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Groups > comp.lang.c > #140354

Re: Distributing C as headers.

From David Brown <david.brown@hesbynett.no>
Newsgroups comp.lang.c
Subject Re: Distributing C as headers.
Date 2019-01-28 13:23 +0100
Organization A noiseless patient Spider
Message-ID <q2ms8d$cd5$1@dont-email.me> (permalink)
References (16 earlier) <OTr3E.154256$592.32298@fx16.am4> <87bm41vb3k.fsf@bsb.me.uk> <10t3E.125278$9A2.93679@fx09.am4> <8736pdv80w.fsf@bsb.me.uk> <m2y375c9it.fsf@despina.home>

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On 28/01/2019 12:21, Pascal J. Bourguignon wrote:
> Ben Bacarisse <ben.usenet@bsb.me.uk> writes:
> 
>> Bart <bc@freeuk.com> writes:
>>
>>> On 28/01/2019 01:12, Ben Bacarisse wrote:
>>>> Bart <bc@freeuk.com> writes:
>>>>
>>>>> On 28/01/2019 00:06, Bart wrote:
>>>>>> On 27/01/2019 23:51, Pascal J. Bourguignon wrote:
>>>>>
>>>>>>> In C, you need a lot more information to be able to use the header.
>>>>>>> In Pascal, you have all the information you need:
>>>>>>>
>>>>>>>      var
>>>>>>>         dst:string;
>>>>>>>      begin
>>>>>>>        string_copy(dst,'Hello World');
>>>>>>>      end;
>>>>>>>
>>>>>>> will work without crashing.
>>>>>>
>>>>>> What would string_copy(dst, dst) do? What is the capacity of dst?
>>>>>> (Last time I used Pascal, strings had to have a fixed length.)
>>>>>
>>>>> I couldn't compile your Pascal code. Do you have a real, complete
>>>>> example that will run? I have Free Pascal Compiler.
>>>>
>>>> This is a runable example, though I have no idea if it illustrates
>>>> whatever point was being made:
>>>>
>>>> program copystring (output);
>>>> procedure string_copy(var dst : string; src : string);
>>>> begin
>>>>     dst := src
>>>> end;
>>>> var dst : string;
>>>> begin
>>>>     string_copy(dst, 'Hello World');
>>>>     write(dst)
>>>> end.
>>>
>>> Thanks. I think the point was that you couldn't make a Pascal program crash, as the interfaces are more robust. However if I modify your example to:
>>>
>>>    program copystring (output);
>>>    procedure string_copy(var dst : string; src : string);
>>>    begin
>>>       string_copy(dst,src)
>>>    end;
>>>    var dst : string;
>>>    begin
>>>       string_copy(dst, 'Hello World');
>>>       write(dst)
>>>    end.
>>>
>>> then run via FPC it gives me:
>>>
>>>  Runtime error 202 at $0040142E
>>>   $0040142E
>>>   $00401441
>>>   $00401441
>>>   $00401441
>>>   $00401441
>>>   $00401441
>>>   $00401441
>>>   $00401441
>>>   $00401441
>>>   $00401441
>>>
>>> (at a wild guess, it's run out of stack). I would say that it has
>>> crashed.
>>
>> I went and looked.  James was talking about pointers so a more direct
>> example might be this:
>>
>> program copystring (output);
>> procedure string_copy(var dst : string; src : string);
>> begin
>>    dst := src
>> end;
>> var dp : ^string;
>> begin
>>    string_copy(dp^, 'Hello World');
>>    write(dp^)
>> end.
> 
> Part of the point that you could avoid using pointer in non-C
> programming languages.  There are constructs such as passing arguments
> by reference, or using opaque objects (such as string) instead of bare
> pointers to characters with some missing attribute such as allocated
> size or length that must be passed on the side, which is propice to
> errors, and ultimately crashes.
> 
> 

When you are passing references in other languages, the underlying
implementation is still passing around pointers.  You can do the same in
C - wrap your pointers inside structs, use access functions or macros.
The difference is that in C you need to make these yourself and you
don't get as neat syntax.

Since you talk about "C programming languages" plural, are you including
C++ ?  In C++ you can pass by reference, make classes such as string,
etc. - and you can get a result that is both faster and safer than with
Pascal.

