reorganize JDKInitializationFeature

Author: zapster

substratevm/src/com.oracle.svm.hosted/src/com/oracle/svm/hosted/jdk/JDKInitializationFeature.java

@@ -158,14 +158,23 @@ public void afterRegistration(AfterRegistrationAccess access) {
             rci.initializeAtRunTime("java.io.UnixFileSystem", FutureDefaultsOptions.RUN_TIME_INITIALIZE_JDK_REASON);
             rci.initializeAtRunTime("java.io.WindowsFileSystem", FutureDefaultsOptions.RUN_TIME_INITIALIZE_JDK_REASON);
 
-            rci.initializeAtBuildTime("java.io.File", FutureDefaultsOptions.RUN_TIME_INITIALIZE_JDK_REASON);
-            rci.initializeAtBuildTime("sun.nio.fs.UnixPath", FutureDefaultsOptions.RUN_TIME_INITIALIZE_JDK_REASON);
-            rci.initializeAtBuildTime("sun.nio.fs.WindowsPath", FutureDefaultsOptions.RUN_TIME_INITIALIZE_JDK_REASON);
-
-            // holder for the default file system
+            /* Holder for the default file system. */
             rci.initializeAtRunTime("com.oracle.svm.core.jdk.runtimeinit.DefaultFileSystemHolder", FutureDefaultsOptions.RUN_TIME_INITIALIZE_JDK_REASON);
 
-            // JrtFS support
+            /*
+             * The following need to be build-time initialized because they can end up in the image
+             * heap. There are substitutions to patch the links to run-time initialized classes like
+             * FileSystem or FileSystemProvider.
+             */
+
+            /*
+             * Require explicit initializeAtBuildTime because the sun.nio.fs is registered for
+             * run-time initialization.
+             */
+            rci.initializeAtBuildTime("sun.nio.fs.UnixPath", "Allow UnixPath objects in the image heap (" + FutureDefaultsOptions.RUN_TIME_INITIALIZE_JDK_REASON + ")");
+            rci.initializeAtBuildTime("sun.nio.fs.WindowsPath", "Allow WindowsPath objects in the image heap (" + FutureDefaultsOptions.RUN_TIME_INITIALIZE_JDK_REASON + ")");
+
+            /* JrtFS support. */
             rci.initializeAtBuildTime("jdk.internal.jrtfs.SystemImage", FutureDefaultsOptions.RUN_TIME_INITIALIZE_JDK_REASON);
         }