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+//===- ThreadSafety.cpp ----------------------------------------*- C++ --*-===//
+//
+// The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// A intra-procedural analysis for thread safety (e.g. deadlocks and race
+// conditions), based off of an annotation system.
+//
+// See http://clang.llvm.org/docs/LanguageExtensions.html#threadsafety for more
+// information.
+//
+//===----------------------------------------------------------------------===//
+
+#include "clang/Analysis/Analyses/ThreadSafety.h"
+#include "clang/Analysis/AnalysisContext.h"
+#include "clang/Analysis/CFG.h"
+#include "clang/Analysis/CFGStmtMap.h"
+#include "clang/AST/DeclCXX.h"
+#include "clang/AST/ExprCXX.h"
+#include "clang/AST/StmtCXX.h"
+#include "clang/AST/StmtVisitor.h"
+#include "clang/Basic/SourceManager.h"
+#include "clang/Basic/SourceLocation.h"
+#include "llvm/ADT/BitVector.h"
+#include "llvm/ADT/FoldingSet.h"
+#include "llvm/ADT/ImmutableMap.h"
+#include "llvm/ADT/PostOrderIterator.h"
+#include "llvm/ADT/SmallVector.h"
+#include "llvm/ADT/StringRef.h"
+#include <algorithm>
+#include <vector>
+
+using namespace clang;
+using namespace thread_safety;
+
+// Key method definition
+ThreadSafetyHandler::~ThreadSafetyHandler() {}
+
+// Helper function
+static Expr *getParent(Expr *Exp) {
+ if (MemberExpr *ME = dyn_cast<MemberExpr>(Exp))
+ return ME->getBase();
+ if (CXXMemberCallExpr *CE = dyn_cast<CXXMemberCallExpr>(Exp))
+ return CE->getImplicitObjectArgument();
+ return 0;
+}
+
+namespace {
+/// \brief Implements a set of CFGBlocks using a BitVector.
+///
+/// This class contains a minimal interface, primarily dictated by the SetType
+/// template parameter of the llvm::po_iterator template, as used with external
+/// storage. We also use this set to keep track of which CFGBlocks we visit
+/// during the analysis.
+class CFGBlockSet {
+ llvm::BitVector VisitedBlockIDs;
+
+public:
+ // po_iterator requires this iterator, but the only interface needed is the
+ // value_type typedef.
+ struct iterator {
+ typedef const CFGBlock *value_type;
+ };
+
+ CFGBlockSet() {}
+ CFGBlockSet(const CFG *G) : VisitedBlockIDs(G->getNumBlockIDs(), false) {}
+
+ /// \brief Set the bit associated with a particular CFGBlock.
+ /// This is the important method for the SetType template parameter.
+ bool insert(const CFGBlock *Block) {
+ // Note that insert() is called by po_iterator, which doesn't check to make
+ // sure that Block is non-null. Moreover, the CFGBlock iterator will
+ // occasionally hand out null pointers for pruned edges, so we catch those
+ // here.
+ if (Block == 0)
+ return false; // if an edge is trivially false.
+ if (VisitedBlockIDs.test(Block->getBlockID()))
+ return false;
+ VisitedBlockIDs.set(Block->getBlockID());
+ return true;
+ }
+
+ /// \brief Check if the bit for a CFGBlock has been already set.
+ /// This method is for tracking visited blocks in the main threadsafety loop.
+ /// Block must not be null.
+ bool alreadySet(const CFGBlock *Block) {
+ return VisitedBlockIDs.test(Block->getBlockID());
+ }
+};
+
+/// \brief We create a helper class which we use to iterate through CFGBlocks in
+/// the topological order.
+class TopologicallySortedCFG {
+ typedef llvm::po_iterator<const CFG*, CFGBlockSet, true> po_iterator;
+
+ std::vector<const CFGBlock*> Blocks;
+
+public:
+ typedef std::vector<const CFGBlock*>::reverse_iterator iterator;
+
+ TopologicallySortedCFG(const CFG *CFGraph) {
+ Blocks.reserve(CFGraph->getNumBlockIDs());
+ CFGBlockSet BSet(CFGraph);
+
+ for (po_iterator I = po_iterator::begin(CFGraph, BSet),
+ E = po_iterator::end(CFGraph, BSet); I != E; ++I) {
+ Blocks.push_back(*I);
+ }
+ }
+
+ iterator begin() {
+ return Blocks.rbegin();
+ }
+
+ iterator end() {
+ return Blocks.rend();
+ }
+
+ bool empty() {
+ return begin() == end();
+ }
+};
+
+/// \brief A MutexID object uniquely identifies a particular mutex, and
+/// is built from an Expr* (i.e. calling a lock function).
