More radical ideas about gc and reference counting

[Andrei Alexandrescu via Digitalmars-d]

On 5/1/14, 3:17 PM, H. S. Teoh via Digitalmars-d wrote:
> On Thu, May 01, 2014 at 02:29:22PM -0700, Andrei Alexandrescu via Digitalmars-d wrote:
>> On 5/1/14, 1:19 PM, H. S. Teoh via Digitalmars-d wrote:
>>> On Thu, May 01, 2014 at 01:03:06PM -0700, Andrei Alexandrescu via Digitalmars-d wrote:
>>>> On 5/1/14, 12:52 PM, "Nordlöw" wrote:
>>>>>>> into a class. I'm inclined to say that we should outright
>>>>>>> prohibit that,
>>>>>>
>>>>>> That can't happen.
>>>>>
>>>>> Why is that?
>>>>
>>>> (1) Too much breakage, (2) would disallow a ton of correct code, (3)
>>>> no reasonable alternative to propose. We'd essentially hang our
>>>> users out to dry. -- Andrei
>>>
>>> Isn't this what we're already doing by (eventually) getting rid of
>>> class dtors?
>>
>> Not even close. (1) A lot less breakage, (2) disallowed code was
>> already not guaranteed to work, (3) reasonable alternatives exist.
> [...]
>
> Argh, I feel like this discussion is going in circles. Do I really have
> to spell everything out just to make my point?
>
> 1) Today, a struct with a dtor will have the dtor invoked when the
> struct goes out of scope.
>
> 2) Today, the language allows you to put such a struct in a class as a
> member variable.
>
> 3) Today, the struct dtor of the class member will get invoked when the
> class dtor is invoked.
>
> 4) Andrei is proposing to deprecate class dtors, meaning that at some
> point they will no longer exist.
>
> 5) When that day comes, class dtors will no longer exist.
>
> 6) Since class dtors were the only thing that cleaned up the struct
> member variables by invoking their dtors, that means the struct dtor
> will *never* get invoked.
>
> Since the struct dtor will *never* get invoked, it makes no sense to
> define one in the first place.

Here's where the point derails. A struct may be preexisting; the 
decision to define a destructor for it and the decision to use 
polymorphism for an object that needs that structure are most of the 
time distinct.

Andrei