public inbox for gcc-patches@gcc.gnu.org
 help / color / mirror / Atom feed
From: Jakub Jelinek <jakub@redhat.com>
To: Jason Merrill <jason@redhat.com>
Cc: gcc-patches List <gcc-patches@gcc.gnu.org>
Subject: Re: C++ PATCH for testsuite failures with -std=c++17
Date: Thu, 25 May 2017 09:08:00 -0000	[thread overview]
Message-ID: <20170525085156.GY8499@tucnak> (raw)
In-Reply-To: <CADzB+2n9u7aqAne0Wp-M3qy4i53X5o6iCPjWF7UVnwKcjTOW5g@mail.gmail.com>

On Tue, May 09, 2017 at 04:37:16PM -0400, Jason Merrill wrote:
> For C++17 aggregate bases, we have started adding base fields for
> empty bases.  The code for calculating whether a class is standard
> layout needs to ignore these.
> 
> The C++17 mode diagnostic for direct-enum-init1.C was incorrect.
> 
> Tested x86_64-pc-linux-gnu, applying to trunk.

> commit 9a612cc30d4b3ef905ce45304545d8b99a3cf5b9
> Author: Jason Merrill <jason@redhat.com>
> Date:   Tue May 9 14:15:38 2017 -0400
> 
>             * class.c (check_bases): Ignore empty bases.

This should have referenced PR c++/80605 (and is also a 7 regression).

> diff --git a/gcc/cp/class.c b/gcc/cp/class.c
> index fc71766..085dbc3 100644
> --- a/gcc/cp/class.c
> +++ b/gcc/cp/class.c
> @@ -1860,7 +1860,9 @@ check_bases (tree t,
>  	       members */
>  	    for (basefield = TYPE_FIELDS (basetype); basefield;
>  		 basefield = DECL_CHAIN (basefield))
> -	      if (TREE_CODE (basefield) == FIELD_DECL)
> +	      if (TREE_CODE (basefield) == FIELD_DECL
> +		  && DECL_SIZE (basefield)
> +		  && !integer_zerop (DECL_SIZE (basefield)))

Is that what we really want?  I mean, shouldn't we at least also
check that the basefield we want to ignore is DECL_ARTIFICIAL,
or that it doesn't have DECL_NAME or something similar, to avoid
considering user fields with zero size the same?
I believe your change changes e.g.:
struct S { int a[0]; };
struct T : public S { int b[0]; int c; };
bool q = __is_standard_layout (T);
which previously e.g. with -std=gnu++14 emitted q = false, but
now emits q = true.

	Jakub

  reply	other threads:[~2017-05-25  8:51 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-05-09 20:42 Jason Merrill
2017-05-25  9:08 ` Jakub Jelinek [this message]
2017-05-25  9:23   ` Jakub Jelinek
2017-05-25 21:57     ` Jason Merrill

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=20170525085156.GY8499@tucnak \
    --to=jakub@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).