ProgramState.cpp

Go to the documentation of this file.

//= ProgramState.cpp - Path-Sensitive "State" for tracking values --*- C++ -*--=
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
//  This file implements ProgramState and ProgramStateManager.
//
//===----------------------------------------------------------------------===//
 
#include "clang/StaticAnalyzer/Core/PathSensitive/ProgramState.h"
#include "clang/Analysis/CFG.h"
#include "clang/Basic/JsonSupport.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/AnalysisManager.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/CallEvent.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/DynamicType.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/ExprEngine.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/ProgramStateTrait.h"
#include "llvm/Support/raw_ostream.h"
#include <optional>
 
using namespace clang;
using namespace ento;
 
namespace clang { namespace  ento {
/// Increments the number of times this state is referenced.
 
void ProgramStateRetain(const ProgramState *state) {
  ++const_cast<ProgramState*>(state)->refCount;
}
 
/// Decrement the number of times this state is referenced.
void ProgramStateRelease(const ProgramState *state) {
  assert(state->refCount > 0);
  ProgramState *s = const_cast<ProgramState*>(state);
  if (--s->refCount == 0) {
    ProgramStateManager &Mgr = s->getStateManager();
    Mgr.StateSet.RemoveNode(s);
    s->~ProgramState();
    Mgr.freeStates.push_back(s);
  }
}
}}
 
ProgramState::ProgramState(ProgramStateManager *mgr, const Environment& env,
                 StoreRef st, GenericDataMap gdm)
  : stateMgr(mgr),
    Env(env),
    store(st.getStore()),
    GDM(gdm),
    refCount(0) {
  stateMgr->getStoreManager().incrementReferenceCount(store);
}
 
ProgramState::ProgramState(const ProgramState &RHS)
    : stateMgr(RHS.stateMgr), Env(RHS.Env), store(RHS.store), GDM(RHS.GDM),
      PosteriorlyOverconstrained(RHS.PosteriorlyOverconstrained), refCount(0) {
  stateMgr->getStoreManager().incrementReferenceCount(store);
}
 
ProgramState::~ProgramState() {
  if (store)
    stateMgr->getStoreManager().decrementReferenceCount(store);
}
 
int64_t ProgramState::getID() const {
  return getStateManager().Alloc.identifyKnownAlignedObject<ProgramState>(this);
}
 
ProgramStateManager::ProgramStateManager(ASTContext &Ctx,
                                         StoreManagerCreator CreateSMgr,
                                         ConstraintManagerCreator CreateCMgr,
                                         llvm::BumpPtrAllocator &alloc,
                                         ExprEngine *ExprEng)
  : Eng(ExprEng), EnvMgr(alloc), GDMFactory(alloc),
    svalBuilder(createSimpleSValBuilder(alloc, Ctx, *this)),
    CallEventMgr(new CallEventManager(alloc)), Alloc(alloc) {
  StoreMgr = (*CreateSMgr)(*this);
  ConstraintMgr = (*CreateCMgr)(*this, ExprEng);
}
 
 
ProgramStateManager::~ProgramStateManager() {
  for (GDMContextsTy::iterator I=GDMContexts.begin(), E=GDMContexts.end();
       I!=E; ++I)
    I->second.second(I->second.first);
}
 
ProgramStateRef ProgramStateManager::removeDeadBindingsFromEnvironmentAndStore(
    ProgramStateRef state, const StackFrameContext *LCtx,
    SymbolReaper &SymReaper) {
 
  // This code essentially performs a "mark-and-sweep" of the VariableBindings.
  // The roots are any Block-level exprs and Decls that our liveness algorithm
  // tells us are live.  We then see what Decls they may reference, and keep
  // those around.  This code more than likely can be made faster, and the
  // frequency of which this method is called should be experimented with
  // for optimum performance.
  ProgramState NewState = *state;
 
  NewState.Env = EnvMgr.removeDeadBindings(NewState.Env, SymReaper, state);
 