+///
+/// Thread-safety analysis works by comparing lock expressions. Within the
+/// body of a function, an expression such as "x->foo->bar.mu" will resolve to
+/// a particular mutex object at run-time. Subsequent occurrences of the same
+/// expression (where "same" means syntactic equality) will refer to the same
+/// run-time object if three conditions hold:
+/// (1) Local variables in the expression, such as "x" have not changed.
+/// (2) Values on the heap that affect the expression have not changed.
+/// (3) The expression involves only pure function calls.
+/// The current implementation assumes, but does not verify, that multiple uses
+/// of the same lock expression satisfies these criteria.
+///
+/// Clang introduces an additional wrinkle, which is that it is difficult to
+/// derive canonical expressions, or compare expressions directly for equality.
+/// Thus, we identify a mutex not by an Expr, but by the set of named
+/// declarations that are referenced by the Expr. In other words,
+/// x->foo->bar.mu will be a four element vector with the Decls for
+/// mu, bar, and foo, and x. The vector will uniquely identify the expression
+/// for all practical purposes.
+///
+/// Note we will need to perform substitution on "this" and function parameter
+/// names when constructing a lock expression.
+///
+/// For example:
+/// class C { Mutex Mu; void lock() EXCLUSIVE_LOCK_FUNCTION(this->Mu); };
+/// void myFunc(C *X) { ... X->lock() ... }
+/// The original expression for the mutex acquired by myFunc is "this->Mu", but
+/// "X" is substituted for "this" so we get X->Mu();
+///
+/// For another example:
+/// foo(MyList *L) EXCLUSIVE_LOCKS_REQUIRED(L->Mu) { ... }
+/// MyList *MyL;
+/// foo(MyL); // requires lock MyL->Mu to be held
+class MutexID {
+ SmallVector<NamedDecl*, 2> DeclSeq;
+
+ /// Build a Decl sequence representing the lock from the given expression.
+ /// Recursive function that bottoms out when the final DeclRefExpr is reached.
+ // FIXME: Lock expressions that involve array indices or function calls.
+ // FIXME: Deal with LockReturned attribute.
+ void buildMutexID(Expr *Exp, Expr *Parent) {
+ if (DeclRefExpr *DRE = dyn_cast<DeclRefExpr>(Exp)) {
+ NamedDecl *ND = cast<NamedDecl>(DRE->getDecl()->getCanonicalDecl());
+ DeclSeq.push_back(ND);
+ } else if (MemberExpr *ME = dyn_cast<MemberExpr>(Exp)) {
+ NamedDecl *ND = ME->getMemberDecl();
+ DeclSeq.push_back(ND);
+ buildMutexID(ME->getBase(), Parent);
+ } else if (isa<CXXThisExpr>(Exp)) {
+ if (Parent)
+ buildMutexID(Parent, 0);
+ else
+ return; // mutexID is still valid in this case
+ } else if (CastExpr *CE = dyn_cast<CastExpr>(Exp))
+ buildMutexID(CE->getSubExpr(), Parent);
+ else
+ DeclSeq.clear(); // invalid lock expression
+ }
+
+public:
+ MutexID(Expr *LExpr, Expr *ParentExpr) {
+ buildMutexID(LExpr, ParentExpr);
+ }
+
+ /// If we encounter part of a lock expression we cannot parse
+ bool isValid() const {
+ return !DeclSeq.empty();
+ }
+
+ bool operator==(const MutexID &other) const {
+ return DeclSeq == other.DeclSeq;
+ }
+
+ bool operator!=(const MutexID &other) const {
+ return !(*this == other);
+ }
+
+ // SmallVector overloads Operator< to do lexicographic ordering. Note that
+ // we use pointer equality (and <) to compare NamedDecls. This means the order
+ // of MutexIDs in a lockset is nondeterministic. In order to output
+ // diagnostics in a deterministic ordering, we must order all diagnostics to
+ // output by SourceLocation when iterating through this lockset.
+ bool operator<(const MutexID &other) const {
+ return DeclSeq < other.DeclSeq;
+ }
+
+ /// \brief Returns the name of the first Decl in the list for a given MutexID;
+ /// e.g. the lock expression foo.bar() has name "bar".
+ /// The caret will point unambiguously to the lock expression, so using this
+ /// name in diagnostics is a way to get simple, and consistent, mutex names.
+ /// We do not want to output the entire expression text for security reasons.
