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SpotBugs: Because it's easy!
/*
* FindBugs - Find bugs in Java programs
* Copyright (C) 2005 Jay Dunning
* Copyright (C) 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.Collection;
import java.util.LinkedList;
import java.util.Objects;
import org.apache.bcel.Const;
import org.apache.bcel.classfile.Code;
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.OpcodeStack.Item;
import edu.umd.cs.findbugs.SourceLineAnnotation;
import edu.umd.cs.findbugs.StatelessDetector;
import edu.umd.cs.findbugs.bcel.OpcodeStackDetector;
public class FindFloatEquality extends OpcodeStackDetector implements StatelessDetector {
private static final int SAW_NOTHING = 0;
private static final int SAW_COMP = 1;
private int priority;
private final BugReporter bugReporter;
private final BugAccumulator bugAccumulator;
private int state;
public FindFloatEquality(BugReporter bugReporter) {
this.bugReporter = bugReporter;
this.bugAccumulator = new BugAccumulator(bugReporter);
}
Collection found = new LinkedList<>();
@Override
public void visit(Code obj) {
found.clear();
priority = LOW_PRIORITY;
state = SAW_NOTHING;
super.visit(obj);
bugAccumulator.reportAccumulatedBugs();
if (!found.isEmpty()) {
BugInstance bug = new BugInstance(this, "FE_FLOATING_POINT_EQUALITY", priority).addClassAndMethod(this);
boolean first = true;
for (SourceLineAnnotation s : found) {
bug.add(s);
if (first) {
first = false;
} else {
bug.describe(SourceLineAnnotation.ROLE_ANOTHER_INSTANCE);
}
}
bugReporter.reportBug(bug);
found.clear();
}
}
public boolean isZero(Number n) {
if (n == null) {
return false;
}
double v = n.doubleValue();
return v == 0.0;
}
public boolean okValueToCompareAgainst(Number n) {
if (n == null) {
return false;
}
double v = n.doubleValue();
if (Double.isInfinite(v) || Double.isNaN(v)) {
return true;
}
v = v - Math.floor(v);
return v == 0.0;
}
@Override
public void sawOpcode(int seen) {
switch (seen) {
case Const.FCMPG:
case Const.FCMPL:
case Const.DCMPG:
case Const.DCMPL:
if (stack.getStackDepth() >= 2) {
OpcodeStack.Item first = stack.getStackItem(0);
OpcodeStack.Item second = stack.getStackItem(1);
if (first.getRegisterNumber() == second.getRegisterNumber() && first.getRegisterNumber() != -1) {
break;
}
if (first.isInitialParameter() && second.isInitialParameter()) {
break;
}
if (sameField(first, second)) {
break;
}
Number n1 = (Number) first.getConstant();
Number n2 = (Number) second.getConstant();
if (n1 != null && Double.isNaN(n1.doubleValue()) || n2 != null && Double.isNaN(n2.doubleValue())) {
BugInstance bug = new BugInstance(this, "FE_TEST_IF_EQUAL_TO_NOT_A_NUMBER", HIGH_PRIORITY)
.addClassAndMethod(this);
bugAccumulator.accumulateBug(bug, this);
state = SAW_NOTHING;
break;
}
if (first.getSpecialKind() == OpcodeStack.Item.NASTY_FLOAT_MATH && !isZero(n2)
|| second.getSpecialKind() == OpcodeStack.Item.NASTY_FLOAT_MATH && !isZero(n1)
|| first.getSpecialKind() == OpcodeStack.Item.FLOAT_MATH && !okValueToCompareAgainst(n2)
|| second.getSpecialKind() == OpcodeStack.Item.FLOAT_MATH && !okValueToCompareAgainst(n1)) {
if (priority != HIGH_PRIORITY) {
found.clear();
}
priority = HIGH_PRIORITY;
state = SAW_COMP;
break;
}
if (priority == HIGH_PRIORITY) {
break;
}
// if (first.isInitialParameter() && n2 != null) break;
// if (second.isInitialParameter() && n1 != null) break;
if (n1 != null && n2 != null) {
break;
}
if (okValueToCompareAgainst(n1) || okValueToCompareAgainst(n2)) {
break;
}
if (n1 != null && !second.isInitialParameter() || n2 != null && !first.isInitialParameter()) {
if (priority == LOW_PRIORITY) {
found.clear();
}
priority = NORMAL_PRIORITY;
} else if (priority == NORMAL_PRIORITY) {
break;
}
state = SAW_COMP;
}
break;
case Const.IFEQ:
case Const.IFNE:
if (state == SAW_COMP) {
SourceLineAnnotation sourceLineAnnotation = SourceLineAnnotation.fromVisitedInstruction(getClassContext(), this,
getPC());
if (sourceLineAnnotation != null) {
found.add(sourceLineAnnotation);
}
}
state = SAW_NOTHING;
break;
default:
state = SAW_NOTHING;
break;
}
}
static boolean sameField(Item i1, Item i2) {
return Objects.equals(i1.getXField(), i2.getXField())
&& i1.getFieldLoadedFromRegister() == i2.getFieldLoadedFromRegister();
}
}