Re: Is there any place to talk about language features?

From	Ian Collins <ian-news@hotmail.com>
Newsgroups	comp.lang.c
Subject	Re: Is there any place to talk about language features?
Date	2016-10-02 20:38 +1300
Message-ID	<e5brqtF4ag4U1@mid.individual.net> (permalink)
References	(11 earlier) <3e7e20c2-c69d-4777-a98a-b7d212f546c9@googlegroups.com> <e57rk4Fa94uU1@mid.individual.net> <c7787c1f-f39c-499f-8d93-1caa13d4c005@googlegroups.com> <e59h3bFkp66U1@mid.individual.net> <a3ba260b-f6ab-4677-9073-c7c9866c7232@googlegroups.com>

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On 10/ 2/16 02:15 AM, Malcolm McLean wrote:
> On Saturday, October 1, 2016 at 11:22:42 AM UTC+1, Ian Collins wrote:
>> On 10/ 1/16 09:51 PM, Malcolm McLean wrote:
>>> On Friday, September 30, 2016 at 8:10:05 PM UTC+1, Ian Collins wrote:
>>>>
>>>> It all comes down to where the complexity required to manage a task
>>>> lies: in user code in C or in the language in C++.
>>>>
>>> In C we can use this pattern.
>>>
>>> a) Variables may not be declared in block scope, only function scope.
>>> (only really matters for pointer and handles, but make it all).
>>> b) Every pointer or handle is initialised to null.
>>> c) There is a label called "out_of_memory" (for a "Malcolm function,
>>> which can only fail on out of memory conditions and for no other
>>> reason) or "error_exit" (for a "Malcolm procedure" which does IO
>>> and can experience IO failure).
>>> d) out_of_memory or error_exit is jumped to on memory allocation
>>> or IO failure.
>>> e) code the error label destroys all resources, which will be null
>>> if not intialised.
>>> f) In the usual situation of an failure also meaning a failure in
>>> caller, an error return must be passed up. So normally if the function
>>> return a pointer it returns null, otherwise it returns -1 for
>>> out-of memory, or a lower negative for IO errors.
>>>
>>>
>>> Simple rules, not very complex or hard to follow.
>>
>> Simple but fallible rules for simple use cases of simple resources.
>> Life gets way more interesting when those simple things become a little
>> more complicated.
>>
>>> The only real point of difficulty is that when allocating a structure
>>> which itself contains pointers to be allocated, those pointers must
>>> immediately be set to null so the destructor logic doesn't free
>>> wild pointers.
>>
>> You overlook the fact that many if not most resource allocation and
>> release happens in different parts of a programme.
>>
> There's also the structure pattern. A graph is created, then nodes and
> edges are added and deleted as the algorithm does its stuff. So
> obviously memory has to be allocated at the point a node is created
> and released at the point it is destroyed. But everything should
> be accessible from the root, and at every time it ought to be
> possible to destroy the entire structure by calling the destructor
> on the root.

A good example of where this gets a little more complicated is where 
there are multiple references to a node or nodes.  XML DOM manipulation 
is one such case.  Then you need reference counting (or possibly GC) 
which is something else that has to be manually maintained (in C, not C++!).

> The trick is to use structured programming. Each "block" (which is
> similar to but not identical to a C curly braces block") has one
> point of entry and one point of exit. So creation and destruction
> are matched. A block either destroys all the resources it holds
> on exit, or passes them up to caller. If it passes them up to caller,
> it must be matched by a "destructor" function, which caller must
> call on his own exit (or pass them up to super-caller, and provide
> a destructor of his own, which then calls the destructor).
>
> Where it does get more difficult is where you have threads.

You don't even need threads: just storing stored items for later 
consumption breaks your simple use case.

