The GNU C Library will be rebased in F21 to match glibc 2.20.

[Josh Boyer]

On Thu, Jul 31, 2014 at 12:34 PM, Siddhesh Poyarekar
<siddhesh at redhat.com> wrote:
> On Thu, Jul 31, 2014 at 03:06:00PM +0100, Richard W.M. Jones wrote:
>> However the previous problem(s -- multiple) was glibc using
>> non-Rawhide for integration testing, especially just while we were
>> trying to stablise Fedora for a release:
>>
>> https://lists.fedoraproject.org/pipermail/devel/2011-October/158440.html
>> https://lists.fedoraproject.org/pipermail/devel/2011-October/158662.html
>
> We're absolutely not going to rebase master in non-rawhide.  Our
> intention is to get glibc 2.20 release out before Fedora turns beta.
>
>> But 2.20 is a stable branch, right?  So this shouldn't be a concern
>> now.
>
> Yes, it is in what we call, a slushy freeze right now.  Changes going
> in are mostly regression fixes and other fixes that should not have
> any generated code impact.  There is however one change that the s/390
> folks will find painful - s/390 broke ABI in 2.19 without a proper
> justification and that is now going to be reverted in 2.20 (and in
> 2.19, but we don't really care about 2.19 right now).

To expand on this just a bit, the s/390 ABI break was done by the
s/390 glibc port maintainers and was done intentionally.  This wasn't
a "oops, we accidentally broke the ABI" bug.  It was something the
s/390 maintainers decided was of minimal concern and it turns out they
were wrong.  In my experience, glibc goes above and beyond maintaining
their software.  This s/390 incident is an anomaly in an otherwise
very controlled and well-run software project.

josh