Re: NULL as the empty string

From	Keith Thompson <kst-u@mib.org>
Newsgroups	comp.lang.c
Subject	Re: NULL as the empty string
Date	2017-12-08 15:19 -0800
Organization	None to speak of
Message-ID	<lnvahgst7s.fsf@kst-u.example.com> (permalink)
References	(2 earlier) <0f96b837-7b9a-435f-81ec-8bbc8d2f928b@googlegroups.com> <ln7etxt4ox.fsf@kst-u.example.com> <p0etae$tqd$1@dont-email.me> <lnzi6trkxz.fsf@kst-u.example.com> <p0f1eb$sg1$1@dont-email.me>

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jacobnavia <jacob@jacob.remcomp.fr> writes:
> Le 08/12/2017 à 22:03, Keith Thompson a écrit :
>> You propose that strlen(NULL) should return 0 (rather than having
>> undefined behavior as it currently does).  Does your proposal apply
>> only to code that uses the NULL macro, or would strlen() return
>> 0 for any null pointer argument?  Would strlen(0), which passes a
>> null pointer value to strlen*without*  referring to the NULL macro,
>> be required to return 0 under your proposal?
>
> Trying to make a distinction between using a macro and not would break 
> the whole preprocessor.
>
> Obviously this must be checked at run time. I do not see any use of calling
>
> strlen(NULL);
>
> in the code.

I'm fairly sure that answers my question, thanks.  You're talking
about null pointer values, not about the NULL macro.

I suggest using the phrase "null pointer" rather than "NULL".
Using the latter could imply (as John Bode thought) that you're
talking specifically about the macro rather than about the value
that it represents.

> That could be simplified to zero by the compiler as an optimization.
>
> I am proposing
>
> The undefined behavior of calling strlen with a NULL pointer value is 
> defined as zero. NULL is the empty string.
[...]

What you propose is treating a null pointer as *a pointer to* the
empty string, not as the empty string itself.  (Unless you're also
proposing to change the standard's definition of the word "string".)

Since the cases we're talking about have undefined behavior, a
conforming implementation can behave as you propose.  Does lcc-win
do this?  If not, are you planning to change it so it does?

-- 
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"

