[GR-51416] Registering a class as initialize-at-build-time should immediately trigger initialization.

sdk/src/org.graalvm.nativeimage/src/org/graalvm/nativeimage/hosted/RuntimeClassInitialization.java

@@ -103,12 +103,20 @@ public static void initializeAtRunTime(Class<?>... classes) {
     /**
      * Registers the provided classes as eagerly initialized during image-build time.
      * <p>
-     * All static initializers of {@code classes} will be executed during image-build time and
-     * static fields that are assigned values will be available at runtime. {@code static final}
+     * All static initializers of {@code classes} will be executed immediately at image-build time
+     * and static fields that are assigned values will be available at runtime. {@code static final}
      * fields will be considered as constant.
      * <p>
      * It is up to the user to ensure that this behavior makes sense and does not lead to wrong
      * application behavior.
+     * <p>
+     * After this method returns, all listed classes are initialized in the VM that runs the image
+     * generator. Therefore, this method can be used to resolve deadlocks and cycles in class
+     * initializer by starting initialization with a known-good entry class.
+     * <p>
+     * All superclasses and superinterfaces that are initialized before any of the listed classes
+     * are registered for initialization at build time too. Please look at the Java specification
+     * for the exact rules, especially regarding interfaces that declare default methods.
      *
      * @since 19.0
      */

substratevm/src/com.oracle.svm.hosted/src/com/oracle/svm/hosted/classinitialization/AllowAllHostedUsagesClassInitializationSupport.java

@@ -26,14 +26,13 @@
 
 import java.lang.reflect.Proxy;
 
-import jdk.graal.compiler.java.LambdaUtils;
-
 import com.oracle.graal.pointsto.meta.AnalysisMetaAccess;
 import com.oracle.graal.pointsto.meta.AnalysisUniverse;
 import com.oracle.svm.core.util.UserError;
 import com.oracle.svm.core.util.VMError;
 import com.oracle.svm.hosted.ImageClassLoader;
 
+import jdk.graal.compiler.java.LambdaUtils;
 import jdk.vm.ci.meta.MetaAccessProvider;
 
 class AllowAllHostedUsagesClassInitializationSupport extends ClassInitializationSupport {
@@ -45,21 +44,7 @@ class AllowAllHostedUsagesClassInitializationSupport extends ClassInitialization
     @Override
     public void initializeAtBuildTime(Class<?> aClass, String reason) {
         UserError.guarantee(!configurationSealed, "The class initialization configuration can be changed only before the phase analysis.");
-        Class<?> cur = aClass;
-        do {
-            classInitializationConfiguration.insert(cur.getTypeName(), InitKind.BUILD_TIME, cur == aClass ? reason : "super type of " + aClass.getTypeName(), true);
-            initializeInterfacesAtBuildTime(cur.getInterfaces(), "interface of " + aClass.getTypeName());
-            cur = cur.getSuperclass();
-        } while (cur != null);
-    }
-
-    private void initializeInterfacesAtBuildTime(Class<?>[] interfaces, String reason) {
-        for (Class<?> iface : interfaces) {
-            if (metaAccess.lookupJavaType(iface).declaresDefaultMethods()) {
-                classInitializationConfiguration.insert(iface.getTypeName(), InitKind.BUILD_TIME, reason, true);
-            }
-            initializeInterfacesAtBuildTime(iface.getInterfaces(), reason);
-        }
+        forceInitializeHosted(aClass, reason, false);
     }
 
     @Override
@@ -103,7 +88,13 @@ public void forceInitializeHosted(Class<?> clazz, String reason, boolean allowIn
         classInitKinds.put(clazz, initKind);
 
         forceInitializeHosted(clazz.getSuperclass(), "super type of " + clazz.getTypeName(), allowInitializationErrors);
-        forceInitializeInterfaces(clazz.getInterfaces(), "super type of " + clazz.getTypeName());
+        if (!clazz.isInterface()) {
+            /*
+             * Initialization of an interface does not trigger initialization of superinterfaces.
+             * Regardless whether any of the involved interfaces declare default methods.
+             */
+            forceInitializeInterfaces(clazz.getInterfaces(), "super type of " + clazz.getTypeName());
+        }
     }
 
     private void forceInitializeInterfaces(Class<?>[] interfaces, String reason) {

substratevm/src/com.oracle.svm.test/src/com/oracle/svm/test/clinit/TestClassInitialization.java

@@ -28,6 +28,7 @@
 import java.lang.reflect.Method;
 import java.util.ArrayList;
 import java.util.Arrays;
+import java.util.Collections;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
@@ -663,6 +664,100 @@ static synchronized int synchronizedMethod() {
     }
 }
 
