c++: split_nonconstant_init and flexarrays

split_nonconstant_init was doing the wrong thing for both the initialization
and cleanup here; we know the size from the initializer, and we can pass it
along.  This doesn't make the testcase work, since the y destructor is still
broken, but it removes the wrong error for the aggregate initialization.

gcc/cp/ChangeLog:

	* typeck2.c (split_nonconstant_init_1): Handle flexarrays better.

gcc/testsuite/ChangeLog:

	* g++.dg/ext/flexary37.C: Remove expected error.

gcc/cp/typeck2.c

@@ -484,6 +484,15 @@ split_nonconstant_init_1 (tree dest, tree init, bool nested)
 	   && TYPE_HAS_NONTRIVIAL_DESTRUCTOR (type))
 	  || vla_type_p (type))
 	{
+	  if (!TYPE_DOMAIN (type)
+	      && TREE_CODE (init) == CONSTRUCTOR
+	      && CONSTRUCTOR_NELTS (init))
+	    {
+	      /* Flexible array.  */
+	      cp_complete_array_type (&type, init, /*default*/true);
+	      dest = build1 (VIEW_CONVERT_EXPR, type, dest);
+	    }
+
 	  /* For an array, we only need/want a single cleanup region rather
 	     than one per element.  */
 	  tree code = build_vec_init (dest, NULL_TREE, init, false, 1,

gcc/testsuite/g++.dg/ext/flexary37.C

@@ -12,4 +12,4 @@ public:
 
 struct y { // { dg-error "unknown array size in delete" }
     int a; C b[];
-} y = { 1, { { 2, 3 } } }; // { dg-error "unknown array size in delete" }
+} y = { 1, { { 2, 3 } } };