lib/StaticAnalyzer/GRState.cpp

   1 //= GRState.cpp - Path-Sensitive "State" for tracking values -----*- 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 //  This file implements GRState and GRStateManager.
  11 //
  12 //===----------------------------------------------------------------------===//
  13
  14 #include "clang/Analysis/CFG.h"
  15 #include "clang/StaticAnalyzer/PathSensitive/GRStateTrait.h"
  16 #include "clang/StaticAnalyzer/PathSensitive/GRState.h"
  17 #include "clang/StaticAnalyzer/PathSensitive/SubEngine.h"
  18 #include "clang/StaticAnalyzer/PathSensitive/TransferFuncs.h"
  19 #include "llvm/Support/raw_ostream.h"
  20
  21 using namespace clang;
  22 using namespace ento;
  23
  24 // Give the vtable for ConstraintManager somewhere to live.
  25 // FIXME: Move this elsewhere.
  26 ConstraintManager::~ConstraintManager() {}
  27
  28 GRStateManager::~GRStateManager() {
  29   for (std::vector<GRState::Printer*>::iterator I=Printers.begin(),
  30         E=Printers.end(); I!=E; ++I)
  31     delete *I;
  32
  33   for (GDMContextsTy::iterator I=GDMContexts.begin(), E=GDMContexts.end();
  34        I!=E; ++I)
  35     I->second.second(I->second.first);
  36 }
  37
  38 const GRState*
  39 GRStateManager::removeDeadBindings(const GRState* state,
  40                                    const StackFrameContext *LCtx,
  41                                    SymbolReaper& SymReaper) {
  42
  43   // This code essentially performs a "mark-and-sweep" of the VariableBindings.
  44   // The roots are any Block-level exprs and Decls that our liveness algorithm
  45   // tells us are live.  We then see what Decls they may reference, and keep
  46   // those around.  This code more than likely can be made faster, and the
  47   // frequency of which this method is called should be experimented with
  48   // for optimum performance.
  49   llvm::SmallVector<const MemRegion*, 10> RegionRoots;
  50   GRState NewState = *state;
  51
  52   NewState.Env = EnvMgr.removeDeadBindings(NewState.Env, SymReaper,
  53                                            state, RegionRoots);
  54
  55   // Clean up the store.
  56   NewState.St = StoreMgr->removeDeadBindings(NewState.St, LCtx,
  57                                              SymReaper, RegionRoots);
  58   state = getPersistentState(NewState);
  59   return ConstraintMgr->removeDeadBindings(state, SymReaper);
  60 }
  61
  62 const GRState *GRStateManager::MarshalState(const GRState *state,
  63                                             const StackFrameContext *InitLoc) {
  64   // make up an empty state for now.
  65   GRState State(this,
  66                 EnvMgr.getInitialEnvironment(),
  67                 StoreMgr->getInitialStore(InitLoc),
  68                 GDMFactory.getEmptyMap());
  69
  70   return getPersistentState(State);
  71 }
  72
  73 const GRState *GRState::bindCompoundLiteral(const CompoundLiteralExpr* CL,
  74                                             const LocationContext *LC,
  75                                             SVal V) const {
  76   Store new_store =
  77     getStateManager().StoreMgr->BindCompoundLiteral(St, CL, LC, V);
  78   return makeWithStore(new_store);
  79 }
  80
  81 const GRState *GRState::bindDecl(const VarRegion* VR, SVal IVal) const {
  82   Store new_store = getStateManager().StoreMgr->BindDecl(St, VR, IVal);
  83   return makeWithStore(new_store);
  84 }
  85
  86 const GRState *GRState::bindDeclWithNoInit(const VarRegion* VR) const {
  87   Store new_store = getStateManager().StoreMgr->BindDeclWithNoInit(St, VR);
  88   return makeWithStore(new_store);
  89 }
  90
  91 const GRState *GRState::bindLoc(Loc LV, SVal V) const {
  92   GRStateManager &Mgr = getStateManager();
  93   Store new_store = Mgr.StoreMgr->Bind(St, LV, V);
  94   const GRState *new_state = makeWithStore(new_store);
  95
  96   const MemRegion *MR = LV.getAsRegion();
  97   if (MR)
  98     return Mgr.getOwningEngine().processRegionChange(new_state, MR);
  99
 100   return new_state;
 101 }
 102
 103 const GRState *GRState::bindDefault(SVal loc, SVal V) const {