+ StringRef getName() const {
+ assert(isValid());
+ return DeclSeq.front()->getName();
+ }
+
+ void Profile(llvm::FoldingSetNodeID &ID) const {
+ for (SmallVectorImpl<NamedDecl*>::const_iterator I = DeclSeq.begin(),
+ E = DeclSeq.end(); I != E; ++I) {
+ ID.AddPointer(*I);
+ }
+ }
+};
+
+/// \brief This is a helper class that stores info about the most recent
+/// accquire of a Lock.
+///
+/// The main body of the analysis maps MutexIDs to LockDatas.
+struct LockData {
+ SourceLocation AcquireLoc;
+
+ /// \brief LKind stores whether a lock is held shared or exclusively.
+ /// Note that this analysis does not currently support either re-entrant
+ /// locking or lock "upgrading" and "downgrading" between exclusive and
+ /// shared.
+ ///
+ /// FIXME: add support for re-entrant locking and lock up/downgrading
+ LockKind LKind;
+
+ LockData(SourceLocation AcquireLoc, LockKind LKind)
+ : AcquireLoc(AcquireLoc), LKind(LKind) {}
+
+ bool operator==(const LockData &other) const {
+ return AcquireLoc == other.AcquireLoc && LKind == other.LKind;
+ }
+
+ bool operator!=(const LockData &other) const {
+ return !(*this == other);
+ }
+
+ void Profile(llvm::FoldingSetNodeID &ID) const {
+ ID.AddInteger(AcquireLoc.getRawEncoding());
+ ID.AddInteger(LKind);
+ }
+};
+
+/// A Lockset maps each MutexID (defined above) to information about how it has
+/// been locked.
+typedef llvm::ImmutableMap<MutexID, LockData> Lockset;
+
+/// \brief We use this class to visit different types of expressions in
+/// CFGBlocks, and build up the lockset.
+/// An expression may cause us to add or remove locks from the lockset, or else
+/// output error messages related to missing locks.
+/// FIXME: In future, we may be able to not inherit from a visitor.
+class BuildLockset : public StmtVisitor<BuildLockset> {
+ ThreadSafetyHandler &Handler;
+ Lockset LSet;
+ Lockset::Factory &LocksetFactory;
+
+ // Helper functions
+ void removeLock(SourceLocation UnlockLoc, Expr *LockExp, Expr *Parent);
+ void addLock(SourceLocation LockLoc, Expr *LockExp, Expr *Parent,
+ LockKind LK);
+ const ValueDecl *getValueDecl(Expr *Exp);
+ void warnIfMutexNotHeld (const NamedDecl *D, Expr *Exp, AccessKind AK,
+ Expr *MutexExp, ProtectedOperationKind POK);
+ void checkAccess(Expr *Exp, AccessKind AK);
+ void checkDereference(Expr *Exp, AccessKind AK);
+
+ template <class AttrType>
+ void addLocksToSet(LockKind LK, Attr *Attr, CXXMemberCallExpr *Exp);
+
+ /// \brief Returns true if the lockset contains a lock, regardless of whether
+ /// the lock is held exclusively or shared.
+ bool locksetContains(MutexID Lock) const {
+ return LSet.lookup(Lock);
+ }
+
+ /// \brief Returns true if the lockset contains a lock with the passed in
+ /// locktype.
+ bool locksetContains(MutexID Lock, LockKind KindRequested) const {
+ const LockData *LockHeld = LSet.lookup(Lock);
+ return (LockHeld && KindRequested == LockHeld->LKind);
+ }
+
+ /// \brief Returns true if the lockset contains a lock with at least the
+ /// passed in locktype. So for example, if we pass in LK_Shared, this function
+ /// returns true if the lock is held LK_Shared or LK_Exclusive. If we pass in
+ /// LK_Exclusive, this function returns true if the lock is held LK_Exclusive.
+ bool locksetContainsAtLeast(MutexID Lock, LockKind KindRequested) const {
+ switch (KindRequested) {
+ case LK_Shared:
+ return locksetContains(Lock);
+ case LK_Exclusive:
+ return locksetContains(Lock, KindRequested);
+ }
+ llvm_unreachable("Unknown LockKind");
+ }
+
+public:
+ BuildLockset(ThreadSafetyHandler &Handler, Lockset LS, Lockset::Factory &F)
+ : StmtVisitor<BuildLockset>(), Handler(Handler), LSet(LS),
+ LocksetFactory(F) {}
+
+ Lockset getLockset() {
+ return LSet;
+ }
+
+ void VisitUnaryOperator(UnaryOperator *UO);
+ void VisitBinaryOperator(BinaryOperator *BO);
+ void VisitCastExpr(CastExpr *CE);
+ void VisitCXXMemberCallExpr(CXXMemberCallExpr *Exp);
+};
+
+/// \brief Add a new lock to the lockset, warning if the lock is already there.
