RFR: 8277924: Small tweaks to foreign function and memory API

[Jorn Vernee]

On Mon, 29 Nov 2021 11:22:45 GMT, Maurizio Cimadamore <mcimadamore at openjdk.org> wrote:

> Following integration of the second incubator of the foreign function and memory API [1], we detected few divergences between the contents of the jdk repo and the panama repo:
> 
> * the name of some of the `FunctionDescriptor` wither methods is different (e.g. `withAppendedLayoutArguments` vs. `appendLayoutArguments`), as it has been simplified and improved following a change that was not incorporated in [1].
> 
> * TestUpcall does not execute all the test combinations, because of an issue in the jtreg header (also fixed in the panama repo)
> 
> * Addressing some feedback, we would like to bring back alignment to JAVA_INT layout constants (and related constants). 
> 
> Javadoc: http://cr.openjdk.java.net/~mcimadamore/8277924/v1/javadoc/jdk/incubator/foreign/package-summary.html
> Specdiff: http://cr.openjdk.java.net/~mcimadamore/8277924/v1/spec_diff/overview-summary.html
> 
> [1] - #5907

Marked as reviewed by jvernee (Reviewer).

src/jdk.incubator.foreign/share/classes/jdk/incubator/foreign/FunctionDescriptor.java line 134:

> 132:      * layout array of this function descriptor.
> 133:      * @param index the index at which to insert the arguments
> 134:      * @param addedLayouts the argument layouts to append.

Suggestion:

     * @param addedLayouts the argument layouts to insert.

src/jdk.incubator.foreign/share/classes/jdk/incubator/foreign/ValueLayout.java line 205:

> 203: 
> 204:     static final int ALIGNED_POS = 0;
> 205:     static final int UNALIGNED_POS = 1;

Suggestion:

    private static final int ALIGNED_POS = 0;
    private static final int UNALIGNED_POS = 1;

src/jdk.incubator.foreign/share/classes/jdk/internal/foreign/Utils.java line 179:

> 177: 
> 178:     @Stable
> 179:     public static LayoutAccess LAYOUT_ACCESS;

Clever :) Maybe some comment here about what this is doing would be nice (I had to look at it for a while).
Suggestion:

    public static LayoutAccess LAYOUT_ACCESS; // shared secret


Alternatively, I think you could do this with a MethodHandle acquired through `Lookup.privateLookupIn(lookup(), ValueLayout.class).findVirtual(...)`.

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PR: https://git.openjdk.java.net/jdk/pull/6589