RFR: 8369451: Debug agent support for USE_ITERATE_THROUGH_HEAP is broken and should be removed [v2]

[Alex Menkov]

On Wed, 8 Oct 2025 22:47:24 GMT, Chris Plummer <cjplummer at openjdk.org> wrote:

>> Remove support for the debug agents USE_ITERATE_THROUGH_HEAP support, and the debugflags option used to enable it. Support has been broken for a very long time and can't possibly be relied on by anyone. Please see the CR for a full description.
>> 
>> Note there is a very small compatibility risk with removing the debugflags option (any script that uses it would break). But since it was only used in support of USE_ITERATE_THROUGH_HEAP, is not included in the docs, and is only included in the help output for debug builds, I think the risk is very low. If used, script failures are likely a good thing as it would call attention to the fact that the user is attempting to use functionality that doesn't (and hasn't) worked.
>
> Chris Plummer has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Get rid of no longer needed cbObjectTagInstance() function

Marked as reviewed by amenkov (Reviewer).

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PR Review: https://git.openjdk.org/jdk/pull/27706#pullrequestreview-3320346750