7903314: Jextract doesn't honor pack pragmas

[mcimadamore]

This patch fixes a long standing issue where jextract ignores alignment directives (e.g. pragma pack). Because of this issue, jextract can sometiems generate layouts whose alignment is incorrect (e.g. jextract might attempt to add a i32 to a struct at an offset that is not 32-bit aligned).

The fix is in RecordLayoutComputer - when we need to emit the layout of a given struct field, we need to additionally pass in the offset at which the field is added. Then we check that the offset conforms to the field alignment. If not, we force-align the layout to the available alignment. This should only affect instances of ValueLayout.

During code generation, when we lookup a value layout, we first drop both name and custom alignment (so that the lookup will find what it's looking for). Additional name and/or alignment is added back when the layout is turned back into a string.

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Progress

• Change must not contain extraneous whitespace
• Change must be properly reviewed (no review required)

Issue

• CODETOOLS-7903314: Jextract doesn't honor pack pragmas

Reviewers

• Jorn Vernee (@JornVernee - Committer)

Reviewing

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$ git fetch https://git.openjdk.org/jextract pull/113/head:pull/113
$ git checkout pull/113

Update a local copy of the PR:
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$ git pull https://git.openjdk.org/jextract pull/113/head

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$ git pr checkout 113

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https://git.openjdk.org/jextract/pull/113.diff

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[openjdk]

@mcimadamore This change now passes all automated pre-integration checks.

After integration, the commit message for the final commit will be:

7903314: Jextract doesn't honor pack pragmas

Reviewed-by: jvernee

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[mlbridge]

Webrevs

• 00: Full (48bfc773)

[mcimadamore]

/integrate

[openjdk]

Going to push as commit 750c415.

[openjdk]

@mcimadamore Pushed as commit 750c415.

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