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