Fix a problem that wasn't found on my mac builds... :-(.

lib/byte_array.cc

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/bootstrap_natives.h"
 
 #include "vm/bigint_operations.h"
 #include "vm/exceptions.h"
 #include "vm/native_entry.h"
 #include "vm/object.h"
@@ skipping 248 matching lines @@
   ByteArray& dst = ByteArray::CheckedHandle(arguments->At(0));
   GET_NATIVE_ARGUMENT(Smi, dst_start, arguments->At(1));
   GET_NATIVE_ARGUMENT(Smi, length, arguments->At(2));
   GET_NATIVE_ARGUMENT(ByteArray, src, arguments->At(3));
   GET_NATIVE_ARGUMENT(Smi, src_start, arguments->At(4));
   intptr_t length_value = length.Value();
   intptr_t src_start_value = src_start.Value();
   intptr_t dst_start_value = dst_start.Value();
   if (length_value < 0) {
     const String& error = String::Handle(String::NewFormatted(
-        "length (%ld) must be non-negative", index));
+        "length (%ld) must be non-negative", length_value));
     GrowableArray<const Object*> args;
     args.Add(&error);
     Exceptions::ThrowByType(Exceptions::kIllegalArgument, args);
   }
   RangeCheck(src, src_start_value, length_value);
   RangeCheck(dst, dst_start_value, length_value);
   ByteArray::Copy(dst, dst_start_value, src, src_start_value, length_value);
 }
 
 
@@ skipping 320 matching lines @@
 DEFINE_NATIVE_ENTRY(ExternalFloat64Array_getIndexed, 2) {
   GETTER(ExternalFloat64Array, Double, double);
 }
 
 
 DEFINE_NATIVE_ENTRY(ExternalFloat64Array_setIndexed, 3) {
   SETTER(ExternalFloat64Array, Double, value, double);
 }
 
 }  // namespace dart