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Groups > comp.lang.c > #65374

Re: Unspecified behavior in C

From Keith Thompson <kst-u@mib.org>
Newsgroups comp.lang.c
Subject Re: Unspecified behavior in C
Date 2015-07-11 17:15 -0700
Organization None to speak of
Message-ID <lnsi8unscq.fsf@kst-u.example.com> (permalink)
References (6 earlier) <cb5f75e3-44fb-484d-a017-47e53b339c53@googlegroups.com> <lnzj358b78.fsf@kst-u.example.com> <30dbd9ab-036d-4b2a-bcea-7538f2dbe73d@googlegroups.com> <ln1tgfsu8i.fsf@kst-u.example.com> <37753968-e7fd-4076-9451-ed27b66a7330@googlegroups.com>

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David Kleinecke <dkleinecke@gmail.com> writes:
> On Friday, July 10, 2015 at 12:11:53 PM UTC-7, Keith Thompson wrote:
>> David Kleinecke <dkleinecke@gmail.com> writes:
>> > On Thursday, July 9, 2015 at 10:58:46 AM UTC-7, Keith Thompson wrote:
>> >> David Kleinecke <dkleinecke@gmail.com> writes:
>> [...]
>> >> > You are correct. I want all the "unspecified" behavior documented.
>> >> 
>> >> Thank you for the clear statement.
>> >> 
>> >> I strongly disagree.
>> 
>> [snip examples]
>> 
>> > I think you don't understand what I mean by documented. I just want
>> > what may happened stated. All I want for, say, the order of arguments
>> > is that there is a statement in the documentation like "the order
>> > in which the arguments of a function are evaluated is unpredicatable." 
>> > That is useful because an implementation might make them predicatable.
>> > At the moment the documentation is not required to say anything on this
>> > subject.
>> 
>> For the order to be truly *unpredictable*, it would have to use some
>> high-quality random number generator to determine the order on each
>> call.  Is that really what you meant?
>> 
>> In practice, the order is arbitrary, and may change depending on factors
>> that are not at all obvious.
>> 
>> I am perfectly satisfied with the standard's statement that the order is
>> unspecified (and I'm glossing over the possibility that evaluation could
>> be interleaved, since there are no sequence points between argument
>> evaluations).
>> 
>> If an implementation documented the order as "unpredictable", how would
>> you benefit from that information?
>> 
>> If gcc, for example, provided documentation that specified exactly how
>> the order is determined (for a given release, target platform, and
>> optimization level), how would you benefit from that information?
>> 
>> If the documentation merely stated that the order is unspecified, would
>> that satisfy you?  If so, what's the point?  That's exactly what the
>> standard already says.
>  
> You are assuming the standard is part of the documentation. I
> suppose that is fair enough but it wasn't my assumption. Perhaps
> I should add it. I would be much more willing to make that
> assumption if the standard were better written.

You've answered none of the questions I asked.  Did you intend to?

The standard documents the language.  The documentation for a
particular implementation is likely to be useless without that
knowledge.

The C standard says that the order of evaluation of function
arguments is unspecified.  It also explains clearly what
"unspecified" means.  Apparently that's not good enough for you,
but you haven't explained why.

-- 
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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Thread

