On Thu, 10 Jul 2025 23:40:15 GMT, Chen Liang <li...@openjdk.org> wrote:
> On 32 bit platforms, when an access to long/double is aligned, it is > supported but not atomic. The original wording in > `MethodHandles::byteBufferViewVarHandle` sounds as if it is not supported at > all. We can fix that by borrowing the improved specification from > `MemoryLayout::varHandle`. > > Note: This doc is copied from > https://github.com/openjdk/jdk/blob/ee0d309bbd33302d8c6f35155e975db77aaea785/src/java.base/share/classes/java/lang/foreign/MemoryLayout.java#L279-L282 > with slight adjustments. See the rendering at > https://docs.oracle.com/en/java/javase/24/docs/api/java.base/java/lang/foreign/MemoryLayout.html#access-mode-restrictions Changes requested by shade (Reviewer). src/java.base/share/classes/java/lang/invoke/MethodHandles.java line 4311: > 4309: * access modes {@code get} and {@code set} for {@code long}, > {@code > 4310: * double} are supported but might lead to word tearing, as > described in > 4311: * Section {@jls 17.7} of <cite>The Java Language > Specification</cite>. ...except that JLS 17.7 is "Non-Atomic Treatment of double and long". Word tearing (JLS 17.6) should still be very much forbidden. This all means that [MemoryLayout.java](https://github.com/openjdk/jdk/blob/ee0d309bbd33302d8c6f35155e975db77aaea785/src/java.base/share/classes/java/lang/foreign/MemoryLayout.java#L279-L282) comment is also incorrect. Note how the previous paragraph talks about "support atomic access", which is a correct term here. ------------- PR Review: https://git.openjdk.org/jdk/pull/26258#pullrequestreview-3009183292 PR Review Comment: https://git.openjdk.org/jdk/pull/26258#discussion_r2200018561
