/*
* FindBugs - Find bugs in Java programs
* Copyright (C) 2004,2005 University of Maryland
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* This library 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
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/
package edu.umd.cs.findbugs.detect;
import java.util.BitSet;
import java.util.Iterator;
import org.apache.bcel.Constants;
import org.apache.bcel.classfile.Code;
import org.apache.bcel.classfile.JavaClass;
import org.apache.bcel.classfile.Method;
import org.apache.bcel.generic.AllocationInstruction;
import org.apache.bcel.generic.FieldInstruction;
import org.apache.bcel.generic.GETSTATIC;
import org.apache.bcel.generic.INVOKESTATIC;
import org.apache.bcel.generic.IfInstruction;
import org.apache.bcel.generic.Instruction;
import org.apache.bcel.generic.InstructionHandle;
import org.apache.bcel.generic.InvokeInstruction;
import org.apache.bcel.generic.MethodGen;
import org.apache.bcel.generic.ReturnInstruction;
import edu.umd.cs.findbugs.BugInstance;
import edu.umd.cs.findbugs.BugReporter;
import edu.umd.cs.findbugs.ByteCodePatternDetector;
import edu.umd.cs.findbugs.StatelessDetector;
import edu.umd.cs.findbugs.SystemProperties;
import edu.umd.cs.findbugs.ba.BasicBlock;
import edu.umd.cs.findbugs.ba.CFG;
import edu.umd.cs.findbugs.ba.CFGBuilderException;
import edu.umd.cs.findbugs.ba.ClassContext;
import edu.umd.cs.findbugs.ba.DataflowAnalysisException;
import edu.umd.cs.findbugs.ba.DominatorsAnalysis;
import edu.umd.cs.findbugs.ba.Hierarchy;
import edu.umd.cs.findbugs.ba.Location;
import edu.umd.cs.findbugs.ba.LockDataflow;
import edu.umd.cs.findbugs.ba.LockSet;
import edu.umd.cs.findbugs.ba.PostDominatorsAnalysis;
import edu.umd.cs.findbugs.ba.XClass;
import edu.umd.cs.findbugs.ba.XFactory;
import edu.umd.cs.findbugs.ba.XField;
import edu.umd.cs.findbugs.ba.bcp.Binding;
import edu.umd.cs.findbugs.ba.bcp.BindingSet;
import edu.umd.cs.findbugs.ba.bcp.ByteCodePattern;
import edu.umd.cs.findbugs.ba.bcp.ByteCodePatternMatch;
import edu.umd.cs.findbugs.ba.bcp.FieldVariable;
import edu.umd.cs.findbugs.ba.bcp.IfNull;
import edu.umd.cs.findbugs.ba.bcp.Load;
import edu.umd.cs.findbugs.ba.bcp.PatternElementMatch;
import edu.umd.cs.findbugs.ba.bcp.Store;
import edu.umd.cs.findbugs.ba.bcp.Wild;
import edu.umd.cs.findbugs.classfile.CheckedAnalysisException;
import edu.umd.cs.findbugs.classfile.ClassDescriptor;
import edu.umd.cs.findbugs.classfile.DescriptorFactory;
import edu.umd.cs.findbugs.classfile.Global;
/*
* Look for lazy initialization of fields which
* are not volatile. This is quite similar to checking for
* double checked locking, except that there is no lock.
*
* @author David Hovemeyer
*/
public final class LazyInit extends ByteCodePatternDetector implements StatelessDetector {
private final BugReporter bugReporter;
private static final boolean DEBUG = SystemProperties.getBoolean("lazyinit.debug");
/**
* The pattern to look for.
*/
private static ByteCodePattern pattern = new ByteCodePattern();
static {
pattern.add(new Load("f", "val").label("start")).add(new IfNull("val").label("test"))
.add(new Wild(1, 1).label("createObject").dominatedBy("test"))
.add(new Store("f", pattern.dummyVariable()).label("end").dominatedBy("createObject"));
}
public LazyInit(BugReporter bugReporter) {
this.bugReporter = bugReporter;
}
@Override
public Object clone() {
try {
return super.clone();
} catch (CloneNotSupportedException e) {
throw new AssertionError(e);
}
}
@Override
public BugReporter getBugReporter() {
return bugReporter;
}
BitSet reported = new BitSet();
@Override
public ByteCodePattern getPattern() {
return pattern;
}
@Override
public boolean prescreen(Method method, ClassContext classContext) {
if (method.getName().equals("<clinit>")) {
return false;
}
Code code = method.getCode();
if (code.getCode().length > 5000) {
return false;
}
BitSet bytecodeSet = classContext.getBytecodeSet(method);
if (bytecodeSet == null) {
return false;
}
// The pattern requires a get/put pair accessing the same field.
