* langhooks-def.h (LANG_HOOKS_EXPR_SIZE): New macro.
        * langhooks.c (lhd_expr_size): Define default.
        * langhooks.h (struct lang_hooks): Add expr_size.
        * explow.c (expr_size): Call it.
        * expr.c (store_expr): Don't copy an expression of size zero.
        (expand_expr) [CONSTRUCTOR]: Use expr_size to calculate how much
        to store.
        * Makefile.in (builtins.o): Depend on langhooks.h.

        * cp-lang.c (LANG_HOOKS_EXPR_SIZE): Define.
        (cp_expr_size): New fn.
        * call.c (build_over_call): Lose empty class hackery.
        (convert_arg_to_ellipsis): Promote non-POD warning to error.
        * typeck.c (build_modify_expr): Don't use save_expr on an lvalue.

From-SVN: r55983