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llvm-project/clang/lib/Analysis/ThreadSafety.cpp

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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/Analyses/PostOrderCFGView.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 "llvm/Support/raw_ostream.h"
#include <algorithm>
#include <utility>
#include <vector>
using namespace clang;
using namespace thread_safety;
// Key method definition
ThreadSafetyHandler::~ThreadSafetyHandler() {}
namespace {
/// \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 list 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. Null is used to denote 'this'.
///
/// 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 terminates on DeclRefExpr.
/// Note: this function merely creates a MutexID; it does not check to
/// ensure that the original expression is a valid mutex expression.
void buildMutexID(Expr *Exp, const NamedDecl *D, Expr *Parent,
unsigned NumArgs, Expr **FunArgs) {
if (!Exp) {
DeclSeq.clear();
return;
}
if (DeclRefExpr *DRE = dyn_cast<DeclRefExpr>(Exp)) {
NamedDecl *ND = cast<NamedDecl>(DRE->getDecl()->getCanonicalDecl());
ParmVarDecl *PV = dyn_cast_or_null<ParmVarDecl>(ND);
if (PV) {
FunctionDecl *FD =
cast<FunctionDecl>(PV->getDeclContext())->getCanonicalDecl();
unsigned i = PV->getFunctionScopeIndex();
if (FunArgs && FD == D->getCanonicalDecl()) {
// Substitute call arguments for references to function parameters
assert(i < NumArgs);
buildMutexID(FunArgs[i], D, 0, 0, 0);
return;
}
// Map the param back to the param of the original function declaration.
DeclSeq.push_back(FD->getParamDecl(i));
return;
}
// Not a function parameter -- just store the reference.
DeclSeq.push_back(ND);
} else if (MemberExpr *ME = dyn_cast<MemberExpr>(Exp)) {
NamedDecl *ND = ME->getMemberDecl();
DeclSeq.push_back(ND);
buildMutexID(ME->getBase(), D, Parent, NumArgs, FunArgs);
} else if (isa<CXXThisExpr>(Exp)) {
if (Parent)
buildMutexID(Parent, D, 0, 0, 0);
else {
DeclSeq.push_back(0); // Use 0 to represent 'this'.
return; // mutexID is still valid in this case
}
} else if (CXXMemberCallExpr *CMCE = dyn_cast<CXXMemberCallExpr>(Exp)) {
DeclSeq.push_back(CMCE->getMethodDecl()->getCanonicalDecl());
buildMutexID(CMCE->getImplicitObjectArgument(),
D, Parent, NumArgs, FunArgs);
unsigned NumCallArgs = CMCE->getNumArgs();
Expr** CallArgs = CMCE->getArgs();
for (unsigned i = 0; i < NumCallArgs; ++i) {
buildMutexID(CallArgs[i], D, Parent, NumArgs, FunArgs);
}
} else if (CallExpr *CE = dyn_cast<CallExpr>(Exp)) {
buildMutexID(CE->getCallee(), D, Parent, NumArgs, FunArgs);
unsigned NumCallArgs = CE->getNumArgs();
Expr** CallArgs = CE->getArgs();
for (unsigned i = 0; i < NumCallArgs; ++i) {
buildMutexID(CallArgs[i], D, Parent, NumArgs, FunArgs);
}
} else if (BinaryOperator *BOE = dyn_cast<BinaryOperator>(Exp)) {
buildMutexID(BOE->getLHS(), D, Parent, NumArgs, FunArgs);
buildMutexID(BOE->getRHS(), D, Parent, NumArgs, FunArgs);
} else if (UnaryOperator *UOE = dyn_cast<UnaryOperator>(Exp)) {
buildMutexID(UOE->getSubExpr(), D, Parent, NumArgs, FunArgs);
} else if (ArraySubscriptExpr *ASE = dyn_cast<ArraySubscriptExpr>(Exp)) {
buildMutexID(ASE->getBase(), D, Parent, NumArgs, FunArgs);
buildMutexID(ASE->getIdx(), D, Parent, NumArgs, FunArgs);
} else if (AbstractConditionalOperator *CE =
dyn_cast<AbstractConditionalOperator>(Exp)) {
buildMutexID(CE->getCond(), D, Parent, NumArgs, FunArgs);
buildMutexID(CE->getTrueExpr(), D, Parent, NumArgs, FunArgs);
buildMutexID(CE->getFalseExpr(), D, Parent, NumArgs, FunArgs);
} else if (ChooseExpr *CE = dyn_cast<ChooseExpr>(Exp)) {
buildMutexID(CE->getCond(), D, Parent, NumArgs, FunArgs);
buildMutexID(CE->getLHS(), D, Parent, NumArgs, FunArgs);
buildMutexID(CE->getRHS(), D, Parent, NumArgs, FunArgs);
} else if (CastExpr *CE = dyn_cast<CastExpr>(Exp)) {
buildMutexID(CE->getSubExpr(), D, Parent, NumArgs, FunArgs);
} else if (ParenExpr *PE = dyn_cast<ParenExpr>(Exp)) {
buildMutexID(PE->getSubExpr(), D, Parent, NumArgs, FunArgs);
} else if (isa<CharacterLiteral>(Exp) ||
isa<CXXNullPtrLiteralExpr>(Exp) ||
isa<GNUNullExpr>(Exp) ||
isa<CXXBoolLiteralExpr>(Exp) ||
isa<FloatingLiteral>(Exp) ||
isa<ImaginaryLiteral>(Exp) ||
isa<IntegerLiteral>(Exp) ||
isa<StringLiteral>(Exp) ||
isa<ObjCStringLiteral>(Exp)) {
return; // FIXME: Ignore literals for now
} else {
// Ignore. FIXME: mark as invalid expression?
}
}
/// \brief Construct a MutexID from an expression.
/// \param MutexExp The original mutex expression within an attribute
/// \param DeclExp An expression involving the Decl on which the attribute
/// occurs.