Unspecified behavior in C David Kleinecke <dkleinecke@gmail.com> - 2015-07-07 14:44 -0700
  Re: Unspecified behavior in C Keith Thompson <kst-u@mib.org> - 2015-07-07 15:34 -0700
    Re: Unspecified behavior in C David Kleinecke <dkleinecke@gmail.com> - 2015-07-08 08:47 -0700
      Re: Unspecified behavior in C Keith Thompson <kst-u@mib.org> - 2015-07-08 09:11 -0700
        Re: Unspecified behavior in C David Kleinecke <dkleinecke@gmail.com> - 2015-07-08 10:24 -0700
          Re: Unspecified behavior in C John Bode <jfbode1029@gmail.com> - 2015-07-08 10:46 -0700
          Re: Unspecified behavior in C James Kuyper <jameskuyper@verizon.net> - 2015-07-08 13:54 -0400
          Re: Unspecified behavior in C Keith Thompson <kst-u@mib.org> - 2015-07-08 11:12 -0700
            Re: Unspecified behavior in C David Kleinecke <dkleinecke@gmail.com> - 2015-07-09 09:15 -0700
              Re: Unspecified behavior in C Richard Heathfield <rjh@cpax.org.uk> - 2015-07-09 17:33 +0100
                Re: Unspecified behavior in C David Kleinecke <dkleinecke@gmail.com> - 2015-07-10 09:24 -0700
                Re: Unspecified behavior in C James Kuyper <jameskuyper@verizon.net> - 2015-07-10 12:54 -0400
              Re: Unspecified behavior in C Keith Thompson <kst-u@mib.org> - 2015-07-09 10:58 -0700
                Re: Unspecified behavior in C David Kleinecke <dkleinecke@gmail.com> - 2015-07-10 09:33 -0700
                Re: Unspecified behavior in C Keith Thompson <kst-u@mib.org> - 2015-07-10 12:11 -0700
                Re: Unspecified behavior in C glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-07-10 21:05 +0000
                Re: Unspecified behavior in C Keith Thompson <kst-u@mib.org> - 2015-07-10 17:14 -0700
                Re: Unspecified behavior in C David Kleinecke <dkleinecke@gmail.com> - 2015-07-11 09:32 -0700
                Re: Unspecified behavior in C James Kuyper <jameskuyper@verizon.net> - 2015-07-11 12:59 -0400
                Re: Unspecified behavior in C Keith Thompson <kst-u@mib.org> - 2015-07-11 17:21 -0700
                Re: Unspecified behavior in C David Kleinecke <dkleinecke@gmail.com> - 2015-07-11 09:23 -0700
                Re: Unspecified behavior in C James Kuyper <jameskuyper@verizon.net> - 2015-07-11 13:03 -0400
                Re: Unspecified behavior in C Keith Thompson <kst-u@mib.org> - 2015-07-11 17:15 -0700
                Re: Unspecified behavior in C David Kleinecke <dkleinecke@gmail.com> - 2015-07-12 09:52 -0700
                Re: Unspecified behavior in C James Kuyper <jameskuyper@verizon.net> - 2015-07-12 14:13 -0400
                Re: Unspecified behavior in C David Kleinecke <dkleinecke@gmail.com> - 2015-07-13 09:02 -0700
                Re: Unspecified behavior in C James Kuyper <jameskuyper@verizon.net> - 2015-07-13 13:18 -0400
                Re: Unspecified behavior in C David Kleinecke <dkleinecke@gmail.com> - 2015-07-13 11:09 -0700
                Re: Unspecified behavior in C James Kuyper <jameskuyper@verizon.net> - 2015-07-13 15:06 -0400
                Re: Unspecified behavior in C David Kleinecke <dkleinecke@gmail.com> - 2015-07-14 08:14 -0700
                Re: Unspecified behavior in C James Kuyper <jameskuyper@verizon.net> - 2015-07-14 12:02 -0400
                Re: Unspecified behavior in C Keith Thompson <kst-u@mib.org> - 2015-07-13 12:03 -0700
                Re: Unspecified behavior in C David Kleinecke <dkleinecke@gmail.com> - 2015-07-14 07:54 -0700
