DIP 1018--The Copy Constructor--Community Review Round 1

[RazvanN]

On Saturday, 22 December 2018 at 14:43:46 UTC, 12345swordy wrote:
> On Saturday, 22 December 2018 at 09:07:52 UTC, Boris-Barboris 
> wrote:
>> On Saturday, 22 December 2018 at 02:02:55 UTC, Nicholas Wilson 
>> wrote:
>>> On Saturday, 22 December 2018 at 00:08:51 UTC, Boris-Barboris 
>>> wrote:
>>>
>>> One of the primary use cases for this is ref-counting stuff, 
>>> the refcount needs to be mutable.
>>
>> I thought ref-counted stuff is perfectly fine with postblits, 
>> was I wrong?
>
> Nope, it turns out you can't implement ref-counting GC with 
> postbilts. Andrei have tried to do this already and failed. 
> That why they are introducing it, (and why it should be covered 
> in the motivation section in the DIP).

The motivation section, although it does not link to the RC GC, 
it describes the problems encountered when trying to implement 
it. The main problem was the fact that when dealing with 
immutable fields, after the blitting phase is done it is not 
obvious in  what state the immutable fields is (raw/cooked?).