RFR: 8277489: Rewrite JAAS UnixLoginModule with FFM [v5]

[Maurizio Cimadamore]

On Fri, 2 Jan 2026 17:00:37 GMT, Weijun Wang <weijun at openjdk.org> wrote:

>> Rewrite the native calls with FFM.
>
> Weijun Wang has updated the pull request incrementally with one additional commit since the last revision:
> 
>   fail early on Windows, and more comments

src/jdk.security.auth/share/classes/com/sun/security/auth/module/UnixSystem.java line 87:

> 85:             = ((AddressLayout) LINKER.canonicalLayouts().get("void*"))
> 86:             .withTargetLayout(MemoryLayout.sequenceLayout(java.lang.Long.MAX_VALUE, C_CHAR));
> 87:     private static final ValueLayout.OfLong C_SIZE_T

Note that portability between 32/64 is hard, even if using canonicalLayouts -- because size_t will likely be an IntLayout on arm32, while a LongLayout in 64 bits. If you never use this layout to access data (e.g. call `MemorySegment::get/set`) I'd suggest to avoid the cast, and leave it just as `ValueLayout`

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PR Review Comment: https://git.openjdk.org/jdk/pull/28931#discussion_r2661342378