-- 
Ian

Thread

Is there any place to talk about language features? Thiago Adams <thiago.adams@gmail.com> - 2016-09-28 09:35 -0700
  Re: Is there any place to talk about language features? Keith Thompson <kst-u@mib.org> - 2016-09-28 09:39 -0700
    Re: Is there any place to talk about language features? Thiago Adams <thiago.adams@gmail.com> - 2016-09-28 09:46 -0700
      Re: Is there any place to talk about language features? Richard Heathfield <rjh@cpax.org.uk> - 2016-09-28 17:53 +0100
      Re: Is there any place to talk about language features? David Brown <david.brown@hesbynett.no> - 2016-09-28 21:21 +0200
      Re: Is there any place to talk about language features? BartC <bc@freeuk.com> - 2016-09-28 20:36 +0100
        Re: Is there any place to talk about language features? Thiago Adams <thiago.adams@gmail.com> - 2016-09-28 13:55 -0700
          Re: Is there any place to talk about language features? Thiago Adams <thiago.adams@gmail.com> - 2016-09-28 14:02 -0700
          Re: Is there any place to talk about language features? Ian Collins <ian-news@hotmail.com> - 2016-09-29 10:03 +1300
            Re: Is there any place to talk about language features? Thiago Adams <thiago.adams@gmail.com> - 2016-09-28 14:13 -0700
              Re: Is there any place to talk about language features? Ian Collins <ian-news@hotmail.com> - 2016-09-29 10:22 +1300
                Re: Is there any place to talk about language features? Robert Latest <boblatest@yahoo.com> - 2016-10-03 08:47 +0000
                Re: Is there any place to talk about language features? James Kuyper <jameskuyper@verizon.net> - 2016-10-03 07:44 -0400
                Re: Is there any place to talk about language features? Malcolm McLean <malcolm.mclean5@btinternet.com> - 2016-10-03 04:56 -0700
                Re: Is there any place to talk about language features? BartC <bc@freeuk.com> - 2016-10-03 13:18 +0100
                Re: Is there any place to talk about language features? BGB <cr88192@hotmail.com> - 2016-10-03 12:43 -0500
                Re: Is there any place to talk about language features? Ike Naar <ike@iceland.freeshell.org> - 2016-10-03 21:43 +0000
                Re: Is there any place to talk about language features? John Gordon <gordon@panix.com> - 2016-10-03 22:28 +0000
                Re: Is there any place to talk about language features? Thiago Adams <thiago.adams@gmail.com> - 2016-10-03 04:51 -0700
                Re: Is there any place to talk about language features? BartC <bc@freeuk.com> - 2016-10-03 13:10 +0100
                Re: Is there any place to talk about language features? Malcolm McLean <malcolm.mclean5@btinternet.com> - 2016-10-03 05:48 -0700
                Re: Is there any place to talk about language features? BartC <bc@freeuk.com> - 2016-10-03 14:03 +0100
                Re: Is there any place to talk about language features? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2016-10-03 14:24 +0100
                Re: Is there any place to talk about language features? Malcolm McLean <malcolm.mclean5@btinternet.com> - 2016-10-03 07:07 -0700
                Re: Is there any place to talk about language features? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2016-10-03 19:16 +0100
                Re: Is there any place to talk about language features? Malcolm McLean <malcolm.mclean5@btinternet.com> - 2016-10-03 07:16 -0700
                Re: Is there any place to talk about language features? supercat@casperkitty.com - 2016-10-03 07:45 -0700
                Re: Is there any place to talk about language features? supercat@casperkitty.com - 2016-10-03 07:57 -0700
                Re: Is there any place to talk about language features? James Kuyper <jameskuyper@verizon.net> - 2016-10-03 08:21 -0400
                Re: Is there any place to talk about language features? Thiago Adams <thiago.adams@gmail.com> - 2016-10-03 05:31 -0700
                Re: Is there any place to talk about language features? supercat@casperkitty.com - 2016-10-03 06:43 -0700
                Re: Is there any place to talk about language features? David Brown <david.brown@hesbynett.no> - 2016-10-03 15:08 +0200
              Re: Is there any place to talk about language features? Thiago Adams <thiago.adams@gmail.com> - 2016-09-28 14:22 -0700
                Re: Is there any place to talk about language features? Keith Thompson <kst-u@mib.org> - 2016-09-28 15:16 -0700
