DIP18: Non-GC threads

[Piotr Szturmaj]

Michel Fortin wrote:
>> If some of the function's arguments take references (directly or
>> indirectly), then all of them are automatically added to the list of
>> GC roots (addRoot()).
>
> You still have a problem: you might have added an object passed as an
> argument to the GC roots, preventing the GC from collecting it, but if
> any thread is allowed to mutate a pointer inside this object pointing to
> some other data, using this other data in your thread is not safe,
> unless you have added a root for this other pointer too. You'd have to
> recursively add roots for this to work.
>
> There's also the same issue with global variables, the ones which are
> pointers to other pointers.

Yes, there is no obvious solution, but I think it could be done. For 
example non-immutable references may be disallowed at all. The other 
solution is to copy the whole referenced object using malloc, and add it 
to the GC roots.