Disallowing the dynamic loading of agents by default

[Thomas Stüfe]

Hi Ron,

Will this affect attaching via jcmd?

Thanks, Thomas

On Thu, Mar 16, 2023 at 7:48 PM Ron Pressler <ron.pressler at oracle.com>
wrote:

> Hi.
>
> In JDK 21 we intend to disallow the dynamic loading of agents by default.
> This
> will affect tools that use the Attach API to load an agent into a JVM some
> time
> after the JVM has started [1]. There is no change to any of the mechanisms
> that
> load an agent at JVM startup (-javaagent/-agentlib on the command line or
> the
> Launcher-Agent-Class attribute in the main JAR's manifest).
>
> This change in default behavior was proposed in 2017 as part of JEP 261
> [2][3].
> At that time the consensus was to switch to this default not in JDK 9 but
> in a
> later release to give tool maintainers sufficient time to inform their
> users.
> To allow the dynamic loading of agents, users will need to specify
> -XX:+EnableDynamicAgentLoading on the command line.
>
> I'll post a draft JEP for review shortly.
>
> -- Ron
>
> [1]:
> https://docs.oracle.com/en/java/javase/19/docs/api/jdk.attach/com/sun/tools/attach/package-summary.html
> [2]: https://openjdk.org/jeps/261
> [3]: https://mail.openjdk.org/pipermail/jigsaw-dev/2017-April/012040.html
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