scopes writeup

[Samuel Audet]

Hi, Maurizio,

I see there is an "interface Resource", but it doesn't allow us to 
provide custom allocators and deallocators. How could we, for example, 
manage all resources including those that are not pointers, structs, etc 
with a single Scope? Do we need to provide a new implementation of Scope 
for each type of Resource?

Samuel

On 1/23/19 1:27 AM, Maurizio Cimadamore wrote:
> Hi,
> at the end of last year I tried coming up with a proposal [1] which 
> aimed at finding the basic concepts behind Panama scopes - I've been 
> iterating (with the help of some internal feedback) on that proposal, 
> and put it back together in a different form which, all things 
> considered, it's not too far off from where we are now.
> 
> https://cr.openjdk.java.net/~mcimadamore/panama/scopes.html
> 
> That is, we still have a Scope abstraction - memory regions are still 
> hidden under Scopes, and not part of the public API (in an attempt to 
> limit the number of concepts exposed by the API - at least for now). 
> Pointer is an immutable cursor into a memory region. Resources are just 
> things with a scope (turns out, a native library is another such thing, 
> since a native library needs a library-wide scope for allocating its own 
> globals, etc.).
> 
> On top of what we have now, this writeup pushes forward an improved 
> ownership model, as well as some discussions concerning 
> thread-confinement of scopes.
> 
> I think this tweaked API proposal has the potential of fixing the 
> current lifecycle issues, w/o making the API too complex to use. 
> Additional abstraction (such as MemoryRegion) can be added back to the 
> public API on a by need basis (e.g. provided relevant use cases).
> 
> An experimental patch implementing the proposed approach can be found here:
> 
> http://cr.openjdk.java.net/~mcimadamore/panama/scope-ownership_v2/
> 
> Comments welcome!
> 
> Maurizio
> 
> [1] - 
> https://mail.openjdk.java.net/pipermail/panama-dev/2018-December/003605.html 
> 
>