/// \param D The declaration to which the lock/unlock attribute is attached.
void buildMutexIDFromExp(Expr *MutexExp, Expr *DeclExp, const NamedDecl *D) {
Expr *Parent = 0;
unsigned NumArgs = 0;
Expr **FunArgs = 0;
// If we are processing a raw attribute expression, with no substitutions.
if (DeclExp == 0) {
buildMutexID(MutexExp, D, 0, 0, 0);
return;
}
// Examine DeclExp to find Parent and FunArgs, which are used to substitute
// for formal parameters when we call buildMutexID later.
if (MemberExpr *ME = dyn_cast<MemberExpr>(DeclExp)) {
Parent = ME->getBase();
} else if (CXXMemberCallExpr *CE = dyn_cast<CXXMemberCallExpr>(DeclExp)) {
Parent = CE->getImplicitObjectArgument();
NumArgs = CE->getNumArgs();
FunArgs = CE->getArgs();
} else if (CallExpr *CE = dyn_cast<CallExpr>(DeclExp)) {
NumArgs = CE->getNumArgs();
FunArgs = CE->getArgs();
} else if (CXXConstructExpr *CE = dyn_cast<CXXConstructExpr>(DeclExp)) {
Parent = 0; // FIXME -- get the parent from DeclStmt
NumArgs = CE->getNumArgs();
FunArgs = CE->getArgs();
} else if (D && isa<CXXDestructorDecl>(D)) {
// There's no such thing as a "destructor call" in the AST.
Parent = DeclExp;
}
// If the attribute has no arguments, then assume the argument is "this".
if (MutexExp == 0) {
buildMutexID(Parent, D, 0, 0, 0);
return;
}
buildMutexID(MutexExp, D, Parent, NumArgs, FunArgs);
}
public:
explicit MutexID(clang::Decl::EmptyShell e) {
DeclSeq.clear();
}
/// \param MutexExp The original mutex expression within an attribute
/// \param DeclExp An expression involving the Decl on which the attribute
/// occurs.
/// \param D The declaration to which the lock/unlock attribute is attached.
/// Caller must check isValid() after construction.
MutexID(Expr* MutexExp, Expr *DeclExp, const NamedDecl* D) {
buildMutexIDFromExp(MutexExp, DeclExp, D);
}
/// Return true if this is a valid decl sequence.
/// Caller must call this by hand after construction to handle errors.
bool isValid() const {
return !DeclSeq.empty();
}
/// Issue a warning about an invalid lock expression
static void warnInvalidLock(ThreadSafetyHandler &Handler, Expr* MutexExp,
Expr *DeclExp, const NamedDecl* D) {
SourceLocation Loc;
if (DeclExp)
Loc = DeclExp->getExprLoc();
// FIXME: add a note about the attribute location in MutexExp or D
if (Loc.isValid())
Handler.handleInvalidLockExp(Loc);
}
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.
std::string getName() const {
assert(isValid());
if (!DeclSeq.front())
return "this"; // Use 0 to represent 'this'.
return DeclSeq.front()->getNameAsString();
}
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;
MutexID UnderlyingMutex; // for ScopedLockable objects
LockData(SourceLocation AcquireLoc, LockKind LKind)
: AcquireLoc(AcquireLoc), LKind(LKind), UnderlyingMutex(Decl::EmptyShell())
{}
LockData(SourceLocation AcquireLoc, LockKind LKind, const MutexID &Mu)
: AcquireLoc(AcquireLoc), LKind(LKind), UnderlyingMutex(Mu) {}
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;
typedef llvm::ImmutableMap<NamedDecl*, unsigned> LocalVarContext;
class LocalVariableMap;
/// A side (entry or exit) of a CFG node.
enum CFGBlockSide { CBS_Entry, CBS_Exit };
/// CFGBlockInfo is a struct which contains all the information that is
/// maintained for each block in the CFG. See LocalVariableMap for more
/// information about the contexts.
struct CFGBlockInfo {
Lockset EntrySet; // Lockset held at entry to block
Lockset ExitSet; // Lockset held at exit from block
LocalVarContext EntryContext; // Context held at entry to block
LocalVarContext ExitContext; // Context held at exit from block
SourceLocation EntryLoc; // Location of first statement in block
SourceLocation ExitLoc; // Location of last statement in block.
unsigned EntryIndex; // Used to replay contexts later
const Lockset &getSet(CFGBlockSide Side) const {
return Side == CBS_Entry ? EntrySet : ExitSet;
}
SourceLocation getLocation(CFGBlockSide Side) const {
return Side == CBS_Entry ? EntryLoc : ExitLoc;
}
private:
CFGBlockInfo(Lockset EmptySet, LocalVarContext EmptyCtx)
: EntrySet(EmptySet), ExitSet(EmptySet),
EntryContext(EmptyCtx), ExitContext(EmptyCtx)
{ }
public:
static CFGBlockInfo getEmptyBlockInfo(Lockset::Factory &F,
LocalVariableMap &M);
};
// A LocalVariableMap maintains a map from local variables to their currently
// valid definitions. It provides SSA-like functionality when traversing the
// CFG. Like SSA, each definition or assignment to a variable is assigned a
// unique name (an integer), which acts as the SSA name for that definition.
// The total set of names is shared among all CFG basic blocks.
// Unlike SSA, we do not rewrite expressions to replace local variables declrefs
// with their SSA-names. Instead, we compute a Context for each point in the
// code, which maps local variables to the appropriate SSA-name. This map
// changes with each assignment.
//
// The map is computed in a single pass over the CFG. Subsequent analyses can
// then query the map to find the appropriate Context for a statement, and use
// that Context to look up the definitions of variables.
class LocalVariableMap {
public:
typedef LocalVarContext Context;
/// A VarDefinition consists of an expression, representing the value of the
/// variable, along with the context in which that expression should be
/// interpreted. A reference VarDefinition does not itself contain this
/// information, but instead contains a pointer to a previous VarDefinition.
struct VarDefinition {
public:
friend class LocalVariableMap;
NamedDecl *Dec; // The original declaration for this variable.
Expr *Exp; // The expression for this variable, OR
unsigned Ref; // Reference to another VarDefinition
Context Ctx; // The map with which Exp should be interpreted.
bool isReference() { return !Exp; }
private:
// Create ordinary variable definition
VarDefinition(NamedDecl *D, Expr *E, Context C)
: Dec(D), Exp(E), Ref(0), Ctx(C)
{ }
// Create reference to previous definition
VarDefinition(NamedDecl *D, unsigned R, Context C)
: Dec(D), Exp(0), Ref(R), Ctx(C)
{ }
};
private:
Context::Factory ContextFactory;
std::vector<VarDefinition> VarDefinitions;
std::vector<unsigned> CtxIndices;
std::vector<std::pair<Stmt*, Context> > SavedContexts;
public:
LocalVariableMap() {
// index 0 is a placeholder for undefined variables (aka phi-nodes).
