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+//===--- CloneDetection.cpp - Finds code clones in an AST -------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+///
+/// This file implements classes for searching and analyzing source code clones.
+///
+//===----------------------------------------------------------------------===//
+
+#include "clang/Analysis/CloneDetection.h"
+
+#include "clang/AST/DataCollection.h"
+#include "clang/AST/DeclTemplate.h"
+#include "llvm/Support/MD5.h"
+#include "llvm/Support/Path.h"
+
+using namespace clang;
+
+StmtSequence::StmtSequence(const CompoundStmt *Stmt, const Decl *D,
+ unsigned StartIndex, unsigned EndIndex)
+ : S(Stmt), D(D), StartIndex(StartIndex), EndIndex(EndIndex) {
+ assert(Stmt && "Stmt must not be a nullptr");
+ assert(StartIndex < EndIndex && "Given array should not be empty");
+ assert(EndIndex <= Stmt->size() && "Given array too big for this Stmt");
+}
+
+StmtSequence::StmtSequence(const Stmt *Stmt, const Decl *D)
+ : S(Stmt), D(D), StartIndex(0), EndIndex(0) {}
+
+StmtSequence::StmtSequence()
+ : S(nullptr), D(nullptr), StartIndex(0), EndIndex(0) {}
+
+bool StmtSequence::contains(const StmtSequence &Other) const {
+ // If both sequences reside in different declarations, they can never contain
+ // each other.
+ if (D != Other.D)
+ return false;
+
+ const SourceManager &SM = getASTContext().getSourceManager();
+
+ // Otherwise check if the start and end locations of the current sequence
+ // surround the other sequence.
+ bool StartIsInBounds =
+ SM.isBeforeInTranslationUnit(getBeginLoc(), Other.getBeginLoc()) ||
+ getBeginLoc() == Other.getBeginLoc();
+ if (!StartIsInBounds)
+ return false;
+
+ bool EndIsInBounds =
+ SM.isBeforeInTranslationUnit(Other.getEndLoc(), getEndLoc()) ||
+ Other.getEndLoc() == getEndLoc();
+ return EndIsInBounds;
+}
+
+StmtSequence::iterator StmtSequence::begin() const {
+ if (!holdsSequence()) {
+ return &S;
+ }
+ auto CS = cast<CompoundStmt>(S);
+ return CS->body_begin() + StartIndex;
+}
+
+StmtSequence::iterator StmtSequence::end() const {
+ if (!holdsSequence()) {
+ return reinterpret_cast<StmtSequence::iterator>(&S) + 1;
+ }
+ auto CS = cast<CompoundStmt>(S);
+ return CS->body_begin() + EndIndex;
+}
+
+ASTContext &StmtSequence::getASTContext() const {
+ assert(D);
+ return D->getASTContext();
+}
+
+SourceLocation StmtSequence::getBeginLoc() const {
+ return front()->getBeginLoc();
+}
+
+SourceLocation StmtSequence::getEndLoc() const { return back()->getEndLoc(); }
+
+SourceRange StmtSequence::getSourceRange() const {
+ return SourceRange(getBeginLoc(), getEndLoc());
+}
+
+void CloneDetector::analyzeCodeBody(const Decl *D) {
+ assert(D);
+ assert(D->hasBody());
+
+ Sequences.push_back(StmtSequence(D->getBody(), D));
+}
+
+/// Returns true if and only if \p Stmt contains at least one other
+/// sequence in the \p Group.
+static bool containsAnyInGroup(StmtSequence &Seq,
+ CloneDetector::CloneGroup &Group) {
+ for (StmtSequence &GroupSeq : Group) {
+ if (Seq.contains(GroupSeq))
+ return true;
+ }
+ return false;
+}
+
+/// Returns true if and only if all sequences in \p OtherGroup are
+/// contained by a sequence in \p Group.
+static bool containsGroup(CloneDetector::CloneGroup &Group,
+ CloneDetector::CloneGroup &OtherGroup) {
+ // We have less sequences in the current group than we have in the other,
+ // so we will never fulfill the requirement for returning true. This is only
+ // possible because we know that a sequence in Group can contain at most
+ // one sequence in OtherGroup.
