Path: ...!news.mixmin.net!eternal-september.org!feeder3.eternal-september.org!news.eternal-september.org!.POSTED!not-for-mail
From: Thiago Adams <thiago.adams@gmail.com>
Newsgroups: comp.lang.c
Subject: Re: C23 auto x C++ auto.
Date: Sun, 26 May 2024 14:02:56 -0300
Organization: A noiseless patient Spider
Lines: 73
Message-ID: <v2vq00$3fq60$2@dont-email.me>
References: <v2vela$3e4pn$1@dont-email.me> <20240526172307.00005e3e@yahoo.com>
 <v2viv9$3el3j$1@dont-email.me>
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: 8bit
Injection-Date: Sun, 26 May 2024 19:02:57 +0200 (CEST)
Injection-Info: dont-email.me; posting-host="b36d0c53be6e431910f898a3cb57d404";
	logging-data="3664064"; mail-complaints-to="abuse@eternal-september.org";	posting-account="U2FsdGVkX1+W4Z+xIggfUDg/Aq/uskU/lM8OHQ+faJw="
User-Agent: Mozilla Thunderbird
Cancel-Lock: sha1:3nrgj2DjgfPJC5eGjAdOOD0vmRo=
In-Reply-To: <v2viv9$3el3j$1@dont-email.me>
Content-Language: en-GB
Bytes: 2762

Em 5/26/2024 12:03 PM, Thiago Adams escreveu:
> Em 5/26/2024 11:23 AM, Michael S escreveu:
>> On Sun, 26 May 2024 10:49:30 -0300
>> Thiago Adams <thiago.adams@gmail.com> wrote:
>>
>>> I think most people is not aware of this:
>>>
>>>   From 3096 C23 draft
>>>
>>> "
>>> 6.7.9 Type inference
>>> ...
>>>    2 For such a declaration that is the definition of an object the
>>> init- declarator shall have the form
>>>
>>>      direct-declarator = assignment-expression
>>> "
>>>
>>> Basically "direct-declarator" differs from "declarator" because it
>>> does not contains pointer.
>>>
>>> Then the type inference using auto and pointer is something undefined
>>> in C23.
>>>
>>> struct node{
>>>       struct node * next;
>>>
>>> };
>>> int main(){
>>>      struct node node = {};
>>>      auto * p = node.next;
>>> }
>>>
>>> <source>:7:4: error: 'auto' requires a plain identifier, possibly
>>> with attributes, as declarator
>>>       7 |    auto * p = node.next;
>>>         |    ^~~~
>>>
>>> This differs from C++.
>>>
>>>
>>
>> Differs in positive way. Less confusing.
>>
> I agree!
> 
> 

clang still accepts it.

https://godbolt.org/z/nxhcWGo5h

"For such a declaration that is the definition of an object the 
init-declarator shall have the form

direct-declarator = assignment-expression

...
177) Implementations need not accept a direct declarator that is not of 
the form

   identifier attribute-specifier-sequence opt

optionally enclosed in balanced pairs of parentheses;

if a direct declarator of a different form is accepted, the behavior is 
implementation-defined.
"