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# Eclipse OpenJ9 version 0.55.0 release notes

These release notes support the [Eclipse OpenJ9&trade; 0.55.0 release plan](https://projects.eclipse.org/projects/technology.openj9/releases/0.55.0/plan).

## Supported environments

OpenJ9 release 0.55.0 supports OpenJDK 25.

All releases are tested against the OpenJ9 functional verification (FV) test suite, the OpenJDK test suites, and additional tests provided by Adoptium.

To learn more about support for OpenJ9 releases, including OpenJDK levels and platform support, see [Supported environments](https://eclipse.org/openj9/docs/openj9_support/index.html).

## Notable changes in this release

The following table covers notable changes in v0.55.0. Further information about these changes can be found in the [user documentation](https://eclipse.dev/openj9/docs/version0.55/).

<table cellpadding="4" cellspacing="0" summary="" width="100%" rules="all" frame="border" border="1"><thead align="left">
<tr>
<th valign="bottom">Issue number</th>
<th valign="bottom">Description</th>
<th valign="bottom">Version / Platform</th>
<th valign="bottom">Impact</th>
</tr>
</thead>
<tbody>

<tr>
<td valign="top"><a href="https://github.com/eclipse-openj9/openj9/issues/19098">#19098</a></td>
<td valign="top">XL C++ Runtime 17.1.3.0 or later required for AIX OpenJ9 builds.</td>
<td valign="top">OpenJDK 25 and later (AIX)</td>
<td valign="top">Earlier, XL C++ Runtime 16.1.0.10 or later was required for AIX OpenJ9 builds. Now, AIX OpenJ9 builds require version 17.1.3.0 or later of the IBM XL C++ Runtime.</td>
</tr>

<tr>
<td valign="top"><a href="https://github.com/eclipse-openj9/openj9/pull/22626">#22626</a></td>
<td valign="top">The format of the <tt>java.vm.version</tt> system property value is updated to be compatible with the Runtime.Version parser.</td>
<td valign="top">All versions</td>
<td valign="top">Earlier, the format of the <tt>java.vm.version</tt> system property value was not standardized and structured and was not parse-able by the <tt>java.lang.Runtime.Version</tt> class.<br>With the new structured format, the <tt>java.lang.Runtime.Version</tt> class parses the value and you can extract specific information such as the information related to the VM version. This modification also changes the <tt>-version</tt> output. For example, <tt>build openj9-0.55.0</tt> changes to <tt>build 25+36-openj9-0.55.0</tt>.</td>
</tr>

<tr>
<td valign="top"><a href="https://github.com/ibmruntimes/openj9-openjdk-jdk/pull/1069">#1069</td>
<td valign="top">A new system property, <tt>-Djava.security.propertiesList</tt> is added to support a list of java.security property files.
</td>
<td valign="top">All versions</td>
<td valign="top">You can use the <tt>-Djava.security.propertiesList</tt> system property to configure a superset of profile files in different java.security property files. Instead of putting those different profiles into a single java.security file, you can now specify a list of java.security property files that have the profiles that you want to use.

This is an OpenJDK change in the OpenJDK versions maintained to support building with OpenJ9.</td>
</tr>
</tbody>
</table>

## Known issues

The v0.55.0 release contains the following known issues and limitations:

<table cellpadding="4" cellspacing="0" summary="" width="100%" rules="all" frame="border" border="1">
<thead align="left">
<tr>
<th valign="bottom">Issue number</th>
<th valign="bottom">Description</th>
<th valign="bottom">Platform</th>
<th valign="bottom">Impact</th>
<th valign="bottom">Workaround</th>
</tr>
</thead>

<tbody>
<tr>
<td valign="top"><a href="https://github.com/eclipse-openj9/openj9/issues/15011">#15011</a></td>
<td valign="top">The default stack size for the main thread is a smaller platform-dependent value.</td>
<td valign="top">All</td>
<td valign="top">The main thread stack size was 1 MB in releases before 0.32. In the 0.32 release and later it was modified to a smaller
platform-dependent value, the same value as the <tt>-Xmso</tt> setting. The 0.33 release increased the default <tt>-Xmso</tt> stack size
on x64 platforms, but builds with OpenJDK 17 and later also require more stack space to run. These changes might result in a
<tt>java.lang.StackOverflowError: operating system stack overflow</tt>.</td>
<td valign="top">Use <tt>-Xmso</tt> to set the default stack size. See the default value by using <tt>-verbose:sizes</tt>.</td>
</tr>

<tr>
<td valign="top"><a href="https://github.com/eclipse-openj9/openj9/issues/13767">#13767</a></td>
<td valign="top">Compressed references mode is not available.</td>
<td valign="top">Apple silicon macOS</td>
<td valign="top">You can use only the large heap (non-compressed references) mode.</td>
<td valign="top">None</td>
</tr>

<tr>
<td valign="top"><a href="https://github.com/eclipse-openj9/openj9/issues/14803">#14803</a></td>
<td valign="top">Using the <tt>-XX:+ShowHiddenFrames</tt> option in an OpenJ9 release that is built with OpenJDK 18 and later causes errors.</td>
<td valign="top">All platforms</td>
<td valign="top">Wrong exception might be thrown when using the Reflection API.</td>
<td valign="top">Avoid using the <tt>-XX:+ShowHiddenFrames</tt> option with OpenJDK 18 and later.</td>
</tr>

</tbody>
</table>

## Other changes

A full commit history for 0.55.0 release is available at [Eclipse OpenJ9 v0.55.0](https://github.com/eclipse-openj9/openj9/releases/tag/openj9-0.55.0).
