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1 package edu.umd.cs.findbugs.detect;
2
3 import java.util.BitSet  ;
4 import java.util.IdentityHashMap ;
5 import java.util.Iterator ;
6
7 import org.apache.bcel.classfile.LineNumberTable;
8 import org.apache.bcel.classfile.Method;
9 import org.apache.bcel.generic.ALOAD;
10 import org.apache.bcel.generic.ARETURN;
11 import org.apache.bcel.generic.Instruction;
12 import org.apache.bcel.generic.InstructionHandle;
13 import org.apache.bcel.generic.MethodGen;
14
15 import edu.umd.cs.findbugs.BugInstance;
16 import edu.umd.cs.findbugs.BugReporter;
17 import edu.umd.cs.findbugs.Detector;
18 import edu.umd.cs.findbugs.SourceLineAnnotation;
19 import edu.umd.cs.findbugs.SystemProperties;
20 import edu.umd.cs.findbugs.ba.CFG;
21 import edu.umd.cs.findbugs.ba.CFGBuilderException;
22 import edu.umd.cs.findbugs.ba.ClassContext;
23 import edu.umd.cs.findbugs.ba.DataflowAnalysisException;
24 import edu.umd.cs.findbugs.ba.Location;
25 import edu.umd.cs.findbugs.ba.MethodUnprofitableException;
26 import edu.umd.cs.findbugs.ba.npe.IsNullValue;
27 import edu.umd.cs.findbugs.ba.npe.IsNullValueDataflow;
28 import edu.umd.cs.findbugs.ba.npe.IsNullValueFrame;
29
30 public class LoadOfKnownNullValue implements Detector {
31
32 private BugReporter bugReporter;
33
34 public LoadOfKnownNullValue(BugReporter bugReporter) {
35 this.bugReporter = bugReporter;
36 }
37
38 public void visitClassContext(ClassContext classContext) {
39 Method[] methodList = classContext.getJavaClass().getMethods();
40
41 for (Method method : methodList) {
42 if (method.getCode() == null)
43 continue;
44
45 try {
46 analyzeMethod(classContext, method);
47 } catch (MethodUnprofitableException mue) {
48 if (SystemProperties.getBoolean("unprofitable.debug")) bugReporter.logError("skipping unprofitable method in " + getClass().getName());
50 } catch (CFGBuilderException e) {
51 bugReporter.logError("Detector " + this.getClass().getName()
52 + " caught exception", e);
53 } catch (DataflowAnalysisException e) {
54 bugReporter.logError("Detector " + this.getClass().getName()
55 + " caught exception", e);
56 }
57 }
58 }
59
60 private void analyzeMethod(ClassContext classContext, Method method)
61 throws CFGBuilderException, DataflowAnalysisException {
62 BitSet lineMentionedMultipleTimes = ClassContext.linesMentionedMultipleTimes(method);
63 BitSet linesWithLoadsOfNotDefinitelyNullValues = null;
64
65 CFG cfg = classContext.getCFG(method);
66 IsNullValueDataflow nullValueDataflow = classContext
67 .getIsNullValueDataflow(method);
68 MethodGen methodGen = classContext.getMethodGen(method);
69 String sourceFile = classContext.getJavaClass().getSourceFileName();
70
71 if (lineMentionedMultipleTimes.cardinality() > 0) {
72 linesWithLoadsOfNotDefinitelyNullValues = new BitSet ();
73 LineNumberTable lineNumbers = method.getLineNumberTable();
74 for (Iterator <Location> i = cfg.locationIterator(); i.hasNext();) {
75 Location location = i.next();
76
77 InstructionHandle handle = location.getHandle();
78 Instruction ins = handle.getInstruction();
79 if (!(ins instanceof ALOAD))
80 continue;
81
82 IsNullValueFrame frame = nullValueDataflow
83 .getFactAtLocation(location);
84 if (!frame.isValid()) {
85 continue;
87 }
88
90 ALOAD load = (ALOAD) ins;
91
92 int index = load.getIndex();
93 IsNullValue v = frame.getValue(index);
94 if (!v.isDefinitelyNull()) {
95 int sourceLine = lineNumbers.getSourceLine(handle.getPosition());
96 if (sourceLine > 0)
97 linesWithLoadsOfNotDefinitelyNullValues.set(sourceLine);
98 }
99 }
100 }
101
102
103 IdentityHashMap <InstructionHandle, Object > sometimesGood = new IdentityHashMap <InstructionHandle, Object >();
104
105 for (Iterator <Location> i = cfg.locationIterator(); i.hasNext();) {
106 Location location = i.next();
107 InstructionHandle handle = location.getHandle();
108 Instruction ins = handle.getInstruction();
109 if (!(ins instanceof ALOAD)) continue;
110 IsNullValueFrame frame = nullValueDataflow.getFactAtLocation(location);
111 if (!frame.isValid()) {
112 continue;
114 }
115
117 ALOAD load = (ALOAD) ins;
118
119 int index = load.getIndex();
120 IsNullValue v = frame.getValue(index);
121 if (!v.isDefinitelyNull()) sometimesGood.put(handle, null);
122 }
123
124 for (Iterator <Location> i = cfg.locationIterator(); i.hasNext();) {
126 Location location = i.next();
127
128 InstructionHandle handle = location.getHandle();
129 Instruction ins = handle.getInstruction();
130 if (!(ins instanceof ALOAD))
131 continue;
132
133 if (sometimesGood.containsKey(handle)) continue;
134 IsNullValueFrame frame = nullValueDataflow
135 .getFactAtLocation(location);
136 if (!frame.isValid()) {
137 continue;
139 }
140
142 ALOAD load = (ALOAD) ins;
143
144 int index = load.getIndex();
145 IsNullValue v = frame.getValue(index);
146 if (v.isDefinitelyNull()) {
147 Instruction next = handle.getNext().getInstruction();
148 InstructionHandle prevHandle = handle.getPrev();
149 SourceLineAnnotation sourceLineAnnotation = SourceLineAnnotation
150 .fromVisitedInstruction(classContext, methodGen, sourceFile, handle);
151 SourceLineAnnotation prevSourceLineAnnotation = SourceLineAnnotation
152 .fromVisitedInstruction(classContext, methodGen, sourceFile, prevHandle);
153
154 if (next instanceof ARETURN) {
155 continue;
157 }
158 int startLine = sourceLineAnnotation.getStartLine();
159 if (startLine > 0 && lineMentionedMultipleTimes.get(startLine) && linesWithLoadsOfNotDefinitelyNullValues.get(startLine))
160 continue;
161
162 if (startLine > prevSourceLineAnnotation.getEndLine()) {
163 continue;
166 }
167 int priority = NORMAL_PRIORITY;
168
169 if (!v.isChecked()) priority++;
170
173 bugReporter.reportBug(new BugInstance(this,
174 "NP_LOAD_OF_KNOWN_NULL_VALUE",
175 priority)
176 .addClassAndMethod(methodGen, sourceFile)
177 .addSourceLine(sourceLineAnnotation));
178 }
179
180 }
181 }
182
183 public void report() {
184 }
185
186 }
187 |
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