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Re: Is this defined behavior?

From Tim Rentsch <tr.17687@z991.linuxsc.com>
Newsgroups comp.lang.c
Subject Re: Is this defined behavior?
Date 2024-02-03 00:44 -0800
Organization A noiseless patient Spider
Message-ID <8634ua9bts.fsf@linuxsc.com> (permalink)
References <7h8vN.323427$xHn7.112429@fx14.iad> <8734uaq19p.fsf@nosuchdomain.example.com>

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Keith Thompson <Keith.S.Thompson+u@gmail.com> writes:

> Anthony Cuozzo <anthony@cuozzo.us> writes:
>
>> Time T:  Add N to a uintptr_t
>>
>> Time T+1:  Subtract N from that same uintptr_t
>>
>> Questions:
>>
>> 1.  Is this behavior defined?
>
> Sure, why wouldn't it be?  uintptr_t is just an unsigned integer
> type.  The guarantees about converting to and from void* don't
> affect its arithmetic behavior.  Adding and then subtracting N
> yields the original value.

Extremely likely to hold.  A perverse implementation could choose
(IIANM) a uintptr_t whose integer conversion rank is less than
that of int, and that could mess things up.  In practical terms
though what you say is spot on.

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Thread

Is this defined behavior? Anthony Cuozzo <anthony@cuozzo.us> - 2024-02-02 10:56 -0500
  Re: Is this defined behavior? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2024-02-02 08:28 -0800
    Re: Is this defined behavior? Tim Rentsch <tr.17687@z991.linuxsc.com> - 2024-02-03 00:44 -0800
      Re: Is this defined behavior? Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2024-02-03 16:07 +0000
        Re: Is this defined behavior? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2024-02-03 13:41 -0800
          Re: Is this defined behavior? Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2024-02-04 03:18 +0000
            Re: Is this defined behavior? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2024-02-03 19:48 -0800
              Re: Is this defined behavior? Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2024-02-04 04:34 +0000
        Re: Is this defined behavior? David Brown <david.brown@hesbynett.no> - 2024-02-04 13:24 +0100
          Re: Is this defined behavior? Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2024-02-04 15:16 +0000
            Re: Is this defined behavior? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2024-02-04 13:31 -0800
              Re: Is this defined behavior? Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2024-02-04 23:18 +0000
                Re: Is this defined behavior? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2024-02-04 15:56 -0800
                Re: Is this defined behavior? gazelle@shell.xmission.com (Kenny McCormack) - 2024-02-05 00:05 +0000
                Re: Is this defined behavior? Poprocks <please@replytogroup.com> - 2024-02-05 13:35 -0500
                Re: Is this defined behavior? Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2024-02-06 13:10 +0000
                Is this sane behavior? (Was: Is this defined behavior?) gazelle@shell.xmission.com (Kenny McCormack) - 2024-02-06 14:52 +0000
                Re: Is this sane behavior? (Was: Is this defined behavior?) Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2024-02-06 15:50 +0000
              Re: Is this defined behavior? Tim Rentsch <tr.17687@z991.linuxsc.com> - 2024-02-04 23:21 -0800
          Re: Is this defined behavior? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2024-02-04 15:27 +0000
            Re: Is this defined behavior? David Brown <david.brown@hesbynett.no> - 2024-02-04 18:23 +0100

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