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  1. Thrift
  2. THRIFT-5355

Do not rely on compiler and check boundaries

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    Details

    • Type: Improvement
    • Status: Closed
    • Priority: Major
    • Resolution: Fixed
    • Affects Version/s: None
    • Fix Version/s: 0.15.0
    • Component/s: C++ - Library
    • Labels:
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      Description

      C++ considers the overflow of a signed integer to be an undefined behavior (even with the "Signed Integers are Two's Complement" update: http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2018/p0907r1.html ).

      Instead of relying on tests(1) to discover if a compiler does not handle the signed integer overflow as we expect it to, we should add an explicit check before incrementing.

      (1) See
      thrift/lib/cpp/src/thrift/async/TConcurrentClientSyncInfo.cpp

      Lines 33 to 34 in c4e899a

        // test rollover all the time
        nextseqid_((std::numeric_limits<int32_t>::max)()-10),

       

      Quick check on https://godbolt.org/z/d7W8ds shows that Clang is able to optimize and just do the +1 so modern compilers should be able to keep the same performances where hardware permits.

      In addition, some company rules might require code to do just that:
      https://wiki.sei.cmu.edu/confluence/display/c/INT32-C.+Ensure+that+operations+on+signed+integers+do+not+result+in+overflow

       

       

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              • Assignee:
                jensg Jens Geyer
                Reporter:
                jensg Jens Geyer
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