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Groups > comp.lang.c > #101937

Re: Dinamic array without malloc - Can be done?

From David Brown <david.brown@hesbynett.no>
Newsgroups comp.lang.c
Subject Re: Dinamic array without malloc - Can be done?
Date 2017-01-16 10:08 +0100
Organization A noiseless patient Spider
Message-ID <o5i2g7$1la$1@dont-email.me> (permalink)
References <863e4550-027a-4d32-b5df-e34f2c7b4439@googlegroups.com> <o5gcm9$lu4$1@dont-email.me> <01610cdf-e6ca-47ac-ba40-b597b0c524d0@googlegroups.com> <n0kn7c1t8a7tbnjbt1ir4hikahmtakp7hp@4ax.com>

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On 15/01/17 20:53, Barry Schwarz wrote:
> On Sun, 15 Jan 2017 10:38:17 -0800 (PST), "Fernando D. Bozzo" 
> <fdbozzo@gmail.com> wrote:
> 
>> El domingo, 15 de enero de 2017, 18:50:39 (UTC+1), Richard
>> Heathfield  escribió: <snip>
>>> Why don't you want to use malloc?
>>> 
>> 
>> 
>> Hi Richard, the reason is just to simplify the garbage collection
>> automatically, and not needing to free() manually at some point. If
>> I could use some mechanism like try/catch then this could not be a
>> problem, but without it it makes more difficult to manage the flow
>> of a program.
>> 
>> May be is the little practice I have until now, but for small
>> arrays (<1MB) could be a good idea.
> 
> Why do you think the garbage collection performed when the VLA is 
> destroyed is any simpler then the garbage collection performed when 
> allocated memory is freed?  

Perhaps he thinks it is the case, because it is true?  It is easier for
the programmer - you just end the block, rather than having to free the
pointer.  It is more efficient at run-time in the code - allocation is
typically just adding/subtracting a size value to the stack pointer, and
deallocation is reversing that operation (if it is needed at all - often
that will be combined with the rest of the function epilogue).

> Are you aware that you cannot extend (or 
> shrink) a VLA while the size of an allocated array can be adjusted
> by realloc?

I am sure he is aware that a VLA is not the same thing as using malloc.

> 
> Since the "stack" is usually smaller than the "heap", using a VLA in
> a recursive function can lead to problems sooner than using malloc.
> 
> I am curious how the choice of allocation method can affect the flow 
> of your program.  Could you give an example.  I realize that one 
> approach calls malloc which is outside your code.  But I'm pretty 
> certain the code generated by the definition of the VLA will do a
> lot of processing unrelated to any executable statements you have
> coded. It may even call malloc for you.

It is highly unlikely that using a VLA will call malloc.  (It is not
impossible - someone mentioned that this is done on some 8051 compilers.
 But there we are talking about very limited processors with no decent
data stack support.)

> 
> The frequently cited quote about premature optimization springs 
> unbidden to mind.
> 

I wonder if you know what VLA's actually are.

