C++ PATCH for c++/46348 (array value-init and constexpr)

diff --git a/gcc/cp/semantics.c b/gcc/cp/semantics.c
index 1ee0ccf..db0d0a1 100644
--- a/gcc/cp/semantics.c
+++ b/gcc/cp/semantics.c
@@ -6391,15 +6391,16 @@  cxx_eval_bare_aggregate (const constexpr_call *call, tree t,
    initialization of a non-static data member of array type.  Reduce it to a
    CONSTRUCTOR.
 
-   Note that this is only intended to support the initializations done by
-   defaulted constructors for classes with non-static data members of array
-   type.  In this case, VEC_INIT_EXPR_INIT will either be NULL_TREE for the
-   default constructor, or a COMPONENT_REF for the copy/move
-   constructor.  */
+   Note that apart from value-initialization (when VALUE_INIT is true),
+   this is only intended to support value-initialization and the
+   initializations done by defaulted constructors for classes with
+   non-static data members of array type.  In this case, VEC_INIT_EXPR_INIT
+   will either be NULL_TREE for the default constructor, or a COMPONENT_REF
+   for the copy/move constructor.  */
 
 static tree
 cxx_eval_vec_init_1 (const constexpr_call *call, tree atype, tree init,
-		     bool allow_non_constant, bool addr,
+		     bool value_init, bool allow_non_constant, bool addr,
 		     bool *non_constant_p)
 {
   tree elttype = TREE_TYPE (atype);
@@ -6412,7 +6413,9 @@  cxx_eval_vec_init_1 (const constexpr_call *call, tree atype, tree init,
      here, as for a constructor to be constexpr, all members must be
      initialized, which for a defaulted default constructor means they must
      be of a class type with a constexpr default constructor.  */
-  if (!init)
+  if (value_init)
+    gcc_assert (!init);
+  else if (!init)
     {
       VEC(tree,gc) *argvec = make_tree_vector ();
       init = build_special_member_call (NULL_TREE, complete_ctor_identifier,
@@ -6433,12 +6436,21 @@  cxx_eval_vec_init_1 (const constexpr_call *call, tree atype, tree init,
       if (TREE_CODE (elttype) == ARRAY_TYPE)
 	{
 	  /* A multidimensional array; recurse.  */
-	  eltinit = cp_build_array_ref (input_location, init, idx,
-					tf_warning_or_error);
-	  eltinit = cxx_eval_vec_init_1 (call, elttype, eltinit,
+	  if (value_init)
+	    eltinit = NULL_TREE;
+	  else
+	    eltinit = cp_build_array_ref (input_location, init, idx,
+					  tf_warning_or_error);
+	  eltinit = cxx_eval_vec_init_1 (call, elttype, eltinit, value_init,
 					 allow_non_constant, addr,
 					 non_constant_p);
 	}
+      else if (value_init)
+	{
+	  eltinit = build_value_init (elttype, tf_warning_or_error);
+	  eltinit = cxx_eval_constant_expression
+	    (call, eltinit, allow_non_constant, addr, non_constant_p);
+	}
       else if (TREE_CODE (init) == CONSTRUCTOR)
 	{
 	  /* Initializing an element using the call to the default
@@ -6488,8 +6500,9 @@  cxx_eval_vec_init (const constexpr_call *call, tree t,
 {
   tree atype = TREE_TYPE (t);
   tree init = VEC_INIT_EXPR_INIT (t);
-  tree r = cxx_eval_vec_init_1 (call, atype, init, allow_non_constant,
-				addr, non_constant_p);
+  tree r = cxx_eval_vec_init_1 (call, atype, init,
+				VEC_INIT_EXPR_VALUE_INIT (t),
+				allow_non_constant, addr, non_constant_p);
   if (*non_constant_p)
     return t;
   else
diff --git a/gcc/testsuite/g++.dg/cpp0x/constexpr-array2.C b/gcc/testsuite/g++.dg/cpp0x/constexpr-array2.C
new file mode 100644
index 0000000..9577f75
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/constexpr-array2.C
@@ -0,0 +1,19 @@ 
+// PR c++/46348
+// { dg-options -std=c++0x }
+
+template<__SIZE_TYPE__ _Nw>
+  struct _Base
+  {
+    typedef unsigned long _WordT;
+
+    _WordT _M_w[_Nw];
+
+    constexpr
+    _Base()
+    : _M_w() { }
+  };
+
+int main()
+{
+  _Base<256> bs;
+}