https://gcc.gnu.org/bugzilla/show_bug.cgi?id=86513
--- Comment #3 from Csaba Ráduly <csaba_22 at yahoo dot co.uk> --- I don't get this. ostringstream isn't even supposed to have a default constructor, only the openmode, string and openmode, and the move constructor (if I'm reading [ostringstream.cons] in N4659 right). In the meantime it fixed itself at revision 262687 (mybe my usual "svn up && make bootstrap && make install" triggered the necessary rebuild). $ nm /usr/local/lib/gcc/x86_64-pc-linux-gnu/9.0.0/libstdc++.a | grep _ZNSt7__cxx1119basic_ostringstreamIcSt11char_traitsIcESaIcEEC1E | c++filt 0000000000000000 W std::__cxx11::basic_ostringstream<char, std::char_traits<char>, std::allocator<char> >::basic_ostringstream(std::__cxx11::basic_ostringstream<char, std::char_traits<char>, std::allocator<char> >&&) 0000000000000000 W std::__cxx11::basic_ostringstream<char, std::char_traits<char>, std::allocator<char> >::basic_ostringstream(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&, std::_Ios_Openmode) 0000000000000000 W std::__cxx11::basic_ostringstream<char, std::char_traits<char>, std::allocator<char> >::basic_ostringstream(std::_Ios_Openmode) 0000000000000000 W std::__cxx11::basic_ostringstream<char, std::char_traits<char>, std::allocator<char> >::basic_ostringstream()
