#define LLVM_CLANG_AST_CLONEDETECTION_H
#include "clang/Basic/SourceLocation.h"
-#include "llvm/ADT/Hashing.h"
-#include "llvm/ADT/StringMap.h"
-
+#include "llvm/ADT/SmallVector.h"
#include <vector>
namespace clang {
class ASTContext;
class CompoundStmt;
-/// \brief Identifies a list of statements.
+/// Identifies a list of statements.
///
/// Can either identify a single arbitrary Stmt object, a continuous sequence of
/// child statements inside a CompoundStmt or no statements at all.
/// Stmt, then S is a pointer to this Stmt.
const Stmt *S;
- /// The related ASTContext for S.
- ASTContext *Context;
+ /// The declaration that contains the statements.
+ const Decl *D;
/// If EndIndex is non-zero, then S is a CompoundStmt and this StmtSequence
/// instance is representing the CompoundStmt children inside the array
unsigned EndIndex;
public:
- /// \brief Constructs a StmtSequence holding multiple statements.
+ /// Constructs a StmtSequence holding multiple statements.
///
/// The resulting StmtSequence identifies a continuous sequence of statements
/// in the body of the given CompoundStmt. Which statements of the body should
/// that describe a non-empty sub-array in the body of the given CompoundStmt.
///
/// \param Stmt A CompoundStmt that contains all statements in its body.
- /// \param Context The ASTContext for the given CompoundStmt.
+ /// \param Decl The Decl containing this Stmt.
/// \param StartIndex The inclusive start index in the children array of
/// \p Stmt
/// \param EndIndex The exclusive end index in the children array of \p Stmt.
- StmtSequence(const CompoundStmt *Stmt, ASTContext &Context,
- unsigned StartIndex, unsigned EndIndex);
+ StmtSequence(const CompoundStmt *Stmt, const Decl *D, unsigned StartIndex,
+ unsigned EndIndex);
- /// \brief Constructs a StmtSequence holding a single statement.
+ /// Constructs a StmtSequence holding a single statement.
///
/// \param Stmt An arbitrary Stmt.
- /// \param Context The ASTContext for the given Stmt.
- StmtSequence(const Stmt *Stmt, ASTContext &Context);
+ /// \param Decl The Decl containing this Stmt.
+ StmtSequence(const Stmt *Stmt, const Decl *D);
- /// \brief Constructs an empty StmtSequence.
+ /// Constructs an empty StmtSequence.
StmtSequence();
typedef const Stmt *const *iterator;
bool empty() const { return size() == 0; }
/// Returns the related ASTContext for the stored Stmts.
- ASTContext &getASTContext() const {
- assert(Context);
- return *Context;
+ ASTContext &getASTContext() const;
+
+ /// Returns the declaration that contains the stored Stmts.
+ const Decl *getContainingDecl() const {
+ assert(D);
+ return D;
}
/// Returns true if this objects holds a list of statements.
bool contains(const StmtSequence &Other) const;
};
-/// \brief Searches for clones in source code.
+/// Searches for similar subtrees in the AST.
///
-/// First, this class needs a translation unit which is passed via
-/// \p analyzeTranslationUnit . It will then generate and store search data
-/// for all statements inside the given translation unit.
-/// Afterwards the generated data can be used to find code clones by calling
-/// \p findClones .
+/// First, this class needs several declarations with statement bodies which
+/// can be passed via analyzeCodeBody. Afterwards all statements can be
+/// searched for clones by calling findClones with a given list of constraints
+/// that should specify the wanted properties of the clones.
+///
+/// The result of findClones can be further constrained with the constrainClones
+/// method.
///
/// This class only searches for clones in exectuable source code
/// (e.g. function bodies). Other clones (e.g. cloned comments or declarations)
/// are not supported.
class CloneDetector {
+
public:
- typedef unsigned DataPiece;
-
- /// Holds the data about a StmtSequence that is needed during the search for
- /// code clones.
- struct CloneSignature {
- /// \brief The hash code of the StmtSequence.
- ///
- /// The initial clone groups that are formed during the search for clones
- /// consist only of Sequences that share the same hash code. This makes this
- /// value the central part of this heuristic that is needed to find clones
- /// in a performant way. For this to work, the type of this variable
- /// always needs to be small and fast to compare.
- ///
- /// Also, StmtSequences that are clones of each others have to share
- /// the same hash code. StmtSequences that are not clones of each other
- /// shouldn't share the same hash code, but if they do, it will only
- /// degrade the performance of the hash search but doesn't influence
- /// the correctness of the result.
- size_t Hash;
-
- /// \brief The complexity of the StmtSequence.
- ///
- /// This value gives an approximation on how many direct or indirect child
- /// statements are contained in the related StmtSequence. In general, the
- /// greater this value, the greater the amount of statements. However, this
- /// is only an approximation and the actual amount of statements can be
- /// higher or lower than this value. Statements that are generated by the
- /// compiler (e.g. macro expansions) for example barely influence the
- /// complexity value.
- ///
- /// The main purpose of this value is to filter clones that are too small
- /// and therefore probably not interesting enough for the user.