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Thread

Distributing C as headers. Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2019-01-25 07:23 -0800
  Re: Distributing C as headers. Thiago Adams <thiago.adams@gmail.com> - 2019-01-25 07:31 -0800
    Re: Distributing C as headers. Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2019-01-25 07:33 -0800
      Re: Distributing C as headers. Mateusz Viste <mateusz@wont.tell> - 2019-01-25 15:42 +0000
      Re: Distributing C as headers. gazelle@shell.xmission.com (Kenny McCormack) - 2019-01-25 17:40 +0000
        Re: Distributing C as headers. Thiago Adams <thiago.adams@gmail.com> - 2019-01-25 09:59 -0800
          Re: Distributing C as headers. Thiago Adams <thiago.adams@gmail.com> - 2019-01-25 10:01 -0800
          Re: Distributing C as headers. David Brown <david.brown@hesbynett.no> - 2019-01-25 22:17 +0100
            Re: Distributing C as headers. Bart <bc@freeuk.com> - 2019-01-25 21:33 +0000
        Re: Distributing C as headers. Mateusz Viste <mateusz@wont.tell> - 2019-01-25 18:07 +0000
          Re: Distributing C as headers. gazelle@shell.xmission.com (Kenny McCormack) - 2019-01-25 18:46 +0000
            Re: Distributing C as headers. Joe Pfeiffer <pfeiffer@cs.nmsu.edu> - 2019-01-25 19:43 -0700
              Re: Distributing C as headers. Mateusz Viste <mateusz@wont.tell> - 2019-01-26 08:13 +0000
                Re: Distributing C as headers. Joe Pfeiffer <pfeiffer@cs.nmsu.edu> - 2019-01-26 13:39 -0700
                Re: Distributing C as headers. Mateusz Viste <mateusz@wont.tell> - 2019-01-26 21:00 +0000
                Re: Distributing C as headers. "Pascal J. Bourguignon" <pjb@informatimago.com> - 2019-01-26 22:29 +0100
                Re: Distributing C as headers. nobody@example.org (Scott) - 2019-01-27 04:56 +0000
                Re: Distributing C as headers. Dan Purgert <dan@djph.net> - 2019-01-27 11:36 +0000
                Re: Distributing C as headers. Tim Rentsch <tr.17687@z991.linuxsc.com> - 2019-02-25 12:26 -0800
                Re: Distributing C as headers. "Jason C. McDonald" <indeliblebluepen@gmail.com> - 2019-02-28 19:52 +0000
                Re: Distributing C as headers. Lew Pitcher <lew.pitcher@digitalfreehold.ca> - 2019-02-28 15:04 -0500
                Re: Distributing C as headers. "Pascal J. Bourguignon" <pjb@informatimago.com> - 2019-02-28 21:40 +0100
                Re: Distributing C as headers. James Kuyper <jameskuyper@alumni.caltech.edu> - 2019-02-28 13:57 -0800
                Re: Distributing C as headers. Jorgen Grahn <grahn+nntp@snipabacken.se> - 2019-01-27 13:33 +0000
                Re: Distributing C as headers. David Brown <david.brown@hesbynett.no> - 2019-01-27 15:06 +0100
                Re: Distributing C as headers. luser droog <luser.droog@gmail.com> - 2019-01-26 13:01 -0800
                Re: Distributing C as headers. "Pascal J. Bourguignon" <pjb@informatimago.com> - 2019-01-26 22:30 +0100
                Re: Distributing C as headers. Jorgen Grahn <grahn+nntp@snipabacken.se> - 2019-02-02 09:27 +0000
                Re: Distributing C as headers. "Pascal J. Bourguignon" <pjb@informatimago.com> - 2019-01-26 22:23 +0100
                Re: Distributing C as headers. Keith Thompson <kst-u@mib.org> - 2019-01-26 13:39 -0800
                Re: Distributing C as headers. "Pascal J. Bourguignon" <pjb@informatimago.com> - 2019-01-26 22:47 +0100
                Re: Distributing C as headers. Keith Thompson <kst-u@mib.org> - 2019-01-26 14:33 -0800
                Re: Distributing C as headers. "Pascal J. Bourguignon" <pjb@informatimago.com> - 2019-01-26 23:37 +0100
                Re: Distributing C as headers. Keith Thompson <kst-u@mib.org> - 2019-01-26 15:09 -0800
                Re: Distributing C as headers. David Brown <david.brown@hesbynett.no> - 2019-01-27 15:11 +0100
                Re: Distributing C as headers. James Kuyper <jameskuyper@alumni.caltech.edu> - 2019-01-27 16:12 -0500
