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Groups > comp.lang.c > #55075

Re: the language

From James Kuyper <jameskuyper@verizon.net>
Newsgroups comp.lang.c
Subject Re: the language
Date 2014-12-19 11:00 -0500
Organization Self
Message-ID <54944BB2.4080700@verizon.net> (permalink)
References (20 earlier) <ALQkw.114331$Cy6.90924@fx23.am4> <m716bq$i5$1@dont-email.me> <jeVkw.179964$or5.57791@fx11.am4> <54943C24.4040407@verizon.net> <OlXkw.483574$CW3.306863@fx07.am4>

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On 12/19/2014 10:19 AM, Richard Heathfield wrote:
> James Kuyper wrote:
> 
>> On 12/19/2014 07:54 AM, Richard Heathfield wrote:
> 
> <snip>
> 
>>> Since the Standard doesn't require any implementation to support this
>>> device, it will be necessary to implement it oneself on systems where the
>>> implementation doesn't support it. How, without UB?
>>
>> Again, I can't see the problem. If it's possible to connect your device
>> to a given platform, an implementor of C for that platform can provide
>> features with the implementation-defined behavior of causing
>> user-specified I/O to be performed through those connections.
> 
> Is it turtles all the way down?
> 
> By which I mean, how does the *implementor* write the code to interface with 
> that device, without UB?

The same way it writes code to implement addition of two int values
without undefined behavior. In either case, the implementation will be
in a platform-specific assembler or machine language, with behavior that
is well-defined by that language.

> And what if the implementor doesn't support that device (perhaps because 
> they've never heard of it)? How does one write the code oneself without UB?

They don't need to support the device; all they need to do is support
the connection to the device. Knowing how to access all of the available
connections provided by a given platform strikes me as a very ordinary
thing I'd expect any implementor targeting that platform to be able to
do. The user code needs to understand the device, but implementation's
code need merely provide the tools for communicating with the device. As
long as the use of the connection is well-defined, the fact that what
happens on the other end of connection is outside the scope of the
documentation is not sufficient to require the behavior to be described
as "undefined".

If you hadn't allowed for the possibility of implementation-defined
behavior, or if you'd inserted even a single word suggesting that the
solution needs to be portable, this would be a far more difficult
challenge. However, as it stands, it seems trivial to meet this challenge.

I can't provide example code, because it relies upon
implementation-defined support. If you would care to provide a list of C
features with implmentation-defined behavior, and to provide definitions
for that behavior which provide adequate input and output access to the
relevant connections on the relevant platform, and if you provide a
description of the hardware interface to your device, I could, in
principle, write appropriate user code to use those connections to
interface with that device.
In practice, I would expect creation of such a device driver to require
a major commitment of time, far too large for me to tackle without being
paid; and my lack of experience with this particular kind of programming
suggests you wouldn't be getting good value for your money if you did
pay me enough to justify spending my time to write it. But I don't see
how it is necessary for C to have undefined behavior in order to make it
work.

