| Summary: | std::atomic_init() undefined | ||
|---|---|---|---|
| Product: | gcc | Reporter: | Jonathan Wakely <redi> |
| Component: | libstdc++ | Assignee: | Not yet assigned to anyone <unassigned> |
| Status: | RESOLVED FIXED | ||
| Severity: | normal | Keywords: | rejects-valid |
| Priority: | P3 | ||
| Version: | 4.9.2 | ||
| Target Milestone: | 5.0 | ||
| Host: | Target: | ||
| Build: | Known to work: | ||
| Known to fail: | Last reconfirmed: | 2015-01-18 00:00:00 | |
Although atomic_init doesn't need to be atomic the simplest way to implement it is just with a relaxed store:
--- a/libstdc++-v3/include/std/atomic
+++ b/libstdc++-v3/include/std/atomic
@@ -921,11 +921,13 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
template<typename _ITp>
inline void
- atomic_init(atomic<_ITp>* __a, _ITp __i) noexcept;
+ atomic_init(atomic<_ITp>* __a, _ITp __i) noexcept
+ { __a->store(__i, memory_order_relaxed); }
template<typename _ITp>
inline void
- atomic_init(volatile atomic<_ITp>* __a, _ITp __i) noexcept;
+ atomic_init(volatile atomic<_ITp>* __a, _ITp __i) noexcept
+ { __a->store(__i, memory_order_relaxed); }
template<typename _ITp>
inline void
A better implementation would make atomic_init friend of std::atomic so it can set the private data member directly.
Testcase for 4.9 (which doesn't have the fix for PR64940 that allows std::atomic_int t o be used interchangeably with std::atomic<int>): #include <atomic> int main() { std::atomic<int> a; atomic_init(&a, 0); } Author: redi Date: Tue Jan 20 11:50:43 2015 New Revision: 219886 URL: https://gcc.gnu.org/viewcvs?rev=219886&root=gcc&view=rev Log: PR libstdc++/64658 * include/std/atomic (atomic_init): Define. * testsuite/29_atomics/atomic/64658.cc: New. Added: trunk/libstdc++-v3/testsuite/29_atomics/atomic/64658.cc Modified: trunk/libstdc++-v3/ChangeLog trunk/libstdc++-v3/include/std/atomic fixed - probably not worth backporting since noone has noticed it's missing (and these functions only really exist because of the original plan for C compatibility, in C++ you can just use the constructor) |
#include <atomic> int main() { std::atomic_int a; atomic_init(&a, 0); } $ g++ -std=c++11 at.cc In file included from at.cc:1:0: /home/jwakely/gcc/5/include/c++/5.0.0/atomic:924:5: warning: inline function ‘void std::atomic_init(std::atomic<_ITp>*, _ITp) [with _ITp = int]’ used but never defined atomic_init(atomic<_ITp>* __a, _ITp __i) noexcept; ^ /tmp/ccZgPnay.o: In function `main': /tmp/at.cc:6: undefined reference to `void std::atomic_init<int>(std::atomic<int>*, int)' collect2: error: ld returned 1 exit status