https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70472
--- Comment #2 from Jonathan Wakely <redi at gcc dot gnu.org> --- (In reply to Askar Safin from comment #0) > Also, please, make sure that std::is_copy_constructible gives right answers > for all standard containers. And same for other type_traits > (move_constructible etc). That's easy to say but much harder to do. > I don't know is > std::is_copy_constructible<std::vector<std::unique_ptr<int>>>::value == > false required by the standard. If no, then, please, add this requirement to > it. It's not required, and it would be impossible to require it in general. The problem is that std::vector does have a copy constructor, so the trait value is true, but instantiating that constructor produces an error when the value_type is not copyable. The trait is not required to instantiate the constructor (and doing so would cause other problems). > I noticed this bug when I tried to implement my own class template similar > to std::experimental::optional. Compiler give big error message when I > combine my class with other standard containers. If I add noexcept to my > move constructor, then the error message disappears. Types used with std::vector must be nothrow-move-constructible or copy-constructible. If your type has a throwing move-ctor then vector will try to copy it, which causes an instantiation error. > So I think this bug > somehow related to bug 55043 (bug #55043). If you want, I can describe this > my class template in detail. Also, this bug is very similar to this comment: > https://gcc.gnu.org/bugzilla/show_bug.cgi?id=55043#c15 . It's the same issue as PR 55043, but harder to fix for std::vector because the relevant constructors are not defined as defaulted. > I use stdlibc++ shipped with this gcc. It's libstdc++ not stdlibc++
