From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 24297 invoked by alias); 5 May 2011 22:08:59 -0000 Received: (qmail 24286 invoked by uid 22791); 5 May 2011 22:08:58 -0000 X-SWARE-Spam-Status: No, hits=-2.7 required=5.0 tests=ALL_TRUSTED,AWL,BAYES_00 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; Thu, 05 May 2011 22:08:44 +0000 From: "redi at gcc dot gnu.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) 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: 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-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 Date: Thu, 05 May 2011 22:08:00 -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 X-SW-Source: 2011-05/txt/msg00485.txt.bz2 http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48891 --- Comment #2 from Jonathan Wakely 2011-05-05 22:03:55 UTC --- (In reply to comment #0) > > and build it with : g++ main.cpp -std=c++0x -std=gnu++0x -o test There's no point specifying two -std options, only the last one takes effect. > If I deactivate the c++0x support it works. Because in C++98 there is no std::isnan, so you only get the version in the global namespace from > The real issue is that the c++0x standard removes the prohibition on C++ > headers declaring C names in the global namespace. The problem here is that > math.h is included therefore the declarations are in the global namespace. I don't think that's the problem, because libstdc++ has always declared the names in the global namespace even though it wasn't valid in C++03 - we haven't changed that for C++0x (all that happened is the standard was relaxed to reflect the reality of actual implementations) > I'm not really sure how the compiler can solve that but this new "feature" of > c++0x seems to be very annoying. I could solve it by not using namespace std > but let say the project is huge, it will requires lot of modifications. > > Basically any time you use using namespace std, you may have conflicts with the > underlaying C libraries, it's even more annoying with your own namespace > because your functions can conflict with all the stuff in the global namespace > put by C libraries and it's very common in a cpp file to use "using namespace > foo;" > > Any suggestions on how I could "workaround" that? Qualify isnan explicitly, by calling either ::isnan or std::isnan