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From: Richard Harnden <richard.nospam@gmail.invalid>
Newsgroups: comp.lang.c
Subject: Re: question about nullptr
Date: Tue, 9 Jul 2024 08:02:42 +0100
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On 09/07/2024 07:17, Chris M. Thomasson wrote:
> 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;

No, I mean when p = nullptr