tmp/tmpjow36hz9/{from.md → to.md}
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#### General <a id="thread.lock.general">[[thread.lock.general]]</a>
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A *lock* is an object that holds a reference to a lockable object and
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may unlock the lockable object during the lock’s destruction (such as
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when leaving block scope). An execution agent may use a lock to aid in
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managing ownership of a lockable object in an exception safe manner. A
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lock is said to *own* a lockable object if it is currently managing the
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ownership of that lockable object for an execution agent. A lock does
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not manage the lifetime of the lockable object it references.
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[*Note 1*: Locks are intended to ease the burden of unlocking the
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lockable object under both normal and exceptional
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circumstances. — *end note*]
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Some lock constructors take tag types which describe what should be done
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with the lockable object during the lock’s construction.
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``` cpp
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namespace std {
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struct defer_lock_t { }; // do not acquire ownership of the mutex
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struct try_to_lock_t { }; // try to acquire ownership of the mutex
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// without blocking
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struct adopt_lock_t { }; // assume the calling thread has already
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// obtained mutex ownership and manage it
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inline constexpr defer_lock_t defer_lock { };
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inline constexpr try_to_lock_t try_to_lock { };
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inline constexpr adopt_lock_t adopt_lock { };
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}
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```
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