 104   GRStateManager &Mgr = getStateManager();
 105   const MemRegion *R = cast<loc::MemRegionVal>(loc).getRegion();
 106   Store new_store = Mgr.StoreMgr->BindDefault(St, R, V);
 107   const GRState *new_state = makeWithStore(new_store);
 108   return Mgr.getOwningEngine().processRegionChange(new_state, R);
 109 }
 110
 111 const GRState *GRState::InvalidateRegions(const MemRegion * const *Begin,
 112                                           const MemRegion * const *End,
 113                                           const Expr *E, unsigned Count,
 114                                           StoreManager::InvalidatedSymbols *IS,
 115                                           bool invalidateGlobals) const {
 116   GRStateManager &Mgr = getStateManager();
 117   SubEngine &Eng = Mgr.getOwningEngine();
 118
 119   if (Eng.wantsRegionChangeUpdate(this)) {
 120     StoreManager::InvalidatedRegions Regions;
 121
 122     Store new_store = Mgr.StoreMgr->InvalidateRegions(St, Begin, End,
 123                                                       E, Count, IS,
 124                                                       invalidateGlobals,
 125                                                       &Regions);
 126     const GRState *new_state = makeWithStore(new_store);
 127
 128     return Eng.processRegionChanges(new_state,
 129                                     &Regions.front(),
 130                                     &Regions.back()+1);
 131   }
 132
 133   Store new_store = Mgr.StoreMgr->InvalidateRegions(St, Begin, End,
 134                                                     E, Count, IS,
 135                                                     invalidateGlobals,
 136                                                     NULL);
 137   return makeWithStore(new_store);
 138 }
 139
 140 const GRState *GRState::unbindLoc(Loc LV) const {
 141   assert(!isa<loc::MemRegionVal>(LV) && "Use InvalidateRegion instead.");
 142
 143   Store OldStore = getStore();
 144   Store NewStore = getStateManager().StoreMgr->Remove(OldStore, LV);
 145
 146   if (NewStore == OldStore)
 147     return this;
 148
 149   return makeWithStore(NewStore);
 150 }
 151
 152 const GRState *GRState::enterStackFrame(const StackFrameContext *frame) const {
 153   Store new_store = getStateManager().StoreMgr->enterStackFrame(this, frame);
 154   return makeWithStore(new_store);
 155 }
 156
 157 SVal GRState::getSValAsScalarOrLoc(const MemRegion *R) const {
 158   // We only want to do fetches from regions that we can actually bind
 159   // values.  For example, SymbolicRegions of type 'id<...>' cannot
 160   // have direct bindings (but their can be bindings on their subregions).
 161   if (!R->isBoundable())
 162     return UnknownVal();
 163
 164   if (const TypedRegion *TR = dyn_cast<TypedRegion>(R)) {
 165     QualType T = TR->getValueType();
 166     if (Loc::IsLocType(T) || T->isIntegerType())
 167       return getSVal(R);
 168   }
 169
 170   return UnknownVal();
 171 }
 172
 173 SVal GRState::getSVal(Loc location, QualType T) const {
 174   SVal V = getRawSVal(cast<Loc>(location), T);
 175
 176   // If 'V' is a symbolic value that is *perfectly* constrained to
 177   // be a constant value, use that value instead to lessen the burden
 178   // on later analysis stages (so we have less symbolic values to reason
 179   // about).
 180   if (!T.isNull()) {
 181     if (SymbolRef sym = V.getAsSymbol()) {
 182       if (const llvm::APSInt *Int = getSymVal(sym)) {
 183         // FIXME: Because we don't correctly model (yet) sign-extension
 184         // and truncation of symbolic values, we need to convert
 185         // the integer value to the correct signedness and bitwidth.
 186         //
 187         // This shows up in the following:
 188         //
 189         //   char foo();
 190         //   unsigned x = foo();
 191         //   if (x == 54)
 192         //     ...
 193         //
 194         //  The symbolic value stored to 'x' is actually the conjured
 195         //  symbol for the call to foo(); the type of that symbol is 'char',
 196         //  not unsigned.
