Re: Variable-length arrays: should they be used at all?

From	jacob navia <jacob@spamsink.net>
Newsgroups	comp.lang.c
Subject	Re: Variable-length arrays: should they be used at all?
Date	2012-06-27 20:48 +0200
Organization	lccwin
Message-ID	<jsfkid$2b0$1@speranza.aioe.org> (permalink)
References	<jscgum$lk6$1@speranza.aioe.org> <jsd15l$28f$1@speranza.aioe.org> <ListBuffer-20120626211823@ram.dialup.fu-berlin.de> <jse4k1$9of$1@speranza.aioe.org> <private_implementation-20120627182821@ram.dialup.fu-berlin.de>

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Le 27/06/12 18:36, Stefan Ram a écrit :
>
>    Ok, I see. LIST_SIZE must be either »sizeof List« or a
>    programmer-written literal, such as »104«, which is
>    error-prone.
>
>    (One could generate a header file »#define LIST_SIZE 104«
>    during the make process using means beyond the C language
>    only.)
>
>    However, in your code, you have:
>
> List *L = (List *)&buffer[0];
>
>    . Doesn't this also mean that »List« must be disclosed to
>    the client, which, as I understand it, is the actual list
>    header structure?
>

No, the actual "List" structure mustn't be disclosed at all since you
always work with POINTERS to that incomplete type and never with
the type itself.

This is the beauty of C "private" types: they are REALLY private
and you have absolutely NO CLUE at all what they actually are.

Interface and implementation are then completely separated. I can
(and have) changed the list structure several times without ever
needing to change client code.

More: Old code that was compiled long ago when the list structure
was different will STILL WORK.

