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1
20
21 package edu.umd.cs.findbugs.detect;
22
23 import edu.umd.cs.findbugs.*;
24 import java.util.*;
25 import org.apache.bcel.classfile.Code;
26
27 public class FindFloatEquality extends BytecodeScanningDetector implements StatelessDetector
28 {
29 private static final int SAW_NOTHING = 0;
30 private static final int SAW_COMP = 1;
31 private int priority;
32 private BugReporter bugReporter;
33 private OpcodeStack opStack = new OpcodeStack();
34 private int state;
35
36 public FindFloatEquality(BugReporter bugReporter) {
37 this.bugReporter = bugReporter;
38 }
39
40
41 Collection<SourceLineAnnotation> found = new LinkedList<SourceLineAnnotation>();
42
43 @Override 
44 public void visit(Code obj) {
45 found.clear();
46 priority = LOW_PRIORITY;
47
48
49 opStack.resetForMethodEntry(this);
50 state = SAW_NOTHING;
51
52 super.visit(obj);
53 if (!found.isEmpty()) {
54 BugInstance bug = new BugInstance(this, "FE_FLOATING_POINT_EQUALITY", priority)
55 .addClassAndMethod(this);
56
57 for(SourceLineAnnotation s : found)
58 bug.add(s);
59 bugReporter.reportBug(bug);
60
61 found.clear();
62 }
63 }
64
65 public boolean okValueToCompareAgainst(Number n) {
66 if (n == null) return false;
67 double v = n.doubleValue();
68 if (Double.isInfinite(v) || Double.isNaN(v)) return true;
69 v = v - Math.floor(v);
70 return v == 0.0;
71 }
72 @Override
73 public void sawOpcode(int seen) {
74 if (false) System.out.println(OPCODE_NAMES[seen] + " " + state);
75 opStack.mergeJumps(this);
76 try {
77 switch ( seen ) {
78 case FCMPG:
79 case FCMPL:
80 case DCMPG:
81 case DCMPL:
82 if (opStack.getStackDepth() >= 2) {
83 OpcodeStack.Item first = opStack.getStackItem(0);
84 OpcodeStack.Item second = opStack.getStackItem(1);
85
86 Number n1 = (Number )first.getConstant();
87 Number n2 = (Number )second.getConstant();
88 if (n1 != null && Double.isNaN(n1.doubleValue())
89 || n2 != null && Double.isNaN(n2.doubleValue()) ) {
90 BugInstance bug = new BugInstance(this, "FE_TEST_IF_EQUAL_TO_NOT_A_NUMBER", HIGH_PRIORITY)
91 .addClassAndMethod(this).addSourceLine(this);
92 bugReporter.reportBug(bug);
93 state = SAW_NOTHING;
94 break;
95 }
96 if (first.getSpecialKind() == OpcodeStack.Item.FLOAT_MATH && !okValueToCompareAgainst(n2)
97 || second.getSpecialKind() == OpcodeStack.Item.FLOAT_MATH && !okValueToCompareAgainst(n1)) {
98 if (priority != HIGH_PRIORITY) found.clear();
99 priority = HIGH_PRIORITY;
100 state = SAW_COMP;
101 break;
102 }
103 if (priority == HIGH_PRIORITY) break;
104 if (first.isInitialParameter() && n2 != null) break;
105 if (second.isInitialParameter() && n1 != null) break;
106 if (first.getRegisterNumber() == second.getRegisterNumber()) break;
107 if (first.isInitialParameter() && second.isInitialParameter()) break;
108 if (n1 != null && n2 != null) break;
109
110 if (okValueToCompareAgainst(n1) || okValueToCompareAgainst(n2)) break;
111 if (n1 != null || n2 != null) {
112 if (priority == LOW_PRIORITY) found.clear();
113 priority = NORMAL_PRIORITY;
114
115 }
116 else if (priority == NORMAL_PRIORITY) break;
117 state = SAW_COMP;
118 }
119 break;
120
121 case IFEQ:
122 case IFNE:
123 if (state == SAW_COMP) {
124 SourceLineAnnotation sourceLineAnnotation =
125 SourceLineAnnotation.fromVisitedInstruction(getClassContext(), this, getPC());
126 if (sourceLineAnnotation != null) {
127 found.add(sourceLineAnnotation);
128 }
129 }
130 state = SAW_NOTHING;
131 break;
132
133 default:
134 state = SAW_NOTHING;
135 break;
136 }
137 }
138 finally {
139 opStack.sawOpcode(this, seen);
140 }
141 }
142 }
143 |
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