if (X !is null && X.Y !is null) access crash

[Steven Schveighoffer]

On 6/8/19 2:28 AM, Amex wrote:
> On Friday, 7 June 2019 at 16:09:47 UTC, Adam D. Ruppe wrote:
>>> It happens when I close down my app.
>>
>> is this inside a destructor?
> 
> No, it's in an external thread(it is in a callback). All I can think of 
> is that something is happening in between the two checks since there is 
> no way it could happen otherwise.
> 
> 
> 

Possible the GC cleaned up the object already. When this happens, you 
get this kind of behavior (the GC intentionally sets the vtable to null 
to prevent invalid access).

Try GC.addRef on the X reference, and see if it helps.

-Steve