8343064: ClassFormatError: Illegal class name from InnerClassLambdaMetafactory

Reviewed-by: jvernee

src/java.base/share/classes/java/lang/invoke/InnerClassLambdaMetafactory.java

@@ -185,13 +185,17 @@ import sun.invoke.util.Wrapper;
         return i < ARG_NAME_CACHE.length ? ARG_NAME_CACHE[i] :  "arg$" + (i + 1);
     }
 
-    private static String lambdaClassName(Class<?> targetClass) {
+    private static String sanitizedTargetClassName(Class<?> targetClass) {
         String name = targetClass.getName();
         if (targetClass.isHidden()) {
             // use the original class name
             name = name.replace('/', '_');
         }
-        return name.replace('.', '/').concat("$$Lambda");
+        return name.replace('.', '/');
+    }
+
+    private static String lambdaClassName(Class<?> targetClass) {
+        return sanitizedTargetClassName(targetClass).concat("$$Lambda");
     }
 
     /**
@@ -430,7 +434,7 @@ import sun.invoke.util.Wrapper;
                     public void accept(CodeBuilder cob) {
                         cob.new_(SerializationSupport.CD_SerializedLambda)
                            .dup()
-                           .ldc(classDesc(targetClass))
+                           .ldc(ClassDesc.ofInternalName(sanitizedTargetClassName(targetClass)))
                            .ldc(factoryType.returnType().getName().replace('.', '/'))
                            .ldc(interfaceMethodName)
                            .ldc(interfaceMethodType.toMethodDescriptorString())

src/java.base/share/classes/java/lang/invoke/LambdaMetafactory.java

@@ -229,6 +229,22 @@ import java.util.Objects;
  * used, but this is not compatible with some implementation techniques and
  * would complicate the work implementations must do.
  *
+ * <p>Uses besides evaluation of lambda expressions and method references are
+ * unintended.  These linkage methods may change their unspecified behaviors at
+ * any time to better suit the Java language features they were designed to
+ * support, and such changes may impact unintended uses.  Unintended uses of
+ * these linkage methods may lead to resource leaks, or other unspecified
+ * negative effects.
+ *
+ * @implNote In the reference implementation, the classes implementing the created
+ * function objects are strongly reachable from the defining class loader of the
+ * caller, like classes and interfaces in Java source code.  This technique
+ * reduces heap memory use, but as a consequence, the implementation classes can
+ * be unloaded only if the caller class can be unloaded.  In particular, if the
+ * caller is a {@linkplain MethodHandles.Lookup.ClassOption#STRONG weak hidden
+ * class}, the implementation class, a strong hidden class, may not be unloaded
+ * even if the caller may be unloaded.
+ *
  * @since 1.8
  */
 public final class LambdaMetafactory {

test/jdk/java/lang/invoke/lambda/LambdaHiddenCaller.java

@@ -0,0 +1,93 @@
+/*
+ * Copyright (c) 2024, 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.io.Serializable;
+import java.lang.invoke.MethodHandles;
+import java.lang.invoke.MethodType;
+import java.util.function.IntSupplier;
+
+import org.junit.jupiter.api.BeforeAll;
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+/*
+ * @test
+ * @bug 8343064
+ * @summary Test about when lambda caller/target class is a hidden class
+ * @run junit LambdaHiddenCaller
+ */
+public class LambdaHiddenCaller {
+    static Hooks hiddenCaller;
+
+    @BeforeAll
+    static void setup() throws Throwable {
+        byte[] bytes;
+        try (var in = LambdaHiddenCaller.class.getResourceAsStream("HiddenHooks.class")) {
+            bytes = in.readAllBytes();
+        }
+        var hiddenClassLookup = MethodHandles.lookup().defineHiddenClass(bytes, true);
+        hiddenCaller = (Hooks) hiddenClassLookup.findConstructor(hiddenClassLookup.lookupClass(), MethodType.methodType(void.class))
+                .asType(MethodType.methodType(Hooks.class)).invokeExact();
+    }
+
+    @Test
+    void testStaticMethod() {
+        var is = hiddenCaller.callStaticMethodLambda();
+        assertEquals(42, is.getAsInt());
+    }
+
+    @Test
+    void testSerializableLambda() {
+        var is = hiddenCaller.callSerializableLambda();
+        assertEquals(42, is.getAsInt());
+        assertTrue(Serializable.class.isAssignableFrom(is.getClass()));
+        // We do not guarantee serialization functionalities yet
+    }
+}
+
+/**
+ * Hooks to call hidden class methods easily.
+ */
+interface Hooks {
+    IntSupplier callStaticMethodLambda();
+
+    IntSupplier callSerializableLambda();
+}
+
+class HiddenHooks implements Hooks {
+    private static int compute() {
+        return 42;
+    }
+
+    @Override
+    public IntSupplier callStaticMethodLambda() {
+        return HiddenHooks::compute;
+    }
+
+    @Override
+    public IntSupplier callSerializableLambda() {
+        return (IntSupplier & Serializable) HiddenHooks::compute;
+    }
+}