Allow to neuter array buffer twice in tests.

src/runtime.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
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@@ skipping 893 matching lines @@
   CONVERT_ARG_CHECKED(Object, object, 0);
   return object->IsJSArrayBufferView()
     ? isolate->heap()->true_value()
     : isolate->heap()->false_value();
 }
 
 
 RUNTIME_FUNCTION(MaybeObject*, Runtime_ArrayBufferNeuter) {
   HandleScope scope(isolate);
   CONVERT_ARG_HANDLE_CHECKED(JSArrayBuffer, array_buffer, 0);
+  if (array_buffer->backing_store() == NULL) {
+    CHECK(Smi::FromInt(0) == array_buffer->byte_length());
+    return isolate->heap()->undefined_value();
+  }

[Jarin, 2014/03/25 10:59:42]

How about keeping just one return statement? That is, saying something like:

RUNTIME_FUNCTION(MaybeObject*, Runtime_ArrayBufferNeuter) {
  ...
  if (array_buffer->backing_store() != NULL) {
    ... do the neutering...
  }
  CHECK(Smi::FromInt(0) == array_buffer->byte_length());
  return isolate->heap()->undefined_value();
}

[Dmitry Lomov (no reviews), 2014/03/25 11:04:25]

I think that complicates code for the edge case.

[Sven Panne, 2014/03/25 11:30:35]

Actually I like the initial version, too, a "comb-like" pattern is very easy to
read:

void foo() {
   if (special_condition1) return val1;
   if (special_condition2) return val2;
   <compute normal case>
   return normal_case_val;
}

see http://refactoring.com/catalog/replaceNestedConditionalWithGuardClauses.html

   ASSERT(!array_buffer->is_external());
   void* backing_store = array_buffer->backing_store();
   size_t byte_length = NumberToSize(isolate, array_buffer->byte_length());
   array_buffer->set_is_external(true);
   Runtime::NeuterArrayBuffer(array_buffer);
   V8::ArrayBufferAllocator()->Free(backing_store, byte_length);
   return isolate->heap()->undefined_value();
 }
 
 
@@ skipping 14184 matching lines @@
     // Handle last resort GC and make sure to allow future allocations
     // to grow the heap without causing GCs (if possible).
     isolate->counters()->gc_last_resort_from_js()->Increment();
     isolate->heap()->CollectAllGarbage(Heap::kNoGCFlags,
                                        "Runtime::PerformGC");
   }
 }
 
 
 } }  // namespace v8::internal