re PR c++/38908 (Unexplained "'<anonymous>' is used uninitialized in this function" warning in cc1plus -m64)

        PR c++/38908
        * class.c (is_really_empty_class): New fn.
        * cp-tree.h: Declare it.
        * cp-objcp-common.c (cp_expr_size): Use it.

From-SVN: r144643