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* [Bug libstdc++/115402] New: std::atomic_ref<volatile T> compile-error in compare_exchange_[weak/strong]() and wait()
@ 2024-06-09 7:19 lewissbaker.opensource at gmail dot com
2024-06-09 17:02 ` [Bug libstdc++/115402] " pinskia at gcc dot gnu.org
` (6 more replies)
0 siblings, 7 replies; 8+ messages in thread
From: lewissbaker.opensource at gmail dot com @ 2024-06-09 7:19 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115402
Bug ID: 115402
Summary: std::atomic_ref<volatile T> compile-error in
compare_exchange_[weak/strong]() and wait()
Product: gcc
Version: 15.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: libstdc++
Assignee: unassigned at gcc dot gnu.org
Reporter: lewissbaker.opensource at gmail dot com
Target Milestone: ---
See https://godbolt.org/z/q4jYvPaah
The following code-snippet fails to compile:
volatile int vi = 0;
std::atomic_ref<volatile int> vref(vi);
int val = vref.load(); // ok
vref.exchange(val); // ok
vref.compare_exchange_weak(val, 0); // error
vref.compare_exchange_strong(val, 0); // error
vref.wait(0); // error
Fails with error messages like:
.../include/c++/15.0.0/bits/atomic_base.h: In instantiation of 'bool
std::__atomic_ref<_Tp, true, false>::compare_exchange_weak(_Tp&, _Tp,
std::memory_order, std::memory_order) const [with _Tp = volatile int]':
/opt/compiler-explorer/gcc-trunk-20240609/include/c++/15.0.0/bits/atomic_base.h:1674:30:
required from 'bool std::__atomic_ref<_Tp, true,
false>::compare_exchange_weak(_Tp&, _Tp, std::memory_order) const [with _Tp =
volatile int]'
1674 | return compare_exchange_weak(__expected, __desired, __order,
| ~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1675 | __cmpexch_failure_order(__order));
| ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
<source>:8:31: required from here
8 | vref.compare_exchange_weak(val, 0); // error
| ~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~
.../include/c++/15.0.0/bits/atomic_base.h:1656:58: error: binding reference of
type 'std::__atomic_impl::_Val<volatile int>&' {aka 'int&'} to 'volatile int'
discards qualifiers
1656 | return __atomic_impl::compare_exchange_weak<true>(
| ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^
1657 | _M_ptr, __expected, __desired, __success, __failure);
| ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
.../include/c++/15.0.0/bits/atomic_base.h:1119:52: note: initializing
argument 2 of 'bool std::__atomic_impl::compare_exchange_weak(_Tp*, _Val<_Tp>&,
_Val<_Tp>, std::memory_order, std::memory_order, bool) [with bool _AtomicRef =
true; _Tp = volatile int; _Val<_Tp> = int]'
1119 | compare_exchange_weak(_Tp* __ptr, _Val<_Tp>& __expected,
| ~~~~~~~~~~~^~~~~~~~~~
^ permalink raw reply [flat|nested] 8+ messages in thread
* [Bug libstdc++/115402] std::atomic_ref<volatile T> compile-error in compare_exchange_[weak/strong]() and wait()
2024-06-09 7:19 [Bug libstdc++/115402] New: std::atomic_ref<volatile T> compile-error in compare_exchange_[weak/strong]() and wait() lewissbaker.opensource at gmail dot com
@ 2024-06-09 17:02 ` pinskia at gcc dot gnu.org
2024-06-09 17:05 ` pinskia at gcc dot gnu.org
` (5 subsequent siblings)
6 siblings, 0 replies; 8+ messages in thread
From: pinskia at gcc dot gnu.org @ 2024-06-09 17:02 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115402
--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Created attachment 58393
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=58393&action=edit
Full testcase from compiler explorer link
^ permalink raw reply [flat|nested] 8+ messages in thread
* [Bug libstdc++/115402] std::atomic_ref<volatile T> compile-error in compare_exchange_[weak/strong]() and wait()
2024-06-09 7:19 [Bug libstdc++/115402] New: std::atomic_ref<volatile T> compile-error in compare_exchange_[weak/strong]() and wait() lewissbaker.opensource at gmail dot com
2024-06-09 17:02 ` [Bug libstdc++/115402] " pinskia at gcc dot gnu.org
@ 2024-06-09 17:05 ` pinskia at gcc dot gnu.org
2024-06-09 17:09 ` pinskia at gcc dot gnu.org
` (4 subsequent siblings)
6 siblings, 0 replies; 8+ messages in thread
From: pinskia at gcc dot gnu.org @ 2024-06-09 17:05 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115402
--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Note libc++ also fails this. So Does Microsoft's c++ library using MSVC.
So I am not sure if this is a bug or not.