VarDefinitions.push_back(VarDefinition(0, 0u, getEmptyContext()));
}
/// Look up a definition, within the given context.
const VarDefinition* lookup(NamedDecl *D, Context Ctx) {
const unsigned *i = Ctx.lookup(D);
if (!i)
return 0;
assert(*i < VarDefinitions.size());
return &VarDefinitions[*i];
}
/// Look up the definition for D within the given context. Returns
/// NULL if the expression is not statically known. If successful, also
/// modifies Ctx to hold the context of the return Expr.
Expr* lookupExpr(NamedDecl *D, Context &Ctx) {
const unsigned *P = Ctx.lookup(D);
if (!P)
return 0;
unsigned i = *P;
while (i > 0) {
if (VarDefinitions[i].Exp) {
Ctx = VarDefinitions[i].Ctx;
return VarDefinitions[i].Exp;
}
i = VarDefinitions[i].Ref;
}
return 0;
}
Context getEmptyContext() { return ContextFactory.getEmptyMap(); }
/// Return the next context after processing S. This function is used by
/// clients of the class to get the appropriate context when traversing the
/// CFG. It must be called for every assignment or DeclStmt.
Context getNextContext(unsigned &CtxIndex, Stmt *S, Context C) {
if (SavedContexts[CtxIndex+1].first == S) {
CtxIndex++;
Context Result = SavedContexts[CtxIndex].second;
return Result;
}
return C;
}
void dumpVarDefinitionName(unsigned i) {
if (i == 0) {
llvm::errs() << "Undefined";
return;
}
NamedDecl *Dec = VarDefinitions[i].Dec;
if (!Dec) {
llvm::errs() << "<<NULL>>";
return;
}
Dec->printName(llvm::errs());
llvm::errs() << "." << i << " " << ((void*) Dec);
}
/// Dumps an ASCII representation of the variable map to llvm::errs()
void dump() {
for (unsigned i = 1, e = VarDefinitions.size(); i < e; ++i) {
Expr *Exp = VarDefinitions[i].Exp;
unsigned Ref = VarDefinitions[i].Ref;
dumpVarDefinitionName(i);
llvm::errs() << " = ";
if (Exp) Exp->dump();
else {
dumpVarDefinitionName(Ref);
llvm::errs() << "\n";
}
}
}
/// Dumps an ASCII representation of a Context to llvm::errs()
void dumpContext(Context C) {
for (Context::iterator I = C.begin(), E = C.end(); I != E; ++I) {
NamedDecl *D = I.getKey();
D->printName(llvm::errs());
const unsigned *i = C.lookup(D);
llvm::errs() << " -> ";
dumpVarDefinitionName(*i);
llvm::errs() << "\n";
}
}
/// Builds the variable map.
void traverseCFG(CFG *CFGraph, PostOrderCFGView *SortedGraph,
std::vector<CFGBlockInfo> &BlockInfo);
protected:
// Get the current context index
unsigned getContextIndex() { return SavedContexts.size()-1; }
// Save the current context for later replay
void saveContext(Stmt *S, Context C) {
SavedContexts.push_back(std::make_pair(S,C));
}
// Adds a new definition to the given context, and returns a new context.
// This method should be called when declaring a new variable.
Context addDefinition(NamedDecl *D, Expr *Exp, Context Ctx) {
assert(!Ctx.contains(D));
unsigned newID = VarDefinitions.size();
Context NewCtx = ContextFactory.add(Ctx, D, newID);
VarDefinitions.push_back(VarDefinition(D, Exp, Ctx));
return NewCtx;
}
// Add a new reference to an existing definition.
Context addReference(NamedDecl *D, unsigned i, Context Ctx) {
unsigned newID = VarDefinitions.size();
Context NewCtx = ContextFactory.add(Ctx, D, newID);
VarDefinitions.push_back(VarDefinition(D, i, Ctx));
return NewCtx;
}
// Updates a definition only if that definition is already in the map.
// This method should be called when assigning to an existing variable.
Context updateDefinition(NamedDecl *D, Expr *Exp, Context Ctx) {
if (Ctx.contains(D)) {
unsigned newID = VarDefinitions.size();
Context NewCtx = ContextFactory.remove(Ctx, D);
NewCtx = ContextFactory.add(NewCtx, D, newID);
VarDefinitions.push_back(VarDefinition(D, Exp, Ctx));
return NewCtx;
}
return Ctx;
}
// Removes a definition from the context, but keeps the variable name
// as a valid variable. The index 0 is a placeholder for cleared definitions.
Context clearDefinition(NamedDecl *D, Context Ctx) {
Context NewCtx = Ctx;
if (NewCtx.contains(D)) {
NewCtx = ContextFactory.remove(NewCtx, D);
NewCtx = ContextFactory.add(NewCtx, D, 0);
}
return NewCtx;
}
// Remove a definition entirely frmo the context.
Context removeDefinition(NamedDecl *D, Context Ctx) {
Context NewCtx = Ctx;
if (NewCtx.contains(D)) {
NewCtx = ContextFactory.remove(NewCtx, D);
}
return NewCtx;
}
Context intersectContexts(Context C1, Context C2);
Context createReferenceContext(Context C);
void intersectBackEdge(Context C1, Context C2);
friend class VarMapBuilder;
};
// This has to be defined after LocalVariableMap.
CFGBlockInfo CFGBlockInfo::getEmptyBlockInfo(Lockset::Factory &F,
LocalVariableMap &M) {
return CFGBlockInfo(F.getEmptyMap(), M.getEmptyContext());
}
/// Visitor which builds a LocalVariableMap
class VarMapBuilder : public StmtVisitor<VarMapBuilder> {
public:
LocalVariableMap* VMap;
LocalVariableMap::Context Ctx;
VarMapBuilder(LocalVariableMap *VM, LocalVariableMap::Context C)
: VMap(VM), Ctx(C) {}
void VisitDeclStmt(DeclStmt *S);
void VisitBinaryOperator(BinaryOperator *BO);
};
// Add new local variables to the variable map
void VarMapBuilder::VisitDeclStmt(DeclStmt *S) {
bool modifiedCtx = false;
DeclGroupRef DGrp = S->getDeclGroup();
for (DeclGroupRef::iterator I = DGrp.begin(), E = DGrp.end(); I != E; ++I) {
if (VarDecl *VD = dyn_cast_or_null<VarDecl>(*I)) {
Expr *E = VD->getInit();
// Add local variables with trivial type to the variable map
QualType T = VD->getType();
if (T.isTrivialType(VD->getASTContext())) {
Ctx = VMap->addDefinition(VD, E, Ctx);
modifiedCtx = true;
}
}
}
if (modifiedCtx)
VMap->saveContext(S, Ctx);
}
// Update local variable definitions in variable map
void VarMapBuilder::VisitBinaryOperator(BinaryOperator *BO) {
if (!BO->isAssignmentOp())
return;
Expr *LHSExp = BO->getLHS()->IgnoreParenCasts();
// Update the variable map and current context.
if (DeclRefExpr *DRE = dyn_cast<DeclRefExpr>(LHSExp)) {
ValueDecl *VDec = DRE->getDecl();
if (Ctx.lookup(VDec)) {
if (BO->getOpcode() == BO_Assign)
Ctx = VMap->updateDefinition(VDec, BO->getRHS(), Ctx);
else
// FIXME -- handle compound assignment operators
Ctx = VMap->clearDefinition(VDec, Ctx);
VMap->saveContext(BO, Ctx);
}
}
}
// Computes the intersection of two contexts. The intersection is the
// set of variables which have the same definition in both contexts;
// variables with different definitions are discarded.