- unsigned Complexity;
-
- /// \brief Creates an empty CloneSignature without any data.
- CloneSignature() : Complexity(1) {}
-
- CloneSignature(llvm::hash_code Hash, unsigned Complexity)
- : Hash(Hash), Complexity(Complexity) {}
- };
+ /// A collection of StmtSequences that share an arbitrary property.
+ typedef llvm::SmallVector<StmtSequence, 8> CloneGroup;
- /// Holds group of StmtSequences that are clones of each other and the
- /// complexity value (see CloneSignature::Complexity) that all stored
- /// StmtSequences have in common.
- struct CloneGroup {
- std::vector<StmtSequence> Sequences;
- CloneSignature Signature;
+ /// Generates and stores search data for all statements in the body of
+ /// the given Decl.
+ void analyzeCodeBody(const Decl *D);
- CloneGroup() {}
+ /// Constrains the given list of clone groups with the given constraint.
+ ///
+ /// The constraint is expected to have a method with the signature
+ /// `void constrain(std::vector<CloneDetector::CloneGroup> &Sequences)`
+ /// as this is the interface that the CloneDetector uses for applying the
+ /// constraint. The constraint is supposed to directly modify the passed list
+ /// so that all clones in the list fulfill the specific property this
+ /// constraint ensures.
+ template <typename T>
+ static void constrainClones(std::vector<CloneGroup> &CloneGroups, T C) {
+ C.constrain(CloneGroups);
+ }
- CloneGroup(const StmtSequence &Seq, CloneSignature Signature)
- : Signature(Signature) {
- Sequences.push_back(Seq);
- }
+ /// Constrains the given list of clone groups with the given list of
+ /// constraints.
+ ///
+ /// The constraints are applied in sequence in the order in which they are
+ /// passed to this function.
+ template <typename T1, typename... Ts>
+ static void constrainClones(std::vector<CloneGroup> &CloneGroups, T1 C,
+ Ts... ConstraintList) {
+ constrainClones(CloneGroups, C);
+ constrainClones(CloneGroups, ConstraintList...);
+ }
- /// \brief Returns false if and only if this group should be skipped when
- /// searching for clones.
- bool isValid() const {
- // A clone group with only one member makes no sense, so we skip them.
- return Sequences.size() > 1;
+ /// Searches for clones in all previously passed statements.
+ /// \param Result Output parameter to which all created clone groups are
+ /// added.
+ /// \param Passes The constraints that should be applied to the result.
+ template <typename... Ts>
+ void findClones(std::vector<CloneGroup> &Result, Ts... ConstraintList) {
+ // The initial assumption is that there is only one clone group and every
+ // statement is a clone of the others. This clone group will then be
+ // split up with the help of the constraints.
+ CloneGroup AllClones;
+ AllClones.reserve(Sequences.size());
+ for (const auto &C : Sequences) {
+ AllClones.push_back(C);
}
- };
- /// \brief Generates and stores search data for all statements in the body of
- /// the given Decl.
- void analyzeCodeBody(const Decl *D);
+ Result.push_back(AllClones);
- /// \brief Stores the CloneSignature to allow future querying.
- void add(const StmtSequence &S, const CloneSignature &Signature);
+ constrainClones(Result, ConstraintList...);
+ }
- /// \brief Searches the provided statements for clones.
+private:
+ CloneGroup Sequences;
+};
+
+/// This class is a utility class that contains utility functions for building
+/// custom constraints.
+class CloneConstraint {
+public:
+ /// Removes all groups by using a filter function.
+ /// \param CloneGroups The list of CloneGroups that is supposed to be
+ /// filtered.
+ /// \param Filter The filter function that should return true for all groups
+ /// that should be removed from the list.
+ static void
+ filterGroups(std::vector<CloneDetector::CloneGroup> &CloneGroups,
+ std::function<bool(const CloneDetector::CloneGroup &)> Filter) {
+ CloneGroups.erase(
+ std::remove_if(CloneGroups.begin(), CloneGroups.end(), Filter),
+ CloneGroups.end());
+ }
+
+ /// Splits the given CloneGroups until the given Compare function returns true
+ /// for all clones in a single group.
+ /// \param CloneGroups A list of CloneGroups that should be modified.
+ /// \param Compare The comparison function that all clones are supposed to
+ /// pass. Should return true if and only if two clones belong
+ /// to the same CloneGroup.
+ static void splitCloneGroups(
+ std::vector<CloneDetector::CloneGroup> &CloneGroups,
+ std::function<bool(const StmtSequence &, const StmtSequence &)> Compare);
+};
+
+/// Searches all children of the given clones for type II clones (i.e. they are
+/// identical in every aspect beside the used variable names).
+class RecursiveCloneTypeIIConstraint {
+
+ /// 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.
///
- /// \param Result Output parameter that is filled with a list of found
- /// clone groups. Each group contains multiple StmtSequences
- /// that were identified to be clones of each other.
- /// \param MinGroupComplexity Only return clones which have at least this
- /// complexity value.
- /// \param CheckPatterns Returns only clone groups in which the referenced
- /// variables follow the same pattern.
