Gentoo's Bugzilla –
Attachment 464092 Details for
Bug 609618media-sound/mpd-0.20.4 - src/command/CommandError.cxx:21: error: cannot dynamic_cast ‘& __ex’ (of type ‘const class std::__exception_ptr::exception_ptr*’) to type ‘const class std::nested_exception*’ (source type is not polymorphic)