ThreadSafety.cpp revision f63797c741e646b9482d204c88dee02fb41d7962
1//===- ThreadSafety.cpp ----------------------------------------*- C++ --*-===// 2// 3// The LLVM Compiler Infrastructure 4// 5// This file is distributed under the University of Illinois Open Source 6// License. See LICENSE.TXT for details. 7// 8//===----------------------------------------------------------------------===// 9// 10// A intra-procedural analysis for thread safety (e.g. deadlocks and race 11// conditions), based off of an annotation system. 12// 13// See http://clang.llvm.org/docs/LanguageExtensions.html#threadsafety for more 14// information. 15// 16//===----------------------------------------------------------------------===// 17 18#include "clang/Analysis/Analyses/ThreadSafety.h" 19#include "clang/Analysis/Analyses/PostOrderCFGView.h" 20#include "clang/Analysis/AnalysisContext.h" 21#include "clang/Analysis/CFG.h" 22#include "clang/Analysis/CFGStmtMap.h" 23#include "clang/AST/DeclCXX.h" 24#include "clang/AST/ExprCXX.h" 25#include "clang/AST/StmtCXX.h" 26#include "clang/AST/StmtVisitor.h" 27#include "clang/Basic/SourceManager.h" 28#include "clang/Basic/SourceLocation.h" 29#include "llvm/ADT/BitVector.h" 30#include "llvm/ADT/FoldingSet.h" 31#include "llvm/ADT/ImmutableMap.h" 32#include "llvm/ADT/PostOrderIterator.h" 33#include "llvm/ADT/SmallVector.h" 34#include "llvm/ADT/StringRef.h" 35#include "llvm/Support/raw_ostream.h" 36#include <algorithm> 37#include <utility> 38#include <vector> 39 40using namespace clang; 41using namespace thread_safety; 42 43// Key method definition 44ThreadSafetyHandler::~ThreadSafetyHandler() {} 45 46namespace { 47 48/// \brief A MutexID object uniquely identifies a particular mutex, and 49/// is built from an Expr* (i.e. calling a lock function). 50/// 51/// Thread-safety analysis works by comparing lock expressions. Within the 52/// body of a function, an expression such as "x->foo->bar.mu" will resolve to 53/// a particular mutex object at run-time. Subsequent occurrences of the same 54/// expression (where "same" means syntactic equality) will refer to the same 55/// run-time object if three conditions hold: 56/// (1) Local variables in the expression, such as "x" have not changed. 57/// (2) Values on the heap that affect the expression have not changed. 58/// (3) The expression involves only pure function calls. 59/// 60/// The current implementation assumes, but does not verify, that multiple uses 61/// of the same lock expression satisfies these criteria. 62/// 63/// Clang introduces an additional wrinkle, which is that it is difficult to 64/// derive canonical expressions, or compare expressions directly for equality. 65/// Thus, we identify a mutex not by an Expr, but by the list of named 66/// declarations that are referenced by the Expr. In other words, 67/// x->foo->bar.mu will be a four element vector with the Decls for 68/// mu, bar, and foo, and x. The vector will uniquely identify the expression 69/// for all practical purposes. Null is used to denote 'this'. 70/// 71/// Note we will need to perform substitution on "this" and function parameter 72/// names when constructing a lock expression. 73/// 74/// For example: 75/// class C { Mutex Mu; void lock() EXCLUSIVE_LOCK_FUNCTION(this->Mu); }; 76/// void myFunc(C *X) { ... X->lock() ... } 77/// The original expression for the mutex acquired by myFunc is "this->Mu", but 78/// "X" is substituted for "this" so we get X->Mu(); 79/// 80/// For another example: 81/// foo(MyList *L) EXCLUSIVE_LOCKS_REQUIRED(L->Mu) { ... } 82/// MyList *MyL; 83/// foo(MyL); // requires lock MyL->Mu to be held 84class MutexID { 85 SmallVector<NamedDecl*, 2> DeclSeq; 86 87 /// \brief Encapsulates the lexical context of a function call. The lexical 88 /// context includes the arguments to the call, including the implicit object 89 /// argument. When an attribute containing a mutex expression is attached to 90 /// a method, the expression may refer to formal parameters of the method. 91 /// Actual arguments must be substituted for formal parameters to derive 92 /// the appropriate mutex expression in the lexical context where the function 93 /// is called. PrevCtx holds the context in which the arguments themselves 94 /// should be evaluated; multiple calling contexts can be chained together 95 /// by the lock_returned attribute. 96 struct CallingContext { 97 const NamedDecl* AttrDecl; // The decl to which the attribute is attached. 98 Expr* SelfArg; // Implicit object argument -- e.g. 'this' 99 unsigned NumArgs; // Number of funArgs 100 Expr** FunArgs; // Function arguments 101 CallingContext* PrevCtx; // The previous context; or 0 if none. 102 103 CallingContext(const NamedDecl* D = 0, Expr* S = 0, 104 unsigned N = 0, Expr** A = 0, CallingContext* P = 0) 105 : AttrDecl(D), SelfArg(S), NumArgs(N), FunArgs(A), PrevCtx(P) 106 { } 107 }; 108 109 /// Build a Decl sequence representing the lock from the given expression. 110 /// Recursive function that terminates on DeclRefExpr. 111 /// Note: this function merely creates a MutexID; it does not check to 112 /// ensure that the original expression is a valid mutex expression. 113 void buildMutexID(Expr *Exp, CallingContext* CallCtx) { 114 if (!Exp) { 115 DeclSeq.clear(); 116 return; 117 } 118 119 if (DeclRefExpr *DRE = dyn_cast<DeclRefExpr>(Exp)) { 120 NamedDecl *ND = cast<NamedDecl>(DRE->getDecl()->getCanonicalDecl()); 121 ParmVarDecl *PV = dyn_cast_or_null<ParmVarDecl>(ND); 122 if (PV) { 123 FunctionDecl *FD = 124 cast<FunctionDecl>(PV->getDeclContext())->getCanonicalDecl(); 125 unsigned i = PV->getFunctionScopeIndex(); 126 127 if (CallCtx && CallCtx->FunArgs && 128 FD == CallCtx->AttrDecl->getCanonicalDecl()) { 129 // Substitute call arguments for references to function parameters 130 assert(i < CallCtx->NumArgs); 131 buildMutexID(CallCtx->FunArgs[i], CallCtx->PrevCtx); 132 return; 133 } 134 // Map the param back to the param of the original function declaration. 135 DeclSeq.push_back(FD->getParamDecl(i)); 136 return; 137 } 138 // Not a function parameter -- just store the reference. 139 DeclSeq.push_back(ND); 140 } else if (isa<CXXThisExpr>(Exp)) { 141 // Substitute parent for 'this' 142 if (CallCtx && CallCtx->SelfArg) 143 buildMutexID(CallCtx->SelfArg, CallCtx->PrevCtx); 144 else { 145 DeclSeq.push_back(0); // Use 0 to represent 'this'. 146 return; // mutexID is still valid in this case 147 } 148 } else if (MemberExpr *ME = dyn_cast<MemberExpr>(Exp)) { 149 NamedDecl *ND = ME->getMemberDecl(); 150 DeclSeq.push_back(ND); 151 buildMutexID(ME->getBase(), CallCtx); 152 } else if (CXXMemberCallExpr *CMCE = dyn_cast<CXXMemberCallExpr>(Exp)) { 153 // When calling a function with a lock_returned attribute, replace 154 // the function call with the expression in lock_returned. 155 if (LockReturnedAttr* At = 156 CMCE->getMethodDecl()->getAttr<LockReturnedAttr>()) { 157 CallingContext LRCallCtx(CMCE->getMethodDecl()); 158 LRCallCtx.SelfArg = CMCE->getImplicitObjectArgument(); 159 LRCallCtx.NumArgs = CMCE->getNumArgs(); 160 LRCallCtx.FunArgs = CMCE->getArgs(); 161 LRCallCtx.PrevCtx = CallCtx; 162 buildMutexID(At->getArg(), &LRCallCtx); 163 return; 164 } 165 DeclSeq.push_back(CMCE->getMethodDecl()->getCanonicalDecl()); 166 buildMutexID(CMCE->getImplicitObjectArgument(), CallCtx); 167 unsigned NumCallArgs = CMCE->getNumArgs(); 168 Expr** CallArgs = CMCE->getArgs(); 169 for (unsigned i = 0; i < NumCallArgs; ++i) { 170 buildMutexID(CallArgs[i], CallCtx); 171 } 172 } else if (CallExpr *CE = dyn_cast<CallExpr>(Exp)) { 173 if (LockReturnedAttr* At = 174 CE->getDirectCallee()->getAttr<LockReturnedAttr>()) { 175 CallingContext LRCallCtx(CE->getDirectCallee()); 176 LRCallCtx.NumArgs = CE->getNumArgs(); 177 LRCallCtx.FunArgs = CE->getArgs(); 178 LRCallCtx.PrevCtx = CallCtx; 179 buildMutexID(At->getArg(), &LRCallCtx); 180 return; 181 } 182 buildMutexID(CE->getCallee(), CallCtx); 183 unsigned NumCallArgs = CE->getNumArgs(); 184 Expr** CallArgs = CE->getArgs(); 185 for (unsigned i = 0; i < NumCallArgs; ++i) { 186 buildMutexID(CallArgs[i], CallCtx); 187 } 188 } else if (BinaryOperator *BOE = dyn_cast<BinaryOperator>(Exp)) { 189 buildMutexID(BOE->getLHS(), CallCtx); 190 buildMutexID(BOE->getRHS(), CallCtx); 191 } else if (UnaryOperator *UOE = dyn_cast<UnaryOperator>(Exp)) { 192 buildMutexID(UOE->getSubExpr(), CallCtx); 193 } else if (ArraySubscriptExpr *ASE = dyn_cast<ArraySubscriptExpr>(Exp)) { 194 buildMutexID(ASE->getBase(), CallCtx); 195 buildMutexID(ASE->getIdx(), CallCtx); 196 } else if (AbstractConditionalOperator *CE = 197 dyn_cast<AbstractConditionalOperator>(Exp)) { 198 buildMutexID(CE->getCond(), CallCtx); 199 buildMutexID(CE->getTrueExpr(), CallCtx); 200 buildMutexID(CE->getFalseExpr(), CallCtx); 201 } else if (ChooseExpr *CE = dyn_cast<ChooseExpr>(Exp)) { 202 buildMutexID(CE->getCond(), CallCtx); 203 buildMutexID(CE->getLHS(), CallCtx); 204 buildMutexID(CE->getRHS(), CallCtx); 205 } else if (CastExpr *CE = dyn_cast<CastExpr>(Exp)) { 206 buildMutexID(CE->getSubExpr(), CallCtx); 207 } else if (ParenExpr *PE = dyn_cast<ParenExpr>(Exp)) { 208 buildMutexID(PE->getSubExpr(), CallCtx); 209 } else if (isa<CharacterLiteral>(Exp) || 210 isa<CXXNullPtrLiteralExpr>(Exp) || 211 isa<GNUNullExpr>(Exp) || 212 isa<CXXBoolLiteralExpr>(Exp) || 213 isa<FloatingLiteral>(Exp) || 214 isa<ImaginaryLiteral>(Exp) || 215 isa<IntegerLiteral>(Exp) || 216 isa<StringLiteral>(Exp) || 217 isa<ObjCStringLiteral>(Exp)) { 218 return; // FIXME: Ignore literals for now 219 } else { 220 // Ignore. FIXME: mark as invalid expression? 