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* [Bug c++/60695] New: std::atomic<X> doesn't work when X is of zero size
@ 2014-03-28 12:54 roman at binarylife dot net
2014-03-28 13:11 ` [Bug c++/60695] " redi at gcc dot gnu.org
` (5 more replies)
0 siblings, 6 replies; 7+ messages in thread
From: roman at binarylife dot net @ 2014-03-28 12:54 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60695
Bug ID: 60695
Summary: std::atomic<X> doesn't work when X is of zero size
Product: gcc
Version: unknown
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: roman at binarylife dot net
$ cat test.cc
#include <atomic>
struct X {
char stuff[0];
};
X foo(std::atomic<X>& a, X x) {
a = x;
return a;
}
$ g++ -std=c++11 -c test.cc
In file included from test.cc:1:0:
/home/abend/local/gcc-4.9/include/c++/4.9.0/atomic: In instantiation of ‘void
std::atomic<_Tp>::store(_Tp, std::memory_order) [with _Tp = X;
std::memory_order = std::memory_order]’:
/home/abend/local/gcc-4.9/include/c++/4.9.0/atomic:183:18: required from ‘_Tp
std::atomic<_Tp>::operator=(_Tp) [with _Tp = X]’
test.cc:8:5: required from here
/home/abend/local/gcc-4.9/include/c++/4.9.0/atomic:199:39: error: argument 1 of
‘__atomic_store’ must be a pointer to a nonzero size object
{ __atomic_store(&_M_i, &__i, _m); }
^
/home/abend/local/gcc-4.9/include/c++/4.9.0/atomic: In instantiation of ‘_Tp
std::atomic<_Tp>::load(std::memory_order) const [with _Tp = X;
std::memory_order = std::memory_order]’:
/home/abend/local/gcc-4.9/include/c++/4.9.0/atomic:176:21: required from
‘std::atomic<_Tp>::operator _Tp() const [with _Tp = X]’
test.cc:9:10: required from here
/home/abend/local/gcc-4.9/include/c++/4.9.0/atomic:209:31: error: argument 1 of
‘__atomic_load’ must be a pointer to a nonzero size object
__atomic_load(&_M_i, &tmp, _m);
^
$ g++ --version
g++ (GCC) 4.9.0 20140327 (experimental)
...
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From: "burnus at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug fortran/60677] [4.9 Regression] FAIL: gfortran.dg/ichar_3.f90 -O (test for excess errors)
Date: Fri, 28 Mar 2014 13:02:00 -0000
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http://gcc.gnu.org/bugzilla/show_bug.cgi?id`677
--- Comment #2 from Tobias Burnus <burnus at gcc dot gnu.org> ---
*** Bug 60678 has been marked as a duplicate of this bug. ***
^ permalink raw reply [flat|nested] 7+ messages in thread
* [Bug c++/60695] std::atomic<X> doesn't work when X is of zero size
2014-03-28 12:54 [Bug c++/60695] New: std::atomic<X> doesn't work when X is of zero size roman at binarylife dot net
@ 2014-03-28 13:11 ` redi at gcc dot gnu.org
2014-03-28 13:26 ` [Bug libstdc++/60695] " redi at gcc dot gnu.org
` (4 subsequent siblings)
5 siblings, 0 replies; 7+ messages in thread
From: redi at gcc dot gnu.org @ 2014-03-28 13:11 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60695
--- Comment #1 from Jonathan Wakely <redi at gcc dot gnu.org> ---
That type isn't valid in ISO C++ and I don't see how you can usefully use it as
an atomic object, so I don't think this failure matters.
My preference would be to add this to std::atomic<_Tp>:
static_assert( sizeof(_Tp) > 0, "Don't be silly" );
^ permalink raw reply [flat|nested] 7+ messages in thread
* [Bug libstdc++/60695] std::atomic<X> doesn't work when X is of zero size
2014-03-28 12:54 [Bug c++/60695] New: std::atomic<X> doesn't work when X is of zero size roman at binarylife dot net
2014-03-28 13:11 ` [Bug c++/60695] " redi at gcc dot gnu.org
@ 2014-03-28 13:26 ` redi at gcc dot gnu.org
2014-03-28 13:36 ` roman at binarylife dot net
` (3 subsequent siblings)
5 siblings, 0 replies; 7+ messages in thread
From: redi at gcc dot gnu.org @ 2014-03-28 13:26 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60695
Jonathan Wakely <redi at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |ASSIGNED
Last reconfirmed| |2014-03-28
Component|c++ |libstdc++
Assignee|unassigned at gcc dot gnu.org |redi at gcc dot gnu.org
Ever confirmed|0 |1
Severity|normal |enhancement
--- Comment #2 from Jonathan Wakely <redi at gcc dot gnu.org> ---
I'll add that assertion in the library.
