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  1. JDK
  2. JDK-8178348

left_n_bits(0) invokes undefined behavior

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    • b14
    • generic
    • generic

    Description

      The current definition of left_n_bits is

      #define left_n_bits(n) \
        (right_n_bits(n) << (((n) >= BitsPerWord) ? 0 : (BitsPerWord - (n))))

      When n == 0, this reduces to

        (right_n_bits(0) << BitsPerWord)

      According to C++03 5.8/2, the behavior of a shift expression is undefined if the right operand is greater than or equal to the length in bits of the promoted left operand. So a shift by BitsPerWord invokes undefined behavior.

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          relates to

          Bug - A problem which impairs or prevents the functions of the product. JDK-8233144 undefined behavior: signed integer overflow

          • P4 - Minor loss of function, or other problem where easy workaround is present.
          • Open

          Enhancement - null JDK-8169039 Add unit tests for BitMap search operations

          • P4 - Minor loss of function, or other problem where easy workaround is present.
          • Resolved

          Bug - A problem which impairs or prevents the functions of the product. JDK-8178352 BitMap::get_next_zero_offset may give wrong result on Mac

          • P4 - Minor loss of function, or other problem where easy workaround is present.
          • Resolved
          links to

          Commit Commit openjdk/jdk/4b5c664b

          Review Review openjdk/jdk/2944

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              hseigel Harold Seigel (Inactive)
              kbarrett Kim Barrett
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