PR c++/44780
	* typeck.c (convert_for_assignment): When converting a convertible
	vector type or objc++ types, call mark_rvalue_use.
	* typeck2.c (build_m_component_ref): Use return values from
	mark_rvalue_use or mark_lvalue_use.
	* class.c (build_base_path): Likewise.
	* call.c (build_conditional_expr): Likewise.

	* c-c++-common/Wunused-var-12.c: New test.

From-SVN: r161742