221 } 222 } 223 224 /// \brief Construct a MutexID from an expression. 225 /// \param MutexExp The original mutex expression within an attribute 226 /// \param DeclExp An expression involving the Decl on which the attribute 227 /// occurs. 228 /// \param D The declaration to which the lock/unlock attribute is attached. 229 void buildMutexIDFromExp(Expr *MutexExp, Expr *DeclExp, const NamedDecl *D) { 230 CallingContext CallCtx(D); 231 232 // If we are processing a raw attribute expression, with no substitutions. 233 if (DeclExp == 0) { 234 buildMutexID(MutexExp, 0); 235 return; 236 } 237 238 // Examine DeclExp to find SelfArg and FunArgs, which are used to substitute 239 // for formal parameters when we call buildMutexID later. 240 if (MemberExpr *ME = dyn_cast<MemberExpr>(DeclExp)) { 241 CallCtx.SelfArg = ME->getBase(); 242 } else if (CXXMemberCallExpr *CE = dyn_cast<CXXMemberCallExpr>(DeclExp)) { 243 CallCtx.SelfArg = CE->getImplicitObjectArgument(); 244 CallCtx.NumArgs = CE->getNumArgs(); 245 CallCtx.FunArgs = CE->getArgs(); 246 } else if (CallExpr *CE = dyn_cast<CallExpr>(DeclExp)) { 247 CallCtx.NumArgs = CE->getNumArgs(); 248 CallCtx.FunArgs = CE->getArgs(); 249 } else if (CXXConstructExpr *CE = dyn_cast<CXXConstructExpr>(DeclExp)) { 250 CallCtx.SelfArg = 0; // FIXME -- get the parent from DeclStmt 251 CallCtx.NumArgs = CE->getNumArgs(); 252 CallCtx.FunArgs = CE->getArgs(); 253 } else if (D && isa<CXXDestructorDecl>(D)) { 254 // There's no such thing as a "destructor call" in the AST. 255 CallCtx.SelfArg = DeclExp; 256 } 257 258 // If the attribute has no arguments, then assume the argument is "this". 259 if (MutexExp == 0) { 260 buildMutexID(CallCtx.SelfArg, 0); 261 return; 262 } 263 264 // For most attributes. 265 buildMutexID(MutexExp, &CallCtx); 266 } 267 268public: 269 explicit MutexID(clang::Decl::EmptyShell e) { 270 DeclSeq.clear(); 271 } 272 273 /// \param MutexExp The original mutex expression within an attribute 274 /// \param DeclExp An expression involving the Decl on which the attribute 275 /// occurs. 276 /// \param D The declaration to which the lock/unlock attribute is attached. 277 /// Caller must check isValid() after construction. 278 MutexID(Expr* MutexExp, Expr *DeclExp, const NamedDecl* D) { 279 buildMutexIDFromExp(MutexExp, DeclExp, D); 280 } 281 282 /// Return true if this is a valid decl sequence. 283 /// Caller must call this by hand after construction to handle errors. 284 bool isValid() const { 285 return !DeclSeq.empty(); 286 } 287 288 /// Issue a warning about an invalid lock expression 289 static void warnInvalidLock(ThreadSafetyHandler &Handler, Expr* MutexExp, 290 Expr *DeclExp, const NamedDecl* D) { 291 SourceLocation Loc; 292 if (DeclExp) 293 Loc = DeclExp->getExprLoc(); 294 295 // FIXME: add a note about the attribute location in MutexExp or D 296 if (Loc.isValid()) 297 Handler.handleInvalidLockExp(Loc); 298 } 299 300 bool operator==(const MutexID &other) const { 301 return DeclSeq == other.DeclSeq; 302 } 303 304 bool operator!=(const MutexID &other) const { 305 return !(*this == other); 306 } 307 308 // SmallVector overloads Operator< to do lexicographic ordering. Note that 309 // we use pointer equality (and <) to compare NamedDecls. This means the order 310 // of MutexIDs in a lockset is nondeterministic. In order to output 311 // diagnostics in a deterministic ordering, we must order all diagnostics to 312 // output by SourceLocation when iterating through this lockset. 313 bool operator<(const MutexID &other) const { 314 return DeclSeq < other.DeclSeq; 315 } 316 317 /// \brief Returns the name of the first Decl in the list for a given MutexID; 318 /// e.g. the lock expression foo.bar() has name "bar". 319 /// The caret will point unambiguously to the lock expression, so using this 320 /// name in diagnostics is a way to get simple, and consistent, mutex names. 321 /// We do not want to output the entire expression text for security reasons. 322 std::string getName() const { 323 assert(isValid()); 324 if (!DeclSeq.front()) 325 return "this"; // Use 0 to represent 'this'. 326 return DeclSeq.front()->getNameAsString(); 327 } 328 329 void Profile(llvm::FoldingSetNodeID &ID) const { 330 for (SmallVectorImpl<NamedDecl*>::const_iterator I = DeclSeq.begin(), 331 E = DeclSeq.end(); I != E; ++I) { 332 ID.AddPointer(*I); 333 } 334 } 335}; 336 337 338/// \brief This is a helper class that stores info about the most recent 339/// accquire of a Lock. 340/// 341/// The main body of the analysis maps MutexIDs to LockDatas. 342struct LockData { 343 SourceLocation AcquireLoc; 344 345 /// \brief LKind stores whether a lock is held shared or exclusively. 346 /// Note that this analysis does not currently support either re-entrant 347 /// locking or lock "upgrading" and "downgrading" between exclusive and 348 /// shared. 349 /// 350 /// FIXME: add support for re-entrant locking and lock up/downgrading 351 LockKind LKind; 352 MutexID UnderlyingMutex; // for ScopedLockable objects 353 354 LockData(SourceLocation AcquireLoc, LockKind LKind) 355 : AcquireLoc(AcquireLoc), LKind(LKind), UnderlyingMutex(Decl::EmptyShell()) 356 {} 357 358 LockData(SourceLocation AcquireLoc, LockKind LKind, const MutexID &Mu) 359 : AcquireLoc(AcquireLoc), LKind(LKind), UnderlyingMutex(Mu) {} 360 361 bool operator==(const LockData &other) const { 362 return AcquireLoc == other.AcquireLoc && LKind == other.LKind; 363 } 364 365 bool operator!=(const LockData &other) const { 366 return !(*this == other); 367 } 368 369 void Profile(llvm::FoldingSetNodeID &ID) const { 370 ID.AddInteger(AcquireLoc.getRawEncoding()); 371 ID.AddInteger(LKind); 372 } 373}; 374 375 376/// A Lockset maps each MutexID (defined above) to information about how it has 377/// been locked. 378typedef llvm::ImmutableMap<MutexID, LockData> Lockset; 379typedef llvm::ImmutableMap<const NamedDecl*, unsigned> LocalVarContext; 380 381class LocalVariableMap; 382 383/// A side (entry or exit) of a CFG node. 384enum CFGBlockSide { CBS_Entry, CBS_Exit }; 385 386/// CFGBlockInfo is a struct which contains all the information that is 387/// maintained for each block in the CFG. See LocalVariableMap for more 388/// information about the contexts. 389struct CFGBlockInfo { 390 Lockset EntrySet; // Lockset held at entry to block 391 Lockset ExitSet; // Lockset held at exit from block 392 LocalVarContext EntryContext; // Context held at entry to block 393 LocalVarContext ExitContext; // Context held at exit from block 394 SourceLocation EntryLoc; // Location of first statement in block 395 SourceLocation ExitLoc; // Location of last statement in block. 396 unsigned EntryIndex; // Used to replay contexts later 397 398 const Lockset &getSet(CFGBlockSide Side) const { 399 return Side == CBS_Entry ? EntrySet : ExitSet; 400 } 401 SourceLocation getLocation(CFGBlockSide Side) const { 402 return Side == CBS_Entry ? EntryLoc : ExitLoc; 403 } 404 405private: 406 CFGBlockInfo(Lockset EmptySet, LocalVarContext EmptyCtx) 407 : EntrySet(EmptySet), ExitSet(EmptySet), 408 EntryContext(EmptyCtx), ExitContext(EmptyCtx) 409 { } 410 411public: 412 static CFGBlockInfo getEmptyBlockInfo(Lockset::Factory &F, 413 LocalVariableMap &M); 414}; 415 416 417 418// A LocalVariableMap maintains a map from local variables to their currently 419// valid definitions. It provides SSA-like functionality when traversing the 420// CFG. Like SSA, each definition or assignment to a variable is assigned a 421// unique name (an integer), which acts as the SSA name for that definition. 422// The total set of names is shared among all CFG basic blocks. 423// Unlike SSA, we do not rewrite expressions to replace local variables declrefs 424// with their SSA-names. Instead, we compute a Context for each point in the 425// code, which maps local variables to the appropriate SSA-name. This map 426// changes with each assignment. 