+/// \param LockLoc The source location of the acquire
+/// \param LockExp The lock expression corresponding to the lock to be added
+void BuildLockset::addLock(SourceLocation LockLoc, Expr *LockExp, Expr *Parent,
+ LockKind LK) {
+ // FIXME: deal with acquired before/after annotations. We can write a first
+ // pass that does the transitive lookup lazily, and refine afterwards.
+ MutexID Mutex(LockExp, Parent);
+ if (!Mutex.isValid()) {
+ Handler.handleInvalidLockExp(LockExp->getExprLoc());
+ return;
+ }
+
+ LockData NewLock(LockLoc, LK);
+
+ // FIXME: Don't always warn when we have support for reentrant locks.
+ if (locksetContains(Mutex))
+ Handler.handleDoubleLock(Mutex.getName(), LockLoc);
+ LSet = LocksetFactory.add(LSet, Mutex, NewLock);
+}
+
+/// \brief Remove a lock from the lockset, warning if the lock is not there.
+/// \param LockExp The lock expression corresponding to the lock to be removed
+/// \param UnlockLoc The source location of the unlock (only used in error msg)
+void BuildLockset::removeLock(SourceLocation UnlockLoc, Expr *LockExp,
+ Expr *Parent) {
+ MutexID Mutex(LockExp, Parent);
+ if (!Mutex.isValid()) {
+ Handler.handleInvalidLockExp(LockExp->getExprLoc());
+ return;
+ }
+
+ Lockset NewLSet = LocksetFactory.remove(LSet, Mutex);
+ if(NewLSet == LSet)
+ Handler.handleUnmatchedUnlock(Mutex.getName(), UnlockLoc);
+
+ LSet = NewLSet;
+}
+
+/// \brief Gets the value decl pointer from DeclRefExprs or MemberExprs
+const ValueDecl *BuildLockset::getValueDecl(Expr *Exp) {
+ if (const DeclRefExpr *DR = dyn_cast<DeclRefExpr>(Exp))
+ return DR->getDecl();
+
+ if (const MemberExpr *ME = dyn_cast<MemberExpr>(Exp))
+ return ME->getMemberDecl();
+
+ return 0;
+}
+
+/// \brief Warn if the LSet does not contain a lock sufficient to protect access
+/// of at least the passed in AccessType.
+void BuildLockset::warnIfMutexNotHeld(const NamedDecl *D, Expr *Exp,
+ AccessKind AK, Expr *MutexExp,
+ ProtectedOperationKind POK) {
+ LockKind LK = getLockKindFromAccessKind(AK);
+ Expr *Parent = getParent(Exp);
+ MutexID Mutex(MutexExp, Parent);
+ if (!Mutex.isValid())
+ Handler.handleInvalidLockExp(MutexExp->getExprLoc());
+ else if (!locksetContainsAtLeast(Mutex, LK))
+ Handler.handleMutexNotHeld(D, POK, Mutex.getName(), LK, Exp->getExprLoc());
+}
+
+
+/// \brief This method identifies variable dereferences and checks pt_guarded_by
+/// and pt_guarded_var annotations. Note that we only check these annotations
+/// at the time a pointer is dereferenced.
+/// FIXME: We need to check for other types of pointer dereferences
+/// (e.g. [], ->) and deal with them here.
+/// \param Exp An expression that has been read or written.
+void BuildLockset::checkDereference(Expr *Exp, AccessKind AK) {
+ UnaryOperator *UO = dyn_cast<UnaryOperator>(Exp);
+ if (!UO || UO->getOpcode() != clang::UO_Deref)
+ return;
+ Exp = UO->getSubExpr()->IgnoreParenCasts();
+
+ const ValueDecl *D = getValueDecl(Exp);
+ if(!D || !D->hasAttrs())
+ return;
+
+ if (D->getAttr<PtGuardedVarAttr>() && LSet.isEmpty())
+ Handler.handleNoMutexHeld(D, POK_VarDereference, AK, Exp->getExprLoc());
+
+ const AttrVec &ArgAttrs = D->getAttrs();
+ for(unsigned i = 0, Size = ArgAttrs.size(); i < Size; ++i)
+ if (PtGuardedByAttr *PGBAttr = dyn_cast<PtGuardedByAttr>(ArgAttrs[i]))
+ warnIfMutexNotHeld(D, Exp, AK, PGBAttr->getArg(), POK_VarDereference);
+}
+
+/// \brief Checks guarded_by and guarded_var attributes.
