std::atomic_ref::is_always_lock_free (3) Linux Manual Page

std::atomic_ref<T>::is_always_lock_free – std::atomic_ref<T>::is_always_lock_free

Synopsis

static constexpr bool is_always_lock_free = /*implementation-defined*/;  (since C++20)

Equals true if this operations on this atomic_ref type is always lock-free and false if it is never or sometimes lock-free.
The value of this constant is consistent with the result of member function is_lock_free.

See also

             checks if the atomic_ref object is lock-free
is_lock_free (public member function)