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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 06:42:30 +0100
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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 ) ...

?