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Re: GCC version bikeshedding
- From: Marek Polacek <polacek at redhat dot com>
- To: Richard Biener <richard dot guenther at gmail dot com>
- Cc: Jakub Jelinek <jakub at redhat dot com>, Eric Botcazou <ebotcazou at libertysurf dot fr>, Ian Lance Taylor <iant at google dot com>, GCC Development <gcc at gcc dot gnu dot org>, Jason Merrill <jason at redhat dot com>
- Date: Wed, 6 Aug 2014 11:10:21 +0200
- Subject: Re: GCC version bikeshedding
- Authentication-results: sourceware.org; auth=none
- References: <20140720165506 dot GT3003 at laptop dot redhat dot com> <201407291845 dot 14107 dot ebotcazou at libertysurf dot fr> <CAKOQZ8whj_m9yjYVdX_p24ocV25VRZwwmTf=VvGjEoxNeHbxSg at mail dot gmail dot com> <201408060925 dot 48414 dot ebotcazou at libertysurf dot fr> <20140806074223 dot GY7393 at tucnak dot redhat dot com> <CAFiYyc1+LTfbPF=nT3O4pA4ST6Z2X5FJ0ywMxL9bk3UsqwnV2w at mail dot gmail dot com> <20140806084803 dot GB7393 at tucnak dot redhat dot com> <CAFiYyc0+YgrRA-CheSFx5not6XadTWOa-mr_LWpX4sZ_gQMgdg at mail dot gmail dot com>
On Wed, Aug 06, 2014 at 11:04:14AM +0200, Richard Biener wrote:
> On Wed, Aug 6, 2014 at 10:48 AM, Jakub Jelinek <jakub@redhat.com> wrote:
> > - libstdc++ ABI changes (it is a significant user visible change,
> > if you rebuild everything, no extra effort is needed, but otherwise
> > if you want some C++ code built with older compilers work together
> > with code built with newer compilers, it might require source code
> > changes (the abi_tag attribute additions where needed and warning
> > suggest to put those at), at least that is my current understanding
> > of the plans
>
> But that's only with -std=c++11? Which had no compatibility
> guarantees before?
>
> > - likely libgfortran ABI changes (different array descriptors)
>
> Let's wait and see ...
>
> We'll find a good reason to bump the major with every release.
> Like for 4.9 LTO defaults to slim-objects, or C++ rejecting even more
> invalid code, or libstdc++ header re-orgs, or defaulting to dwarf4+
> (or even support for it), or VTA, or ...
>
> Where do we set the barrier? GCC isn't a C++ (or Fortran) compiler
> only.
>
> So if we change to 5.1 (please not .0) then let's switch the default
> optimization level to -O2! _That's_ a user-visible change across
> the board.
I'm planning to move the default C standard from gnu90 to gnu11
(Currently it's blocked on the -Wc90-c99-compat warning).
That's a pretty big user-visible change as well, I suppose.
Marek