+ if (Group.size() < OtherGroup.size())
+ return false;
+
+ for (StmtSequence &Stmt : Group) {
+ if (!containsAnyInGroup(Stmt, OtherGroup))
+ return false;
+ }
+ return true;
+}
+
+void OnlyLargestCloneConstraint::constrain(
+ std::vector<CloneDetector::CloneGroup> &Result) {
+ std::vector<unsigned> IndexesToRemove;
+
+ // Compare every group in the result with the rest. If one groups contains
+ // another group, we only need to return the bigger group.
+ // Note: This doesn't scale well, so if possible avoid calling any heavy
+ // function from this loop to minimize the performance impact.
+ for (unsigned i = 0; i < Result.size(); ++i) {
+ for (unsigned j = 0; j < Result.size(); ++j) {
+ // Don't compare a group with itself.
+ if (i == j)
+ continue;
+
+ if (containsGroup(Result[j], Result[i])) {
+ IndexesToRemove.push_back(i);
+ break;
+ }
+ }
+ }
+
+ // Erasing a list of indexes from the vector should be done with decreasing
+ // indexes. As IndexesToRemove is constructed with increasing values, we just
+ // reverse iterate over it to get the desired order.
+ for (auto I = IndexesToRemove.rbegin(); I != IndexesToRemove.rend(); ++I) {
+ Result.erase(Result.begin() + *I);
+ }
+}
+
+bool FilenamePatternConstraint::isAutoGenerated(
+ const CloneDetector::CloneGroup &Group) {
+ if (IgnoredFilesPattern.empty() || Group.empty() ||
+ !IgnoredFilesRegex->isValid())
+ return false;
+
+ for (const StmtSequence &S : Group) {
+ const SourceManager &SM = S.getASTContext().getSourceManager();
+ StringRef Filename = llvm::sys::path::filename(
+ SM.getFilename(S.getContainingDecl()->getLocation()));
+ if (IgnoredFilesRegex->match(Filename))
+ return true;
+ }
+
+ return false;
+}
+
+/// This class defines what a type II code clone is: If it collects for two
+/// statements the same data, then those two statements are considered to be
+/// clones of each other.
+///
+/// All collected data is forwarded to the given data consumer of the type T.
+/// The data consumer class needs to provide a member method with the signature:
+/// update(StringRef Str)
+namespace {
+template <class T>
+class CloneTypeIIStmtDataCollector
+ : public ConstStmtVisitor<CloneTypeIIStmtDataCollector<T>> {
+ ASTContext &Context;
+ /// The data sink to which all data is forwarded.
+ T &DataConsumer;
+
+ template <class Ty> void addData(const Ty &Data) {
+ data_collection::addDataToConsumer(DataConsumer, Data);
+ }
+
+public:
+ CloneTypeIIStmtDataCollector(const Stmt *S, ASTContext &Context,
+ T &DataConsumer)
+ : Context(Context), DataConsumer(DataConsumer) {
+ this->Visit(S);
+ }
+
+// Define a visit method for each class to collect data and subsequently visit
+// all parent classes. This uses a template so that custom visit methods by us
+// take precedence.
+#define DEF_ADD_DATA(CLASS, CODE) \
+ template <class = void> void Visit##CLASS(const CLASS *S) { \
+ CODE; \
+ ConstStmtVisitor<CloneTypeIIStmtDataCollector<T>>::Visit##CLASS(S); \
+ }
+
+#include "clang/AST/StmtDataCollectors.inc"
+
+// Type II clones ignore variable names and literals, so let's skip them.
+#define SKIP(CLASS) \
+ void Visit##CLASS(const CLASS *S) { \
+ ConstStmtVisitor<CloneTypeIIStmtDataCollector<T>>::Visit##CLASS(S); \
+ }
+ SKIP(DeclRefExpr)
+ SKIP(MemberExpr)
+ SKIP(IntegerLiteral)
+ SKIP(FloatingLiteral)
+ SKIP(StringLiteral)
+ SKIP(CXXBoolLiteralExpr)
+ SKIP(CharacterLiteral)
+#undef SKIP
+};
+} // end anonymous namespace
+
+static size_t createHash(llvm::MD5 &Hash) {
+ size_t HashCode;
+
+ // Create the final hash code for the current Stmt.
