xref: /llvm-project/clang/lib/StaticAnalyzer/Checkers/MallocChecker.cpp (revision 21c4dc7997b83e83f87c26a97c104dcdd95f1d0f)

//=== MallocChecker.cpp - A malloc/free checker -------------------*- 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 defines a variety of memory management related checkers, such as
// leak, double free, and use-after-free.
//
// The following checkers are defined here:
//
//   * MallocChecker
//       Despite its name, it models all sorts of memory allocations and
//       de- or reallocation, including but not limited to malloc, free,
//       relloc, new, delete. It also reports on a variety of memory misuse
//       errors.
//       Many other checkers interact very closely with this checker, in fact,
//       most are merely options to this one. Other checkers may register
//       MallocChecker, but do not enable MallocChecker's reports (more details
//       to follow around its field, ChecksEnabled).
//       It also has a boolean "Optimistic" checker option, which if set to true
//       will cause the checker to model user defined memory management related
//       functions annotated via the attribute ownership_takes, ownership_holds
//       and ownership_returns.
//
//   * NewDeleteChecker
//       Enables the modeling of new, new[], delete, delete[] in MallocChecker,
//       and checks for related double-free and use-after-free errors.
//
//   * NewDeleteLeaksChecker
//       Checks for leaks related to new, new[], delete, delete[].
//       Depends on NewDeleteChecker.
//
//   * MismatchedDeallocatorChecker
//       Enables checking whether memory is deallocated with the correspending
//       allocation function in MallocChecker, such as malloc() allocated
//       regions are only freed by free(), new by delete, new[] by delete[].
//
//  InnerPointerChecker interacts very closely with MallocChecker, but unlike
//  the above checkers, it has it's own file, hence the many InnerPointerChecker
//  related headers and non-static functions.
//
//===----------------------------------------------------------------------===//

#include "AllocationState.h"
#include "InterCheckerAPI.h"
#include "clang/AST/Attr.h"
#include "clang/AST/DeclCXX.h"
#include "clang/AST/DeclTemplate.h"
#include "clang/AST/Expr.h"
#include "clang/AST/ExprCXX.h"
#include "clang/AST/ParentMap.h"
#include "clang/ASTMatchers/ASTMatchFinder.h"
#include "clang/ASTMatchers/ASTMatchers.h"
#include "clang/Analysis/ProgramPoint.h"
#include "clang/Basic/LLVM.h"
#include "clang/Basic/SourceManager.h"
#include "clang/Basic/TargetInfo.h"
#include "clang/Lex/Lexer.h"
#include "clang/StaticAnalyzer/Checkers/BuiltinCheckerRegistration.h"
#include "clang/StaticAnalyzer/Core/BugReporter/BugType.h"
#include "clang/StaticAnalyzer/Core/BugReporter/CommonBugCategories.h"
#include "clang/StaticAnalyzer/Core/Checker.h"
#include "clang/StaticAnalyzer/Core/CheckerManager.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/CallDescription.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/CallEvent.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/CheckerHelpers.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/DynamicExtent.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/ExplodedGraph.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/ProgramState.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/ProgramStateTrait.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/ProgramState_Fwd.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/SVals.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/StoreRef.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/SymbolManager.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/SetOperations.h"
#include "llvm/ADT/SmallString.h"
#include "llvm/ADT/StringExtras.h"
#include "llvm/Support/Casting.h"
#include "llvm/Support/Compiler.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/raw_ostream.h"
#include <climits>
#include <functional>
#include <optional>
#include <utility>

using namespace clang;
using namespace ento;
using namespace std::placeholders;

//===----------------------------------------------------------------------===//
// The types of allocation we're modeling. This is used to check whether a
// dynamically allocated object is deallocated with the correct function, like
// not using operator delete on an object created by malloc(), or alloca regions
// aren't ever deallocated manually.
//===----------------------------------------------------------------------===//

namespace {

// Used to check correspondence between allocators and deallocators.
enum AllocationFamily {
  AF_None,
  AF_Malloc,
  AF_CXXNew,
  AF_CXXNewArray,
  AF_IfNameIndex,
  AF_Alloca,
  AF_InnerBuffer
};

} // end of anonymous namespace

/// Print names of allocators and deallocators.
///
/// \returns true on success.
static bool printMemFnName(raw_ostream &os, CheckerContext &C, const Expr *E);