427// 428// The map is computed in a single pass over the CFG. Subsequent analyses can 429// then query the map to find the appropriate Context for a statement, and use 430// that Context to look up the definitions of variables. 431class LocalVariableMap { 432public: 433 typedef LocalVarContext Context; 434 435 /// A VarDefinition consists of an expression, representing the value of the 436 /// variable, along with the context in which that expression should be 437 /// interpreted. A reference VarDefinition does not itself contain this 438 /// information, but instead contains a pointer to a previous VarDefinition. 439 struct VarDefinition { 440 public: 441 friend class LocalVariableMap; 442 443 const NamedDecl *Dec; // The original declaration for this variable. 444 const Expr *Exp; // The expression for this variable, OR 445 unsigned Ref; // Reference to another VarDefinition 446 Context Ctx; // The map with which Exp should be interpreted. 447 448 bool isReference() { return !Exp; } 449 450 private: 451 // Create ordinary variable definition 452 VarDefinition(const NamedDecl *D, const Expr *E, Context C) 453 : Dec(D), Exp(E), Ref(0), Ctx(C) 454 { } 455 456 // Create reference to previous definition 457 VarDefinition(const NamedDecl *D, unsigned R, Context C) 458 : Dec(D), Exp(0), Ref(R), Ctx(C) 459 { } 460 }; 461 462private: 463 Context::Factory ContextFactory; 464 std::vector<VarDefinition> VarDefinitions; 465 std::vector<unsigned> CtxIndices; 466 std::vector<std::pair<Stmt*, Context> > SavedContexts; 467 468public: 469 LocalVariableMap() { 470 // index 0 is a placeholder for undefined variables (aka phi-nodes). 471 VarDefinitions.push_back(VarDefinition(0, 0u, getEmptyContext())); 472 } 473 474 /// Look up a definition, within the given context. 475 const VarDefinition* lookup(const NamedDecl *D, Context Ctx) { 476 const unsigned *i = Ctx.lookup(D); 477 if (!i) 478 return 0; 479 assert(*i < VarDefinitions.size()); 480 return &VarDefinitions[*i]; 481 } 482 483 /// Look up the definition for D within the given context. Returns 484 /// NULL if the expression is not statically known. If successful, also 485 /// modifies Ctx to hold the context of the return Expr. 486 const Expr* lookupExpr(const NamedDecl *D, Context &Ctx) { 487 const unsigned *P = Ctx.lookup(D); 488 if (!P) 489 return 0; 490 491 unsigned i = *P; 492 while (i > 0) { 493 if (VarDefinitions[i].Exp) { 494 Ctx = VarDefinitions[i].Ctx; 495 return VarDefinitions[i].Exp; 496 } 497 i = VarDefinitions[i].Ref; 498 } 499 return 0; 500 } 501 502 Context getEmptyContext() { return ContextFactory.getEmptyMap(); } 503 504 /// Return the next context after processing S. This function is used by 505 /// clients of the class to get the appropriate context when traversing the 506 /// CFG. It must be called for every assignment or DeclStmt. 507 Context getNextContext(unsigned &CtxIndex, Stmt *S, Context C) { 508 if (SavedContexts[CtxIndex+1].first == S) { 509 CtxIndex++; 510 Context Result = SavedContexts[CtxIndex].second; 511 return Result; 512 } 513 return C; 514 } 515 516 void dumpVarDefinitionName(unsigned i) { 517 if (i == 0) { 518 llvm::errs() << "Undefined"; 519 return; 520 } 521 const NamedDecl *Dec = VarDefinitions[i].Dec; 522 if (!Dec) { 523 llvm::errs() << "<<NULL>>"; 524 return; 525 } 526 Dec->printName(llvm::errs()); 527 llvm::errs() << "." << i << " " << ((void*) Dec); 528 } 529 530 /// Dumps an ASCII representation of the variable map to llvm::errs() 531 void dump() { 532 for (unsigned i = 1, e = VarDefinitions.size(); i < e; ++i) { 533 const Expr *Exp = VarDefinitions[i].Exp; 534 unsigned Ref = VarDefinitions[i].Ref; 535 536 dumpVarDefinitionName(i); 537 llvm::errs() << " = "; 538 if (Exp) Exp->dump(); 539 else { 540 dumpVarDefinitionName(Ref); 541 llvm::errs() << "\n"; 542 } 543 } 544 } 545 546 /// Dumps an ASCII representation of a Context to llvm::errs() 547 void dumpContext(Context C) { 548 for (Context::iterator I = C.begin(), E = C.end(); I != E; ++I) { 549 const NamedDecl *D = I.getKey(); 550 D->printName(llvm::errs()); 551 const unsigned *i = C.lookup(D); 552 llvm::errs() << " -> "; 553 dumpVarDefinitionName(*i); 554 llvm::errs() << "\n"; 555 } 556 } 557 558 /// Builds the variable map. 559 void traverseCFG(CFG *CFGraph, PostOrderCFGView *SortedGraph, 560 std::vector<CFGBlockInfo> &BlockInfo); 561 562protected: 563 // Get the current context index 564 unsigned getContextIndex() { return SavedContexts.size()-1; } 565 566 // Save the current context for later replay 567 void saveContext(Stmt *S, Context C) { 568 SavedContexts.push_back(std::make_pair(S,C)); 569 } 570 571 // Adds a new definition to the given context, and returns a new context. 572 // This method should be called when declaring a new variable. 573 Context addDefinition(const NamedDecl *D, Expr *Exp, Context Ctx) { 574 assert(!Ctx.contains(D)); 575 unsigned newID = VarDefinitions.size(); 576 Context NewCtx = ContextFactory.add(Ctx, D, newID); 577 VarDefinitions.push_back(VarDefinition(D, Exp, Ctx)); 578 return NewCtx; 579 } 580 581 // Add a new reference to an existing definition. 582 Context addReference(const NamedDecl *D, unsigned i, Context Ctx) { 583 unsigned newID = VarDefinitions.size(); 584 Context NewCtx = ContextFactory.add(Ctx, D, newID); 585 VarDefinitions.push_back(VarDefinition(D, i, Ctx)); 586 return NewCtx; 587 } 588 589 // Updates a definition only if that definition is already in the map. 590 // This method should be called when assigning to an existing variable. 591 Context updateDefinition(const NamedDecl *D, Expr *Exp, Context Ctx) { 592 if (Ctx.contains(D)) { 593 unsigned newID = VarDefinitions.size(); 594 Context NewCtx = ContextFactory.remove(Ctx, D); 595 NewCtx = ContextFactory.add(NewCtx, D, newID); 596 VarDefinitions.push_back(VarDefinition(D, Exp, Ctx)); 597 return NewCtx; 598 } 599 return Ctx; 600 } 601 602 // Removes a definition from the context, but keeps the variable name 603 // as a valid variable. The index 0 is a placeholder for cleared definitions. 604 Context clearDefinition(const NamedDecl *D, Context Ctx) { 605 Context NewCtx = Ctx; 606 if (NewCtx.contains(D)) { 607 NewCtx = ContextFactory.remove(NewCtx, D); 608 NewCtx = ContextFactory.add(NewCtx, D, 0); 609 } 610 return NewCtx; 611 } 612 613 // Remove a definition entirely frmo the context. 614 Context removeDefinition(const NamedDecl *D, Context Ctx) { 615 Context NewCtx = Ctx; 616 if (NewCtx.contains(D)) { 617 NewCtx = ContextFactory.remove(NewCtx, D); 618 } 619 return NewCtx; 620 } 621 622 Context intersectContexts(Context C1, Context C2); 623 Context createReferenceContext(Context C); 624 void intersectBackEdge(Context C1, Context C2); 625 626 friend class VarMapBuilder; 627}; 628 629 630// This has to be defined after LocalVariableMap. 631CFGBlockInfo CFGBlockInfo::getEmptyBlockInfo(Lockset::Factory &F, 632 LocalVariableMap &M) { 633 return CFGBlockInfo(F.getEmptyMap(), M.getEmptyContext()); 634} 635 636 637/// Visitor which builds a LocalVariableMap 638class VarMapBuilder : public StmtVisitor<VarMapBuilder> { 639public: 640 LocalVariableMap* VMap; 641 LocalVariableMap::Context Ctx; 642 643 VarMapBuilder(LocalVariableMap *VM, LocalVariableMap::Context C) 644 : VMap(VM), Ctx(C) {} 645 646 void VisitDeclStmt(DeclStmt *S); 647 void VisitBinaryOperator(BinaryOperator *BO); 648}; 649 650 651// Add new local variables to the variable map 652void VarMapBuilder::VisitDeclStmt(DeclStmt *S) { 653 bool modifiedCtx = false; 654 DeclGroupRef DGrp = S->getDeclGroup(); 655 for (DeclGroupRef::iterator I = DGrp.begin(), E = DGrp.end(); I != E; ++I) { 656 if (VarDecl *VD = dyn_cast_or_null<VarDecl>(*I)) { 657 Expr *E = VD->getInit(); 658 659 // Add local variables with trivial type to the variable map 660 QualType T = VD->getType(); 661 if (T.isTrivialType(VD->getASTContext())) { 662 Ctx = VMap->addDefinition(VD, E, Ctx); 663 modifiedCtx = true; 664 } 665 } 666 } 667 if (modifiedCtx) 668 VMap->saveContext(S, Ctx); 669} 670 671// Update local variable definitions in variable map 672void VarMapBuilder::VisitBinaryOperator(BinaryOperator *BO) { 673 if (!BO->isAssignmentOp()) 674 return; 675 676 Expr *LHSExp = BO->getLHS()->IgnoreParenCasts(); 677 678 // Update the variable map and current context. 679 if (DeclRefExpr *DRE = dyn_cast<DeclRefExpr>(LHSExp)) { 680 ValueDecl *VDec = DRE->getDecl(); 681 if (Ctx.lookup(VDec)) { 682 if (BO->getOpcode() == BO_Assign) 683 Ctx = VMap->updateDefinition(VDec, BO->getRHS(), Ctx); 684 else 685 // FIXME -- handle compound assignment operators 686 Ctx = VMap->clearDefinition(VDec, Ctx); 687 VMap->saveContext(BO, Ctx); 688 } 689 } 690} 691 692 693// Computes the intersection of two contexts. The intersection is the 694// set of variables which have the same definition in both contexts; 695// variables with different definitions are discarded. 