Re: [TUHS] reviving a bit of WWB

[Clem Cole <clemc@ccc.com>]

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Yep.   They all suck.  As Dennis said, “C is quirky” and part of the issue
is HW is even more so.  Clem

On Sun, Sep 20, 2020 at 8:10 PM Warner Losh <imp@bsdimp.com> wrote:

> To two places: stddef.h and stdlib.h :(.
>
> It's interesting to see the different bugs 0, 0L, (char *)0 and (void *)0
> expose or hide as definitions of NULL.
>
> 0 is fine if sizeof(int) == sizeof(void *). Otherwise varadic function
> calls break. 0L is the same, but for long. The pointer definitions run into
> trouble in other contexts since NULL is often incorrectly used as a
> terminating byte in a string instead of '\0'. (void *) has issues with
> const pointers, some of which are relevant if you use it in the wrong
> context.
>
> There were quite spirited debates back in the day for which one was best.
> They all suck. C++ invented a null pointer symbol because it's type rules
> were enough different than C to make a universal NULL #define impossible.
> Is that better or worse? Don't know. It's different.
>
> Glad to see the null-pointer need not have all zero bits being different
> than a 0 constant shall be the null-pointer in sufficient detail.
>
> Warner
>
> On Sun, Sep 20, 2020, 5:54 PM Clem Cole <clemc@ccc.com> wrote:
>
>> 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
>>
>>
>>
>
> --
Sent from a handheld expect more typos than usual

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