- void findClones(std::vector<CloneGroup> &Result, unsigned MinGroupComplexity,
- bool CheckPatterns = true);
-
- /// \brief Describes two clones that reference their variables in a different
- /// pattern which could indicate a programming error.
+ /// If the given Stmt is a CompoundStmt, this method will also generate
+ /// hashes for all possible StmtSequences in the children of this Stmt.
+ size_t saveHash(const Stmt *S, const Decl *D,
+ std::vector<std::pair<size_t, StmtSequence>> &StmtsByHash);
+
+public:
+ void constrain(std::vector<CloneDetector::CloneGroup> &Sequences);
+};
+
+/// Ensures that every clone has at least the given complexity.
+///
+/// Complexity is here defined as the total amount of children of a statement.
+/// This constraint assumes the first statement in the group is representative
+/// for all other statements in the group in terms of complexity.
+class MinComplexityConstraint {
+ unsigned MinComplexity;
+
+public:
+ MinComplexityConstraint(unsigned MinComplexity)
+ : MinComplexity(MinComplexity) {}
+
+ size_t calculateStmtComplexity(const StmtSequence &Seq,
+ const std::string &ParentMacroStack = "");
+
+ void constrain(std::vector<CloneDetector::CloneGroup> &CloneGroups) {
+ CloneConstraint::filterGroups(
+ CloneGroups, [this](const CloneDetector::CloneGroup &A) {
+ if (!A.empty())
+ return calculateStmtComplexity(A.front()) < MinComplexity;
+ else
+ return false;
+ });
+ }
+};
+
+/// Ensures that all clone groups contain at least the given amount of clones.
+class MinGroupSizeConstraint {
+ unsigned MinGroupSize;
+
+public:
+ MinGroupSizeConstraint(unsigned MinGroupSize = 2)
+ : MinGroupSize(MinGroupSize) {}
+
+ void constrain(std::vector<CloneDetector::CloneGroup> &CloneGroups) {
+ CloneConstraint::filterGroups(CloneGroups,
+ [this](const CloneDetector::CloneGroup &A) {
+ return A.size() < MinGroupSize;
+ });
+ }
+};
+
+/// Ensures that no clone group fully contains another clone group.
+struct OnlyLargestCloneConstraint {
+ void constrain(std::vector<CloneDetector::CloneGroup> &Result);
+};
+
+/// Analyzes the pattern of the referenced variables in a statement.
+class VariablePattern {
+
+ /// Describes an occurence of a variable reference in a statement.
+ struct VariableOccurence {
+ /// The index of the associated VarDecl in the Variables vector.
+ size_t KindID;
+ /// The statement in the code where the variable was referenced.
+ const Stmt *Mention;
+
+ VariableOccurence(size_t KindID, const Stmt *Mention)
+ : KindID(KindID), Mention(Mention) {}
+ };
+
+ /// All occurences of referenced variables in the order of appearance.
+ std::vector<VariableOccurence> Occurences;
+ /// List of referenced variables in the order of appearance.
+ /// Every item in this list is unique.
+ std::vector<const VarDecl *> Variables;
+
+ /// Adds a new variable referenced to this pattern.
+ /// \param VarDecl The declaration of the variable that is referenced.
+ /// \param Mention The SourceRange where this variable is referenced.
+ void addVariableOccurence(const VarDecl *VarDecl, const Stmt *Mention);
+
+ /// Adds each referenced variable from the given statement.
+ void addVariables(const Stmt *S);
+
+public:
+ /// Creates an VariablePattern object with information about the given
+ /// StmtSequence.
+ VariablePattern(const StmtSequence &Sequence) {
+ for (const Stmt *S : Sequence)
+ addVariables(S);
+ }
+
+ /// Describes two clones that reference their variables in a different pattern
+ /// which could indicate a programming error.
struct SuspiciousClonePair {
- /// \brief Utility class holding the relevant information about a single
- /// clone in this pair.
+ /// Utility class holding the relevant information about a single
+ /// clone in this pair.
struct SuspiciousCloneInfo {
/// The variable which referencing in this clone was against the pattern.
const VarDecl *Variable;
SuspiciousCloneInfo SecondCloneInfo;
};
- /// \brief Searches the provided statements for pairs of clones that don't
- /// follow the same pattern when referencing variables.
- /// \param Result Output parameter that will contain the clone pairs.
- /// \param MinGroupComplexity Only clone pairs in which the clones have at
- /// least this complexity value.
- void findSuspiciousClones(std::vector<SuspiciousClonePair> &Result,
- unsigned MinGroupComplexity);
+ /// Counts the differences between this pattern and the given one.
+ /// \param Other The given VariablePattern to compare with.
+ /// \param FirstMismatch Output parameter that will be filled with information
+ /// about the first difference between the two patterns. This parameter
+ /// can be a nullptr, in which case it will be ignored.
+ /// \return Returns the number of differences between the pattern this object
+ /// is following and the given VariablePattern.
