synchronized (this[.classinfo]) in druntime and phobos

[Jonathan M Davis]

On Wednesday, May 30, 2012 00:01:49 Alex Rønne Petersen wrote:
> Besides, it seems to me that D can't quite make up its mind. We have TLS
> by default, and we encourage message-passing (through a library
> mechanism), and then we have the synchronized statement and attribute.
> It just seems so incredibly inconsistent. synchronized encourages doing
> the wrong thing (locks and synchronization).

It allows multiple approaches at multiple levels. TLS and message passing is 
the preferred way, and shared combined with synchronized or mutexes to protect 
it is available when you need it. synchronized classes are more 
straightforward approach to locking when you need to protect an entire object 
(and less error-prone in some respects, because you then have the guarantee 
that it happens for all functions and don't run the risk of not locking in 
some functions; it also works with inheritance that way, unlike mutexes). 
sychronized blocks on the other hand are a quick and easy way to protect 
specific sections of code without having to bother creating mutexes for it. And 
mutexes are available when you need full control. Which approach you go with 
depends on what you're doing and what your needs are.

Now, I could definitely see an argument that using shared is more low level and 
that it would be just simpler to only have mutexes and no synchronized, but we 
ended up with a more tiered approach, and that's not all bad. Each approach 
has its advantages and disadvantages, and D gives you all of them, so you can 
pick and choose what works best for you.

- Jonathan M Davis