  // Clean up the store.
  StoreRef newStore = StoreMgr->removeDeadBindings(NewState.getStore(), LCtx,
                                                   SymReaper);
  NewState.setStore(newStore);
  SymReaper.setReapedStore(newStore);
 
  return getPersistentState(NewState);
}
 
ProgramStateRef ProgramState::bindLoc(Loc LV,
                                      SVal V,
                                      const LocationContext *LCtx,
                                      bool notifyChanges) const {
  ProgramStateManager &Mgr = getStateManager();
  ProgramStateRef newState = makeWithStore(Mgr.StoreMgr->Bind(getStore(),
                                                             LV, V));
  const MemRegion *MR = LV.getAsRegion();
  if (MR && notifyChanges)
    return Mgr.getOwningEngine().processRegionChange(newState, MR, LCtx);
 
  return newState;
}
 
ProgramStateRef
ProgramState::bindDefaultInitial(SVal loc, SVal V,
                                 const LocationContext *LCtx) const {
  ProgramStateManager &Mgr = getStateManager();
  const MemRegion *R = loc.castAs<loc::MemRegionVal>().getRegion();
  const StoreRef &newStore = Mgr.StoreMgr->BindDefaultInitial(getStore(), R, V);
  ProgramStateRef new_state = makeWithStore(newStore);
  return Mgr.getOwningEngine().processRegionChange(new_state, R, LCtx);
}
 
ProgramStateRef
ProgramState::bindDefaultZero(SVal loc, const LocationContext *LCtx) const {
  ProgramStateManager &Mgr = getStateManager();
  const MemRegion *R = loc.castAs<loc::MemRegionVal>().getRegion();
  const StoreRef &newStore = Mgr.StoreMgr->BindDefaultZero(getStore(), R);
  ProgramStateRef new_state = makeWithStore(newStore);
  return Mgr.getOwningEngine().processRegionChange(new_state, R, LCtx);
}
 
typedef ArrayRef<const MemRegion *> RegionList;
typedef ArrayRef<SVal> ValueList;
 
ProgramStateRef ProgramState::invalidateRegions(
    RegionList Regions, const Stmt *S, unsigned Count,
    const LocationContext *LCtx, bool CausedByPointerEscape,
    InvalidatedSymbols *IS, const CallEvent *Call,
    RegionAndSymbolInvalidationTraits *ITraits) const {
  SmallVector<SVal, 8> Values;
  for (const MemRegion *Reg : Regions)
    Values.push_back(loc::MemRegionVal(Reg));
 
  return invalidateRegions(Values, S, Count, LCtx, CausedByPointerEscape, IS,
                           Call, ITraits);
}
 
ProgramStateRef ProgramState::invalidateRegions(
    ValueList Values, const Stmt *S, unsigned Count,
    const LocationContext *LCtx, bool CausedByPointerEscape,
    InvalidatedSymbols *IS, const CallEvent *Call,
    RegionAndSymbolInvalidationTraits *ITraits) const {
 
  ProgramStateManager &Mgr = getStateManager();
  ExprEngine &Eng = Mgr.getOwningEngine();
 
  InvalidatedSymbols InvalidatedSyms;
  if (!IS)
    IS = &InvalidatedSyms;
 
  RegionAndSymbolInvalidationTraits ITraitsLocal;
  if (!ITraits)
    ITraits = &ITraitsLocal;
 
  StoreManager::InvalidatedRegions TopLevelInvalidated;
  StoreManager::InvalidatedRegions Invalidated;
  const StoreRef &NewStore = Mgr.StoreMgr->invalidateRegions(
      getStore(), Values, S, Count, LCtx, Call, *IS, *ITraits,
      &TopLevelInvalidated, &Invalidated);
 
  ProgramStateRef NewState = makeWithStore(NewStore);
 
  if (CausedByPointerEscape) {
    NewState = Eng.notifyCheckersOfPointerEscape(
        NewState, IS, TopLevelInvalidated, Call, *ITraits);
  }
 
  return Eng.processRegionChanges(NewState, IS, TopLevelInvalidated,
                                  Invalidated, LCtx, Call);
}
 
