std::atomic_ref<T>::is_lock_free
From cppreference.com
                    
                                        
                    < cpp | atomic | atomic ref
                    
                                                            
                    |   bool is_lock_free() const noexcept;  | 
(since C++20) | |
Checks whether the atomic operations on this object are lock-free.
Parameters
(none)
Return value
true if the atomic operations on this object 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
| This section is incomplete Reason: no example  | 
See also
|    [static]  | 
   indicates that the type is always lock-free  (public static member constant)  |