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Dinamic array without malloc - Can be done? "Fernando D. Bozzo" <fdbozzo@gmail.com> - 2017-01-15 08:45 -0800
  Re: Dinamic array without malloc - Can be done? BartC <bc@freeuk.com> - 2017-01-15 16:53 +0000
    Re: Dinamic array without malloc - Can be done? fir <profesor.fir@gmail.com> - 2017-01-15 09:34 -0800
      Re: Dinamic array without malloc - Can be done? BartC <bc@freeuk.com> - 2017-01-17 21:09 +0000
        Re: Dinamic array without malloc - Can be done? fir <profesor.fir@gmail.com> - 2017-01-17 13:45 -0800
          Re: Dinamic array without malloc - Can be done? fir <profesor.fir@gmail.com> - 2017-01-17 14:09 -0800
          Re: Dinamic array without malloc - Can be done? BartC <bc@freeuk.com> - 2017-01-17 22:41 +0000
          Re: Dinamic array without malloc - Can be done? supercat@casperkitty.com - 2017-01-17 15:06 -0800
            Re: Dinamic array without malloc - Can be done? fir <profesor.fir@gmail.com> - 2017-01-17 16:49 -0800
            Re: Dinamic array without malloc - Can be done? Keith Thompson <kst-u@mib.org> - 2017-01-17 16:56 -0800
              Re: Dinamic array without malloc - Can be done? supercat@casperkitty.com - 2017-01-17 20:37 -0800
                Re: Dinamic array without malloc - Can be done? David Brown <david.brown@hesbynett.no> - 2017-01-18 09:38 +0100
                Re: Dinamic array without malloc - Can be done? Tim Rentsch <txr@alumni.caltech.edu> - 2017-01-31 08:49 -0800
                Re: Dinamic array without malloc - Can be done? supercat@casperkitty.com - 2017-01-31 10:39 -0800
                Re: Dinamic array without malloc - Can be done? luser droog <luser.droog@gmail.com> - 2017-01-31 10:55 -0800
                Re: Dinamic array without malloc - Can be done? supercat@casperkitty.com - 2017-01-31 11:40 -0800
                Re: Dinamic array without malloc - Can be done? "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2017-01-31 10:57 -0800
                Re: Dinamic array without malloc - Can be done? Tim Rentsch <txr@alumni.caltech.edu> - 2017-02-03 23:06 -0800
    Re: Dinamic array without malloc - Can be done? "Fernando D. Bozzo" <fdbozzo@gmail.com> - 2017-01-15 10:42 -0800
      Re: Dinamic array without malloc - Can be done? BartC <bc@freeuk.com> - 2017-01-15 20:15 +0000
        Re: Dinamic array without malloc - Can be done? Keith Thompson <kst-u@mib.org> - 2017-01-15 12:43 -0800
        Re: Dinamic array without malloc - Can be done? "Fernando D. Bozzo" <fdbozzo@gmail.com> - 2017-01-15 15:08 -0800
  Re: Dinamic array without malloc - Can be done? "James R. Kuyper" <jameskuyper@verizon.net> - 2017-01-15 12:25 -0500
    Re: Dinamic array without malloc - Can be done? "Fernando D. Bozzo" <fdbozzo@gmail.com> - 2017-01-15 10:46 -0800
      Re: Dinamic array without malloc - Can be done? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2017-01-15 20:13 +0000
        Re: Dinamic array without malloc - Can be done? "Fernando D. Bozzo" <fdbozzo@gmail.com> - 2017-01-15 15:06 -0800
    Re: Dinamic array without malloc - Can be done? Keith Thompson <kst-u@mib.org> - 2017-01-15 12:46 -0800
      Re: Dinamic array without malloc - Can be done? "James R. Kuyper" <jameskuyper@verizon.net> - 2017-01-15 16:10 -0500
      Re: Dinamic array without malloc - Can be done? Tim Rentsch <txr@alumni.caltech.edu> - 2017-01-15 20:37 -0800
        Re: Dinamic array without malloc - Can be done? Keith Thompson <kst-u@mib.org> - 2017-01-15 21:02 -0800
          Re: Dinamic array without malloc - Can be done? Tim Rentsch <txr@alumni.caltech.edu> - 2017-01-30 04:23 -0800
