/*
* FindBugs - Find bugs in Java programs
* Copyright (C) 2003,2004 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.Collection;
import java.util.HashMap;
import java.util.Map;
import org.apache.bcel.classfile.Code;
import org.apache.bcel.classfile.Constant;
import org.apache.bcel.classfile.ConstantClass;
import org.apache.bcel.classfile.ConstantPool;
import org.apache.bcel.classfile.Field;
import org.apache.bcel.classfile.JavaClass;
import org.apache.bcel.classfile.Method;
import edu.umd.cs.findbugs.BugAccumulator;
import edu.umd.cs.findbugs.BugInstance;
import edu.umd.cs.findbugs.BugReporter;
import edu.umd.cs.findbugs.OpcodeStack;
import edu.umd.cs.findbugs.SystemProperties;
import edu.umd.cs.findbugs.ba.AnalysisContext;
import edu.umd.cs.findbugs.ba.CFG;
import edu.umd.cs.findbugs.ba.CFGBuilderException;
import edu.umd.cs.findbugs.ba.DataflowAnalysisException;
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.XField;
import edu.umd.cs.findbugs.ba.ch.Subtypes2;
import edu.umd.cs.findbugs.bcel.OpcodeStackDetector;
import edu.umd.cs.findbugs.classfile.ClassDescriptor;
import edu.umd.cs.findbugs.classfile.DescriptorFactory;
/**
* Detector for static fields of type {@link java.util.Calendar} or
* {@link java.text.DateFormat} and their subclasses. Because
* {@link java.util.Calendar} is unsafe for multithreaded use, static fields
* look suspicous. To work correctly, all access would need to be synchronized
* by the client which cannot be guaranteed.
*
* @author Daniel Schneller
*/
public class StaticCalendarDetector extends OpcodeStackDetector {
/** External Debug flag set? */
private static final boolean DEBUG = Boolean.getBoolean("debug.staticcal");
/**
* External flag to determine whether to skip the test for synchronized
* blocks (default: if a call on a static Calendar or DateFormat is detected
* inside a synchronizationb block, it will not be reported). Setting this
* to <code>true</code> will report method calls on static fields if they
* are in a synchronized block. As the check currently does not take into
* account the lock's mutex it may be useful to switch allow
*/
private static final String PROP_SKIP_SYNCHRONIZED_CHECK = "staticcal.skipsynccheck";
/** The reporter to report to */
final private BugReporter reporter;
final private BugAccumulator bugAccumulator;
/** Name of the class being inspected */
private String currentClass;
/**
* {@link org.apache.bcel.generic.ObjectType} for {@link java.util.Calendar}
*/
private final ClassDescriptor calendarType = DescriptorFactory.createClassDescriptor(java.util.Calendar.class);
/**
* {@link org.apache.bcel.generic.ObjectType} for
* {@link java.text.DateFormat}
*/
private final ClassDescriptor dateFormatType = DescriptorFactory.createClassDescriptor(java.text.DateFormat.class);
/** Stores the current method */
private Method currentMethod = null;
/** Stores current Control Flow Graph */
private CFG currentCFG;
/** Stores current LDF */
private LockDataflow currentLockDataFlow;
private Map<XField, BugInstance> pendingBugs = new HashMap<XField, BugInstance>();
/**
* Creates a new instance of this Detector.
*
* @param aReporter
* {@link BugReporter} instance to report found problems to.
*/
public StaticCalendarDetector(BugReporter aReporter) {
reporter = aReporter;
bugAccumulator = new BugAccumulator(reporter);
}
Subtypes2 subtypes2 = AnalysisContext.currentAnalysisContext().getSubtypes2();
private boolean sawDateClass;
/**
* Remembers the class name and resets temporary fields.
*/
@Override
public void visit(JavaClass someObj) {
currentClass = someObj.getClassName();
currentMethod = null;
currentCFG = null;
currentLockDataFlow = null;
sawDateClass = false;
}
@Override
public void visit(ConstantPool pool) {
for (Constant constant : pool.getConstantPool()) {
if (constant instanceof ConstantClass) {
ConstantClass cc = (ConstantClass) constant;
String className = cc.getBytes(pool);
if (className.equals("java/util/Calendar") || className.equals("java/text/DateFormat"))
sawDateClass = true;
}
}
}
/**
* Checks if the visited field is of type {@link java.util.Calendar} or
* {@link java.text.DateFormat} or a subclass of either one. If so and the
* field is static and non-private it is suspicious and will be reported.
*/
@Override
public void visit(Field aField) {
if (aField.isPrivate()) {
/*
* private fields are harmless, as long as they are used correctly
* inside their own class. This should be something the rest of this
* detector can find out, so do not report them, they might be false
* positives.
