33 Concurrency support library [thread]

33.2 Requirements [thread.req]

33.2.5 Requirements for Cpp17Lockable types [thread.req.lockable] Cpp17Lockable requirements [thread.req.lockable.req]

A type L meets the Cpp17Lockable requirements if it meets the Cpp17BasicLockable requirements and the following expressions are well-formed and have the specified semantics (m denotes a value of type L).
Effects: Attempts to acquire a lock for the current execution agent without blocking.
If an exception is thrown then a lock shall not have been acquired for the current execution agent.
Return type: bool.
Returns: true if the lock was acquired, otherwise false.