Thread

NULL as the empty string jacobnavia <jacob@jacob.remcomp.fr> - 2017-11-21 23:52 +0100
  Re: NULL as the empty string Keith Thompson <kst-u@mib.org> - 2017-11-21 15:16 -0800
    Re: NULL as the empty string jacobnavia <jacob@jacob.remcomp.fr> - 2017-11-22 00:38 +0100
      Re: NULL as the empty string Keith Thompson <kst-u@mib.org> - 2017-11-21 16:02 -0800
        Re: NULL as the empty string jacobnavia <jacob@jacob.remcomp.fr> - 2017-11-22 01:13 +0100
          Re: NULL as the empty string Keith Thompson <kst-u@mib.org> - 2017-11-21 16:52 -0800
      Re: NULL as the empty string Robert Wessel <robertwessel2@yahoo.com> - 2017-11-21 18:09 -0600
      Re: NULL as the empty string Siri Cruise <chine.bleu@yahoo.com> - 2017-11-21 16:34 -0800
      Re: NULL as the empty string David Brown <david.brown@hesbynett.no> - 2017-11-22 12:12 +0100
    Re: NULL as the empty string supercat@casperkitty.com - 2017-11-21 15:57 -0800
      Re: NULL as the empty string jacobnavia <jacob@jacob.remcomp.fr> - 2017-11-22 01:06 +0100
        Re: NULL as the empty string supercat@casperkitty.com - 2017-11-22 15:42 -0800
          Re: NULL as the empty string Melzzzzz <Melzzzzz@zzzzz.com> - 2017-11-22 23:49 +0000
            Re: NULL as the empty string supercat@casperkitty.com - 2017-11-22 15:56 -0800
              Re: NULL as the empty string Melzzzzz <Melzzzzz@zzzzz.com> - 2017-11-23 00:06 +0000
                Re: NULL as the empty string supercat@casperkitty.com - 2017-11-23 17:31 -0800
                Re: NULL as the empty string jacobnavia <jacob@jacob.remcomp.fr> - 2017-11-24 09:42 +0100
                Re: NULL as the empty string supercat@casperkitty.com - 2017-11-24 13:47 -0800
    Re: NULL as the empty string Jorgen Grahn <grahn+nntp@snipabacken.se> - 2017-11-22 06:46 +0000
    Re: NULL as the empty string John Bode <jfbode1029@gmail.com> - 2017-12-08 10:27 -0800
      Re: NULL as the empty string Keith Thompson <kst-u@mib.org> - 2017-12-08 11:11 -0800
        Re: NULL as the empty string jacobnavia <jacob@jacob.remcomp.fr> - 2017-12-08 21:39 +0100
          Re: NULL as the empty string Keith Thompson <kst-u@mib.org> - 2017-12-08 13:03 -0800
            Re: NULL as the empty string jacobnavia <jacob@jacob.remcomp.fr> - 2017-12-08 22:50 +0100
              Re: NULL as the empty string Keith Thompson <kst-u@mib.org> - 2017-12-08 15:19 -0800
                Re: NULL as the empty string jacobnavia <jacob@jacob.remcomp.fr> - 2017-12-09 00:35 +0100
                Re: NULL as the empty string Keith Thompson <kst-u@mib.org> - 2017-12-08 16:05 -0800
                Re: NULL as the empty string jacobnavia <jacob@jacob.remcomp.fr> - 2017-12-09 01:22 +0100
                Re: NULL as the empty string Keith Thompson <kst-u@mib.org> - 2017-12-08 17:39 -0800
                Re: NULL as the empty string John Bode <jfbode1029@gmail.com> - 2017-12-11 12:22 -0800
                Re: NULL as the empty string jacobnavia <jacob@jacob.remcomp.fr> - 2017-12-09 01:29 +0100
                Re: NULL as the empty string Keith Thompson <kst-u@mib.org> - 2017-12-08 17:47 -0800
                Re: NULL as the empty string jacobnavia <jacob@jacob.remcomp.fr> - 2017-12-09 07:05 +0100
                Re: NULL as the empty string David Brown <david.brown@hesbynett.no> - 2017-12-09 18:37 +0100
                Re: NULL as the empty string Keith Thompson <kst-u@mib.org> - 2017-12-09 11:53 -0800
                Re: NULL as the empty string supercat@casperkitty.com - 2017-12-12 10:49 -0800
                Re: NULL as the empty string Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2017-12-12 13:39 -0800
                Re: NULL as the empty string supercat@casperkitty.com - 2017-12-12 16:05 -0800
                Re: NULL as the empty string Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2017-12-13 03:43 -0800
                Re: NULL as the empty string supercat@casperkitty.com - 2017-12-13 08:45 -0800
                Re: NULL as the empty string Keith Thompson <kst-u@mib.org> - 2017-12-13 09:12 -0800
                Re: NULL as the empty string Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2017-12-13 13:27 -0800
                Re: NULL as the empty string Keith Thompson <kst-u@mib.org> - 2017-12-13 14:02 -0800
                Re: NULL as the empty string asetofsymbols@gmail.com - 2017-12-13 14:58 -0800
                Re: NULL as the empty string asetofsymbols@gmail.com - 2017-12-13 15:11 -0800