+ llvm::MD5::MD5Result HashResult;
+ Hash.final(HashResult);
+
+ // Copy as much as possible of the generated hash code to the Stmt's hash
+ // code.
+ std::memcpy(&HashCode, &HashResult,
+ std::min(sizeof(HashCode), sizeof(HashResult)));
+
+ return HashCode;
+}
+
+/// Generates and saves a hash code for the given Stmt.
+/// \param S The given Stmt.
+/// \param D The Decl containing S.
+/// \param StmtsByHash Output parameter that will contain the hash codes for
+/// each StmtSequence in the given Stmt.
+/// \return The hash code of the given Stmt.
+///
+/// If the given Stmt is a CompoundStmt, this method will also generate
+/// hashes for all possible StmtSequences in the children of this Stmt.
+static size_t
+saveHash(const Stmt *S, const Decl *D,
+ std::vector<std::pair<size_t, StmtSequence>> &StmtsByHash) {
+ llvm::MD5 Hash;
+ ASTContext &Context = D->getASTContext();
+
+ CloneTypeIIStmtDataCollector<llvm::MD5>(S, Context, Hash);
+
+ auto CS = dyn_cast<CompoundStmt>(S);
+ SmallVector<size_t, 8> ChildHashes;
+
+ for (const Stmt *Child : S->children()) {
+ if (Child == nullptr) {
+ ChildHashes.push_back(0);
+ continue;
+ }
+ size_t ChildHash = saveHash(Child, D, StmtsByHash);
+ Hash.update(
+ StringRef(reinterpret_cast<char *>(&ChildHash), sizeof(ChildHash)));
+ ChildHashes.push_back(ChildHash);
+ }
+
+ if (CS) {
+ // If we're in a CompoundStmt, we hash all possible combinations of child
+ // statements to find clones in those subsequences.
+ // We first go through every possible starting position of a subsequence.
+ for (unsigned Pos = 0; Pos < CS->size(); ++Pos) {
+ // Then we try all possible lengths this subsequence could have and
+ // reuse the same hash object to make sure we only hash every child
+ // hash exactly once.
+ llvm::MD5 Hash;
+ for (unsigned Length = 1; Length <= CS->size() - Pos; ++Length) {
+ // Grab the current child hash and put it into our hash. We do
+ // -1 on the index because we start counting the length at 1.
+ size_t ChildHash = ChildHashes[Pos + Length - 1];
+ Hash.update(
+ StringRef(reinterpret_cast<char *>(&ChildHash), sizeof(ChildHash)));
+ // If we have at least two elements in our subsequence, we can start
+ // saving it.
+ if (Length > 1) {
+ llvm::MD5 SubHash = Hash;
+ StmtsByHash.push_back(std::make_pair(
+ createHash(SubHash), StmtSequence(CS, D, Pos, Pos + Length)));
+ }
+ }
+ }
+ }
+
+ size_t HashCode = createHash(Hash);
+ StmtsByHash.push_back(std::make_pair(HashCode, StmtSequence(S, D)));
+ return HashCode;
+}
+
+namespace {
+/// Wrapper around FoldingSetNodeID that it can be used as the template
+/// argument of the StmtDataCollector.
+class FoldingSetNodeIDWrapper {
+
+ llvm::FoldingSetNodeID &FS;
+
+public:
+ FoldingSetNodeIDWrapper(llvm::FoldingSetNodeID &FS) : FS(FS) {}
+
+ void update(StringRef Str) { FS.AddString(Str); }
+};
+} // end anonymous namespace
+
+/// Writes the relevant data from all statements and child statements
+/// in the given StmtSequence into the given FoldingSetNodeID.
