https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80683
--- Comment #3 from Xi Ruoyao <ryxi at stu dot xidian.edu.cn> --- For debug purpose, compiled this code in C++98 mode (non-static data member initializers is a GNU extension in C++98 and would be warned). The result is still buggy. Defaulted B::B() is marked noexcept.
