[lworld] RFR: 8372515: [lworld] Plumb in javac flags for compiling with preview mode [v4]

[David Beaumont]

On Wed, 10 Dec 2025 10:39:21 GMT, Jan Lahoda <jlahoda at openjdk.org> wrote:

>> make/langtools/src/classes/build/tools/symbolgenerator/CreateSymbols.java line 1:
>> 
>>> 1: /*
>> 
>> I don't know anything about this code per se, this is all Jan's work.
>
> This adds a support for a different version of classfiles when running with preview in `ct.sym`. This is modeled as a new version (`@`). We only support preview for the most current version, so a single preview version ought to be enough.
> 
> I.e., inside `ct.sym`, 27 will be modeled as `R`, and the preview for 27 will be `@`. Classfiles that are unchanged between 27 and 27-preview will not be duplicates, in the same way classfiles that are common between 26 and 27 are shared and not duplicated.
> 
> (Overall, we may need change the encoding inside `ct.sym`, as we will run out of letters in ~4 years, but that's separate from the effort here.)

I'll try to sum this up with a comment somewhere.

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PR Review Comment: https://git.openjdk.org/valhalla/pull/1761#discussion_r2622556074