[foreign-preview] RFR: 8280460: MemorySegment::allocateNative should be tolerant of zero-sized allocation requests

[Jorn Vernee]

On Tue, 22 Feb 2022 13:05:57 GMT, Maurizio Cimadamore <mcimadamore at openjdk.org> wrote:

> This patch addresses the issues discussed here:
> 
> https://mail.openjdk.java.net/pipermail/panama-dev/2022-January/016071.html
> 
> And makes `MemorySegment::allocateNative` tolerand of zero-sized allocation requests. After evaluating a number of alternatives, I have decided to do what `ByteBuffer` also does, that is, always compute the size of the allocation as `max(size, 1L)`.
> 
> This means that we always perform some allocation - which works better with alignment constraints (e.g. the address you get back is aligned as per request; this is a corner case, but makes the API more consistent).
> 
> I've tweaked the javadoc to reflect that (and also added some javadoc to `SegmentAllocator` as well), and added a test for various kinds of native segments, created both safely and unsafely.

Marked as reviewed by jvernee (Committer).

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PR: https://git.openjdk.java.net/panama-foreign/pull/650