https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115905
--- Comment #13 from Iain Sandoe <iains at gcc dot gnu.org> --- looking like a GTY issue: (gdb) p target->u.fld[1]->rt_mem $7 = (mem_attrs *) 0xafafafaf (gdb) p target->u.fld[1]->rt_mem->align that seems to be the tell-tale value for a free ptr.