+ ///
+ /// For example, the following statements all have the same pattern and this
+ /// function would return zero:
+ ///
+ /// if (a < b) return a; return b;
+ /// if (x < y) return x; return y;
+ /// if (u2 < u1) return u2; return u1;
+ ///
+ /// But the following statement has a different pattern (note the changed
+ /// variables in the return statements) and would have two differences when
+ /// compared with one of the statements above.
+ ///
+ /// if (a < b) return b; return a;
+ ///
+ /// This function should only be called if the related statements of the given
+ /// pattern and the statements of this objects are clones of each other.
+ unsigned countPatternDifferences(
+ const VariablePattern &Other,
+ VariablePattern::SuspiciousClonePair *FirstMismatch = nullptr);
+};
-private:
- /// Stores all encountered StmtSequences alongside their CloneSignature.
- std::vector<std::pair<CloneSignature, StmtSequence>> Sequences;
+/// Ensures that all clones reference variables in the same pattern.
+struct MatchingVariablePatternConstraint {
+ void constrain(std::vector<CloneDetector::CloneGroup> &CloneGroups);
};
} // end namespace clang
using namespace clang;
-StmtSequence::StmtSequence(const CompoundStmt *Stmt, ASTContext &Context,
+StmtSequence::StmtSequence(const CompoundStmt *Stmt, const Decl *D,
unsigned StartIndex, unsigned EndIndex)
- : S(Stmt), Context(&Context), StartIndex(StartIndex), EndIndex(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, ASTContext &Context)
- : S(Stmt), Context(&Context), StartIndex(0), EndIndex(0) {}
+StmtSequence::StmtSequence(const Stmt *Stmt, const Decl *D)
+ : S(Stmt), D(D), StartIndex(0), EndIndex(0) {}
StmtSequence::StmtSequence()
- : S(nullptr), Context(nullptr), StartIndex(0), EndIndex(0) {}
+ : S(nullptr), D(nullptr), StartIndex(0), EndIndex(0) {}
bool StmtSequence::contains(const StmtSequence &Other) const {
- // If both sequences reside in different translation units, they can never
- // contain each other.
- if (Context != Other.Context)
+ // If both sequences reside in different declarations, they can never contain
+ // each other.
+ if (D != Other.D)
return false;
- const SourceManager &SM = Context->getSourceManager();
+ const SourceManager &SM = getASTContext().getSourceManager();
// Otherwise check if the start and end locations of the current sequence
// surround the other sequence.
return CS->body_begin() + EndIndex;
}
+ASTContext &StmtSequence::getASTContext() const {
+ assert(D);
+ return D->getASTContext();
+}
+
SourceLocation StmtSequence::getStartLoc() const {
return front()->getLocStart();
}
return SourceRange(getStartLoc(), getEndLoc());
}
-namespace {
-
-/// \brief Analyzes the pattern of the referenced variables in a statement.
-class VariablePattern {
-
- /// \brief Describes an occurence of a variable reference in a statement.
- struct VariableOccurence {
- /// The index of the associated VarDecl in the Variables vector.
- size_t KindID;
- /// The statement in the code where the variable was referenced.
- const Stmt *Mention;
-
- VariableOccurence(size_t KindID, const Stmt *Mention)
- : KindID(KindID), Mention(Mention) {}
- };
-
- /// All occurences of referenced variables in the order of appearance.
- std::vector<VariableOccurence> Occurences;
- /// List of referenced variables in the order of appearance.
- /// Every item in this list is unique.
- std::vector<const VarDecl *> Variables;
-
- /// \brief Adds a new variable referenced to this pattern.
- /// \param VarDecl The declaration of the variable that is referenced.
- /// \param Mention The SourceRange where this variable is referenced.
- void 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 occurence 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 occurence that points to this new entry.
- Occurences.emplace_back(Variables.size(), Mention);
- Variables.push_back(VarDecl);
- }
-
- /// \brief Adds each referenced variable from the given statement.
- void 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);
- }
- }
-
-public:
- /// \brief Creates an VariablePattern object with information about the given
- /// StmtSequence.
- VariablePattern(const StmtSequence &Sequence) {
- for (const Stmt *S : Sequence)
- addVariables(S);
- }
-
- /// \brief Counts the differences between this pattern and the given one.
- /// \param Other The given VariablePattern to compare with.
- /// \param FirstMismatch Output parameter that will be filled with information
- /// about the first difference between the two patterns. This parameter
- /// can be a nullptr, in which case it will be ignored.
- /// \return Returns the number of differences between the pattern this object
- /// is following and the given VariablePattern.
- ///
- /// For example, the following statements all have the same pattern and this
- /// function would return zero:
- ///
- /// if (a < b) return a; return b;
- /// if (x < y) return x; return y;
- /// if (u2 < u1) return u2; return u1;
- ///
- /// But the following statement has a different pattern (note the changed
- /// variables in the return statements) and would have two differences when
- /// compared with one of the statements above.
- ///
- /// if (a < b) return b; return a;
- ///
- /// This function should only be called if the related statements of the given
- /// pattern and the statements of this objects are clones of each other.
