RFR: 8286983: Add mention of "Preview Feature" for new loom related jdb and debug agent options

[Chris Plummer]

On Thu, 19 May 2022 13:10:50 GMT, Alan Bateman <alanb at openjdk.org> wrote:

>> As part of the loom integration, jdb added -trackvthreads and the debug agent added "enumeratevthreads". The help text for these options should call out that they are Preview Features.
>
> src/jdk.jdwp.agent/share/native/libjdwp/debugInit.c line 880:
> 
>> 878:  "onuncaught=y|n                   debug on any uncaught?            n\n"
>> 879:  "timeout=<timeout value>          for listen/attach in milliseconds n\n"
>> 880:  "enumeratevthreads=y|n            (Preview Feature) thread lists include all vthreads\n"
> 
> I think the description needs to say "virtual threads" rather than "vthreads". Also I think "(Preview" needs to go after "virtual threads" to make it clearer that it's virtual threads that are preview,.

I was really trying to emphasize that the flag is preview, and therefore may change or go away.  If I change as  you suggest, the reader could imply that as long as virtual threads support is in place, then the flag will be also (and in its current form).

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PR: https://git.openjdk.java.net/jdk/pull/8780