CODEWITHSUNDEEP
c++boostmutex
Guillaume Paris
Guillaume Paris

Reputation: 10537

doubt about way to lock a boost mutex

boost::recursive_mutex m;
m.lock();

versus

boost::lock_guard<boost::recursive_mutex> lock( mutex_ );

Is there an advantage to use the first Form? Does the second form only provide RAII mecanism, or are there others advantages ?

Upvotes: 2

Views: 876

Answers (2)

Luc Danton
Luc Danton

Reputation: 35459

The two forms are not equivalent in the least. Here's what's equivalent* to the second form:

boost::recursive_mutex m;
m.lock();
try {
    // ...
} catch(...) {
    m.unlock();
    throw;
}
m.unlock();

This is what you call "only" providing RAII: avoiding hideous boilerplate to provide the same level of correctness.

*: with caveats; see other answers & comments

Upvotes: 2

Captain Obvlious
Captain Obvlious

Reputation: 20083

The advantage of using lock_guard is that it will release the lock when it goes out of scope. This eliminates the need to manually release the lock and reduces the chance of forgetting to do so. 

boost::recursive_mutex mylock;

{
    boost::lock_guard<boost::recursive_mutex> lock( mylock );

    // do something

    if(false == do_something())
    {
        return; // "lock" goes out of scope and unlocks 'mylock' from it's destructor.
    }

}
// "lock" has gone out of scope and unlocked 'mylock' from it's destructor.

Upvotes: 5

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