- unsigned countPatternDifferences(
- const VariablePattern &Other,
- CloneDetector::SuspiciousClonePair *FirstMismatch = nullptr) {
- 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 =
- CloneDetector::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 =
- CloneDetector::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;
- }
-};
-}
-
-/// \brief Prints the macro name that contains the given SourceLocation into
-/// the given raw_string_ostream.
+/// Prints the macro name that contains the given SourceLocation into the given
+/// raw_string_ostream.
static void printMacroName(llvm::raw_string_ostream &MacroStack,
ASTContext &Context, SourceLocation Loc) {
MacroStack << Lexer::getImmediateMacroName(Loc, Context.getSourceManager(),
MacroStack << " ";
}
-/// \brief Returns a string that represents all macro expansions that
-/// expanded into the given SourceLocation.
+/// Returns a string that represents all macro expansions that expanded into the
+/// given SourceLocation.
///
/// If 'getMacroStack(A) == getMacroStack(B)' is true, then the SourceLocations
/// A and B are expanded from the same macros in the same order.
}
namespace {
-/// \brief Collects the data of a single Stmt.
+typedef unsigned DataPiece;
+
+/// Collects the data of a single Stmt.
///
/// This class defines what a code clone is: If it collects for two statements
/// the same data, then those two statements are considered to be clones of each
class StmtDataCollector : public ConstStmtVisitor<StmtDataCollector<T>> {
ASTContext &Context;
- /// \brief The data sink to which all data is forwarded.
+ /// The data sink to which all data is forwarded.
T &DataConsumer;
public:
- /// \brief Collects data of the given Stmt.
+ /// Collects data of the given Stmt.
/// \param S The given statement.
/// \param Context The ASTContext of S.
/// \param DataConsumer The data sink to which all data is forwarded.
// Below are utility methods for appending different data to the vector.
- void addData(CloneDetector::DataPiece Integer) {
+ void addData(DataPiece Integer) {
DataConsumer.update(
StringRef(reinterpret_cast<char *>(&Integer), sizeof(Integer)));
}
})
DEF_ADD_DATA(DeclStmt, {
auto numDecls = std::distance(S->decl_begin(), S->decl_end());
- addData(static_cast<CloneDetector::DataPiece>(numDecls));
+ addData(static_cast<DataPiece>(numDecls));
for (const Decl *D : S->decls()) {
if (const VarDecl *VD = dyn_cast<VarDecl>(D)) {
addData(VD->getType());
};
} // end anonymous namespace
-namespace {
-/// Generates CloneSignatures for a set of statements and stores the results in
-/// a CloneDetector object.
-class CloneSignatureGenerator {
+void CloneDetector::analyzeCodeBody(const Decl *D) {
+ assert(D);
+ assert(D->hasBody());
- CloneDetector &CD;
- ASTContext &Context;
+ Sequences.push_back(StmtSequence(D->getBody(), D));
+}
- /// \brief Generates CloneSignatures for all statements in the given statement
- /// tree and stores them in the CloneDetector.
- ///
- /// \param S The root of the given statement tree.
- /// \param ParentMacroStack A string representing the macros that generated
- /// the parent statement or an empty string if no
- /// macros generated the parent statement.
- /// See getMacroStack() for generating such a string.
- /// \return The CloneSignature of the root statement.
- CloneDetector::CloneSignature
- generateSignatures(const Stmt *S, const std::string &ParentMacroStack) {
- // Create an empty signature that will be filled in this method.
- CloneDetector::CloneSignature Signature;
-
- llvm::MD5 Hash;
-
- // Collect all relevant data from S and hash it.
- StmtDataCollector<llvm::MD5>(S, Context, Hash);
-
- // Look up what macros expanded into the current statement.
- std::string StartMacroStack = getMacroStack(S->getLocStart(), Context);
- std::string EndMacroStack = getMacroStack(S->getLocEnd(), 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() && (StartMacroStack == ParentMacroStack &&
- EndMacroStack == ParentMacroStack)) {
- Signature.Complexity = 0;
- }
+/// 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;
+}
- // Storage for the signatures of the direct child statements. This is only
- // needed if the current statement is a CompoundStmt.
- std::vector<CloneDetector::CloneSignature> ChildSignatures;
- const CompoundStmt *CS = dyn_cast<const CompoundStmt>(S);
+/// 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;
- // The signature of a statement includes the signatures of its children.
- // Therefore we create the signatures for every child and add them to the
- // current signature.
- for (const Stmt *Child : S->children()) {
- // Some statements like 'if' can have nullptr children that we will skip.
- if (!Child)
- continue;
+ for (StmtSequence &Stmt : Group) {
+ if (!containsAnyInGroup(Stmt, OtherGroup))
+ return false;
+ }
+ return true;
+}
- // Recursive call to create the signature of the child statement. This
- // will also create and store all clone groups in this child statement.
- // We pass only the StartMacroStack along to keep things simple.
- auto ChildSignature = generateSignatures(Child, StartMacroStack);
+void OnlyLargestCloneConstraint::constrain(
+ std::vector<CloneDetector::CloneGroup> &Result) {
+ std::vector<unsigned> IndexesToRemove;
- // Add the collected data to the signature of the current statement.