        Re: Dinamic array without malloc - Can be done? David Brown <david.brown@hesbynett.no> - 2017-01-16 09:05 +0100
          Re: Dinamic array without malloc - Can be done? Ian Collins <ian-news@hotmail.com> - 2017-01-16 21:16 +1300
            Re: Dinamic array without malloc - Can be done? David Brown <david.brown@hesbynett.no> - 2017-01-16 09:48 +0100
  Re: Dinamic array without malloc - Can be done? fir <profesor.fir@gmail.com> - 2017-01-15 09:29 -0800
    Re: Dinamic array without malloc - Can be done? fir <profesor.fir@gmail.com> - 2017-01-15 09:37 -0800
    Re: Dinamic array without malloc - Can be done? fir <profesor.fir@gmail.com> - 2017-01-15 09:56 -0800
      Re: Dinamic array without malloc - Can be done? fir <profesor.fir@gmail.com> - 2017-01-15 10:34 -0800
    Re: Dinamic array without malloc - Can be done? "Fernando D. Bozzo" <fdbozzo@gmail.com> - 2017-01-15 10:48 -0800
      Re: Dinamic array without malloc - Can be done? fir <profesor.fir@gmail.com> - 2017-01-15 11:10 -0800
      Re: Dinamic array without malloc - Can be done? Jean-Marc Bourguet <jm@bourguet.org> - 2017-01-15 20:22 +0100
        Re: Dinamic array without malloc - Can be done? Chad <cdalten@gmail.com> - 2017-01-15 11:50 -0800
        Re: Dinamic array without malloc - Can be done? "Fernando D. Bozzo" <fdbozzo@gmail.com> - 2017-01-15 15:12 -0800
  Re: Dinamic array without malloc - Can be done? Richard Heathfield <rjh@cpax.org.uk> - 2017-01-15 17:50 +0000
    Re: Dinamic array without malloc - Can be done? "Fernando D. Bozzo" <fdbozzo@gmail.com> - 2017-01-15 10:38 -0800
      Re: Dinamic array without malloc - Can be done? Richard Heathfield <rjh@cpax.org.uk> - 2017-01-15 19:34 +0000
        Re: Dinamic array without malloc - Can be done? Keith Thompson <kst-u@mib.org> - 2017-01-15 12:51 -0800
          Re: Dinamic array without malloc - Can be done? supercat@casperkitty.com - 2017-01-15 13:10 -0800
            Re: Dinamic array without malloc - Can be done? Keith Thompson <kst-u@mib.org> - 2017-01-15 16:23 -0800
              Re: Dinamic array without malloc - Can be done? supercat@casperkitty.com - 2017-01-15 18:08 -0800
            Re: Dinamic array without malloc - Can be done? David Brown <david.brown@hesbynett.no> - 2017-01-16 09:56 +0100
              Re: Dinamic array without malloc - Can be done? supercat@casperkitty.com - 2017-01-16 08:35 -0800
                Re: Dinamic array without malloc - Can be done? "Chris M. Thomasson" <invalid@invalid.invalid> - 2017-01-16 11:07 -0800
                Re: Dinamic array without malloc - Can be done? "Chris M. Thomasson" <invalid@invalid.invalid> - 2017-01-16 11:17 -0800
                Re: Dinamic array without malloc - Can be done? Robert Wessel <robertwessel2@yahoo.com> - 2017-01-16 15:21 -0600
                Re: Dinamic array without malloc - Can be done? "Chris M. Thomasson" <invalid@invalid.invalid> - 2017-01-31 22:22 -0800
                Re: Dinamic array without malloc - Can be done? David Brown <david.brown@hesbynett.no> - 2017-01-17 00:22 +0100
                Re: Dinamic array without malloc - Can be done? supercat@casperkitty.com - 2017-01-16 16:23 -0800
                Re: Dinamic array without malloc - Can be done? David Brown <david.brown@hesbynett.no> - 2017-01-17 02:04 +0100
                Re: Dinamic array without malloc - Can be done? supercat@casperkitty.com - 2017-01-16 17:27 -0800
                Re: Dinamic array without malloc - Can be done? David Brown <david.brown@hesbynett.no> - 2017-01-17 09:16 +0100
