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Groups > comp.lang.c > #73071

Re: Pointers, constant values

From Keith Thompson <kst-u@mib.org>
Newsgroups comp.lang.c
Subject Re: Pointers, constant values
Date 2015-10-16 13:41 -0700
Organization None to speak of
Message-ID <lnfv1a4kcj.fsf@kst-u.example.com> (permalink)
References (2 earlier) <mvr9nb$ra4$1@dont-email.me> <ln8u726308.fsf@kst-u.example.com> <mvrjar$2ji$1@dont-email.me> <lnpp0e4m7s.fsf@kst-u.example.com> <mvrle8$akl$1@dont-email.me>

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Bartc <bc@freeuk.com> writes:
> On 16/10/2015 21:01, Keith Thompson wrote:
>> Bartc <bc@freeuk.com> writes:
>>> It's a pointer to an unbounded array. You can do anything you like with
>>> it except anything involving its length. But int* doesn't have a length
>>> either.
>>
>> No, but int* specifies the size of the object it points to.  Given int
>> (*array)[], you don't even know the size of the element type.
>
> It's pointer to an array of int. The element size is the size of int.
>
>> $ cat c.c
>> int array_sum(int (*array)[], int n) {
>>      array[0];
>> }
>> $ gcc -c c.c
>> c.c: In function 'array_sum':
>> c.c:2: error: invalid use of array with unspecified bounds
>> $
>
> You forget to put in 'return'.

I didn't forget it.  My intent was to show that it doesn't compile,
regardless of how it's used.  However ...

>                                And you haven't dereferenced the array
> properly. Try writing it as:
>
>  return (*array)[0];
>
> I'm not suggested everyone does this, because just passing int
> pointers for arrays is simpler and is very widespread and well
> understood.
>
> But if the syntax wasn't so clunky, this ought to be the recommended
> way of passing pointers to arrays.

You're right, you had (*array)[i] in your previous article and I missed
it.  Never mind.

-- 
Keith Thompson (The_Other_Keith) kst-u@mib.org  <http://www.ghoti.net/~kst>
Working, but not speaking, for JetHead Development, Inc.
"We must do something.  This is something.  Therefore, we must do this."
    -- Antony Jay and Jonathan Lynn, "Yes Minister"