*/
return;
}
String superclassName = getSuperclassName();
if (!aField.isStatic() && !superclassName.equals("java/lang/Enum"))
return;
if (!aField.isPublic() && !aField.isProtected())
return;
ClassDescriptor classOfField = DescriptorFactory.createClassDescriptorFromFieldSignature(aField.getSignature());
String tBugType = null;
int priority = aField.isPublic() && aField.isFinal() && aField.getName().equals(aField.getName().toUpperCase())
&& getThisClass().isPublic() ? HIGH_PRIORITY : NORMAL_PRIORITY;
if (classOfField != null)
try {
if (subtypes2.isSubtype(classOfField, calendarType)) {
tBugType = "STCAL_STATIC_CALENDAR_INSTANCE";
priority++;
} else if (subtypes2.isSubtype(classOfField, dateFormatType)) {
tBugType = "STCAL_STATIC_SIMPLE_DATE_FORMAT_INSTANCE";
}
if (getClassContext().getXClass().usesConcurrency())
priority--;
if (tBugType != null) {
pendingBugs.put(getXField(), new BugInstance(this, tBugType, priority).addClass(currentClass).addField(this));
}
} catch (ClassNotFoundException e) {
AnalysisContext.reportMissingClass(e);
}
}
/*
* (non-Javadoc)
*
* @see
* edu.umd.cs.findbugs.visitclass.BetterVisitor#visitMethod(org.apache.bcel
* .classfile.Method)
*/
@Override
public void visitMethod(Method obj) {
if (sawDateClass)
try {
super.visitMethod(obj);
currentMethod = obj;
currentLockDataFlow = getClassContext().getLockDataflow(currentMethod);
currentCFG = getClassContext().getCFG(currentMethod);
} catch (CFGBuilderException e) {
reporter.logError("Synchronization check in Static Calendar Detector caught an error.", e);
} catch (DataflowAnalysisException e) {
reporter.logError("Synchronization check in Static Calendar Detector caught an error.", e);
}
}
@Override
public void visit(Code obj) {
if (sawDateClass) {
super.visit(obj);
bugAccumulator.reportAccumulatedBugs();
}
}
/**
* Checks for method invocations (
* {@link org.apache.bcel.generic.INVOKEVIRTUAL}) call on a static
* {@link java.util.Calendar} or {@link java.text.DateFormat} fields. The
* {@link OpcodeStack} is used to determine if an invocation is done on such
* a static field.
*
* @param seen
* An opcode to be analyzed
* @see edu.umd.cs.findbugs.visitclass.DismantleBytecode#sawOpcode(int)
*/
@Override
public void sawOpcode(int seen) {
if (seen == GETSTATIC) {
XField f = getXFieldOperand();
if (pendingBugs.containsKey(f)) {
if (!isLocked()) {
reporter.reportBug(pendingBugs.remove(f));
}
}
}
// we are only interested in method calls
if (seen != INVOKEVIRTUAL) {
return;
}
try {
String className = getClassConstantOperand();
if (className.startsWith("[")) {
// Ignore array classes
return;
}
ClassDescriptor cDesc = DescriptorFactory.createClassDescriptor(className);
// if it is not compatible with Calendar or DateFormat, we are not
// interested anymore
boolean isCalendar = subtypes2.isSubtype(cDesc, calendarType);
boolean isDateFormat = subtypes2.isSubtype(cDesc, dateFormatType);
if (!isCalendar && !isDateFormat) {
return;
}
// determine the number of arguments the method expects
int numArguments = getNumberArguments(getSigConstantOperand());
// go back on the stack to find what the receiver of the method is
OpcodeStack.Item invokedOn = stack.getStackItem(numArguments);
XField field = invokedOn.getXField();
// find out, if the field is static. if not, we are not interested
// anymore
if (field == null || !field.isStatic()) {
return;
}
if (getMethodName().equals("<clinit>") && field.getClassName().equals(getDottedClassName()))
return;
String invokedName = getNameConstantOperand();
if (invokedName.startsWith("get"))
return;
if (invokedName.equals("equals") && numArguments == 1) {
OpcodeStack.Item passedAsArgument = stack.getStackItem(0);
field = passedAsArgument.getXField();
if (field == null || !field.isStatic()) {
return;
}
}
if (!SystemProperties.getBoolean(PROP_SKIP_SYNCHRONIZED_CHECK)) {
// check synchronization
if (isLocked())
return;
}
// if we get here, we want to generate a report, depending on the
// type
String tBugType;
if (isCalendar) {
tBugType = "STCAL_INVOKE_ON_STATIC_CALENDAR_INSTANCE";
} else if (isDateFormat) {
tBugType = "STCAL_INVOKE_ON_STATIC_DATE_FORMAT_INSTANCE";
} else
throw new IllegalStateException("Not possible");
int priority;
if (amVisitingMainMethod())
priority = LOW_PRIORITY;
else {
if (getClassContext().getXClass().usesConcurrency())
priority = NORMAL_PRIORITY;
else
priority = LOW_PRIORITY;
if (invokedName.startsWith("set") || invokedName.equals("format") || invokedName.equals("add")
|| invokedName.equals("clear") || invokedName.equals("parse") || invokedName.equals("applyPattern"))
priority--;
}
bugAccumulator.accumulateBug(new BugInstance(this, tBugType, priority).addClassAndMethod(this).addCalledMethod(this)
.addOptionalField(field), this);
} catch (ClassNotFoundException e) {
AnalysisContext.reportMissingClass(e);
}
}
/**
* @param isLocked
* @return
*/
private boolean isLocked() {
try {
if (currentMethod != null && currentLockDataFlow != null && currentCFG != null) {
Collection<Location> tLocations = currentCFG.getLocationsContainingInstructionWithOffset(getPC());
for (Location tLoc : tLocations) {
LockSet lockSet = currentLockDataFlow.getFactAtLocation(tLoc);
if (lockSet.getNumLockedObjects() > 0) {
// within a synchronized block
return true;
}
}
}
} catch (DataflowAnalysisException e) {
reporter.logError("Synchronization check in Static Calendar Detector caught an error.", e);
}
return false;
}
}