RFR: 8356645: Javac should utilize new ZIP file system read-only access mode [v2]

[David Beaumont]

On Wed, 18 Jun 2025 19:25:43 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 refreshed the contents of this pull request, and previous commits have been removed. The incremental views will show differences compared to the previous content of the PR. The pull request contains one new commit since the last revision:
> 
>   Applying read-only configuration for Javac internal use of ZIP/JAR file systems.

Apologies for the recent force push. I'm having to switch laptops and this is common from a different local repo.

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PR Comment: https://git.openjdk.org/jdk/pull/25639#issuecomment-2985592345