libstdc++/77686 use may_alias for std::function storage

	PR libstdc++/77686
	* include/std/functional (_Any_data): Add may_alias attribute.

From-SVN: r240567

libstdc++-v3/ChangeLog

+2016-09-28  Jonathan Wakely  <jwakely@redhat.com>
+
+	PR libstdc++/77686
+	* include/std/functional (_Any_data): Add may_alias attribute.
+
 2016-09-27  Jonathan Wakely  <jwakely@redhat.com>
 
 	* doc/xml/manual/status_cxx2017.xml: Update status.

libstdc++-v3/include/std/functional

@@ -1401,7 +1401,7 @@ _GLIBCXX_MEM_FN_TRAITS(&&, false_type, true_type)
     void (_Undefined_class::*_M_member_pointer)();
   };
 
-  union _Any_data
+  union [[gnu::may_alias]] _Any_data
   {
     void*       _M_access()       { return &_M_pod_data[0]; }
     const void* _M_access() const { return &_M_pod_data[0]; }