Index: cp/init.c
===================================================================
--- cp/init.c	(revision 202296)
+++ cp/init.c	(working copy)
@@ -3078,7 +3078,7 @@ build_vec_delete_1 (tree base, tree maxindex, tree
 {
   tree virtual_size;
   tree ptype = build_pointer_type (type = complete_type (type));
-  tree size_exp = size_in_bytes (type);
+  tree size_exp;
 
   /* Temporary variables used by the loop.  */
   tree tbase, tbase_init;
@@ -3106,6 +3106,22 @@ build_vec_delete_1 (tree base, tree maxindex, tree
   if (base == error_mark_node || maxindex == error_mark_node)
     return error_mark_node;
 
+  if (!COMPLETE_TYPE_P (type))
+    {
+      if ((complain & tf_warning)
+	  && warning (0, "possible problem detected in invocation of "
+		      "delete [] operator:"))
+       {
+         cxx_incomplete_type_diagnostic (base, type, DK_WARNING);
+         inform (input_location, "neither the destructor nor the "
+                 "class-specific operator delete [] will be called, "
+                 "even if they are declared when the class is defined");
+       }
+      return build_builtin_delete_call (base);
+    } 
+
+  size_exp = size_in_bytes (type);
+
   if (! MAYBE_CLASS_TYPE_P (type) || TYPE_HAS_TRIVIAL_DESTRUCTOR (type))
     goto no_destructor;
 
Index: testsuite/g++.dg/init/delete1.C
===================================================================
--- testsuite/g++.dg/init/delete1.C	(revision 202284)
+++ testsuite/g++.dg/init/delete1.C	(working copy)
@@ -1,7 +1,7 @@
 // PR c++/19811
 
-class C; // { dg-error "forward" }
+class C; // { dg-warning "forward" }
 
 void foo(void *p) {
-  delete [] ((C*)p) ; // { dg-error "" }
+  delete [] ((C*)p) ; // { dg-warning "problem|incomplete" }
 }