From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 25841 invoked by alias); 29 Apr 2012 13:17:01 -0000 Received: (qmail 25829 invoked by uid 22791); 29 Apr 2012 13:17:00 -0000 X-SWARE-Spam-Status: No, hits=-4.3 required=5.0 tests=ALL_TRUSTED,AWL,BAYES_00,KHOP_THREADED X-Spam-Check-By: sourceware.org Received: from localhost (HELO gcc.gnu.org) (127.0.0.1) by sourceware.org (qpsmtpd/0.43rc1) with ESMTP; Sun, 29 Apr 2012 13:16:46 +0000 From: "marc.glisse at normalesup dot org" To: gcc-bugs@gcc.gnu.org Subject: [Bug libstdc++/48891] std functions conflicts with C functions when building with c++0x support (and using namespace std) Date: Sun, 29 Apr 2012 13:17:00 -0000 X-Bugzilla-Reason: CC X-Bugzilla-Type: changed X-Bugzilla-Watch-Reason: None X-Bugzilla-Product: gcc X-Bugzilla-Component: libstdc++ X-Bugzilla-Keywords: X-Bugzilla-Severity: normal X-Bugzilla-Who: marc.glisse at normalesup dot 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-Changed-Fields: Message-ID: In-Reply-To: References: X-Bugzilla-URL: http://gcc.gnu.org/bugzilla/ Auto-Submitted: auto-generated Content-Type: text/plain; charset="UTF-8" MIME-Version: 1.0 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 X-SW-Source: 2012-04/txt/msg02554.txt.bz2 http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48891 --- Comment #6 from Marc Glisse 2012-04-29 13:15:40 UTC --- I don't think it matters that much whether the return type is int or bool, compared to the inconvenience of having 2 functions that conflict. The constexpr qualifier is nice, but not required by the standard, and not even by gcc which recognizes that extern "C" int isnan(double) is a builtin (note that it doesn't recognize it anymore if you change the return type to bool, that should be fixed). For the same reason (recognized as a builtin), there is no performance advantage to having it inline. So I think: * glibc could change the return type of isnan to bool in C++ (there would be a regression in that ::isnan wouldn't be constexpr and inline until g++ is taught the right prototype) * libstdc++ could import ::isnan in std::, assuming isnan exists. Maybe that requires a configure test. Maybe that test would be rather fragile (depends on feature macros). Maybe that's where this stops being a good idea :-(