Long-term maintenance of verifier

[Chen Liang]

Thanks for the clarification. I totally agree with this decision of staying
on track of Option 2, as verification in the ClassFile API is mostly a
debug tool instead of a performance sensitive component.

That said, I noted we are a bit out of sync - for example, JDK-8350029 is
applied to runtime recently and it is clearly not in the ClassFile API. On
the mainline, lack of synchronization is not that big a deal as we have
only minor updates; however, project valhalla introduces strict fields,
which makes this synchronization more necessary, especially that otherwise
strict fields and early_larval_frame will be regarded as verification
errors.

We can probably start our updating on mainline so we can help valhalla. We
currently can claim the CF verifier lacks any patch after the initial
6/10/2022 publication in jdk-sandbox, but it is still helpful to know which
commit or which JDK release of verifier.cpp was the copy based off - we can
probably drop this "up-to-date-to-tag/commit" info in our shadow so we can
sync more easily.

Adam, do you know about the exact fork version of the verifier code? Once
we have a point in history, it's quite easy to check the hotspot commits
and see if we need to update our copy accordingly.

Regards, Chen

On Fri, Jun 6, 2025 at 11:46 PM Brian Goetz <brian.goetz at oracle.com> wrote:

> We had some discussions about this when the verifier was hand-translated
> from the C++ code.  At the time, some care was taken to ensure that we
> _not_ refactor-as-we-go, to preserve some structural similarity with the
> C++ code, so that deltas in the C++ code could be forward-ported.
>
> We were initially skeptical that duplicating this code would work, but it
> turned out to be quite effective.  Of course, long-term maintenance has to
> be part of the story.
>
> Going forward, I think we are still in the phase where the "keep it
> synchronized" strategy (Adam's #2) can work.  We have to be diligent to not
> make stylistic changes as we go, and keep up with changes in the runtime.
>
> Long term, I think there may be something we can do with #1, now that
> Panama is finalized, but that is not enough.  While calling into the C++
> code is now more practical, but that's not enough; the runtime code is
> designed solely to support on-the-fly analysis during class loading.  Some
> refactoring of the C++ API, undertaken by the runtime team, would be needed
> to allow it to serve multiple masters.
>
> On 6/5/2025 10:01 PM, Chen Liang wrote:
>
> Hello,
> I have noted that the classfile API's copy of migrated verifier seems to
> naturally diverge from the c++ code: for example, JDK-8350029 that
> restricts invokespecial to not allow invoking arbitrary interface methods
> is not shadowed to the classfile verifier. This problem will only get more
> serious once strict fields are added. Meanwhile, people expect
> ClassFile.verify to be up-to-date with the runtime verifier.
>
> What should we do to resolve this discrepancy? Should we have a separately
> maintained Java-based verifier implementing JVMS 4.10, or should we just
> increase our frequency of synchronizing with runtime?
>
> Regards,
> Chen Liang
>
>
>
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