- Signature.Complexity += ChildSignature.Complexity;
- Hash.update(StringRef(reinterpret_cast<char *>(&ChildSignature.Hash),
- sizeof(ChildSignature.Hash)));
+ // 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 the current statement is a CompoundStatement, we need to store the
- // signature for the generation of the sub-sequences.
- if (CS)
- ChildSignatures.push_back(ChildSignature);
+ if (containsGroup(Result[j], Result[i])) {
+ IndexesToRemove.push_back(i);
+ break;
+ }
}
+ }
- // If the current statement is a CompoundStmt, we also need to create the
- // clone groups from the sub-sequences inside the children.
- if (CS)
- handleSubSequences(CS, ChildSignatures);
+ // 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);
+ }
+}
- // Create the final hash code for the current signature.
- llvm::MD5::MD5Result HashResult;
- Hash.final(HashResult);
+static size_t createHash(llvm::MD5 &Hash) {
+ size_t HashCode;
- // Copy as much of the generated hash code to the signature's hash code.
- std::memcpy(&Signature.Hash, &HashResult,
- std::min(sizeof(Signature.Hash), sizeof(HashResult)));
+ // Create the final hash code for the current Stmt.
+ llvm::MD5::MD5Result HashResult;
+ Hash.final(HashResult);
- // Save the signature for the current statement in the CloneDetector object.
- CD.add(StmtSequence(S, Context), Signature);
+ // 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 Signature;
- }
+ return HashCode;
+}
- /// \brief Adds all possible sub-sequences in the child array of the given
- /// CompoundStmt to the CloneDetector.
- /// \param CS The given CompoundStmt.
- /// \param ChildSignatures A list of calculated signatures for each child in
- /// the given CompoundStmt.
- void handleSubSequences(
- const CompoundStmt *CS,
- const std::vector<CloneDetector::CloneSignature> &ChildSignatures) {
+size_t RecursiveCloneTypeIIConstraint::saveHash(
+ const Stmt *S, const Decl *D,
+ std::vector<std::pair<size_t, StmtSequence>> &StmtsByHash) {
+ llvm::MD5 Hash;
+ ASTContext &Context = D->getASTContext();
- // FIXME: This function has quadratic runtime right now. Check if skipping
- // this function for too long CompoundStmts is an option.
+ StmtDataCollector<llvm::MD5>(S, Context, Hash);
- // The length of the sub-sequence. We don't need to handle sequences with
- // the length 1 as they are already handled in CollectData().
+ 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) {
for (unsigned Length = 2; Length <= CS->size(); ++Length) {
- // The start index in the body of the CompoundStmt. We increase the
- // position until the end of the sub-sequence reaches the end of the
- // CompoundStmt body.
for (unsigned Pos = 0; Pos <= CS->size() - Length; ++Pos) {
- // Create an empty signature and add the signatures of all selected
- // child statements to it.
- CloneDetector::CloneSignature SubSignature;
- llvm::MD5 SubHash;
-
+ llvm::MD5 Hash;
for (unsigned i = Pos; i < Pos + Length; ++i) {
- SubSignature.Complexity += ChildSignatures[i].Complexity;
- size_t ChildHash = ChildSignatures[i].Hash;
-
- SubHash.update(StringRef(reinterpret_cast<char *>(&ChildHash),
+ size_t ChildHash = ChildHashes[i];
+ Hash.update(StringRef(reinterpret_cast<char *>(&ChildHash),
sizeof(ChildHash)));
}
-
- // Create the final hash code for the current signature.
- llvm::MD5::MD5Result HashResult;
- SubHash.final(HashResult);
-
- // Copy as much of the generated hash code to the signature's hash code.
- std::memcpy(&SubSignature.Hash, &HashResult,
- std::min(sizeof(SubSignature.Hash), sizeof(HashResult)));
-
- // Save the signature together with the information about what children
- // sequence we selected.
- CD.add(StmtSequence(CS, Context, Pos, Pos + Length), SubSignature);
+ StmtsByHash.push_back(std::make_pair(
+ createHash(Hash), StmtSequence(CS, D, Pos, Pos + Length)));
}
}
}
-public:
- explicit CloneSignatureGenerator(CloneDetector &CD, ASTContext &Context)
- : CD(CD), Context(Context) {}
-
- /// \brief Generates signatures for all statements in the given function body.
- void consumeCodeBody(const Stmt *S) { generateSignatures(S, ""); }
-};
-} // end anonymous namespace
-
-void CloneDetector::analyzeCodeBody(const Decl *D) {
- assert(D);
- assert(D->hasBody());
- CloneSignatureGenerator Generator(*this, D->getASTContext());
- Generator.consumeCodeBody(D->getBody());
-}
-
-void CloneDetector::add(const StmtSequence &S,
- const CloneSignature &Signature) {
- Sequences.push_back(std::make_pair(Signature, S));
+ size_t HashCode = createHash(Hash);
+ StmtsByHash.push_back(std::make_pair(HashCode, StmtSequence(S, D)));
+ return HashCode;
}
namespace {
-/// \brief Returns true if and only if \p Stmt contains at least one other
-/// sequence in the \p Group.
