https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70651
--- Comment #3 from Marek Polacek <mpolacek at gcc dot gnu.org> --- We have the code to reject this, but it happens only when gimplifying: 11695 if (have_va_type == NULL_TREE) 11696 { 11697 error_at (loc, "first argument to %<va_arg%> not of type %<va_list%>"); 11698 return GS_ERROR; 11699 }