8296743: Tighten Class.getModifiers spec for array classes

Reviewed-by: rriggs, mchung, heidinga

src/java.base/share/classes/java/lang/Class.java

@@ -1296,17 +1296,21 @@ private Class<?> elementType() {
      * {@code abstract} and {@code interface}; they should be decoded
      * using the methods of class {@code Modifier}.
      *
-     * <p> If the underlying class is an array class, then its
-     * {@code public}, {@code private} and {@code protected}
-     * modifiers are the same as those of its component type.  If this
-     * {@code Class} object represents a primitive type or void, its
-     * {@code public} modifier is always {@code true}, and its
-     * {@code protected} and {@code private} modifiers are always
-     * {@code false}. If this {@code Class} object represents an array class, a
-     * primitive type or void, then its {@code final} modifier is always
-     * {@code true} and its interface modifier is always
-     * {@code false}. The values of its other modifiers are not determined
-     * by this specification.
+     * <p> If the underlying class is an array class:
+     * <ul>
+     * <li> its {@code public}, {@code private} and {@code protected}
+     *      modifiers are the same as those of its component type
+     * <li> its {@code abstract} and {@code final} modifiers are always
+     *      {@code true}
+     * <li> its interface modifier is always {@code false}, even when
+     *      the component type is an interface
+     * </ul>
+     * If this {@code Class} object represents a primitive type or
+     * void, its {@code public}, {@code abstract}, and {@code final}
+     * modifiers are always {@code true}.
+     * For {@code Class} objects representing void, primitive types, and
+     * arrays, the values of other modifiers are {@code false} other
+     * than as specified above.
      *
      * <p> The modifier encodings are defined in section {@jvms 4.1}
      * of <cite>The Java Virtual Machine Specification</cite>.
@@ -1320,6 +1324,7 @@ private Class<?> elementType() {
      * @since 1.1
      * @jls 8.1.1 Class Modifiers
      * @jls 9.1.1. Interface Modifiers
+     * @jvms 4.1 The {@code ClassFile} Structure
      */
     @IntrinsicCandidate
     public native int getModifiers();
@@ -1328,17 +1333,19 @@ private Class<?> elementType() {
      * {@return an unmodifiable set of the {@linkplain AccessFlag access
      * flags} for this class, possibly empty}
      *
-     * <p> If the underlying class is an array class, then its
-     * {@code PUBLIC}, {@code PRIVATE} and {@code PROTECTED}
-     * access flags are the same as those of its component type.  If this
-     * {@code Class} object represents a primitive type or void, the
-     * {@code PUBLIC} access flag is present, and the
-     * {@code PROTECTED} and {@code PRIVATE} access flags are always
-     * absent. If this {@code Class} object represents an array class, a
-     * primitive type or void, then the {@code FINAL} access flag is always
-     * present and the interface access flag is always
-     * absent. The values of its other access flags are not determined
-     * by this specification.
+     * <p> If the underlying class is an array class:
+     * <ul>
+     * <li> its {@code PUBLIC}, {@code PRIVATE} and {@code PROTECTED}
+     *      access flags are the same as those of its component type
+     * <li> its {@code ABSTRACT} and {@code FINAL} flags are present
+     * <li> its {@code INTERFACE} flag is absent, even when the
+     *      component type is an interface
+     * </ul>
+     * If this {@code Class} object represents a primitive type or
+     * void, the flags are {@code PUBLIC}, {@code ABSTRACT}, and
+     * {@code FINAL}.
+     * For {@code Class} objects representing void, primitive types, and
+     * arrays, access flags are absent other than as specified above.
      *
      * @see #getModifiers()
      * @jvms 4.1 The ClassFile Structure

