test for failing synchronization in LocalVariableTable.unpack

bcel-builder/src/main/java/org/aspectj/apache/bcel/classfile/LocalVariableTable.java

@@ -63,7 +63,7 @@ import org.aspectj.apache.bcel.Constants;
 
 /**
  * This class represents collection of local variables in a method. This attribute is contained in the <em>Code</em> attribute.
- * 
+ *
  * @version $Id: LocalVariableTable.java,v 1.8 2009/09/15 19:40:12 aclement Exp $
  * @author <A HREF="mailto:markus.dahm@berlin.de">M. Dahm</A>
  * @see Code
@@ -99,7 +99,7 @@ public class LocalVariableTable extends Attribute {
 
 	/**
 	 * Construct object from file stream.
-	 * 
+	 *
 	 * @param name_index Index in constant pool
 	 * @param length Content length in bytes
 	 * @param file Input stream
@@ -117,7 +117,7 @@ public class LocalVariableTable extends Attribute {
 	/**
 	 * Called by objects that are traversing the nodes of the tree implicitely defined by the contents of a Java class. I.e., the
 	 * hierarchy of methods, fields, attributes, etc. spawns a tree of objects.
-	 * 
+	 *
 	 * @param v Visitor object
 	 */
 	@Override
@@ -128,7 +128,7 @@ public class LocalVariableTable extends Attribute {
 
 	/**
 	 * Dump local variable table attribute to file stream in binary format.
-	 * 
+	 *
 	 * @param file Output file stream
 	 * @throws IOException
 	 */
@@ -189,6 +189,11 @@ public class LocalVariableTable extends Attribute {
 		return buf.toString();
 	}
 
+	@Override
+	public Object clone() throws CloneNotSupportedException {
+		return super.clone();
+	}
+
 	/**
 	 * @return deep copy of this attribute
 	 */
@@ -223,7 +228,7 @@ public class LocalVariableTable extends Attribute {
 			dis.close();
 			data = null; // throw it away now
 		} catch (IOException e) {
-			throw new RuntimeException("Unpacking of LocalVariableTable attribute failed");
+			throw new RuntimeException("Unpacking of LocalVariableTable attribute failed", e);
 		}
 		isInPackedState = false;
 	}

bcel-builder/src/test/java/org/aspectj/apache/bcel/classfile/tests/LocalVariableTableConcurrencyTest.java

@@ -0,0 +1,94 @@
+/* *******************************************************************
+ * Copyright (c) 2004 IBM
+ * All rights reserved.
+ * This program and the accompanying materials are made available
+ * under the terms of the Eclipse Public License v1.0
+ * which accompanies this distribution and is available at
+ * http://www.eclipse.org/legal/epl-v10.html
+ *
+ * Contributors:
+ *     Andy Clement -     initial implementation
+ * ******************************************************************/
+
+package org.aspectj.apache.bcel.classfile.tests;
+
+import org.aspectj.apache.bcel.classfile.Code;
+import org.aspectj.apache.bcel.classfile.JavaClass;
+import org.aspectj.apache.bcel.classfile.LocalVariableTable;
+import org.aspectj.apache.bcel.classfile.Method;
+import org.aspectj.apache.bcel.classfile.tests.BcelTestCase;
+
+import java.util.concurrent.CountDownLatch;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.Semaphore;
+import java.util.concurrent.atomic.AtomicReference;
+
+
+public class LocalVariableTableConcurrencyTest extends BcelTestCase {
+
+	private final int nThreads = Runtime.getRuntime().availableProcessors();
+
+	private final ExecutorService[] workers = new ExecutorService[nThreads];
+
+	private LocalVariableTable reference;
+
+	protected void setUp() throws Exception {
+		super.setUp();
+		for (int i = 0; i < nThreads; i++) workers[i] = Executors.newSingleThreadExecutor();
+
+		JavaClass clazz = getClassFromJar("SimpleGenericsProgram");
+
+		Method mainMethod = getMethod(clazz,"main");
+		Code codeAttr = (Code) findAttribute("Code",mainMethod.getAttributes());
+
+		reference =
+				(LocalVariableTable) findAttribute("LocalVariableTable",codeAttr.getAttributes());
+	}
+
+	private LocalVariableTable createReferenceCopy() {
+		try {
+			return (LocalVariableTable) reference.clone();
+		} catch (CloneNotSupportedException e) {
+			throw new RuntimeException("Faileed to clone LocalVariableTable", e);
+		}
+	}
+
+	public void testLocalVariableTableAttributeConcurrency() throws RuntimeException, InterruptedException {
+		final AtomicReference<RuntimeException> error = new AtomicReference<>();
+		for (int i = 0; i < 100000; i++) {
+			LocalVariableTable sharedInstance = createReferenceCopy();
+			CountDownLatch preStart = new CountDownLatch(nThreads);
+			Semaphore start = new Semaphore(0);
+			CountDownLatch finish = new CountDownLatch(nThreads);
+
+			for (int j = 0; j < nThreads; j++) {
+				final boolean needsDelay = j > 0;
+				workers[j].execute(() -> {
+					preStart.countDown();
+					start.acquireUninterruptibly();
+					// trying to trigger concurrent unpacking - one tread should enter unpack() when other is about to leave it
+					if (needsDelay) createReferenceCopy().getTableLength();
+					try {
+						sharedInstance.getTableLength();
+					}
+					catch (RuntimeException ex) {
+						error.compareAndSet(null, ex);
+					}
+					finish.countDown();
+				});
+			}
+
+			preStart.await();
+			start.release(nThreads);
+			finish.await();
+
+			if (error.get() != null) throw error.get();
+		}
+	}
+
+	protected void tearDown() throws Exception {
+		for (int i = 0; i < nThreads; i++) if (workers[i] != null) workers[i].shutdownNow();
+		super.tearDown();
+	}
+}