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Re: Minimum GCC version for building glibc
- From: Joseph Myers <joseph at codesourcery dot com>
- To: Mike Frysinger <vapier at gentoo dot org>
- Cc: Paul Eggert <eggert at cs dot ucla dot edu>, <libc-alpha at sourceware dot org>
- Date: Wed, 5 Nov 2014 18:57:16 +0000
- Subject: Re: Minimum GCC version for building glibc
- Authentication-results: sourceware.org; auth=none
- References: <Pine dot LNX dot 4 dot 64 dot 1410311352200 dot 4263 at digraph dot polyomino dot org dot uk> <20141104165815 dot GK5402 at vapier dot wh0rd dot info> <5459239B dot 4020901 at cs dot ucla dot edu> <20141105184731 dot GP5402 at vapier dot wh0rd dot info>
On Wed, 5 Nov 2014, Mike Frysinger wrote:
> we bump the min required version of any package for these reasons:
> - newer functionality is not feasible to duplicate in glibc
> - existing backwards compat code grows to a size that is too onerous to
> keep maintaining
- There is a combinatorial explosion of possible feature combinations, so
to make that more maintainable it makes sense to declare old versions
unsupported and avoid even needing to think about whether a feature you're
using existed in some old version few people will be using.
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.
> in this case, the proposal of raising gcc 4.4 to 4.7 was accompanied by "it
> might make implementing C11 support easier". it seems like support for that was
> already posted not requiring 4.7. so what's the reason for dropping 4.4/4.5 ?
Having two different ways to implement atomics on the same architecture,
unless justified by variations in hardware support, is another
contribution to that combinatorial explosion of configurations. Once
we're happy use of __atomic_* works well on any given architecture, I
think it should replace the old approach there (and so require 4.7 there)
rather than keeping an old and little-used alternative for building with
Joseph S. Myers