                Re: Unspecified behavior in C James Kuyper <jameskuyper@verizon.net> - 2015-07-14 11:16 -0400
                Re: Unspecified behavior in C Richard Heathfield <rjh@cpax.org.uk> - 2015-07-14 16:17 +0100
                Re: Unspecified behavior in C David Kleinecke <dkleinecke@gmail.com> - 2015-07-14 09:16 -0700
                Re: Unspecified behavior in C James Kuyper <jameskuyper@verizon.net> - 2015-07-14 12:29 -0400
                Re: Unspecified behavior in C James Kuyper <jameskuyper@verizon.net> - 2015-07-14 14:57 -0400
                Re: Unspecified behavior in C Öö Tiib <ootiib@hot.ee> - 2015-07-14 13:12 -0700
                Re: Unspecified behavior in C James Kuyper <jameskuyper@verizon.net> - 2015-07-14 16:30 -0400
                Re: Unspecified behavior in C Öö Tiib <ootiib@hot.ee> - 2015-07-14 15:54 -0700
                Re: Unspecified behavior in C Morris Dovey <mrdovey@iedu.com> - 2015-07-14 21:41 -0500
                Re: Unspecified behavior in C Morris Dovey <mrdovey@iedu.com> - 2015-07-14 21:51 -0500
                Re: Unspecified behavior in C Öö Tiib <ootiib@hot.ee> - 2015-07-15 12:42 -0700
                Re: Unspecified behavior in C Morris Dovey <mrdovey@iedu.com> - 2015-07-15 16:13 -0500
                Re: Unspecified behavior in C Morris Dovey <mrdovey@iedu.com> - 2015-07-16 08:49 -0500
                Re: Unspecified behavior in C Tim Rentsch <txr@alumni.caltech.edu> - 2015-07-20 10:10 -0700
                Re: Unspecified behavior in C Morris Dovey <mrdovey@iedu.com> - 2015-07-20 13:24 -0500
                Re: Unspecified behavior in C Tim Rentsch <txr@alumni.caltech.edu> - 2015-07-23 02:56 -0700
                Re: Unspecified behavior in C Morris Dovey <mrdovey@iedu.com> - 2015-07-23 11:26 -0500
                Re: Unspecified behavior in C Tim Rentsch <txr@alumni.caltech.edu> - 2015-07-26 11:24 -0700
                Re: Unspecified behavior in C Morris Dovey <mrdovey@iedu.com> - 2015-07-23 19:03 -0500
                Re: Unspecified behavior in C David Kleinecke <dkleinecke@gmail.com> - 2015-07-15 21:19 -0700
                Re: Unspecified behavior in C Martin Shobe <martin.shobe@yahoo.com> - 2015-07-15 23:45 -0500
                Re: Unspecified behavior in C James Kuyper <jameskuyper@verizon.net> - 2015-07-16 01:37 -0400
                Re: Unspecified behavior in C Richard Heathfield <rjh@cpax.org.uk> - 2015-07-16 09:42 +0100
                Re: Unspecified behavior in C David Kleinecke <dkleinecke@gmail.com> - 2015-07-16 17:05 -0700
                Re: Unspecified behavior in C Richard Heathfield <rjh@cpax.org.uk> - 2015-07-17 01:32 +0100
                Re: Unspecified behavior in C James Kuyper <jameskuyper@verizon.net> - 2015-07-16 21:07 -0400
                We're good - don't you worry 'bout a thing, babe (Was: Unspecified behavior in C) gazelle@shell.xmission.com (Kenny McCormack) - 2015-07-17 07:21 +0000
                Re: Unspecified behavior in C raltbos@xs4all.nl (Richard Bos) - 2015-07-19 20:59 +0000
                Re: Unspecified behavior in C Richard Heathfield <rjh@cpax.org.uk> - 2015-07-19 22:02 +0100
                Re: Unspecified behavior in C James Kuyper <jameskuyper@verizon.net> - 2015-07-16 17:59 -0400
                Re: Unspecified behavior in C James Kuyper <jameskuyper@verizon.net> - 2015-07-16 23:09 -0400
                Re: Unspecified behavior in C David Kleinecke <dkleinecke@gmail.com> - 2015-07-17 18:48 -0700
                Re: Unspecified behavior in C James Kuyper <jameskuyper@verizon.net> - 2015-07-17 23:09 -0400
