From: Chris Hall <gcc@gmch.uk>
Cc: gcc-help <gcc-help@gcc.gnu.org>
Subject: Re: Should atomic_xxx() functions reject not-_Atomic() arguments ?
Date: Fri, 06 Mar 2020 16:17:00 -0000 [thread overview]
Message-ID: <02d60fa2-0671-31c3-3d4a-1749eb0a6c7b@gmch.uk> (raw)
In-Reply-To: <76f5d98b-affc-111b-5493-2557f8facaf1@gmch.uk>
On 28/02/2020 15:27, Chris Hall wrote:
> On 28/02/2020 01:01, Jim Wilson wrote:
>> On Thu, Feb 27, 2020 at 7:20 AM Chris Hall <gcc@gmch.uk> wrote:
>>> Now, the Standard also tells us that _Atomic(uint64_t) and uint64_t may
>>> have different sizes, representations and alignment. So I guess:
>>> bar = atomic_fetch_add(&bar, 1) ;
>>> should be an error ?
>> __atomic_fetch_add accepts any integer or pointer type. So the fact
>> that _Atomic(uint64_t) and uint64_t may be different types is not a
>> problem, as long as they are still integer types. This works like an
>> overloaded function in C++.
>>
>> https://gcc.gnu.org/onlinedocs/gcc-9.2.0/gcc/_005f_005fatomic-Builtins.html#g_t_005f_005fatomic-Builtins
> Sure. But the Standard atomic_fetch_add() takes an _Atomic(xxx)* (as
> the first parameter), and for the reasons given, I understand that
> uint64_t* is not compatible with _Atomic(uint64_t)*.
FWIW: clang gets this right, and where the Standard says a parameter
must be an _Atomic(foo_t)* [for a standard atomic_xxx()], clang rejects
foo_t* arguments.
Chris
next prev parent reply other threads:[~2020-03-06 16:17 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <72f6344e-d8b2-bab4-b047-63e298063492@gmch.uk>
2020-02-27 17:27 ` Chris Hall
2020-02-28 15:23 ` Jim Wilson
2020-02-28 21:04 ` Chris Hall
2020-03-06 16:17 ` Chris Hall [this message]
2020-03-06 17:46 ` Jonathan Wakely
2020-03-07 11:00 ` Andrew Haley
2020-03-07 19:27 ` Jonathan Wakely
2020-03-07 13:04 ` Chris Hall
2020-03-07 19:29 ` Jonathan Wakely
2020-03-08 20:11 ` Martin Sebor
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