+/// Whenever we identify an access (read or write) of a DeclRefExpr or
+/// MemberExpr, we need to check whether there are any guarded_by or
+/// guarded_var attributes, and make sure we hold the appropriate mutexes.
+void BuildLockset::checkAccess(Expr *Exp, AccessKind AK) {
+ const ValueDecl *D = getValueDecl(Exp);
+ if(!D || !D->hasAttrs())
+ return;
+
+ if (D->getAttr<GuardedVarAttr>() && LSet.isEmpty())
+ Handler.handleNoMutexHeld(D, POK_VarAccess, AK, Exp->getExprLoc());
+
+ const AttrVec &ArgAttrs = D->getAttrs();
+ for(unsigned i = 0, Size = ArgAttrs.size(); i < Size; ++i)
+ if (GuardedByAttr *GBAttr = dyn_cast<GuardedByAttr>(ArgAttrs[i]))
+ warnIfMutexNotHeld(D, Exp, AK, GBAttr->getArg(), POK_VarAccess);
+}
+
+/// \brief For unary operations which read and write a variable, we need to
+/// check whether we hold any required mutexes. Reads are checked in
+/// VisitCastExpr.
+void BuildLockset::VisitUnaryOperator(UnaryOperator *UO) {
+ switch (UO->getOpcode()) {
+ case clang::UO_PostDec:
+ case clang::UO_PostInc:
+ case clang::UO_PreDec:
+ case clang::UO_PreInc: {
+ Expr *SubExp = UO->getSubExpr()->IgnoreParenCasts();
+ checkAccess(SubExp, AK_Written);
+ checkDereference(SubExp, AK_Written);
+ break;
+ }
+ default:
+ break;
+ }
+}
+
+/// For binary operations which assign to a variable (writes), we need to check
+/// whether we hold any required mutexes.
+/// FIXME: Deal with non-primitive types.
+void BuildLockset::VisitBinaryOperator(BinaryOperator *BO) {
+ if (!BO->isAssignmentOp())
+ return;
+ Expr *LHSExp = BO->getLHS()->IgnoreParenCasts();
+ checkAccess(LHSExp, AK_Written);
+ checkDereference(LHSExp, AK_Written);
+}
+
+/// Whenever we do an LValue to Rvalue cast, we are reading a variable and
+/// need to ensure we hold any required mutexes.
+/// FIXME: Deal with non-primitive types.
+void BuildLockset::VisitCastExpr(CastExpr *CE) {
+ if (CE->getCastKind() != CK_LValueToRValue)
+ return;
+ Expr *SubExp = CE->getSubExpr()->IgnoreParenCasts();
+ checkAccess(SubExp, AK_Read);
+ checkDereference(SubExp, AK_Read);
+}
+
+/// \brief This function, parameterized by an attribute type, is used to add a
+/// set of locks specified as attribute arguments to the lockset.
+template <typename AttrType>
+void BuildLockset::addLocksToSet(LockKind LK, Attr *Attr,
+ CXXMemberCallExpr *Exp) {
+ typedef typename AttrType::args_iterator iterator_type;
+ SourceLocation ExpLocation = Exp->getExprLoc();
+ Expr *Parent = Exp->getImplicitObjectArgument();
+ AttrType *SpecificAttr = cast<AttrType>(Attr);
+
+ if (SpecificAttr->args_size() == 0) {
+ // The mutex held is the "this" object.
+ addLock(ExpLocation, Parent, 0, LK);
+ return;
+ }
+
+ for (iterator_type I = SpecificAttr->args_begin(),
+ E = SpecificAttr->args_end(); I != E; ++I)
+ addLock(ExpLocation, *I, Parent, LK);
+}
+
+/// \brief When visiting CXXMemberCallExprs we need to examine the attributes on
+/// the method that is being called and add, remove or check locks in the
+/// lockset accordingly.
+///
+/// FIXME: For classes annotated with one of the guarded annotations, we need
+/// to treat const method calls as reads and non-const method calls as writes,
+/// and check that the appropriate locks are held. Non-const method calls with
+/// the same signature as const method calls can be also treated as reads.
+///
+/// FIXME: We need to also visit CallExprs to catch/check global functions.
