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//===--- CloneChecker.cpp - Clone detection checker -------------*- C++ -*-===//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
/// \file
/// CloneChecker is a checker that reports clones in the current translation
/// unit.
#include "clang/StaticAnalyzer/Checkers/BuiltinCheckerRegistration.h"
#include "clang/Analysis/CloneDetection.h"
#include "clang/Basic/Diagnostic.h"
#include "clang/StaticAnalyzer/Core/BugReporter/BugType.h"
#include "clang/StaticAnalyzer/Core/Checker.h"
#include "clang/StaticAnalyzer/Core/CheckerManager.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/AnalysisManager.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h"
using namespace clang;
using namespace ento;
namespace {
class CloneChecker
: public Checker<check::ASTCodeBody, check::EndOfTranslationUnit> {
// Checker options.
int MinComplexity;
bool ReportNormalClones;
StringRef IgnoredFilesPattern;
mutable CloneDetector Detector;
mutable std::unique_ptr<BugType> BT_Exact, BT_Suspicious;
void checkASTCodeBody(const Decl *D, AnalysisManager &Mgr,
BugReporter &BR) const;
void checkEndOfTranslationUnit(const TranslationUnitDecl *TU,
AnalysisManager &Mgr, BugReporter &BR) const;
/// Reports all clones to the user.
void reportClones(BugReporter &BR, AnalysisManager &Mgr,
std::vector<CloneDetector::CloneGroup> &CloneGroups) const;
/// Reports only suspicious clones to the user along with information
/// that explain why they are suspicious.
void reportSuspiciousClones(
BugReporter &BR, AnalysisManager &Mgr,
std::vector<CloneDetector::CloneGroup> &CloneGroups) const;
} // end anonymous namespace
void CloneChecker::checkASTCodeBody(const Decl *D, AnalysisManager &Mgr,
BugReporter &BR) const {
// Every statement that should be included in the search for clones needs to
// be passed to the CloneDetector.
void CloneChecker::checkEndOfTranslationUnit(const TranslationUnitDecl *TU,
AnalysisManager &Mgr,
BugReporter &BR) const {
// At this point, every statement in the translation unit has been analyzed by
// the CloneDetector. The only thing left to do is to report the found clones.
// Let the CloneDetector create a list of clones from all the analyzed
// statements. We don't filter for matching variable patterns at this point
// because reportSuspiciousClones() wants to search them for errors.
std::vector<CloneDetector::CloneGroup> AllCloneGroups;
AllCloneGroups, FilenamePatternConstraint(IgnoredFilesPattern),
RecursiveCloneTypeIIHashConstraint(), MinGroupSizeConstraint(2),
RecursiveCloneTypeIIVerifyConstraint(), OnlyLargestCloneConstraint());
reportSuspiciousClones(BR, Mgr, AllCloneGroups);
// We are done for this translation unit unless we also need to report normal
// clones.
if (!ReportNormalClones)
// Now that the suspicious clone detector has checked for pattern errors,
// we also filter all clones who don't have matching patterns
reportClones(BR, Mgr, AllCloneGroups);
static PathDiagnosticLocation makeLocation(const StmtSequence &S,
AnalysisManager &Mgr) {
ASTContext &ACtx = Mgr.getASTContext();
return PathDiagnosticLocation::createBegin(
S.front(), ACtx.getSourceManager(),
void CloneChecker::reportClones(
BugReporter &BR, AnalysisManager &Mgr,
std::vector<CloneDetector::CloneGroup> &CloneGroups) const {
if (!BT_Exact)
BT_Exact.reset(new BugType(this, "Exact code clone", "Code clone"));
for (const CloneDetector::CloneGroup &Group : CloneGroups) {
// We group the clones by printing the first as a warning and all others
// as a note.
auto R = std::make_unique<BasicBugReport>(
*BT_Exact, "Duplicate code detected", makeLocation(Group.front(), Mgr));
for (unsigned i = 1; i < Group.size(); ++i)
R->addNote("Similar code here", makeLocation(Group[i], Mgr),
void CloneChecker::reportSuspiciousClones(
BugReporter &BR, AnalysisManager &Mgr,
std::vector<CloneDetector::CloneGroup> &CloneGroups) const {
std::vector<VariablePattern::SuspiciousClonePair> Pairs;
for (const CloneDetector::CloneGroup &Group : CloneGroups) {
for (unsigned i = 0; i < Group.size(); ++i) {
VariablePattern PatternA(Group[i]);
for (unsigned j = i + 1; j < Group.size(); ++j) {
VariablePattern PatternB(Group[j]);
VariablePattern::SuspiciousClonePair ClonePair;
// For now, we only report clones which break the variable pattern just
// once because multiple differences in a pattern are an indicator that
// those differences are maybe intended (e.g. because it's actually a
// different algorithm).
// FIXME: In very big clones even multiple variables can be unintended,
// so replacing this number with a percentage could better handle such
// cases. On the other hand it could increase the false-positive rate
// for all clones if the percentage is too high.
if (PatternA.countPatternDifferences(PatternB, &ClonePair) == 1) {
if (!BT_Suspicious)
new BugType(this, "Suspicious code clone", "Code clone"));
ASTContext &ACtx = BR.getContext();
SourceManager &SM = ACtx.getSourceManager();
AnalysisDeclContext *ADC =
for (VariablePattern::SuspiciousClonePair &Pair : Pairs) {
// FIXME: We are ignoring the suggestions currently, because they are
// only 50% accurate (even if the second suggestion is unavailable),
// which may confuse the user.
// Think how to perform more accurate suggestions?
auto R = std::make_unique<BasicBugReport>(
"Potential copy-paste error; did you really mean to use '" +
Pair.FirstCloneInfo.Variable->getNameAsString() + "' here?",
PathDiagnosticLocation::createBegin(Pair.FirstCloneInfo.Mention, SM,
R->addNote("Similar code using '" +
Pair.SecondCloneInfo.Variable->getNameAsString() + "' here",
// Register CloneChecker
void ento::registerCloneChecker(CheckerManager &Mgr) {
auto *Checker = Mgr.registerChecker<CloneChecker>();
Checker->MinComplexity = Mgr.getAnalyzerOptions().getCheckerIntegerOption(
Checker, "MinimumCloneComplexity");
if (Checker->MinComplexity < 0)
Checker, "MinimumCloneComplexity", "a non-negative value");
Checker->ReportNormalClones = Mgr.getAnalyzerOptions().getCheckerBooleanOption(
Checker, "ReportNormalClones");
Checker->IgnoredFilesPattern = Mgr.getAnalyzerOptions()
.getCheckerStringOption(Checker, "IgnoredFilesPattern");
bool ento::shouldRegisterCloneChecker(const LangOptions &LO) {
return true;