Hi Thomas,
On 28/03/2019 5:02 pm, Thomas Stüfe wrote:
Hi Serguei,
This is planned to be introduced in jdk 13?
The only concern I have is that both paths (old and new behavior) should
be well tested, and hiding the old behavior behind an optional switch
may reduce its test coverage considerably.
The old behaviour is hardly ever used - I'm not even sure we currently
have a test that tries to use it - so it's already not "well tested" and
there's no intent here of increasing test coverage for the code we plan
to remove. The new path will be tested as we do have a test that expects
to get the error. And Serguei will of course have a simple test that
checks the flag with both values.
Cheers,
David
Cheers, Thomas
(p.s. html format does not work well with the OpenJDK mailing list
archive, see
https://mail.openjdk.java.net/pipermail/serviceability-dev/2019-March/027612.html)
On Thu, Mar 28, 2019 at 1:57 AM [email protected]
<mailto:[email protected]> <[email protected]
<mailto:[email protected]>> wrote:
Hi All,
This is request for comments and potentially reviews for the
following CSR:
https://bugs.openjdk.java.net/browse/JDK-8221528
*Problem*
Now, the implementation of JVMTI RedefineClasses and
RetransformClasses allows to
add/delete private static and private final instance methods in the
new class versions.
It means that current implementation does not follow the JVM TI spec
which explicitly states:
"The redefinition must not add, remove or rename fields or methods,
change the signatures
of methods, change modifiers, or change inheritance."
For details, please, see the spec:
https://docs.oracle.com/en/java/javase/12/docs/specs/jvmti.html#RedefineClasses
https://docs.oracle.com/en/java/javase/12/docs/specs/jvmti.html#RetransformClasses
The decision was made to align the implementation with the spec.
For reference, please, see the
https://bugs.openjdk.java.net/browse/JDK-8192936.
This decision is going to cause some inconveniences to the customers.
*Solution*
The solution is to introduce a compatibility mode with new
command-line VM option:
-XX:{+|-}AllowRedefinitionToAddOrDeleteMethods
New option will enable old behavior and allow the JVM TI
RedefineClasses and RetransformClasses
to add/delete private static and private final instance methods in
the new class versions.
Without this option the old behavior will be disabled.
New option is deprecated right away.
The plan is to keep it for a couple of releases to allow customers
(tool vendors)
to remove dependency on old behavior from their tools.
Thanks,
Serguei
