is(Mutex == shared) == false?

[Stanislav Blinov]

Ditto for other core.sync primitives.

This has been haunting me for a while now. Currently all those 
guys are not qualified shared at all. What that means is that we 
cannot use them in any shared classes:

shared class C
{
     Mutex m;

     this()
     {
         m = new Mutex; // error, cannot implicitly convert Mutex 
to shared(Mutex)
         m = new shared Mutex; // error, Mutex.this is not 
callable using a shared object
     }
}

Same goes for shared methods too. So the only possible ways to 
use Mutex et al. are to either declare them __gshared, which 
implies static, or apply casts. So we can't have per-instance 
mutexes, condition variables, etc, unless using casts everywhere.

As far as I can see this state is the same between dmd, ldc and 
gdc.

So, question number 1:

Is this at all intentional or just inherent and no one got around 
to adding support for shared? I can't at all see why would they 
be non-shared.

Because if that is to change, it'd better be sooner than later, 
right?

With mutexes the roots run as deep as object_.{d,di} where the 
Monitor interface is declared (having both lock and unlock 
methods non-shared).

I've been able to coerce my local pull of druntime to define 
Mutex et al. as shared by default. Aside from sorcery with casts 
inside e.g. src/gc/gc.d and combating segfaults in GC and Thread 
initialization, it involved:

- qualifying Monitor's methods as shared
- renaming existing classes (e.g. class Mutex -> shared class 
Mutex_)
- providing default-shared aliases (e.g. alias Mutex = 
shared(Mutex))

The renaming and alias are needed to (a) not break existing code 
and (b) because in my understanding they should be shared anyway 
:)

Surprisingly, this didn't take all that long, though I suspect 
there are some underwater rocks still remaining. But at least 
both druntime and Phobos pass their unittests.

Thus, question number 2:

Am I going in the right direction, or is there something already 
planned regarding this?

The complete set of changes would be rather large, as not only it 
spans currently supported OSs, but I imagine also would concern 
both druntime and Phobos (e.g. std.concurrency, std.parallelism).

I am primarily on Linux, but given time I can also edit the 
relevant files for Windows too. However, I don't have access to 
any other OSs, so I still won't be able to create a complete pull 
request.

Hence, question number 3:

Provided you've read to this point, and question number 2 yields 
positive answer, is there anybody willing to collaborate on this? 
E.g. complete/test the changes on Windows, OSX, etc?

I understand that the community is currently battling in the 
fields of GC vs ARC vs manual memory management, but I still hope 
to hear your feedback :)