+///
+/// FIXME: Do not flag an error for member variables accessed in constructors/
+/// destructors
+void BuildLockset::VisitCXXMemberCallExpr(CXXMemberCallExpr *Exp) {
+ NamedDecl *D = dyn_cast_or_null<NamedDecl>(Exp->getCalleeDecl());
+
+ SourceLocation ExpLocation = Exp->getExprLoc();
+ Expr *Parent = Exp->getImplicitObjectArgument();
+
+ if(!D || !D->hasAttrs())
+ return;
+
+ AttrVec &ArgAttrs = D->getAttrs();
+ for(unsigned i = 0; i < ArgAttrs.size(); ++i) {
+ Attr *Attr = ArgAttrs[i];
+ switch (Attr->getKind()) {
+ // When we encounter an exclusive lock function, we need to add the lock
+ // to our lockset with kind exclusive.
+ case attr::ExclusiveLockFunction:
+ addLocksToSet<ExclusiveLockFunctionAttr>(LK_Exclusive, Attr, Exp);
+ break;
+
+ // When we encounter a shared lock function, we need to add the lock
+ // to our lockset with kind shared.
+ case attr::SharedLockFunction:
+ addLocksToSet<SharedLockFunctionAttr>(LK_Shared, Attr, Exp);
+ break;
+
+ // When we encounter an unlock function, we need to remove unlocked
+ // mutexes from the lockset, and flag a warning if they are not there.
+ case attr::UnlockFunction: {
+ UnlockFunctionAttr *UFAttr = cast<UnlockFunctionAttr>(Attr);
+
+ if (UFAttr->args_size() == 0) { // The lock held is the "this" object.
+ removeLock(ExpLocation, Parent, 0);
+ break;
+ }
+
+ for (UnlockFunctionAttr::args_iterator I = UFAttr->args_begin(),
+ E = UFAttr->args_end(); I != E; ++I)
+ removeLock(ExpLocation, *I, Parent);
+ break;
+ }
+
+ case attr::ExclusiveLocksRequired: {
+ ExclusiveLocksRequiredAttr *ELRAttr =
+ cast<ExclusiveLocksRequiredAttr>(Attr);
+
+ for (ExclusiveLocksRequiredAttr::args_iterator
+ I = ELRAttr->args_begin(), E = ELRAttr->args_end(); I != E; ++I)
+ warnIfMutexNotHeld(D, Exp, AK_Written, *I, POK_FunctionCall);
+ break;
+ }
+
+ case attr::SharedLocksRequired: {
+ SharedLocksRequiredAttr *SLRAttr = cast<SharedLocksRequiredAttr>(Attr);
+
+ for (SharedLocksRequiredAttr::args_iterator I = SLRAttr->args_begin(),
+ E = SLRAttr->args_end(); I != E; ++I)
+ warnIfMutexNotHeld(D, Exp, AK_Read, *I, POK_FunctionCall);
+ break;
+ }
+
+ case attr::LocksExcluded: {
+ LocksExcludedAttr *LEAttr = cast<LocksExcludedAttr>(Attr);
+ for (LocksExcludedAttr::args_iterator I = LEAttr->args_begin(),
+ E = LEAttr->args_end(); I != E; ++I) {
+ MutexID Mutex(*I, Parent);
+ if (!Mutex.isValid())
+ Handler.handleInvalidLockExp((*I)->getExprLoc());
+ else if (locksetContains(Mutex))
+ Handler.handleFunExcludesLock(D->getName(), Mutex.getName(),
+ ExpLocation);
+ }
+ break;
+ }
+
+ // Ignore other (non thread-safety) attributes
+ default:
+ break;
+ }
+ }
+}
+
+} // end anonymous namespace
+
+/// \brief Compute the intersection of two locksets and issue warnings for any
+/// locks in the symmetric difference.
+///
+/// This function is used at a merge point in the CFG when comparing the lockset
+/// of each branch being merged. For example, given the following sequence:
+/// A; if () then B; else C; D; we need to check that the lockset after B and C
+/// are the same. In the event of a difference, we use the intersection of these
+/// two locksets at the start of D.
