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From: Clem Cole <clemc@ccc.com>
To: Norman Wilson <norman@oclsc.org>
Cc: tuhs@tuhs.org
Subject: Re: [TUHS] reviving a bit of WWB
Date: Sun, 20 Sep 2020 19:53:02 -0400	[thread overview]
Message-ID: <CAC20D2PqgrYnADwJJc3rvtgRXB92FKgCT2ycot9bhUoEGPe=+Q@mail.gmail.com> (raw)
In-Reply-To: <20200920230057.C5D1A4422E@lignose.oclsc.org>

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Norman NULL has to be defined and I said that/showed it.   The standard
says where.  I was not trying to compile NULL without a definition which I
agree it not legal.  If that is what Doug was implying I missed understood
him but I note NULL was introduced in Typesetter C /V7 where those compiler
s set it to 0 in studio but the ANSI/ISO moved it.

On Sun, Sep 20, 2020 at 7:03 PM Norman Wilson <norman@oclsc.org> wrote:

> Doug McIlroy:
>
>
>
>   To put it more strongly. this is not a legal C source file.
>
>           char *s = NULL;
>
>   But this is.
>
>           char *s = 0;
>
>
>
> Clem Cole:
>
>
>
>    67)The macro NULL is defined in <stddef.h> (and other headers) as a null
>
>    pointer constant; see 7.19.
>
>
>
> ====
>
>
>
> $ cat null.c
>
> char *s = NULL;
>
> $ cat zero.c
>
> char *s = 0;
>
> $
>
>
>
> zero.c is a legal C program.  null.c is not.  Create
>
> files exactly as shown and compile them if you don't
>
> believe me.
>
>
>
> Prepend `#include <stddef.h>' (or <stdlib.h> or <stdio.h>)
>
> to null.c and it becomes legal, but I think that's Doug's
>
> point: you need an include file.
>
>
>
> Personally I prefer to use NULL instead of 0 when spelling
>
> out a null pointer, because I think it's clearer:
>
>         if ((buf = malloc(SIZE)) == NULL)
>
>                 error("dammit andrew");
>
> though I am willing to omit it when there's no confusion
>
> about = vs ==:
>
>         if (*p)
>
>                 dammit(*p, "andrew");
>
>
>
> But that's just a question of style, and Doug's is fine too.
>
>
>
> The language does not require the compiler to pre-define
>
> NULL or to recognize it as a keyword; you have to include
>
> an appropriate standard header file.
>
>
>
> Norman Wilson
>
> Toronto ON (not 0N nor NULLN)
>
> --
Sent from a handheld expect more typos than usual

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  reply	other threads:[~2020-09-20 23:53 UTC|newest]

Thread overview: 57+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-09-20 23:00 Norman Wilson
2020-09-20 23:53 ` Clem Cole [this message]
2020-09-21  0:00   ` Clem Cole
2020-09-21  2:24     ` John Cowan
2020-09-21  0:09   ` Warner Losh
2020-09-21  1:05     ` Clem Cole
2020-09-21  5:55     ` Steve Nickolas
2020-09-21  5:59       ` Warner Losh
2020-09-21 18:40         ` Paul Winalski
2020-09-21 19:56           ` Dan Cross
2020-09-21 20:50       ` John Cowan
2020-09-21 21:22         ` Rob Pike
2020-09-21 21:57           ` Clem Cole
2020-09-21 23:56             ` John Cowan
2020-09-22  0:54               ` Richard Salz
2020-09-21 21:39         ` Steve Nickolas
  -- strict thread matches above, loose matches on Subject: below --
2020-09-25 14:19 Doug McIlroy
2020-09-28 17:35 ` Angelo Papenhoff
2020-09-20 22:51 Norman Wilson
2020-09-19  1:51 Doug McIlroy
2020-09-20 18:42 ` arnold
2020-09-20 19:28   ` Will Senn
2020-09-20 20:12     ` Steve Nickolas
2020-09-20 20:26       ` Doug McIlroy
2020-09-20 20:57         ` Doug McIlroy
2020-09-20 22:13           ` Clem Cole
2020-09-21 20:43             ` Steffen Nurpmeso
2020-09-20 20:58         ` Steve Nickolas
2020-09-20 21:33           ` Brantley Coile
2020-10-07  5:43             ` scj
2020-09-20 21:35           ` John Cowan
2021-02-02 23:08             ` Greg A. Woods
2021-02-02 23:47               ` Larry McVoy
2021-02-03  0:11                 ` Dave Horsfall
2021-02-03  0:19                   ` Larry McVoy
2021-02-03  2:04                     ` Richard Salz
2021-02-03  3:32                       ` Dave Horsfall
2021-02-03  4:32                         ` M Douglas McIlroy
2021-02-03 11:27                           ` Peter Jeremy via TUHS
2021-02-03 20:09                             ` Dave Horsfall
2021-02-03 20:13                               ` Niklas Karlsson
2021-02-03 23:46                               ` Tom Lyon
2021-02-03 22:19                           ` Dave Horsfall
2021-02-03 22:55                             ` M Douglas McIlroy
2020-09-20 22:15           ` Clem Cole
2020-09-20 22:47             ` John Cowan
2020-09-21 20:48               ` Steffen Nurpmeso
2020-09-21 20:46           ` Steffen Nurpmeso
2020-09-24  2:25       ` Dave Horsfall
2020-09-24  2:33         ` Clem Cole
2020-09-27  5:54           ` Dave Horsfall
2020-09-24 17:19         ` Paul Winalski
2020-09-24 18:17           ` John Cowan
2020-10-07  5:47   ` scj
2020-10-07  9:20     ` arnold
2020-10-08  0:27     ` Dave Horsfall
2020-10-08  3:08       ` John Cowan

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