Struct with default ctor (Was: [dmd-beta] dmd 2.064 beta take 2)

[Walter Bright]

On 5/19/2013 10:35 AM, deadalnix wrote:
> On Sunday, 19 May 2013 at 13:13:07 UTC, Andrei Alexandrescu wrote:
>> No, the race condition would have stayed.
>
> That is ridiculous. non nullable would have made the bug non existent, and even
> without race condition the problem would exists. a reference is null, it
> container shared, then set to something else. You can put barriers all over the
> place to make that sequentially consistent that it wouldn't change anything and
> the bug would still arise.

I agree with Andrei that eliminating null is not going to make a race condition 
into a thread safe one. You've got a serious bug that you may succeed in hiding 
by eliminating the null, but it's still there. From your description, I suspect 
the code is suffering from the double-checked locking bug (which can appear in 
very subtle forms).


> You also never provided any convincing solution to the safety hole. We can't
> even add check only on some edges cases as D also have values types. The only
> solution we are left with that is really safe is to null check every dereference
> or give up on @safe.

Please don't make us guess what exactly you mean by this.