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Re: MISRA C

From Tim Rentsch <tr.17687@z991.linuxsc.com>
Newsgroups comp.lang.c
Subject Re: MISRA C
Date 2026-10-06 22:14 -0700
Organization A noiseless patient Spider
Message-ID <86se2iks7g.fsf@linuxsc.com> (permalink)
References (14 earlier) <1196fb8$3rdj2$1@kst.eternal-september.org> <1196l3v$1b0$1@news.muc.de> <1196nn7$3upk9$1@kst.eternal-september.org> <1197piq$8k7p$1@dont-email.me> <87o6da9yyi.fsf@bsb.me.uk>

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Ben Bacarisse <ben@bsb.me.uk> writes:

> Sorry I'm jumping in here.  I don't read Usenet much these days but this
> got me going.
>
> David Brown <david.brown@hesbynett.no> writes:
>
>> You can implement the Ackermann function without explicit recursion, just
>> using a single loop and with allocated stacks or lists to hold the progress.
>> But you /cannot/ do so with a single allocation at the start.   If you are
>> asked to calculate A(m, n), you cannot calculate an upper bound on the stack
>> size you need without calculating the function.
>
> Hmm...  This is likely to confuse people.  You can calculate A(m, n)
> using O(m) extra space.  You can pre-allocate the space you need before
> starting the calculation.  (Aside: this disregards the space needed to
> store the numbers.  A(m, n) grows so large that you need extra space
> just to store the integers, but that complicates the discussion and I
> think everyone has been ignoring it in this thread anyway.)
>
> A carefully written recursive version will also use only O(m) stack, but
> here we get into problems of definition.  Given that there is an
> iterative version that needs only O(m) extra storage there is obviously
> a trivial recursive version of that function that, say, just pointlessly
> calls itself once!
>
>> But with malloc() and realloc(), you are good to go!
>
> In an imaginary C with unbounded integers, you can do it with a couple
> of VLAs at the top of the function.

After seeing Waldek's post I see now what you're getting at.
Thank you for jumping in.  There is always something new to
learn...

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Thread

MISRA C (was: buckle-up ....) Alan Mackenzie <acm@muc.de> - 2026-09-25 10:01 +0000
  Re: MISRA C Janis Papanagnou <janis_papanagnou+ng@hotmail.com> - 2026-09-25 14:52 +0200
    Re: MISRA C Alan Mackenzie <acm@muc.de> - 2026-09-25 13:48 +0000
      Re: MISRA C Janis Papanagnou <janis_papanagnou+ng@hotmail.com> - 2026-09-25 16:39 +0200
        Re: MISRA C Alan Mackenzie <acm@muc.de> - 2026-09-25 15:10 +0000
          Re: MISRA C bart <bc@freeuk.com> - 2026-09-25 16:57 +0100
          Re: MISRA C Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2026-09-25 11:42 -0700
            Re: MISRA C Alan Mackenzie <acm@muc.de> - 2026-09-25 20:21 +0000
              Re: MISRA C Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2026-09-25 14:05 -0700
                Re: MISRA C David Brown <david.brown@hesbynett.no> - 2026-09-26 08:43 +0200
                Re: MISRA C Alan Mackenzie <acm@muc.de> - 2026-09-26 17:55 +0000
                Re: MISRA C Ben Bacarisse <ben@bsb.me.uk> - 2026-10-03 23:55 +0100
                Re: MISRA C David Brown <david.brown@hesbynett.no> - 2026-10-04 16:10 +0200
                Re: MISRA C Ben Bacarisse <ben@bsb.me.uk> - 2026-10-05 01:22 +0100
                Re: MISRA C David Brown <david.brown@hesbynett.no> - 2026-10-05 07:59 +0200
                Re: MISRA C Tim Rentsch <tr.17687@z991.linuxsc.com> - 2026-10-05 01:23 -0700
                Re: MISRA C Tim Rentsch <tr.17687@z991.linuxsc.com> - 2026-10-05 01:24 -0700
                Re: MISRA C antispam@fricas.org (Waldek Hebisch) - 2026-10-05 09:02 +0000
                Re: MISRA C Janis Papanagnou <janis_papanagnou+ng@hotmail.com> - 2026-10-05 12:07 +0200
                Re: MISRA C Ben Bacarisse <ben@bsb.me.uk> - 2026-10-05 15:29 +0100
                Re: MISRA C antispam@fricas.org (Waldek Hebisch) - 2026-10-05 20:29 +0000
                Re: MISRA C Tim Rentsch <tr.17687@z991.linuxsc.com> - 2026-10-06 22:13 -0700
                Re: MISRA C Tim Rentsch <tr.17687@z991.linuxsc.com> - 2026-10-06 22:14 -0700
          Re: MISRA C Tim Rentsch <tr.17687@z991.linuxsc.com> - 2026-09-27 10:52 -0700
          Re: MISRA C Janis Papanagnou <janis_papanagnou+ng@hotmail.com> - 2026-09-28 13:08 +0200
            Re: MISRA C bart <bc@freeuk.com> - 2026-09-28 13:07 +0100
            Re: MISRA C David Brown <david.brown@hesbynett.no> - 2026-09-28 14:08 +0200
              Re: MISRA C Janis Papanagnou <janis_papanagnou+ng@hotmail.com> - 2026-09-28 14:28 +0200
            Re: MISRA C Alan Mackenzie <acm@muc.de> - 2026-09-28 12:17 +0000
              Re: MISRA C Janis Papanagnou <janis_papanagnou+ng@hotmail.com> - 2026-09-28 14:40 +0200
          Re: MISRA C "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2026-09-30 10:21 -0700
            Re: MISRA C Alan Mackenzie <acm@muc.de> - 2026-09-30 19:57 +0000
              Re: MISRA C "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2026-09-30 13:09 -0700
                Re: MISRA C David Brown <david.brown@hesbynett.no> - 2026-10-01 08:47 +0200
                Re: MISRA C "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2026-10-01 15:18 -0700
      Re: MISRA C Johann 'Myrkraverk' Oskarsson <johann@myrkraverk.invalid> - 2026-09-27 04:58 +0800
  Re: MISRA C David Brown <david.brown@hesbynett.no> - 2026-09-25 17:02 +0200
  Re: MISRA C "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2026-09-26 15:37 -0700

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