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From: "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com>
Newsgroups: comp.lang.c
Subject: Re: question about nullptr
Date: Mon, 8 Jul 2024 23:17:23 -0700
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On 7/8/2024 10:42 PM, Richard Harnden wrote:
> On 06/07/2024 17:57, David Brown wrote:
>> On 06/07/2024 16:39, Richard Damon wrote:
>>> On 7/6/24 7:49 AM, Thiago Adams wrote:
>>>> If you were creating C code today and could use a C23 compiler, 
>>>> would you use nullptr instead of NULL?
>>>>
>>>> I am asking because I think I will keep using NULL.
>>>>
>>>> I like nullptr semantics but I don't like to introduce new element 
>>>> (nullptr) inside the code with no guarantee that the code will not 
>>>> mix both.
>>>>
>>>> In the past we also didn't have a guarantee we are not mixing 0 or 
>>>> NULL.
>>>>
>>>> I think the best scenario for a team guideline would be a style 
>>>> warning if 0 or nullptr is used and NULL to be defined as nullptr in 
>>>> a C23 compiler.
>>>>
>>>
>>> The (small) problem with 0 or NULL being use is that in a context 
>>> where you THINK you are passing a pointer, but the function actually 
>>> is taking an integer value, 0 or NULL (defined as a 0) passes the 
>>> syntax check.
>>>
>>> If C23 REQURIED NULL to be defined as nullptr, then NULL would have 
>>> been used, but as far as I know, it is still allowed to be defined as 
>>> 0 (unless you also have POSIX compatibility).
>>>
>>> With POSIX Compatibility, where NULL must have the type of (void*) 
>>> you also avoid the possible error, and thus the desire to use nullptr.
>>
>> I hope that defining NULL as nullptr will become common - but I would 
>> be surprised to ever see it being required by C standards.
>>
>> The ideal would be for C libraries to define NULL as nullptr and for C 
>> compilers to support a flag like gcc's 
>> "-Wzero-as-null-pointer-constant" warning (it is currently C++ only).  
>> Then people can easily eliminate
>> any mixup between integer 0 and null pointer constants by using that 
>> flag and either NULL or nullptr, according to taste.  (And those who 
>> don't want such checks, are not required to change.)
>>
>>
> 
> So, if malloc was changed to 'returns nullptr and sets errno on error', 
> will you still be able to say:
> 
> if ( p == NULL ) ...
> if ( !p ) ...
> 
> ?

This of a pointer p where:

p = 0;

p == NULL == true;

p == 0 == true;

Therefore (! p) means that p is 0, or NULL if you will..

Fair enough?

Side note:

Tell NULL and 0 to NAND CAT:

https://youtu.be/kdCJunw_Jgg

How long can you listen to this before you snuff it?