Re: Minimum GCC version for building glibc

[Mike Frysinger <vapier at gentoo dot org>]

On 05 Nov 2014 21:08, Joseph Myers wrote:
> On Wed, 5 Nov 2014, Mike Frysinger wrote:
> > any time you use a gcc feature you must review to see if it's supported by the 
> > versions we support.  bumping the min gcc version doesn't preclude that.  if 
> 
> No (even if autoconf kept testing for ISO C90 features long after doing so 
> was unnecessary).  You just need to be aware of what's recent and not care 
> about the versions in which longstanding features were introduced - and 
> expanding the set of features that count as longstanding reduces the load 
> of keeping track of what's recent (you only need to review if using a 
> feature that might be on the borderline, and otherwise can either use 
> features without thinking about compiler versions, or know that a feature 
> is only usable conditionally, either of which is much more efficient than 
> needing to check).

i don't buy it.  we aren't talking about "long standing features" here, nor has 
it really come up before.  every request has been for a recentish feature.

> > > I think -Werror makes it more likely building with old versions will break 
> > > when they aren't actively tested.  We also now have a clear use for 
> > > diagnostic pragmas, new in 4.6, to allow more selective disabling of 
> > > particular warnings together with -Werror.
> > 
> > -Werror makes sense when building from git / maintainer mode, but not in any 
> > other scenario (such as unpacking release tarballs and running plain configure).
> 
> Defaulting to disabling -Werror for releases (or based on compiler 
> version) was previously objected to in 
> <https://sourceware.org/ml/libc-alpha/2012-08/msg00404.html>.

as long as there is a --disable-werror flag, i don't care about the default.  no 
release is every going to build warning free in all configurations.  it isn't 
just a gcc version skew issue.

> > so your argument hinges on whether the new atomic logic should require gcc 4.7.  
> > that should probably shake out in the relevant threads and once it has, you've 
> > got a compelling reason for dropping <4.7.  but i still don't see any 
> > justification for, if we are retaining 4.6, why we should drop 4.4 & 4.5.
> 
> It's already been stated - using #pragma GCC diagnostic push/pop to help 
> with -Werror usage.

OK
-mike

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