std::atomic::is_always_lock_free(3)

NAME
std::atomic::is_always_lock_free - std::atomic::is_always_lock_free

Synopsis
   static constexpr bool is_always_lock_free = (since C++17)
   /*implementation-defined*/;
   Equals true if this atomic type is always lock-free and false if it is never or
   sometimes lock-free.
   The value of this constant is consistent with both the macro ATOMIC_xxx_LOCK_FREE,
   where defined, with the member function is_lock_free and non-member function
   std::atomic_is_lock_free.

Notes
   There is no non-member function equivalent of this static member constant because
   non-member functions take pointers to atomic types, and therefore aren't as useful
   in constant expressions.
            Feature-test macro Value Std Feature
   __cpp_lib_atomic_is_always_lock_free 201603L (C++17) constexpr
                        atomic<T>::is_always_lock_free

See also
   is_lock_free checks if the atomic object is lock-free
                       (public member function)
   atomic_is_lock_free checks if the atomic type's operations are lock-free
   (C++11) (function template)