boolean hasGetStatic = bytecodeSet.get(Constants.GETSTATIC);
boolean hasPutStatic = bytecodeSet.get(Constants.PUTSTATIC);
if (!hasGetStatic || !hasPutStatic) {
return false;
}
// If the method is synchronized, then we'll assume that
// things are properly synchronized
if (method.isSynchronized()) {
return false;
}
reported.clear();
return true;
}
@Override
public void reportMatch(ClassContext classContext, Method method, ByteCodePatternMatch match) throws CFGBuilderException,
DataflowAnalysisException {
JavaClass javaClass = classContext.getJavaClass();
MethodGen methodGen = classContext.getMethodGen(method);
CFG cfg = classContext.getCFG(method);
// Get the variable referenced in the pattern instance.
BindingSet bindingSet = match.getBindingSet();
Binding binding = bindingSet.lookup("f");
// Look up the field as an XField.
// If it is volatile, then the instance is not a bug.
FieldVariable field = (FieldVariable) binding.getVariable();
XField xfield = Hierarchy.findXField(field.getClassName(), field.getFieldName(), field.getFieldSig(),
field.isStatic());
if (!xfield.isResolved()) {
return;
}
// XXX: for now, ignore lazy initialization of instance fields
if (!xfield.isStatic()) {
return;
}
// Definitely ignore synthetic class$ fields
if (xfield.getName().startsWith("class$") || xfield.getName().startsWith("array$")) {
if (DEBUG) {
System.out.println("Ignoring field " + xfield.getName());
}
return;
}
// Ignore non-reference fields
String signature = xfield.getSignature();
if (!signature.startsWith("[") && !signature.startsWith("L")) {
if (DEBUG) {
System.out.println("Ignoring non-reference field " + xfield.getName());
}
return;
}
// Strings are (mostly) safe to pass by data race in 1.5
if (signature.equals("Ljava/lang/String;")) {
return;
}
// GUI types should not be accessed from multiple threads
if (signature.charAt(0) == 'L') {
ClassDescriptor fieldType = DescriptorFactory.createClassDescriptorFromFieldSignature(signature);
while (fieldType != null) {
XClass fieldClass;
try {
fieldClass = Global.getAnalysisCache().getClassAnalysis(XClass.class, fieldType);
} catch (CheckedAnalysisException e) {
break;
}
String name = fieldClass.getClassDescriptor().getClassName();
if (name.startsWith("java/awt") || name.startsWith("javax/swing")) {
return;
}
if (name.equals("java/lang/Object")) {
break;
}
fieldType = fieldClass.getSuperclassDescriptor();
}
}
// Get locations matching the beginning of the object creation,
// and the final field store.
PatternElementMatch createBegin = match.getFirstLabeledMatch("createObject");
PatternElementMatch store = match.getFirstLabeledMatch("end");
PatternElementMatch test = match.getFirstLabeledMatch("test");
InstructionHandle testInstructionHandle = test.getMatchedInstructionInstructionHandle();
if (reported.get(testInstructionHandle.getPosition())) {
return;
}
// Get all blocks
//
// (1) dominated by the wildcard instruction matching
// the beginning of the instructions creating the object, and
// (2) postdominated by the field store
//
// Exception edges are not considered in computing
// dominators/postdominators.
// We will consider this to be all of the code that creates
// the object.
DominatorsAnalysis domAnalysis = classContext.getNonExceptionDominatorsAnalysis(method);
PostDominatorsAnalysis postDomAnalysis = classContext.getNonExceptionPostDominatorsAnalysis(method);
BitSet extent = domAnalysis.getAllDominatedBy(createBegin.getBasicBlock());
BitSet postDom = postDomAnalysis.getAllDominatedBy(store.getBasicBlock());
// System.out.println("Extent: " + extent);
if (DEBUG) {
System.out.println("test dominates: " + extent);
System.out.println("Field store postdominates " + postDom);
}
extent.and(postDom);
if (DEBUG) {
System.out.println("extent: " + extent);
}
// Check all instructions in the object creation extent
//
// (1) to determine the common lock set, and
// (2) to check for NEW and Invoke instructions that might create an
// object
//
// We ignore matches where a lock is held consistently,
// or if the extent does not appear to create a new object.
