public inbox for gcc-patches@gcc.gnu.org
 help / color / mirror / Atom feed
From: Marek Polacek <polacek@redhat.com>
To: Jason Merrill <jason@redhat.com>
Cc: GCC Patches <gcc-patches@gcc.gnu.org>
Subject: Re: [PATCH v3] c++: Implement C++23 P2266R1, Simpler implicit move [PR101165]
Date: Tue, 27 Sep 2022 19:39:25 -0400	[thread overview]
Message-ID: <YzOJraytZZPJhmhJ@redhat.com> (raw)
In-Reply-To: <39fb63d9-8128-512b-523d-f575317cf7c2@redhat.com>

On Tue, Sep 27, 2022 at 05:44:12PM -0400, Jason Merrill wrote:
> On 9/27/22 16:26, Marek Polacek wrote:
> > --- a/gcc/cp/typeck.cc
> > +++ b/gcc/cp/typeck.cc
> > @@ -11042,8 +11042,13 @@ check_return_expr (tree retval, bool *no_warning)
> >   	 the conditions for the named return value optimization.  */
> >         bool converted = false;
> >         tree moved;
> > -      /* This is only interesting for class type.  */
> > -      if (CLASS_TYPE_P (functype)
> > +      /* Until C++23, this was only interesting for class type...  */
> > +      if ((CLASS_TYPE_P (functype)
> > +	   /* ...but in C++23, we should do the below when we're converting
> > +	      from/to a class/reference (a non-scalar type).  */
> > +	   || (cxx_dialect >= cxx23
> > +	       && (!SCALAR_TYPE_P (functype)
> > +		   || !SCALAR_TYPE_P (TREE_TYPE (retval)))))
> 
> You might reformat this as
> (cxx_dialect < cxx23
>  ? CLASS...
>  : (!SCALAR...

Done, I like that better.
 
> > --- a/gcc/testsuite/g++.dg/cpp0x/move-return3.C
> > +++ b/gcc/testsuite/g++.dg/cpp0x/move-return3.C
> > @@ -1,6 +1,7 @@
> >   // PR c++/91212
> >   // Test that C++11 implicit move semantics don't call the const copy.
> > -// { dg-do link }
> > +// In C++23, we call #2.
> 
> I guess that behavior is tested by elision2.C:twelve()?

Yeah, I think that's exactly the same case.
 
> > --- a/gcc/testsuite/g++.old-deja/g++.mike/p2846b.C
> > +++ b/gcc/testsuite/g++.old-deja/g++.mike/p2846b.C
> > @@ -1,4 +1,4 @@
> > -// { dg-do run  }
> > +// { dg-do run { target c++20_down } }
> >   // Shows that problem of initializing one object's secondary base from
> >   // another object via a user defined copy constructor for that base,
> >   // the pointer for the secondary vtable is not set after implicit
> > @@ -11,6 +11,8 @@
> >   // prms-id: 2846
> > +// This test fails in C++23 due to P2266.
> 
> Instead of disabling this test for C++23, let's add a cast to B& in the
> return statement.

Fixed.

> OK with that change and optionally the ?: reformatting above.

Thanks a lot; patch pushed.

Marek


      reply	other threads:[~2022-09-27 23:39 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-09-03 16:42 [PATCH] " Marek Polacek
2022-09-07  2:38 ` Jason Merrill
2022-09-08 22:54   ` Marek Polacek
2022-09-12 20:27     ` Jason Merrill
2022-09-20 18:21       ` Marek Polacek
2022-09-20 18:19   ` [PATCH v2] " Marek Polacek
2022-09-26 17:29     ` Jason Merrill
2022-09-27 20:26       ` [PATCH v3] " Marek Polacek
2022-09-27 21:44         ` Jason Merrill
2022-09-27 23:39           ` Marek Polacek [this message]

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=YzOJraytZZPJhmhJ@redhat.com \
    --to=polacek@redhat.com \
    --cc=gcc-patches@gcc.gnu.org \
    --cc=jason@redhat.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).