+class InitializationOrder {
+    static final List<Class<?>> initializationOrder = Collections.synchronizedList(new ArrayList<>());
+}
+
+interface Test1_I1 {
+    default void defaultI1() {
+    }
+
+    int order = add();
+
+    static int add() {
+        InitializationOrder.initializationOrder.add(Test1_I1.class);
+        return 42;
+    }
+}
+
+interface Test1_I2 extends Test1_I1 {
+    int order = add();
+
+    static int add() {
+        InitializationOrder.initializationOrder.add(Test1_I2.class);
+        return 42;
+    }
+}
+
+interface Test1_I3 extends Test1_I2 {
+    default void defaultI3() {
+    }
+
+    int order = add();
+
+    static int add() {
+        InitializationOrder.initializationOrder.add(Test1_I3.class);
+        return 42;
+    }
+}
+
+interface Test1_I4 extends Test1_I3 {
+    int order = add();
+
+    static int add() {
+        InitializationOrder.initializationOrder.add(Test1_I4.class);
+        return 42;
+    }
+}
+
+class Test1_A implements Test1_I4 {
+    static {
+        InitializationOrder.initializationOrder.add(Test1_A.class);
+    }
+}
+
+interface Test2_I1 {
+    default void defaultI1() {
+    }
+
+    int order = add();
+
+    static int add() {
+        InitializationOrder.initializationOrder.add(Test2_I1.class);
+        return 42;
+    }
+}
+
+interface Test2_I2 extends Test2_I1 {
+    int order = add();
+
+    static int add() {
+        InitializationOrder.initializationOrder.add(Test2_I2.class);
+        return 42;
+    }
+}
+
+interface Test2_I3 extends Test2_I2 {
+    default void defaultI3() {
+    }
+
+    int order = add();
+
+    static int add() {
+        InitializationOrder.initializationOrder.add(Test2_I3.class);
+        return 42;
+    }
+}
+
+interface Test2_I4 extends Test2_I3 {
+    int order = add();
+
+    static int add() {
+        InitializationOrder.initializationOrder.add(Test2_I4.class);
+        return 42;
+    }
+}
+
 abstract class TestClassInitializationFeature implements Feature {
 
     private void checkClasses(boolean checkSafeEarly, boolean checkSafeLate) {
@@ -695,6 +790,65 @@ abstract void checkClass(Class<?> checkedClass, boolean checkSafeEarly, boolean
     public void afterRegistration(AfterRegistrationAccess access) {
         /* We need to access the checkedClasses array both at image build time and run time. */
         RuntimeClassInitialization.initializeAtBuildTime(TestClassInitialization.class);
+
+        /*
+         * Initialization of a class first triggers initialization of all superinterfaces that
+         * declared default methods.
+         */
+        InitializationOrder.initializationOrder.clear();
+        assertNotInitialized(Test1_I1.class, Test1_I2.class, Test1_I3.class, Test1_I4.class, Test1_A.class);
+        RuntimeClassInitialization.initializeAtBuildTime(Test1_A.class);
+        assertNotInitialized(Test1_I2.class, Test1_I4.class);
+        assertInitialized(Test1_I1.class, Test1_I3.class, Test1_A.class);
+        assertArraysEqual(new Object[]{Test1_I1.class, Test1_I3.class, Test1_A.class}, InitializationOrder.initializationOrder.toArray());
+
+        /*
+         * The old class initialization policy is wrong regarding interfaces, but we do not want to
+         * change that now because it will be deleted soon.
+         */
+        if (TestClassInitialization.simulationEnabled) {
+
+            /*
+             * Initialization of an interface does not trigger initialization of superinterfaces.
+             * Regardless whether any of the involved interfaces declare default methods.
+             */
+            InitializationOrder.initializationOrder.clear();
+            assertNotInitialized(Test2_I1.class, Test2_I2.class, Test2_I3.class, Test2_I4.class);
+            RuntimeClassInitialization.initializeAtBuildTime(Test2_I4.class);
+            assertNotInitialized(Test2_I1.class, Test2_I2.class, Test2_I3.class);
+            assertInitialized(Test2_I4.class);
+            assertArraysEqual(new Object[]{Test2_I4.class}, InitializationOrder.initializationOrder.toArray());
+            RuntimeClassInitialization.initializeAtBuildTime(Test2_I3.class);
+            assertNotInitialized(Test2_I1.class, Test2_I2.class);
+            assertInitialized(Test2_I3.class, Test2_I4.class);
+            assertArraysEqual(new Object[]{Test2_I4.class, Test2_I3.class}, InitializationOrder.initializationOrder.toArray());
+            RuntimeClassInitialization.initializeAtBuildTime(Test2_I2.class);
+            assertNotInitialized(Test2_I1.class);
+            assertInitialized(Test2_I2.class, Test2_I3.class, Test2_I4.class);
+            assertArraysEqual(new Object[]{Test2_I4.class, Test2_I3.class, Test2_I2.class}, InitializationOrder.initializationOrder.toArray());
+        }
+    }
+
+    private void assertNotInitialized(Class<?>... classes) {
+        for (var clazz : classes) {
+            if (!Unsafe.getUnsafe().shouldBeInitialized(clazz)) {
+                throw new AssertionError("Already initialized: " + clazz);
+            }
+        }
+    }
+
+    private void assertInitialized(Class<?>... classes) {
+        for (var clazz : classes) {
+            if (Unsafe.getUnsafe().shouldBeInitialized(clazz)) {
+                throw new AssertionError("Not initialized: " + clazz);
+            }
+        }
+    }
+
+    private static void assertArraysEqual(Object[] expected, Object[] actual) {
+        if (!Arrays.equals(expected, actual)) {
+            throw new RuntimeException("expected " + Arrays.toString(expected) + " but found " + Arrays.toString(actual));
+        }
     }
 
     @Override