-bool containsAnyInGroup(StmtSequence &Stmt, CloneDetector::CloneGroup &Group) {
- for (StmtSequence &GroupStmt : Group.Sequences) {
- if (Stmt.contains(GroupStmt))
- return true;
- }
- return false;
-}
-
-/// \brief Returns true if and only if all sequences in \p OtherGroup are
-/// contained by a sequence in \p Group.
-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.Sequences.size() < OtherGroup.Sequences.size())
- return false;
-
- for (StmtSequence &Stmt : Group.Sequences) {
- if (!containsAnyInGroup(Stmt, OtherGroup))
- return false;
- }
- return true;
-}
-} // end anonymous namespace
-
-namespace {
-/// \brief Wrapper around FoldingSetNodeID that it can be used as the template
-/// argument of the StmtDataCollector.
+/// Wrapper around FoldingSetNodeID that it can be used as the template
+/// argument of the StmtDataCollector.
class FoldingSetNodeIDWrapper {
llvm::FoldingSetNodeID &FS;
};
} // end anonymous namespace
-/// \brief Writes the relevant data from all statements and child statements
-/// in the given StmtSequence into the given FoldingSetNodeID.
+/// 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) {
if (!Child)
continue;
- CollectStmtSequenceData(StmtSequence(Child, Sequence.getASTContext()),
+ CollectStmtSequenceData(StmtSequence(Child, Sequence.getContainingDecl()),
OutputData);
}
}
}
-/// \brief Returns true if both sequences are clones of each other.
+/// 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
return DataLHS == DataRHS;
}
-/// \brief Finds all actual clone groups in a single group of presumed clones.
-/// \param Result Output parameter to which all found groups are added.
-/// \param Group A group of presumed clones. The clones are allowed to have a
-/// different variable pattern and may not be actual clones of each
-/// other.
-/// \param CheckVariablePattern If true, every clone in a group that was added
-/// to the output follows the same variable pattern as the other
-/// clones in its group.
-static void createCloneGroups(std::vector<CloneDetector::CloneGroup> &Result,
- const CloneDetector::CloneGroup &Group,
- bool CheckVariablePattern) {
- // We remove the Sequences one by one, so a list is more appropriate.
- std::list<StmtSequence> UnassignedSequences(Group.Sequences.begin(),
- Group.Sequences.end());
-
- // Search for clones as long as there could be clones in UnassignedSequences.
- while (UnassignedSequences.size() > 1) {
-
- // Pick the first Sequence as a protoype for a new clone group.
- StmtSequence Prototype = UnassignedSequences.front();
- UnassignedSequences.pop_front();
-
- CloneDetector::CloneGroup FilteredGroup(Prototype, Group.Signature);
-
- // Analyze the variable pattern of the prototype. Every other StmtSequence
- // needs to have the same pattern to get into the new clone group.
- VariablePattern PrototypeFeatures(Prototype);
-
- // Search all remaining StmtSequences for an identical variable pattern
- // and assign them to our new clone group.
- auto I = UnassignedSequences.begin(), E = UnassignedSequences.end();
- while (I != E) {
- // If the sequence doesn't fit to the prototype, we have encountered
- // an unintended hash code collision and we skip it.
- if (!areSequencesClones(Prototype, *I)) {
- ++I;
- continue;
- }
+void RecursiveCloneTypeIIConstraint::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;
- // If we weren't asked to check for a matching variable pattern in clone
- // groups we can add the sequence now to the new clone group.
- // If we were asked to check for matching variable pattern, we first have
- // to check that there are no differences between the two patterns and
- // only proceed if they match.
- if (!CheckVariablePattern ||
- VariablePattern(*I).countPatternDifferences(PrototypeFeatures) == 0) {
- FilteredGroup.Sequences.push_back(*I);
- I = UnassignedSequences.erase(I);
- continue;
- }
+ 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;
- // We didn't found a matching variable pattern, so we continue with the
- // next sequence.
- ++I;
+ // Generate hash codes for all children of S and save them in StmtsByHash.
+ for (const StmtSequence &S : Group) {
+ saveHash(S.front(), S.getContainingDecl(), StmtsByHash);
}
- // Add a valid clone group to the list of found clone groups.
- if (!FilteredGroup.isValid())
- continue;
+ // Sort hash_codes in StmtsByHash.
+ std::stable_sort(StmtsByHash.begin(), StmtsByHash.end(),
+ [this](std::pair<size_t, StmtSequence> LHS,
+ std::pair<size_t, StmtSequence> RHS) {
+ return LHS.first < RHS.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 an 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 ||
+ !areSequencesClones(StmtsByHash[i].second, Current.second)) {
+ // 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);
+ }
- Result.push_back(FilteredGroup);
+ // 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 CloneDetector::findClones(std::vector<CloneGroup> &Result,
- unsigned MinGroupComplexity,
- bool CheckPatterns) {
- // A shortcut (and necessary for the for-loop later in this function).
