RFR: 8368333: [lworld] Add preview mode to ImageReader and JRT file-system [v7]

[Roger Riggs]

On Wed, 22 Oct 2025 19:35:37 GMT, David Beaumont <duke at openjdk.org> wrote:

>> src/java.base/share/classes/jdk/internal/jimage/ImageStrings.java line 38:
>> 
>>> 36:     // String offset constants are useful for efficient classification
>>> 37:     // of location entries without string comparison. These may change
>>> 38:     // between jimage versions (they are checked during initialization).
>> 
>> The checking seem only to be done when ImageStringsWriter is loaded/initialized.
>> There may be a small risk that a mismatch of the image with the ImageStringsReader could occur.
>> Can they be checked also by the reader?
>
> Hmm, I don't see a nice way to do this at runtime since you can't lookup string offsets by their value (as far as I can see).
> 
> It's no more fragile than the old code (which had hard-coded constants for "class" and "" (and wasn't self-checking their validity). At least now it's tested at build time.
> 
> If the version number matches it should be safe. I'll add a comment about how changing existing entries is problematic.

Seems unlikely to mismatch.  
ImageStringReader.match(offset, string, indxe) could be used to check the Strings or ImageStringReader.get(offset).

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PR Review Comment: https://git.openjdk.org/valhalla/pull/1619#discussion_r2455711286