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

[Martin Doerr]

On Wed, 7 Jan 2026 14:05:32 GMT, Maurizio Cimadamore <mcimadamore at openjdk.org> wrote:

>> I haven't tried (not my machine), but it's undefined behavior. There's no guarantee that `getpwuid_r` does what we expect. We should never use undefined behavior. Also note that not only AIX is affected.
>
>> It's unfortunate that the FFM doesn't provide a good abstraction for passing `uint32_t`. Maybe we should implement an enhancement?
> 
> Indeed, the status quo with respect to unsigned values passed to downcalls is a bit suboptimal, esp. in certain ABIs where sign/zero extension is required. This is tracked here:
> 
> https://bugs.openjdk.org/browse/JDK-8336664
> 
> (apologies -- this link was already shared by @dmlloyd )

Should we use the workaround I have proposed above until a better solution for [JDK-8336664](https://bugs.openjdk.org/browse/JDK-8336664) is available? Or are there other suggestions?

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PR Review Comment: https://git.openjdk.org/jdk/pull/28931#discussion_r2681912656