http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48891
--- Comment #3 from Alexis Menard <alexis.menard at openbossa dot org> 2011-05-05 22:17:36 UTC --- (In reply to comment #2) > (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> That explain. > > > 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) > Sorry for my ignorance. > > > 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 Well that requires me to modify my entire project, namely WebKit :(. But the more I'm stuck on that issue, the more it seems to be the only solution.
