[tor-bugs] #29805 [Core Tor/Tor]: 41 coverity defects on prob_distr.c

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#29805: 41 coverity defects on prob_distr.c
------------------------------+---------------------------------
     Reporter:  asn           |      Owner:  (none)
         Type:  defect        |     Status:  new
     Priority:  Medium        |  Milestone:  Tor: 0.4.1.x-final
    Component:  Core Tor/Tor  |    Version:
     Severity:  Normal        |   Keywords:  prob-distr coverity
Actual Points:                |  Parent ID:
       Points:                |   Reviewer:
      Sponsor:                |
------------------------------+---------------------------------
 The `DIST_BASE_TYPED` macro in `prob_distr.h` is causing us 41 new
 coverity defects. I don't think it's wrong but it's quite hacky so we
 should fix it in some way.

 {{{
 *** CID 1444029:  Incorrect expression  (SIZEOF_MISMATCH)
 /src/lib/math/prob_distr.c: 1511 in log_logistic_sf()
 1505       return cdf_log_logistic(x, LL->alpha, LL->beta);
 1506     }
 1507
 1508     static double
 1509     log_logistic_sf(const struct dist *dist, double x)
 1510     {
 >>>     CID 1444029:  Incorrect expression  (SIZEOF_MISMATCH)
 >>>     Adding "0UL /* 0 * sizeof (dist - &((struct log_logistic const
 *)((char const *)dist - __builtin_offsetof()))->base) */" to pointer
 >>> "(struct log_logistic const *)((char const *)dist - 0UL)" of type
 "struct log_logistic const *" is suspicious because adding an integral
 value
 >>> to this pointer automatically scales that value by the size, 24 bytes,
 of the pointed-to type, "struct log_logistic const".  Most likely, the
 >>> multiplication by "sizeof (dist - &((struct log_logistic const
 *)((char const *)dist - 0UL))->base)" in this expression is extraneous and
 >>> should be eliminated.
 1511       const struct log_logistic *LL = const_container_of(dist,
 1512         struct log_logistic, base);
 1513
 1514       return sf_log_logistic(x, LL->alpha, LL->beta);
 1515     }
 1516
 }}}

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/29805>
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