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Groups > comp.lang.c > #76344

Re: Issue on assigning address to pointers

From James Kuyper <jameskuyper@verizon.net>
Newsgroups comp.lang.c
Subject Re: Issue on assigning address to pointers
Date 2015-11-17 22:37 -0500
Organization A noiseless patient Spider
Message-ID <n2grlo$1fm$1@dont-email.me> (permalink)
References <dc62f43a-1725-496b-b36a-c3e196015b7d@googlegroups.com> <9ptm4b9aist9nba86pj9l086mamsqaa3or@4ax.com> <ln1tbojk96.fsf@kst-u.example.com> <v9kn4b1o9k56orbcg2dnu5hmoqn8eqlv17@4ax.com>

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On 11/17/2015 08:18 PM, Geoff wrote:
> On Tue, 17 Nov 2015 15:09:41 -0800, Keith Thompson <kst-u@mib.org>
> wrote:
> 
>> Geoff <geoff@invalid.invalid> writes:
>> [...]
>>> There are 8 elements in the numbers array, 0 through 7. Pointing to a
>>> ninth element is an error.
>>
>> As discussed previously, constructing the pointer is not an error, but
>> dereferencing it is.
>>
> Then let me amend my statement to read:
> There are 8 elements in the numbers array, 0 through 7. Pointing to a
> ninth element with the intent of doing anything with the contents is
> an error. The only thing that pointer is good for is --ptr.

No, such a pointer can also be compared for relative order with another
pointer into or one past the end of the same array. Testing for relative
order is in fact one of the most common uses of such a pointer:

    for(int *p = array; p < array+num_elements; p++)

It can also be tested for equality with any other valid pointer. Note
the a pointer one past the end of one array is allowed to compare equal
to "a pointer to the start of a different array object that happens to
immediately follow the first array object in the address space." (6.5.9p6).
-- 
James Kuyper