+static void CollectStmtSequenceData(const StmtSequence &Sequence,
+ FoldingSetNodeIDWrapper &OutputData) {
+ for (const Stmt *S : Sequence) {
+ CloneTypeIIStmtDataCollector<FoldingSetNodeIDWrapper>(
+ S, Sequence.getASTContext(), OutputData);
+
+ for (const Stmt *Child : S->children()) {
+ if (!Child)
+ continue;
+
+ CollectStmtSequenceData(StmtSequence(Child, Sequence.getContainingDecl()),
+ OutputData);
+ }
+ }
+}
+
+/// Returns true if both sequences are clones of each other.
+static bool areSequencesClones(const StmtSequence &LHS,
+ const StmtSequence &RHS) {
+ // We collect the data from all statements in the sequence as we did before
+ // when generating a hash value for each sequence. But this time we don't
+ // hash the collected data and compare the whole data set instead. This
+ // prevents any false-positives due to hash code collisions.
+ llvm::FoldingSetNodeID DataLHS, DataRHS;
+ FoldingSetNodeIDWrapper LHSWrapper(DataLHS);
+ FoldingSetNodeIDWrapper RHSWrapper(DataRHS);
+
+ CollectStmtSequenceData(LHS, LHSWrapper);
+ CollectStmtSequenceData(RHS, RHSWrapper);
+
+ return DataLHS == DataRHS;
+}
+
+void RecursiveCloneTypeIIHashConstraint::constrain(
+ std::vector<CloneDetector::CloneGroup> &Sequences) {
+ // FIXME: Maybe we can do this in-place and don't need this additional vector.
+ std::vector<CloneDetector::CloneGroup> Result;
+
+ for (CloneDetector::CloneGroup &Group : Sequences) {
+ // We assume in the following code that the Group is non-empty, so we
+ // skip all empty groups.
+ if (Group.empty())
+ continue;
+
+ std::vector<std::pair<size_t, StmtSequence>> StmtsByHash;
+
+ // Generate hash codes for all children of S and save them in StmtsByHash.
+ for (const StmtSequence &S : Group) {
+ saveHash(S.front(), S.getContainingDecl(), StmtsByHash);
+ }
+
+ // Sort hash_codes in StmtsByHash.
+ llvm::stable_sort(StmtsByHash, llvm::less_first());
+
+ // Check for each StmtSequence if its successor has the same hash value.
+ // We don't check the last StmtSequence as it has no successor.
+ // Note: The 'size - 1 ' in the condition is safe because we check for an
+ // empty Group vector at the beginning of this function.
+ for (unsigned i = 0; i < StmtsByHash.size() - 1; ++i) {
+ const auto Current = StmtsByHash[i];
+
+ // It's likely that we just found a sequence of StmtSequences that
+ // represent a CloneGroup, so we create a new group and start checking and
+ // adding the StmtSequences in this sequence.
+ CloneDetector::CloneGroup NewGroup;
+
+ size_t PrototypeHash = Current.first;
+
+ for (; i < StmtsByHash.size(); ++i) {
+ // A different hash value means we have reached the end of the sequence.
+ if (PrototypeHash != StmtsByHash[i].first) {
+ // The current sequence could be the start of a new CloneGroup. So we
+ // decrement i so that we visit it again in the outer loop.
+ // Note: i can never be 0 at this point because we are just comparing
+ // the hash of the Current StmtSequence with itself in the 'if' above.
+ assert(i != 0);
+ --i;
+ break;
+ }
+ // Same hash value means we should add the StmtSequence to the current
+ // group.
+ NewGroup.push_back(StmtsByHash[i].second);
+ }
+
+ // We created a new clone group with matching hash codes and move it to
+ // the result vector.
+ Result.push_back(NewGroup);
+ }
+ }
+ // Sequences is the output parameter, so we copy our result into it.
+ Sequences = Result;
+}
+
+void RecursiveCloneTypeIIVerifyConstraint::constrain(
+ std::vector<CloneDetector::CloneGroup> &Sequences) {
+ CloneConstraint::splitCloneGroups(
+ Sequences, [](const StmtSequence &A, const StmtSequence &B) {
+ return areSequencesClones(A, B);
+ });
+}
+
+size_t MinComplexityConstraint::calculateStmtComplexity(
+ const StmtSequence &Seq, std::size_t Limit,
+ const std::string &ParentMacroStack) {
+ if (Seq.empty())
+ return 0;
+
+ size_t Complexity = 1;
+
+ ASTContext &Context = Seq.getASTContext();
+
+ // Look up what macros expanded into the current statement.
