[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
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 Reporter:  asn                  |          Owner:  (none)
     Type:  defect               |         Status:  new
 Priority:  Medium               |      Milestone:  Tor: 0.4.1.x-final
Component:  Core Tor/Tor         |        Version:
 Severity:  Normal               |     Resolution:
 Keywords:  prob-distr coverity  |  Actual Points:
Parent ID:                       |         Points:
 Reviewer:                       |        Sponsor:
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Comment (by catalyst):

 Summarizing some analysis that asn and I did on IRC, plus some more
 comments from me:

 For the `DIST_BASE_TYPED` cases (not quoted here?), Coverity is apparently
 complaining about the multiplication of an integer by the result of a
 `sizeof` operator, which I think is possibly a helpful warning where the
 integer is nonzero.

 This appears to be a type-checking hack that functions by making a
 compile-time assertion. The type checking works by subtracting `&(OBJ)`
 and the same pointer cast to `const TYPE *`, which is a C constraint
 violation if the types aren't the same.  At a minimum, I think we should
 move the type-checking hack to a helper macro, and document everything
 better in comments.

 Maybe directly adding the result of the pointer subtraction (which should
 always be zero) will be enough to quiet Coverity. Discarding the
 subtraction result by using a comma operator probably also works (if the
 macro isn't used in a static initializer).

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/29805#comment:2>
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