Re: Minimum GCC version for building glibc

[Mike Frysinger <vapier at gentoo dot org>]

On 31 Oct 2014 14:03, Joseph S. Myers wrote:
> Currently the minimum GCC version for building glibc is 4.4.  I propose 
> that we increase this to either 4.6 or 4.7.  (Release branches before 4.8 
> are no longer maintained, but I don't propose 4.8 as a minimum.)

4.8 is way too recent imo at this time.

> If we require at least 4.7 that means various C11 features are available, 
> and __atomic_* (as discussed, we may not want to use __atomic_* on all 
> architectures, but with 4.7 __atomic_* will be available for use when 
> desired).  Whatever version we choose, __GNUC_PREREQ conditionals in 
> non-installed files not shared with gnulib or other projects would be 
> removed if no longer relevant with the new minimum requirement.
> 
> Questions:
> 
> * Should 4.6 or 4.7 be the minimum?

i tend to prefer to maintain older compatibility when possible.  gcc-4.7 was 
released in Mar 2012.  when we drop support for older versions, i think a 
prerequisite should be: what does dropping the older version gain us ?  when i 
look at the body of code using __GNUC_PREREQ, i see very few hits for <4.7.

you mentioned that we might want to use __atomic_* for some arches.  so if we 
aren't requiring 4.7, what's the diff between 4.4 and 4.6 ?

> * Should we give a recommendation for a specific version or "X or newer", 
> or just specify the minimum without a separate recommendation?  
> Experience says the recommendation gets out of date (I don't think 4.6 is 
> really likely that widely used for building glibc now), and none of the 
> other components come with such a recommendation in install.texi.

it does help indicate to people which versions are heavily tested, but that only 
matters if we think people are actually reading the install notes :).
-mike

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