Summary

Change the default value of the command line option --sun-misc-unsafe-memory-access from allow to warn. A warning is printed to standard error on the first occasion that any memory-access method in sun.misc.Unsafe is used.

Problem

JEP 471 introduced --sun-misc-unsafe-memory-access={allow|warn|debug|deny}, which controls the runtime behavior of sun.misc.Unsafe's memory-access methods, with the default value of allow.

The next step in the roadmap is to change the default value of the option from allow to warn. A future JEP and CSR will propose to change the default value to deny.

Solution

Change the default value of the command line option --sun-misc-unsafe-memory-access to warn. This is the equivalent of running with --sun-misc-unsafe-memory-access=warn. A warning is printed to standard error on the first occasion that any memory-access method is used.

The warning can be suppressed in this release by running with --sun-misc-unsafe-memory-access=allow.

Developers can prepare for the future by testing with --sun-misc-unsafe-memory-access=deny.

Specification

There are no specification changes.

The output from java -X for the command line option changes to:

    --sun-misc-unsafe-memory-access=<value>
                      allow or deny usage of unsupported API sun.misc.Unsafe
                      <value> is one of "allow", "warn", "debug", or "deny".
                      The default value is "warn".