ProgramStateRef ProgramState::killBinding(Loc LV) const {
  Store OldStore = getStore();
  const StoreRef &newStore =
    getStateManager().StoreMgr->killBinding(OldStore, LV);
 
  if (newStore.getStore() == OldStore)
    return this;
 
  return makeWithStore(newStore);
}
 
/// We should never form a MemRegion that would wrap a TypedValueRegion of a
/// reference type. What we actually wanted was to create a MemRegion refering
/// to the pointee of that reference.
SVal ProgramState::desugarReference(SVal Val) const {
  const auto *TyReg = dyn_cast_or_null<TypedValueRegion>(Val.getAsRegion());
  if (!TyReg || !TyReg->getValueType()->isReferenceType())
    return Val;
  return getSVal(TyReg);
}
 
/// SymbolicRegions are expected to be wrapped by an ElementRegion as a
/// canonical representation. As a canonical representation, SymbolicRegions
/// should be wrapped by ElementRegions before getting a FieldRegion.
/// See f8643a9b31c4029942f67d4534c9139b45173504 why.
SVal ProgramState::wrapSymbolicRegion(SVal Val) const {
  const auto *BaseReg = dyn_cast_or_null<SymbolicRegion>(Val.getAsRegion());
  if (!BaseReg)
    return Val;
 
  StoreManager &SM = getStateManager().getStoreManager();
  QualType ElemTy = BaseReg->getPointeeStaticType();
  return loc::MemRegionVal{SM.GetElementZeroRegion(BaseReg, ElemTy)};
}
 
ProgramStateRef
ProgramState::enterStackFrame(const CallEvent &Call,
                              const StackFrameContext *CalleeCtx) const {
  const StoreRef &NewStore =
    getStateManager().StoreMgr->enterStackFrame(getStore(), Call, CalleeCtx);
  return makeWithStore(NewStore);
}
 
SVal ProgramState::getSelfSVal(const LocationContext *LCtx) const {
  const ImplicitParamDecl *SelfDecl = LCtx->getSelfDecl();
  if (!SelfDecl)
    return SVal();
  return getSVal(getRegion(SelfDecl, LCtx));
}
 
SVal ProgramState::getSValAsScalarOrLoc(const MemRegion *R) const {
  // We only want to do fetches from regions that we can actually bind
  // values.  For example, SymbolicRegions of type 'id<...>' cannot
  // have direct bindings (but their can be bindings on their subregions).
  if (!R->isBoundable())
    return UnknownVal();
 
  if (const TypedValueRegion *TR = dyn_cast<TypedValueRegion>(R)) {
    QualType T = TR->getValueType();
    if (Loc::isLocType(T) || T->isIntegralOrEnumerationType())
      return getSVal(R);
  }
 
  return UnknownVal();
}
 
SVal ProgramState::getSVal(Loc location, QualType T) const {
  SVal V = getRawSVal(location, T);
 
  // If 'V' is a symbolic value that is *perfectly* constrained to
  // be a constant value, use that value instead to lessen the burden
  // on later analysis stages (so we have less symbolic values to reason
  // about).
  // We only go into this branch if we can convert the APSInt value we have
  // to the type of T, which is not always the case (e.g. for void).
  if (!T.isNull() && (T->isIntegralOrEnumerationType() || Loc::isLocType(T))) {
    if (SymbolRef sym = V.getAsSymbol()) {
      if (const llvm::APSInt *Int = getStateManager()
                                    .getConstraintManager()
                                    .getSymVal(this, sym)) {
        // FIXME: Because we don't correctly model (yet) sign-extension
        // and truncation of symbolic values, we need to convert
        // the integer value to the correct signedness and bitwidth.
        //
        // This shows up in the following:
        //
        //   char foo();
        //   unsigned x = foo();
        //   if (x == 54)
        //     ...
        //
        //  The symbolic value stored to 'x' is actually the conjured
        //  symbol for the call to foo(); the type of that symbol is 'char',
        //  not unsigned.
        APSIntPtr NewV = getBasicVals().Convert(T, *Int);
        if (V.getAs<Loc>())
          return loc::ConcreteInt(NewV);
        return nonloc::ConcreteInt(NewV);
      }
    }
  }
 
