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From: "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com>
Newsgroups: comp.lang.c
Subject: Re: question about nullptr
Date: Tue, 9 Jul 2024 00:12:21 -0700
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On 7/9/2024 12:02 AM, Richard Harnden wrote:
> 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
> 
> 

p = nullptr;

(0 == p == nullptr == NULL == 0) == true ?

Am I missing something here? If so, here is a preemptive: Shit!