../src/share/classes/com/sun/javatest/diff/SuperDiff.java:243: warning: [serial] non-transient instance field of a serializable class declared with a non-serializable type
            platforms.add(platform);
            ^
../src/share/classes/com/sun/javatest/diff/SuperDiff.java:262: warning: [serial] non-transient instance field of a serializable class declared with a non-serializable type
            infoTable.put(dir.getPath(), new Info(platform, date));
            ^
error: warnings found and -Werror specified


Also, with 18, the security manager issue causes tests to fail: RegressionSecurityManager.java

            if (v >= 18) {
                // Do not install any security manager for JDK 18 or later;
                // see JEP 411: Deprecate the Security Manager for Removal
                return;
            }
 As of now, we either get warnings at startup, which can cause issues for some tests, or we avoid the warnings and risk test code calling System.exit.