From: Jonathan Wakely <jwakely@redhat.com>
To: "François Dumont" <frs.dumont@gmail.com>
Cc: libstdc++@gcc.gnu.org, gcc-patches@gcc.gnu.org
Subject: Re: [PATCH] Do not use tuple-like interface for pair in unordered containers
Date: Mon, 26 Jul 2021 18:25:45 +0100 [thread overview]
Message-ID: <YP7wGXMRnvWl1GEL@redhat.com> (raw)
In-Reply-To: <YPsIwna/zCXgk1MI@redhat.com>
On 23/07/21 19:21 +0100, Jonathan Wakely wrote:
>I've been experimenting with this patch, which removes the need to use
>std::tuple_element and std::get to access the members of a std::pair
>in unordered_{map,multimap}.
>
>I'm in the process of refactoring the <utility> header to reduce
>header dependencies throughout the library, and this is the only use
>of the tuple-like interface for std::pair in the library.
>
>Using tuple_element and std::get resolved PR 53339 by allowing the
>std::pair type to be incomplete, however that is no longer supported
>anyway (the 23_containers/unordered_map/requirements/53339.cc test
>case is XFAILed). That means we could just define _Select1st as:
>
> struct _Select1st
> {
> template<typename _Tp>
> auto
> operator()(_Tp&& __x) const noexcept
> -> decltype(std::forward<_Tp>(__x).first)
> { return std::forward<_Tp>(__x).first; }
> };
>
>But the approach in the patch seems OK too.
Actually I have a fix for PR 53339 so that we can support incomplete
types again. So we don't want to access the .first member in the
return type, as that requires a complete type.
next prev parent reply other threads:[~2021-07-26 17:25 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-23 18:21 Jonathan Wakely
2021-07-26 17:25 ` Jonathan Wakely [this message]
2021-08-11 12:48 ` François Dumont
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=YP7wGXMRnvWl1GEL@redhat.com \
--to=jwakely@redhat.com \
--cc=frs.dumont@gmail.com \
--cc=gcc-patches@gcc.gnu.org \
--cc=libstdc++@gcc.gnu.org \
/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).