+static Lockset intersectAndWarn(ThreadSafetyHandler &Handler,
+ const Lockset LSet1, const Lockset LSet2,
+ Lockset::Factory &Fact, LockErrorKind LEK) {
+ Lockset Intersection = LSet1;
+ for (Lockset::iterator I = LSet2.begin(), E = LSet2.end(); I != E; ++I) {
+ const MutexID &LSet2Mutex = I.getKey();
+ const LockData &LSet2LockData = I.getData();
+ if (const LockData *LD = LSet1.lookup(LSet2Mutex)) {
+ if (LD->LKind != LSet2LockData.LKind) {
+ Handler.handleExclusiveAndShared(LSet2Mutex.getName(),
+ LSet2LockData.AcquireLoc,
+ LD->AcquireLoc);
+ if (LD->LKind != LK_Exclusive)
+ Intersection = Fact.add(Intersection, LSet2Mutex, LSet2LockData);
+ }
+ } else {
+ Handler.handleMutexHeldEndOfScope(LSet2Mutex.getName(),
+ LSet2LockData.AcquireLoc, LEK);
+ }
+ }
+
+ for (Lockset::iterator I = LSet1.begin(), E = LSet1.end(); I != E; ++I) {
+ if (!LSet2.contains(I.getKey())) {
+ const MutexID &Mutex = I.getKey();
+ const LockData &MissingLock = I.getData();
+ Handler.handleMutexHeldEndOfScope(Mutex.getName(),
+ MissingLock.AcquireLoc, LEK);
+ Intersection = Fact.remove(Intersection, Mutex);
+ }
+ }
+ return Intersection;
+}
+
+static Lockset addLock(ThreadSafetyHandler &Handler,
+ Lockset::Factory &LocksetFactory,
+ Lockset &LSet, Expr *LockExp, LockKind LK,
+ SourceLocation Loc) {
+ MutexID Mutex(LockExp, 0);
+ if (!Mutex.isValid()) {
+ Handler.handleInvalidLockExp(LockExp->getExprLoc());
+ return LSet;
+ }
+ LockData NewLock(Loc, LK);
+ return LocksetFactory.add(LSet, Mutex, NewLock);
+}
+
+namespace clang {
+namespace thread_safety {
+/// \brief Check a function's CFG for thread-safety violations.
+///
+/// We traverse the blocks in the CFG, compute the set of mutexes that are held
+/// at the end of each block, and issue warnings for thread safety violations.
+/// Each block in the CFG is traversed exactly once.
+void runThreadSafetyAnalysis(AnalysisContext &AC,
+ ThreadSafetyHandler &Handler) {
+ CFG *CFGraph = AC.getCFG();
+ if (!CFGraph) return;
+ const Decl *D = AC.getDecl();
+ if (D && D->getAttr<NoThreadSafetyAnalysisAttr>()) return;
+
+ Lockset::Factory LocksetFactory;
+
+ // FIXME: Swith to SmallVector? Otherwise improve performance impact?
+ std::vector<Lockset> EntryLocksets(CFGraph->getNumBlockIDs(),
+ LocksetFactory.getEmptyMap());
+ std::vector<Lockset> ExitLocksets(CFGraph->getNumBlockIDs(),
+ LocksetFactory.getEmptyMap());
+
+ // We need to explore the CFG via a "topological" ordering.
+ // That way, we will be guaranteed to have information about required
+ // predecessor locksets when exploring a new block.
+ TopologicallySortedCFG SortedGraph(CFGraph);
+ CFGBlockSet VisitedBlocks(CFGraph);
+
+ if (!SortedGraph.empty() && D->hasAttrs()) {
+ const CFGBlock *FirstBlock = *SortedGraph.begin();
+ Lockset &InitialLockset = EntryLocksets[FirstBlock->getBlockID()];
+ const AttrVec &ArgAttrs = D->getAttrs();
+ for(unsigned i = 0; i < ArgAttrs.size(); ++i) {
+ Attr *Attr = ArgAttrs[i];
+ SourceLocation AttrLoc = Attr->getLocation();
+ if (SharedLocksRequiredAttr *SLRAttr
+ = dyn_cast<SharedLocksRequiredAttr>(Attr)) {
+ for (SharedLocksRequiredAttr::args_iterator
+ SLRIter = SLRAttr->args_begin(),
+ SLREnd = SLRAttr->args_end(); SLRIter != SLREnd; ++SLRIter)
+ InitialLockset = addLock(Handler, LocksetFactory, InitialLockset,
+ *SLRIter, LK_Shared,
+ AttrLoc);
+ } else if (ExclusiveLocksRequiredAttr *ELRAttr
+ = dyn_cast<ExclusiveLocksRequiredAttr>(Attr)) {
+ for (ExclusiveLocksRequiredAttr::args_iterator
+ ELRIter = ELRAttr->args_begin(),
+ ELREnd = ELRAttr->args_end(); ELRIter != ELREnd; ++ELRIter)
+ InitialLockset = addLock(Handler, LocksetFactory, InitialLockset,
+ *ELRIter, LK_Exclusive,
+ AttrLoc);
+ }
+ }
+ }
+
+ for (TopologicallySortedCFG::iterator I = SortedGraph.begin(),
+ E = SortedGraph.end(); I!= E; ++I) {
+ const CFGBlock *CurrBlock = *I;
+ int CurrBlockID = CurrBlock->getBlockID();
+
+ VisitedBlocks.insert(CurrBlock);
+
+ // Use the default initial lockset in case there are no predecessors.
