[foreign-memaccess+abi] RFR: 8265751: MemoryAddress should have a scope accessor [v3]

[Radoslaw Smogura]

On Fri, 23 Apr 2021 17:22:08 GMT, Maurizio Cimadamore <mcimadamore at openjdk.org> wrote:

>> src/jdk.incubator.foreign/share/classes/jdk/internal/foreign/MemoryAddressImpl.java line 87:
>> 
>>> 85:         if (segment != null) {
>>> 86:             if (segment.base() != null) {
>>> 87:                 throw new UnsupportedOperationException("Not a native address");
>> 
>> Maybe I'm wrong, but if I would like to deregister resource associated with this address here (I.e by calling unmap) during cleanup, will it cause exception?
>
> In general yes. Although I argue that if you get such an exception, the cleanup action is doing something suspicious. If you are referring to your allocator work, I think the trick there is to create entries that are backed by plain addresses (and where the addresses are the ones you obtain from malloc - so they have the global scope, no issue there).
> 
> But - if you find yourself in a tight spot during cleanup, you could always do:
> 
> 
> long rawAddress = address.segmentOffset(MemorySegment.globalNativeScope);
> MemoryAddress addr = MemoryAddress.ofLong(rawAddress);

Yes, I was bit scared about it and one other thing I got in mind, but I think it will work. Thank you.

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PR: https://git.openjdk.java.net/panama-foreign/pull/513