LocalVariableMap::Context
LocalVariableMap::intersectContexts(Context C1, Context C2) {
Context Result = C1;
for (Context::iterator I = C1.begin(), E = C1.end(); I != E; ++I) {
NamedDecl *Dec = I.getKey();
unsigned i1 = I.getData();
const unsigned *i2 = C2.lookup(Dec);
if (!i2) // variable doesn't exist on second path
Result = removeDefinition(Dec, Result);
else if (*i2 != i1) // variable exists, but has different definition
Result = clearDefinition(Dec, Result);
}
return Result;
}
// For every variable in C, create a new variable that refers to the
// definition in C. Return a new context that contains these new variables.
// (We use this for a naive implementation of SSA on loop back-edges.)
LocalVariableMap::Context LocalVariableMap::createReferenceContext(Context C) {
Context Result = getEmptyContext();
for (Context::iterator I = C.begin(), E = C.end(); I != E; ++I) {
NamedDecl *Dec = I.getKey();
unsigned i = I.getData();
Result = addReference(Dec, i, Result);
}
return Result;
}
// This routine also takes the intersection of C1 and C2, but it does so by
// altering the VarDefinitions. C1 must be the result of an earlier call to
// createReferenceContext.
void LocalVariableMap::intersectBackEdge(Context C1, Context C2) {
for (Context::iterator I = C1.begin(), E = C1.end(); I != E; ++I) {
NamedDecl *Dec = I.getKey();
unsigned i1 = I.getData();
VarDefinition *VDef = &VarDefinitions[i1];
assert(VDef->isReference());
const unsigned *i2 = C2.lookup(Dec);
if (!i2 || (*i2 != i1))
VDef->Ref = 0; // Mark this variable as undefined
}
}
// Traverse the CFG in topological order, so all predecessors of a block
// (excluding back-edges) are visited before the block itself. At
// each point in the code, we calculate a Context, which holds the set of
// variable definitions which are visible at that point in execution.
// Visible variables are mapped to their definitions using an array that
// contains all definitions.
//
// At join points in the CFG, the set is computed as the intersection of
// the incoming sets along each edge, E.g.
//
// { Context | VarDefinitions }
// int x = 0; { x -> x1 | x1 = 0 }
// int y = 0; { x -> x1, y -> y1 | y1 = 0, x1 = 0 }
// if (b) x = 1; { x -> x2, y -> y1 | x2 = 1, y1 = 0, ... }
// else x = 2; { x -> x3, y -> y1 | x3 = 2, x2 = 1, ... }
// ... { y -> y1 (x is unknown) | x3 = 2, x2 = 1, ... }
//
// This is essentially a simpler and more naive version of the standard SSA
// algorithm. Those definitions that remain in the intersection are from blocks
// that strictly dominate the current block. We do not bother to insert proper
// phi nodes, because they are not used in our analysis; instead, wherever
// a phi node would be required, we simply remove that definition from the
// context (E.g. x above).
//
// The initial traversal does not capture back-edges, so those need to be
// handled on a separate pass. Whenever the first pass encounters an
// incoming back edge, it duplicates the context, creating new definitions
// that refer back to the originals. (These correspond to places where SSA
// might have to insert a phi node.) On the second pass, these definitions are
// set to NULL if the the variable has changed on the back-edge (i.e. a phi
// node was actually required.) E.g.
//
// { Context | VarDefinitions }
// int x = 0, y = 0; { x -> x1, y -> y1 | y1 = 0, x1 = 0 }
// while (b) { x -> x2, y -> y1 | [1st:] x2=x1; [2nd:] x2=NULL; }
// x = x+1; { x -> x3, y -> y1 | x3 = x2 + 1, ... }
// ... { y -> y1 | x3 = 2, x2 = 1, ... }
//
void LocalVariableMap::traverseCFG(CFG *CFGraph,
PostOrderCFGView *SortedGraph,
std::vector<CFGBlockInfo> &BlockInfo) {
PostOrderCFGView::CFGBlockSet VisitedBlocks(CFGraph);
CtxIndices.resize(CFGraph->getNumBlockIDs());
for (PostOrderCFGView::iterator I = SortedGraph->begin(),
E = SortedGraph->end(); I!= E; ++I) {
const CFGBlock *CurrBlock = *I;
int CurrBlockID = CurrBlock->getBlockID();
CFGBlockInfo *CurrBlockInfo = &BlockInfo[CurrBlockID];
VisitedBlocks.insert(CurrBlock);
// Calculate the entry context for the current block
bool HasBackEdges = false;
bool CtxInit = true;
for (CFGBlock::const_pred_iterator PI = CurrBlock->pred_begin(),
PE = CurrBlock->pred_end(); PI != PE; ++PI) {
// if *PI -> CurrBlock is a back edge, so skip it
if (*PI == 0 || !VisitedBlocks.alreadySet(*PI)) {
HasBackEdges = true;
continue;
}
int PrevBlockID = (*PI)->getBlockID();
CFGBlockInfo *PrevBlockInfo = &BlockInfo[PrevBlockID];
if (CtxInit) {
CurrBlockInfo->EntryContext = PrevBlockInfo->ExitContext;
CtxInit = false;
}
else {
CurrBlockInfo->EntryContext =
intersectContexts(CurrBlockInfo->EntryContext,
PrevBlockInfo->ExitContext);
}
}
// Duplicate the context if we have back-edges, so we can call
// intersectBackEdges later.
if (HasBackEdges)
CurrBlockInfo->EntryContext =
createReferenceContext(CurrBlockInfo->EntryContext);
// Create a starting context index for the current block
saveContext(0, CurrBlockInfo->EntryContext);
CurrBlockInfo->EntryIndex = getContextIndex();
// Visit all the statements in the basic block.
