1 //===--- CloneChecker.cpp - Clone detection checker -------------*- C++ -*-===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 ///
9 /// \file
10 /// CloneChecker is a checker that reports clones in the current translation
11 /// unit.
12 ///
13 //===----------------------------------------------------------------------===//
14
15 #include "clang/StaticAnalyzer/Checkers/BuiltinCheckerRegistration.h"
16 #include "clang/Analysis/CloneDetection.h"
17 #include "clang/Basic/Diagnostic.h"
18 #include "clang/StaticAnalyzer/Core/BugReporter/BugType.h"
19 #include "clang/StaticAnalyzer/Core/Checker.h"
20 #include "clang/StaticAnalyzer/Core/CheckerManager.h"
21 #include "clang/StaticAnalyzer/Core/PathSensitive/AnalysisManager.h"
22 #include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h"
23
24 using namespace clang;
25 using namespace ento;
26
27 namespace {
28 class CloneChecker
29 : public Checker<check::ASTCodeBody, check::EndOfTranslationUnit> {
30 public:
31 // Checker options.
32 int MinComplexity;
33 bool ReportNormalClones = false;
34 StringRef IgnoredFilesPattern;
35
36 private:
37 mutable CloneDetector Detector;
38 const BugType BT_Exact{this, "Exact code clone", "Code clone"};
39 const BugType BT_Suspicious{this, "Suspicious code clone", "Code clone"};
40
41 public:
42 void checkASTCodeBody(const Decl *D, AnalysisManager &Mgr,
43 BugReporter &BR) const;
44
45 void checkEndOfTranslationUnit(const TranslationUnitDecl *TU,
46 AnalysisManager &Mgr, BugReporter &BR) const;
47
48 /// Reports all clones to the user.
49 void reportClones(BugReporter &BR, AnalysisManager &Mgr,
50 std::vector<CloneDetector::CloneGroup> &CloneGroups) const;
51
52 /// Reports only suspicious clones to the user along with information
53 /// that explain why they are suspicious.
54 void reportSuspiciousClones(
55 BugReporter &BR, AnalysisManager &Mgr,
56 std::vector<CloneDetector::CloneGroup> &CloneGroups) const;
57 };
58 } // end anonymous namespace
59
checkASTCodeBody(const Decl * D,AnalysisManager & Mgr,BugReporter & BR) const60 void CloneChecker::checkASTCodeBody(const Decl *D, AnalysisManager &Mgr,
61 BugReporter &BR) const {
62 // Every statement that should be included in the search for clones needs to
63 // be passed to the CloneDetector.
64 Detector.analyzeCodeBody(D);
65 }
66
checkEndOfTranslationUnit(const TranslationUnitDecl * TU,AnalysisManager & Mgr,BugReporter & BR) const67 void CloneChecker::checkEndOfTranslationUnit(const TranslationUnitDecl *TU,
68 AnalysisManager &Mgr,
69 BugReporter &BR) const {
70 // At this point, every statement in the translation unit has been analyzed by
71 // the CloneDetector. The only thing left to do is to report the found clones.
72
73 // Let the CloneDetector create a list of clones from all the analyzed
74 // statements. We don't filter for matching variable patterns at this point
75 // because reportSuspiciousClones() wants to search them for errors.
76 std::vector<CloneDetector::CloneGroup> AllCloneGroups;
77
78 Detector.findClones(
79 AllCloneGroups, FilenamePatternConstraint(IgnoredFilesPattern),
80 RecursiveCloneTypeIIHashConstraint(), MinGroupSizeConstraint(2),
81 MinComplexityConstraint(MinComplexity),
82 RecursiveCloneTypeIIVerifyConstraint(), OnlyLargestCloneConstraint());
83
84 reportSuspiciousClones(BR, Mgr, AllCloneGroups);
85
86 // We are done for this translation unit unless we also need to report normal
87 // clones.
88 if (!ReportNormalClones)
89 return;
90
91 // Now that the suspicious clone detector has checked for pattern errors,
92 // we also filter all clones who don't have matching patterns
93 CloneDetector::constrainClones(AllCloneGroups,
94 MatchingVariablePatternConstraint(),
95 MinGroupSizeConstraint(2));
96
97 reportClones(BR, Mgr, AllCloneGroups);
98 }
99
makeLocation(const StmtSequence & S,AnalysisManager & Mgr)100 static PathDiagnosticLocation makeLocation(const StmtSequence &S,
101 AnalysisManager &Mgr) {
102 ASTContext &ACtx = Mgr.getASTContext();
103 return PathDiagnosticLocation::createBegin(
104 S.front(), ACtx.getSourceManager(),
105 Mgr.getAnalysisDeclContext(ACtx.getTranslationUnitDecl()));
106 }
107
reportClones(BugReporter & BR,AnalysisManager & Mgr,std::vector<CloneDetector::CloneGroup> & CloneGroups) const108 void CloneChecker::reportClones(
109 BugReporter &BR, AnalysisManager &Mgr,
110 std::vector<CloneDetector::CloneGroup> &CloneGroups) const {
111 for (const CloneDetector::CloneGroup &Group : CloneGroups) {
112 // We group the clones by printing the first as a warning and all others
113 // as a note.