696LocalVariableMap::Context 697LocalVariableMap::intersectContexts(Context C1, Context C2) { 698 Context Result = C1; 699 for (Context::iterator I = C1.begin(), E = C1.end(); I != E; ++I) { 700 const NamedDecl *Dec = I.getKey(); 701 unsigned i1 = I.getData(); 702 const unsigned *i2 = C2.lookup(Dec); 703 if (!i2) // variable doesn't exist on second path 704 Result = removeDefinition(Dec, Result); 705 else if (*i2 != i1) // variable exists, but has different definition 706 Result = clearDefinition(Dec, Result); 707 } 708 return Result; 709} 710 711// For every variable in C, create a new variable that refers to the 712// definition in C. Return a new context that contains these new variables. 713// (We use this for a naive implementation of SSA on loop back-edges.) 714LocalVariableMap::Context LocalVariableMap::createReferenceContext(Context C) { 715 Context Result = getEmptyContext(); 716 for (Context::iterator I = C.begin(), E = C.end(); I != E; ++I) { 717 const NamedDecl *Dec = I.getKey(); 718 unsigned i = I.getData(); 719 Result = addReference(Dec, i, Result); 720 } 721 return Result; 722} 723 724// This routine also takes the intersection of C1 and C2, but it does so by 725// altering the VarDefinitions. C1 must be the result of an earlier call to 726// createReferenceContext. 727void LocalVariableMap::intersectBackEdge(Context C1, Context C2) { 728 for (Context::iterator I = C1.begin(), E = C1.end(); I != E; ++I) { 729 const NamedDecl *Dec = I.getKey(); 730 unsigned i1 = I.getData(); 731 VarDefinition *VDef = &VarDefinitions[i1]; 732 assert(VDef->isReference()); 733 734 const unsigned *i2 = C2.lookup(Dec); 735 if (!i2 || (*i2 != i1)) 736 VDef->Ref = 0; // Mark this variable as undefined 737 } 738} 739 740 741// Traverse the CFG in topological order, so all predecessors of a block 742// (excluding back-edges) are visited before the block itself. At 743// each point in the code, we calculate a Context, which holds the set of 744// variable definitions which are visible at that point in execution. 745// Visible variables are mapped to their definitions using an array that 746// contains all definitions. 747// 748// At join points in the CFG, the set is computed as the intersection of 749// the incoming sets along each edge, E.g. 750// 751// { Context | VarDefinitions } 752// int x = 0; { x -> x1 | x1 = 0 } 753// int y = 0; { x -> x1, y -> y1 | y1 = 0, x1 = 0 } 754// if (b) x = 1; { x -> x2, y -> y1 | x2 = 1, y1 = 0, ... } 755// else x = 2; { x -> x3, y -> y1 | x3 = 2, x2 = 1, ... } 756// ... { y -> y1 (x is unknown) | x3 = 2, x2 = 1, ... } 757// 758// This is essentially a simpler and more naive version of the standard SSA 759// algorithm. Those definitions that remain in the intersection are from blocks 760// that strictly dominate the current block. We do not bother to insert proper 761// phi nodes, because they are not used in our analysis; instead, wherever 762// a phi node would be required, we simply remove that definition from the 763// context (E.g. x above). 764// 765// The initial traversal does not capture back-edges, so those need to be 766// handled on a separate pass. Whenever the first pass encounters an 767// incoming back edge, it duplicates the context, creating new definitions 768// that refer back to the originals. (These correspond to places where SSA 769// might have to insert a phi node.) On the second pass, these definitions are 770// set to NULL if the the variable has changed on the back-edge (i.e. a phi 771// node was actually required.) E.g. 772// 773// { Context | VarDefinitions } 774// int x = 0, y = 0; { x -> x1, y -> y1 | y1 = 0, x1 = 0 } 775// while (b) { x -> x2, y -> y1 | [1st:] x2=x1; [2nd:] x2=NULL; } 776// x = x+1; { x -> x3, y -> y1 | x3 = x2 + 1, ... } 777// ... { y -> y1 | x3 = 2, x2 = 1, ... } 778// 779void LocalVariableMap::traverseCFG(CFG *CFGraph, 780 PostOrderCFGView *SortedGraph, 781 std::vector<CFGBlockInfo> &BlockInfo) { 782 PostOrderCFGView::CFGBlockSet VisitedBlocks(CFGraph); 783 784 CtxIndices.resize(CFGraph->getNumBlockIDs()); 785 786 for (PostOrderCFGView::iterator I = SortedGraph->begin(), 787 E = SortedGraph->end(); I!= E; ++I) { 788 const CFGBlock *CurrBlock = *I; 789 int CurrBlockID = CurrBlock->getBlockID(); 790 CFGBlockInfo *CurrBlockInfo = &BlockInfo[CurrBlockID]; 791 792 VisitedBlocks.insert(CurrBlock); 793 794 // Calculate the entry context for the current block 795 bool HasBackEdges = false; 796 bool CtxInit = true; 797 for (CFGBlock::const_pred_iterator PI = CurrBlock->pred_begin(), 798 PE = CurrBlock->pred_end(); PI != PE; ++PI) { 799 // if *PI -> CurrBlock is a back edge, so skip it 800 if (*PI == 0 || !VisitedBlocks.alreadySet(*PI)) { 801 HasBackEdges = true; 802 continue; 803 } 804 805 int PrevBlockID = (*PI)->getBlockID(); 806 CFGBlockInfo *PrevBlockInfo = &BlockInfo[PrevBlockID]; 807 808 if (CtxInit) { 809 CurrBlockInfo->EntryContext = PrevBlockInfo->ExitContext; 810 CtxInit = false; 811 } 812 else { 813 CurrBlockInfo->EntryContext = 814 intersectContexts(CurrBlockInfo->EntryContext, 815 PrevBlockInfo->ExitContext); 816 } 817 } 818 819 // Duplicate the context if we have back-edges, so we can call 820 // intersectBackEdges later. 821 if (HasBackEdges) 822 CurrBlockInfo->EntryContext = 823 createReferenceContext(CurrBlockInfo->EntryContext); 824 825 // Create a starting context index for the current block 826 saveContext(0, CurrBlockInfo->EntryContext); 827 CurrBlockInfo->EntryIndex = getContextIndex(); 828 829 // Visit all the statements in the basic block. 830 VarMapBuilder VMapBuilder(this, CurrBlockInfo->EntryContext); 831 for (CFGBlock::const_iterator BI = CurrBlock->begin(), 832 BE = CurrBlock->end(); BI != BE; ++BI) { 833 switch (BI->getKind()) { 834 case CFGElement::Statement: { 835 const CFGStmt *CS = cast<CFGStmt>(&*BI); 836 VMapBuilder.Visit(const_cast<Stmt*>(CS->getStmt())); 837 break; 838 } 839 default: 840 break; 841 } 842 } 843 CurrBlockInfo->ExitContext = VMapBuilder.Ctx; 844 845 // Mark variables on back edges as "unknown" if they've been changed. 846 for (CFGBlock::const_succ_iterator SI = CurrBlock->succ_begin(), 847 SE = CurrBlock->succ_end(); SI != SE; ++SI) { 848 // if CurrBlock -> *SI is *not* a back edge 849 if (*SI == 0 || !VisitedBlocks.alreadySet(*SI)) 850 continue; 851 852 CFGBlock *FirstLoopBlock = *SI; 853 Context LoopBegin = BlockInfo[FirstLoopBlock->getBlockID()].EntryContext; 854 Context LoopEnd = CurrBlockInfo->ExitContext; 855 intersectBackEdge(LoopBegin, LoopEnd); 856 } 857 } 858 859 // Put an extra entry at the end of the indexed context array 860 unsigned exitID = CFGraph->getExit().getBlockID(); 861 saveContext(0, BlockInfo[exitID].ExitContext); 862} 863 864/// Find the appropriate source locations to use when producing diagnostics for 865/// each block in the CFG. 866static void findBlockLocations(CFG *CFGraph, 867 PostOrderCFGView *SortedGraph, 868 std::vector<CFGBlockInfo> &BlockInfo) { 869 for (PostOrderCFGView::iterator I = SortedGraph->begin(), 870 E = SortedGraph->end(); I!= E; ++I) { 871 const CFGBlock *CurrBlock = *I; 872 CFGBlockInfo *CurrBlockInfo = &BlockInfo[CurrBlock->getBlockID()]; 873 874 // Find the source location of the last statement in the block, if the 875 // block is not empty. 876 if (const Stmt *S = CurrBlock->getTerminator()) { 877 CurrBlockInfo->EntryLoc = CurrBlockInfo->ExitLoc = S->getLocStart(); 878 } else { 879 for (CFGBlock::const_reverse_iterator BI = CurrBlock->rbegin(), 880 BE = CurrBlock->rend(); BI != BE; ++BI) { 881 // FIXME: Handle other CFGElement kinds. 882 if (const CFGStmt *CS = dyn_cast<CFGStmt>(&*BI)) { 883 CurrBlockInfo->ExitLoc = CS->getStmt()->getLocStart(); 884 break; 885 } 886 } 887 } 888 889 if (!CurrBlockInfo->ExitLoc.isInvalid()) { 890 // This block contains at least one statement. Find the source location 891 // of the first statement in the block. 892 for (CFGBlock::const_iterator BI = CurrBlock->begin(), 893 BE = CurrBlock->end(); BI != BE; ++BI) { 894 // FIXME: Handle other CFGElement kinds. 895 if (const CFGStmt *CS = dyn_cast<CFGStmt>(&*BI)) { 896 CurrBlockInfo->EntryLoc = CS->getStmt()->getLocStart(); 897 break; 898 } 899 } 900 } else if (CurrBlock->pred_size() == 1 && *CurrBlock->pred_begin() && 901 CurrBlock != &CFGraph->getExit()) { 902 // The block is empty, and has a single predecessor. Use its exit 903 // location. 