VarMapBuilder VMapBuilder(this, CurrBlockInfo->EntryContext);
for (CFGBlock::const_iterator BI = CurrBlock->begin(),
BE = CurrBlock->end(); BI != BE; ++BI) {
switch (BI->getKind()) {
case CFGElement::Statement: {
const CFGStmt *CS = cast<CFGStmt>(&*BI);
VMapBuilder.Visit(const_cast<Stmt*>(CS->getStmt()));
break;
}
default:
break;
}
}
CurrBlockInfo->ExitContext = VMapBuilder.Ctx;
// Mark variables on back edges as "unknown" if they've been changed.
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;
Context LoopBegin = BlockInfo[FirstLoopBlock->getBlockID()].EntryContext;
Context LoopEnd = CurrBlockInfo->ExitContext;
intersectBackEdge(LoopBegin, LoopEnd);
}
}
// Put an extra entry at the end of the indexed context array
unsigned exitID = CFGraph->getExit().getBlockID();
saveContext(0, BlockInfo[exitID].ExitContext);
}
/// Find the appropriate source locations to use when producing diagnostics for
/// each block in the CFG.
static void findBlockLocations(CFG *CFGraph,
PostOrderCFGView *SortedGraph,
std::vector<CFGBlockInfo> &BlockInfo) {
for (PostOrderCFGView::iterator I = SortedGraph->begin(),
E = SortedGraph->end(); I!= E; ++I) {
const CFGBlock *CurrBlock = *I;
CFGBlockInfo *CurrBlockInfo = &BlockInfo[CurrBlock->getBlockID()];
// Find the source location of the last statement in the block, if the
// block is not empty.
if (const Stmt *S = CurrBlock->getTerminator()) {
CurrBlockInfo->EntryLoc = CurrBlockInfo->ExitLoc = S->getLocStart();
} else {
for (CFGBlock::const_reverse_iterator BI = CurrBlock->rbegin(),
BE = CurrBlock->rend(); BI != BE; ++BI) {
// FIXME: Handle other CFGElement kinds.
if (const CFGStmt *CS = dyn_cast<CFGStmt>(&*BI)) {
CurrBlockInfo->ExitLoc = CS->getStmt()->getLocStart();
break;
}
}
}
if (!CurrBlockInfo->ExitLoc.isInvalid()) {
// This block contains at least one statement. Find the source location
// of the first statement in the block.
for (CFGBlock::const_iterator BI = CurrBlock->begin(),
BE = CurrBlock->end(); BI != BE; ++BI) {
// FIXME: Handle other CFGElement kinds.
if (const CFGStmt *CS = dyn_cast<CFGStmt>(&*BI)) {
CurrBlockInfo->EntryLoc = CS->getStmt()->getLocStart();
break;
}
}
} else if (CurrBlock->pred_size() == 1 && *CurrBlock->pred_begin() &&
CurrBlock != &CFGraph->getExit()) {
// The block is empty, and has a single predecessor. Use its exit
// location.
CurrBlockInfo->EntryLoc = CurrBlockInfo->ExitLoc =
BlockInfo[(*CurrBlock->pred_begin())->getBlockID()].ExitLoc;
}
}
}
/// \brief Class which implements the core thread safety analysis routines.
class ThreadSafetyAnalyzer {
friend class BuildLockset;
ThreadSafetyHandler &Handler;
Lockset::Factory LocksetFactory;
LocalVariableMap LocalVarMap;
public:
ThreadSafetyAnalyzer(ThreadSafetyHandler &H) : Handler(H) {}
Lockset intersectAndWarn(const CFGBlockInfo &Block1, CFGBlockSide Side1,
const CFGBlockInfo &Block2, CFGBlockSide Side2,
LockErrorKind LEK);
Lockset addLock(Lockset &LSet, Expr *MutexExp, const NamedDecl *D,
LockKind LK, SourceLocation Loc);
void runAnalysis(AnalysisDeclContext &AC);
};
/// \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> {
friend class ThreadSafetyAnalyzer;
ThreadSafetyHandler &Handler;
Lockset::Factory &LocksetFactory;
LocalVariableMap &LocalVarMap;
Lockset LSet;
LocalVariableMap::Context LVarCtx;
unsigned CtxIndex;
// Helper functions
void addLock(const MutexID &Mutex, const LockData &LDat);
void removeLock(const MutexID &Mutex, SourceLocation UnlockLoc);
template <class AttrType>
void addLocksToSet(LockKind LK, AttrType *Attr,
Expr *Exp, NamedDecl *D, VarDecl *VD = 0);
void removeLocksFromSet(UnlockFunctionAttr *Attr,
Expr *Exp, NamedDecl* FunDecl);
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);
void handleCall(Expr *Exp, NamedDecl *D, VarDecl *VD = 0);
template <class AttrType>
void addTrylock(LockKind LK, AttrType *Attr, Expr *Exp, NamedDecl *FunDecl,
const CFGBlock* PredBlock, const CFGBlock *CurrBlock,
Expr *BrE, bool Neg);
CallExpr* getTrylockCallExpr(Stmt *Cond, LocalVariableMap::Context C,
bool &Negate);
void handleTrylock(Stmt *Cond, const CFGBlock* PredBlock,
const CFGBlock *CurrBlock);
/// \brief Returns true if the lockset contains a lock, regardless of whether
/// the lock is held exclusively or shared.
bool locksetContains(const MutexID &Lock) const {
return LSet.lookup(Lock);
}
/// \brief Returns true if the lockset contains a lock with the passed in
/// locktype.
bool locksetContains(const 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(const 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(ThreadSafetyAnalyzer *analyzer, CFGBlockInfo &Info)
: StmtVisitor<BuildLockset>(),
Handler(analyzer->Handler),
LocksetFactory(analyzer->LocksetFactory),
LocalVarMap(analyzer->LocalVarMap),
LSet(Info.EntrySet),
LVarCtx(Info.EntryContext),
CtxIndex(Info.EntryIndex)
{}
void VisitUnaryOperator(UnaryOperator *UO);
void VisitBinaryOperator(BinaryOperator *BO);
void VisitCastExpr(CastExpr *CE);
void VisitCallExpr(CallExpr *Exp);
void VisitCXXConstructExpr(CXXConstructExpr *Exp);
void VisitDeclStmt(DeclStmt *S);
};
/// \brief Add a new lock to the lockset, warning if the lock is already there.