+ Lockset &Entryset = EntryLocksets[CurrBlockID];
+ Lockset &Exitset = ExitLocksets[CurrBlockID];
+
+ // Iterate through the predecessor blocks and warn if the lockset for all
+ // predecessors is not the same. We take the entry lockset of the current
+ // block to be the intersection of all previous locksets.
+ // FIXME: By keeping the intersection, we may output more errors in future
+ // for a lock which is not in the intersection, but was in the union. We
+ // may want to also keep the union in future. As an example, let's say
+ // the intersection contains Mutex L, and the union contains L and M.
+ // Later we unlock M. At this point, we would output an error because we
+ // never locked M; although the real error is probably that we forgot to
+ // lock M on all code paths. Conversely, let's say that later we lock M.
+ // In this case, we should compare against the intersection instead of the
+ // union because the real error is probably that we forgot to unlock M on
+ // all code paths.
+ bool LocksetInitialized = false;
+ for (CFGBlock::const_pred_iterator PI = CurrBlock->pred_begin(),
+ PE = CurrBlock->pred_end(); PI != PE; ++PI) {
+
+ // if *PI -> CurrBlock is a back edge
+ if (*PI == 0 || !VisitedBlocks.alreadySet(*PI))
+ continue;
+
+ int PrevBlockID = (*PI)->getBlockID();
+ if (!LocksetInitialized) {
+ Entryset = ExitLocksets[PrevBlockID];
+ LocksetInitialized = true;
+ } else {
+ Entryset = intersectAndWarn(Handler, Entryset,
+ ExitLocksets[PrevBlockID], LocksetFactory,
+ LEK_LockedSomePredecessors);
+ }
+ }
+
+ BuildLockset LocksetBuilder(Handler, Entryset, LocksetFactory);
+ for (CFGBlock::const_iterator BI = CurrBlock->begin(),
+ BE = CurrBlock->end(); BI != BE; ++BI) {
+ if (const CFGStmt *CfgStmt = dyn_cast<CFGStmt>(&*BI))
+ LocksetBuilder.Visit(const_cast<Stmt*>(CfgStmt->getStmt()));
+ }
+ Exitset = LocksetBuilder.getLockset();
+
+ // For every back edge from CurrBlock (the end of the loop) to another block
+ // (FirstLoopBlock) we need to check that the Lockset of Block is equal to
+ // the one held at the beginning of FirstLoopBlock. We can look up the
+ // Lockset held at the beginning of FirstLoopBlock in the EntryLockSets map.
+ for (CFGBlock::const_succ_iterator SI = CurrBlock->succ_begin(),
+ SE = CurrBlock->succ_end(); SI != SE; ++SI) {
+
+ // if CurrBlock -> *SI is *not* a back edge
+ if (*SI == 0 || !VisitedBlocks.alreadySet(*SI))
+ continue;
+
+ CFGBlock *FirstLoopBlock = *SI;
+ Lockset PreLoop = EntryLocksets[FirstLoopBlock->getBlockID()];
+ Lockset LoopEnd = ExitLocksets[CurrBlockID];
+ intersectAndWarn(Handler, LoopEnd, PreLoop, LocksetFactory,
+ LEK_LockedSomeLoopIterations);
+ }
+ }
+
+ Lockset InitialLockset = EntryLocksets[CFGraph->getEntry().getBlockID()];
+ Lockset FinalLockset = ExitLocksets[CFGraph->getExit().getBlockID()];
+
+ // FIXME: Should we call this function for all blocks which exit the function?
+ intersectAndWarn(Handler, InitialLockset, FinalLockset, LocksetFactory,
+ LEK_LockedAtEndOfFunction);
+}
+
+/// \brief Helper function that returns a LockKind required for the given level
+/// of access.
+LockKind getLockKindFromAccessKind(AccessKind AK) {
+ switch (AK) {
+ case AK_Read :
+ return LK_Shared;
+ case AK_Written :
+ return LK_Exclusive;
+ }
+ llvm_unreachable("Unknown AccessKind");
+}
+}} // end namespace clang::thread_safety