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the language Rosario193 <Rosario@invalid.invalid> - 2014-11-26 21:54 +0100
  Re: the language Rosario193 <Rosario@invalid.invalid> - 2014-11-26 21:56 +0100
    Re: the language John Bode <jfbode1029@gmail.com> - 2014-11-26 13:45 -0800
      Re: the language Rosario193 <Rosario@invalid.invalid> - 2014-11-28 11:52 +0100
      Re: the language "Bill Cunningham" <nospam@nspam.invalid> - 2014-12-01 23:25 -0500
      Re: the language "Bill Cunningham" <nospam@nspam.invalid> - 2014-12-02 00:56 -0500
        Re: the language Rosario193 <Rosario@invalid.invalid> - 2014-12-04 14:52 +0100
          Re: the language "Osmium" <r124c4u102@comcast.net> - 2014-12-04 08:07 -0600
            Re: the language Geoff <geoff@invalid.invalid> - 2014-12-04 10:20 -0800
  Re: the language Mark Storkamp <mstorkamp@yahoo.com> - 2014-11-26 15:11 -0600
    Re: the language Rosario193 <Rosario@invalid.invalid> - 2014-11-28 12:16 +0100
      Re: the language Rosario193 <Rosario@invalid.invalid> - 2014-11-28 12:18 +0100
  Re: the language John Bode <jfbode1029@gmail.com> - 2014-11-26 13:12 -0800
    Re: the language Kaz Kylheku <kaz@kylheku.com> - 2014-11-27 00:37 +0000
    Re: the language Ben Bacarisse <ben.usenet@bsb.me.uk> - 2014-11-27 01:13 +0000
  Re: the language raltbos@xs4all.nl (Richard Bos) - 2014-11-26 22:45 +0000
    Re: the language Rosario193 <Rosario@invalid.invalid> - 2014-11-27 07:41 +0100
  Re: the language Rosario193 <Rosario@invalid.invalid> - 2014-11-27 08:12 +0100
    Re: the language Morris Dovey <mrdovey@iedu.com> - 2014-11-27 01:43 -0600
      Re: the language Rosario193 <Rosario@invalid.invalid> - 2014-11-28 11:56 +0100
        Re: the language Morris Dovey <mrdovey@iedu.com> - 2014-11-28 09:08 -0600
          Re: the language Rosario193 <Rosario@invalid.invalid> - 2014-11-28 20:58 +0100
            Re: the language Morris Dovey <mrdovey@iedu.com> - 2014-11-28 19:22 -0600
              Re: the language Rosario193 <Rosario@invalid.invalid> - 2014-12-02 02:59 +0100
                Re: the language Kaz Kylheku <kaz@kylheku.com> - 2014-12-02 02:53 +0000
                Re: the language Les Cargill <lcargill99@comcast.com> - 2014-12-01 21:25 -0600
                Re: the language Kaz Kylheku <kaz@kylheku.com> - 2014-12-02 06:22 +0000
  Re: the language Richard Heathfield <invalid@see.sig.invalid> - 2014-11-27 08:37 +0000
    Re: the language Reinhardt Behm <rbehm@hushmail.com> - 2014-11-27 16:44 +0800
      Re: the language gazelle@shell.xmission.com (Kenny McCormack) - 2014-11-27 15:35 +0000
        Re: the language Richard Damon <Richard@Damon-Family.org> - 2014-11-27 11:58 -0500
          Re: the language jt@toerring.de (Jens Thoms Toerring) - 2014-11-27 22:44 +0000
            Re: the language Rosario193 <Rosario@invalid.invalid> - 2014-11-28 09:52 +0100
            Re: the language Tim Rentsch <txr@alumni.caltech.edu> - 2014-11-28 12:53 -0800
          Re: the language Thomas Jahns <jahns@idontlikespam.dkrz.de> - 2014-11-28 10:07 +0100
            Re: the language Thomas Jahns <jahns@idontlikespam.dkrz.de> - 2014-11-28 14:57 +0100
            Re: the language Tim Rentsch <txr@alumni.caltech.edu> - 2014-11-28 13:09 -0800
    Re: the language Rosario193 <Rosario@invalid.invalid> - 2014-11-28 12:01 +0100
      Re: the language Richard Heathfield <invalid@see.sig.invalid> - 2014-11-28 14:46 +0000
    Re: the language Tim Rentsch <txr@alumni.caltech.edu> - 2014-11-28 13:16 -0800
      Re: the language gazelle@shell.xmission.com (Kenny McCormack) - 2014-11-28 22:09 +0000
        Re: the language Tim Rentsch <txr@alumni.caltech.edu> - 2014-12-01 03:40 -0800
      Re: the language Malcolm McLean <malcolm.mclean5@btinternet.com> - 2014-11-28 14:42 -0800
        Re: the language Tim Rentsch <txr@alumni.caltech.edu> - 2014-12-01 03:22 -0800
      Re: the language Richard Heathfield <invalid@see.sig.invalid> - 2014-11-28 23:09 +0000
        Re: the language Malcolm McLean <malcolm.mclean5@btinternet.com> - 2014-11-28 16:14 -0800
          Re: the language BartC <bc@freeuk.com> - 2014-11-29 01:42 +0000
          Re: the language Kaz Kylheku <kaz@kylheku.com> - 2014-11-29 01:42 +0000
