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1
19
20 package edu.umd.cs.findbugs.detect;
21
22
23 import edu.umd.cs.findbugs.*;
24 import edu.umd.cs.findbugs.ba.*;
25 import java.io.*;
26 import java.util.*;
27
28 import org.apache.bcel.classfile.Code;
29
30
31 public class SwitchFallthrough extends BytecodeScanningDetector implements StatelessDetector {
32 private static final boolean DEBUG = SystemProperties.getBoolean("switchFallthrough.debug");
33 private static final boolean LOOK_IN_SOURCE_FOR_FALLTHRU_COMMENT =
34 SystemProperties.getBoolean("findbugs.sf.comment");
35
36 private SwitchHandler switchHdlr;
37 private boolean reachable;
38 private BugReporter bugReporter;
39 private int lastPC;
40 private BitSet potentiallyDeadStores = new BitSet();
41 private BitSet potentiallyDeadStoresFromBeforeFallthrough = new BitSet();
42 private LocalVariableAnnotation deadStore = null;
43 private int priority;
44 private int fallthroughDistance;
45
46 public SwitchFallthrough(BugReporter bugReporter) {
47 this.bugReporter = bugReporter;
48 }
49
50
51
52 @Override 
53 public void visitClassContext(ClassContext classContext) {
54 classContext.getJavaClass().accept(this);
55 }
56
57 Collection<SourceLineAnnotation> found = new LinkedList<SourceLineAnnotation>();
58
59 @Override
60 public void visit(Code obj) {
61 reachable = false;
62 lastPC = 0;
63 found.clear();
64 switchHdlr = new SwitchHandler();
65 potentiallyDeadStores.clear();
66 deadStore = null;
67 potentiallyDeadStoresFromBeforeFallthrough.clear();
68 priority = NORMAL_PRIORITY;
69 fallthroughDistance = 1000;
70 super.visit(obj);
71 if (!found.isEmpty() && found.size() < 4) {
72 BugInstance bug = new BugInstance(this, "SF_SWITCH_FALLTHROUGH", priority)
73 .addClassAndMethod(this).addAnnotations(found);
74 bugReporter.reportBug(bug);
75
76 }
77 }
78
79 @Override
80 public void sawOpcode(int seen) {
81 if (reachable && switchHdlr.isOnSwitchOffset(this)) {
82 fallthroughDistance = 0;
83 potentiallyDeadStoresFromBeforeFallthrough = (BitSet) potentiallyDeadStores.clone();
84 if (!hasFallThruComment(lastPC + 1, getPC() - 1)) {
85 SourceLineAnnotation sourceLineAnnotation =
86 SourceLineAnnotation.fromVisitedInstructionRange(getClassContext(), this, lastPC, getPC());
87 if (sourceLineAnnotation != null) {
88 found.add(sourceLineAnnotation);
89 }
90 }
91
92 }
93
94 if (isBranch(seen) || isSwitch(seen)
95 || seen == GOTO || seen == ARETURN || seen == IRETURN || seen == RETURN || seen == LRETURN
96 || seen == DRETURN || seen == FRETURN) {
97 potentiallyDeadStores.clear();
98 potentiallyDeadStoresFromBeforeFallthrough.clear();
99 }
100
101
102 if (isRegisterLoad())
103 potentiallyDeadStores.clear(getRegisterOperand());
104
105 else if (isRegisterStore() && !atCatchBlock()) {
106 int register = getRegisterOperand();
107 if (potentiallyDeadStores.get(register) && (potentiallyDeadStoresFromBeforeFallthrough.get(register))){
108 priority = HIGH_PRIORITY;
110 deadStore = LocalVariableAnnotation.getLocalVariableAnnotation(getMethod(), register, getPC()-1, getPC());
111 BugInstance bug = new BugInstance(this, "SF_DEAD_STORE_DUE_TO_SWITCH_FALLTHROUGH", priority)
112 .addClassAndMethod(this).add(deadStore).addSourceLine(this);
113 bugReporter.reportBug(bug);
114
115 }
116 potentiallyDeadStores.set(register);
117 }
118
119 switch (seen) {
120 case TABLESWITCH:
121 case LOOKUPSWITCH:
122 reachable = false;
123 switchHdlr.enterSwitch(this);
124 break;
125
126 case ATHROW:
127 case RETURN:
128 case ARETURN:
129 case IRETURN:
130 case LRETURN:
131 case DRETURN:
132 case FRETURN:
133 case GOTO_W:
134 case GOTO:
135 reachable = false;
136 break;
137
138 case INVOKESTATIC:
139 reachable = !("exit".equals(getNameConstantOperand()) && "java/lang/System".equals(getClassConstantOperand()));
140 break;
141
142 default:
143 reachable = true;
144 }
145
146 lastPC = getPC();
147 fallthroughDistance++;
148 }
149
150 private boolean hasFallThruComment( int startPC, int endPC ) {
151 if (LOOK_IN_SOURCE_FOR_FALLTHRU_COMMENT) {
152 BufferedReader r = null;
153 try {
154 SourceLineAnnotation srcLine
155 = SourceLineAnnotation.fromVisitedInstructionRange(this, lastPC, getPC());
156 SourceFinder sourceFinder = AnalysisContext.currentAnalysisContext().getSourceFinder();
157 SourceFile sourceFile = sourceFinder.findSourceFile(srcLine.getPackageName(), srcLine.getSourceFile());
158
159 int startLine = srcLine.getStartLine();
160 int numLines = srcLine.getEndLine() - startLine - 1;
161 if (numLines <= 0)
162 return false;
163 r = new BufferedReader(
164 new InputStreamReader(sourceFile.getInputStream()));
165 for (int i = 0; i < startLine; i++) {
166 String line = r.readLine();
167 if (line == null) return false;
168 }
169 for (int i = 0; i < numLines; i++) {
170 String line = r.readLine();
171 if (line == null) return false;
172 line = line.toLowerCase();
173 if (line.indexOf("fall") >= 0 || line.indexOf("nobreak") >= 0) {
174 return true;
175 }
176 }
177 }
178 catch (IOException ioe) {
179 }
181 finally {
182 try {
183 if (r != null)
184 r.close();
185 } catch (IOException ioe) {
186 }
187 }
188 }
189 return false;
190 }
191 }
192 |
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