+ std::string MacroStack =
+ data_collection::getMacroStack(Seq.getBeginLoc(), Context);
+
+ // First, check if ParentMacroStack is not empty which means we are currently
+ // dealing with a parent statement which was expanded from a macro.
+ // If this parent statement was expanded from the same macros as this
+ // statement, we reduce the initial complexity of this statement to zero.
+ // This causes that a group of statements that were generated by a single
+ // macro expansion will only increase the total complexity by one.
+ // Note: This is not the final complexity of this statement as we still
+ // add the complexity of the child statements to the complexity value.
+ if (!ParentMacroStack.empty() && MacroStack == ParentMacroStack) {
+ Complexity = 0;
+ }
+
+ // Iterate over the Stmts in the StmtSequence and add their complexity values
+ // to the current complexity value.
+ if (Seq.holdsSequence()) {
+ for (const Stmt *S : Seq) {
+ Complexity += calculateStmtComplexity(
+ StmtSequence(S, Seq.getContainingDecl()), Limit, MacroStack);
+ if (Complexity >= Limit)
+ return Limit;
+ }
+ } else {
+ for (const Stmt *S : Seq.front()->children()) {
+ Complexity += calculateStmtComplexity(
+ StmtSequence(S, Seq.getContainingDecl()), Limit, MacroStack);
+ if (Complexity >= Limit)
+ return Limit;
+ }
+ }
+ return Complexity;
+}
+
+void MatchingVariablePatternConstraint::constrain(
+ std::vector<CloneDetector::CloneGroup> &CloneGroups) {
+ CloneConstraint::splitCloneGroups(
+ CloneGroups, [](const StmtSequence &A, const StmtSequence &B) {
+ VariablePattern PatternA(A);
+ VariablePattern PatternB(B);
+ return PatternA.countPatternDifferences(PatternB) == 0;
+ });
+}
+
+void CloneConstraint::splitCloneGroups(
+ std::vector<CloneDetector::CloneGroup> &CloneGroups,
+ llvm::function_ref<bool(const StmtSequence &, const StmtSequence &)>
+ Compare) {
+ std::vector<CloneDetector::CloneGroup> Result;
+ for (auto &HashGroup : CloneGroups) {
+ // Contains all indexes in HashGroup that were already added to a
+ // CloneGroup.
+ std::vector<char> Indexes;
+ Indexes.resize(HashGroup.size());
+
+ for (unsigned i = 0; i < HashGroup.size(); ++i) {
+ // Skip indexes that are already part of a CloneGroup.
+ if (Indexes[i])
+ continue;
+
+ // Pick the first unhandled StmtSequence and consider it as the
+ // beginning
+ // of a new CloneGroup for now.
+ // We don't add i to Indexes because we never iterate back.
+ StmtSequence Prototype = HashGroup[i];
+ CloneDetector::CloneGroup PotentialGroup = {Prototype};
+ ++Indexes[i];
+
+ // Check all following StmtSequences for clones.
+ for (unsigned j = i + 1; j < HashGroup.size(); ++j) {
+ // Skip indexes that are already part of a CloneGroup.
+ if (Indexes[j])
+ continue;
+
+ // If a following StmtSequence belongs to our CloneGroup, we add it.
+ const StmtSequence &Candidate = HashGroup[j];
+
+ if (!Compare(Prototype, Candidate))
+ continue;
+
+ PotentialGroup.push_back(Candidate);
+ // Make sure we never visit this StmtSequence again.
+ ++Indexes[j];
+ }
+
+ // Otherwise, add it to the result and continue searching for more
+ // groups.
+ Result.push_back(PotentialGroup);
+ }
+
+ assert(llvm::all_of(Indexes, [](char c) { return c == 1; }));
+ }
+ CloneGroups = Result;
+}
+
+void VariablePattern::addVariableOccurence(const VarDecl *VarDecl,
+ const Stmt *Mention) {
+ // First check if we already reference this variable
+ for (size_t KindIndex = 0; KindIndex < Variables.size(); ++KindIndex) {
+ if (Variables[KindIndex] == VarDecl) {
+ // If yes, add a new occurrence that points to the existing entry in
+ // the Variables vector.