                Re: Is there any place to talk about language features? Thiago Adams <thiago.adams@gmail.com> - 2016-09-28 16:08 -0700
                Re: Is there any place to talk about language features? Keith Thompson <kst-u@mib.org> - 2016-09-28 16:57 -0700
          Re: Is there any place to talk about language features? Keith Thompson <kst-u@mib.org> - 2016-09-28 14:19 -0700
            Re: Is there any place to talk about language features? Thiago Adams <thiago.adams@gmail.com> - 2016-09-28 14:50 -0700
              Re: Is there any place to talk about language features? Thiago Adams <thiago.adams@gmail.com> - 2016-09-28 17:03 -0700
              Re: Is there any place to talk about language features? BartC <bc@freeuk.com> - 2016-09-29 01:08 +0100
                Re: Is there any place to talk about language features? Thiago Adams <thiago.adams@gmail.com> - 2016-09-28 17:33 -0700
                Re: Is there any place to talk about language features? Melzzzzz <Melzzzzz@zzzzz.com> - 2016-09-29 01:02 +0000
                Re: Is there any place to talk about language features? BGB <cr88192@hotmail.com> - 2016-09-29 01:39 -0500
                Re: Is there any place to talk about language features? Malcolm McLean <malcolm.mclean5@btinternet.com> - 2016-09-29 00:48 -0700
                Re: Is there any place to talk about language features? BGB <cr88192@hotmail.com> - 2016-09-29 11:59 -0500
                Re: Is there any place to talk about language features? Ian Collins <ian-news@hotmail.com> - 2016-10-01 08:09 +1300
                Re: Is there any place to talk about language features? Thiago Adams <thiago.adams@gmail.com> - 2016-09-30 12:14 -0700
                Re: Is there any place to talk about language features? Ian Collins <ian-news@hotmail.com> - 2016-10-01 09:07 +1300
                Re: Is there any place to talk about language features? Thiago Adams <thiago.adams@gmail.com> - 2016-09-30 13:53 -0700
                Re: Is there any place to talk about language features? Gareth Owen <gwowen@gmail.com> - 2016-09-30 22:13 +0100
                Re: Is there any place to talk about language features? raltbos@xs4all.nl (Richard Bos) - 2016-10-01 09:36 +0000
                Re: Is there any place to talk about language features? Jerry Stuckle <jstucklex@attglobal.net> - 2016-10-01 13:04 -0400
                Re: Is there any place to talk about language features? "Chris M. Thomasson" <invalid@invalid.invalid> - 2016-09-30 14:20 -0700
                Re: Is there any place to talk about language features? BartC <bc@freeuk.com> - 2016-09-30 22:30 +0100
                Re: Is there any place to talk about language features? Jorgen Grahn <grahn+nntp@snipabacken.se> - 2016-10-02 07:30 +0000
                Re: Is there any place to talk about language features? Malcolm McLean <malcolm.mclean5@btinternet.com> - 2016-10-01 01:51 -0700
                Re: Is there any place to talk about language features? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2016-10-01 10:31 +0100
                Re: Is there any place to talk about language features? Ian Collins <ian-news@hotmail.com> - 2016-10-01 23:22 +1300
                Re: Is there any place to talk about language features? Malcolm McLean <malcolm.mclean5@btinternet.com> - 2016-10-01 06:15 -0700
                Re: Is there any place to talk about language features? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2016-10-01 15:28 +0100
                Re: Is there any place to talk about language features? Malcolm McLean <malcolm.mclean5@btinternet.com> - 2016-10-01 10:07 -0700
                Re: Is there any place to talk about language features? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2016-10-01 19:52 +0100
                Re: Is there any place to talk about language features? Ian Collins <ian-news@hotmail.com> - 2016-10-02 20:38 +1300
                Re: Is there any place to talk about language features? Malcolm McLean <malcolm.mclean5@btinternet.com> - 2016-10-02 03:37 -0700
                Re: Is there any place to talk about language features? Ian Collins <ian-news@hotmail.com> - 2016-10-03 08:35 +1300
                Re: Is there any place to talk about language features? Malcolm McLean <malcolm.mclean5@btinternet.com> - 2016-10-02 15:17 -0700
                Re: Is there any place to talk about language features? Ian Collins <ian-news@hotmail.com> - 2016-10-03 18:29 +1300
                Re: Is there any place to talk about language features? Malcolm McLean <malcolm.mclean5@btinternet.com> - 2016-10-03 01:09 -0700
