From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 25861 invoked by alias); 16 Jun 2014 22:10:53 -0000 Mailing-List: contact gcc-bugs-help@gcc.gnu.org; run by ezmlm Precedence: bulk List-Id: List-Archive: List-Post: List-Help: Sender: gcc-bugs-owner@gcc.gnu.org Received: (qmail 25829 invoked by uid 48); 16 Jun 2014 22:10:48 -0000 From: "redi at gcc dot gnu.org" To: gcc-bugs@gcc.gnu.org Subject: [Bug libstdc++/56785] std::tuple of two elements does not apply empty base class optimization when one of its elements is a std::tuple with two elements Date: Mon, 16 Jun 2014 22:10:00 -0000 X-Bugzilla-Reason: CC X-Bugzilla-Type: changed X-Bugzilla-Watch-Reason: None X-Bugzilla-Product: gcc X-Bugzilla-Component: libstdc++ X-Bugzilla-Version: 4.7.2 X-Bugzilla-Keywords: X-Bugzilla-Severity: enhancement X-Bugzilla-Who: redi at gcc dot gnu.org X-Bugzilla-Status: UNCONFIRMED X-Bugzilla-Priority: P3 X-Bugzilla-Assigned-To: unassigned at gcc dot gnu.org X-Bugzilla-Target-Milestone: --- X-Bugzilla-Flags: X-Bugzilla-Changed-Fields: Message-ID: In-Reply-To: References: Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit X-Bugzilla-URL: http://gcc.gnu.org/bugzilla/ Auto-Submitted: auto-generated MIME-Version: 1.0 X-SW-Source: 2014-06/txt/msg01405.txt.bz2 https://gcc.gnu.org/bugzilla/show_bug.cgi?id=56785 --- Comment #3 from Jonathan Wakely --- (In reply to Eelis from comment #2) > Another manifestation of this is that > > sizeof(pair,pair>) == 4 > > while > > sizeof(tuple,tuple>) == 5 (!!). Oh noes, one byte more for a silly edge case! > I think that at the moment, GCC users are best advised to avoid using stdlib > tuples if efficiency is a concern. That's a ridiculous conclusion to reach based on an edge case. There are many realistic situations where std::tuple is more compact that std::pair.