test/mjsunit/copy-on-write-assert.js

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function createLargeCOWArray() {
  var s = "[0";
  // The constant below depends on the max object size in new space.
  for (var i = 0; i < (128 << 10); i++) {
    s += ",0";
  }
  s += "]";
  return eval(s);
}

var large_cow_array = createLargeCOWArray();

// Force copy. Because the array is large it will test the slow array
// cloning in large object space.
large_cow_array[17] = 42;