Revert "[analyzer] Add a modular constraint system to the CloneDetector"
This reverts commit r299544.
Crashes on tests on some buildbots.
llvm-svn: 299550
diff --git a/clang/lib/Analysis/CloneDetection.cpp b/clang/lib/Analysis/CloneDetection.cpp
index 11f3961..e761738 100644
--- a/clang/lib/Analysis/CloneDetection.cpp
+++ b/clang/lib/Analysis/CloneDetection.cpp
@@ -24,27 +24,27 @@
using namespace clang;
-StmtSequence::StmtSequence(const CompoundStmt *Stmt, const Decl *D,
+StmtSequence::StmtSequence(const CompoundStmt *Stmt, ASTContext &Context,
unsigned StartIndex, unsigned EndIndex)
- : S(Stmt), D(D), StartIndex(StartIndex), EndIndex(EndIndex) {
+ : S(Stmt), Context(&Context), 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(const Stmt *Stmt, ASTContext &Context)
+ : S(Stmt), Context(&Context), StartIndex(0), EndIndex(0) {}
StmtSequence::StmtSequence()
- : S(nullptr), D(nullptr), StartIndex(0), EndIndex(0) {}
+ : S(nullptr), Context(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)
+ // If both sequences reside in different translation units, they can never
+ // contain each other.
+ if (Context != Other.Context)
return false;
- const SourceManager &SM = getASTContext().getSourceManager();
+ const SourceManager &SM = Context->getSourceManager();
// Otherwise check if the start and end locations of the current sequence
// surround the other sequence.
@@ -76,11 +76,6 @@
return CS->body_begin() + EndIndex;
}
-ASTContext &StmtSequence::getASTContext() const {
- assert(D);
- return D->getASTContext();
-}
-
SourceLocation StmtSequence::getStartLoc() const {
return front()->getLocStart();
}
@@ -91,8 +86,168 @@
return SourceRange(getStartLoc(), getEndLoc());
}
-/// Prints the macro name that contains the given SourceLocation into the given
-/// raw_string_ostream.
+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.
static void printMacroName(llvm::raw_string_ostream &MacroStack,
ASTContext &Context, SourceLocation Loc) {
MacroStack << Lexer::getImmediateMacroName(Loc, Context.getSourceManager(),
@@ -103,8 +258,8 @@
MacroStack << " ";
}
-/// Returns a string that represents all macro expansions that expanded into the
-/// given SourceLocation.
+/// \brief 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.
@@ -124,9 +279,7 @@
}
namespace {
-typedef unsigned DataPiece;
-
-/// Collects the data of a single Stmt.
+/// \brief 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
@@ -139,11 +292,11 @@
class StmtDataCollector : public ConstStmtVisitor<StmtDataCollector<T>> {
ASTContext &Context;
- /// The data sink to which all data is forwarded.
+ /// \brief The data sink to which all data is forwarded.
T &DataConsumer;
public:
- /// Collects data of the given Stmt.
+ /// \brief 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.
@@ -154,7 +307,7 @@
// Below are utility methods for appending different data to the vector.
- void addData(DataPiece Integer) {
+ void addData(CloneDetector::DataPiece Integer) {
DataConsumer.update(
StringRef(reinterpret_cast<char *>(&Integer), sizeof(Integer)));
}
@@ -272,7 +425,7 @@
})
DEF_ADD_DATA(DeclStmt, {
auto numDecls = std::distance(S->decl_begin(), S->decl_end());
- addData(static_cast<DataPiece>(numDecls));
+ addData(static_cast<CloneDetector::DataPiece>(numDecls));
for (const Decl *D : S->decls()) {
if (const VarDecl *VD = dyn_cast<VarDecl>(D)) {
addData(VD->getType());
@@ -301,44 +454,384 @@
};
} // end anonymous namespace
+namespace {
+/// Generates CloneSignatures for a set of statements and stores the results in
+/// a CloneDetector object.
+class CloneSignatureGenerator {
+
+ CloneDetector &CD;
+ ASTContext &Context;
+
+ /// \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;
+ }
+
+ // 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);
+
+ // 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;
+
+ // 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);
+
+ // 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)));
+
+ // 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 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);
+
+ // Create the final hash code for the current signature.
+ llvm::MD5::MD5Result HashResult;
+ Hash.final(HashResult);
+
+ // 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)));
+
+ // Save the signature for the current statement in the CloneDetector object.
+ CD.add(StmtSequence(S, Context), Signature);
+
+ return Signature;
+ }
+
+ /// \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) {
+
+ // FIXME: This function has quadratic runtime right now. Check if skipping
+ // this function for too long CompoundStmts is an option.
+
+ // The length of the sub-sequence. We don't need to handle sequences with
+ // the length 1 as they are already handled in CollectData().
