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
24using namespace clang;
25using namespace ento;
26
27namespace {
28class CloneChecker
29 : public Checker<check::ASTCodeBody, check::EndOfTranslationUnit> {
30public:
31 // Checker options.
32 int MinComplexity;
33 bool ReportNormalClones = false;
34 StringRef IgnoredFilesPattern;
35
36private:
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
41public:
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
60void 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
67void 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 Result&: AllCloneGroups, ConstraintList: FilenamePatternConstraint(IgnoredFilesPattern),
80 ConstraintList: RecursiveCloneTypeIIHashConstraint(), ConstraintList: MinGroupSizeConstraint(2),
81 ConstraintList: MinComplexityConstraint(MinComplexity),
82 ConstraintList: RecursiveCloneTypeIIVerifyConstraint(), ConstraintList: OnlyLargestCloneConstraint());
83
84 reportSuspiciousClones(BR, Mgr, CloneGroups&: 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(CloneGroups&: AllCloneGroups,
94 C: MatchingVariablePatternConstraint(),
95 ConstraintList: MinGroupSizeConstraint(2));
96
97 reportClones(BR, Mgr, CloneGroups&: AllCloneGroups);
98}
99
100static PathDiagnosticLocation makeLocation(const StmtSequence &S,
101 AnalysisManager &Mgr) {
102 ASTContext &ACtx = Mgr.getASTContext();
103 return PathDiagnosticLocation::createBegin(
104 S: S.front(), SM: ACtx.getSourceManager(),
105 LAC: Mgr.getAnalysisDeclContext(D: ACtx.getTranslationUnitDecl()));
106}
107
108void 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 args: BT_Exact, args: "Duplicate code detected", args: makeLocation(S: Group.front(), Mgr));
116 R->addRange(R: Group.front().getSourceRange());
117
118 for (unsigned i = 1; i < Group.size(); ++i)
119 R->addNote(Msg: "Similar code here", Pos: makeLocation(S: Group[i], Mgr),
120 Ranges: Group[i].getSourceRange());
121 BR.emitReport(R: std::move(R));
122 }
123}
124
125void 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(Other: PatternB, FirstMismatch: &ClonePair) == 1) {
147 Pairs.push_back(x: ClonePair);
148 break;
149 }
150 }
151 }
152 }
153
154 ASTContext &ACtx = BR.getContext();
155 SourceManager &SM = ACtx.getSourceManager();
156 AnalysisDeclContext *ADC =
157 Mgr.getAnalysisDeclContext(D: 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 args: BT_Suspicious,
167 args: "Potential copy-paste error; did you really mean to use '" +
168 Pair.FirstCloneInfo.Variable->getNameAsString() + "' here?",
169 args: PathDiagnosticLocation::createBegin(S: Pair.FirstCloneInfo.Mention, SM,
170 LAC: ADC));
171 R->addRange(R: Pair.FirstCloneInfo.Mention->getSourceRange());
172
173 R->addNote(Msg: "Similar code using '" +
174 Pair.SecondCloneInfo.Variable->getNameAsString() + "' here",
175 Pos: PathDiagnosticLocation::createBegin(S: Pair.SecondCloneInfo.Mention,
176 SM, LAC: ADC),
177 Ranges: Pair.SecondCloneInfo.Mention->getSourceRange());
178
179 BR.emitReport(R: std::move(R));
180 }
181}
182
183//===----------------------------------------------------------------------===//
184// Register CloneChecker
185//===----------------------------------------------------------------------===//
186
187void ento::registerCloneChecker(CheckerManager &Mgr) {
188 auto *Checker = Mgr.registerChecker<CloneChecker>();
189
190 Checker->MinComplexity = Mgr.getAnalyzerOptions().getCheckerIntegerOption(
191 C: Checker, OptionName: "MinimumCloneComplexity");
192
193 if (Checker->MinComplexity < 0)
194 Mgr.reportInvalidCheckerOptionValue(
195 Checker, OptionName: "MinimumCloneComplexity", ExpectedValueDesc: "a non-negative value");
196
197 Checker->ReportNormalClones = Mgr.getAnalyzerOptions().getCheckerBooleanOption(
198 C: Checker, OptionName: "ReportNormalClones");
199
200 Checker->IgnoredFilesPattern = Mgr.getAnalyzerOptions()
201 .getCheckerStringOption(C: Checker, OptionName: "IgnoredFilesPattern");
202}
203
204bool ento::shouldRegisterCloneChecker(const CheckerManager &mgr) {
205 return true;
206}
207