https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70650
--- Comment #2 from Jack Howarth <howarth.at.gcc at gmail dot com> ---
This regression is caused by the commit...
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r234959 | jason | 2016-04-13 16:11:20 -0400 (Wed, 13 Apr 2016) | 7 lines
Pass empty class parameters like C.
* call.c (pass_as_empty_struct, empty_class_arg): New.
(type_passed_as, build_x_va_arg): Use pass_as_empty_struct.
(build_call_a): Use empty_class_arg.
* cp-tree.h (CPTI_EMPTY_STRUCT, empty_struct_type): New.
* decl.c (cxx_init_decl_processing): Create empty_struct_type.
