RFR: 8307181: MemoryLayout.structLayout uses undocumented strict alignment constraints

[Jorn Vernee]

On Wed, 3 May 2023 08:31:34 GMT, Maurizio Cimadamore <mcimadamore at openjdk.org> wrote:

> This patch adds documentation for the behavior of the `MemoryLayout::structLayout` factory.
> 
> This factory throws an `IllegalArgumentException` if one of the member layouts passed to it occurs at an offset within the struct that is not aligned.
> 
> As part of this patch, I've also added some api notes on how to use this factory when unaligned elements are present.

Nice api note!

src/java.base/share/classes/java/lang/foreign/MemoryLayout.java line 743:

> 741:      * overflows.
> 742:      * @throws IllegalArgumentException if a member layouts in {@code elements} occurs at an offset (relative to the start
> 743:      * of the struct layout) which is not compatible with its alignment constraint.

Suggestion:

     * @throws IllegalArgumentException if a member layout in {@code elements} occurs at an offset (relative to the start
     * of the struct layout) which is not compatible with its alignment constraint.

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Marked as reviewed by jvernee (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/13770#pullrequestreview-1411008792
PR Review Comment: https://git.openjdk.org/jdk/pull/13770#discussion_r1183756362