A Refcounted Array Type

[Steven Schveighoffer via Digitalmars-d]

On 2/24/15 3:34 PM, Walter Bright wrote:
> On 2/24/2015 6:56 AM, Steven Schveighoffer wrote:
>> Actually, RCArray can never be allocated on GC, or you may corrupt
>> memory. count
>> may be non-null, and point at invalid memory when the dtor is called.
>
> Just set count to null after the delete.

No, the GC may have already deallocated the memory count points at, and 
count is still non-null.

This is why you can never refer to GC-allocated memory in dtors, if they 
can be called from the GC.

>> Only safe way to do this is to C malloc/free the count. And yes, at
>> that point,
>> you need atomics.
>
> No, RCArray is not intended for shared access between threads.

GC is what shares the access. For instance, if you have an RCArray in 
one object that is being collected, it will attempt to decrement count. 
However, that doesn't mean that another RCArray reference in the 
originating thread won't also be trying to adjust count. In reality, 
it's only shared between the GC-collection running thread and the 
originating thread. I was not talking at all about making RCArray 
shared-usable.

As talked about before, running dtors in the originating thread can 
solve this problem.

-Steve