/// Print expected name of an allocator based on the deallocator's family
/// derived from the DeallocExpr.
static void printExpectedAllocName(raw_ostream &os, AllocationFamily Family);

/// Print expected name of a deallocator based on the allocator's
/// family.
static void printExpectedDeallocName(raw_ostream &os, AllocationFamily Family);

//===----------------------------------------------------------------------===//
// The state of a symbol, in terms of memory management.
//===----------------------------------------------------------------------===//

namespace {

class RefState {
  enum Kind {
    // Reference to allocated memory.
    Allocated,
    // Reference to zero-allocated memory.
    AllocatedOfSizeZero,
    // Reference to released/freed memory.
    Released,
    // The responsibility for freeing resources has transferred from
    // this reference. A relinquished symbol should not be freed.
    Relinquished,
    // We are no longer guaranteed to have observed all manipulations
    // of this pointer/memory. For example, it could have been
    // passed as a parameter to an opaque function.
    Escaped
  };

  const Stmt *S;

  Kind K;
  AllocationFamily Family;

  RefState(Kind k, const Stmt *s, AllocationFamily family)
      : S(s), K(k), Family(family) {
    assert(family != AF_None);
  }

public:
  bool isAllocated() const { return K == Allocated; }
  bool isAllocatedOfSizeZero() const { return K == AllocatedOfSizeZero; }
  bool isReleased() const { return K == Released; }
  bool isRelinquished() const { return K == Relinquished; }
  bool isEscaped() const { return K == Escaped; }
  AllocationFamily getAllocationFamily() const { return Family; }
  const Stmt *getStmt() const { return S; }

  bool operator==(const RefState &X) const {
    return K == X.K && S == X.S && Family == X.Family;
  }

  static RefState getAllocated(AllocationFamily family, const Stmt *s) {
    return RefState(Allocated, s, family);
  }
  static RefState getAllocatedOfSizeZero(const RefState *RS) {
    return RefState(AllocatedOfSizeZero, RS->getStmt(),
                    RS->getAllocationFamily());
  }
  static RefState getReleased(AllocationFamily family, const Stmt *s) {
    return RefState(Released, s, family);
  }
  static RefState getRelinquished(AllocationFamily family, const Stmt *s) {
    return RefState(Relinquished, s, family);
  }
  static RefState getEscaped(const RefState *RS) {
    return RefState(Escaped, RS->getStmt(), RS->getAllocationFamily());
  }

  void Profile(llvm::FoldingSetNodeID &ID) const {
    ID.AddInteger(K);
    ID.AddPointer(S);
    ID.AddInteger(Family);
  }

  LLVM_DUMP_METHOD void dump(raw_ostream &OS) const {
    switch (K) {
#define CASE(ID) case ID: OS << #ID; break;
    CASE(Allocated)
    CASE(AllocatedOfSizeZero)
    CASE(Released)
    CASE(Relinquished)
    CASE(Escaped)
    }
  }

  LLVM_DUMP_METHOD void dump() const { dump(llvm::errs()); }
};

} // end of anonymous namespace

REGISTER_MAP_WITH_PROGRAMSTATE(RegionState, SymbolRef, RefState)

/// Check if the memory associated with this symbol was released.
static bool isReleased(SymbolRef Sym, CheckerContext &C);

/// Update the RefState to reflect the new memory allocation.
/// The optional \p RetVal parameter specifies the newly allocated pointer
/// value; if unspecified, the value of expression \p E is used.
static ProgramStateRef
MallocUpdateRefState(CheckerContext &C, const Expr *E, ProgramStateRef State,
                     AllocationFamily Family,
                     Optional<SVal> RetVal = std::nullopt);

//===----------------------------------------------------------------------===//
// The modeling of memory reallocation.
//
// The terminology 'toPtr' and 'fromPtr' will be used:
//   toPtr = realloc(fromPtr, 20);
//===----------------------------------------------------------------------===//

