Re: Reference counter in smart pointers are not updated properly when used by multiple tasks

["Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>]

On 01/02/2018 06:52, onox wrote:

> So the smart pointers are not working properly when there are jobs (paired with the same
> smart pointer) being executed by multiple workers.

Depends on the implementation. Surely handling reference counts must be 
done in a task-safe manner, e.g. through a protected action. Pragma 
Atomic is no help here.

> I'm not sure if this is a bug in my
> own code or whether GNAT is doing something funky in the Finalize procedure.

I never had problems with that.

> Can someone provide some insight?

1. I have two implementations, one with heavy logging/tracing the 
actions taken on reference counts.

2. There is gnatmem, which works surprisingly good. Reference-counted 
objects are allocated in the pool, so most of bugs are also memory leaks.

3. Controlled objects are tagged and thus passed by reference. It is 
important to remember when passing controlled handles/smart pointers 
around. A usual schema for dealing with shared linked structures like 
graphs is to clone its parts when updated under concurrent access. The 
case is detected using the reference count value > n, where n is the 
number of "owned" references. That n depends on parameter passing 
mechanism, which is, as I said, by-reference.

-- 
Regards,
Dmitry A. Kazakov
http://www.dmitry-kazakov.de