          Re: Dinamic array without malloc - Can be done? Tim Rentsch <txr@alumni.caltech.edu> - 2017-01-15 20:32 -0800
          Re: Dinamic array without malloc - Can be done? David Brown <david.brown@hesbynett.no> - 2017-01-16 10:02 +0100
            Re: Dinamic array without malloc - Can be done? Keith Thompson <kst-u@mib.org> - 2017-01-16 09:22 -0800
              Re: Dinamic array without malloc - Can be done? David Brown <david.brown@hesbynett.no> - 2017-01-17 00:25 +0100
      Re: Dinamic array without malloc - Can be done? Barry Schwarz <schwarzb@dqel.com> - 2017-01-15 11:53 -0800
        Re: Dinamic array without malloc - Can be done? fir <profesor.fir@gmail.com> - 2017-01-15 12:22 -0800
        Re: Dinamic array without malloc - Can be done? "Fernando D. Bozzo" <fdbozzo@gmail.com> - 2017-01-15 15:32 -0800
          Re: Dinamic array without malloc - Can be done? supercat@casperkitty.com - 2017-01-15 16:01 -0800
            Re: Dinamic array without malloc - Can be done? David Brown <david.brown@hesbynett.no> - 2017-01-16 10:19 +0100
              Re: Dinamic array without malloc - Can be done? BartC <bc@freeuk.com> - 2017-01-16 11:28 +0000
                Re: Dinamic array without malloc - Can be done? David Brown <david.brown@hesbynett.no> - 2017-01-16 14:29 +0100
                Re: Dinamic array without malloc - Can be done? BartC <bc@freeuk.com> - 2017-01-16 15:41 +0000
                Re: Dinamic array without malloc - Can be done? David Brown <david.brown@hesbynett.no> - 2017-01-16 17:27 +0100
                Re: Dinamic array without malloc - Can be done? supercat@casperkitty.com - 2017-01-16 07:56 -0800
                Re: Dinamic array without malloc - Can be done? David Brown <david.brown@hesbynett.no> - 2017-01-16 17:31 +0100
                Re: Dinamic array without malloc - Can be done? supercat@casperkitty.com - 2017-01-16 08:48 -0800
                Re: Dinamic array without malloc - Can be done? David Brown <david.brown@hesbynett.no> - 2017-01-17 00:29 +0100
                Re: Dinamic array without malloc - Can be done? "Chris M. Thomasson" <invalid@invalid.invalid> - 2017-01-16 11:25 -0800
                Re: Dinamic array without malloc - Can be done? supercat@casperkitty.com - 2017-01-16 12:28 -0800
                Re: Dinamic array without malloc - Can be done? "Chris M. Thomasson" <invalid@invalid.invalid> - 2017-01-16 12:38 -0800
          Re: Dinamic array without malloc - Can be done? Keith Thompson <kst-u@mib.org> - 2017-01-15 16:57 -0800
            Re: Dinamic array without malloc - Can be done? "Fernando D. Bozzo" <fdbozzo@gmail.com> - 2017-01-16 00:37 -0800
              Re: Dinamic array without malloc - Can be done? David Brown <david.brown@hesbynett.no> - 2017-01-16 10:23 +0100
                Re: Dinamic array without malloc - Can be done? "Fernando D. Bozzo" <fdbozzo@gmail.com> - 2017-01-16 01:35 -0800
                Re: Dinamic array without malloc - Can be done? Keith Thompson <kst-u@mib.org> - 2017-01-16 09:15 -0800
          Re: Dinamic array without malloc - Can be done? BartC <bc@freeuk.com> - 2017-01-16 01:29 +0000
        Re: Dinamic array without malloc - Can be done? David Brown <david.brown@hesbynett.no> - 2017-01-16 10:08 +0100
          Re: Dinamic array without malloc - Can be done? supercat@casperkitty.com - 2017-01-16 08:08 -0800
            Re: Dinamic array without malloc - Can be done? David Brown <david.brown@hesbynett.no> - 2017-01-17 00:35 +0100
              Re: Dinamic array without malloc - Can be done? supercat@casperkitty.com - 2017-01-16 16:31 -0800
