David Abrahams wrote:
"Eric Niebler" <eric@boost-consulting.com> writes:
I continue to believe that a better interface for a unified lock involves descriptively named helper functions:
scoped_lock l1( m ); // lock unconditionally scoped_lock l1 = defer_lock( m ); // don't lock scoped_lock l2 = try_lock( m ); // try lock scoped_lock l3 = timed_lock( m, t ); // timed lock
It's just as clear as you could hope for,
I'm not convinced it is. It potentially puts information about the kind of locking being done very far from the actual call that does locking.
True, but the other design under consideration doesn't help with that. It requires two-step construction for some constructs which could result in code like: scoped_lock l( m, false ); maybe_takes_the_lock_i_dont_know( l );
and it's extensible. I feel that the single lock c'tor with a bool arg is less readable and rather inflexible.
Inflexible how?
User's can't add more constructors if they want a different locking strategy, but they can add as many helper function as they like. For instance, they could define a function that tried to take a timed_lock and logs failures. Or throws an exception. Or they could write a lock_if helper that takes a predicate. And they can do all that with simple one-step construction syntax. It's more concise and it permits the lock declaration to appear in the condition of if statements. -- Eric Niebler Boost Consulting www.boost-consulting.com