RFR: 7904115: Fix for AIX test case failures due to incorrect alignment for double and pointer [v2]

[Maurizio Cimadamore]

On Fri, 21 Nov 2025 17:04:39 GMT, Maurizio Cimadamore <mcimadamore at openjdk.org> wrote:

> My 0.02$ on this issue.

I had  an offline discussion with @JornVernee --- it seems part of the issue here is caused by the fact that the required alignment we pass is the alignment of the struct as a whole (which takes into account any `pragma pack` directives). In reality it would probably be more robust to figure out what the alignment is based on what is the offset at which clang wants to put the struct field. This should work and only make very minimal assumptions.

I also wonder if we should do that as part of this PR, or as a separate PR.

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PR Comment: https://git.openjdk.org/jextract/pull/296#issuecomment-3564203711