re PR c++/46472 ([C++0X] constexpr is not constexpr)

	PR c++/46472
	* method.c (process_subob_fn): Instantiate constexpr templates.
	* optimize.c (maybe_clone_body): Propagate DECL_DECLARED_CONSTEXPR_P.

From-SVN: r170348

gcc/cp/ChangeLog

+2011-02-20  Jason Merrill  <jason@redhat.com>
+
+	PR c++/46472
+	* method.c (process_subob_fn): Instantiate constexpr templates.
+	* optimize.c (maybe_clone_body): Propagate DECL_DECLARED_CONSTEXPR_P.
+
 2011-02-20  Dodji Seketeli  <dodji@redhat.com>
 
 	PR c++/46394

gcc/cp/method.c

@@ -941,8 +941,17 @@ process_subob_fn (tree fn, bool move_p, tree *spec_p, bool *trivial_p,
       goto bad;
     }
 
-  if (constexpr_p && !DECL_DECLARED_CONSTEXPR_P (fn))
-    *constexpr_p = false;
+  if (constexpr_p)
+    {
+      /* If this is a specialization of a constexpr template, we need to
+	 force the instantiation now so that we know whether or not it's
+	 really constexpr.  */
+      if (DECL_DECLARED_CONSTEXPR_P (fn) && DECL_TEMPLATE_INSTANTIATION (fn)
+	  && !DECL_TEMPLATE_INSTANTIATED (fn))
+	instantiate_decl (fn, /*defer_ok*/false, /*expl_class*/false);
+      if (!DECL_DECLARED_CONSTEXPR_P (fn))
+	*constexpr_p = false;
+    }
 
   return;
 

gcc/cp/optimize.c

@@ -256,6 +256,7 @@ maybe_clone_body (tree fn)
       /* Update CLONE's source position information to match FN's.  */
       DECL_SOURCE_LOCATION (clone) = DECL_SOURCE_LOCATION (fn);
       DECL_DECLARED_INLINE_P (clone) = DECL_DECLARED_INLINE_P (fn);
+      DECL_DECLARED_CONSTEXPR_P (clone) = DECL_DECLARED_CONSTEXPR_P (fn);
       DECL_COMDAT (clone) = DECL_COMDAT (fn);
       DECL_WEAK (clone) = DECL_WEAK (fn);
 

gcc/testsuite/ChangeLog

+2011-02-20  Jason Merrill  <jason@redhat.com>
+
+	* g++.dg/cpp0x/constexpr-synth1.C: New.
+
 2011-02-20  Nicola Pero  <nicola.pero@meta-innovation.com>
 
 	* objc.dg/layout-2.m: New.

gcc/testsuite/g++.dg/cpp0x/constexpr-synth1.C

+// PR c++/46472
+// { dg-options -std=c++0x }
+
+template<class T> struct A {
+  T t;
+  constexpr A(){}
+};
+
+struct B
+{
+  A<int> a;
+};
+
+B b;