std::atomic<T>::is_lock_free
From cppreference.com
| bool is_lock_free() const noexcept; |
(1) | (since C++11) |
| bool is_lock_free() const volatile noexcept; |
(2) | (since C++11) |
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
Run this code
#include <atomic> #include <iostream> #include <utility> 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) |