std::atomic<T>::is_lock_free
(since C++11) | ||
bool is_lock_free() const noexcept; | ||
bool is_lock_free() const volatile noexcept; |
Checks whether the atomic operations on all objects of this type are lock-free.
Parameters
(none).
Return value
true
if the atomic operations on the objects of this type are lock-free, false
otherwise.
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.
The C++ standard recommends (but does not require) that lock-free atomic operations are also address-free, that is, suitable for communication between processes using shared memory.
Example
#include <iostream> #include <utility> #include <atomic> struct A { int a[100]; }; struct B { int x, y; }; int main() { std::cout << std::boolalpha << "std::atomic<A> is lock free? " << std::atomic<A>{}.is_lock_free() << '\n' << "std::atomic<B> is lock free? " << std::atomic<B>{}.is_lock_free() << '\n'; }
Possible output:
std::atomic<A> is lock free? false std::atomic<B> is lock free? true
See also
(C++11) | checks if the atomic type's operations are lock-free (function template) |
specializes atomic operations for std::shared_ptr (function template) |
|
[static] (C++17) | indicates that the type is always lock-free (public static member constant) |
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