RFC: requiring GCC >= 4.7 to build glibc

[Carlos O'Donell]

On 10/05/2015 07:36 AM, Joseph Myers wrote:
>>> From: Joseph Myers <joseph@codesourcery.com> Date: Mon, 24 Aug
>>> 2015 20:28:34 +0000
>>> 
>>>> Would anyone else like to comment on (a) the general principle
>>>> of doing time-based upgrades of the minimum GCC and binutils
>>>> versions for building glibc (so typically upgrade every other
>>>> glibc release cycle, since GCC and binutils have major releases
>>>> about once a year) or (b) this particular proposed increase?
>>> 
>>> It can be a pain to upgrade gcc, and in fact for me this is much 
>>> harder than updating the kernel for example.  If I upgrade gcc
>>> it effects all of my development work, not just the work I do
>>> with glibc.
>> 
>> What criteria would you like for the minimum GCC version for
>> building glibc?
> 
> I haven't seen any responses to this question.  Would those opposed
> to the 4.7 upgrade at this time in particular, or to my proposed
> principle of time-based upgrades of the minimum GCC version in
> general, like to propose alternative criteria?  (E.g., "the current
> long-term-support releases of GNU/Linux distributions X, Y and Z
> should include a suitable GCC version" - or "support for release N
> can be dropped once release N+5 is out" (which would imply dropping
> 4.6 support when GCC 6 is out).)

I know you already checked in these changes, but I wanted to comment.

For Fedora this is largely a non-issue. The distribution cycles every 6 months
and we have new enough compilers across aarch64, arm, x86_64, i686, ppc, ppc64,
ppc64le, s390, and s390x, that glibc builds just fine.

On RHEL the question is more complicated. Right now I routinely test glibc
on RHEL5, RHEL6 and RHEL7 (the three major commercially supported releases).
On RHEL5 I use Developer Toolset (DTS) 2.0 which is our non-system compiler
based on gcc 4.8.2. Similarly on RHEL6 and RHEL7 I can use DTS which comes
with a newer tools including binutils and gdb.

It would be problematic only if glibc were to require gcc 4.9 or greater.

Cheers,
Carlos.