RE: GCC selftest improvements

["Gabriel Dos Reis via gcc" <gcc@gcc.gnu.org>]

| -----Original Message-----
| From: Andrew Pinski <pinskia@gmail.com>
| Sent: Monday, October 28, 2019 2:52 PM
| To: Jakub Jelinek <jakub@redhat.com>
| Cc: Jeff Law <law@redhat.com>; Segher Boessenkool
| <segher@kernel.crashing.org>; Gabriel Dos Reis <gdr@microsoft.com>;
| Andrew Dean <Andrew.Dean@microsoft.com>; David Malcolm
| <dmalcolm@redhat.com>; gcc@gcc.gnu.org; ro@CeBiTec.Uni-Bielefeld.DE;
| mikestump@comcast.net; jason@redhat.com; Jonathan Wakely
| <cxx@kayari.org>
| Subject: Re: GCC selftest improvements
| 
| On Mon, Oct 28, 2019 at 2:47 PM Jakub Jelinek <jakub@redhat.com> wrote:
| >
| > On Mon, Oct 28, 2019 at 03:41:13PM -0600, Jeff Law wrote:
| > > On 10/28/19 2:27 PM, Segher Boessenkool wrote:
| > > > On Mon, Oct 28, 2019 at 01:40:03PM -0600, Jeff Law wrote:
| > > >> On 10/25/19 6:01 PM, Gabriel Dos Reis wrote:
| > > >>> Jason, Jonathan - is the situation on the terrain really that dire that
| C++11 (or C++14) isn't at all available for platforms that GCC is bootstrapped
| from?
| > > >> The argument that I'd make is that's relatively uncommon (I know, I
| know
| > > >> AIX) that bootstrapping in those environments may well require first
| > > >> building something like gcc-9.
| > > >>
| > > >> I'd really like to see us move to C++11 or beyond.  Sadly, I don't think
| > > >> we have any good mechanism for making this kind of technical
| decision
| > > >> when there isn't consensus.
| > > >
| > > > Which GCC version will be required to work as bootstrap compiler?  Will
| > > > 4.8.5 be enough?
| > > I'd say gcc-9.  What would we gain by making it 4.8 or anything else
| > > that old?
| >
| > That is not a good idea, it will make it much harder to build gcc because
| > not everybody has gcc-9 built as a system compiler.
| > The previous minimum requirement of 4.1 is perhaps too old now that 4.8
| is
| > something we could require and gain through that C++11 support, but we
| > shouldn't follow Rust with "you can only build it with 6 weeks old previous
| > release and nothing else".
| > As discussed earlier, we gain most through C++11 support, there is no need
| > to jump to C++17 or C++20 as requirement.
| 
| Just a quick note.
| RHEL/CentOS 7 uses GCC 4.8 as the system compiler.  Requiring a new
| compiler to compile GCC 10 will not work for me.
| I normally bootstrap GCC 10 and then build a GCC 10 cross compiler.
| Having to have an extra compiler inbetween is problematic for me.
| 
| Thanks,
| Andrew

I would think C++14 gives you a good compromise, as you have access to key C++11 functionalities with a less crippled constexpr support.

-- Gaby