 197         const llvm::APSInt &NewV = getBasicVals().Convert(T, *Int);
 198
 199         if (isa<Loc>(V))
 200           return loc::ConcreteInt(NewV);
 201         else
 202           return nonloc::ConcreteInt(NewV);
 203       }
 204     }
 205   }
 206
 207   return V;
 208 }
 209
 210 const GRState *GRState::BindExpr(const Stmt* S, SVal V, bool Invalidate) const{
 211   Environment NewEnv = getStateManager().EnvMgr.bindExpr(Env, S, V,
 212                                                          Invalidate);
 213   if (NewEnv == Env)
 214     return this;
 215
 216   GRState NewSt = *this;
 217   NewSt.Env = NewEnv;
 218   return getStateManager().getPersistentState(NewSt);
 219 }
 220
 221 const GRState *GRState::bindExprAndLocation(const Stmt *S, SVal location,
 222                                             SVal V) const {
 223   Environment NewEnv =
 224     getStateManager().EnvMgr.bindExprAndLocation(Env, S, location, V);
 225
 226   if (NewEnv == Env)
 227     return this;
 228
 229   GRState NewSt = *this;
 230   NewSt.Env = NewEnv;
 231   return getStateManager().getPersistentState(NewSt);
 232 }
 233
 234 const GRState *GRState::assumeInBound(DefinedOrUnknownSVal Idx,
 235                                       DefinedOrUnknownSVal UpperBound,
 236                                       bool Assumption) const {
 237   if (Idx.isUnknown() || UpperBound.isUnknown())
 238     return this;
 239
 240   // Build an expression for 0 <= Idx < UpperBound.
 241   // This is the same as Idx + MIN < UpperBound + MIN, if overflow is allowed.
 242   // FIXME: This should probably be part of SValBuilder.
 243   GRStateManager &SM = getStateManager();
 244   SValBuilder &svalBuilder = SM.getSValBuilder();
 245   ASTContext &Ctx = svalBuilder.getContext();
 246
 247   // Get the offset: the minimum value of the array index type.
 248   BasicValueFactory &BVF = svalBuilder.getBasicValueFactory();
 249   // FIXME: This should be using ValueManager::ArrayindexTy...somehow.
 250   QualType indexTy = Ctx.IntTy;
 251   nonloc::ConcreteInt Min(BVF.getMinValue(indexTy));
 252
 253   // Adjust the index.
 254   SVal newIdx = svalBuilder.evalBinOpNN(this, BO_Add,
 255                                         cast<NonLoc>(Idx), Min, indexTy);
 256   if (newIdx.isUnknownOrUndef())
 257     return this;
 258
 259   // Adjust the upper bound.
 260   SVal newBound =
 261     svalBuilder.evalBinOpNN(this, BO_Add, cast<NonLoc>(UpperBound),
 262                             Min, indexTy);
 263
 264   if (newBound.isUnknownOrUndef())
 265     return this;
 266
 267   // Build the actual comparison.
 268   SVal inBound = svalBuilder.evalBinOpNN(this, BO_LT,
 269                                 cast<NonLoc>(newIdx), cast<NonLoc>(newBound),
 270                                 Ctx.IntTy);
 271   if (inBound.isUnknownOrUndef())
 272     return this;
 273
 274   // Finally, let the constraint manager take care of it.
 275   ConstraintManager &CM = SM.getConstraintManager();
 276   return CM.assume(this, cast<DefinedSVal>(inBound), Assumption);
 277 }
 278
 279 const GRState* GRStateManager::getInitialState(const LocationContext *InitLoc) {
 280   GRState State(this,
 281                 EnvMgr.getInitialEnvironment(),
 282                 StoreMgr->getInitialStore(InitLoc),
 283                 GDMFactory.getEmptyMap());
 284
 285   return getPersistentState(State);
 286 }
 287
 288 void GRStateManager::recycleUnusedStates() {
 289   for (std::vector<GRState*>::iterator i = recentlyAllocatedStates.begin(),
 290        e = recentlyAllocatedStates.end(); i != e; ++i) {
 291     GRState *state = *i;
 292     if (state->referencedByExplodedNode())
 293       continue;
 294     StateSet.RemoveNode(state);
 295     freeStates.push_back(state);
 296   }
 297   recentlyAllocatedStates.clear();
 298 }
 299
 300 const GRState* GRStateManager::getPersistentState(GRState& State) {
 301
 302   llvm::FoldingSetNodeID ID;
 303   State.Profile(ID);
 304   void* InsertPos;
 305
 306   if (GRState* I = StateSet.FindNodeOrInsertPos(ID, InsertPos))
 307     return I;
 308
 309   GRState *newState = 0;
 310   if (!freeStates.empty()) {
 311     newState = freeStates.back();
 312     freeStates.pop_back();
 313   }
 314   else {
 315     newState = (GRState*) Alloc.Allocate<GRState>();
 316   }
 317   new (newState) GRState(State);
 318   StateSet.InsertNode(newState, InsertPos);
 319   recentlyAllocatedStates.push_back(newState);
 320   return newState;
 321 }
 322
 323 const GRState* GRState::makeWithStore(Store store) const {
 324   GRState NewSt = *this;
 325   NewSt.St = store;
 326   return getStateManager().getPersistentState(NewSt);
 327 }
 328
 329 //===----------------------------------------------------------------------===//
 330 //  State pretty-printing.
