http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53646
--- Comment #6 from Michael Matz <matz at gcc dot gnu.org> 2012-06-12 15:41:49 UTC --- FWIW, it's finish_struct_bits setting TREE_ADDRESSABLE, because type_has_nontrivial_copy_init returns true for pair with that ctor. I think this indeed makes pair non-POD.
