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/*
* FindBugs - Find bugs in Java programs
* Copyright (C) 2004-2006 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.HashMap;
import java.util.LinkedList;
import java.util.Map;
import org.apache.bcel.Const;
import org.apache.bcel.classfile.Code;
import org.apache.bcel.generic.BranchInstruction;
import org.apache.bcel.generic.Instruction;
import org.apache.bcel.generic.InstructionHandle;
import org.apache.bcel.generic.MethodGen;
import org.objectweb.asm.Opcodes;
import edu.umd.cs.findbugs.BugInstance;
import edu.umd.cs.findbugs.BugReporter;
import edu.umd.cs.findbugs.SourceLineAnnotation;
import edu.umd.cs.findbugs.bcel.OpcodeStackDetector;
import edu.umd.cs.findbugs.classfile.CheckedAnalysisException;
import edu.umd.cs.findbugs.classfile.Global;
import edu.umd.cs.findbugs.detect.FindNoSideEffectMethods.MethodSideEffectStatus;
import edu.umd.cs.findbugs.detect.FindNoSideEffectMethods.NoSideEffectMethodsDatabase;
public class RepeatedConditionals extends OpcodeStackDetector {
BugReporter bugReporter;
private final NoSideEffectMethodsDatabase noSideEffectMethods;
public RepeatedConditionals(BugReporter bugReporter) {
this.bugReporter = bugReporter;
this.noSideEffectMethods = Global.getAnalysisCache().getDatabase(NoSideEffectMethodsDatabase.class);
reset();
}
@Override
public void visit(Code code) {
boolean interesting = true;
if (interesting) {
// initialize any variables we want to initialize for the method
super.visit(code); // make callbacks to sawOpcode for all opcodes
reset();
}
}
/*
* (non-Javadoc)
*
* @see edu.umd.cs.findbugs.bcel.OpcodeStackDetector#sawOpcode(int)
*/
int oldPC;
LinkedList emptyStackLocations = new LinkedList<>();
LinkedList prevOpcodeLocations = new LinkedList<>();
Map branchTargets = new HashMap<>();
@Override
public void sawBranchTo(int pc) {
branchTargets.put(getPC(), pc);
}
@Override
public void sawOpcode(int seen) {
if (hasSideEffect(seen)) {
reset();
} else if (stack.getStackDepth() == 0) {
if (emptyStackLocations.size() > 1) {
for (int n = 1; n <= emptyStackLocations.size() / 2; n++) {
int first = emptyStackLocations.get(emptyStackLocations.size() - 2 * n);
int second = emptyStackLocations.get(emptyStackLocations.size() - n);
int third = getPC();
if (third - second == second - first) {
int endOfFirstSegment = prevOpcodeLocations.get(emptyStackLocations.size() - n);
int endOfSecondSegment = oldPC;
int opcodeAtEndOfFirst = getCodeByte(endOfFirstSegment);
int opcodeAtEndOfSecond = getCodeByte(endOfSecondSegment);
if (!isBranch(opcodeAtEndOfFirst) || !isBranch(opcodeAtEndOfSecond)) {
continue;
}
if (opcodeAtEndOfFirst == Opcodes.GOTO || opcodeAtEndOfSecond == Opcodes.GOTO) {
continue;
}
if (opcodeAtEndOfFirst != opcodeAtEndOfSecond
&& !areOppositeBranches(opcodeAtEndOfFirst, opcodeAtEndOfSecond)) {
continue;
}
if (first == endOfFirstSegment) {
continue;
}
Integer firstTarget = branchTargets.get(endOfFirstSegment);
Integer secondTarget = branchTargets.get(endOfSecondSegment);
if (firstTarget == null || secondTarget == null) {
continue;
}
if (firstTarget >= second && firstTarget <= endOfSecondSegment) {
// first jumps inside second
continue;
}
boolean identicalCheck = firstTarget.equals(secondTarget) && opcodeAtEndOfFirst == opcodeAtEndOfSecond
|| (firstTarget.intValue() == getPC() && opcodeAtEndOfFirst != opcodeAtEndOfSecond);
if (!compareCode(first, endOfFirstSegment, second, endOfSecondSegment, !identicalCheck)) {
continue;
}