/// \param Mutex -- the Mutex expression for the lock
/// \param LDat -- the LockData for the lock
void BuildLockset::addLock(const MutexID &Mutex, const LockData& LDat) {
// FIXME: deal with acquired before/after annotations.
// FIXME: Don't always warn when we have support for reentrant locks.
if (locksetContains(Mutex))
Handler.handleDoubleLock(Mutex.getName(), LDat.AcquireLoc);
else
LSet = LocksetFactory.add(LSet, Mutex, LDat);
}
/// \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(const MutexID &Mutex, SourceLocation UnlockLoc) {
const LockData *LDat = LSet.lookup(Mutex);
if (!LDat)
Handler.handleUnmatchedUnlock(Mutex.getName(), UnlockLoc);
else {
// For scoped-lockable vars, remove the mutex associated with this var.
if (LDat->UnderlyingMutex.isValid())
removeLock(LDat->UnderlyingMutex, UnlockLoc);
LSet = LocksetFactory.remove(LSet, Mutex);
}
}
/// \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, AttrType *Attr,
Expr *Exp, NamedDecl* FunDecl, VarDecl *VD) {
typedef typename AttrType::args_iterator iterator_type;
SourceLocation ExpLocation = Exp->getExprLoc();
// Figure out if we're calling the constructor of scoped lockable class
bool isScopedVar = false;
if (VD) {
if (CXXConstructorDecl *CD = dyn_cast<CXXConstructorDecl>(FunDecl)) {
CXXRecordDecl* PD = CD->getParent();
if (PD && PD->getAttr<ScopedLockableAttr>())
isScopedVar = true;
}
}
if (Attr->args_size() == 0) {
// The mutex held is the "this" object.
MutexID Mutex(0, Exp, FunDecl);
if (!Mutex.isValid())
MutexID::warnInvalidLock(Handler, 0, Exp, FunDecl);
else
addLock(Mutex, LockData(ExpLocation, LK));
return;
}
for (iterator_type I=Attr->args_begin(), E=Attr->args_end(); I != E; ++I) {
MutexID Mutex(*I, Exp, FunDecl);
if (!Mutex.isValid())
MutexID::warnInvalidLock(Handler, *I, Exp, FunDecl);
else {
addLock(Mutex, LockData(ExpLocation, LK));
if (isScopedVar) {
// For scoped lockable vars, map this var to its underlying mutex.
DeclRefExpr DRE(VD, VD->getType(), VK_LValue, VD->getLocation());
MutexID SMutex(&DRE, 0, 0);
addLock(SMutex, LockData(VD->getLocation(), LK, Mutex));
}
}
}
}
/// \brief This function removes a set of locks specified as attribute
/// arguments from the lockset.
void BuildLockset::removeLocksFromSet(UnlockFunctionAttr *Attr,
Expr *Exp, NamedDecl* FunDecl) {
SourceLocation ExpLocation;
if (Exp) ExpLocation = Exp->getExprLoc();
if (Attr->args_size() == 0) {
// The mutex held is the "this" object.
MutexID Mu(0, Exp, FunDecl);
if (!Mu.isValid())
MutexID::warnInvalidLock(Handler, 0, Exp, FunDecl);
else
removeLock(Mu, ExpLocation);
return;
}
for (UnlockFunctionAttr::args_iterator I = Attr->args_begin(),
E = Attr->args_end(); I != E; ++I) {
MutexID Mutex(*I, Exp, FunDecl);
if (!Mutex.isValid())
MutexID::warnInvalidLock(Handler, *I, Exp, FunDecl);
else
removeLock(Mutex, ExpLocation);
}
}
/// \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 AccessKind.
void BuildLockset::warnIfMutexNotHeld(const NamedDecl *D, Expr *Exp,
AccessKind AK, Expr *MutexExp,
ProtectedOperationKind POK) {
LockKind LK = getLockKindFromAccessKind(AK);
MutexID Mutex(MutexExp, Exp, D);
if (!Mutex.isValid())
MutexID::warnInvalidLock(Handler, MutexExp, Exp, D);
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 Process a function call, method call, constructor call,
/// or destructor call. This involves looking at the attributes on the
/// corresponding function/method/constructor/destructor, issuing warnings,
/// and updating the locksets 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::handleCall(Expr *Exp, NamedDecl *D, VarDecl *VD) {
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: {
ExclusiveLockFunctionAttr *A = cast<ExclusiveLockFunctionAttr>(Attr);
addLocksToSet(LK_Exclusive, A, Exp, D, VD);
break;
}
// When we encounter a shared lock function, we need to add the lock
// to our lockset with kind shared.
case attr::SharedLockFunction: {
SharedLockFunctionAttr *A = cast<SharedLockFunctionAttr>(Attr);
addLocksToSet(LK_Shared, A, Exp, D, VD);
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);
removeLocksFromSet(UFAttr, Exp, D);
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, Exp, D);
if (!Mutex.isValid())
MutexID::warnInvalidLock(Handler, *I, Exp, D);
else if (locksetContains(Mutex))
Handler.handleFunExcludesLock(D->getName(), Mutex.getName(),
Exp->getExprLoc());
}
break;
}
// Ignore other (non thread-safety) attributes
default:
break;
}
}
}
/// \brief Add lock to set, if the current block is in the taken branch of a
/// trylock.
template <class AttrType>
void BuildLockset::addTrylock(LockKind LK, AttrType *Attr, Expr *Exp,
NamedDecl *FunDecl, const CFGBlock *PredBlock,
const CFGBlock *CurrBlock, Expr *BrE, bool Neg) {
// Find out which branch has the lock
bool branch = 0;
if (CXXBoolLiteralExpr *BLE = dyn_cast_or_null<CXXBoolLiteralExpr>(BrE)) {
branch = BLE->getValue();
}
else if (IntegerLiteral *ILE = dyn_cast_or_null<IntegerLiteral>(BrE)) {
branch = ILE->getValue().getBoolValue();
}
int branchnum = branch ? 0 : 1;
if (Neg) branchnum = !branchnum;
// If we've taken the trylock branch, then add the lock
int i = 0;
for (CFGBlock::const_succ_iterator SI = PredBlock->succ_begin(),
SE = PredBlock->succ_end(); SI != SE && i < 2; ++SI, ++i) {
if (*SI == CurrBlock && i == branchnum) {
addLocksToSet(LK, Attr, Exp, FunDecl, 0);
}
}
}
// If Cond can be traced back to a function call, return the call expression.
// The negate variable should be called with false, and will be set to true
// if the function call is negated, e.g. if (!mu.tryLock(...))
