[foreign-abi] RFR: 8253360: LibraryLookup javadoc should be clearer about how to create restricted segments

[Paul Sandoz]

On Fri, 18 Sep 2020 15:57:56 GMT, Maurizio Cimadamore <mcimadamore at openjdk.org> wrote:

> This patch adds a better description of how clients are supposed to derive segments from a lookup symbol, by stating
> the need of keeping the symbol alive via segment attachment.
> I also fixed a missing type parameter javadoc in the VaList API.

src/jdk.incubator.foreign/share/classes/jdk/incubator/foreign/LibraryLookup.java line 55:

> 53: MemorySegment errnoSegment = errno.address().asRestrictedSegment(4, errno);
> 54:  * }</pre>
> 55:  * <p>

I worry this can easily be missed. Perhaps also doc on `Symbol` itself, and maybe consider a default method
`Symbol.asRestrictedSegment`?

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PR: https://git.openjdk.java.net/panama-foreign/pull/345