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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next prev parent 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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