From: Matthias Kretz <m.kretz@gsi.de>
To: <gcc-patches@gcc.gnu.org>, Jason Merrill <jason@redhat.com>
Subject: Re: [PATCH] Add gnu::diagnose_as attribute
Date: Thu, 1 Jul 2021 11:28:23 +0200 [thread overview]
Message-ID: <2984128.Mn6ktlgx0N@excalibur> (raw)
In-Reply-To: <e30fc933-f1c5-0baa-691c-4ba0b726e2c6@redhat.com>
On Tuesday, 22 June 2021 22:12:42 CEST Jason Merrill wrote:
> On 6/22/21 4:01 PM, Matthias Kretz wrote:
> > On Tuesday, 22 June 2021 21:52:16 CEST Jason Merrill wrote:
> >> For alias templates, you probably want the attribute only on the
> >> templated class, not on the instantiations.
> >
> > Oh good point. My current patch does not allow the attribute on alias
> > templates. Consider:
> >
> > template <class T, class U>
> >
> > struct X {};
> >
> > template <class T>
> >
> > using foo [[gnu::diagnose_as]] = X<T, int>;
> >
> > I have no idea how this could work. I would have to set the attribute for
> > an implicit partial specialization (not that I know of the existence of
> > such a thing)? I.e. X<int, int> would have to be diagnosed as foo<int>,
> > but X<int, float> would have to be diagnosed as X<int, float>, not foo.
> >
> > So if anything it should only support alias templates if they are strictly
> > "renaming" the type. I.e. their template parameters must match up exactly.
> > Can I constrain the attribute like this?
>
> Yes. You can check that with get_underlying_template.
>
> Or you could support the above by putting the attribute on the
> instantiation with the TEMPLATE_INFO for foo<A> rather than a simple name.
Question, given:
template <class T> using foo = bar<T>;
The diagnose_as attribute handler isn't called until e.g. `foo<int>` is
instantiated. Meaning that even after the declaration of the alias template
`bar<int>` will not be diagnosed as `foo<int>`, which happens only after the
first use of `foo<int>`. I find that more confusing than helpful, even if the
expectation would be that users only use the alias template.
So do you still expect alias templates to support diagnose_as? And if yes, how
could I handle the attribute so that the diagnose_as attribute is applied to
`bar` on declaration of `foo`?
--
──────────────────────────────────────────────────────────────────────────
Dr. Matthias Kretz https://mattkretz.github.io
GSI Helmholtz Centre for Heavy Ion Research https://gsi.de
std::experimental::simd https://github.com/VcDevel/std-simd
──────────────────────────────────────────────────────────────────────────
next prev parent reply other threads:[~2021-07-01 9:28 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <14205410.xuKvIAzr1H@excalibur>
[not found] ` <20210427094648.GL3008@redhat.com>
2021-05-04 11:13 ` Matthias Kretz
2021-05-04 13:34 ` David Malcolm
2021-05-04 14:23 ` Matthias Kretz
2021-05-04 14:32 ` Matthias Kretz
2021-05-04 19:00 ` David Malcolm
2021-05-04 19:22 ` Matthias Kretz
2021-05-14 16:05 ` Martin Sebor
2021-05-26 21:33 ` Matthias Kretz
2021-05-27 17:39 ` Jason Merrill
2021-05-27 18:54 ` Matthias Kretz
2021-05-27 21:15 ` Jason Merrill
2021-05-27 22:07 ` Matthias Kretz
2021-05-28 3:05 ` Jason Merrill
2021-05-28 7:42 ` Matthias Kretz
2021-06-01 19:12 ` Jason Merrill
2021-06-01 21:01 ` Matthias Kretz
2021-06-11 10:01 ` Matthias Kretz
2021-06-15 15:51 ` Jason Merrill
2021-06-15 20:56 ` Matthias Kretz
2021-06-16 0:48 ` Jason Merrill
2021-06-22 7:30 ` Matthias Kretz
2021-06-22 19:52 ` Jason Merrill
2021-06-22 20:01 ` Matthias Kretz
2021-06-22 20:12 ` Jason Merrill
2021-07-01 9:28 ` Matthias Kretz [this message]
2021-07-01 15:18 ` Jason Merrill
2021-07-05 14:18 ` Matthias Kretz
2021-07-07 22:34 ` Jason Merrill
2021-07-07 8:23 ` Matthias Kretz
2021-07-08 1:19 ` Jason Merrill
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