[jboss-jira] [JBoss JIRA] Commented: (JASSIST-61) clone on a member array causes an NPE in MemberResolver when instrumenting

clone on a member array causes an NPE in MemberResolver when instrumenting -------------------------------------------------------------------------- Key: JASSIST-61 URL: http://jira.jboss.com/jira/browse/JASSIST-61 Project: Javassist Issue Type: Bug Environment: Javassist 3.7.1 (latest from cvs HEAD) Eclipse Version: 3.3.1.1, Build id: M20071023-1652 running in the JRE included with JDK1.6.0_03 on winXP and compiler compliance set to 5.0. Show » Javassist 3.7.1 (latest from cvs HEAD) Eclipse Version: 3.3.1.1, Build id: M20071023-1652 running in the JRE included with JDK1.6.0_03 on winXP and compiler compliance set to 5.0. Reporter: Yanic Inghelbrecht Assigned To: Shigeru Chiba In the instrumentation of JHotDraw, I encountered an NPE in javassist.compiler.MemberResolver#lookupMethod(...). When replacing a method call with a trivial block, a null pointer exception occurs in MemberResolver if that method calls clone() on a member array. The method that is being looked up is the clone method. The simplest testcase to reproduce this bug consists of two classes : Client (to be instrumented) and Main (does the instrumentation). It produces the following stack trace : Exception in thread "main" java.lang.ClassNotFoundException: caught an exception while obtaining a class file for test_clone_member_array.Client at javassist.Loader.findClass(Loader.java:359) at javassist.Loader.loadClass(Loader.java:311) at java.lang.ClassLoader.loadClass(Unknown Source) at test_clone_member_array.Main.main(Main.java:25) Caused by: java.lang.NullPointerException at javassist.compiler.MemberResolver.lookupMethod(MemberResolver.java:110) at javassist.compiler.MemberResolver.lookupMethod(MemberResolver.java:96) at javassist.compiler.TypeChecker.atMethodCallCore(TypeChecker.java:704) at javassist.compiler.TypeChecker.atCallExpr(TypeChecker.java:681) at javassist.compiler.JvstTypeChecker.atCallExpr(JvstTypeChecker.java:156) at javassist.compiler.ast.CallExpr.accept(CallExpr.java:45) at javassist.compiler.Javac$1.setReturnType(Javac.java:459) at javassist.compiler.JvstTypeChecker.atCallExpr(JvstTypeChecker.java:146) at javassist.compiler.ast.CallExpr.accept(CallExpr.java:45) at javassist.compiler.TypeChecker.atVariableAssign(TypeChecker.java:248) at javassist.compiler.TypeChecker.atAssignExpr(TypeChecker.java:217) at javassist.compiler.ast.AssignExpr.accept(AssignExpr.java:38) at javassist.compiler.CodeGen.doTypeCheck(CodeGen.java:241) at javassist.compiler.CodeGen.atStmnt(CodeGen.java:329) at javassist.compiler.ast.Stmnt.accept(Stmnt.java:49) at javassist.compiler.CodeGen.atStmnt(CodeGen.java:350) at javassist.compiler.ast.Stmnt.accept(Stmnt.java:49) at javassist.compiler.Javac.compileStmnt(Javac.java:568) at javassist.expr.MethodCall.replace(MethodCall.java:234) at test_clone_member_array.Main$MyTranslator.edit(Main.java:48) at javassist.expr.ExprEditor.loopBody(ExprEditor.java:191) at javassist.expr.ExprEditor.doit(ExprEditor.java:90) at javassist.CtBehavior.instrument(CtBehavior.java:548) at test_clone_member_array.Main$MyTranslator.modify(Main.java:40) at test_clone_member_array.Main$MyTranslator.onLoad(Main.java:35) at javassist.Loader.findClass(Loader.java:340) ... 3 more The source code for this testcase : // ----- file Client.java package test_clone_member_array; public class Client { private Object[] oa; public void test() throws Exception { this.oa.clone(); } } // ----- file Main.java package test_clone_member_array; import javassist.CannotCompileException; import javassist.ClassPool; import javassist.CtClass; import javassist.CtMethod; import javassist.Loader; import javassist.NotFoundException; import javassist.Translator; import javassist.expr.ExprEditor; import javassist.expr.MethodCall; public class Main { public static void main(String[] args) throws Exception { ClassPool pool = new ClassPool(true); Loader cl = new Loader(); try { cl.addTranslator(pool, new MyTranslator()); } catch (Exception e) { e.printStackTrace(); return; } // load the Client class Class clientClass=cl.loadClass("test_clone_member_array.Client"); // create an instance Object client=clientClass.newInstance(); } static public class MyTranslator extends ExprEditor implements Translator { public void onLoad(ClassPool pool, String classname) throws NotFoundException, CannotCompileException { CtClass cc = pool.get(classname); modify(cc); } public void modify(CtClass c) throws CannotCompileException { for (CtMethod m : c.getMethods()) { m.instrument(this); } } @Override public void edit(MethodCall mc) throws CannotCompileException { // no changes, for simplicity's sake String block = "{$_=$proceed($$);}"; mc.replace(block); } public void start(ClassPool pool) throws NotFoundException, CannotCompileException { // do nothing } } } I hope it's an easy fix for you, I did not find a usable workaround. Thanks in advance. Best regards, Yanic