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Re: std::atomic<T>::is_lock_free()

From "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com>
Newsgroups comp.lang.c++
Subject Re: std::atomic<T>::is_lock_free()
Date 2019-11-12 15:21 -0800
Organization Aioe.org NNTP Server
Message-ID <qqfepc$1vi7$1@gioia.aioe.org> (permalink)
References (2 earlier) <qqeb20$asj$1@news.albasani.net> <qqecn5$o7a$1@news.albasani.net> <h302fhFs1t7U1@mid.individual.net> <qqenae$thq$1@news.albasani.net> <h30f5hF722U1@mid.individual.net>

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On 11/12/2019 11:23 AM, Bo Persson wrote:
> On 2019-11-12 at 17:40, Bonita Montero wrote:
>>> It might just be for historic reasons. In C++14 we only have the 
>>> function and it is speced:
>>> Returns: True if the object’s operations are lock-free, false otherwise.
>>> It said nothing about whether different objects of the same type 
>>> always returned the same value.
>>
>> There's no logical reason why they should.
> 
> So therefore we now also have the member is_always_lock_free.  :-)
> 
> In my previous post I a bit hastily stated that the functions always 
> return that value, but in reality that is only true if the value *is* true.
> 
> When is_always_lock_free is false, the functions just *might* return 
> true in some cases and false in others.
> 
> Just to make it more complicated, there are also macros for some types, 
> like ATOMIC_INT_LOCK_FREE (which can have the value "sometimes lock 
> free" :-).

Indeed! The atomic types are allowed to be created using locks or even 
obstruction free constructs:

All lock-free is obstruction free, but not all obstruction free is 
lock-free... ;^)