            Re: the language Malcolm McLean <malcolm.mclean5@btinternet.com> - 2014-11-29 04:03 -0800
          Re: the language Keith Thompson <kst-u@mib.org> - 2014-12-01 00:55 -0800
            Re: the language glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2014-12-02 05:42 +0000
        Re: the language Richard Damon <Richard@Damon-Family.org> - 2014-11-28 19:25 -0500
        Re: the language Tim Rentsch <txr@alumni.caltech.edu> - 2014-12-01 03:21 -0800
          Re: the language Richard Heathfield <invalid@see.sig.invalid> - 2014-12-01 14:02 +0000
            Re: the language Tim Rentsch <txr@alumni.caltech.edu> - 2014-12-05 10:18 -0800
              Re: the language Richard Heathfield <invalid@see.sig.invalid> - 2014-12-07 08:25 +0000
                Re: the language Öö Tiib <ootiib@hot.ee> - 2014-12-07 10:44 -0800
                Re: the language Richard Heathfield <invalid@see.sig.invalid> - 2014-12-07 19:17 +0000
                Re: the language Öö Tiib <ootiib@hot.ee> - 2014-12-07 15:48 -0800
                Re: the language Richard Heathfield <invalid@see.sig.invalid> - 2014-12-08 05:45 +0000
                Re: the language Malcolm McLean <malcolm.mclean5@btinternet.com> - 2014-12-08 03:27 -0800
                Re: the language Kaz Kylheku <kaz@kylheku.com> - 2014-12-08 06:00 +0000
                Re: the language Richard Heathfield <invalid@see.sig.invalid> - 2014-12-08 06:17 +0000
                Re: the language Malcolm McLean <malcolm.mclean5@btinternet.com> - 2014-12-08 03:37 -0800
                Re: the language Richard Heathfield <invalid@see.sig.invalid> - 2014-12-08 12:53 +0000
                Re: the language Tim Rentsch <txr@alumni.caltech.edu> - 2014-12-16 04:21 -0800
                Re: the language Richard Heathfield <invalid@see.sig.invalid> - 2014-12-16 12:43 +0000
                Re: the language Tim Rentsch <txr@alumni.caltech.edu> - 2014-12-16 14:46 -0800
                Re: the language Richard Heathfield <invalid@see.sig.invalid> - 2014-12-17 00:23 +0000
                Re: the language JohnF <john@please.see.sig.for.email.com> - 2014-12-17 07:01 +0000
                Re: the language Richard Heathfield <invalid@see.sig.invalid> - 2014-12-17 07:22 +0000
                Re: the language Ben Bacarisse <ben.usenet@bsb.me.uk> - 2014-12-17 11:56 +0000
                Re: the language Malcolm McLean <malcolm.mclean5@btinternet.com> - 2014-12-17 05:43 -0800
                Re: the language Rosario193 <Rosario@invalid.invalid> - 2014-12-18 18:30 +0100
                Re: the language Rosario193 <Rosario@invalid.invalid> - 2014-12-18 18:41 +0100
                Re: the language Richard Heathfield <invalid@see.sig.invalid> - 2014-12-17 14:34 +0000
                Re: the language Ben Bacarisse <ben.usenet@bsb.me.uk> - 2014-12-18 02:15 +0000
                Re: the language James Kuyper <jameskuyper@verizon.net> - 2014-12-17 22:31 -0500
                Re: the language Ben Bacarisse <ben.usenet@bsb.me.uk> - 2014-12-18 17:19 +0000
                Re: the language Richard Heathfield <invalid@see.sig.invalid> - 2014-12-18 07:52 +0000
                Re: the language Ben Bacarisse <ben.usenet@bsb.me.uk> - 2014-12-18 17:21 +0000
                Re: the language Richard Heathfield <invalid@see.sig.invalid> - 2014-12-18 18:15 +0000
                Re: the language Ben Bacarisse <ben.usenet@bsb.me.uk> - 2014-12-19 01:20 +0000
                Re: the language Richard Heathfield <invalid@see.sig.invalid> - 2014-12-19 07:48 +0000
                Re: the language James Kuyper <jameskuyper@verizon.net> - 2014-12-19 07:40 -0500
                Re: the language Richard Heathfield <invalid@see.sig.invalid> - 2014-12-19 12:54 +0000
                Re: the language James Kuyper <jameskuyper@verizon.net> - 2014-12-19 09:54 -0500
                Re: the language Richard Heathfield <invalid@see.sig.invalid> - 2014-12-19 15:19 +0000
                Re: the language James Kuyper <jameskuyper@verizon.net> - 2014-12-19 11:00 -0500
                Re: the language Richard Heathfield <invalid@see.sig.invalid> - 2014-12-19 16:13 +0000
                Re: the language James Kuyper <jameskuyper@verizon.net> - 2014-12-19 11:27 -0500