^ permalink raw reply [flat|nested] 7+ messages in thread
* [Bug libstdc++/60695] std::atomic<X> doesn't work when X is of zero size
2014-03-28 12:54 [Bug c++/60695] New: std::atomic<X> doesn't work when X is of zero size roman at binarylife dot net
2014-03-28 13:11 ` [Bug c++/60695] " redi at gcc dot gnu.org
2014-03-28 13:26 ` [Bug libstdc++/60695] " redi at gcc dot gnu.org
@ 2014-03-28 13:36 ` roman at binarylife dot net
2014-03-28 17:27 ` redi at gcc dot gnu.org
` (2 subsequent siblings)
5 siblings, 0 replies; 7+ messages in thread
From: roman at binarylife dot net @ 2014-03-28 13:36 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60695
--- Comment #3 from Roman Kononov <roman at binarylife dot net> ---
Yes, it is definitely silly in some sense. But, some templated user code might
become more complex with this behaviour. If gcc supports zero-sized objects it
would be nice to support them fully. The implementation for this case might do
the synchronization part without any data exchange.
^ permalink raw reply [flat|nested] 7+ messages in thread
* [Bug libstdc++/60695] std::atomic<X> doesn't work when X is of zero size
2014-03-28 12:54 [Bug c++/60695] New: std::atomic<X> doesn't work when X is of zero size roman at binarylife dot net
` (2 preceding siblings ...)
2014-03-28 13:36 ` roman at binarylife dot net
@ 2014-03-28 17:27 ` redi at gcc dot gnu.org
2014-04-15 13:48 ` redi at gcc dot gnu.org
2014-04-15 14:07 ` redi at gcc dot gnu.org
5 siblings, 0 replies; 7+ messages in thread
From: redi at gcc dot gnu.org @ 2014-03-28 17:27 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60695
--- Comment #4 from Jonathan Wakely <redi at gcc dot gnu.org> ---
I don't buy it. That zero-size struct type has very limited uses, it's not the
sort of type you use like other value types, and I can't imagine any scenario
where that type is useful where you're also storing generic types in
std::atomic.
I don't want to complicate the implementation even if someone thinks of an
obscure hypothetical use case.
^ permalink raw reply [flat|nested] 7+ messages in thread
* [Bug libstdc++/60695] std::atomic<X> doesn't work when X is of zero size
2014-03-28 12:54 [Bug c++/60695] New: std::atomic<X> doesn't work when X is of zero size roman at binarylife dot net
` (3 preceding siblings ...)
2014-03-28 17:27 ` redi at gcc dot gnu.org
@ 2014-04-15 13:48 ` redi at gcc dot gnu.org
2014-04-15 14:07 ` redi at gcc dot gnu.org
5 siblings, 0 replies; 7+ messages in thread
From: redi at gcc dot gnu.org @ 2014-04-15 13:48 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60695
--- Comment #5 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Author: redi
Date: Tue Apr 15 13:48:07 2014
New Revision: 209418
URL: http://gcc.gnu.org/viewcvs?rev=209418&root=gcc&view=rev
Log:
PR libstdc++/60695
* include/std/atomic (atomic<_Tp>): Add static assertion.
* testsuite/29_atomics/atomic/60695.cc: New.
Added:
trunk/libstdc++-v3/testsuite/29_atomics/atomic/60695.cc
Modified:
trunk/libstdc++-v3/ChangeLog
trunk/libstdc++-v3/include/std/atomic
^ permalink raw reply [flat|nested] 7+ messages in thread
* [Bug libstdc++/60695] std::atomic<X> doesn't work when X is of zero size
2014-03-28 12:54 [Bug c++/60695] New: std::atomic<X> doesn't work when X is of zero size roman at binarylife dot net
` (4 preceding siblings ...)
2014-04-15 13:48 ` redi at gcc dot gnu.org
@ 2014-04-15 14:07 ` redi at gcc dot gnu.org
5 siblings, 0 replies; 7+ messages in thread
From: redi at gcc dot gnu.org @ 2014-04-15 14:07 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60695
Jonathan Wakely <redi at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|ASSIGNED |RESOLVED
Resolution|--- |FIXED
Target Milestone|--- |4.10.0
--- Comment #6 from Jonathan Wakely <redi at gcc dot gnu.org> ---
fixed
^ permalink raw reply [flat|nested] 7+ messages in thread
end of thread, other threads:[~2014-04-15 14:07 UTC | newest]
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2014-03-28 12:54 [Bug c++/60695] New: std::atomic<X> doesn't work when X is of zero size roman at binarylife dot net
2014-03-28 13:11 ` [Bug c++/60695] " redi at gcc dot gnu.org
2014-03-28 13:26 ` [Bug libstdc++/60695] " redi at gcc dot gnu.org
2014-03-28 13:36 ` roman at binarylife dot net
2014-03-28 17:27 ` redi at gcc dot gnu.org
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