RFR: 8356645: Javac should utilize new ZIP file system read-only access mode [v4]

[David Beaumont]

On Thu, 19 Jun 2025 10:31:00 GMT, David Beaumont <duke at openjdk.org> wrote:

>> This PR seeks to integrate the new ZipFileSystem "accessMode" parameter to open internal ZIP/JAR files as read only, to act as defense in-depth against accidental modification.
>> 
>> Note that this currently also propagates the (currently undocumented) "zipinfo-time" parameter to several other places where ZIP/JAR files are opened, which is likely to improve performance. This was discussed and is expected to be safe (but it's something to be careful about).
>> This will, of course, be thoroughly tested before integration.
>> 
>> It also unifies several places to use a common helper method to obtain the environment map, adds more comments, and changes a small number of affected tests.
>> 
>> I'm also happy to update the original bug description to include the timestamp related changes as necessary.
>
> David Beaumont has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Reverted test (not caused by this PR).

Opened https://bugs.openjdk.org/browse/JDK-8360022 for the weird failing test thing (it was @cleanup, good call whoever suggested that!).

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PR Comment: https://git.openjdk.org/jdk/pull/25639#issuecomment-2987716897