904 CurrBlockInfo->EntryLoc = CurrBlockInfo->ExitLoc = 905 BlockInfo[(*CurrBlock->pred_begin())->getBlockID()].ExitLoc; 906 } 907 } 908} 909 910/// \brief Class which implements the core thread safety analysis routines. 911class ThreadSafetyAnalyzer { 912 friend class BuildLockset; 913 914 ThreadSafetyHandler &Handler; 915 Lockset::Factory LocksetFactory; 916 LocalVariableMap LocalVarMap; 917 std::vector<CFGBlockInfo> BlockInfo; 918 919public: 920 ThreadSafetyAnalyzer(ThreadSafetyHandler &H) : Handler(H) {} 921 922 Lockset addLock(const Lockset &LSet, const MutexID &Mutex, 923 const LockData &LDat); 924 Lockset addLock(const Lockset &LSet, Expr *MutexExp, const NamedDecl *D, 925 const LockData &LDat); 926 Lockset removeLock(const Lockset &LSet, const MutexID &Mutex, 927 SourceLocation UnlockLoc); 928 929 template <class AttrType> 930 Lockset addLocksToSet(const Lockset &LSet, LockKind LK, AttrType *Attr, 931 Expr *Exp, NamedDecl *D, VarDecl *VD = 0); 932 Lockset removeLocksFromSet(const Lockset &LSet, 933 UnlockFunctionAttr *Attr, 934 Expr *Exp, NamedDecl* FunDecl); 935 936 template <class AttrType> 937 Lockset addTrylock(const Lockset &LSet, 938 LockKind LK, AttrType *Attr, Expr *Exp, NamedDecl *FunDecl, 939 const CFGBlock* PredBlock, const CFGBlock *CurrBlock, 940 Expr *BrE, bool Neg); 941 const CallExpr* getTrylockCallExpr(const Stmt *Cond, LocalVarContext C, 942 bool &Negate); 943 944 Lockset getEdgeLockset(const Lockset &ExitSet, 945 const CFGBlock* PredBlock, 946 const CFGBlock *CurrBlock); 947 948 Lockset intersectAndWarn(const Lockset &LSet1, const Lockset &LSet2, 949 SourceLocation JoinLoc, LockErrorKind LEK); 950 951 void runAnalysis(AnalysisDeclContext &AC); 952}; 953 954 955/// \brief Add a new lock to the lockset, warning if the lock is already there. 956/// \param Mutex -- the Mutex expression for the lock 957/// \param LDat -- the LockData for the lock 958Lockset ThreadSafetyAnalyzer::addLock(const Lockset &LSet, 959 const MutexID &Mutex, 960 const LockData &LDat) { 961 // FIXME: deal with acquired before/after annotations. 962 // FIXME: Don't always warn when we have support for reentrant locks. 963 if (LSet.lookup(Mutex)) { 964 Handler.handleDoubleLock(Mutex.getName(), LDat.AcquireLoc); 965 return LSet; 966 } else { 967 return LocksetFactory.add(LSet, Mutex, LDat); 968 } 969} 970 971/// \brief Construct a new mutex and add it to the lockset. 972Lockset ThreadSafetyAnalyzer::addLock(const Lockset &LSet, 973 Expr *MutexExp, const NamedDecl *D, 974 const LockData &LDat) { 975 MutexID Mutex(MutexExp, 0, D); 976 if (!Mutex.isValid()) { 977 MutexID::warnInvalidLock(Handler, MutexExp, 0, D); 978 return LSet; 979 } 980 return addLock(LSet, Mutex, LDat); 981} 982 983 984/// \brief Remove a lock from the lockset, warning if the lock is not there. 985/// \param LockExp The lock expression corresponding to the lock to be removed 986/// \param UnlockLoc The source location of the unlock (only used in error msg) 987Lockset ThreadSafetyAnalyzer::removeLock(const Lockset &LSet, 988 const MutexID &Mutex, 989 SourceLocation UnlockLoc) { 990 const LockData *LDat = LSet.lookup(Mutex); 991 if (!LDat) { 992 Handler.handleUnmatchedUnlock(Mutex.getName(), UnlockLoc); 993 return LSet; 994 } 995 else { 996 Lockset Result = LSet; 997 // For scoped-lockable vars, remove the mutex associated with this var. 998 if (LDat->UnderlyingMutex.isValid()) 999 Result = removeLock(Result, LDat->UnderlyingMutex, UnlockLoc); 1000 return LocksetFactory.remove(Result, Mutex); 1001 } 1002} 1003 1004/// \brief This function, parameterized by an attribute type, is used to add a 1005/// set of locks specified as attribute arguments to the lockset. 1006template <typename AttrType> 1007Lockset ThreadSafetyAnalyzer::addLocksToSet(const Lockset &LSet, 1008 LockKind LK, AttrType *Attr, 1009 Expr *Exp, NamedDecl* FunDecl, 1010 VarDecl *VD) { 1011 typedef typename AttrType::args_iterator iterator_type; 1012 1013 SourceLocation ExpLocation = Exp->getExprLoc(); 1014 1015 // Figure out if we're calling the constructor of scoped lockable class 1016 bool isScopedVar = false; 1017 if (VD) { 1018 if (CXXConstructorDecl *CD = dyn_cast<CXXConstructorDecl>(FunDecl)) { 1019 CXXRecordDecl* PD = CD->getParent(); 1020 if (PD && PD->getAttr<ScopedLockableAttr>()) 1021 isScopedVar = true; 1022 } 1023 } 1024 1025 if (Attr->args_size() == 0) { 1026 // The mutex held is the "this" object. 1027 MutexID Mutex(0, Exp, FunDecl); 1028 if (!Mutex.isValid()) { 1029 MutexID::warnInvalidLock(Handler, 0, Exp, FunDecl); 1030 return LSet; 1031 } 1032 else { 1033 return addLock(LSet, Mutex, LockData(ExpLocation, LK)); 1034 } 1035 } 1036 1037 Lockset Result = LSet; 1038 for (iterator_type I=Attr->args_begin(), E=Attr->args_end(); I != E; ++I) { 1039 MutexID Mutex(*I, Exp, FunDecl); 1040 if (!Mutex.isValid()) 1041 MutexID::warnInvalidLock(Handler, *I, Exp, FunDecl); 1042 else { 1043 Result = addLock(Result, Mutex, LockData(ExpLocation, LK)); 1044 if (isScopedVar) { 1045 // For scoped lockable vars, map this var to its underlying mutex. 1046 DeclRefExpr DRE(VD, false, VD->getType(), VK_LValue, VD->getLocation()); 1047 MutexID SMutex(&DRE, 0, 0); 1048 Result = addLock(Result, SMutex, 1049 LockData(VD->getLocation(), LK, Mutex)); 1050 } 1051 } 1052 } 1053 return Result; 1054} 1055 1056/// \brief This function removes a set of locks specified as attribute 1057/// arguments from the lockset. 1058Lockset ThreadSafetyAnalyzer::removeLocksFromSet(const Lockset &LSet, 1059 UnlockFunctionAttr *Attr, 1060 Expr *Exp, NamedDecl* FunDecl) { 1061 SourceLocation ExpLocation; 1062 if (Exp) ExpLocation = Exp->getExprLoc(); 1063 1064 if (Attr->args_size() == 0) { 1065 // The mutex held is the "this" object. 1066 MutexID Mu(0, Exp, FunDecl); 1067 if (!Mu.isValid()) { 1068 MutexID::warnInvalidLock(Handler, 0, Exp, FunDecl); 1069 return LSet; 1070 } else { 1071 return removeLock(LSet, Mu, ExpLocation); 1072 } 1073 } 1074 1075 Lockset Result = LSet; 1076 for (UnlockFunctionAttr::args_iterator I = Attr->args_begin(), 1077 E = Attr->args_end(); I != E; ++I) { 1078 MutexID Mutex(*I, Exp, FunDecl); 1079 if (!Mutex.isValid()) 1080 MutexID::warnInvalidLock(Handler, *I, Exp, FunDecl); 1081 else 1082 Result = removeLock(Result, Mutex, ExpLocation); 1083 } 1084 return Result; 1085} 1086 1087 1088/// \brief Add lock to set, if the current block is in the taken branch of a 1089/// trylock. 1090template <class AttrType> 1091Lockset ThreadSafetyAnalyzer::addTrylock(const Lockset &LSet, 1092 LockKind LK, AttrType *Attr, 1093 Expr *Exp, NamedDecl *FunDecl, 1094 const CFGBlock *PredBlock, 1095 const CFGBlock *CurrBlock, 1096 Expr *BrE, bool Neg) { 1097 // Find out which branch has the lock 1098 bool branch = 0; 1099 if (CXXBoolLiteralExpr *BLE = dyn_cast_or_null<CXXBoolLiteralExpr>(BrE)) { 1100 branch = BLE->getValue(); 1101 } 1102 else if (IntegerLiteral *ILE = dyn_cast_or_null<IntegerLiteral>(BrE)) { 1103 branch = ILE->getValue().getBoolValue(); 1104 } 1105 int branchnum = branch ? 0 : 1; 1106 if (Neg) branchnum = !branchnum; 1107 1108 Lockset Result = LSet; 1109 // If we've taken the trylock branch, then add the lock 1110 int i = 0; 1111 for (CFGBlock::const_succ_iterator SI = PredBlock->succ_begin(), 1112 SE = PredBlock->succ_end(); SI != SE && i < 2; ++SI, ++i) { 1113 if (*SI == CurrBlock && i == branchnum) { 1114 Result = addLocksToSet(Result, LK, Attr, Exp, FunDecl, 0); 1115 } 1116 } 1117 return Result; 1118} 1119 1120 1121// If Cond can be traced back to a function call, return the call expression. 1122// The negate variable should be called with false, and will be set to true 1123// if the function call is negated, e.g. if (!mu.tryLock(...)) 