C++ PATCH for c++/66216 (ICE with aligned attribute)

[Jason Merrill]

We weren't properly propagating the alignment to other variants after 
applying it, so we ended up with two const-qualified variants with 
different alignment.

Tested x86_64-pc-linux-gnu, applying to trunk and 5.
commit ffea563209dfc6daf1054fffc6f8d726e440f1dc
Author: Jason Merrill <ja...@redhat.com>
Date:   Fri Jun 26 16:52:01 2015 -0400
    	PR c++/66216
    	* class.c (finish_struct): Call fixup_attribute_variants.

diff --git a/gcc/cp/class.c b/gcc/cp/class.c
index f4e4f85..be31de2 100644
--- a/gcc/cp/class.c
+++ b/gcc/cp/class.c
@@ -6820,6 +6820,7 @@ finish_struct (tree t, tree attributes)
   unreverse_member_declarations (t);
 
   cplus_decl_attributes (&t, attributes, (int) ATTR_FLAG_TYPE_IN_PLACE);
+  fixup_attribute_variants (t);
 
   /* Nadger the current location so that diagnostics point to the start of
      the struct, not the end.  */
diff --git a/gcc/testsuite/g++.dg/ext/attrib52.C b/gcc/testsuite/g++.dg/ext/attrib52.C
new file mode 100644
index 0000000..e33556c
--- /dev/null
+++ b/gcc/testsuite/g++.dg/ext/attrib52.C
@@ -0,0 +1,15 @@
+// PR c++/66216
+// { dg-do compile { target c++11 } }
+// { dg-options "" }
+
+class CMymy
+{
+  unsigned char _a;
+  unsigned char _b;
+public:
+  constexpr CMymy() : _a(), _b() {}
+
+  constexpr CMymy(const CMymy &) = default;
+  CMymy &operator=(const CMymy &) = default;
+
+} __attribute__((aligned(2)));