LockDataflow lockDataflow = classContext.getLockDataflow(method);
LockSet lockSet = null;
boolean sawNEW = false, sawINVOKE = false;
for (BasicBlock block : cfg.getBlocks(extent)) {
for (Iterator<InstructionHandle> j = block.instructionIterator(); j.hasNext();) {
InstructionHandle handle = j.next();
if (handle.equals(store.getMatchedInstructionInstructionHandle())) {
break;
}
Location location = new Location(handle, block);
// Keep track of whether we saw any instructions
// that might actually have created a new object.
Instruction ins = handle.getInstruction();
if (DEBUG) {
System.out.println(location);
}
if (ins instanceof AllocationInstruction) {
sawNEW = true;
} else if (ins instanceof InvokeInstruction) {
if (ins instanceof INVOKESTATIC
&& ((INVOKESTATIC) ins).getMethodName(classContext.getConstantPoolGen()).startsWith("new")) {
sawNEW = true;
}
sawINVOKE = true;
}
// Compute lock set intersection for all matched
// instructions.
LockSet insLockSet = lockDataflow.getFactAtLocation(location);
if (lockSet == null) {
lockSet = new LockSet();
lockSet.copyFrom(insLockSet);
} else {
lockSet.intersectWith(insLockSet);
}
}
}
if (!(sawNEW || sawINVOKE)) {
return;
}
if (lockSet == null) {
throw new IllegalStateException("lock set is null");
}
if (!lockSet.isEmpty()) {
return;
}
boolean sawGetStaticAfterPutStatic = false;
check: if (signature.startsWith("[") || signature.startsWith("L")) {
BitSet postStore = domAnalysis.getAllDominatedBy(store.getBasicBlock());
for (BasicBlock block : cfg.getBlocks(postStore)) {
for (Iterator<InstructionHandle> j = block.instructionIterator(); j.hasNext();) {
InstructionHandle handle = j.next();
InstructionHandle nextHandle = handle.getNext();
Instruction ins = handle.getInstruction();
if (ins instanceof GETSTATIC && potentialInitialization(nextHandle)) {
XField field2 = XFactory.createXField((FieldInstruction) ins, methodGen.getConstantPool());
if (xfield.equals(field2)) {
sawGetStaticAfterPutStatic = true;
break check;
}
}
}
}
}
// Compute the priority:
// - ignore lazy initialization of instance fields
// - when it's done in a public method, emit a high priority warning
// - protected or default access method, emit a medium priority
// warning
// - otherwise, low priority
if (!sawGetStaticAfterPutStatic && xfield.isVolatile()) {
return;
}
int priority = LOW_PRIORITY;
boolean isDefaultAccess = (method.getAccessFlags() & (Constants.ACC_PUBLIC | Constants.ACC_PRIVATE | Constants.ACC_PROTECTED)) == 0;
if (method.isPublic()) {
priority = NORMAL_PRIORITY;
} else if (method.isProtected() || isDefaultAccess) {
priority = NORMAL_PRIORITY;
}
if (signature.startsWith("[") || signature.startsWith("Ljava/util/")) {
priority--;
}
if (!sawNEW) {
priority++;
}
if (!sawGetStaticAfterPutStatic && priority < LOW_PRIORITY) {
priority = LOW_PRIORITY;
}
if (classContext.getXClass().usesConcurrency()) {
priority--;
}
// Report the bug.
InstructionHandle start = match.getLabeledInstruction("start");
InstructionHandle end = match.getLabeledInstruction("end");
String sourceFile = javaClass.getSourceFileName();
bugReporter.reportBug(new BugInstance(this, sawGetStaticAfterPutStatic ? "LI_LAZY_INIT_UPDATE_STATIC"
: "LI_LAZY_INIT_STATIC", priority).addClassAndMethod(methodGen, sourceFile).addField(xfield)
.describe("FIELD_ON").addSourceLine(classContext, methodGen, sourceFile, start, end));
reported.set(testInstructionHandle.getPosition());
}
private boolean potentialInitialization(InstructionHandle nextHandle) {
if (nextHandle == null) {
return true;
}
Instruction instruction = nextHandle.getInstruction();
if (instruction instanceof ReturnInstruction) {
return false;
}
if (instruction instanceof IfInstruction) {
return false;
}
return true;
}
}