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Asked: 2026-06-15T23:16:03+00:00

It seems that BasicLockable concept is enough for lock_guard, but in the standard draft(N3242),

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It seems that BasicLockable concept is enough for lock_guard, but in the standard draft(N3242), Lockable is required for the Mutex template parameter. Any reason ?

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  1. Editorial Team

    In n3290 (§30.4.2.1[thread.lock.guard]/1), it says,

    An object of type lock_guard controls the ownership of a lockable object within a scope. A lock_guard object maintains ownership of a lockable object throughout the lock_guard object’s lifetime (3.8). The behavior of a program is undefined if the lockable object referenced by pm does not exist for the entire lifetime of the lock_guard object. The supplied Mutex type shall meet the BasicLockable requirements (30.2.5.2).

    The 2nd paragraph in n3242 is probably an editorial error. This is library defect 2023: Incorrect requirements for lock_guard and unique_lock, and the paragraph is removed in n3290, as shown in n3278: Recent Concurrency Issue Resolutions

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