                Re: NULL as the empty string Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2017-12-14 03:49 -0800
                Re: NULL as the empty string mark.bluemel@gmail.com - 2017-12-14 04:05 -0800
                Re: NULL as the empty string David Brown <david.brown@hesbynett.no> - 2017-12-14 13:09 +0100
                Re: NULL as the empty string Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2017-12-14 05:02 -0800
                Re: NULL as the empty string David Brown <david.brown@hesbynett.no> - 2017-12-14 14:54 +0100
                Re: NULL as the empty string supercat@casperkitty.com - 2017-12-14 07:38 -0800
                Re: NULL as the empty string Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2017-12-14 09:50 -0800
                Re: NULL as the empty string Keith Thompson <kst-u@mib.org> - 2017-12-14 09:20 -0800
                Re: NULL as the empty string supercat@casperkitty.com - 2017-12-14 09:53 -0800
                Re: NULL as the empty string Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2017-12-14 12:57 -0800
                Re: NULL as the empty string herrmannsfeldt@gmail.com - 2017-12-14 17:22 -0800
                Re: NULL as the empty string Keith Thompson <kst-u@mib.org> - 2017-12-14 17:26 -0800
      Re: NULL as the empty string jacobnavia <jacob@jacob.remcomp.fr> - 2017-12-08 21:23 +0100
        Re: NULL as the empty string Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2017-12-08 13:41 -0800
          Re: NULL as the empty string jacobnavia <jacob@jacob.remcomp.fr> - 2017-12-08 22:54 +0100
  Re: NULL as the empty string supercat@casperkitty.com - 2017-11-21 15:17 -0800
    Re: NULL as the empty string jacobnavia <jacob@jacob.remcomp.fr> - 2017-11-22 00:26 +0100
      Re: NULL as the empty string supercat@casperkitty.com - 2017-11-21 16:03 -0800
  Re: NULL as the empty string "Pascal J. Bourguignon" <pjb@informatimago.com> - 2017-11-22 00:27 +0100
    Re: NULL as the empty string jacobnavia <jacob@jacob.remcomp.fr> - 2017-11-22 00:42 +0100
      Re: NULL as the empty string Keith Thompson <kst-u@mib.org> - 2017-11-21 16:05 -0800
        Re: NULL as the empty string herrmannsfeldt@gmail.com - 2017-12-06 22:33 -0800
          Re: NULL as the empty string supercat@casperkitty.com - 2017-12-07 12:04 -0800
            Re: NULL as the empty string jacobnavia <jacob@jacob.remcomp.fr> - 2017-12-07 23:20 +0100
              Re: NULL as the empty string supercat@casperkitty.com - 2017-12-07 15:04 -0800
  Re: NULL as the empty string Keith Thompson <kst-u@mib.org> - 2017-11-21 15:28 -0800
  Re: NULL as the empty string Thiago Adams <thiago.adams@gmail.com> - 2017-11-21 16:04 -0800
  Re: NULL as the empty string Siri Cruise <chine.bleu@yahoo.com> - 2017-11-21 16:25 -0800
    Re: NULL as the empty string jacobnavia <jacob@jacob.remcomp.fr> - 2017-11-22 01:34 +0100
  Re: NULL as the empty string bartc <bc@freeuk.com> - 2017-11-22 00:36 +0000
  Re: NULL as the empty string Öö Tiib <ootiib@hot.ee> - 2017-11-21 23:07 -0800
  NULL as the empty string asetofsymbols@gmail.com - 2017-11-23 22:23 -0800
  Re: NULL as the empty string Geoff <geoff@invalid.invalid> - 2017-12-09 09:05 -0800
    Re: NULL as the empty string Lew Pitcher <lew.pitcher@digitalfreehold.ca> - 2017-12-09 12:40 -0500
  Re: NULL as the empty string gordonb.yj0bc@burditt.org (Gordon Burditt) - 2017-12-09 13:50 -0600
  Re: NULL as the empty string Ian Collins <ian-news@hotmail.com> - 2017-12-10 08:59 +1300
    Re: NULL as the empty string Keith Thompson <kst-u@mib.org> - 2017-12-09 12:22 -0800
      Re: NULL as the empty string jacobnavia <jacob@jacob.remcomp.fr> - 2017-12-11 01:42 +0100
        Re: NULL as the empty string Keith Thompson <kst-u@mib.org> - 2017-12-10 19:20 -0800
          Re: NULL as the empty string jacobnavia <jacob@jacob.remcomp.fr> - 2017-12-11 18:56 +0100
            Re: NULL as the empty string Keith Thompson <kst-u@mib.org> - 2017-12-11 11:19 -0800
        Re: NULL as the empty string supercat@casperkitty.com - 2017-12-15 09:29 -0800
          Re: NULL as the empty string Thiago Adams <thiago.adams@gmail.com> - 2018-01-05 08:28 -0800
            Re: NULL as the empty string supercat@casperkitty.com - 2018-01-05 09:37 -0800
              Re: NULL as the empty string Thiago Adams <thiago.adams@gmail.com> - 2018-01-05 17:08 -0800
    Re: NULL as the empty string supercat@casperkitty.com - 2017-12-15 09:18 -0800

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