Thread

Variable-length arrays: should they be used at all? Rui Maciel <rui.maciel@gmail.com> - 2012-06-26 15:28 +0100
  Re: Variable-length arrays: should they be used at all? Eric Sosman <esosman@ieee-dot-org.invalid> - 2012-06-26 11:54 -0400
  Re: Variable-length arrays: should they be used at all? jacob navia <jacob@spamsink.net> - 2012-06-26 21:05 +0200
    Re: Variable-length arrays: should they be used at all? Rui Maciel <rui.maciel@gmail.com> - 2012-06-26 21:04 +0100
      Re: Variable-length arrays: should they be used at all? Keith Thompson <kst-u@mib.org> - 2012-06-26 13:09 -0700
        Re: Variable-length arrays: should they be used at all? Ian Collins <ian-news@hotmail.com> - 2012-06-27 17:50 +1200
          Re: Variable-length arrays: should they be used at all? jacob navia <jacob@spamsink.net> - 2012-06-27 07:57 +0200
            Re: Variable-length arrays: should they be used at all? gwowen <gwowen@gmail.com> - 2012-06-27 00:49 -0700
            Re: Variable-length arrays: should they be used at all? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2012-06-27 13:50 +0100
              Re: Variable-length arrays: should they be used at all? Eric Sosman <esosman@ieee-dot-org.invalid> - 2012-06-27 10:21 -0400
                Re: Variable-length arrays: should they be used at all? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2012-06-27 19:56 +0100
          Re: Variable-length arrays: should they be used at all? Phil Carmody <thefatphil_demunged@yahoo.co.uk> - 2012-07-06 00:55 +0300
            Re: Variable-length arrays: should they be used at all? Andrew Cooper <amc96@cam.ac.uk> - 2012-07-05 23:37 +0100
              Re: Variable-length arrays: should they be used at all? Tim Rentsch <txr@alumni.caltech.edu> - 2012-07-06 16:53 -0700
            Re: Variable-length arrays: should they be used at all? Ian Collins <ian-news@hotmail.com> - 2012-07-06 18:26 +1200
              Re: Variable-length arrays: should they be used at all? Phil Carmody <thefatphil_demunged@yahoo.co.uk> - 2012-07-07 17:37 +0300
                Re: Variable-length arrays: should they be used at all? Ian Collins <ian-news@hotmail.com> - 2012-07-08 08:03 +1200
            Re: Variable-length arrays: should they be used at all? gwowen <gwowen@gmail.com> - 2012-07-06 02:58 -0700
              Re: Variable-length arrays: should they be used at all? Tim Rentsch <txr@alumni.caltech.edu> - 2012-07-06 18:11 -0700
                Re: Variable-length arrays: should they be used at all? gwowen <gwowen@gmail.com> - 2012-07-09 02:33 -0700
                Re: Variable-length arrays: should they be used at all? Tim Rentsch <txr@alumni.caltech.edu> - 2012-07-09 11:35 -0700
                Re: Variable-length arrays: should they be used at all? Ike Naar <ike@iceland.freeshell.org> - 2012-07-09 22:33 +0000
                Re: Variable-length arrays: should they be used at all? Tim Rentsch <txr@alumni.caltech.edu> - 2012-07-10 10:52 -0700
                Re: Variable-length arrays: should they be used at all? Malcolm McLean <malcolm.mclean5@btinternet.com> - 2012-07-09 12:03 -0700
                Re: Variable-length arrays: should they be used at all? Ian Collins <ian-news@hotmail.com> - 2012-07-10 09:19 +1200
        Re: Variable-length arrays: should they be used at all? Gareth Owen <gwowen@gmail.com> - 2012-06-27 07:25 +0100
    Re: Variable-length arrays: should they be used at all? jacob navia <jacob@spamsink.net> - 2012-06-27 07:10 +0200
      Re: Variable-length arrays: should they be used at all? jacob navia <jacob@spamsink.net> - 2012-06-27 20:48 +0200
  Re: Variable-length arrays: should they be used at all? Jens Gustedt <jens.gustedt@loria.fr> - 2012-06-26 21:13 +0200
    Re: Variable-length arrays: should they be used at all? Rui Maciel <rui.maciel@gmail.com> - 2012-06-26 20:47 +0100
      Re: Variable-length arrays: should they be used at all? Keith Thompson <kst-u@mib.org> - 2012-06-26 13:05 -0700
      Re: Variable-length arrays: should they be used at all? David Resnick <lndresnick@gmail.com> - 2012-06-26 13:51 -0700
        Re: Variable-length arrays: should they be used at all? Malcolm McLean <malcolm.mclean5@btinternet.com> - 2012-06-26 17:10 -0700
        Re: Variable-length arrays: should they be used at all? Gareth Owen <gwowen@gmail.com> - 2012-06-27 07:27 +0100
        Re: Variable-length arrays: should they be used at all? Rui Maciel <rui.maciel@gmail.com> - 2012-06-27 20:23 +0100
  Re: Variable-length arrays: should they be used at all? Tim Rentsch <txr@alumni.caltech.edu> - 2012-06-27 11:20 -0700
    Re: Variable-length arrays: should they be used at all? Ian Collins <ian-news@hotmail.com> - 2012-06-28 09:35 +1200
      Re: Variable-length arrays: should they be used at all? Tim Rentsch <txr@alumni.caltech.edu> - 2012-06-27 17:23 -0700
        Re: Variable-length arrays: should they be used at all? Ian Collins <ian-news@hotmail.com> - 2012-06-28 13:06 +1200
          Re: Variable-length arrays: should they be used at all? Tim Rentsch <txr@alumni.caltech.edu> - 2012-06-29 10:48 -0700
            Re: Variable-length arrays: should they be used at all? Ian Collins <ian-news@hotmail.com> - 2012-06-30 21:58 +1200
              Re: Variable-length arrays: should they be used at all? Malcolm McLean <malcolm.mclean5@btinternet.com> - 2012-06-30 03:37 -0700
              Re: Variable-length arrays: should they be used at all? Tim Rentsch <txr@alumni.caltech.edu> - 2012-07-01 19:31 -0700
            Re: Variable-length arrays: should they be used at all? Phil Carmody <thefatphil_demunged@yahoo.co.uk> - 2012-07-06 00:54 +0300
              Re: Variable-length arrays: should they be used at all? Tim Rentsch <txr@alumni.caltech.edu> - 2012-07-06 17:58 -0700
        Re: Variable-length arrays: should they be used at all? Phil Carmody <thefatphil_demunged@yahoo.co.uk> - 2012-07-06 00:49 +0300
          Re: Variable-length arrays: should they be used at all? Tim Rentsch <txr@alumni.caltech.edu> - 2012-07-06 16:38 -0700
            Re: Variable-length arrays: should they be used at all? Phil Carmody <thefatphil_demunged@yahoo.co.uk> - 2012-07-07 18:00 +0300
              Re: Variable-length arrays: should they be used at all? Tim Rentsch <txr@alumni.caltech.edu> - 2012-07-07 12:40 -0700
                Re: Variable-length arrays: should they be used at all? pacman@kosh.dhis.org (Alan Curry) - 2012-07-08 02:54 +0000
                Re: Variable-length arrays: should they be used at all? jacob navia <jacob@spamsink.net> - 2012-07-08 13:33 +0200
                Re: Variable-length arrays: should they be used at all? pacman@kosh.dhis.org (Alan Curry) - 2012-07-08 22:18 +0000
                Re: Variable-length arrays: should they be used at all? Tim Rentsch <txr@alumni.caltech.edu> - 2012-07-09 10:57 -0700
                Re: Variable-length arrays: should they be used at all? pacman@kosh.dhis.org (Alan Curry) - 2012-07-09 21:38 +0000
                Re: Variable-length arrays: should they be used at all? Tim Rentsch <txr@alumni.caltech.edu> - 2012-07-10 11:12 -0700
                Re: Variable-length arrays: should they be used at all? Tim Rentsch <txr@alumni.caltech.edu> - 2012-07-08 11:28 -0700

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