  return V;
}
 
ProgramStateRef ProgramState::BindExpr(const Stmt *S,
                                           const LocationContext *LCtx,
                                           SVal V, bool Invalidate) const{
  Environment NewEnv =
    getStateManager().EnvMgr.bindExpr(Env, EnvironmentEntry(S, LCtx), V,
                                      Invalidate);
  if (NewEnv == Env)
    return this;
 
  ProgramState NewSt = *this;
  NewSt.Env = NewEnv;
  return getStateManager().getPersistentState(NewSt);
}
 
[[nodiscard]] std::pair<ProgramStateRef, ProgramStateRef>
ProgramState::assumeInBoundDual(DefinedOrUnknownSVal Idx,
                                DefinedOrUnknownSVal UpperBound,
                                QualType indexTy) const {
  if (Idx.isUnknown() || UpperBound.isUnknown())
    return {this, this};
 
  // Build an expression for 0 <= Idx < UpperBound.
  // This is the same as Idx + MIN < UpperBound + MIN, if overflow is allowed.
  // FIXME: This should probably be part of SValBuilder.
  ProgramStateManager &SM = getStateManager();
  SValBuilder &svalBuilder = SM.getSValBuilder();
  ASTContext &Ctx = svalBuilder.getContext();
 
  // Get the offset: the minimum value of the array index type.
  BasicValueFactory &BVF = svalBuilder.getBasicValueFactory();
  if (indexTy.isNull())
    indexTy = svalBuilder.getArrayIndexType();
  nonloc::ConcreteInt Min(BVF.getMinValue(indexTy));
 
  // Adjust the index.
  SVal newIdx = svalBuilder.evalBinOpNN(this, BO_Add,
                                        Idx.castAs<NonLoc>(), Min, indexTy);
  if (newIdx.isUnknownOrUndef())
    return {this, this};
 
  // Adjust the upper bound.
  SVal newBound =
    svalBuilder.evalBinOpNN(this, BO_Add, UpperBound.castAs<NonLoc>(),
                            Min, indexTy);
 
  if (newBound.isUnknownOrUndef())
    return {this, this};
 
  // Build the actual comparison.
  SVal inBound = svalBuilder.evalBinOpNN(this, BO_LT, newIdx.castAs<NonLoc>(),
                                         newBound.castAs<NonLoc>(), Ctx.IntTy);
  if (inBound.isUnknownOrUndef())
    return {this, this};
 
  // Finally, let the constraint manager take care of it.
  ConstraintManager &CM = SM.getConstraintManager();
  return CM.assumeDual(this, inBound.castAs<DefinedSVal>());
}
 
ProgramStateRef ProgramState::assumeInBound(DefinedOrUnknownSVal Idx,
                                            DefinedOrUnknownSVal UpperBound,
                                            bool Assumption,
                                            QualType indexTy) const {
  std::pair<ProgramStateRef, ProgramStateRef> R =
      assumeInBoundDual(Idx, UpperBound, indexTy);
  return Assumption ? R.first : R.second;
}
 
ConditionTruthVal ProgramState::isNonNull(SVal V) const {
  ConditionTruthVal IsNull = isNull(V);
  if (IsNull.isUnderconstrained())
    return IsNull;
  return ConditionTruthVal(!IsNull.getValue());
}
 
ConditionTruthVal ProgramState::areEqual(SVal Lhs, SVal Rhs) const {
  return stateMgr->getSValBuilder().areEqual(this, Lhs, Rhs);
}
 
ConditionTruthVal ProgramState::isNull(SVal V) const {
  if (V.isZeroConstant())
    return true;
 
  if (V.isConstant())
    return false;
 