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std::atomic<T>::is_lock_free() Bonita Montero <Bonita.Montero@gmail.com> - 2019-11-12 10:54 +0100
  Re: std::atomic<T>::is_lock_free() Bonita Montero <Bonita.Montero@gmail.com> - 2019-11-12 11:24 +0100
    Re: std::atomic<T>::is_lock_free() Bonita Montero <Bonita.Montero@gmail.com> - 2019-11-12 14:11 +0100
      Re: std::atomic<T>::is_lock_free() Bonita Montero <Bonita.Montero@gmail.com> - 2019-11-12 14:39 +0100
        Re: std::atomic<T>::is_lock_free() Bo Persson <bo@bo-persson.se> - 2019-11-12 16:46 +0100
          Re: std::atomic<T>::is_lock_free() Bonita Montero <Bonita.Montero@gmail.com> - 2019-11-12 17:40 +0100
            Re: std::atomic<T>::is_lock_free() Bo Persson <bo@bo-persson.se> - 2019-11-12 20:23 +0100
              Re: std::atomic<T>::is_lock_free() "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2019-11-12 15:21 -0800
              Re: std::atomic<T>::is_lock_free() "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2019-11-14 13:09 -0800
              Re: std::atomic<T>::is_lock_free() Bonita Montero <Bonita.Montero@gmail.com> - 2019-11-13 06:34 +0100
                Re: std::atomic<T>::is_lock_free() "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2019-11-13 22:00 -0800
                Re: std::atomic<T>::is_lock_free() Bonita Montero <Bonita.Montero@gmail.com> - 2019-11-14 07:26 +0100
                Re: std::atomic<T>::is_lock_free() "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2019-11-13 22:33 -0800
                Re: std::atomic<T>::is_lock_free() "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2019-11-13 22:33 -0800
                Re: std::atomic<T>::is_lock_free() Bonita Montero <Bonita.Montero@gmail.com> - 2019-11-14 07:51 +0100
                Re: std::atomic<T>::is_lock_free() Bonita Montero <Bonita.Montero@gmail.com> - 2019-11-14 07:50 +0100
                Re: std::atomic<T>::is_lock_free() "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2019-11-13 23:14 -0800
                Re: std::atomic<T>::is_lock_free() Bonita Montero <Bonita.Montero@gmail.com> - 2019-11-14 10:43 +0100
  Re: std::atomic<T>::is_lock_free() "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2019-11-12 15:14 -0800
    Re: std::atomic<T>::is_lock_free() Bonita Montero <Bonita.Montero@gmail.com> - 2019-11-14 13:11 +0100
  Re: std::atomic<T>::is_lock_free() Öö Tiib <ootiib@hot.ee> - 2019-11-14 07:53 -0800
    Re: std::atomic<T>::is_lock_free() Bonita Montero <Bonita.Montero@gmail.com> - 2019-11-14 16:57 +0100
      Re: std::atomic<T>::is_lock_free() Öö Tiib <ootiib@hot.ee> - 2019-11-14 08:16 -0800
        Re: std::atomic<T>::is_lock_free() Bonita Montero <Bonita.Montero@gmail.com> - 2019-11-14 17:26 +0100
          Re: std::atomic<T>::is_lock_free() Bonita Montero <Bonita.Montero@gmail.com> - 2019-11-14 17:28 +0100
          Re: std::atomic<T>::is_lock_free() Öö Tiib <ootiib@hot.ee> - 2019-11-14 08:30 -0800
            Re: std::atomic<T>::is_lock_free() Bonita Montero <Bonita.Montero@gmail.com> - 2019-11-14 17:33 +0100
              Re: std::atomic<T>::is_lock_free() "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2019-11-14 13:41 -0800
                Re: std::atomic<T>::is_lock_free() Bonita Montero <Bonita.Montero@gmail.com> - 2019-11-15 09:31 +0100
                Re: std::atomic<T>::is_lock_free() "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2019-11-15 12:59 -0800
                Re: std::atomic<T>::is_lock_free() scott@slp53.sl.home (Scott Lurndal) - 2019-11-15 21:47 +0000
                Re: std::atomic<T>::is_lock_free() "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2019-11-15 13:56 -0800
                Re: std::atomic<T>::is_lock_free() scott@slp53.sl.home (Scott Lurndal) - 2019-11-16 18:07 +0000
                Re: std::atomic<T>::is_lock_free() "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2019-11-16 13:55 -0800
                Re: std::atomic<T>::is_lock_free() scott@slp53.sl.home (Scott Lurndal) - 2019-11-16 22:13 +0000
                Re: std::atomic<T>::is_lock_free() "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2019-11-16 18:40 -0800
                Re: std::atomic<T>::is_lock_free() James Kuyper <jameskuyper@alumni.caltech.edu> - 2019-11-17 18:39 -0500
                Re: std::atomic<T>::is_lock_free() "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2019-11-17 20:59 -0800
                Re: std::atomic<T>::is_lock_free() "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2019-11-17 21:00 -0800
                Re: std::atomic<T>::is_lock_free() James Kuyper <jameskuyper@alumni.caltech.edu> - 2019-11-18 08:25 -0500
                Re: std::atomic<T>::is_lock_free() "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2019-11-18 18:24 -0800
                Re: std::atomic<T>::is_lock_free() "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2019-11-15 13:59 -0800
                Re: std::atomic<T>::is_lock_free() Ian Collins <ian-news@hotmail.com> - 2019-11-16 11:08 +1300
                Re: std::atomic<T>::is_lock_free() Öö Tiib <ootiib@hot.ee> - 2019-11-15 15:39 -0800