                Re: Distributing C as headers. "Pascal J. Bourguignon" <pjb@informatimago.com> - 2019-01-28 00:51 +0100
                Re: Distributing C as headers. Bart <bc@freeuk.com> - 2019-01-28 00:06 +0000
                Re: Distributing C as headers. Bart <bc@freeuk.com> - 2019-01-28 00:18 +0000
                Re: Distributing C as headers. Ben Bacarisse <ben.usenet@bsb.me.uk> - 2019-01-28 01:12 +0000
                Re: Distributing C as headers. Bart <bc@freeuk.com> - 2019-01-28 01:35 +0000
                Re: Distributing C as headers. Ben Bacarisse <ben.usenet@bsb.me.uk> - 2019-01-28 02:19 +0000
                Re: Distributing C as headers. Bart <bc@freeuk.com> - 2019-01-28 10:40 +0000
                Re: Distributing C as headers. "Pascal J. Bourguignon" <pjb@informatimago.com> - 2019-01-28 12:22 +0100
                Re: Distributing C as headers. "Pascal J. Bourguignon" <pjb@informatimago.com> - 2019-01-28 12:21 +0100
                Re: Distributing C as headers. Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2019-01-28 04:03 -0800
                Re: Distributing C as headers. David Brown <david.brown@hesbynett.no> - 2019-01-28 13:23 +0100
                Re: Distributing C as headers. Keith Thompson <kst-u@mib.org> - 2019-01-28 11:16 -0800
                Re: Distributing C as headers. David Brown <david.brown@hesbynett.no> - 2019-01-28 21:08 +0100
                Re: Distributing C as headers. "Pascal J. Bourguignon" <pjb@informatimago.com> - 2019-01-28 01:19 +0100
                Re: Distributing C as headers. Keith Thompson <kst-u@mib.org> - 2019-01-27 16:59 -0800
                Re: Distributing C as headers. Keith Thompson <kst-u@mib.org> - 2019-01-27 16:33 -0800
                Re: Distributing C as headers. "Pascal J. Bourguignon" <pjb@informatimago.com> - 2019-01-28 01:35 +0100
                Re: Distributing C as headers. Keith Thompson <kst-u@mib.org> - 2019-01-27 17:20 -0800
                Re: Distributing C as headers. James Kuyper <jameskuyper@alumni.caltech.edu> - 2019-01-27 22:50 -0500
                Re: Distributing C as headers. David Brown <david.brown@hesbynett.no> - 2019-01-28 06:52 +0100
                Re: Distributing C as headers. Bart <bc@freeuk.com> - 2019-01-28 10:55 +0000
                Re: Distributing C as headers. "Pascal J. Bourguignon" <pjb@informatimago.com> - 2019-01-28 12:26 +0100
                Re: Distributing C as headers. David Brown <david.brown@hesbynett.no> - 2019-01-28 13:27 +0100
                Re: Distributing C as headers. David Brown <david.brown@hesbynett.no> - 2019-01-28 13:26 +0100
                Re: Distributing C as headers. "Pascal J. Bourguignon" <pjb@informatimago.com> - 2019-01-28 14:03 +0100
                Re: Distributing C as headers. Keith Thompson <kst-u@mib.org> - 2019-01-28 11:12 -0800
                Re: Distributing C as headers. "Pascal J. Bourguignon" <pjb@informatimago.com> - 2019-01-28 12:25 +0100
                Re: Distributing C as headers. David Brown <david.brown@hesbynett.no> - 2019-01-28 13:33 +0100
                Re: Distributing C as headers. Keith Thompson <kst-u@mib.org> - 2019-01-28 11:20 -0800
                Re: Distributing C as headers. David Brown <david.brown@hesbynett.no> - 2019-01-28 21:11 +0100
                Re: Distributing C as headers. scott@slp53.sl.home (Scott Lurndal) - 2019-01-28 21:12 +0000
                Re: Distributing C as headers. David Brown <david.brown@hesbynett.no> - 2019-01-28 23:06 +0100
                Re: Distributing C as headers. David Brown <david.brown@hesbynett.no> - 2019-01-27 15:02 +0100
    Re: Distributing C as headers. "Pascal J. Bourguignon" <pjb@informatimago.com> - 2019-01-25 17:51 +0100
    Re: Distributing C as headers. fir <profesor.fir@gmail.com> - 2019-01-25 14:28 -0800

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