ compatibility.  If we're going to
preserve forward compatibility, we might as well stop developing the
library.  It is absolutely impossible to add new functions, change the
size of data structures, change semantics, etc. without breaking
forward compatibility.  And we've never claimed you could do this.

There are some packages in the archive whose dependencies don't reflect
this properly right now.  They were built against a buggy version which
claimed to be compatible with 2.2.5.  We've fixed it and packages will
eventually be rebuilt.

The error message is precisely accurate.  The rebuilt tar binary
_REQUIRES_ glibc 2.3.  If you downgrade it by hand it's your own neck
on the line.

-- 
Daniel Jacobowitz
MontaVista Software                         Debian GNU/Linux Developer