- if (Sequences.empty())
- return;
+size_t MinComplexityConstraint::calculateStmtComplexity(
+ const StmtSequence &Seq, 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 StartMacroStack = getMacroStack(Seq.getStartLoc(), Context);
+ std::string EndMacroStack = getMacroStack(Seq.getEndLoc(), 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() && (StartMacroStack == ParentMacroStack &&
+ EndMacroStack == ParentMacroStack)) {
+ Complexity = 0;
+ }
- // We need to search for groups of StmtSequences with the same hash code to
- // create our initial clone groups. By sorting all known StmtSequences by
- // their hash value we make sure that StmtSequences with the same hash code
- // are grouped together in the Sequences vector.
- // Note: We stable sort here because the StmtSequences are added in the order
- // in which they appear in the source file. We want to preserve that order
- // because we also want to report them in that order in the CloneChecker.
- std::stable_sort(Sequences.begin(), Sequences.end(),
- [](std::pair<CloneSignature, StmtSequence> LHS,
- std::pair<CloneSignature, StmtSequence> RHS) {
- return LHS.first.Hash < RHS.first.Hash;
- });
-
- std::vector<CloneGroup> CloneGroups;
-
- // Check for each CloneSignature if its successor has the same hash value.
- // We don't check the last CloneSignature as it has no successor.
- // Note: The 'size - 1' in the condition is safe because we check for an empty
- // Sequences vector at the beginning of this function.
- for (unsigned i = 0; i < Sequences.size() - 1; ++i) {
- const auto Current = Sequences[i];
- const auto Next = Sequences[i + 1];
-
- if (Current.first.Hash != Next.first.Hash)
- continue;
+ // 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()), StartMacroStack);
+ }
+ } else {
+ for (const Stmt *S : Seq.front()->children()) {
+ Complexity += calculateStmtComplexity(
+ StmtSequence(S, Seq.getContainingDecl()), StartMacroStack);
+ }
+ }
+ return Complexity;
+}
- // It's likely that we just found an sequence of CloneSignatures that
- // represent a CloneGroup, so we create a new group and start checking and
- // adding the CloneSignatures in this sequence.
- CloneGroup Group;
- Group.Signature = Current.first;
-
- for (; i < Sequences.size(); ++i) {
- const auto &Signature = Sequences[i];
-
- // A different hash value means we have reached the end of the sequence.
- if (Current.first.Hash != Signature.first.Hash) {
- // The current Signature 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 CloneSignature with itself in the 'if' above.
- assert(i != 0);
- --i;
- break;
- }
+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;
+ });
+}
- // Skip CloneSignatures that won't pass the complexity requirement.
- if (Signature.first.Complexity < MinGroupComplexity)
+void CloneConstraint::splitCloneGroups(
+ std::vector<CloneDetector::CloneGroup> &CloneGroups,
+ std::function<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;
- Group.Sequences.push_back(Signature.second);
- }
+ // 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 to
+ // 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];
+ }
- // There is a chance that we haven't found more than two fitting
- // CloneSignature because not enough CloneSignatures passed the complexity
- // requirement. As a CloneGroup with less than two members makes no sense,
- // we ignore this CloneGroup and won't add it to the result.
- if (!Group.isValid())
- continue;
+ // Otherwise, add it to the result and continue searching for more
+ // groups.
+ Result.push_back(PotentialGroup);
+ }
- CloneGroups.push_back(Group);
+ assert(std::all_of(Indexes.begin(), Indexes.end(),
+ [](char c) { return c == 1; }));
}
+ CloneGroups = Result;
+}
- // Add every valid clone group that fulfills the complexity requirement.
- for (const CloneGroup &Group : CloneGroups) {
- createCloneGroups(Result, Group, CheckPatterns);
+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 occurence 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 occurence that points to this new entry.
+ Occurences.emplace_back(Variables.size(), Mention);
+ Variables.push_back(VarDecl);
+}
- 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;
+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;
- if (containsGroup(Result[j], Result[i])) {
- IndexesToRemove.push_back(i);
- break;
- }
- }
+ // 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);
}
- // 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);
+ // Recursively check all children of the given statement.
+ for (const Stmt *Child : S->children()) {
+ addVariables(Child);
}
}
-void CloneDetector::findSuspiciousClones(
- std::vector<CloneDetector::SuspiciousClonePair> &Result,
- unsigned MinGroupComplexity) {
- std::vector<CloneGroup> Clones;
- // Reuse the normal search for clones but specify that the clone groups don't
- // need to have a common referenced variable pattern so that we can manually
- // search for the kind of pattern errors this function is supposed to find.
- findClones(Clones, MinGroupComplexity, false);
-
- for (const CloneGroup &Group : Clones) {
- for (unsigned i = 0; i < Group.Sequences.size(); ++i) {
- VariablePattern PatternA(Group.Sequences[i]);
-
- for (unsigned j = i + 1; j < Group.Sequences.size(); ++j) {
- VariablePattern PatternB(Group.Sequences[j]);
-
- CloneDetector::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).
- // TODO: 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) {
- Result.push_back(ClonePair);
- break;
- }
- }
- }
+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;
}
projects / clang / commitdiff