test/mjsunit/regress/regress-155924.js

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// A HeapNumber with certain bits in the mantissa of the floating point
// value should not be able to masquerade as a string in a keyed lookup
// inline cache stub.  See http://codereview.chromium.org/155924.

A = [ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 ];

function foo() {
  x = 1 << 26;
  x = x * x;
  // The following floating-point heap number has a second word similar
  // to that of the string "5":
  // 2^52 + index << cached_index_shift + cached_index_tag
  x = x + (5 << 2) + (1 << 1);
  return A[x];
}

assertEquals(undefined, foo(), "First lookup A[bad_float]");
assertEquals(undefined, foo(), "Second lookup A[bad_float]");
assertEquals(undefined, foo(), "Third lookup A[bad_float]");