On 16 December 2016 at 11:00, Jonathan Wakely wrote: > On 16 December 2016 at 10:04, Edward Diener wrote: >> I am testing gcc-6.2 with the -std=c++03 switch against some Boost C++ code >> in a library which does not require c++11 on up support. Without going into >> the exact code I am seeing a compiler error along the lines of: >> >> some_path/some_header_file.hpp:224:20: error: no matching function for call >> to 'std::pair<int&, std::__cxx11::basic_string<char>&>::pair(int&, >> std::__cxx11::basic_string<char>&)' >> >> This implies that even when the -std=c++03 switch with gcc-6.2 c++11 >> constructs are being internally used. > > No it doesn't, see > https://gcc.gnu.org/onlinedocs/libstdc++/manual/using_dual_abi.html > > Whether the __cxx11 ABI is used or not orthogonal to the -std option. > It's controlled by a macro. If you compile with > -D_GLIBCXX_USE_CXX11_ABI=0 you'll see the exact same error without the > __cxx11 qualification. > >> Testing the exact same code with the >> -std=c++11 switch or with the -std=c++14 switch there are no errors. Does >> this mean that using gcc-6.2 with -std=c++03 does not work with gcc-6.2, or >> is there something other compiler switch I must use along with the >> -std=c++03 switch to be able to compile using gcc-6.2 in c++03 mode ? > > There is no other switch, -std=c++03 is all that's needed, and you're > misinterpreting the error. > > I would guess that the code is using std::make_pair with an explicit > template argument list, which changed meaning between C++03 and C++11, > so the code is simply not compatible with C++03. Or it's trying to create a pair of references, which also doesn't work in C++03, because std::pair only had this constructor: pair(const T1& x, const T2& y); So you can't create a std::pair<int&, std::string&> because there's no way to pass non-const references to the constructor, so there's no way to initialize the members. So it looks like the Boost code does in fact require C++11 or later.