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Thread

Issue on assigning address to pointers Alla _ <modelling.data@gmail.com> - 2015-11-17 08:49 -0800
  Re: Issue on assigning address to pointers James Kuyper <jameskuyper@verizon.net> - 2015-11-17 12:36 -0500
    Re: Issue on assigning address to pointers Richard Heathfield <rjh@cpax.org.uk> - 2015-11-17 17:47 +0000
      Re: Issue on assigning address to pointers Alla _ <modelling.data@gmail.com> - 2015-11-17 10:34 -0800
        Re: Issue on assigning address to pointers Keith Thompson <kst-u@mib.org> - 2015-11-17 12:16 -0800
        Re: Issue on assigning address to pointers James Kuyper <jameskuyper@verizon.net> - 2015-11-17 15:23 -0500
    Re: Issue on assigning address to pointers Alla _ <modelling.data@gmail.com> - 2015-11-17 10:33 -0800
  Re: Issue on assigning address to pointers Keith Thompson <kst-u@mib.org> - 2015-11-17 09:41 -0800
    Re: Issue on assigning address to pointers Geoff <geoff@invalid.invalid> - 2015-11-17 10:03 -0800
      Re: Issue on assigning address to pointers glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-11-17 20:31 +0000
        Re: Issue on assigning address to pointers Geoff <geoff@invalid.invalid> - 2015-11-17 12:53 -0800
    Re: Issue on assigning address to pointers Alla _ <modelling.data@gmail.com> - 2015-11-17 10:32 -0800
      Re: Issue on assigning address to pointers Richard Heathfield <rjh@cpax.org.uk> - 2015-11-17 18:45 +0000
        Re: Issue on assigning address to pointers Alla _ <modelling.data@gmail.com> - 2015-11-17 10:53 -0800
        Re: Issue on assigning address to pointers Keith Thompson <kst-u@mib.org> - 2015-11-17 15:05 -0800
          Re: Issue on assigning address to pointers Philip Lantz <prl@canterey.us> - 2015-11-19 21:16 -0800
        Re: Issue on assigning address to pointers Anand Hariharan <mailto.anand.hariharan@gmail.com> - 2015-11-17 15:47 -0800
        Re: Issue on assigning address to pointers Barry Schwarz <schwarzb@dqel.com> - 2015-11-17 15:53 -0800
          Re: Issue on assigning address to pointers Richard Heathfield <rjh@cpax.org.uk> - 2015-11-18 04:05 +0000
      Re: Issue on assigning address to pointers Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-11-17 19:41 +0000
  Re: Issue on assigning address to pointers Stephen Sprunk <stephen@sprunk.org> - 2015-11-17 12:17 -0600
    Re: Issue on assigning address to pointers Richard Heathfield <rjh@cpax.org.uk> - 2015-11-17 18:21 +0000
      Re: Issue on assigning address to pointers Geoff <geoff@invalid.invalid> - 2015-11-17 10:36 -0800
        Re: Issue on assigning address to pointers Richard Heathfield <rjh@cpax.org.uk> - 2015-11-17 18:46 +0000
          Re: Issue on assigning address to pointers Alla _ <modelling.data@gmail.com> - 2015-11-17 10:49 -0800
        Re: Issue on assigning address to pointers Alla _ <modelling.data@gmail.com> - 2015-11-17 10:47 -0800
          Re: Issue on assigning address to pointers Richard Heathfield <rjh@cpax.org.uk> - 2015-11-17 18:51 +0000
            Re: Issue on assigning address to pointers Alla _ <modelling.data@gmail.com> - 2015-11-17 10:55 -0800
          Re: Issue on assigning address to pointers Geoff <geoff@invalid.invalid> - 2015-11-17 11:59 -0800
      Re: Issue on assigning address to pointers Stephen Sprunk <stephen@sprunk.org> - 2015-11-17 12:58 -0600
        Re: Issue on assigning address to pointers Richard Heathfield <rjh@cpax.org.uk> - 2015-11-17 19:12 +0000
      Re: Issue on assigning address to pointers Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-11-17 19:33 +0000
    Re: Issue on assigning address to pointers Lew Pitcher <lew.pitcher@digitalfreehold.ca> - 2015-11-17 13:25 -0500
  Re: Issue on assigning address to pointers Richard Heathfield <rjh@cpax.org.uk> - 2015-11-17 18:31 +0000
    Re: Issue on assigning address to pointers Alla _ <modelling.data@gmail.com> - 2015-11-17 10:39 -0800
    Re: Issue on assigning address to pointers Alla _ <modelling.data@gmail.com> - 2015-11-17 10:40 -0800
      Re: Issue on assigning address to pointers Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-11-17 19:40 +0000
  Re: Issue on assigning address to pointers Geoff <geoff@invalid.invalid> - 2015-11-17 11:15 -0800
    Re: Issue on assigning address to pointers James Kuyper <jameskuyper@verizon.net> - 2015-11-17 15:32 -0500
    Re: Issue on assigning address to pointers Keith Thompson <kst-u@mib.org> - 2015-11-17 15:09 -0800
      Re: Issue on assigning address to pointers supercat@casperkitty.com - 2015-11-17 15:41 -0800
        Re: Issue on assigning address to pointers Malcolm McLean <malcolm.mclean5@btinternet.com> - 2015-11-17 21:28 -0800
          Re: Issue on assigning address to pointers supercat@casperkitty.com - 2015-11-17 23:18 -0800
      Re: Issue on assigning address to pointers Geoff <geoff@invalid.invalid> - 2015-11-17 17:18 -0800
        Re: Issue on assigning address to pointers James Kuyper <jameskuyper@verizon.net> - 2015-11-17 22:37 -0500
  Re: Issue on assigning address to pointers Lőrinczy Zsigmond <zsiga@nospam.for.me> - 2015-11-18 11:27 +0100
    Re: Issue on assigning address to pointers Keith Thompson <kst-u@mib.org> - 2015-11-18 06:13 -0800
  Re: Issue on assigning address to pointers guinness.tony@gmail.com - 2015-11-24 02:46 -0800
    Re: Issue on assigning address to pointers Keith Thompson <kst-u@mib.org> - 2015-11-24 09:21 -0800
  Re: Issue on assigning address to pointers John Bode <jfbode1029@gmail.com> - 2015-11-24 05:01 -0800
    Re: Issue on assigning address to pointers Keith Thompson <kst-u@mib.org> - 2015-11-24 09:22 -0800
  Re: Issue on assigning address to pointers John Bode <jfbode1029@gmail.com> - 2015-11-24 06:47 -0800
    Re: Issue on assigning address to pointers Alla _ <modelling.data@gmail.com> - 2015-11-25 06:44 -0800

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