RFR: 8317819: Scope should reflect lifetime of underying resource (mainline) [v2]

[Jorn Vernee]

On Fri, 13 Oct 2023 15:39:06 GMT, Maurizio Cimadamore <mcimadamore at openjdk.org> wrote:

>> This PR is based on a port of: openjdk/panama-foreign#898
>> 
>> Some additional changes are contained in this PR:
>> 
>> * instead of using a different "always alive" scope for zero-length memory segments, we now use the global scope
>> * the javadoc for `MemorySegment::ofArray`, `MemorySegment::ofBuffer` and `SymbolLookup::loaderLookup` is tweaked to say that the scope associated to the returned segments is an automatic scope
>> * the javadoc for `MemorySegment.Scope` defines the concepts of global and automatic scope, which are then referenced in the `Arena` javadoc.
>
> Maurizio Cimadamore has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Add test

Marked as reviewed by jvernee (Reviewer).

src/java.base/share/classes/java/lang/foreign/Arena.java line 47:

> 45:  * The simplest arena is the {@linkplain Arena#global() global arena}. The global arena
> 46:  * features an <em>unbounded lifetime</em>. The scope of the global arena is the global scope.
> 47:  * As such, native segments allocated with the global arena are associated are always accessible and their backing regions

Typo?
Suggestion:

 * As such, native segments allocated with the global arena are always accessible and their backing regions

src/java.base/share/classes/java/lang/foreign/MemoryLayout.java line 463:

> 461:      * <p>
> 462:      * If the selected layout is an {@linkplain AddressLayout address layout}, calling {@link VarHandle#get(Object...)}
> 463:      * on the returned var handle will return a new memory segment. The segment is associated with a scope that is

Should this say 'global scope' as well?

src/java.base/share/classes/java/lang/foreign/MemorySegment.java line 2367:

> 2365:      * A scope models the <em>lifetime</em> of all the memory segments associated with it. That is, a memory segment
> 2366:      * cannot be accessed if its associated scope is not {@linkplain #isAlive() alive}. Scope instances can be compared
> 2367:      * for equality. That is, two scopes are considered {@linkplain #equals(Object)} if they denote the same lifetime.

missing plain text in the link tag

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PR Review: https://git.openjdk.org/jdk/pull/16183#pullrequestreview-1676868842
PR Review Comment: https://git.openjdk.org/jdk/pull/16183#discussion_r1358496679
PR Review Comment: https://git.openjdk.org/jdk/pull/16183#discussion_r1358498568
PR Review Comment: https://git.openjdk.org/jdk/pull/16183#discussion_r1358500044