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From: "redi at gcc dot gnu.org" <gcc-bugzilla@gcc.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) Date: Thu, 05 May 2011 22:08:00 -0000 [thread overview] Message-ID: <bug-48891-4-pANR8Cxh1H@http.gcc.gnu.org/bugzilla/> (raw) In-Reply-To: <bug-48891-4@http.gcc.gnu.org/bugzilla/> http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48891 --- Comment #2 from Jonathan Wakely <redi at gcc dot gnu.org> 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 <math.h> > 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
next prev parent reply other threads:[~2011-05-05 22:08 UTC|newest] Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top 2011-05-05 21:50 [Bug libstdc++/48891] New: std functions conflicts with C functions when building with c++0x support alexis.menard at openbossa dot org 2011-05-05 21:44 ` [Bug libstdc++/48891] " alexis.menard at openbossa dot org 2011-05-05 22:08 ` redi at gcc dot gnu.org [this message] 2011-05-05 22:22 ` [Bug libstdc++/48891] std functions conflicts with C functions when building with c++0x support (and using namespace std) alexis.menard at openbossa dot org 2011-05-05 22:47 ` paolo.carlini at oracle dot com 2011-05-05 23:16 ` paolo.carlini at oracle dot com 2012-04-29 13:17 ` marc.glisse at normalesup dot org 2015-04-09 14:35 ` redi at gcc dot gnu.org
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