  SymbolRef Sym = V.getAsSymbol(/* IncludeBaseRegion */ true);
  if (!Sym)
    return ConditionTruthVal();
 
  return getStateManager().ConstraintMgr->isNull(this, Sym);
}
 
ProgramStateRef ProgramStateManager::getInitialState(const LocationContext *InitLoc) {
  ProgramState State(this,
                EnvMgr.getInitialEnvironment(),
                StoreMgr->getInitialStore(InitLoc),
                GDMFactory.getEmptyMap());
 
  return getPersistentState(State);
}
 
ProgramStateRef ProgramStateManager::getPersistentStateWithGDM(
                                                     ProgramStateRef FromState,
                                                     ProgramStateRef GDMState) {
  ProgramState NewState(*FromState);
  NewState.GDM = GDMState->GDM;
  return getPersistentState(NewState);
}
 
ProgramStateRef ProgramStateManager::getPersistentState(ProgramState &State) {
 
  llvm::FoldingSetNodeID ID;
  State.Profile(ID);
  void *InsertPos;
 
  if (ProgramState *I = StateSet.FindNodeOrInsertPos(ID, InsertPos))
    return I;
 
  ProgramState *newState = nullptr;
  if (!freeStates.empty()) {
    newState = freeStates.back();
    freeStates.pop_back();
  }
  else {
    newState = Alloc.Allocate<ProgramState>();
  }
  new (newState) ProgramState(State);
  StateSet.InsertNode(newState, InsertPos);
  return newState;
}
 
ProgramStateRef ProgramState::makeWithStore(const StoreRef &store) const {
  ProgramState NewSt(*this);
  NewSt.setStore(store);
  return getStateManager().getPersistentState(NewSt);
}
 
ProgramStateRef ProgramState::cloneAsPosteriorlyOverconstrained() const {
  ProgramState NewSt(*this);
  NewSt.PosteriorlyOverconstrained = true;
  return getStateManager().getPersistentState(NewSt);
}
 
void ProgramState::setStore(const StoreRef &newStore) {
  Store newStoreStore = newStore.getStore();
  if (newStoreStore)
    stateMgr->getStoreManager().incrementReferenceCount(newStoreStore);
  if (store)
    stateMgr->getStoreManager().decrementReferenceCount(store);
  store = newStoreStore;
}
 
SVal ProgramState::getLValue(const FieldDecl *D, SVal Base) const {
  Base = desugarReference(Base);
  Base = wrapSymbolicRegion(Base);
  return getStateManager().StoreMgr->getLValueField(D, Base);
}
 
SVal ProgramState::getLValue(const IndirectFieldDecl *D, SVal Base) const {
  StoreManager &SM = *getStateManager().StoreMgr;
  Base = desugarReference(Base);
  Base = wrapSymbolicRegion(Base);
 
  // FIXME: This should work with `SM.getLValueField(D->getAnonField(), Base)`,
  // but that would break some tests. There is probably a bug somewhere that it
  // would expose.
  for (const auto *I : D->chain()) {
    Base = SM.getLValueField(cast<FieldDecl>(I), Base);
  }
  return Base;
}
 
//===----------------------------------------------------------------------===//
//  State pretty-printing.
//===----------------------------------------------------------------------===//
 
void ProgramState::printJson(raw_ostream &Out, const LocationContext *LCtx,
                             const char *NL, unsigned int Space,
                             bool IsDot) const {
  Indent(Out, Space, IsDot) << "\"program_state\": {" << NL;
  ++Space;
 
  ProgramStateManager &Mgr = getStateManager();
 
  // Print the store.
  Mgr.getStoreManager().printJson(Out, getStore(), NL, Space, IsDot);
 
  // Print out the environment.
  Env.printJson(Out, Mgr.getContext(), LCtx, NL, Space, IsDot);
 
  // Print out the constraints.
  Mgr.getConstraintManager().printJson(Out, this, NL, Space, IsDot);
 
  // Print out the tracked dynamic types.
  printDynamicTypeInfoJson(Out, this, NL, Space, IsDot);
 
  // Print checker-specific data.
  Mgr.getOwningEngine().