                Re: Dinamic array without malloc - Can be done? David Brown <david.brown@hesbynett.no> - 2017-01-17 09:27 +0100
                Re: Dinamic array without malloc - Can be done? BartC <bc@freeuk.com> - 2017-01-17 12:11 +0000
                Re: Dinamic array without malloc - Can be done? David Brown <david.brown@hesbynett.no> - 2017-01-17 14:23 +0100
                Re: Dinamic array without malloc - Can be done? supercat@casperkitty.com - 2017-01-17 05:38 -0800
                Re: Dinamic array without malloc - Can be done? BartC <bc@freeuk.com> - 2017-01-17 14:17 +0000
                Re: Dinamic array without malloc - Can be done? supercat@casperkitty.com - 2017-01-17 07:09 -0800
                Re: Dinamic array without malloc - Can be done? supercat@casperkitty.com - 2017-01-17 05:14 -0800
                Re: Dinamic array without malloc - Can be done? David Brown <david.brown@hesbynett.no> - 2017-01-17 14:40 +0100
                Re: Dinamic array without malloc - Can be done? supercat@casperkitty.com - 2017-01-17 06:41 -0800
                Re: Dinamic array without malloc - Can be done? David Brown <david.brown@hesbynett.no> - 2017-01-17 16:00 +0100
                Re: Dinamic array without malloc - Can be done? supercat@casperkitty.com - 2017-01-17 07:45 -0800
                Re: Dinamic array without malloc - Can be done? fir <profesor.fir@gmail.com> - 2017-01-17 08:18 -0800
                Re: Dinamic array without malloc - Can be done? fir <profesor.fir@gmail.com> - 2017-01-17 08:27 -0800
                Re: Dinamic array without malloc - Can be done? supercat@casperkitty.com - 2017-01-17 09:29 -0800
                Re: Dinamic array without malloc - Can be done? supercat@casperkitty.com - 2017-01-17 09:23 -0800
                Re: Dinamic array without malloc - Can be done? fir <profesor.fir@gmail.com> - 2017-01-17 10:35 -0800
                Re: Dinamic array without malloc - Can be done? supercat@casperkitty.com - 2017-01-17 12:41 -0800
                Re: Dinamic array without malloc - Can be done? fir <profesor.fir@gmail.com> - 2017-01-17 13:45 -0800
                Re: Dinamic array without malloc - Can be done? Robert Wessel <robertwessel2@yahoo.com> - 2017-01-17 21:00 -0600
      Re: Dinamic array without malloc - Can be done? fir <profesor.fir@gmail.com> - 2017-01-15 11:55 -0800
      Re: Dinamic array without malloc - Can be done? Siri Cruise <chine.bleu@yahoo.com> - 2017-01-15 14:59 -0800
    Re: Dinamic array without malloc - Can be done? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2017-01-15 20:04 +0000
      Re: Dinamic array without malloc - Can be done? David Brown <david.brown@hesbynett.no> - 2017-01-15 21:33 +0100
        Re: Dinamic array without malloc - Can be done? supercat@casperkitty.com - 2017-01-15 13:00 -0800
          Re: Dinamic array without malloc - Can be done? Tim Rentsch <txr@alumni.caltech.edu> - 2017-01-15 20:27 -0800
        Re: Dinamic array without malloc - Can be done? "James R. Kuyper" <jameskuyper@verizon.net> - 2017-01-15 16:34 -0500
          Re: Dinamic array without malloc - Can be done? "James R. Kuyper" <jameskuyper@verizon.net> - 2017-01-15 16:43 -0500
            Re: Dinamic array without malloc - Can be done? Keith Thompson <kst-u@mib.org> - 2017-01-15 16:17 -0800
              Re: Dinamic array without malloc - Can be done? Tim Rentsch <txr@alumni.caltech.edu> - 2017-01-15 20:22 -0800
                Re: Dinamic array without malloc - Can be done? Keith Thompson <kst-u@mib.org> - 2017-01-15 21:00 -0800