                Re: Is there any place to talk about language features? Ian Collins <ian-news@hotmail.com> - 2016-10-04 08:21 +1300
                Re: Is there any place to talk about language features? Malcolm McLean <malcolm.mclean5@btinternet.com> - 2016-10-03 13:12 -0700
                Re: Is there any place to talk about language features? supercat@casperkitty.com - 2016-10-03 14:34 -0700
                Re: Is there any place to talk about language features? Malcolm McLean <malcolm.mclean5@btinternet.com> - 2016-10-04 00:47 -0700
                Re: Is there any place to talk about language features? Ike Naar <ike@iceland.freeshell.org> - 2016-10-04 07:49 +0000
                Re: Is there any place to talk about language features? supercat@casperkitty.com - 2016-10-04 07:50 -0700
                Re: Is there any place to talk about language features? Keith Thompson <kst-u@mib.org> - 2016-10-04 08:57 -0700
                Re: Is there any place to talk about language features? supercat@casperkitty.com - 2016-10-04 10:42 -0700
                Re: Is there any place to talk about language features? Ian Collins <ian-news@hotmail.com> - 2016-10-05 15:47 +1300
                Re: Is there any place to talk about language features? Malcolm McLean <malcolm.mclean5@btinternet.com> - 2016-10-04 20:58 -0700
                Re: Is there any place to talk about language features? Ian Collins <ian-news@hotmail.com> - 2016-10-05 18:14 +1300
                Re: Is there any place to talk about language features? Malcolm McLean <malcolm.mclean5@btinternet.com> - 2016-10-05 02:15 -0700
                Re: Is there any place to talk about language features? Ian Collins <ian-news@hotmail.com> - 2016-10-05 22:44 +1300
                Re: Is there any place to talk about language features? Malcolm McLean <malcolm.mclean5@btinternet.com> - 2016-10-05 03:12 -0700
                Re: Is there any place to talk about language features? Ian Collins <ian-news@hotmail.com> - 2016-10-06 15:38 +1300
                Re: Is there any place to talk about language features? Malcolm McLean <malcolm.mclean5@btinternet.com> - 2016-10-05 19:50 -0700
                Re: Is there any place to talk about language features? Ian Collins <ian-news@hotmail.com> - 2016-10-06 16:25 +1300
                Re: Is there any place to talk about language features? Malcolm McLean <malcolm.mclean5@btinternet.com> - 2016-10-05 21:19 -0700
                Re: Is there any place to talk about language features? Ian Collins <ian-news@hotmail.com> - 2016-10-06 18:11 +1300
                Re: Is there any place to talk about language features? Gareth Owen <gwowen@gmail.com> - 2016-10-06 06:38 +0100
                Re: Is there any place to talk about language features? Malcolm McLean <malcolm.mclean5@btinternet.com> - 2016-10-06 00:36 -0700
                Re: Is there any place to talk about language features? gwowen <gwowen@gmail.com> - 2016-10-06 07:33 -0700
                Re: Is there any place to talk about language features? supercat@casperkitty.com - 2016-10-06 09:00 -0700
                Re: Is there any place to talk about language features? Malcolm McLean <malcolm.mclean5@btinternet.com> - 2016-10-07 00:32 -0700
                Re: Is there any place to talk about language features? Thiago Adams <thiago.adams@gmail.com> - 2016-10-07 05:05 -0700
                Re: Is there any place to talk about language features? supercat@casperkitty.com - 2016-10-07 08:13 -0700
                Re: Is there any place to talk about language features? Malcolm McLean <malcolm.mclean5@btinternet.com> - 2016-10-07 00:20 -0700
                Re: Is there any place to talk about language features? Gareth Owen <gwowen@gmail.com> - 2016-10-07 17:01 +0100
                Re: Is there any place to talk about language features? Les Cargill <lcargill99@comcast.com> - 2016-10-05 12:45 -0500
                Re: Is there any place to talk about language features? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2016-10-05 11:12 +0100
                Re: Is there any place to talk about language features? Malcolm McLean <malcolm.mclean5@btinternet.com> - 2016-10-05 03:15 -0700
                Re: Is there any place to talk about language features? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2016-10-05 14:41 +0100
                Re: Is there any place to talk about language features? Malcolm McLean <malcolm.mclean5@btinternet.com> - 2016-10-05 08:01 -0700
