RFR: 8295044: Implementation of Foreign Function and Memory API (Second Preview) [v6]

[Paul Sandoz]

On Mon, 7 Nov 2022 15:00:02 GMT, Maurizio Cimadamore <mcimadamore at openjdk.org> wrote:

>> This PR contains the API and implementation changes for JEP-434 [1]. A more detailed description of such changes, to avoid repetitions during the review process, is included as a separate comment.
>> 
>> [1] - https://openjdk.org/jeps/434
>
> Maurizio Cimadamore has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Make memory session a pure lifetime abstraction

src/java.base/share/classes/java/lang/foreign/Arena.java line 37:

> 35:  * This session is created with the arena, and is closed when the arena is {@linkplain #close() closed}.
> 36:  * Furthermore, all the native segments {@linkplain #allocate(long, long) allocated} by the arena are associated
> 37:  * with that session.

I think we can simplify the wording by saying an arena has a session:
Suggestion:

 * An arena is a {@linkplain AutoCloseable closeable} segment allocator that has a {@link #session() memory session}.
 * The arena's session is created when the arena is created, and is closed when the arena is {@linkplain #close() closed}.
 * All native segments {@linkplain #allocate(long, long) allocated} by the arena are associated
 * with its session.

src/java.base/share/classes/java/lang/foreign/Arena.java line 65:

> 63:      * The {@link MemorySegment#address()} of the returned memory segment is the starting address of the
> 64:      * allocated off-heap memory region backing the segment. Moreover, the {@linkplain MemorySegment#address() address}
> 65:      * of the returned segment is aligned according the provided alignment constraint.

Suggestion:

    /**
     * Creates a native memory segment with the given size (in bytes) and alignment constraint (in bytes).
     * The returned segment is associated with the arena's memory session.
     * The segment's {@link MemorySegment#address() address} is the starting address of the
     * allocated off-heap memory region backing the segment, and the address is 
     * aligned according the provided alignment constraint.

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PR: https://git.openjdk.org/jdk/pull/10872