^ permalink raw reply [flat|nested] 8+ messages in thread
* [Bug libstdc++/115402] std::atomic_ref<volatile T> compile-error in compare_exchange_[weak/strong]() and wait()
2024-06-09 7:19 [Bug libstdc++/115402] New: std::atomic_ref<volatile T> compile-error in compare_exchange_[weak/strong]() and wait() lewissbaker.opensource at gmail dot com
2024-06-09 17:02 ` [Bug libstdc++/115402] " pinskia at gcc dot gnu.org
2024-06-09 17:05 ` pinskia at gcc dot gnu.org
@ 2024-06-09 17:09 ` pinskia at gcc dot gnu.org
2024-06-09 17:55 ` pinskia at gcc dot gnu.org
` (3 subsequent siblings)
6 siblings, 0 replies; 8+ messages in thread
From: pinskia at gcc dot gnu.org @ 2024-06-09 17:09 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115402
--- Comment #3 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
https://cplusplus.github.io/LWG/issue3508
^ permalink raw reply [flat|nested] 8+ messages in thread
* [Bug libstdc++/115402] std::atomic_ref<volatile T> compile-error in compare_exchange_[weak/strong]() and wait()
2024-06-09 7:19 [Bug libstdc++/115402] New: std::atomic_ref<volatile T> compile-error in compare_exchange_[weak/strong]() and wait() lewissbaker.opensource at gmail dot com
` (2 preceding siblings ...)
2024-06-09 17:09 ` pinskia at gcc dot gnu.org
@ 2024-06-09 17:55 ` pinskia at gcc dot gnu.org
2024-06-10 9:19 ` redi at gcc dot gnu.org
` (2 subsequent siblings)
6 siblings, 0 replies; 8+ messages in thread
From: pinskia at gcc dot gnu.org @ 2024-06-09 17:55 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115402
--- Comment #4 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
https://lists.isocpp.org/lib/2024/06/28451.php
^ permalink raw reply [flat|nested] 8+ messages in thread
* [Bug libstdc++/115402] std::atomic_ref<volatile T> compile-error in compare_exchange_[weak/strong]() and wait()
2024-06-09 7:19 [Bug libstdc++/115402] New: std::atomic_ref<volatile T> compile-error in compare_exchange_[weak/strong]() and wait() lewissbaker.opensource at gmail dot com
` (3 preceding siblings ...)
2024-06-09 17:55 ` pinskia at gcc dot gnu.org
@ 2024-06-10 9:19 ` redi at gcc dot gnu.org
2024-06-10 9:23 ` redi at gcc dot gnu.org
2024-06-14 12:52 ` lewissbaker.opensource at gmail dot com
6 siblings, 0 replies; 8+ messages in thread
From: redi at gcc dot gnu.org @ 2024-06-10 9:19 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115402
--- Comment #5 from Jonathan Wakely <redi at gcc dot gnu.org> ---
And https://cplusplus.github.io/LWG/issue4069 too.
^ permalink raw reply [flat|nested] 8+ messages in thread
* [Bug libstdc++/115402] std::atomic_ref<volatile T> compile-error in compare_exchange_[weak/strong]() and wait()
2024-06-09 7:19 [Bug libstdc++/115402] New: std::atomic_ref<volatile T> compile-error in compare_exchange_[weak/strong]() and wait() lewissbaker.opensource at gmail dot com
` (4 preceding siblings ...)
2024-06-10 9:19 ` redi at gcc dot gnu.org
@ 2024-06-10 9:23 ` redi at gcc dot gnu.org
2024-06-14 12:52 ` lewissbaker.opensource at gmail dot com
6 siblings, 0 replies; 8+ messages in thread
From: redi at gcc dot gnu.org @ 2024-06-10 9:23 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115402
--- Comment #6 from Jonathan Wakely <redi at gcc dot gnu.org> ---
There is a paper being written to address both those issues, but it hasn't been
published yet. It should be P3323 when it's ready.
^ permalink raw reply [flat|nested] 8+ messages in thread
* [Bug libstdc++/115402] std::atomic_ref<volatile T> compile-error in compare_exchange_[weak/strong]() and wait()
2024-06-09 7:19 [Bug libstdc++/115402] New: std::atomic_ref<volatile T> compile-error in compare_exchange_[weak/strong]() and wait() lewissbaker.opensource at gmail dot com
` (5 preceding siblings ...)
2024-06-10 9:23 ` redi at gcc dot gnu.org
@ 2024-06-14 12:52 ` lewissbaker.opensource at gmail dot com
6 siblings, 0 replies; 8+ messages in thread
From: lewissbaker.opensource at gmail dot com @ 2024-06-14 12:52 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115402
--- Comment #7 from Lewis Baker <lewissbaker.opensource at gmail dot com> ---
This paper has now been published and is available at:
https://isocpp.org/files/papers/P3323R0.html
^ permalink raw reply [flat|nested] 8+ messages in thread
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2024-06-09 7:19 [Bug libstdc++/115402] New: std::atomic_ref<volatile T> compile-error in compare_exchange_[weak/strong]() and wait() lewissbaker.opensource at gmail dot com
2024-06-09 17:02 ` [Bug libstdc++/115402] " pinskia at gcc dot gnu.org
2024-06-09 17:05 ` pinskia at gcc dot gnu.org
2024-06-09 17:09 ` pinskia at gcc dot gnu.org
2024-06-09 17:55 ` pinskia at gcc dot gnu.org
2024-06-10 9:19 ` redi at gcc dot gnu.org
2024-06-10 9:23 ` redi at gcc dot gnu.org
2024-06-14 12:52 ` lewissbaker.opensource at gmail dot com
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