                Re: the language Richard Heathfield <invalid@see.sig.invalid> - 2014-12-19 16:45 +0000
                Re: the language James Kuyper <jameskuyper@verizon.net> - 2014-12-19 13:48 -0500
                Re: the language Richard Heathfield <invalid@see.sig.invalid> - 2014-12-19 19:10 +0000
                Re: the language Morris Dovey <mrdovey@iedu.com> - 2014-12-19 21:17 -0600
                Re: the language Morris Dovey <mrdovey@iedu.com> - 2014-12-19 21:32 -0600
                Re: the language Ben Bacarisse <ben.usenet@bsb.me.uk> - 2014-12-19 16:49 +0000
                Re: the language Richard Heathfield <invalid@see.sig.invalid> - 2014-12-19 17:00 +0000
                Re: the language James Kuyper <jameskuyper@verizon.net> - 2014-12-19 13:57 -0500
                Re: the language Malcolm McLean <malcolm.mclean5@btinternet.com> - 2014-12-19 14:31 -0800
                Re: the language Ben Bacarisse <ben.usenet@bsb.me.uk> - 2014-12-19 20:29 +0000
                Re: the language Richard Heathfield <invalid@see.sig.invalid> - 2014-12-19 20:36 +0000
                Re: the language Tim Rentsch <txr@alumni.caltech.edu> - 2014-12-17 07:18 -0800
                Re: the language Richard Heathfield <invalid@see.sig.invalid> - 2014-12-17 15:45 +0000
                Re: the language glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2014-12-17 16:50 +0000
                Re: the language raltbos@xs4all.nl (Richard Bos) - 2014-12-17 17:24 +0000
                Re: the language Robert Wessel <robertwessel2@yahoo.com> - 2014-12-18 02:07 -0600
                Re: the language raltbos@xs4all.nl (Richard Bos) - 2014-12-18 12:04 +0000
                Re: the language Richard Damon <Richard@Damon-Family.org> - 2014-12-18 08:06 -0500
                Re: the language James Kuyper <jameskuyper@verizon.net> - 2014-12-18 08:30 -0500
                Re: the language Richard Damon <Richard@Damon-Family.org> - 2014-12-19 00:11 -0500
                Re: the language glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2014-12-19 07:00 +0000
                Re: the language Keith Thompson <kst-u@mib.org> - 2014-12-19 08:43 -0800
                Re: the language Richard Damon <Richard@Damon-Family.org> - 2014-12-19 23:29 -0500
                Re: the language Keith Thompson <kst-u@mib.org> - 2014-12-20 00:37 -0800
                Re: the language gazelle@shell.xmission.com (Kenny McCormack) - 2014-12-20 08:45 +0000
                Re: the language raltbos@xs4all.nl (Richard Bos) - 2014-12-20 09:45 +0000
                Re: the language Malcolm McLean <malcolm.mclean5@btinternet.com> - 2014-12-20 03:17 -0800
                Re: the language Malcolm McLean <malcolm.mclean5@btinternet.com> - 2014-12-18 06:09 -0800
                Re: the language raltbos@xs4all.nl (Richard Bos) - 2014-12-18 14:30 +0000
                Re: the language raltbos@xs4all.nl (Richard Bos) - 2014-12-18 14:23 +0000
                Re: the language Keith Thompson <kst-u@mib.org> - 2014-12-18 08:18 -0800
                Re: the language Richard Damon <Richard@Damon-Family.org> - 2014-12-20 12:22 -0500
                Re: the language James Kuyper <jameskuyper@verizon.net> - 2014-12-20 13:36 -0500
                Re: the language Keith Thompson <kst-u@mib.org> - 2014-12-20 11:43 -0800
                Re: the language Keith Thompson <kst-u@mib.org> - 2014-12-20 11:37 -0800
                Re: the language glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2014-12-20 20:10 +0000
                Re: the language Robert Wessel <robertwessel2@yahoo.com> - 2014-12-21 15:02 -0600
                Re: the language Kaz Kylheku <kaz@kylheku.com> - 2014-12-21 22:02 +0000
                Re: the language Stephen Sprunk <stephen@sprunk.org> - 2014-12-21 23:49 -0600
                Re: the language raltbos@xs4all.nl (Richard Bos) - 2014-12-21 17:45 +0000
                Re: the language Tim Rentsch <txr@alumni.caltech.edu> - 2014-12-18 10:29 -0800
                Re: the language Robert Wessel <robertwessel2@yahoo.com> - 2014-12-20 05:29 -0600
                Re: the language Tim Rentsch <txr@alumni.caltech.edu> - 2014-12-20 11:32 -0800
