Re: Future of C

From	Keith Thompson <kst-u@mib.org>
Newsgroups	comp.lang.c
Subject	Re: Future of C
Date	2018-03-30 09:45 -0700
Organization	None to speak of
Message-ID	<lnin9dtsuo.fsf@kst-u.example.com> (permalink)
References	(16 earlier) <0dcf08ee-d589-444c-8122-5310d95e80df@googlegroups.com> <p88srs$17c$1@dont-email.me> <kfna7uunp2c.fsf@x-alumni2.alumni.caltech.edu> <ln7epxwm5h.fsf@kst-u.example.com> <kfnh8oxlkfn.fsf@x-alumni2.alumni.caltech.edu>

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Tim Rentsch <txr@alumni.caltech.edu> writes:
> Keith Thompson <kst-u@mib.org> writes:
>> Tim Rentsch <txr@alumni.caltech.edu> writes:
>>> David Brown <david.brown@hesbynett.no> writes:
>>>> Overruning the stack is undefined behaviour - [...]
>>>
>>> Considered in the sense the ISO C standard defines and uses the
>>> term, overrunning a run-time stack is not undefined behavior.
>>
>> Would you care to elaborate on that?  How is it not "behavior that
>> is not defined" (N1570 4p2)?

Correction: the phrase in 4p2 is "behavior that is undefined".

> Simple:
>
>   1. Write a program that runs out of stack but is otherwise
>      strictly conforming.  (It's easy to do this.)
>
>   2. Identify the statement or declaration whose behavior
>      is undefined under the semantic descriptions given
>      in the Standard.  (That assertion should be supported
>      by specific references to relevant passages in the
>      Standard.)
>
>   3. If you can't identify any such statement or declaration,
>      the program has no undefined behavior as the Standard
>      uses the term, and running out of stack space doesn't
>      change that.
>
> Any claim that running out of stack space is undefined behavior
> should be able to be supported by showing such a program and
> pointing out the particular statement or declaration described in
> step (2);  if there is no such statement or declaration, there is
> no undefined behavior.  In the absence of any such identification,
> we may reasonably conclude that running out of stack space does
> not imply undefined behavior, in the sense the Standard uses the
> term.

If the behavior of a stack overflow is not "behavior that is
undefined", then how is it defined?  Or is there some third
alternative other than "behavior that is undefined" and "behavior
that is defined"?

Undefined behavior may be indicated "by the omission of any explicit
definition of behavior".

The standard acknowledges but does not specify capacity limits
in 1p2, saying that the standard does not specify "the size
or complexity of a program and its data that will exceed the
capacity of any specific data-processing system or the capacity of
a particular processor".  The standard omits any explicit definition
of the behavior of a program that has exceeded a capacity limit.

-- 
Keith Thompson (The_Other_Keith) kst-u@mib.org  <http://www.ghoti.net/~kst>
Working, but not speaking, for JetHead Development, Inc.
"We must do something.  This is something.  Therefore, we must do this."
    -- Antony Jay and Jonathan Lynn, "Yes Minister"

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Re: Future of C Tim Rentsch <txr@alumni.caltech.edu> - 2018-03-26 21:02 -0700
  Re: Future of C David Brown <david.brown@hesbynett.no> - 2018-03-27 09:39 +0200
    Re: Future of C supercat@casperkitty.com - 2018-03-27 07:37 -0700
      Re: Future of C Steven Petruzzellis <frelwizzen@gmail.com> - 2018-03-28 11:19 -0700
  Re: Future of C Steven Petruzzellis <frelwizzen@gmail.com> - 2018-03-27 00:42 -0700
  Re: Future of C Keith Thompson <kst-u@mib.org> - 2018-03-27 08:52 -0700
    Re: Future of C Tim Rentsch <txr@alumni.caltech.edu> - 2018-03-30 07:14 -0700
      Re: Future of C David Brown <david.brown@hesbynett.no> - 2018-03-30 17:23 +0200
        Re: Future of C Steven Petruzzellis <frelwizzen@gmail.com> - 2018-03-31 02:41 -0700
      Re: Future of C Keith Thompson <kst-u@mib.org> - 2018-03-30 09:45 -0700
        Re: Future of C Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2018-04-02 01:42 -0700
          Re: Future of C Steven Petruzzellis <frelwizzen@gmail.com> - 2018-04-02 04:53 -0700
          Re: Future of C supercat@casperkitty.com - 2018-04-02 06:02 -0700
            Re: Future of C Steven Petruzzellis <frelwizzen@gmail.com> - 2018-04-02 06:57 -0700
            Re: Future of C Keith Thompson <kst-u@mib.org> - 2018-04-02 09:12 -0700
              Re: Future of C "Chris M. Thomasson" <invalid_chris_thomasson@invalid.invalid> - 2018-04-02 13:30 -0700
                Re: Future of C Steven Petruzzellis <frelwizzen@gmail.com> - 2018-04-03 00:59 -0700
              Re: Future of C David Brown <david.brown@hesbynett.no> - 2018-04-02 22:33 +0200
                Re: Future of C Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2018-04-03 01:40 -0700
                Re: Future of C David Brown <david.brown@hesbynett.no> - 2018-04-03 12:47 +0200
              Re: Future of C supercat@casperkitty.com - 2018-04-03 09:51 -0700
                Re: Future of C Keith Thompson <kst-u@mib.org> - 2018-04-03 11:23 -0700
                Re: Future of C supercat@casperkitty.com - 2018-04-03 11:37 -0700
                Re: Future of C Keith Thompson <kst-u@mib.org> - 2018-04-03 11:46 -0700
                Re: Future of C supercat@casperkitty.com - 2018-04-03 12:26 -0700
                Re: Future of C Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2018-04-04 01:17 -0700
                Re: Future of C supercat@casperkitty.com - 2018-04-04 09:45 -0700
          Re: Future of C Keith Thompson <kst-u@mib.org> - 2018-04-02 09:10 -0700
            Re: Future of C Steven Petruzzellis <frelwizzen@gmail.com> - 2018-04-02 09:33 -0700
            Re: Future of C Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2018-04-03 01:35 -0700
              Re: Future of C David Brown <david.brown@hesbynett.no> - 2018-04-03 12:50 +0200
                Re: Future of C Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2018-04-03 04:01 -0700
              Re: Future of C Keith Thompson <kst-u@mib.org> - 2018-04-03 09:12 -0700
        Re: Future of C Tim Rentsch <txr@alumni.caltech.edu> - 2018-04-04 16:17 -0700
          Re: Future of C Keith Thompson <kst-u@mib.org> - 2018-04-04 17:26 -0700
            Re: Future of C Tim Rentsch <txr@alumni.caltech.edu> - 2018-04-09 07:30 -0700
              Re: Future of C Keith Thompson <kst-u@mib.org> - 2018-04-09 08:52 -0700
                Re: Future of C Tim Rentsch <txr@alumni.caltech.edu> - 2018-04-11 08:21 -0700
                Re: Future of C Keith Thompson <kst-u@mib.org> - 2018-04-11 09:28 -0700
          Re: Future of C supercat@casperkitty.com - 2018-04-05 11:00 -0700

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