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Subject: Re: [Boost-users] question about threading library
From: Anthony Williams (anthony.ajw_at_[hidden])
Date: 2008-11-07 04:38:32

"Robert Ramey" <ramey_at_[hidden]> writes:

> I want to use the boost threading library in an application.
> Looking through the documentation, I have a questions.
> a) in the examples I find "boost::mutex::scoped_lock" but
> I don't find this in the documentation. It looks like this
> is called "lock_guard". What should I be doing here.

boost::mutex::scoped_lock is provided for backwards compatibility. It
is a typedef for boost::unique_lock<boost::mutex>.

I suggest using lock_guard unless you need backwards compatibility
with boost 1.34 or earlier, or need the flexibility provided by

> b) Its not clear to me how unique_lock(Lockable l)
> is different than using lock_gard(..) or scoped_lock.

lock_guard is a lightweight wrapper that *always* owns the lock. It is
not movable, and doesn't support try_lock, timed locks or

unique_lock is a more fully-featured lock owner. It supports the full
Lockable interface (including try_lock and timed_lock), so you can
pass it to boost::lock. Ownership can be transferred between
unique_lock instances, and a given instance may or may not have an
associated mutex, and may or may not own the lock on its mutex.

You can also use unique_lock with condition variables, which you can't
do with lock_guard.

scoped_lock is just a typedef to unique_lock in most cases.


Anthony Williams
Author of C++ Concurrency in Action |
Custom Software Development |
Just Software Solutions Ltd, Registered in England, Company Number 5478976.
Registered Office: 15 Carrallack Mews, St Just, Cornwall, TR19 7UL, UK

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