                Re: Is there any place to talk about language features? supercat@casperkitty.com - 2016-10-05 08:41 -0700
                Re: Is there any place to talk about language features? Malcolm McLean <malcolm.mclean5@btinternet.com> - 2016-10-05 10:29 -0700
                Re: Is there any place to talk about language features? Thiago Adams <thiago.adams@gmail.com> - 2016-10-05 12:29 -0700
                Re: Is there any place to talk about language features? BartC <bc@freeuk.com> - 2016-10-05 11:08 +0100
                Re: Is there any place to talk about language features? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2016-10-05 14:35 +0100
                Re: Is there any place to talk about language features? BartC <bc@freeuk.com> - 2016-10-05 18:15 +0100
                Re: Is there any place to talk about language features? supercat@casperkitty.com - 2016-10-05 10:38 -0700
                Re: Is there any place to talk about language features? BartC <bc@freeuk.com> - 2016-10-05 19:14 +0100
                Re: Is there any place to talk about language features? supercat@casperkitty.com - 2016-10-05 11:56 -0700
                Re: Is there any place to talk about language features? Thiago Adams <thiago.adams@gmail.com> - 2016-10-05 11:57 -0700
                Re: Is there any place to talk about language features? Keith Thompson <kst-u@mib.org> - 2016-10-05 12:18 -0700
                Re: Is there any place to talk about language features? David Brown <david.brown@hesbynett.no> - 2016-10-05 21:49 +0200
                Re: Is there any place to talk about language features? Thiago Adams <thiago.adams@gmail.com> - 2016-10-05 13:07 -0700
                Re: Is there any place to talk about language features? "James R. Kuyper" <jameskuyper@verizon.net> - 2016-10-05 16:23 -0400
                Re: Is there any place to talk about language features? David Brown <david.brown@hesbynett.no> - 2016-10-06 14:26 +0200
                Re: Is there any place to talk about language features? supercat@casperkitty.com - 2016-10-05 13:56 -0700
                Re: Is there any place to talk about language features? BartC <bc@freeuk.com> - 2016-10-06 14:17 +0100
                Re: Is there any place to talk about language features? David Brown <david.brown@hesbynett.no> - 2016-10-06 15:53 +0200
                Re: Is there any place to talk about language features? Keith Thompson <kst-u@mib.org> - 2016-10-06 09:12 -0700
                Re: Is there any place to talk about language features? supercat@casperkitty.com - 2016-10-06 11:28 -0700
                Re: Is there any place to talk about language features? Ian Collins <ian-news@hotmail.com> - 2016-10-06 15:31 +1300
                Re: Is there any place to talk about language features? Ian Collins <ian-news@hotmail.com> - 2016-10-06 15:32 +1300
                Re: Is there any place to talk about language features? Malcolm McLean <malcolm.mclean5@btinternet.com> - 2016-10-05 19:43 -0700
                Re: Is there any place to talk about language features? Ian Collins <ian-news@hotmail.com> - 2016-10-06 16:05 +1300
                Re: Is there any place to talk about language features? Jorgen Grahn <grahn+nntp@snipabacken.se> - 2016-10-02 07:24 +0000
                Re: Is there any place to talk about language features? supercat@casperkitty.com - 2016-09-30 16:17 -0700
                Re: Is there any place to talk about language features? raltbos@xs4all.nl (Richard Bos) - 2016-10-01 09:39 +0000
                Re: Is there any place to talk about language features? supercat@casperkitty.com - 2016-10-01 14:11 -0700
            Re: Is there any place to talk about language features? Thiago Adams <thiago.adams@gmail.com> - 2016-09-29 07:47 -0700
            Re: Is there any place to talk about language features? Thiago Adams <thiago.adams@gmail.com> - 2016-09-29 10:25 -0700
  Re: Is there any place to talk about language features? "James R. Kuyper" <jameskuyper@verizon.net> - 2016-09-28 12:59 -0400
    Re: Is there any place to talk about language features? Richard Heathfield <rjh@cpax.org.uk> - 2016-09-28 18:30 +0100
      Re: Is there any place to talk about language features? Keith Thompson <kst-u@mib.org> - 2016-09-28 12:10 -0700
    Re: Is there any place to talk about language features? James Harris <james.harris.1@gmail.com> - 2016-09-28 20:20 +0100

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