CallExpr* BuildLockset::getTrylockCallExpr(Stmt *Cond,
LocalVariableMap::Context C,
bool &Negate) {
if (!Cond)
return 0;
if (CallExpr *CallExp = dyn_cast<CallExpr>(Cond)) {
return CallExp;
}
else if (ImplicitCastExpr *CE = dyn_cast<ImplicitCastExpr>(Cond)) {
return getTrylockCallExpr(CE->getSubExpr(), C, Negate);
}
else if (DeclRefExpr *DRE = dyn_cast<DeclRefExpr>(Cond)) {
Expr *E = LocalVarMap.lookupExpr(DRE->getDecl(), C);
return getTrylockCallExpr(E, C, Negate);
}
else if (UnaryOperator *UOP = dyn_cast<UnaryOperator>(Cond)) {
if (UOP->getOpcode() == UO_LNot) {
Negate = !Negate;
return getTrylockCallExpr(UOP->getSubExpr(), C, Negate);
}
}
// FIXME -- handle && and || as well.
return NULL;
}
/// \brief Process a conditional branch from a previous block to the current
/// block, looking for trylock calls.
void BuildLockset::handleTrylock(Stmt *Cond, const CFGBlock *PredBlock,
const CFGBlock *CurrBlock) {
bool Negate = false;
CallExpr *Exp = getTrylockCallExpr(Cond, LVarCtx, Negate);
if (!Exp)
return;
NamedDecl *FunDecl = dyn_cast_or_null<NamedDecl>(Exp->getCalleeDecl());
if(!FunDecl || !FunDecl->hasAttrs())
return;
// If the condition is a call to a Trylock function, then grab the attributes
AttrVec &ArgAttrs = FunDecl->getAttrs();
for (unsigned i = 0; i < ArgAttrs.size(); ++i) {
Attr *Attr = ArgAttrs[i];
switch (Attr->getKind()) {
case attr::ExclusiveTrylockFunction: {
ExclusiveTrylockFunctionAttr *A =
cast<ExclusiveTrylockFunctionAttr>(Attr);
addTrylock(LK_Exclusive, A, Exp, FunDecl, PredBlock, CurrBlock,
A->getSuccessValue(), Negate);
break;
}
case attr::SharedTrylockFunction: {
SharedTrylockFunctionAttr *A =
cast<SharedTrylockFunctionAttr>(Attr);
addTrylock(LK_Shared, A, Exp, FunDecl, PredBlock, CurrBlock,
A->getSuccessValue(), Negate);
break;
}
default:
break;
}
}
}
/// \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;
// adjust the context
LVarCtx = LocalVarMap.getNextContext(CtxIndex, BO, LVarCtx);
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);
}
void BuildLockset::VisitCallExpr(CallExpr *Exp) {
NamedDecl *D = dyn_cast_or_null<NamedDecl>(Exp->getCalleeDecl());
if(!D || !D->hasAttrs())
return;
handleCall(Exp, D);
}
void BuildLockset::VisitCXXConstructExpr(CXXConstructExpr *Exp) {
// FIXME -- only handles constructors in DeclStmt below.
}
void BuildLockset::VisitDeclStmt(DeclStmt *S) {
// adjust the context
LVarCtx = LocalVarMap.getNextContext(CtxIndex, S, LVarCtx);
DeclGroupRef DGrp = S->getDeclGroup();
for (DeclGroupRef::iterator I = DGrp.begin(), E = DGrp.end(); I != E; ++I) {
Decl *D = *I;
if (VarDecl *VD = dyn_cast_or_null<VarDecl>(D)) {
Expr *E = VD->getInit();
if (CXXConstructExpr *CE = dyn_cast_or_null<CXXConstructExpr>(E)) {
NamedDecl *CtorD = dyn_cast_or_null<NamedDecl>(CE->getConstructor());
if (!CtorD || !CtorD->hasAttrs())
return;
handleCall(CE, CtorD, VD);
}
}
}
}
/// \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.
Lockset ThreadSafetyAnalyzer::intersectAndWarn(const CFGBlockInfo &Block1,
CFGBlockSide Side1,
const CFGBlockInfo &Block2,
CFGBlockSide Side2,
LockErrorKind LEK) {
Lockset LSet1 = Block1.getSet(Side1);
Lockset LSet2 = Block2.getSet(Side2);
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 = LocksetFactory.add(Intersection, LSet2Mutex,
LSet2LockData);
}
} else {
Handler.handleMutexHeldEndOfScope(LSet2Mutex.getName(),
LSet2LockData.AcquireLoc,
Block1.getLocation(Side1), 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,
Block2.getLocation(Side2), LEK);
Intersection = LocksetFactory.remove(Intersection, Mutex);
}
}
return Intersection;
}
Lockset ThreadSafetyAnalyzer::addLock(Lockset &LSet, Expr *MutexExp,
const NamedDecl *D,
LockKind LK, SourceLocation Loc) {
MutexID Mutex(MutexExp, 0, D);
if (!Mutex.isValid()) {
MutexID::warnInvalidLock(Handler, MutexExp, 0, D);
return LSet;
}
LockData NewLock(Loc, LK);
return LocksetFactory.add(LSet, Mutex, NewLock);
}
/// \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 ThreadSafetyAnalyzer::runAnalysis(AnalysisDeclContext &AC) {
CFG *CFGraph = AC.getCFG();
if (!CFGraph) return;
const NamedDecl *D = dyn_cast_or_null<NamedDecl>(AC.getDecl());
if (!D)
return; // Ignore anonymous functions for now.
if (D->getAttr<NoThreadSafetyAnalysisAttr>())
return;
// FIXME: Do something a bit more intelligent inside constructor and
// destructor code. Constructors and destructors must assume unique access
// to 'this', so checks on member variable access is disabled, but we should
// still enable checks on other objects.
if (isa<CXXConstructorDecl>(D))
return; // Don't check inside constructors.
if (isa<CXXDestructorDecl>(D))
return; // Don't check inside destructors.
std::vector<CFGBlockInfo> BlockInfo(CFGraph->getNumBlockIDs(),
CFGBlockInfo::getEmptyBlockInfo(LocksetFactory, LocalVarMap));
// 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.
PostOrderCFGView *SortedGraph = AC.getAnalysis<PostOrderCFGView>();
PostOrderCFGView::CFGBlockSet VisitedBlocks(CFGraph);
// Compute SSA names for local variables
LocalVarMap.traverseCFG(CFGraph, SortedGraph, BlockInfo);
// Fill in source locations for all CFGBlocks.
findBlockLocations(CFGraph, SortedGraph, BlockInfo);
// Add locks from exclusive_locks_required and shared_locks_required
// to initial lockset. Also turn off checking for lock and unlock functions.