1124const CallExpr* ThreadSafetyAnalyzer::getTrylockCallExpr(const Stmt *Cond, 1125 LocalVarContext C, 1126 bool &Negate) { 1127 if (!Cond) 1128 return 0; 1129 1130 if (const CallExpr *CallExp = dyn_cast<CallExpr>(Cond)) { 1131 return CallExp; 1132 } 1133 else if (const ImplicitCastExpr *CE = dyn_cast<ImplicitCastExpr>(Cond)) { 1134 return getTrylockCallExpr(CE->getSubExpr(), C, Negate); 1135 } 1136 else if (const DeclRefExpr *DRE = dyn_cast<DeclRefExpr>(Cond)) { 1137 const Expr *E = LocalVarMap.lookupExpr(DRE->getDecl(), C); 1138 return getTrylockCallExpr(E, C, Negate); 1139 } 1140 else if (const UnaryOperator *UOP = dyn_cast<UnaryOperator>(Cond)) { 1141 if (UOP->getOpcode() == UO_LNot) { 1142 Negate = !Negate; 1143 return getTrylockCallExpr(UOP->getSubExpr(), C, Negate); 1144 } 1145 } 1146 // FIXME -- handle && and || as well. 1147 return NULL; 1148} 1149 1150 1151/// \brief Find the lockset that holds on the edge between PredBlock 1152/// and CurrBlock. The edge set is the exit set of PredBlock (passed 1153/// as the ExitSet parameter) plus any trylocks, which are conditionally held. 1154Lockset ThreadSafetyAnalyzer::getEdgeLockset(const Lockset &ExitSet, 1155 const CFGBlock *PredBlock, 1156 const CFGBlock *CurrBlock) { 1157 if (!PredBlock->getTerminatorCondition()) 1158 return ExitSet; 1159 1160 bool Negate = false; 1161 const Stmt *Cond = PredBlock->getTerminatorCondition(); 1162 const CFGBlockInfo *PredBlockInfo = &BlockInfo[PredBlock->getBlockID()]; 1163 const LocalVarContext &LVarCtx = PredBlockInfo->ExitContext; 1164 1165 CallExpr *Exp = const_cast<CallExpr*>( 1166 getTrylockCallExpr(Cond, LVarCtx, Negate)); 1167 if (!Exp) 1168 return ExitSet; 1169 1170 NamedDecl *FunDecl = dyn_cast_or_null<NamedDecl>(Exp->getCalleeDecl()); 1171 if(!FunDecl || !FunDecl->hasAttrs()) 1172 return ExitSet; 1173 1174 Lockset Result = ExitSet; 1175 1176 // If the condition is a call to a Trylock function, then grab the attributes 1177 AttrVec &ArgAttrs = FunDecl->getAttrs(); 1178 for (unsigned i = 0; i < ArgAttrs.size(); ++i) { 1179 Attr *Attr = ArgAttrs[i]; 1180 switch (Attr->getKind()) { 1181 case attr::ExclusiveTrylockFunction: { 1182 ExclusiveTrylockFunctionAttr *A = 1183 cast<ExclusiveTrylockFunctionAttr>(Attr); 1184 Result = addTrylock(Result, LK_Exclusive, A, Exp, FunDecl, 1185 PredBlock, CurrBlock, 1186 A->getSuccessValue(), Negate); 1187 break; 1188 } 1189 case attr::SharedTrylockFunction: { 1190 SharedTrylockFunctionAttr *A = 1191 cast<SharedTrylockFunctionAttr>(Attr); 1192 Result = addTrylock(Result, LK_Shared, A, Exp, FunDecl, 1193 PredBlock, CurrBlock, 1194 A->getSuccessValue(), Negate); 1195 break; 1196 } 1197 default: 1198 break; 1199 } 1200 } 1201 return Result; 1202} 1203 1204 1205/// \brief We use this class to visit different types of expressions in 1206/// CFGBlocks, and build up the lockset. 1207/// An expression may cause us to add or remove locks from the lockset, or else 1208/// output error messages related to missing locks. 1209/// FIXME: In future, we may be able to not inherit from a visitor. 1210class BuildLockset : public StmtVisitor<BuildLockset> { 1211 friend class ThreadSafetyAnalyzer; 1212 1213 ThreadSafetyAnalyzer *Analyzer; 1214 Lockset LSet; 1215 LocalVariableMap::Context LVarCtx; 1216 unsigned CtxIndex; 1217 1218 // Helper functions 1219 const ValueDecl *getValueDecl(Expr *Exp); 1220 1221 void warnIfMutexNotHeld(const NamedDecl *D, Expr *Exp, AccessKind AK, 1222 Expr *MutexExp, ProtectedOperationKind POK); 1223 1224 void checkAccess(Expr *Exp, AccessKind AK); 1225 void checkDereference(Expr *Exp, AccessKind AK); 1226 void handleCall(Expr *Exp, NamedDecl *D, VarDecl *VD = 0); 1227 1228 /// \brief Returns true if the lockset contains a lock, regardless of whether 1229 /// the lock is held exclusively or shared. 1230 bool locksetContains(const MutexID &Lock) const { 1231 return LSet.lookup(Lock); 1232 } 1233 1234 /// \brief Returns true if the lockset contains a lock with the passed in 1235 /// locktype. 1236 bool locksetContains(const MutexID &Lock, LockKind KindRequested) const { 1237 const LockData *LockHeld = LSet.lookup(Lock); 1238 return (LockHeld && KindRequested == LockHeld->LKind); 1239 } 1240 1241 /// \brief Returns true if the lockset contains a lock with at least the 1242 /// passed in locktype. So for example, if we pass in LK_Shared, this function 1243 /// returns true if the lock is held LK_Shared or LK_Exclusive. If we pass in 1244 /// LK_Exclusive, this function returns true if the lock is held LK_Exclusive. 1245 bool locksetContainsAtLeast(const MutexID &Lock, 1246 LockKind KindRequested) const { 1247 switch (KindRequested) { 1248 case LK_Shared: 1249 return locksetContains(Lock); 1250 case LK_Exclusive: 1251 return locksetContains(Lock, KindRequested); 1252 } 1253 llvm_unreachable("Unknown LockKind"); 1254 } 1255 1256public: 1257 BuildLockset(ThreadSafetyAnalyzer *Anlzr, CFGBlockInfo &Info) 1258 : StmtVisitor<BuildLockset>(), 1259 Analyzer(Anlzr), 1260 LSet(Info.EntrySet), 1261 LVarCtx(Info.EntryContext), 1262 CtxIndex(Info.EntryIndex) 1263 {} 1264 1265 void VisitUnaryOperator(UnaryOperator *UO); 1266 void VisitBinaryOperator(BinaryOperator *BO); 1267 void VisitCastExpr(CastExpr *CE); 1268 void VisitCallExpr(CallExpr *Exp); 1269 void VisitCXXConstructExpr(CXXConstructExpr *Exp); 1270 void VisitDeclStmt(DeclStmt *S); 1271}; 1272 1273 1274/// \brief Gets the value decl pointer from DeclRefExprs or MemberExprs 1275const ValueDecl *BuildLockset::getValueDecl(Expr *Exp) { 1276 if (const DeclRefExpr *DR = dyn_cast<DeclRefExpr>(Exp)) 1277 return DR->getDecl(); 1278 1279 if (const MemberExpr *ME = dyn_cast<MemberExpr>(Exp)) 1280 return ME->getMemberDecl(); 1281 1282 return 0; 1283} 1284 1285/// \brief Warn if the LSet does not contain a lock sufficient to protect access 1286/// of at least the passed in AccessKind. 1287void BuildLockset::warnIfMutexNotHeld(const NamedDecl *D, Expr *Exp, 1288 AccessKind AK, Expr *MutexExp, 1289 ProtectedOperationKind POK) { 1290 LockKind LK = getLockKindFromAccessKind(AK); 1291 1292 MutexID Mutex(MutexExp, Exp, D); 1293 if (!Mutex.isValid()) 1294 MutexID::warnInvalidLock(Analyzer->Handler, MutexExp, Exp, D); 1295 else if (!locksetContainsAtLeast(Mutex, LK)) 1296 Analyzer->Handler.handleMutexNotHeld(D, POK, Mutex.getName(), LK, 1297 Exp->getExprLoc()); 1298} 1299 1300/// \brief This method identifies variable dereferences and checks pt_guarded_by 1301/// and pt_guarded_var annotations. Note that we only check these annotations 1302/// at the time a pointer is dereferenced. 1303/// FIXME: We need to check for other types of pointer dereferences 1304/// (e.g. [], ->) and deal with them here. 1305/// \param Exp An expression that has been read or written. 1306void BuildLockset::checkDereference(Expr *Exp, AccessKind AK) { 1307 UnaryOperator *UO = dyn_cast<UnaryOperator>(Exp); 1308 if (!UO || UO->getOpcode() != clang::UO_Deref) 1309 return; 1310 Exp = UO->getSubExpr()->IgnoreParenCasts(); 1311 1312 const ValueDecl *D = getValueDecl(Exp); 1313 if(!D || !D->hasAttrs()) 1314 return; 1315 1316 if (D->getAttr<PtGuardedVarAttr>() && LSet.isEmpty()) 1317 Analyzer->Handler.handleNoMutexHeld(D, POK_VarDereference, AK, 1318 Exp->getExprLoc()); 1319 1320 const AttrVec &ArgAttrs = D->getAttrs(); 1321 for(unsigned i = 0, Size = ArgAttrs.size(); i < Size; ++i) 1322 if (PtGuardedByAttr *PGBAttr = dyn_cast<PtGuardedByAttr>(ArgAttrs[i])) 1323 warnIfMutexNotHeld(D, Exp, AK, PGBAttr->getArg(), POK_VarDereference); 1324} 1325 1326/// \brief Checks guarded_by and guarded_var attributes. 1327/// Whenever we identify an access (read or write) of a DeclRefExpr or 1328/// MemberExpr, we need to check whether there are any guarded_by or 1329/// guarded_var attributes, and make sure we hold the appropriate mutexes. 1330void BuildLockset::checkAccess(Expr *Exp, AccessKind AK) { 1331 const ValueDecl *D = getValueDecl(Exp); 1332 if(!D || !D->hasAttrs()) 1333 return; 1334 1335 if (D->getAttr<GuardedVarAttr>() && LSet.isEmpty()) 1336 Analyzer->Handler.handleNoMutexHeld(D, POK_VarAccess, AK, 1337 Exp->getExprLoc()); 1338 1339 const AttrVec &ArgAttrs = D->getAttrs(); 1340 for(unsigned i = 0, Size = ArgAttrs.size(); i < Size; ++i) 1341 if (GuardedByAttr *GBAttr = dyn_cast<GuardedByAttr>(ArgAttrs[i])) 1342 warnIfMutexNotHeld(D, Exp, AK, GBAttr->getArg(), POK_VarAccess); 1343} 1344 1345/// \brief Process a function call, method call, constructor call, 1346/// or destructor call. This involves looking at the attributes on the 1347/// corresponding function/method/constructor/destructor, issuing warnings, 1348/// and updating the locksets accordingly. 1349/// 1350/// FIXME: For classes annotated with one of the guarded annotations, we need 1351/// to treat const method calls as reads and non-const method calls as writes, 1352/// and check that the appropriate locks are held. Non-const method calls with 1353/// the same signature as const method calls can be also treated as reads. 1354/// 1355/// FIXME: We need to also visit CallExprs to catch/check global functions. 1356/// 1357/// FIXME: Do not flag an error for member variables accessed in constructors/ 1358/// destructors 1359void BuildLockset::handleCall(Expr *Exp, NamedDecl *D, VarDecl *VD) { 1360 AttrVec &ArgAttrs = D->getAttrs(); 1361 for(unsigned i = 0; i < ArgAttrs.size(); ++i) { 1362 Attr *Attr = ArgAttrs[i]; 1363 switch (Attr->getKind()) { 1364 // When we encounter an exclusive lock function, we need to add the lock 1365 // to our lockset with kind exclusive. 1366 case attr::ExclusiveLockFunction: { 1367 ExclusiveLockFunctionAttr *A = cast<ExclusiveLockFunctionAttr>(Attr); 1368 LSet = Analyzer->addLocksToSet(LSet, LK_Exclusive, A, Exp, D, VD); 1369 break; 1370 } 1371 1372 // When we encounter a shared lock function, we need to add the lock 1373 // to our lockset with kind shared. 