                Re: Dinamic array without malloc - Can be done? Tim Rentsch <txr@alumni.caltech.edu> - 2017-01-30 05:01 -0800
                Re: Dinamic array without malloc - Can be done? Keith Thompson <kst-u@mib.org> - 2017-01-30 11:35 -0800
                Re: Dinamic array without malloc - Can be done? Tim Rentsch <txr@alumni.caltech.edu> - 2017-02-01 16:18 -0800
                Re: Dinamic array without malloc - Can be done? supercat@casperkitty.com - 2017-02-01 16:37 -0800
                Re: Dinamic array without malloc - Can be done? Robert Wessel <robertwessel2@yahoo.com> - 2017-02-01 23:21 -0600
                Re: Dinamic array without malloc - Can be done? Tim Rentsch <txr@alumni.caltech.edu> - 2017-02-02 00:27 -0800
                Re: Dinamic array without malloc - Can be done? supercat@casperkitty.com - 2017-02-02 10:58 -0800
                Re: Dinamic array without malloc - Can be done? Tim Rentsch <txr@alumni.caltech.edu> - 2017-02-03 22:51 -0800
  Re: Dinamic array without malloc - Can be done? "Chris M. Thomasson" <invalid@invalid.invalid> - 2017-01-15 15:41 -0800
    Re: Dinamic array without malloc - Can be done? "Fernando D. Bozzo" <fdbozzo@gmail.com> - 2017-01-15 15:44 -0800
      Re: Dinamic array without malloc - Can be done? "Chris M. Thomasson" <invalid@invalid.invalid> - 2017-01-15 16:17 -0800
  Re: Dinamic array without malloc - Can be done? Alla _ <modelling.data@gmail.com> - 2017-01-16 01:47 -0800
    Re: Dinamic array without malloc - Can be done? "Fernando D. Bozzo" <fdbozzo@gmail.com> - 2017-01-16 01:50 -0800
      Re: Dinamic array without malloc - Can be done? Alla _ <modelling.data@gmail.com> - 2017-01-16 02:38 -0800
        Re: Dinamic array without malloc - Can be done? "Fernando D. Bozzo" <fdbozzo@gmail.com> - 2017-01-16 03:15 -0800
          Re: Dinamic array without malloc - Can be done? Alla _ <modelling.data@gmail.com> - 2017-01-16 03:40 -0800
            Re: Dinamic array without malloc - Can be done? "Fernando D. Bozzo" <fdbozzo@gmail.com> - 2017-01-16 04:21 -0800
          Re: Dinamic array without malloc - Can be done? Alla _ <modelling.data@gmail.com> - 2017-01-16 04:29 -0800
            Re: Dinamic array without malloc - Can be done? "Fernando D. Bozzo" <fdbozzo@gmail.com> - 2017-01-16 04:36 -0800
    Re: Dinamic array without malloc - Can be done? Richard Heathfield <rjh@cpax.org.uk> - 2017-01-16 11:36 +0000
      Re: Dinamic array without malloc - Can be done? Alla _ <modelling.data@gmail.com> - 2017-01-16 03:44 -0800
      Re: Dinamic array without malloc - Can be done? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2017-01-16 15:34 +0000
        Re: Dinamic array without malloc - Can be done? Richard Heathfield <rjh@cpax.org.uk> - 2017-01-16 16:01 +0000
  Re: Dinamic array without malloc - Can be done? John Bode <jfbode1029@gmail.com> - 2017-01-17 10:14 -0800
    Re: Dinamic array without malloc - Can be done? James Kuyper <jameskuyper@verizon.net> - 2017-01-17 13:21 -0500
      Re: Dinamic array without malloc - Can be done? John Bode <jfbode1029@gmail.com> - 2017-01-17 11:43 -0800
        Re: Dinamic array without malloc - Can be done? James Kuyper <jameskuyper@verizon.net> - 2017-01-17 15:07 -0500
      Re: Dinamic array without malloc - Can be done? supercat@casperkitty.com - 2017-01-17 12:24 -0800
    Re: Dinamic array without malloc - Can be done? "Fernando D. Bozzo" <fdbozzo@gmail.com> - 2017-01-17 10:24 -0800
    Re: Dinamic array without malloc - Can be done? Tim Rentsch <txr@alumni.caltech.edu> - 2017-01-30 05:21 -0800

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