On Mon, 22 Sep 2025 22:26:15 GMT, David Beaumont <[email protected]> wrote:

>> C++ changes for supporting preview mode *when* preview mode resources (with 
>> new location flags) are available.
>> 
>> At the moment, this code will operate on non-preview jimage files (1.0) and 
>> act as if no preview resources are available by virtue of the default value 
>> for missing attributes being zero (which matches location flags for "normal" 
>> entries).
>
> src/java.base/share/native/libjimage/imageFile.hpp line 248:
> 
>> 246:     };
>> 247: 
>> 248:     // Flag masks for the ATTRIBUTE_PREVIEW_FLAGS attribute. Defined so
> 
> As discussed offline, there might be a neater expression for these flags with:
> 
> 
> bit: 1 0
>     [0,0] 0 = normal_entry (only)
>     [0,1] 1 = normal_entry_with_preview_version
>     [1,0] 2 = preview_entry (only)
>     [1,1] 3 = preview_entry_with_normal_version
>        ^-- has other version bit
>      ^---- is preview version bit

After remembering that these flags are also used in packages/xxx locations, 
where "is this a preview version" makes no conceptual sense, I no longer think 
it would be a good idea to change the flag definitions.

-------------

PR Review Comment: 
https://git.openjdk.org/valhalla/pull/1609#discussion_r2370800106

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