1374 case attr::SharedLockFunction: { 1375 SharedLockFunctionAttr *A = cast<SharedLockFunctionAttr>(Attr); 1376 LSet = Analyzer->addLocksToSet(LSet, LK_Shared, A, Exp, D, VD); 1377 break; 1378 } 1379 1380 // When we encounter an unlock function, we need to remove unlocked 1381 // mutexes from the lockset, and flag a warning if they are not there. 1382 case attr::UnlockFunction: { 1383 UnlockFunctionAttr *UFAttr = cast<UnlockFunctionAttr>(Attr); 1384 LSet = Analyzer->removeLocksFromSet(LSet, UFAttr, Exp, D); 1385 break; 1386 } 1387 1388 case attr::ExclusiveLocksRequired: { 1389 ExclusiveLocksRequiredAttr *ELRAttr = 1390 cast<ExclusiveLocksRequiredAttr>(Attr); 1391 1392 for (ExclusiveLocksRequiredAttr::args_iterator 1393 I = ELRAttr->args_begin(), E = ELRAttr->args_end(); I != E; ++I) 1394 warnIfMutexNotHeld(D, Exp, AK_Written, *I, POK_FunctionCall); 1395 break; 1396 } 1397 1398 case attr::SharedLocksRequired: { 1399 SharedLocksRequiredAttr *SLRAttr = cast<SharedLocksRequiredAttr>(Attr); 1400 1401 for (SharedLocksRequiredAttr::args_iterator I = SLRAttr->args_begin(), 1402 E = SLRAttr->args_end(); I != E; ++I) 1403 warnIfMutexNotHeld(D, Exp, AK_Read, *I, POK_FunctionCall); 1404 break; 1405 } 1406 1407 case attr::LocksExcluded: { 1408 LocksExcludedAttr *LEAttr = cast<LocksExcludedAttr>(Attr); 1409 for (LocksExcludedAttr::args_iterator I = LEAttr->args_begin(), 1410 E = LEAttr->args_end(); I != E; ++I) { 1411 MutexID Mutex(*I, Exp, D); 1412 if (!Mutex.isValid()) 1413 MutexID::warnInvalidLock(Analyzer->Handler, *I, Exp, D); 1414 else if (locksetContains(Mutex)) 1415 Analyzer->Handler.handleFunExcludesLock(D->getName(), 1416 Mutex.getName(), 1417 Exp->getExprLoc()); 1418 } 1419 break; 1420 } 1421 1422 // Ignore other (non thread-safety) attributes 1423 default: 1424 break; 1425 } 1426 } 1427} 1428 1429 1430/// \brief For unary operations which read and write a variable, we need to 1431/// check whether we hold any required mutexes. Reads are checked in 1432/// VisitCastExpr. 1433void BuildLockset::VisitUnaryOperator(UnaryOperator *UO) { 1434 switch (UO->getOpcode()) { 1435 case clang::UO_PostDec: 1436 case clang::UO_PostInc: 1437 case clang::UO_PreDec: 1438 case clang::UO_PreInc: { 1439 Expr *SubExp = UO->getSubExpr()->IgnoreParenCasts(); 1440 checkAccess(SubExp, AK_Written); 1441 checkDereference(SubExp, AK_Written); 1442 break; 1443 } 1444 default: 1445 break; 1446 } 1447} 1448 1449/// For binary operations which assign to a variable (writes), we need to check 1450/// whether we hold any required mutexes. 1451/// FIXME: Deal with non-primitive types. 1452void BuildLockset::VisitBinaryOperator(BinaryOperator *BO) { 1453 if (!BO->isAssignmentOp()) 1454 return; 1455 1456 // adjust the context 1457 LVarCtx = Analyzer->LocalVarMap.getNextContext(CtxIndex, BO, LVarCtx); 1458 1459 Expr *LHSExp = BO->getLHS()->IgnoreParenCasts(); 1460 checkAccess(LHSExp, AK_Written); 1461 checkDereference(LHSExp, AK_Written); 1462} 1463 1464/// Whenever we do an LValue to Rvalue cast, we are reading a variable and 1465/// need to ensure we hold any required mutexes. 1466/// FIXME: Deal with non-primitive types. 1467void BuildLockset::VisitCastExpr(CastExpr *CE) { 1468 if (CE->getCastKind() != CK_LValueToRValue) 1469 return; 1470 Expr *SubExp = CE->getSubExpr()->IgnoreParenCasts(); 1471 checkAccess(SubExp, AK_Read); 1472 checkDereference(SubExp, AK_Read); 1473} 1474 1475 1476void BuildLockset::VisitCallExpr(CallExpr *Exp) { 1477 NamedDecl *D = dyn_cast_or_null<NamedDecl>(Exp->getCalleeDecl()); 1478 if(!D || !D->hasAttrs()) 1479 return; 1480 handleCall(Exp, D); 1481} 1482 1483void BuildLockset::VisitCXXConstructExpr(CXXConstructExpr *Exp) { 1484 // FIXME -- only handles constructors in DeclStmt below. 1485} 1486 1487void BuildLockset::VisitDeclStmt(DeclStmt *S) { 1488 // adjust the context 1489 LVarCtx = Analyzer->LocalVarMap.getNextContext(CtxIndex, S, LVarCtx); 1490 1491 DeclGroupRef DGrp = S->getDeclGroup(); 1492 for (DeclGroupRef::iterator I = DGrp.begin(), E = DGrp.end(); I != E; ++I) { 1493 Decl *D = *I; 1494 if (VarDecl *VD = dyn_cast_or_null<VarDecl>(D)) { 1495 Expr *E = VD->getInit(); 1496 if (CXXConstructExpr *CE = dyn_cast_or_null<CXXConstructExpr>(E)) { 1497 NamedDecl *CtorD = dyn_cast_or_null<NamedDecl>(CE->getConstructor()); 1498 if (!CtorD || !CtorD->hasAttrs()) 1499 return; 1500 handleCall(CE, CtorD, VD); 1501 } 1502 } 1503 } 1504} 1505 1506 1507 1508/// \brief Compute the intersection of two locksets and issue warnings for any 1509/// locks in the symmetric difference. 1510/// 1511/// This function is used at a merge point in the CFG when comparing the lockset 1512/// of each branch being merged. For example, given the following sequence: 1513/// A; if () then B; else C; D; we need to check that the lockset after B and C 1514/// are the same. In the event of a difference, we use the intersection of these 1515/// two locksets at the start of D. 1516/// 1517/// \param LSet1 The first lockset. 1518/// \param LSet2 The second lockset. 1519/// \param JoinLoc The location of the join point for error reporting 1520/// \param LEK The error message to report. 1521Lockset ThreadSafetyAnalyzer::intersectAndWarn(const Lockset &LSet1, 1522 const Lockset &LSet2, 1523 SourceLocation JoinLoc, 1524 LockErrorKind LEK) { 1525 Lockset Intersection = LSet1; 1526 1527 for (Lockset::iterator I = LSet2.begin(), E = LSet2.end(); I != E; ++I) { 1528 const MutexID &LSet2Mutex = I.getKey(); 1529 const LockData &LSet2LockData = I.getData(); 1530 if (const LockData *LD = LSet1.lookup(LSet2Mutex)) { 1531 if (LD->LKind != LSet2LockData.LKind) { 1532 Handler.handleExclusiveAndShared(LSet2Mutex.getName(), 1533 LSet2LockData.AcquireLoc, 1534 LD->AcquireLoc); 1535 if (LD->LKind != LK_Exclusive) 1536 Intersection = LocksetFactory.add(Intersection, LSet2Mutex, 1537 LSet2LockData); 1538 } 1539 } else { 1540 Handler.handleMutexHeldEndOfScope(LSet2Mutex.getName(), 1541 LSet2LockData.AcquireLoc, 1542 JoinLoc, LEK); 1543 } 1544 } 1545 1546 for (Lockset::iterator I = LSet1.begin(), E = LSet1.end(); I != E; ++I) { 1547 if (!LSet2.contains(I.getKey())) { 1548 const MutexID &Mutex = I.getKey(); 1549 const LockData &MissingLock = I.getData(); 1550 Handler.handleMutexHeldEndOfScope(Mutex.getName(), 1551 MissingLock.AcquireLoc, 1552 JoinLoc, LEK); 1553 Intersection = LocksetFactory.remove(Intersection, Mutex); 1554 } 1555 } 1556 return Intersection; 1557} 1558 1559 1560/// \brief Check a function's CFG for thread-safety violations. 1561/// 1562/// We traverse the blocks in the CFG, compute the set of mutexes that are held 1563/// at the end of each block, and issue warnings for thread safety violations. 1564/// Each block in the CFG is traversed exactly once. 1565void ThreadSafetyAnalyzer::runAnalysis(AnalysisDeclContext &AC) { 1566 CFG *CFGraph = AC.getCFG(); 1567 if (!CFGraph) return; 1568 const NamedDecl *D = dyn_cast_or_null<NamedDecl>(AC.getDecl()); 1569 1570 // AC.dumpCFG(true); 1571 1572 if (!D) 1573 return; // Ignore anonymous functions for now. 1574 if (D->getAttr<NoThreadSafetyAnalysisAttr>()) 1575 return; 1576 // FIXME: Do something a bit more intelligent inside constructor and 1577 // destructor code. Constructors and destructors must assume unique access 1578 // to 'this', so checks on member variable access is disabled, but we should 1579 // still enable checks on other objects. 1580 if (isa<CXXConstructorDecl>(D)) 1581 return; // Don't check inside constructors. 1582 if (isa<CXXDestructorDecl>(D)) 1583 return; // Don't check inside destructors. 1584 1585 BlockInfo.resize(CFGraph->getNumBlockIDs(), 1586 CFGBlockInfo::getEmptyBlockInfo(LocksetFactory, LocalVarMap)); 1587 1588 // We need to explore the CFG via a "topological" ordering. 1589 // That way, we will be guaranteed to have information about required 1590 // predecessor locksets when exploring a new block. 1591 PostOrderCFGView *SortedGraph = AC.getAnalysis<PostOrderCFGView>(); 1592 PostOrderCFGView::CFGBlockSet VisitedBlocks(CFGraph); 1593 1594 // Compute SSA names for local variables 1595 LocalVarMap.traverseCFG(CFGraph, SortedGraph, BlockInfo); 1596 1597 // Fill in source locations for all CFGBlocks. 1598 findBlockLocations(CFGraph, SortedGraph, BlockInfo); 1599 1600 // Add locks from exclusive_locks_required and shared_locks_required 1601 // to initial lockset. Also turn off checking for lock and unlock functions. 1602 // FIXME: is there a more intelligent way to check lock/unlock functions? 