Error building with GCC 6 (C++14)

[loganjerry@…]

Fedora has started building with the upcoming GCC 6 compiler, which defaults to C++14 mode when building C++ code. It encounters an error while building Singular 4-0-3:

ppinitialReduction.cc: In function 'bool ppreduceInitially(sip_sideal*&, number, ideal, ring)':
ppinitialReduction.cc:675:46: error: no matching function for call to 'make_pair(int&, int)'
       T.push_back(std::make_pair<int,int>(i,1));
                                              ^
In file included from /usr/include/c++/6.0.0/bits/stl_algobase.h:64:0,
                 from /usr/include/c++/6.0.0/vector:60,
                 from ../../../gfanlib/gfanlib_vector.h:11,
                 from ./tropicalStrategy.h:4,
                 from ppinitialReduction.h:5,
                 from ppinitialReduction.cc:5:
/usr/include/c++/6.0.0/bits/stl_pair.h:406:5: note: candidate: template<class _T1, class _T2> constexpr std::pair<typename std::__decay_and_strip<_Tp>::__type, typename std::__decay_and_strip<_T2>::__type> std::make_pair(_T1&&, _T2&&)
     make_pair(_T1&& __x, _T2&& __y)
     ^~~~~~~~~
/usr/include/c++/6.0.0/bits/stl_pair.h:406:5: note:   template argument deduction/substitution failed:
ppinitialReduction.cc:675:46: note:   cannot convert 'i' (type 'int') to type 'int&&'
       T.push_back(std::make_pair<int,int>(i,1));
                                              ^

The solution is to let the compiler deduce the types; i.e. change that line to this:

       T.push_back(std::make_pair(i,1));

This should work for earlier versions of GCC as well. The point of make_pair is that you don't have to specify the types.

[hannes]

already fixed with 6828dc2a9db4f0616aef09df69cf620b2f3ace02