+ 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;
+
+ 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),
+ 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);
+ }
+ }
+ }
+
+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());
-
- Sequences.push_back(StmtSequence(D->getBody(), D));
+ CloneSignatureGenerator Generator(*this, D->getASTContext());
+ Generator.consumeCodeBody(D->getBody());
}
-/// Returns true if and only if \p Stmt contains at least one other
+void CloneDetector::add(const StmtSequence &S,
+ const CloneSignature &Signature) {
+ Sequences.push_back(std::make_pair(Signature, S));
+}
+
+namespace {
+/// \brief 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))
+bool containsAnyInGroup(StmtSequence &Stmt, CloneDetector::CloneGroup &Group) {
+ for (StmtSequence &GroupStmt : Group.Sequences) {
+ if (Stmt.contains(GroupStmt))
return true;
}
return false;
}
-/// Returns true if and only if all sequences in \p OtherGroup are
+/// \brief 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) {
+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())
+ if (Group.Sequences.size() < OtherGroup.Sequences.size())
return false;
- for (StmtSequence &Stmt : Group) {
+ for (StmtSequence &Stmt : Group.Sequences) {
if (!containsAnyInGroup(Stmt, OtherGroup))
return false;
}
return true;
}
+} // end anonymous namespace
-void OnlyLargestCloneConstraint::constrain(
- std::vector<CloneDetector::CloneGroup> &Result) {
+namespace {
+/// \brief 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
+
+/// \brief 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) {
+ StmtDataCollector<FoldingSetNodeIDWrapper>(S, Sequence.getASTContext(),
+ OutputData);
+
+ for (const Stmt *Child : S->children()) {
+ if (!Child)
+ continue;
+
+ CollectStmtSequenceData(StmtSequence(Child, Sequence.getASTContext()),
+ OutputData);
+ }
+ }
+}
+
+/// \brief 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;
+}
+
+/// \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;
+ }
+
+ // 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;
+ }
+
+ // We didn't found a matching variable pattern, so we continue with the
+ // next sequence.
+ ++I;
+ }
+
+ // Add a valid clone group to the list of found clone groups.
+ if (!FilteredGroup.isValid())
+ continue;
+
+ Result.push_back(FilteredGroup);
+ }
+}
+
+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;
+
+ // 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;
+
+ // 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;
+ }
+
+ // Skip CloneSignatures that won't pass the complexity requirement.
+ if (Signature.first.Complexity < MinGroupComplexity)
+ continue;
+
+ Group.Sequences.push_back(Signature.second);
+ }
+
+ // 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;
+
+ CloneGroups.push_back(Group);
+ }
+
+ // Add every valid clone group that fulfills the complexity requirement.
+ for (const CloneGroup &Group : CloneGroups) {
+ createCloneGroups(Result, Group, CheckPatterns);
+ }
+
std::vector<unsigned> IndexesToRemove;
// Compare every group in the result with the rest. If one groups contains
@@ -366,378 +859,36 @@
}
}
-static size_t createHash(llvm::MD5 &Hash) {
- size_t HashCode;
+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);
- // Create the final hash code for the current Stmt.
- llvm::MD5::MD5Result HashResult;
- Hash.final(HashResult);
+ for (const CloneGroup &Group : Clones) {
+ for (unsigned i = 0; i < Group.Sequences.size(); ++i) {
+ VariablePattern PatternA(Group.Sequences[i]);
- // 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)));
+ for (unsigned j = i + 1; j < Group.Sequences.size(); ++j) {
+ VariablePattern PatternB(Group.Sequences[j]);
- return HashCode;
-}
-
-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();
-
- StmtDataCollector<llvm::MD5>(S, Context, Hash);
-
- auto CS = dyn_cast<CompoundStmt>(S);
- SmallVector<size_t, 8> ChildHashes;
-
- for (const Stmt *S : S->children()) {
- if (S == nullptr) {
- ChildHashes.push_back(0);
- continue;
- }
- size_t ChildHash = saveHash(S, 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) {
- for (unsigned Pos = 0; Pos <= CS->size() - Length; ++Pos) {
- llvm::MD5 Hash;
- for (unsigned i = Pos; i < Pos + Length; ++i) {
- size_t ChildHash = ChildHashes[i];
- Hash.update(StringRef(reinterpret_cast<char *>(&ChildHash),
- sizeof(ChildHash)));
- }
- StmtsByHash.push_back(std::make_pair(
- createHash(Hash), 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) {
- StmtDataCollector<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 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;
-
- 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.
- 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;
+ 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;
}
- // 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;
-}
-
-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;
- }
-
- // 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;
-}
-
-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,
- 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;
-
- // 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];
- }
-
- // Otherwise, add it to the result and continue searching for more
- // groups.
- Result.push_back(PotentialGroup);
- }
-
- assert(std::all_of(Indexes.begin(), Indexes.end(),
- [](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 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);
-}
-
-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;
}