test/jdk/java/lang/Class/getModifiers/TestPrimitiveAndArrayModifiers.java

@@ -0,0 +1,136 @@
+/*
+ * Copyright (c) 2022, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+import java.lang.reflect.Modifier;
+import java.lang.annotation.*;
+
+/*
+ * @test
+ * @bug 8296743
+ * @summary Verify array classes and primitives have expected modifiers
+ */
+@ExpectedModifiers(Modifier.PUBLIC | Modifier.FINAL | Modifier.ABSTRACT)
+public class TestPrimitiveAndArrayModifiers {
+
+    /*
+     * Relevant excerpt of the Class.getModifiers() specification:
+     * <p> If the underlying class is an array class:
+     * <ul>
+     * <li> its {@code public}, {@code private} and {@code protected}
+     *      modifiers are the same as those of its component type
+     * <li> its {@code final} and {@code abstract} modifiers are always
+     *      {@code true}
+     * <li> its interface modifier is always {@code false}, even when
+     *      the component type is an interface
+     * </ul>
+     */
+
+    public static void main(String... args) throws Exception {
+        testPrimitives();
+        testArrays();
+    }
+
+    private static void testArrays() {
+        Class<?>[] testCases = {
+            TestPrimitiveAndArrayModifiers.class,
+
+            PackagePrivateClass.class,
+            ProtectedClass.class,
+            PrivateClass.class,
+
+            PublicInterface.class,
+            PackagePrivateInterface.class,
+            ProtectedInterface.class,
+            PrivateInterface.class,
+        };
+
+        for(var testCase : testCases) {
+            int expectedModifiers =
+                testCase.getAnnotation(ExpectedModifiers.class).value();
+            Class<?> arrayClass = testCase.arrayType();
+            int actualModifiers = arrayClass.getModifiers();
+            if (expectedModifiers != actualModifiers) {
+                throw new RuntimeException("Expected " + Modifier.toString(expectedModifiers) +
+                                           "on " + testCase.getCanonicalName() +
+                                           ", but got " + Modifier.toString(actualModifiers));
+            }
+        }
+    }
+
+    @ExpectedModifiers(Modifier.FINAL | Modifier.ABSTRACT)
+    class PackagePrivateClass {}
+
+    @ExpectedModifiers(Modifier.FINAL | Modifier.ABSTRACT | Modifier.PROTECTED)
+    protected class ProtectedClass {}
+
+    @ExpectedModifiers(Modifier.FINAL | Modifier.ABSTRACT | Modifier.PRIVATE)
+    private class  PrivateClass {}
+
+    @ExpectedModifiers(Modifier.FINAL | Modifier.ABSTRACT | Modifier.PUBLIC)
+    public interface PublicInterface {}
+
+    @ExpectedModifiers(Modifier.FINAL | Modifier.ABSTRACT)
+    interface PackagePrivateInterface {}
+
+    @ExpectedModifiers(Modifier.FINAL | Modifier.ABSTRACT | Modifier.PROTECTED)
+    protected interface ProtectedInterface {}
+
+    @ExpectedModifiers(Modifier.FINAL | Modifier.ABSTRACT | Modifier.PRIVATE)
+    private interface PrivateInterface {}
+
+    /*
+     * Relevant excerpt of the Class.getModifiers() specification:
+     *
+     * If this {@code Class} object represents a primitive type or
+     * void, its {@code public}, {@code abstract}, and {@code final}
+     * modifiers are always {@code true}.
+     */
+    private static void testPrimitives() {
+        Class<?>[] testCases = {
+            void.class,
+            boolean.class,
+            byte.class,
+            short.class,
+            char.class,
+            int.class,
+            float.class,
+            long.class,
+            double.class,
+        };
+
+        for(var testCase : testCases) {
+            int actualModifiers = testCase.getModifiers();
+            if ((Modifier.PUBLIC | Modifier.ABSTRACT | Modifier.FINAL) !=
+                actualModifiers) {
+                throw new RuntimeException("Bad modifiers " +
+                                           Modifier.toString(actualModifiers) +
+                                           " on primitive type " + testCase);
+            }
+        }
+    }
+}
+
+@Retention(RetentionPolicy.RUNTIME)
+@interface ExpectedModifiers {
+    int value() default 0;
+}

test/jdk/java/lang/reflect/AccessFlag/ClassAccessFlagTest.java

@@ -23,7 +23,7 @@
 
 /*
  * @test
- * @bug 8266670 8291734
+ * @bug 8266670 8291734 8296743
  * @summary Test expected AccessFlag's on classes.
  */
 
@@ -98,23 +98,14 @@ private static void checkPrimitives() {
             void.class // same access flag rules
         };
 
-        var mustBePresent = Set.of(AccessFlag.PUBLIC, AccessFlag.FINAL);
-        var mustBeAbsent = Set.of(AccessFlag.PRIVATE,
-                                  AccessFlag.PROTECTED,
-                                  AccessFlag.INTERFACE);
+        var expected = Set.of(AccessFlag.PUBLIC,
+                              AccessFlag.FINAL,
+                              AccessFlag.ABSTRACT);
 
         for(var primClass : primitives) {
-            // PUBLIC must be present, PROTECTED and PRIVATE must be
-            // absent.
-            // FINAL must be present, INTERFACE must be absent.
             var accessFlags = primClass.accessFlags();
-            if (!accessFlags.containsAll(mustBePresent)) {
-                throw new RuntimeException("Missing mandatory flags on " +
-                                           primClass);
-            }
-
-            if (containsAny(accessFlags, mustBeAbsent)) {
-                throw new RuntimeException("Unexpected flags present on " +
+            if (!accessFlags.equals(expected)) {
+                throw new RuntimeException("Unexpected flags on " +
                                            primClass);
             }
         }