 331 //===----------------------------------------------------------------------===//
 332
 333 static bool IsEnvLoc(const Stmt *S) {
 334   // FIXME: This is a layering violation.  Should be in environment.
 335   return (bool) (((uintptr_t) S) & 0x1);
 336 }
 337
 338 void GRState::print(llvm::raw_ostream& Out, CFG &C, const char* nl,
 339                     const char* sep) const {
 340   // Print the store.
 341   GRStateManager &Mgr = getStateManager();
 342   Mgr.getStoreManager().print(getStore(), Out, nl, sep);
 343
 344   // Print Subexpression bindings.
 345   bool isFirst = true;
 346
 347   // FIXME: All environment printing should be moved inside Environment.
 348   for (Environment::iterator I = Env.begin(), E = Env.end(); I != E; ++I) {
 349     if (C.isBlkExpr(I.getKey()) || IsEnvLoc(I.getKey()))
 350       continue;
 351
 352     if (isFirst) {
 353       Out << nl << nl << "Sub-Expressions:" << nl;
 354       isFirst = false;
 355     }
 356     else { Out << nl; }
 357
 358     Out << " (" << (void*) I.getKey() << ") ";
 359     LangOptions LO; // FIXME.
 360     I.getKey()->printPretty(Out, 0, PrintingPolicy(LO));
 361     Out << " : " << I.getData();
 362   }
 363
 364   // Print block-expression bindings.
 365   isFirst = true;
 366
 367   for (Environment::iterator I = Env.begin(), E = Env.end(); I != E; ++I) {
 368     if (!C.isBlkExpr(I.getKey()))
 369       continue;
 370
 371     if (isFirst) {
 372       Out << nl << nl << "Block-level Expressions:" << nl;
 373       isFirst = false;
 374     }
 375     else { Out << nl; }
 376
 377     Out << " (" << (void*) I.getKey() << ") ";
 378     LangOptions LO; // FIXME.
 379     I.getKey()->printPretty(Out, 0, PrintingPolicy(LO));
 380     Out << " : " << I.getData();
 381   }
 382
 383   // Print locations.
 384   isFirst = true;
 385
 386   for (Environment::iterator I = Env.begin(), E = Env.end(); I != E; ++I) {
 387     if (!IsEnvLoc(I.getKey()))
 388       continue;
 389
 390     if (isFirst) {
 391       Out << nl << nl << "Load/store locations:" << nl;
 392       isFirst = false;
 393     }
 394     else { Out << nl; }
 395
 396     const Stmt *S = (Stmt*) (((uintptr_t) I.getKey()) & ((uintptr_t) ~0x1));
 397
 398     Out << " (" << (void*) S << ") ";
 399     LangOptions LO; // FIXME.
 400     S->printPretty(Out, 0, PrintingPolicy(LO));
 401     Out << " : " << I.getData();
 402   }
 403
 404   Mgr.getConstraintManager().print(this, Out, nl, sep);
 405
 406   // Print checker-specific data.
 407   for (std::vector<Printer*>::iterator I = Mgr.Printers.begin(),
 408                                        E = Mgr.Printers.end(); I != E; ++I) {
 409     (*I)->Print(Out, this, nl, sep);
 410   }
 411 }
 412
 413 void GRState::printDOT(llvm::raw_ostream& Out, CFG &C) const {
 414   print(Out, C, "\\l", "\\|");
 415 }
 416
 417 void GRState::printStdErr(CFG &C) const {
 418   print(llvm::errs(), C);
 419 }
 420
 421 //===----------------------------------------------------------------------===//
 422 // Generic Data Map.
 423 //===----------------------------------------------------------------------===//
 424
 425 void* const* GRState::FindGDM(void* K) const {
 426   return GDM.lookup(K);
 427 }
 428
 429 void*
 430 GRStateManager::FindGDMContext(void* K,
 431                                void* (*CreateContext)(llvm::BumpPtrAllocator&),
 432                                void (*DeleteContext)(void*)) {
 433
 434   std::pair<void*, void (*)(void*)>& p = GDMContexts[K];
 435   if (!p.first) {
 436     p.first = CreateContext(Alloc);
 437     p.second = DeleteContext;
 438   }
 439
 440   return p.first;
 441 }
 442
 443 const GRState* GRStateManager::addGDM(const GRState* St, void* Key, void* Data){
 444   GRState::GenericDataMap M1 = St->getGDM();
 445   GRState::GenericDataMap M2 = GDMFactory.add(M1, Key, Data);
 446
 447   if (M1 == M2)
 448     return St;
 449
 450   GRState NewSt = *St;
 451   NewSt.GDM = M2;
 452   return getPersistentState(NewSt);
 453 }
 454
 455 const GRState *GRStateManager::removeGDM(const GRState *state, void *Key) {
 456   GRState::GenericDataMap OldM = state->getGDM();
 457   GRState::GenericDataMap NewM = GDMFactory.remove(OldM, Key);
 458
 459   if (NewM == OldM)
 460     return state;
 461
 462   GRState NewState = *state;
 463   NewState.GDM = NewM;
 464   return getPersistentState(NewState);
 465 }
 466
 467 //===----------------------------------------------------------------------===//
 468 // Utility.
