[tor-bugs] #13104 [Tor]: [patch] Arithmetic undef behaviour: sscanf, memeq, scale array, fmt exit status

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#13104: [patch] Arithmetic undef behaviour: sscanf, memeq, scale array, fmt exit
status
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     Reporter:  teor    |      Owner:
         Type:  defect  |     Status:  needs_review
     Priority:  normal  |  Milestone:  Tor: 0.2.6.x-final
    Component:  Tor     |    Version:  Tor: 0.2.5.5-alpha
   Resolution:          |   Keywords:  tor-router 025-backport
Actual Points:          |  Parent ID:
       Points:          |
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Comment (by teor):

 Yes, you're right, unsigned integer underflow is defined in C11 as modulo
 (UINT_TYPE_MAX + 1):

   6.3.1.3, paragraph 2 [ISO/IEC 9899:2011]:
   Otherwise, if the new type is unsigned, the value is converted by
 repeatedly adding or subtracting one more than the maximum value that can
 be represented in the new type until the value is in the range of the new
 type.

 I think this was probably a build configuration issue on my end. It looks
 like I managed to slip in -fsanitize=unsigned-integer-overflow in my tests
 on di_ops.c, then remove it again shortly afterwards. I can't reproduce
 the same error with the original code and my current build flags.

 I'm sorry about that, I'll replace the di_ops patch with one that simply
 adds the new tests, and doesn't change any tor code.

--
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/13104#comment:3>
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