RFC: reference counted Throwable

[Andrei Alexandrescu via Digitalmars-d]

On 9/21/14, 1:51 AM, Jacob Carlborg wrote:
> On 2014-09-20 18:56, Andrei Alexandrescu wrote:
>
>> Please don't take me in a court of law. But yes, I am talking about the
>> compiler inserting calls to increment and decrement reference counts. --
>> Andrei
>
> We do need to know what you're proposal is for.

The title is an incomplete summary. Exceptions would be transparently 
reference counted. I.e. no changes in user code.

A little more detail on a design Walter has put together: define a new 
root class RCObject. Neither Object nor RCObject inherit each other. All 
classes that inherit RCObject are detected by the compiler as reference 
counted.

(For practical reasons, RCObject will implement IUnknown. There are a 
few random consequences of that (meaningless method QueryInterface, no 
class info, no monitor, COM-compatible layout) but IUnknown already has 
AddRef and Release and the compiler already recognizes IUnknown as a 
special case. Hooking RCObject there will leave us with two roots 
instead of adding a third one.)

Throwable will inherit RCObject. The compiler inserts AddRef and Release 
whenever copying RCObject (and derivatives) references around, of course 
following a null check.

The caveats discussed previously in http://goo.gl/Xl5U3z do apply.


Andrei