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From: "iains at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c++/60512] would be useful if gcc implemented __has_feature
 similarly to clang
Date: Tue, 09 May 2023 10:57:26 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D60512

--- Comment #19 from Iain Sandoe <iains at gcc dot gnu.org> ---
(In reply to Alex Coplan from comment #18)
> (In reply to Iain Sandoe from comment #16)
> >=20
> > AFAIR the main blocker to progress was trying to decide how to represen=
t the
> > target/language/language version dependencies of the features and exten=
sions
> > (there's a rudimentary scheme at the moment but it probably is not flex=
ible
> > enough)
>=20
> Can you elaborate on this a little? In particular I'd be interested to he=
ar
> about cases where the target matters.

the first commit in my WIP branch is "generic support" (i.e. features that =
are
[intended to be] common to all targets)

the second commit identifies a set of features that (I would want to be)
supported on Darwin, but maybe not relevant to other targets.

Of course, we hope the first set to be the largest.

Targets like Darwin and Windows are more likely to need such things - where
compatibility with external ABI and system tools means we're trying to comp=
ly
with design decisions out of our control.

However, it is presumably conceivable that (say) variable length vector
features could be relevant to aarch64 and risc-v but not elsewhere (I'm
speculating here, so no concrete example or evidence).=