Difference between revisions of "cpp/atomic/atomic is lock free"
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@2@ Expands to an integer constant expression with value {{c|0}} for the built-in atomic types that are never lock-free, to {{c|1}} for the built-in atomic types that are sometimes lock-free, and to {{c|2}} for the built-in atomic types that are always lock-free. | @2@ Expands to an integer constant expression with value {{c|0}} for the built-in atomic types that are never lock-free, to {{c|1}} for the built-in atomic types that are sometimes lock-free, and to {{c|2}} for the built-in atomic types that are always lock-free. | ||
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===Parameters=== | ===Parameters=== | ||
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===Exceptions=== | ===Exceptions=== | ||
{{noexcept}} | {{noexcept}} | ||
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| + | ===Notes=== | ||
| + | All atomic types except for {{lc|std::atomic_flag}} may be implemented using mutexes or other locking operations, rather than using the lock-free atomic CPU instructions. Atomic types are also allowed to be ''sometimes'' lock-free, e.g. if only aligned memory accesses are naturally atomic on a given architecture, misaligned objects of the same type have to use locks. If the type is sometimes lock-free, then the function (1) or its member function equivalent has to be used to determine if the particular instance is lock-free. | ||
===Example=== | ===Example=== | ||
Revision as of 11:34, 17 August 2013
| Defined in header <atomic>
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| (1) | ||
| template< class Atomic > bool atomic_is_lock_free( const volatile Atomic* obj ) |
(since C++11) | |
| template< class Atomic > bool atomic_is_lock_free( const Atomic* obj ) |
(since C++11) | |
| #define ATOMIC_CHAR_LOCK_FREE /* unspecified */ #define ATOMIC_CHAR16_T_LOCK_FREE /* unspecified */ |
(2) | (since C++11) |
obj is implemented lock-free, as if by calling obj->is_lock_free()Contents |
Parameters
| obj | - | pointer to the atomic object to examine |
Return value
true if *obj is a lock-free atomic, false otherwise.
Exceptions
Notes
All atomic types except for std::atomic_flag may be implemented using mutexes or other locking operations, rather than using the lock-free atomic CPU instructions. Atomic types are also allowed to be sometimes lock-free, e.g. if only aligned memory accesses are naturally atomic on a given architecture, misaligned objects of the same type have to use locks. If the type is sometimes lock-free, then the function (1) or its member function equivalent has to be used to determine if the particular instance is lock-free.
Example
| This section is incomplete Reason: no example |
See also
| checks if the atomic object is lock-free (public member function of std::atomic<T>)
| |
| specializes atomic operations for std::shared_ptr (function template) | |
| (C++11) |
the lock-free boolean atomic type (class) |