1603 if (!SortedGraph->empty() && D->hasAttrs()) { 1604 const CFGBlock *FirstBlock = *SortedGraph->begin(); 1605 Lockset &InitialLockset = BlockInfo[FirstBlock->getBlockID()].EntrySet; 1606 const AttrVec &ArgAttrs = D->getAttrs(); 1607 for (unsigned i = 0; i < ArgAttrs.size(); ++i) { 1608 Attr *Attr = ArgAttrs[i]; 1609 SourceLocation AttrLoc = Attr->getLocation(); 1610 if (SharedLocksRequiredAttr *SLRAttr 1611 = dyn_cast<SharedLocksRequiredAttr>(Attr)) { 1612 for (SharedLocksRequiredAttr::args_iterator 1613 SLRIter = SLRAttr->args_begin(), 1614 SLREnd = SLRAttr->args_end(); SLRIter != SLREnd; ++SLRIter) 1615 InitialLockset = addLock(InitialLockset, *SLRIter, D, 1616 LockData(AttrLoc, LK_Shared)); 1617 } else if (ExclusiveLocksRequiredAttr *ELRAttr 1618 = dyn_cast<ExclusiveLocksRequiredAttr>(Attr)) { 1619 for (ExclusiveLocksRequiredAttr::args_iterator 1620 ELRIter = ELRAttr->args_begin(), 1621 ELREnd = ELRAttr->args_end(); ELRIter != ELREnd; ++ELRIter) 1622 InitialLockset = addLock(InitialLockset, *ELRIter, D, 1623 LockData(AttrLoc, LK_Exclusive)); 1624 } else if (isa<UnlockFunctionAttr>(Attr)) { 1625 // Don't try to check unlock functions for now 1626 return; 1627 } else if (isa<ExclusiveLockFunctionAttr>(Attr)) { 1628 // Don't try to check lock functions for now 1629 return; 1630 } else if (isa<SharedLockFunctionAttr>(Attr)) { 1631 // Don't try to check lock functions for now 1632 return; 1633 } 1634 } 1635 } 1636 1637 for (PostOrderCFGView::iterator I = SortedGraph->begin(), 1638 E = SortedGraph->end(); I!= E; ++I) { 1639 const CFGBlock *CurrBlock = *I; 1640 int CurrBlockID = CurrBlock->getBlockID(); 1641 CFGBlockInfo *CurrBlockInfo = &BlockInfo[CurrBlockID]; 1642 1643 // Use the default initial lockset in case there are no predecessors. 1644 VisitedBlocks.insert(CurrBlock); 1645 1646 // Iterate through the predecessor blocks and warn if the lockset for all 1647 // predecessors is not the same. We take the entry lockset of the current 1648 // block to be the intersection of all previous locksets. 1649 // FIXME: By keeping the intersection, we may output more errors in future 1650 // for a lock which is not in the intersection, but was in the union. We 1651 // may want to also keep the union in future. As an example, let's say 1652 // the intersection contains Mutex L, and the union contains L and M. 1653 // Later we unlock M. At this point, we would output an error because we 1654 // never locked M; although the real error is probably that we forgot to 1655 // lock M on all code paths. Conversely, let's say that later we lock M. 1656 // In this case, we should compare against the intersection instead of the 1657 // union because the real error is probably that we forgot to unlock M on 1658 // all code paths. 1659 bool LocksetInitialized = false; 1660 llvm::SmallVector<CFGBlock*, 8> SpecialBlocks; 1661 for (CFGBlock::const_pred_iterator PI = CurrBlock->pred_begin(), 1662 PE = CurrBlock->pred_end(); PI != PE; ++PI) { 1663 1664 // if *PI -> CurrBlock is a back edge 1665 if (*PI == 0 || !VisitedBlocks.alreadySet(*PI)) 1666 continue; 1667 1668 // Ignore edges from blocks that can't return. 1669 if ((*PI)->hasNoReturnElement()) 1670 continue; 1671 1672 // If the previous block ended in a 'continue' or 'break' statement, then 1673 // a difference in locksets is probably due to a bug in that block, rather 1674 // than in some other predecessor. In that case, keep the other 1675 // predecessor's lockset. 1676 if (const Stmt *Terminator = (*PI)->getTerminator()) { 1677 if (isa<ContinueStmt>(Terminator) || isa<BreakStmt>(Terminator)) { 1678 SpecialBlocks.push_back(*PI); 1679 continue; 1680 } 1681 } 1682 1683 int PrevBlockID = (*PI)->getBlockID(); 1684 CFGBlockInfo *PrevBlockInfo = &BlockInfo[PrevBlockID]; 1685 Lockset PrevLockset = 1686 getEdgeLockset(PrevBlockInfo->ExitSet, *PI, CurrBlock); 1687 1688 if (!LocksetInitialized) { 1689 CurrBlockInfo->EntrySet = PrevLockset; 1690 LocksetInitialized = true; 1691 } else { 1692 CurrBlockInfo->EntrySet = 1693 intersectAndWarn(CurrBlockInfo->EntrySet, PrevLockset, 1694 CurrBlockInfo->EntryLoc, 1695 LEK_LockedSomePredecessors); 1696 } 1697 } 1698 1699 // Process continue and break blocks. Assume that the lockset for the 1700 // resulting block is unaffected by any discrepancies in them. 1701 for (unsigned SpecialI = 0, SpecialN = SpecialBlocks.size(); 1702 SpecialI < SpecialN; ++SpecialI) { 1703 CFGBlock *PrevBlock = SpecialBlocks[SpecialI]; 1704 int PrevBlockID = PrevBlock->getBlockID(); 1705 CFGBlockInfo *PrevBlockInfo = &BlockInfo[PrevBlockID]; 1706 1707 if (!LocksetInitialized) { 1708 CurrBlockInfo->EntrySet = PrevBlockInfo->ExitSet; 1709 LocksetInitialized = true; 1710 } else { 1711 // Determine whether this edge is a loop terminator for diagnostic 1712 // purposes. FIXME: A 'break' statement might be a loop terminator, but 1713 // it might also be part of a switch. Also, a subsequent destructor 1714 // might add to the lockset, in which case the real issue might be a 1715 // double lock on the other path. 1716 const Stmt *Terminator = PrevBlock->getTerminator(); 1717 bool IsLoop = Terminator && isa<ContinueStmt>(Terminator); 1718 1719 Lockset PrevLockset = 1720 getEdgeLockset(PrevBlockInfo->ExitSet, PrevBlock, CurrBlock); 1721 1722 // Do not update EntrySet. 1723 intersectAndWarn(CurrBlockInfo->EntrySet, PrevLockset, 1724 PrevBlockInfo->ExitLoc, 1725 IsLoop ? LEK_LockedSomeLoopIterations 1726 : LEK_LockedSomePredecessors); 1727 } 1728 } 1729 1730 BuildLockset LocksetBuilder(this, *CurrBlockInfo); 1731 1732 // Visit all the statements in the basic block. 1733 for (CFGBlock::const_iterator BI = CurrBlock->begin(), 1734 BE = CurrBlock->end(); BI != BE; ++BI) { 1735 switch (BI->getKind()) { 1736 case CFGElement::Statement: { 1737 const CFGStmt *CS = cast<CFGStmt>(&*BI); 1738 LocksetBuilder.Visit(const_cast<Stmt*>(CS->getStmt())); 1739 break; 1740 } 1741 // Ignore BaseDtor, MemberDtor, and TemporaryDtor for now. 1742 case CFGElement::AutomaticObjectDtor: { 1743 const CFGAutomaticObjDtor *AD = cast<CFGAutomaticObjDtor>(&*BI); 1744 CXXDestructorDecl *DD = const_cast<CXXDestructorDecl*>( 1745 AD->getDestructorDecl(AC.getASTContext())); 1746 if (!DD->hasAttrs()) 1747 break; 1748 1749 // Create a dummy expression, 1750 VarDecl *VD = const_cast<VarDecl*>(AD->getVarDecl()); 1751 DeclRefExpr DRE(VD, false, VD->getType(), VK_LValue, 1752 AD->getTriggerStmt()->getLocEnd()); 1753 LocksetBuilder.handleCall(&DRE, DD); 1754 break; 1755 } 1756 default: 1757 break; 1758 } 1759 } 1760 CurrBlockInfo->ExitSet = LocksetBuilder.LSet; 1761 1762 // For every back edge from CurrBlock (the end of the loop) to another block 1763 // (FirstLoopBlock) we need to check that the Lockset of Block is equal to 1764 // the one held at the beginning of FirstLoopBlock. We can look up the 1765 // Lockset held at the beginning of FirstLoopBlock in the EntryLockSets map. 1766 for (CFGBlock::const_succ_iterator SI = CurrBlock->succ_begin(), 1767 SE = CurrBlock->succ_end(); SI != SE; ++SI) { 1768 1769 // if CurrBlock -> *SI is *not* a back edge 1770 if (*SI == 0 || !VisitedBlocks.alreadySet(*SI)) 1771 continue; 1772 1773 CFGBlock *FirstLoopBlock = *SI; 1774 CFGBlockInfo *PreLoop = &BlockInfo[FirstLoopBlock->getBlockID()]; 1775 CFGBlockInfo *LoopEnd = &BlockInfo[CurrBlockID]; 1776 intersectAndWarn(LoopEnd->ExitSet, PreLoop->EntrySet, 1777 PreLoop->EntryLoc, 1778 LEK_LockedSomeLoopIterations); 1779 } 1780 } 1781 1782 CFGBlockInfo *Initial = &BlockInfo[CFGraph->getEntry().getBlockID()]; 1783 CFGBlockInfo *Final = &BlockInfo[CFGraph->getExit().getBlockID()]; 1784 1785 // FIXME: Should we call this function for all blocks which exit the function? 1786 intersectAndWarn(Initial->EntrySet, Final->ExitSet, 1787 Final->ExitLoc, 1788 LEK_LockedAtEndOfFunction); 1789} 1790 1791} // end anonymous namespace 1792 1793 1794namespace clang { 1795namespace thread_safety { 1796 1797/// \brief Check a function's CFG for thread-safety violations. 1798/// 1799/// We traverse the blocks in the CFG, compute the set of mutexes that are held 1800/// at the end of each block, and issue warnings for thread safety violations. 1801/// Each block in the CFG is traversed exactly once. 1802void runThreadSafetyAnalysis(AnalysisDeclContext &AC, 1803 ThreadSafetyHandler &Handler) { 1804 ThreadSafetyAnalyzer Analyzer(Handler); 1805 Analyzer.runAnalysis(AC); 1806} 1807 1808/// \brief Helper function that returns a LockKind required for the given level 1809/// of access. 1810LockKind getLockKindFromAccessKind(AccessKind AK) { 1811 switch (AK) { 1812 case AK_Read : 1813 return LK_Shared; 1814 case AK_Written : 1815 return LK_Exclusive; 1816 } 1817 llvm_unreachable("Unknown AccessKind"); 1818} 1819 1820}} // end namespace clang::thread_safety 1821