                Re: Unspecified behavior in C raltbos@xs4all.nl (Richard Bos) - 2015-07-19 20:57 +0000
                Re: Unspecified behavior in C James Kuyper <jameskuyper@verizon.net> - 2015-07-19 17:22 -0400
                Re: Unspecified behavior in C David Kleinecke <dkleinecke@gmail.com> - 2015-07-19 18:57 -0700
                Re: Unspecified behavior in C James Kuyper <jameskuyper@verizon.net> - 2015-07-19 22:16 -0400
                Re: Unspecified behavior in C David Kleinecke <dkleinecke@gmail.com> - 2015-07-19 19:30 -0700
                Re: Unspecified behavior in C John Bode <jfbode1029@gmail.com> - 2015-07-30 14:20 -0700
                Re: Unspecified behavior in C Keith Thompson <kst-u@mib.org> - 2015-07-30 15:30 -0700
                Re: Unspecified behavior in C John Bode <jfbode1029@gmail.com> - 2015-07-30 15:53 -0700
                Re: Unspecified behavior in C David Kleinecke <dkleinecke@gmail.com> - 2015-07-30 16:46 -0700
                Re: Unspecified behavior in C James Kuyper <jameskuyper@verizon.net> - 2015-07-31 00:59 -0400
                Re: Unspecified behavior in C David Kleinecke <dkleinecke@gmail.com> - 2015-07-31 17:15 -0700
                Re: Unspecified behavior in C Keith Thompson <kst-u@mib.org> - 2015-07-31 18:28 -0700
                Re: Unspecified behavior in C James Kuyper <jameskuyper@verizon.net> - 2015-07-31 23:28 -0400
                Re: Unspecified behavior in C Tim Rentsch <txr@alumni.caltech.edu> - 2015-08-04 04:07 -0700
                Re: Unspecified behavior in C David Kleinecke <dkleinecke@gmail.com> - 2015-08-04 18:02 -0700
                Re: Unspecified behavior in C James Kuyper <jameskuyper@verizon.net> - 2015-08-04 21:27 -0400
                Re: Unspecified behavior in C Tim Rentsch <txr@alumni.caltech.edu> - 2015-08-24 09:33 -0700
                Re: Unspecified behavior in C David Kleinecke <dkleinecke@gmail.com> - 2015-08-24 17:11 -0700
                Re: Unspecified behavior in C Tim Rentsch <txr@alumni.caltech.edu> - 2015-09-06 12:44 -0700
                Re: Unspecified behavior in C Ken Brody <kenbrody@spamcop.net> - 2015-08-03 12:09 -0400
                Re: Unspecified behavior in C James Kuyper <jameskuyper@verizon.net> - 2015-08-03 13:26 -0400
                Re: Unspecified behavior in C David Kleinecke <dkleinecke@gmail.com> - 2015-08-03 17:53 -0700
                Re: Unspecified behavior in C Keith Thompson <kst-u@mib.org> - 2015-08-03 18:44 -0700
                Re: Unspecified behavior in C David Kleinecke <dkleinecke@gmail.com> - 2015-08-04 17:59 -0700
                Re: Unspecified behavior in C Richard Heathfield <rjh@cpax.org.uk> - 2015-08-05 02:23 +0100
                Re: Unspecified behavior in C James Kuyper <jameskuyper@verizon.net> - 2015-08-04 21:39 -0400
                Re: Unspecified behavior in C Keith Thompson <kst-u@mib.org> - 2015-08-04 19:27 -0700
                Re: Unspecified behavior in C James Kuyper <jameskuyper@verizon.net> - 2015-08-04 00:25 -0400
                Re: Unspecified behavior in C Ken Brody <kenbrody@spamcop.net> - 2015-08-04 11:55 -0400
                Re: Unspecified behavior in C Philip Lantz <prl@canterey.us> - 2015-08-04 10:31 -0700
                Re: Unspecified behavior in C James Kuyper <jameskuyper@verizon.net> - 2015-08-04 13:32 -0400
                Re: Unspecified behavior in C James Kuyper <jameskuyper@verizon.net> - 2015-08-04 22:46 -0400