// FIXME: is there a more intelligent way to check lock/unlock functions?
if (!SortedGraph->empty() && D->hasAttrs()) {
const CFGBlock *FirstBlock = *SortedGraph->begin();
Lockset &InitialLockset = BlockInfo[FirstBlock->getBlockID()].EntrySet;
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(InitialLockset,
*SLRIter, D, 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(InitialLockset,
*ELRIter, D, LK_Exclusive,
AttrLoc);
} else if (isa<UnlockFunctionAttr>(Attr)) {
// Don't try to check unlock functions for now
return;
} else if (isa<ExclusiveLockFunctionAttr>(Attr)) {
// Don't try to check lock functions for now
return;
} else if (isa<SharedLockFunctionAttr>(Attr)) {
// Don't try to check lock functions for now
return;
}
}
}
for (PostOrderCFGView::iterator I = SortedGraph->begin(),
E = SortedGraph->end(); I!= E; ++I) {
const CFGBlock *CurrBlock = *I;
int CurrBlockID = CurrBlock->getBlockID();
CFGBlockInfo *CurrBlockInfo = &BlockInfo[CurrBlockID];
// Use the default initial lockset in case there are no predecessors.
VisitedBlocks.insert(CurrBlock);
// 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;
llvm::SmallVector<CFGBlock*, 8> SpecialBlocks;
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;
// Ignore edges from blocks that can't return.
if ((*PI)->hasNoReturnElement())
continue;
// If the previous block ended in a 'continue' or 'break' statement, then
// a difference in locksets is probably due to a bug in that block, rather
// than in some other predecessor. In that case, keep the other
// predecessor's lockset.
if (const Stmt *Terminator = (*PI)->getTerminator()) {
if (isa<ContinueStmt>(Terminator) || isa<BreakStmt>(Terminator)) {
SpecialBlocks.push_back(*PI);
continue;
}
}
int PrevBlockID = (*PI)->getBlockID();
CFGBlockInfo *PrevBlockInfo = &BlockInfo[PrevBlockID];
if (!LocksetInitialized) {
CurrBlockInfo->EntrySet = PrevBlockInfo->ExitSet;
LocksetInitialized = true;
} else {
CurrBlockInfo->EntrySet =
intersectAndWarn(*CurrBlockInfo, CBS_Entry,
*PrevBlockInfo, CBS_Exit,
LEK_LockedSomePredecessors);
}
}
// Process continue and break blocks. Assume that the lockset for the
// resulting block is unaffected by any discrepancies in them.
for (unsigned SpecialI = 0, SpecialN = SpecialBlocks.size();
SpecialI < SpecialN; ++SpecialI) {
CFGBlock *PrevBlock = SpecialBlocks[SpecialI];
int PrevBlockID = PrevBlock->getBlockID();
CFGBlockInfo *PrevBlockInfo = &BlockInfo[PrevBlockID];
if (!LocksetInitialized) {
CurrBlockInfo->EntrySet = PrevBlockInfo->ExitSet;
LocksetInitialized = true;
} else {
// Determine whether this edge is a loop terminator for diagnostic
// purposes. FIXME: A 'break' statement might be a loop terminator, but
// it might also be part of a switch. Also, a subsequent destructor
// might add to the lockset, in which case the real issue might be a
// double lock on the other path.
const Stmt *Terminator = PrevBlock->getTerminator();
bool IsLoop = Terminator && isa<ContinueStmt>(Terminator);
// Do not update EntrySet.
intersectAndWarn(*CurrBlockInfo, CBS_Entry, *PrevBlockInfo, CBS_Exit,
IsLoop ? LEK_LockedSomeLoopIterations
: LEK_LockedSomePredecessors);
}
}
BuildLockset LocksetBuilder(this, *CurrBlockInfo);
CFGBlock::const_pred_iterator PI = CurrBlock->pred_begin(),
PE = CurrBlock->pred_end();
if (PI != PE) {
// If the predecessor ended in a branch, then process any trylocks.
// FIXME -- check to make sure there's only one predecessor.
if (Stmt *TCE = (*PI)->getTerminatorCondition()) {
LocksetBuilder.handleTrylock(TCE, *PI, CurrBlock);
}
}
// Visit all the statements in the basic block.
for (CFGBlock::const_iterator BI = CurrBlock->begin(),
BE = CurrBlock->end(); BI != BE; ++BI) {
switch (BI->getKind()) {
case CFGElement::Statement: {
const CFGStmt *CS = cast<CFGStmt>(&*BI);
LocksetBuilder.Visit(const_cast<Stmt*>(CS->getStmt()));
break;
}
// Ignore BaseDtor, MemberDtor, and TemporaryDtor for now.
case CFGElement::AutomaticObjectDtor: {
const CFGAutomaticObjDtor *AD = cast<CFGAutomaticObjDtor>(&*BI);
CXXDestructorDecl *DD = const_cast<CXXDestructorDecl*>(
AD->getDestructorDecl(AC.getASTContext()));
if (!DD->hasAttrs())
break;
// Create a dummy expression,
VarDecl *VD = const_cast<VarDecl*>(AD->getVarDecl());
DeclRefExpr DRE(VD, VD->getType(), VK_LValue,
AD->getTriggerStmt()->getLocEnd());
LocksetBuilder.handleCall(&DRE, DD);
break;
}
default:
break;
}
}
CurrBlockInfo->ExitSet = LocksetBuilder.LSet;
// 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;
CFGBlockInfo &PreLoop = BlockInfo[FirstLoopBlock->getBlockID()];
CFGBlockInfo &LoopEnd = BlockInfo[CurrBlockID];
intersectAndWarn(LoopEnd, CBS_Exit, PreLoop, CBS_Entry,
LEK_LockedSomeLoopIterations);
}
}
CFGBlockInfo &Initial = BlockInfo[CFGraph->getEntry().getBlockID()];
CFGBlockInfo &Final = BlockInfo[CFGraph->getExit().getBlockID()];
// FIXME: Should we call this function for all blocks which exit the function?
intersectAndWarn(Initial, CBS_Entry, Final, CBS_Exit,
LEK_LockedAtEndOfFunction);
}
} // end anonymous namespace
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(AnalysisDeclContext &AC,
ThreadSafetyHandler &Handler) {
ThreadSafetyAnalyzer Analyzer(Handler);
Analyzer.runAnalysis(AC);
}
/// \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
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