boost::lock_guard vs boost::mutex::scoped_lock

Question

Which is preferred boost::lock_guard or boost::mutex::scoped_lock?

I'm using Boost.Thread with the hope to move to C++11 threading when it becomes available.

Is scoped_lock part of the next c++ standard?

Are the any advantages to prefer one over the other?

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NOTE: I'm aware that scoped_lock is just a typedef of lock_guard.

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edit: I was wrong scoped_lock is not a typedef of lock_guard. It's a typedef of unique_lock.

Answer 1

Amit is right: boost::mutex::scoped_lock is a typedef for boost::unique_lock<boost::mutex>, not lock_guard. scoped_lock is not available in C++0x.

Unless you need the flexibility of unique_lock, I would use lock_guard. It is simpler, and more clearly expresses the intent to limit the lock to a defined scope.

Answer 2

Not much difference between the two. As per Boost, scoped_lock is a typedef for unique_lock<mutex>. Both of unique_lock and lock_guard implement RAII-style locking. The difference between is simply that unique_lock has a more complex interface -- it allows to defer lock and call unlock.