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Pointers, constant values Alla _ <modelling.data@gmail.com> - 2015-10-16 00:49 -0700
  Re: Pointers, constant values Philip Lantz <prl@canterey.us> - 2015-10-16 01:49 -0700
  Re: Pointers, constant values James Kuyper <jameskuyper@verizon.net> - 2015-10-16 09:41 -0400
    Re: Pointers, constant values supercat@casperkitty.com - 2015-10-16 08:55 -0700
  Re: Pointers, constant values Keith Thompson <kst-u@mib.org> - 2015-10-16 08:25 -0700
    Re: Pointers, constant values supercat@casperkitty.com - 2015-10-16 09:11 -0700
      Re: Pointers, constant values Keith Thompson <kst-u@mib.org> - 2015-10-16 12:06 -0700
        Re: Pointers, constant values supercat@casperkitty.com - 2015-10-16 12:55 -0700
    Re: Pointers, constant values Bartc <bc@freeuk.com> - 2015-10-16 17:49 +0100
      Re: Pointers, constant values Lew Pitcher <lew.pitcher@digitalfreehold.ca> - 2015-10-16 13:23 -0400
        Re: Pointers, constant values Bartc <bc@freeuk.com> - 2015-10-16 19:34 +0100
          Re: Pointers, constant values supercat@casperkitty.com - 2015-10-16 12:05 -0700
        Re: Pointers, constant values Keith Thompson <kst-u@mib.org> - 2015-10-16 12:18 -0700
      Re: Pointers, constant values Keith Thompson <kst-u@mib.org> - 2015-10-16 12:13 -0700
        Re: Pointers, constant values Bartc <bc@freeuk.com> - 2015-10-16 20:33 +0100
          Re: Pointers, constant values Keith Thompson <kst-u@mib.org> - 2015-10-16 13:01 -0700
            Re: Pointers, constant values Bartc <bc@freeuk.com> - 2015-10-16 21:09 +0100
              Re: Pointers, constant values Keith Thompson <kst-u@mib.org> - 2015-10-16 13:41 -0700
          Re: Pointers, constant values Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-10-16 21:07 +0100
            Re: Pointers, constant values Bartc <bc@freeuk.com> - 2015-10-16 21:20 +0100
              Re: Pointers, constant values Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-10-16 22:02 +0100
                Re: Pointers, constant values Bartc <bc@freeuk.com> - 2015-10-16 22:21 +0100
                Re: Pointers, constant values supercat@casperkitty.com - 2015-10-16 14:39 -0700
                Re: Pointers, constant values Keith Thompson <kst-u@mib.org> - 2015-10-16 15:26 -0700
                Re: Pointers, constant values supercat@casperkitty.com - 2015-10-16 15:44 -0700
                Re: Pointers, constant values Keith Thompson <kst-u@mib.org> - 2015-10-16 16:58 -0700
                Re: Pointers, constant values supercat@casperkitty.com - 2015-10-16 17:28 -0700
                Re: Pointers, constant values Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-10-16 22:50 +0100
                Re: Pointers, constant values supercat@casperkitty.com - 2015-10-16 15:14 -0700
                Re: Pointers, constant values Bartc <bc@freeuk.com> - 2015-10-17 01:23 +0100
                Re: Pointers, constant values Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-10-17 19:39 +0100
                Re: Pointers, constant values Bartc <bc@freeuk.com> - 2015-10-17 22:42 +0100
                Re: Pointers, constant values Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-10-18 00:31 +0100
                Re: Pointers, constant values Bartc <bc@freeuk.com> - 2015-10-18 02:11 +0100
                Re: Pointers, constant values Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-10-18 11:59 +0100
                Re: Pointers, constant values Bartc <bc@freeuk.com> - 2015-10-18 12:12 +0100
                Re: Pointers, constant values Bartc <bc@freeuk.com> - 2015-10-18 12:28 +0100
                Re: Pointers, constant values Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-10-18 23:16 +0100
                Re: Pointers, constant values Bartc <bc@freeuk.com> - 2015-10-18 23:34 +0100
                Re: Pointers, constant values Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-10-19 01:45 +0100
                Re: Pointers, constant values Bartc <bc@freeuk.com> - 2015-10-19 11:51 +0100
                Re: Pointers, constant values Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-10-19 12:55 +0100
                Re: Pointers, constant values Bartc <bc@freeuk.com> - 2015-10-19 13:51 +0100
                Re: Pointers, constant values Malcolm McLean <malcolm.mclean5@btinternet.com> - 2015-10-19 06:02 -0700
                Re: Pointers, constant values supercat@casperkitty.com - 2015-10-19 07:02 -0700
                Re: Pointers, constant values Bartc <bc@freeuk.com> - 2015-10-19 15:39 +0100
                Re: Pointers, constant values supercat@casperkitty.com - 2015-10-19 08:54 -0700
                Re: Pointers, constant values Malcolm McLean <malcolm.mclean5@btinternet.com> - 2015-10-19 09:14 -0700
                Re: Pointers, constant values supercat@casperkitty.com - 2015-10-19 10:21 -0700
                Re: Pointers, constant values Malcolm McLean <malcolm.mclean5@btinternet.com> - 2015-10-19 12:57 -0700
                Re: Pointers, constant values glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-10-19 21:20 +0000
                Re: Pointers, constant values supercat@casperkitty.com - 2015-10-20 20:50 -0700
                Re: Pointers, constant values glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-10-21 04:58 +0000
                Re: Pointers, constant values Keith Thompson <kst-u@mib.org> - 2015-10-19 08:40 -0700
                Re: Pointers, constant values Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-10-19 20:17 +0100
                Re: Pointers, constant values supercat@casperkitty.com - 2015-10-17 16:44 -0700
                Re: Pointers, constant values Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-10-18 11:52 +0100
                Re: Pointers, constant values Malcolm McLean <malcolm.mclean5@btinternet.com> - 2015-10-18 05:15 -0700
                Re: Pointers, constant values Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-10-18 21:54 +0100
                Re: Pointers, constant values Malcolm McLean <malcolm.mclean5@btinternet.com> - 2015-10-18 16:09 -0700
                Re: Pointers, constant values supercat@casperkitty.com - 2015-10-18 07:55 -0700
                Re: Pointers, constant values Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-10-18 21:47 +0100
                Re: Pointers, constant values supercat@casperkitty.com - 2015-10-18 15:37 -0700
                Re: Pointers, constant values Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-10-19 00:10 +0100
                Re: Pointers, constant values supercat@casperkitty.com - 2015-10-18 19:04 -0700
        Re: Pointers, constant values Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-10-16 21:13 +0100
      Re: Pointers, constant values Ian Collins <ian-news@hotmail.com> - 2015-10-17 11:27 +1300
        Re: Pointers, constant values Bartc <bc@freeuk.com> - 2015-10-17 00:56 +0100
  Re: Pointers, constant values Les Cargill <lcargill99@comcast.com> - 2015-10-16 12:37 -0500
    Re: Pointers, constant values James Kuyper <jameskuyper@verizon.net> - 2015-10-16 14:22 -0400
  Re: Pointers, constant values Jorgen Grahn <grahn+nntp@snipabacken.se> - 2015-10-16 18:57 +0000
    Re: Pointers, constant values Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-10-16 20:40 +0100
      Re: Pointers, constant values Jorgen Grahn <grahn+nntp@snipabacken.se> - 2015-10-16 20:46 +0000
        Re: Pointers, constant values Keith Thompson <kst-u@mib.org> - 2015-10-16 14:24 -0700
          Re: Pointers, constant values Jorgen Grahn <grahn+nntp@snipabacken.se> - 2015-10-19 12:43 +0000
  Re: Pointers, constant values Siri Cruz <chine.bleu@yahoo.com> - 2015-10-16 13:20 -0700
    Re: Pointers, constant values supercat@casperkitty.com - 2015-10-17 13:59 -0700

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