template< class T > bool atomic_is_lock_free( const std::shared_ptr<T>* p ); | (1) | (since C++11) |
template< class T > std::shared_ptr<T> atomic_load( const std::shared_ptr<T>* p ); | (2) | (since C++11) |
template< class T >
std::shared_ptr<T> atomic_load_explicit( const std::shared_ptr<T>* p,
std::memory_order mo ); | (3) | (since C++11) |
template< class T >
void atomic_store( std::shared_ptr<T>* p,
std::shared_ptr<T> r ); | (4) | (since C++11) |
template< class T >
void atomic_store_explicit( std::shared_ptr<T>* p,
std::shared_ptr<T> r,
std::memory_order mo); | (5) | (since C++11) |
template< class T >
std::shared_ptr<T> atomic_exchange( std::shared_ptr<T>* p,
std::shared_ptr<T> r); | (6) | (since C++11) |
template<class T>
std::shared_ptr<T> atomic_exchange_explicit( std::shared_ptr<T>* p,
std::shared_ptr<T> r,
std::memory_order mo); | (7) | (since C++11) |
template< class T >
bool atomic_compare_exchange_weak( std::shared_ptr<T>* p,
std::shared_ptr<T>* expected,
std::shared_ptr<T> desired); | (8) | (since C++11) |
template<class T>
bool atomic_compare_exchange_strong( std::shared_ptr<T>* p,
std::shared_ptr<T>* expected,
std::shared_ptr<T> desired); | (9) | (since C++11) |
template< class T >
bool atomic_compare_exchange_strong_explicit( std::shared_ptr<T>* p,
std::shared_ptr<T>* expected,
std::shared_ptr<T> desired,
std::memory_order success,
std::memory_order failure); | (10) | (since C++11) |
template< class T >
bool atomic_compare_exchange_weak_explicit( std::shared_ptr<T>* p,
std::shared_ptr<T>* expected,
std::shared_ptr<T> desired,
std::memory_order success,
std::memory_order failure); | (11) | (since C++11) |
If multiple threads of execution access the same std::shared_ptr object without synchronization and any of those accesses uses a non-const member function of shared_ptr then a data race will occur unless all such access is performed through these functions, which are overloads of the corresponding atomic access functions (std::atomic_load, std::atomic_store, etc.).
Note that the control block of a shared_ptr is thread-safe: different std::shared_ptr objects can be accessed using mutable operations, such as operator= or reset, simultaneously by multiple threads, even when these instances are copies, and share the same control block internally.
1) Determines whether atomic access to the shared pointer pointed-to by
p is lock-free. 2) Equivalent to
atomic_load_explicit(p, std::memory_order_seq_cst) 3) Returns the shared pointer pointed-to by
p. As with the non-specialized std::atomic_load_explicit, mo cannot be std::memory_order_release or std::memory_order_acq_rel 4) Equivalent to
atomic_store_explicit(p, r, memory_order_seq_cst) 5) Swaps the shared pointers
p and r, effectively executing p->swap(r). As with the non-specialized std::atomic_store_explicit, mo cannot be std::memory_order_acquire or std::memory_order_acq_rel 6) Equivalent to
atomic_exchange_explicit(p, r, memory_order_seq_cst) 7) Swaps the shared pointers
p and r, effectively executing p->swap(r) and returns a copy of the shared pointer formerly pointed-to by p 8) Equivalent to
atomic_compare_exchange_weak_explicit(p, expected, desired, std::memory_order_seq_cst, std::memory_order_seq_cst) 9) Equivalent to
atomic_compare_exchange_strong_explicit(p, expected, desired, std::memory_order_seq_cst, std::memory_order_seq_cst) 10) Compares the shared pointers pointed-to by
p and expected. If they are equivalent (share ownership of the same pointer and refer to the same pointer), assigns desired into *p using the memory ordering constraints specified by success and returns true. If they are not equivalent, assigns *p into *expected using the memory ordering constraints specified by failure and returns false. 11) Same as 10), but may fail spuriously.
All these functions invoke undefined behavior if p is a null pointer.
Parameters
| p, expected | - | a pointer to a std::shared_ptr |
| r, desired | - | a std::shared_ptr |
| mo, success, failure | - | memory ordering selectors of type std::memory_order |
Exceptions
These functions do not throw exceptions.
Return value
1)
true if atomic access is implemented using lock-free instructions 2,3) A copy of the pointed-to shared pointer.
4,5) (none)
6,7) A copy of the formerly pointed-to shared pointer
8,9,10,11)
true if the shared pointers were equivalent and the exchange was performed, false otherwise.Notes
The Concurrency TS offers atomic smart pointer classes atomic_shared_ptr and atomic_weak_ptr as a replacement for the use of these functions.
Example
See also
| (C++11) | checks if the atomic type's operations are lock-free (function template) |
| (C++11)(C++11) | atomically replaces the value of the atomic object with a non-atomic argument (function template) |
| (C++11)(C++11) | atomically obtains the value stored in an atomic object (function template) |
| (C++11)(C++11) | atomically replaces the value of the atomic object with non-atomic argument and returns the old value of the atomic (function template) |
| atomically compares the value of the atomic object with non-atomic argument and performs atomic exchange if equal or atomic load if not (function template) |
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