RFR: 8368475: [lworld] Add preview classes to jimage at make time [v4]

[Roger Riggs]

On Tue, 23 Sep 2025 23:07:18 GMT, David Beaumont <duke at openjdk.org> wrote:

>> Copies valuetype classes for each module into corresponding "/META-INF/preview/..." sub-directories to be pulled into jimage files and processed by the new preview mode handling code.
>> 
>> There might be a better way to do this in terms of Makefile semantics, but this seems to work well enough and doesn't prevent the value-class JAR files being generated for patching (which is still how everyone will get value classes until the rest of the work is plumbed in).
>> 
>> To enable the new preview mode work, set the "DISABLE_PREVIEW_PATCHING" system property to "true".
>> 
>> This should be review against https://github.com/openjdk/valhalla/pull/1621.
>
> David Beaumont has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains five commits:
> 
>  - Copy value classes into preview directories for inclusion in jimage
>  - Restoring lost changes and updating some comments.
>  - add system property guard to preview mode
>  - jimage writer changes to support preview mode.
>    
>    * Remove TODOs now jimage version is bumped
>    * jimage writer changes to support preview mode.
>  - Manually deleting ImageReaderFactory (it returned somehow)

make/CompileJavaModules.gmk line 184:

> 182: 
> 183:     TARGETS += $(PREVIEW_OUTPUTDIR)/_copy_valueclasses.marker
> 184: 

I expect build reviewer will suggest using the SetupCopyFiles mechanism to copy files.

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PR Review Comment: https://git.openjdk.org/valhalla/pull/1622#discussion_r2383475070