                Re: the language Robert Wessel <robertwessel2@yahoo.com> - 2014-12-21 15:23 -0600
                Re: the language Tim Rentsch <txr@alumni.caltech.edu> - 2014-12-22 23:39 -0800
                Re: the language glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2014-12-20 20:22 +0000
                Re: the language Tim Rentsch <txr@alumni.caltech.edu> - 2014-12-18 10:24 -0800
                Re: the language Richard Heathfield <invalid@see.sig.invalid> - 2014-12-18 18:36 +0000
                Re: the language Tim Rentsch <txr@alumni.caltech.edu> - 2014-12-19 09:24 -0800
                Re: the language Richard Heathfield <invalid@see.sig.invalid> - 2014-12-19 17:53 +0000
                Re: the language Tim Rentsch <txr@alumni.caltech.edu> - 2014-12-20 11:48 -0800
                Re: the language JohnF <john@please.see.sig.for.email.com> - 2014-12-19 02:20 +0000
                Re: the language Richard Heathfield <invalid@see.sig.invalid> - 2014-12-19 08:31 +0000
                Re: the language JohnF <john@please.see.sig.for.email.com> - 2014-12-19 09:31 +0000
                Re: the language Richard Heathfield <invalid@see.sig.invalid> - 2014-12-19 10:10 +0000
                Re: the language Malcolm McLean <malcolm.mclean5@btinternet.com> - 2014-12-19 07:08 -0800
                Re: the language JohnF <john@please.see.sig.for.email.com> - 2014-12-20 06:39 +0000
                Re: the language John Forkosh <forkosh@panix.com> - 2014-12-20 07:32 +0000
                Re: the language Greg Martin <greg.at.softsprocket@dot.com> - 2015-01-04 17:02 +0000
                Re: the language James Kuyper <jameskuyper@verizon.net> - 2015-01-04 12:40 -0500
                Re: the language Greg Martin <greg.at.softsprocket@dot.com> - 2015-01-04 18:02 +0000
                Re: the language James Kuyper <jameskuyper@verizon.net> - 2015-01-05 09:47 -0500
                Re: the language Greg Martin <greg.at.softsprocket@dot.com> - 2015-01-05 15:14 +0000
                Re: the language Keith Thompson <kst-u@mib.org> - 2015-01-05 08:42 -0800
                Re: the language glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-01-06 00:14 +0000
                Re: the language James Kuyper <jameskuyper@verizon.net> - 2015-01-05 13:19 -0500
                Re: the language Richard Damon <Richard@Damon-Family.org> - 2015-01-04 15:59 -0500
                Re: the language Keith Thompson <kst-u@mib.org> - 2015-01-04 14:30 -0800
                Re: the language Malcolm McLean <malcolm.mclean5@btinternet.com> - 2015-01-04 15:44 -0800
                Re: the language James Kuyper <jameskuyper@verizon.net> - 2015-01-05 13:36 -0500
  Re: the language Rosario193 <Rosario@invalid.invalid> - 2014-11-28 12:07 +0100
  Re: the language "ocq (an evil corporate man)" <ocq@maili.ng> - 2014-12-02 23:16 +0100
    Re: the language Malcolm McLean <malcolm.mclean5@btinternet.com> - 2014-12-03 02:23 -0800
      Re: the language "ocq (an evil corporate man)" <ocq@maili.ng> - 2014-12-03 15:55 +0100
      Re: the language Nobody <nobody@nowhere.invalid> - 2014-12-03 15:42 +0000
        Re: the language Malcolm McLean <malcolm.mclean5@btinternet.com> - 2014-12-04 04:49 -0800
          Re: the language Keith Thompson <kst-u@mib.org> - 2014-12-04 09:07 -0800
            Re: the language Malcolm McLean <malcolm.mclean5@btinternet.com> - 2014-12-04 10:08 -0800
              Re: the language Keith Thompson <kst-u@mib.org> - 2014-12-04 11:49 -0800
                Re: the language Rosario193 <Rosario@invalid.invalid> - 2014-12-05 12:32 +0100
          Re: the language raltbos@xs4all.nl (Richard Bos) - 2014-12-04 22:17 +0000
  Re: the language Rosario193 <Rosario@invalid.invalid> - 2014-12-18 18:17 +0100
    Re: the language Richard Heathfield <invalid@see.sig.invalid> - 2014-12-18 18:12 +0000
      Re: the language Rosario193 <Rosario@invalid.invalid> - 2014-12-18 23:15 +0100
        Re: the language Rosario193 <Rosario@invalid.invalid> - 2014-12-18 23:50 +0100
    Re: the language "ocq (an evil corporate man)" <ocq@maili.ng> - 2014-12-19 02:34 +0100

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