[foreign-jextract] RFR: Update memory access and linker documents [v4]

[Maurizio Cimadamore]

On Thu, 25 Mar 2021 14:02:52 GMT, Jorn Vernee <jvernee at openjdk.org> wrote:

>> Maurizio Cimadamore has updated the pull request incrementally with two additional commits since the last revision:
>> 
>>  - Fix review comments
>>  - Fix section on SegmentAllocator (was containing forward-references to native method handles)
>
> doc/panama_ffi.md line 66:
> 
>> 64: MemorySegment size = MemorySegment.allocateNative(C_INT);
>> 65: MemoryAccess.setInt(size, 5);
>> 66: foo.invokeExact(42, size);
> 
> I think this should call `size.address()` to be equivalent with the C code. Also, reachability of the segment is problematic in that case, so maybe this should switch to using an explicit resource scope.

I've rewritten this section as I noted that it was referring to native method handles, which were not yet discussed. Instead I focussed on "creating a native array" as a way to demonstrate "clunkiness" of base memory access API.

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PR: https://git.openjdk.java.net/panama-foreign/pull/475