CGAL users discussion list

[Martin Seemann <>]

Hello Marc

glad to see that it is already taken care of in the current beta and 
sorry for the noise about it.

Also thanks for pointing out ADL in this context. I wasn't aware that 
base was a std::pair. Now the compiler behavior makes perfect sense again.

Am 11.08.2015 um 04:48 schrieb Marc Glisse:
> On Fri, 7 Aug 2015, Martin Seemann wrote:
>
> > I recently came across a regression, which is demonstrated by the
> > example below:
> >
> > #include <CGAL/Simple_cartesian.h>
> > int main() {
> >     typedef CGAL::Simple_cartesian<double> K;
> >     CGAL::Line_3<K> line(CGAL::Point_3<K>(0, 0, 0),
> > CGAL::Point_3<K>(1, 1, 1));
> >     std::cout << line.point(0) << std::endl;
> >     return 0; }
> >
> > Using GCC 5.2.0 (Archlinux), the above example compiles fine with
> > -std=c++11 but when switching to -std=c++14, the compiler starts
> > complaining about ambiguous 'get(...)' overloads in
> > CGAL/Cartesian/Line_3.h:78.
> > I figured that it was caused by some c++14 additions to the standard
> > library (http://en.cppreference.com/w/cpp/utility/pair/get, overloads
> > 4-7).
> > A quick fix is to make the desired namespace explicit in
> > CGAL/Cartesian/Line_3.h, i. e. to replace lines 78 and 83 by
> >    return CGAL::get(base).first;
> > and
> >    return CGAL::get(base).second;
> > respectively.
> > After these modifications, the above example (and also my real
> > project) compiles fine.
>
> https://github.com/CGAL/cgal/commit/b7f98495991ee49b2b01e64a36bb3b5c1e89a615
>
>
> > However, prefixing with CGAL:: in this place seems strange to me,
> > since we are already in namespace CGAL. Furthermore, I do not
> > understand why the std::get variants even participate in overload
> > resolution, given that they are defined in std (I couldn't find any
> > dangerous
> > 'using namespace std' anywhere in the CGAL code base either).
> >
> > Maybe someone with a deeper understanding of the language can give his
> > opinion if this situation should be corrected in CGAL or in the
> > standard library.
> > BTW: The error also happens with clang (v3.6.2)
> > (My CGAL version is 4.6.2)
>
> ADL means that if the arguments involve a type defined in namespace std
> (even indirectly), std::get gets to participate.