114 auto R = std::make_unique<BasicBugReport>(
115 BT_Exact, "Duplicate code detected", makeLocation(Group.front(), Mgr));
116 R->addRange(Group.front().getSourceRange());
117
118 for (unsigned i = 1; i < Group.size(); ++i)
119 R->addNote("Similar code here", makeLocation(Group[i], Mgr),
120 Group[i].getSourceRange());
121 BR.emitReport(std::move(R));
122 }
123 }
124
reportSuspiciousClones(BugReporter & BR,AnalysisManager & Mgr,std::vector<CloneDetector::CloneGroup> & CloneGroups) const125 void CloneChecker::reportSuspiciousClones(
126 BugReporter &BR, AnalysisManager &Mgr,
127 std::vector<CloneDetector::CloneGroup> &CloneGroups) const {
128 std::vector<VariablePattern::SuspiciousClonePair> Pairs;
129
130 for (const CloneDetector::CloneGroup &Group : CloneGroups) {
131 for (unsigned i = 0; i < Group.size(); ++i) {
132 VariablePattern PatternA(Group[i]);
133
134 for (unsigned j = i + 1; j < Group.size(); ++j) {
135 VariablePattern PatternB(Group[j]);
136
137 VariablePattern::SuspiciousClonePair ClonePair;
138 // For now, we only report clones which break the variable pattern just
139 // once because multiple differences in a pattern are an indicator that
140 // those differences are maybe intended (e.g. because it's actually a
141 // different algorithm).
142 // FIXME: In very big clones even multiple variables can be unintended,
143 // so replacing this number with a percentage could better handle such
144 // cases. On the other hand it could increase the false-positive rate
145 // for all clones if the percentage is too high.
146 if (PatternA.countPatternDifferences(PatternB, &ClonePair) == 1) {
147 Pairs.push_back(ClonePair);
148 break;
149 }
150 }
151 }
152 }
153
154 ASTContext &ACtx = BR.getContext();
155 SourceManager &SM = ACtx.getSourceManager();
156 AnalysisDeclContext *ADC =
157 Mgr.getAnalysisDeclContext(ACtx.getTranslationUnitDecl());
158
159 for (VariablePattern::SuspiciousClonePair &Pair : Pairs) {
160 // FIXME: We are ignoring the suggestions currently, because they are
161 // only 50% accurate (even if the second suggestion is unavailable),
162 // which may confuse the user.
163 // Think how to perform more accurate suggestions?
164
165 auto R = std::make_unique<BasicBugReport>(
166 BT_Suspicious,
167 "Potential copy-paste error; did you really mean to use '" +
168 Pair.FirstCloneInfo.Variable->getNameAsString() + "' here?",
169 PathDiagnosticLocation::createBegin(Pair.FirstCloneInfo.Mention, SM,
170 ADC));
171 R->addRange(Pair.FirstCloneInfo.Mention->getSourceRange());
172
173 R->addNote("Similar code using '" +
174 Pair.SecondCloneInfo.Variable->getNameAsString() + "' here",
175 PathDiagnosticLocation::createBegin(Pair.SecondCloneInfo.Mention,
176 SM, ADC),
177 Pair.SecondCloneInfo.Mention->getSourceRange());
178
179 BR.emitReport(std::move(R));
180 }
181 }
182
183 //===----------------------------------------------------------------------===//
184 // Register CloneChecker
185 //===----------------------------------------------------------------------===//
186
registerCloneChecker(CheckerManager & Mgr)187 void ento::registerCloneChecker(CheckerManager &Mgr) {
188 auto *Checker = Mgr.registerChecker<CloneChecker>();
189
190 Checker->MinComplexity = Mgr.getAnalyzerOptions().getCheckerIntegerOption(
191 Checker, "MinimumCloneComplexity");
192
193 if (Checker->MinComplexity < 0)
194 Mgr.reportInvalidCheckerOptionValue(
195 Checker, "MinimumCloneComplexity", "a non-negative value");
196
197 Checker->ReportNormalClones = Mgr.getAnalyzerOptions().getCheckerBooleanOption(
198 Checker, "ReportNormalClones");
199
200 Checker->IgnoredFilesPattern = Mgr.getAnalyzerOptions()
201 .getCheckerStringOption(Checker, "IgnoredFilesPattern");
202 }
203
shouldRegisterCloneChecker(const CheckerManager & mgr)204 bool ento::shouldRegisterCloneChecker(const CheckerManager &mgr) {
205 return true;
206 }
207