std::experimental::atomic_weak_ptr<T>::compare_exchange_strong, std::experimental::atomic_weak_ptr<T>::
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bool compare_exchange_weak(
std::weak_ptr
<T>
& expected, const
std::weak_ptr
<T>
& desired,
std::memory_order success, std::memory_order failure ) noexcept ; |
(1) | |
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bool compare_exchange_weak(
std::weak_ptr
<T>
& expected, std::weak_ptr
<T>
&& desired,
std::memory_order success, std::memory_order failure ) noexcept ; |
(2) | |
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bool compare_exchange_weak(
std::weak_ptr
<T>
& expected, const
std::weak_ptr
<T>
& desired,
std::memory_order order = std::memory_order_seq_cst ) noexcept ; |
(3) | |
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bool compare_exchange_weak(
std::weak_ptr
<T>
& expected, std::weak_ptr
<T>
&& desired,
std::memory_order order = std::memory_order_seq_cst ) noexcept ; |
(4) | |
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bool compare_exchange_strong(
std::weak_ptr
<T>
& expected, const
std::weak_ptr
<T>
& desired,
std::memory_order success, std::memory_order failure ) noexcept ; |
(5) | |
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bool compare_exchange_strong(
std::weak_ptr
<T>
& expected, std::weak_ptr
<T>
&& desired,
std::memory_order success, std::memory_order failure ) noexcept ; |
(6) | |
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bool compare_exchange_strong(
std::weak_ptr
<T>
& expected, const
std::weak_ptr
<T>
& desired,
std::memory_order order = std::memory_order_seq_cst ) noexcept ; |
(7) | |
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bool compare_exchange_strong(
std::weak_ptr
<T>
& expected, std::weak_ptr
<T>
&& desired,
std::memory_order order = std::memory_order_seq_cst ) noexcept ; |
(8) | |
Atomically compares the underlying weak_ptr in *this with expected, and if they are equivalent, replaces the former with desired (performs read-modify-write operation). Otherwise, loads the actual value stored in *this into expected (performs load operation). The replacement is performed as if by the copy or move assignment operator of weak_ptr
Two weak_ptrs are equivalent if and only if they store the same pointer value and share ownership.
The memory models for the read-modify-write and load operations are success and failure respectively. For overloads (3,4,7,8), order is used for both read-modify-write and load operations, except that std::memory_order_acquire and std::memory_order_relaxed are used for the load operation if order == std::memory_order_acq_rel, or order == std::memory_order_release
The weak versions (1-4) may fail spuriously.
Parameters
| expected | - | reference to the value expected to be found in the atomic object |
| desired | - | the value to store in the atomic object if it is as expected |
| success | - | the memory synchronization ordering for the read-modify-write operation if the comparison succeeds. All values are permitted |
| failure | - | the memory synchronization ordering for the load operation if the comparison fails. Cannot be std::memory_order_release or std::memory_order_acq_rel and cannot specify stronger ordering than success |
| order | - | the memory synchronization ordering for both operations |
Return value
true if the underlying atomic value was changed, false
Remarks
All changes to the atomic_weak_ptr object itself, and all associated use_count increments, are guaranteed to be performed atomically. Associated use_count
If the compare-exchange operation return true, expected is not accessed after the atomic update step. If it returns false, expected is updated with the existing value read from the atomic_weak_ptr object in the attempted atomic update. The use_count update corresponding to the write to expected is part of the atomic operation, but the write to expected
For overloads (1,3,5,7), desired is not accessed after the atomic update step.
For overloads (2,4,6,8), desired is moved from only if the compare-exchange operation returns true
Notes
The weak forms (1-4) of the functions are allowed to fail spuriously, that is, act as if *this and expected
See also
specializes atomic operations for std::shared_ptr (function template) |