                Re: Unspecified behavior in C Ken Brody <kenbrody@spamcop.net> - 2015-08-10 12:16 -0400
                Re: Unspecified behavior in C James Kuyper <jameskuyper@verizon.net> - 2015-08-10 13:26 -0400
                Re: Unspecified behavior in C David Kleinecke <dkleinecke@gmail.com> - 2015-08-03 17:46 -0700
                Re: Unspecified behavior in C James Kuyper <jameskuyper@verizon.net> - 2015-08-05 12:34 -0400
                Re: Unspecified behavior in C Richard Heathfield <rjh@cpax.org.uk> - 2015-07-14 17:57 +0100
                Re: Unspecified behavior in C David Kleinecke <dkleinecke@gmail.com> - 2015-07-14 10:31 -0700
                Re: Unspecified behavior in C Richard Heathfield <rjh@cpax.org.uk> - 2015-07-14 18:50 +0100
                Re: Unspecified behavior in C David Kleinecke <dkleinecke@gmail.com> - 2015-07-15 20:59 -0700
                Re: Unspecified behavior in C Keith Thompson <kst-u@mib.org> - 2015-07-14 11:34 -0700
                Re: Unspecified behavior in C raltbos@xs4all.nl (Richard Bos) - 2015-07-19 20:46 +0000
                Re: Unspecified behavior in C Keith Thompson <kst-u@mib.org> - 2015-07-12 12:07 -0700
                Re: Unspecified behavior in C glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-07-12 19:53 +0000
                Re: Unspecified behavior in C James Kuyper <jameskuyper@verizon.net> - 2015-07-12 16:12 -0400
              Re: Unspecified behavior in C James Kuyper <jameskuyper@verizon.net> - 2015-07-09 14:20 -0400
                Re: Unspecified behavior in C Keith Thompson <kst-u@mib.org> - 2015-07-09 12:18 -0700
                Re: Unspecified behavior in C David Kleinecke <dkleinecke@gmail.com> - 2015-07-10 09:47 -0700
                Re: Unspecified behavior in C James Kuyper <jameskuyper@verizon.net> - 2015-07-10 13:36 -0400
                Re: Unspecified behavior in C David Kleinecke <dkleinecke@gmail.com> - 2015-07-11 09:19 -0700
                Re: Unspecified behavior in C James Kuyper <jameskuyper@verizon.net> - 2015-07-11 12:56 -0400
                Re: Unspecified behavior in C gordonb.j19di@burditt.org (Gordon Burditt) - 2015-07-11 20:36 -0500
                Re: Unspecified behavior in C David Kleinecke <dkleinecke@gmail.com> - 2015-07-12 10:10 -0700
              Re: Unspecified behavior in C Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-07-09 20:13 +0100
          Re: Unspecified behavior in C raltbos@xs4all.nl (Richard Bos) - 2015-07-09 11:17 +0000
        Re: Unspecified behavior in C David Kleinecke <dkleinecke@gmail.com> - 2015-07-08 10:37 -0700
          Re: Unspecified behavior in C John Bode <jfbode1029@gmail.com> - 2015-07-08 10:51 -0700
          Re: Unspecified behavior in C James Kuyper <jameskuyper@verizon.net> - 2015-07-08 14:14 -0400
          Re: Unspecified behavior in C Keith Thompson <kst-u@mib.org> - 2015-07-08 12:19 -0700
      Re: Unspecified behavior in C James Kuyper <jameskuyper@verizon.net> - 2015-07-08 12:14 -0400
        Re: Unspecified behavior in C David Kleinecke <dkleinecke@gmail.com> - 2015-07-08 10:40 -0700
          Re: Unspecified behavior in C James Kuyper <jameskuyper@verizon.net> - 2015-07-08 14:29 -0400
            Re: Unspecified behavior in C raltbos@xs4all.nl (Richard Bos) - 2015-07-09 11:20 +0000
      Re: Unspecified behavior in C Robert Wessel <robertwessel2@yahoo.com> - 2015-07-09 02:30 -0500
  Re: Unspecified behavior in C James Kuyper <jameskuyper@verizon.net> - 2015-07-07 22:30 -0400

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