Memory management and local GC?

[Ola Fosheim Grøstad]

On Saturday, 31 October 2020 at 19:05:43 UTC, Kagamin wrote:
> Say, allocate a dictionary, network connection or XML document 
> and put it in shared context. How do you deal with them?

Ok, so we assume @safe. When you allocate you have access to it 
as an "isolated shared" which taint all references obtained 
through it, so you cannot store references to the internals. BUT, 
you can configure it.

After you are done with the isolated configuration/usage you do a 
move operation to transfer it to a shared pointer (effectively 
encapsulating it). Then you need to obtain access to it through 
the implementation of the shared protocol for the object (not 
implemented as @safe).

So for a dictionary, where you want to store references to local 
objects you would need a dictionary written especially for shared 
access as you would need to have a borrow-pointer to keep it 
pinned in the "foreign" GC-pool. So it is up to the dictionary 
implementation to prevent multiple threads to access the same 
object at the same time. So that makes it possible to set up a 
shared cache and use it in @safe code, but the object accesses 
have to be limited somewhat.

We need to think of shared globals as facades in this model.

A network connection would probably best be implemented as a 
struct that you embed as a private field in a shared class object.

Or maybe you think about something else? I expect there to be 
pitfalls, so more feedback is good. :-)