SourceLineAnnotation firstSourceLine = SourceLineAnnotation.fromVisitedInstructionRange(getClassContext(),
this, first, endOfFirstSegment - 1);
SourceLineAnnotation secondSourceLine = SourceLineAnnotation.fromVisitedInstructionRange(getClassContext(),
this, second, endOfSecondSegment - 1);
int priority = HIGH_PRIORITY;
if (firstSourceLine.getStartLine() == -1 || firstSourceLine.getStartLine() != secondSourceLine.getEndLine()) {
priority++;
}
if (stack.isJumpTarget(second)) {
priority++;
}
if (!identicalCheck) {
// opposite checks
priority += 2;
}
BugInstance bug = new BugInstance(this, "RpC_REPEATED_CONDITIONAL_TEST", priority).addClassAndMethod(this)
.add(firstSourceLine).add(secondSourceLine);
bugReporter.reportBug(bug);
}
}
}
emptyStackLocations.add(getPC());
prevOpcodeLocations.add(oldPC);
}
oldPC = getPC();
}
private boolean compareCode(int first, int endOfFirstSegment, int second,
int endOfSecondSegment, boolean oppositeChecks) {
if (endOfFirstSegment - first != endOfSecondSegment - second) {
return false;
}
MethodGen methodGen = null;
try {
methodGen = Global.getAnalysisCache().getMethodAnalysis(MethodGen.class, getMethodDescriptor());
} catch (CheckedAnalysisException e) {
// Ignore
}
if (methodGen == null) {
// MethodGen is absent for some reason: fallback to byte-to-byte comparison
byte[] code = getCode().getCode();
for (int i = first; i < endOfFirstSegment; i++) {
if (code[i] != code[i - first + second]) {
return false;
}
}
return true;
}
InstructionHandle firstHandle = methodGen.getInstructionList().findHandle(first);
InstructionHandle secondHandle = methodGen.getInstructionList().findHandle(second);
while (true) {
if (firstHandle == null || secondHandle == null) {
return false;
}
if (firstHandle.getPosition() >= endOfFirstSegment) {
return secondHandle.getPosition() >= endOfSecondSegment;
}
if (secondHandle.getPosition() >= endOfSecondSegment) {
return firstHandle.getPosition() >= endOfFirstSegment;
}
Instruction firstInstruction = firstHandle.getInstruction();
Instruction secondInstruction = secondHandle.getInstruction();
if (firstInstruction instanceof BranchInstruction && secondInstruction instanceof BranchInstruction) {
int firstOpcode = firstInstruction.getOpcode();
int secondOpcode = secondInstruction.getOpcode();
if (firstOpcode != secondOpcode) {
return false;
}
int firstTarget = ((BranchInstruction) firstInstruction).getTarget().getPosition();
int secondTarget = ((BranchInstruction) secondInstruction).getTarget().getPosition();
if (firstTarget == second) {
if (oppositeChecks || secondTarget <= endOfSecondSegment) {
return false;
}
} else {
if (!((firstTarget >= first && firstTarget <= endOfFirstSegment && firstTarget - first == secondTarget - second)
|| firstTarget == secondTarget)) {
return false;
}
}
} else {
if (!firstInstruction.equals(secondInstruction)) {
return false;
}
}
firstHandle = firstHandle.getNext();
secondHandle = secondHandle.getNext();
}
}
private boolean hasSideEffect(int seen) {
if (seen == Const.INVOKEVIRTUAL || seen == Const.INVOKESPECIAL || seen == Const.INVOKEINTERFACE || seen == Const.INVOKESTATIC) {
return noSideEffectMethods.is(getMethodDescriptorOperand(), MethodSideEffectStatus.SE, MethodSideEffectStatus.OBJ);
}
return isRegisterStore() || isReturn(seen) || isSwitch(seen) || seen == Const.INVOKEDYNAMIC || seen == Const.PUTFIELD
|| seen == Const.PUTSTATIC;
}
private void reset() {
emptyStackLocations.clear();
prevOpcodeLocations.clear();
branchTargets.clear();
oldPC = -1;
}
}