 469 //===----------------------------------------------------------------------===//
 470
 471 namespace {
 472 class ScanReachableSymbols : public SubRegionMap::Visitor  {
 473   typedef llvm::DenseSet<const MemRegion*> VisitedRegionsTy;
 474
 475   VisitedRegionsTy visited;
 476   const GRState *state;
 477   SymbolVisitor &visitor;
 478   llvm::OwningPtr<SubRegionMap> SRM;
 479 public:
 480
 481   ScanReachableSymbols(const GRState *st, SymbolVisitor& v)
 482     : state(st), visitor(v) {}
 483
 484   bool scan(nonloc::CompoundVal val);
 485   bool scan(SVal val);
 486   bool scan(const MemRegion *R);
 487
 488   // From SubRegionMap::Visitor.
 489   bool Visit(const MemRegion* Parent, const MemRegion* SubRegion) {
 490     return scan(SubRegion);
 491   }
 492 };
 493 }
 494
 495 bool ScanReachableSymbols::scan(nonloc::CompoundVal val) {
 496   for (nonloc::CompoundVal::iterator I=val.begin(), E=val.end(); I!=E; ++I)
 497     if (!scan(*I))
 498       return false;
 499
 500   return true;
 501 }
 502
 503 bool ScanReachableSymbols::scan(SVal val) {
 504   if (loc::MemRegionVal *X = dyn_cast<loc::MemRegionVal>(&val))
 505     return scan(X->getRegion());
 506
 507   if (nonloc::LocAsInteger *X = dyn_cast<nonloc::LocAsInteger>(&val))
 508     return scan(X->getLoc());
 509
 510   if (SymbolRef Sym = val.getAsSymbol())
 511     return visitor.VisitSymbol(Sym);
 512
 513   if (nonloc::CompoundVal *X = dyn_cast<nonloc::CompoundVal>(&val))
 514     return scan(*X);
 515
 516   return true;
 517 }
 518
 519 bool ScanReachableSymbols::scan(const MemRegion *R) {
 520   if (isa<MemSpaceRegion>(R) || visited.count(R))
 521     return true;
 522
 523   visited.insert(R);
 524
 525   // If this is a symbolic region, visit the symbol for the region.
 526   if (const SymbolicRegion *SR = dyn_cast<SymbolicRegion>(R))
 527     if (!visitor.VisitSymbol(SR->getSymbol()))
 528       return false;
 529
 530   // If this is a subregion, also visit the parent regions.
 531   if (const SubRegion *SR = dyn_cast<SubRegion>(R))
 532     if (!scan(SR->getSuperRegion()))
 533       return false;
 534
 535   // Now look at the binding to this region (if any).
 536   if (!scan(state->getSValAsScalarOrLoc(R)))
 537     return false;
 538
 539   // Now look at the subregions.
 540   if (!SRM.get())
 541     SRM.reset(state->getStateManager().getStoreManager().
 542                                            getSubRegionMap(state->getStore()));
 543
 544   return SRM->iterSubRegions(R, *this);
 545 }
 546
 547 bool GRState::scanReachableSymbols(SVal val, SymbolVisitor& visitor) const {
 548   ScanReachableSymbols S(this, visitor);
 549   return S.scan(val);
 550 }
 551
 552 bool GRState::scanReachableSymbols(const SVal *I, const SVal *E,
 553                                    SymbolVisitor &visitor) const {
 554   ScanReachableSymbols S(this, visitor);
 555   for ( ; I != E; ++I) {
 556     if (!S.scan(*I))
 557       return false;
 558   }
 559   return true;
 560 }
 561
 562 bool GRState::scanReachableSymbols(const MemRegion * const *I,
 563                                    const MemRegion * const *E,
 564                                    SymbolVisitor &visitor) const {
 565   ScanReachableSymbols S(this, visitor);
 566   for ( ; I != E; ++I) {
 567     if (!S.scan(*I))
 568       return false;
 569   }
 570   return true;
 571 }