C++ PATCH for c++/48138 (losing __attribute ((aligned)) on template argument)

commit d4813fc54ee69f5880e588e8b9edf97baa0ad6cc
Author: Jason Merrill <jason@redhat.com>
Date:   Mon Jun 20 14:37:05 2011 -0400

    	PR c++/48138
    	* pt.c (canonicalize_type_argument): New.
    	(convert_template_argument, unify): Use it.

diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c
index 6f15101..4d2caa8 100644
--- a/gcc/cp/pt.c
+++ b/gcc/cp/pt.c
@@ -5916,6 +5916,28 @@  template_template_parm_bindings_ok_p (tree tparms, tree targs)
   return ret;
 }
 
+/* Since type attributes aren't mangled, we need to strip them from
+   template type arguments.  */
+
+static tree
+canonicalize_type_argument (tree arg, tsubst_flags_t complain)
+{
+  tree mv;
+  if (!arg || arg == error_mark_node || arg == TYPE_CANONICAL (arg))
+    return arg;
+  mv = TYPE_MAIN_VARIANT (arg);
+  arg = strip_typedefs (arg);
+  if (TYPE_ALIGN (arg) != TYPE_ALIGN (mv)
+      || TYPE_ATTRIBUTES (arg) != TYPE_ATTRIBUTES (mv))
+    {
+      if (complain & tf_warning)
+	warning (0, "ignoring attributes on template argument %qT", arg);
+      arg = build_aligned_type (arg, TYPE_ALIGN (mv));
+      arg = cp_build_type_attribute_variant (arg, TYPE_ATTRIBUTES (mv));
+    }
+  return arg;
+}
+
 /* Convert the indicated template ARG as necessary to match the
    indicated template PARM.  Returns the converted ARG, or
    error_mark_node if the conversion was unsuccessful.  Error and
@@ -6092,7 +6114,7 @@  convert_template_argument (tree parm,
 	 the typedef, which is confusing if those future uses do not
 	 themselves also use the typedef.  */
       if (TYPE_P (val))
-	val = strip_typedefs (val);
+	val = canonicalize_type_argument (val, complain);
     }
   else
     {
@@ -6136,8 +6158,9 @@  convert_template_argument (tree parm,
       if (TREE_CODE (val) == SCOPE_REF)
 	{
 	  /* Strip typedefs from the SCOPE_REF.  */
-	  tree type = strip_typedefs (TREE_TYPE (val));
-	  tree scope = strip_typedefs (TREE_OPERAND (val, 0));
+	  tree type = canonicalize_type_argument (TREE_TYPE (val), complain);
+	  tree scope = canonicalize_type_argument (TREE_OPERAND (val, 0),
+						   complain);
 	  val = build_qualified_name (type, scope, TREE_OPERAND (val, 1),
 				      QUALIFIED_NAME_IS_TEMPLATE (val));
 	}
@@ -15479,7 +15502,7 @@  unify (tree tparms, tree targs, tree parm, tree arg, int strict)
 	    return 1;
 
 	  /* Strip typedefs as in convert_template_argument.  */
-	  arg = strip_typedefs (arg);
+	  arg = canonicalize_type_argument (arg, tf_none);
 	}
 
       /* If ARG is a parameter pack or an expansion, we cannot unify
diff --git a/gcc/testsuite/g++.dg/ext/attr-aligned01.C b/gcc/testsuite/g++.dg/ext/attr-aligned01.C
index a051c6e..c8ec07d 100644
--- a/gcc/testsuite/g++.dg/ext/attr-aligned01.C
+++ b/gcc/testsuite/g++.dg/ext/attr-aligned01.C
@@ -1,20 +1,25 @@ 
 // PR c++/48138
-// { dg-options -std=c++0x }
 
 #define ALIGNED(x) __attribute__((aligned(x)))
-#define SA(X) static_assert ((X),#X)
+#define SA(X) int ar[(X)?1:-1];
 
 template<typename T>
 void type_alignment(const T&) {
   struct { char c; T t; } s;
-  SA((char*)&s.t - (char*)&s.c == 8);
+  SA((char*)&s.t - (char*)&s.c == 1);
 }
 
+template <class T> struct A { char c; T t; };
+
 int main() {
   typedef char unaligned[15];
   typedef char aligned[15] ALIGNED(8);
 
+  A<aligned> a;			// { dg-warning "ignoring attributes" }
+
+  SA((char*)&a.t - (char*)&a.c == 1);
+
   aligned z;
-  type_alignment(z);
-  type_alignment<unaligned ALIGNED(8)>(z);
+  type_alignment(z);		// { dg-warning "ignoring attributes" "" { xfail *-*-* } }
+  type_alignment<unaligned ALIGNED(8)>(z); // { dg-warning "ignoring attributes" "" { xfail *-*-* } }
 }