8285401: Proxy class initializer should use 3-arg Class.forName to avoid unnecessary class initialization

Reviewed-by: rriggs, mchung

src/java.base/share/classes/java/lang/reflect/ProxyGenerator.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1999, 2021, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 1999, 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
@@ -73,6 +73,7 @@ final class ProxyGenerator extends ClassWriter {
     private static final String JLR_UNDECLARED_THROWABLE_EX = "java/lang/reflect/UndeclaredThrowableException";
 
     private static final String LJL_CLASS = "Ljava/lang/Class;";
+    private static final String LJL_CLASSLOADER = "Ljava/lang/ClassLoader;";
     private static final String LJLR_METHOD = "Ljava/lang/reflect/Method;";
     private static final String LJLR_INVOCATION_HANDLER = "Ljava/lang/reflect/InvocationHandler;";
 
@@ -597,6 +598,13 @@ final class ProxyGenerator extends ClassWriter {
         mv.visitTryCatchBlock(L_startBlock, L_endBlock, L_NoClassHandler,
                 JL_CLASS_NOT_FOUND_EX);
 
+        // Put ClassLoader at local variable index 0, used by
+        // Class.forName(String, boolean, ClassLoader) calls
+        mv.visitLdcInsn(Type.getObjectType(dotToSlash(className)));
+        mv.visitMethodInsn(INVOKEVIRTUAL, JL_CLASS,
+                "getClassLoader", "()" + LJL_CLASSLOADER, false);
+        mv.visitVarInsn(ASTORE, 0);
+
         mv.visitLabel(L_startBlock);
         for (List<ProxyMethod> sigmethods : proxyMethods.values()) {
             for (ProxyMethod pm : sigmethods) {
@@ -844,7 +852,8 @@ final class ProxyGenerator extends ClassWriter {
 
         /**
          * Generate code for initializing the static field that stores
-         * the Method object for this proxy method.
+         * the Method object for this proxy method. A class loader is
+         * anticipated at local variable index 0.
          */
         private void codeFieldInitialization(MethodVisitor mv, String className) {
             codeClassForName(mv, fromClass);
@@ -890,13 +899,18 @@ final class ProxyGenerator extends ClassWriter {
          * Generate code to invoke the Class.forName with the name of the given
          * class to get its Class object at runtime.  The code is written to
          * the supplied stream.  Note that the code generated by this method
-         * may cause the checked ClassNotFoundException to be thrown.
+         * may cause the checked ClassNotFoundException to be thrown. A class
+         * loader is anticipated at local variable index 0.
          */
         private void codeClassForName(MethodVisitor mv, Class<?> cl) {
             mv.visitLdcInsn(cl.getName());
+            mv.visitInsn(ICONST_0); // false
+            mv.visitVarInsn(ALOAD, 0); // classLoader
             mv.visitMethodInsn(INVOKESTATIC,
                     JL_CLASS,
-                    "forName", "(Ljava/lang/String;)Ljava/lang/Class;", false);
+                    "forName",
+                    "(Ljava/lang/String;Z" + LJL_CLASSLOADER + ")Ljava/lang/Class;",
+                    false);
         }
 
         /**

test/jdk/java/lang/reflect/Proxy/LazyInitializationTest.java

@@ -0,0 +1,58 @@
+/*
+ * 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.Proxy;
+
+import org.testng.Assert;
+import org.testng.annotations.Test;
+
+/*
+ * @test
+ * @bug 8285401
+ * @summary Avoid initialization of parameter types in proxy construction
+ * @run testng LazyInitializationTest
+ */
+public final class LazyInitializationTest {
+    private static volatile boolean initialized = false;
+
+    interface Intf {
+        void m(Parameter parameter);
+    }
+
+    static class Parameter {
+        static {
+            initialized = true;
+        }
+    }
+
+    @Test
+    public void testLazyInitialization() {
+        Intf value = (Intf) Proxy.newProxyInstance(LazyInitializationTest.class.getClassLoader(),
+                new Class<?>[]{ Intf.class },
+                (proxy, method, args) -> null);
+        Assert.assertFalse(initialized, "parameter type initialized unnecessarily");
+
+        value.m(new Parameter());
+        Assert.assertTrue(initialized, "parameter type initialized after instantiation");
+    }
+}