On Sunday, 19 May 2013 at 22:32:58 UTC, Andrei Alexandrescu wrote:
How was there a bug if everything was properly synchronized? You either describe the matter with sufficient detail, or acknowledge the destruction of your anecdote. This is going nowhere.
I explained over and over. A field is initialized to null, while the object lock is owned, and later to its value, while it is locked. In the meantime, another thread access the object, owning the lock, assuming the field is always initialized.
The exact same problem arise quite often in the single threaded world : a reference is set to null, the dev try to be clever when initializing it, in a rare case it isn't, and everything blows up when it occurs.
It is simply easier to reproduce when things are single threaded, and are often quickly debugged in that case.
As explained, the multithreaded environment makes it super hard to debug, not the primary cause of the issue. The simply consistent in moving the initialization where it was set to null in the first place.
It is an instance of the very classic something may be null and code use it assuming it is never null.