                Re: std::atomic<T>::is_lock_free() Bonita Montero <Bonita.Montero@gmail.com> - 2019-11-16 07:22 +0100
                Re: std::atomic<T>::is_lock_free() Öö Tiib <ootiib@hot.ee> - 2019-11-16 08:06 -0800
                Re: std::atomic<T>::is_lock_free() Bonita Montero <Bonita.Montero@gmail.com> - 2019-11-16 17:13 +0100
                Re: std::atomic<T>::is_lock_free() Öö Tiib <ootiib@hot.ee> - 2019-11-16 08:26 -0800
                Re: std::atomic<T>::is_lock_free() Bonita Montero <Bonita.Montero@gmail.com> - 2019-11-16 19:27 +0100
                Re: std::atomic<T>::is_lock_free() Öö Tiib <ootiib@hot.ee> - 2019-11-16 10:37 -0800
                Re: std::atomic<T>::is_lock_free() Bonita Montero <Bonita.Montero@gmail.com> - 2019-11-16 19:47 +0100
                Re: std::atomic<T>::is_lock_free() Öö Tiib <ootiib@hot.ee> - 2019-11-16 11:34 -0800
                Re: std::atomic<T>::is_lock_free() Bonita Montero <Bonita.Montero@gmail.com> - 2019-11-17 09:17 +0100
                Re: std::atomic<T>::is_lock_free() Öö Tiib <ootiib@hot.ee> - 2019-11-17 01:52 -0800
                Re: std::atomic<T>::is_lock_free() Bonita Montero <Bonita.Montero@gmail.com> - 2019-11-17 11:23 +0100
                Re: std::atomic<T>::is_lock_free() Öö Tiib <ootiib@hot.ee> - 2019-11-17 03:22 -0800
                Re: std::atomic<T>::is_lock_free() Bonita Montero <Bonita.Montero@gmail.com> - 2019-11-17 14:20 +0100
                Re: std::atomic<T>::is_lock_free() Öö Tiib <ootiib@hot.ee> - 2019-11-17 06:39 -0800
                Re: std::atomic<T>::is_lock_free() Bonita Montero <Bonita.Montero@gmail.com> - 2019-11-17 15:49 +0100
                Re: std::atomic<T>::is_lock_free() Öö Tiib <ootiib@hot.ee> - 2019-11-17 22:54 -0800
                Re: std::atomic<T>::is_lock_free() Bonita Montero <Bonita.Montero@gmail.com> - 2019-11-18 08:03 +0100
                Re: std::atomic<T>::is_lock_free() Tim Rentsch <tr.17687@z991.linuxsc.com> - 2019-11-28 15:39 -0800
                Re: std::atomic<T>::is_lock_free() Öö Tiib <ootiib@hot.ee> - 2019-11-28 16:33 -0800
                Re: std::atomic<T>::is_lock_free() Tim Rentsch <tr.17687@z991.linuxsc.com> - 2020-01-10 22:48 -0800
                Re: std::atomic<T>::is_lock_free() Öö Tiib <ootiib@hot.ee> - 2020-01-11 00:24 -0800
                Re: std::atomic<T>::is_lock_free() Tim Rentsch <tr.17687@z991.linuxsc.com> - 2020-01-14 07:16 -0800
                Re: std::atomic<T>::is_lock_free() Öö Tiib <ootiib@hot.ee> - 2020-01-14 08:55 -0800
                Re: std::atomic<T>::is_lock_free() Tim Rentsch <tr.17687@z991.linuxsc.com> - 2020-01-21 02:01 -0800
                Re: std::atomic<T>::is_lock_free() James Kuyper <jameskuyper@alumni.caltech.edu> - 2020-01-21 06:00 -0800
                Re: std::atomic<T>::is_lock_free() Bonita Montero <Bonita.Montero@gmail.com> - 2019-11-17 15:58 +0100
                Re: std::atomic<T>::is_lock_free() "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2019-11-17 21:01 -0800
                Re: std::atomic<T>::is_lock_free() Bonita Montero <Bonita.Montero@gmail.com> - 2019-11-18 07:00 +0100
                Re: std::atomic<T>::is_lock_free() Öö Tiib <ootiib@hot.ee> - 2019-11-17 22:45 -0800
                Re: std::atomic<T>::is_lock_free() Bonita Montero <Bonita.Montero@gmail.com> - 2019-11-18 07:52 +0100
                Re: std::atomic<T>::is_lock_free() Bonita Montero <Bonita.Montero@gmail.com> - 2019-11-18 08:10 +0100
                Re: std::atomic<T>::is_lock_free() Öö Tiib <ootiib@hot.ee> - 2019-11-17 23:23 -0800
                Re: std::atomic<T>::is_lock_free() Ian Collins <ian-news@hotmail.com> - 2019-11-18 20:26 +1300
                Re: std::atomic<T>::is_lock_free() Öö Tiib <ootiib@hot.ee> - 2019-11-17 23:05 -0800
                Re: std::atomic<T>::is_lock_free() Tim Rentsch <tr.17687@z991.linuxsc.com> - 2019-11-28 15:44 -0800
                Re: std::atomic<T>::is_lock_free() Öö Tiib <ootiib@hot.ee> - 2019-11-28 16:43 -0800
                Re: std::atomic<T>::is_lock_free() Tim Rentsch <tr.17687@z991.linuxsc.com> - 2020-01-11 06:41 -0800
        Re: std::atomic<T>::is_lock_free() "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2019-11-14 13:33 -0800
  Re: std::atomic<T>::is_lock_free() Melzzzzz <Melzzzzz@zzzzz.com> - 2019-11-14 19:08 +0000
    Re: std::atomic<T>::is_lock_free() Bonita Montero <Bonita.Montero@gmail.com> - 2019-11-14 20:12 +0100
      Re: std::atomic<T>::is_lock_free() "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2019-11-14 13:35 -0800
  Re: std::atomic<T>::is_lock_free() "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2019-11-14 13:32 -0800
    Re: std::atomic<T>::is_lock_free() "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2019-11-14 13:37 -0800
    Re: std::atomic<T>::is_lock_free() Bonita Montero <Bonita.Montero@gmail.com> - 2019-11-15 09:32 +0100
      Re: std::atomic<T>::is_lock_free() "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2019-11-15 13:06 -0800
  Re: std::atomic<T>::is_lock_free() Öö Tiib <ootiib@hot.ee> - 2019-11-14 02:29 -0800
    Re: std::atomic<T>::is_lock_free() Bonita Montero <Bonita.Montero@gmail.com> - 2019-11-14 11:45 +0100

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