+ Occurences.emplace_back(KindIndex, Mention);
+ return;
+ }
+ }
+ // If this variable wasn't already referenced, add it to the list of
+ // referenced variables and add a occurrence that points to this new entry.
+ Occurences.emplace_back(Variables.size(), Mention);
+ Variables.push_back(VarDecl);
+}
+
+void VariablePattern::addVariables(const Stmt *S) {
+ // Sometimes we get a nullptr (such as from IfStmts which often have nullptr
+ // children). We skip such statements as they don't reference any
+ // variables.
+ if (!S)
+ return;
+
+ // Check if S is a reference to a variable. If yes, add it to the pattern.
+ if (auto D = dyn_cast<DeclRefExpr>(S)) {
+ if (auto VD = dyn_cast<VarDecl>(D->getDecl()->getCanonicalDecl()))
+ addVariableOccurence(VD, D);
+ }
+
+ // Recursively check all children of the given statement.
+ for (const Stmt *Child : S->children()) {
+ addVariables(Child);
+ }
+}
+
+unsigned VariablePattern::countPatternDifferences(
+ const VariablePattern &Other,
+ VariablePattern::SuspiciousClonePair *FirstMismatch) {
+ unsigned NumberOfDifferences = 0;
+
+ assert(Other.Occurences.size() == Occurences.size());
+ for (unsigned i = 0; i < Occurences.size(); ++i) {
+ auto ThisOccurence = Occurences[i];
+ auto OtherOccurence = Other.Occurences[i];
+ if (ThisOccurence.KindID == OtherOccurence.KindID)
+ continue;
+
+ ++NumberOfDifferences;
+
+ // If FirstMismatch is not a nullptr, we need to store information about
+ // the first difference between the two patterns.
+ if (FirstMismatch == nullptr)
+ continue;
+
+ // Only proceed if we just found the first difference as we only store
+ // information about the first difference.
+ if (NumberOfDifferences != 1)
+ continue;
+
+ const VarDecl *FirstSuggestion = nullptr;
+ // If there is a variable available in the list of referenced variables
+ // which wouldn't break the pattern if it is used in place of the
+ // current variable, we provide this variable as the suggested fix.
+ if (OtherOccurence.KindID < Variables.size())
+ FirstSuggestion = Variables[OtherOccurence.KindID];
+
+ // Store information about the first clone.
+ FirstMismatch->FirstCloneInfo =
+ VariablePattern::SuspiciousClonePair::SuspiciousCloneInfo(
+ Variables[ThisOccurence.KindID], ThisOccurence.Mention,
+ FirstSuggestion);
+
+ // Same as above but with the other clone. We do this for both clones as
+ // we don't know which clone is the one containing the unintended
+ // pattern error.
+ const VarDecl *SecondSuggestion = nullptr;
+ if (ThisOccurence.KindID < Other.Variables.size())
+ SecondSuggestion = Other.Variables[ThisOccurence.KindID];
+
+ // Store information about the second clone.
+ FirstMismatch->SecondCloneInfo =
+ VariablePattern::SuspiciousClonePair::SuspiciousCloneInfo(
+ Other.Variables[OtherOccurence.KindID], OtherOccurence.Mention,
+ SecondSuggestion);
+
+ // SuspiciousClonePair guarantees that the first clone always has a
+ // suggested variable associated with it. As we know that one of the two
+ // clones in the pair always has suggestion, we swap the two clones
+ // in case the first clone has no suggested variable which means that
+ // the second clone has a suggested variable and should be first.
+ if (!FirstMismatch->FirstCloneInfo.Suggestion)
+ std::swap(FirstMismatch->FirstCloneInfo, FirstMismatch->SecondCloneInfo);
+
+ // This ensures that we always have at least one suggestion in a pair.
+ assert(FirstMismatch->FirstCloneInfo.Suggestion);
+ }
+
+ return NumberOfDifferences;
+}
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