RFC: requiring GCC >= 4.7 to build glibc

[Joseph Myers]

On Mon, 24 Aug 2015, Joseph Myers wrote:

> On Mon, 24 Aug 2015, David Miller 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).)

And, in light of 
<https://sourceware.org/ml/libc-alpha/2015-09/msg00749.html>, what would 
your views be on version upgrades for particular architectures when needed 
to add new ABIs (__float128 support for powerpc64le and possibly other 
hard-float powerpc variants), given that such version requirements might 
be much stronger than a requirement for 4.7 (as in, no current released 
GCC version yet has the __float128 support for powerpc)?

Note that I think a 4.7 requirement brings *more* benefits than most such 
single-version increments of the minimum GCC version.  And annual 
increases in the required version do *not* require glibc developers to 
upgrade the GCC version they use to build glibc annually, but only about 
once every four years (if someone moves from 4.6 to 5.x now, they wouldn't 
need to upgrade again until the required version reaches 6.x).

-- 
Joseph S. Myers
joseph@codesourcery.com