[foreign-abi] RFR: 8249803: Add LibraryLookup.Symbol

[Jorn Vernee]

On Tue, 21 Jul 2020 14:42:11 GMT, Maurizio Cimadamore <mcimadamore at openjdk.org> wrote:

> This patch adds the LibraryLookup.Symbol, which implements Addressable, and that is returned on a successful symbol
> lookup. This patch also tweaks VaList to also implement the Addressable interface (VaList already had an `address()`
> method).  The `ForeignLinker::downcallHandle` method has been tweaked to accept an Addressable as a function entry
> point. This allows downcall handle to target not only native symbols, but also upcall stubs (since upcall stubs are
> segments, which are addressable) as well as native memory addresses.  Some tests needed minor tweaks.

src/jdk.incubator.foreign/share/classes/jdk/internal/foreign/abi/ProgrammableInvoker.java line 116:

> 115:
> 116:         this.addr = addr.address();
> 117:         this.callingSequence = callingSequence;

Don't think this will keep the reference to the LibraryLookup alive. I think you need to save the Addressable, and then
convert to MA on demand, or use 2 fields (or maybe you have a better idea).

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PR: https://git.openjdk.java.net/panama-foreign/pull/256