REGISTER_SET_WITH_PROGRAMSTATE(ReallocSizeZeroSymbols, SymbolRef)

namespace {

/// The state of 'fromPtr' after reallocation is known to have failed.
enum OwnershipAfterReallocKind {
  // The symbol needs to be freed (e.g.: realloc)
  OAR_ToBeFreedAfterFailure,
  // The symbol has been freed (e.g.: reallocf)
  OAR_FreeOnFailure,
  // The symbol doesn't have to freed (e.g.: we aren't sure if, how and where
  // 'fromPtr' was allocated:
  //    void Haha(int *ptr) {
  //      ptr = realloc(ptr, 67);
  //      // ...
  //    }
  // ).
  OAR_DoNotTrackAfterFailure
};

/// Stores information about the 'fromPtr' symbol after reallocation.
///
/// This is important because realloc may fail, and that needs special modeling.
/// Whether reallocation failed or not will not be known until later, so we'll
/// store whether upon failure 'fromPtr' will be freed, or needs to be freed
/// later, etc.
struct ReallocPair {

  // The 'fromPtr'.
  SymbolRef ReallocatedSym;
  OwnershipAfterReallocKind Kind;

  ReallocPair(SymbolRef S, OwnershipAfterReallocKind K)
      : ReallocatedSym(S), Kind(K) {}
  void Profile(llvm::FoldingSetNodeID &ID) const {
    ID.AddInteger(Kind);
    ID.AddPointer(ReallocatedSym);
  }
  bool operator==(const ReallocPair &X) const {
    return ReallocatedSym == X.ReallocatedSym &&
           Kind == X.Kind;
  }
};

} // end of anonymous namespace

REGISTER_MAP_WITH_PROGRAMSTATE(ReallocPairs, SymbolRef, ReallocPair)

/// Tells if the callee is one of the builtin new/delete operators, including
/// placement operators and other standard overloads.
static bool isStandardNewDelete(const FunctionDecl *FD);
static bool isStandardNewDelete(const CallEvent &Call) {
  if (!Call.getDecl() || !isa<FunctionDecl>(Call.getDecl()))
    return false;
  return isStandardNewDelete(cast<FunctionDecl>(Call.getDecl()));
}

//===----------------------------------------------------------------------===//
// Definition of the MallocChecker class.
//===----------------------------------------------------------------------===//

namespace {

class MallocChecker
    : public Checker<check::DeadSymbols, check::PointerEscape,
                     check::ConstPointerEscape, check::PreStmt<ReturnStmt>,
                     check::EndFunction, check::PreCall, check::PostCall,
                     check::NewAllocator, check::PostStmt<BlockExpr>,
                     check::PostObjCMessage, check::Location, eval::Assume> {
public:
  /// In pessimistic mode, the checker assumes that it does not know which
  /// functions might free the memory.
  /// In optimistic mode, the checker assumes that all user-defined functions
  /// which might free a pointer are annotated.
  bool ShouldIncludeOwnershipAnnotatedFunctions = false;

  bool ShouldRegisterNoOwnershipChangeVisitor = false;

  /// Many checkers are essentially built into this one, so enabling them will
  /// make MallocChecker perform additional modeling and reporting.
  enum CheckKind {
    /// When a subchecker is enabled but MallocChecker isn't, model memory
    /// management but do not emit warnings emitted with MallocChecker only
    /// enabled.
    CK_MallocChecker,
    CK_NewDeleteChecker,
    CK_NewDeleteLeaksChecker,
    CK_MismatchedDeallocatorChecker,
    CK_InnerPointerChecker,
    CK_NumCheckKinds
  };

  using LeakInfo = std::pair<const ExplodedNode *, const MemRegion *>;

  bool ChecksEnabled[CK_NumCheckKinds] = {false};
  CheckerNameRef CheckNames[CK_NumCheckKinds];

  void checkPreCall(const CallEvent &Call, CheckerContext &C) const;
  void checkPostCall(const CallEvent &Call, CheckerContext &C) const;
  void checkNewAllocator(const CXXAllocatorCall &Call, CheckerContext &C) const;
  void checkPostObjCMessage(const ObjCMethodCall &Call, CheckerContext &C) const;
  void checkPostStmt(const BlockExpr *BE, CheckerContext &C) const;
  void checkDeadSymbols(SymbolReaper &SymReaper, CheckerContext &C) const;
  void checkPreStmt(const ReturnStmt *S, CheckerContext &C) const;
  void checkEndFunction(const ReturnStmt *S, CheckerContext &C) const;
  ProgramStateRef evalAssume(ProgramStateRef state, SVal Cond,
                            bool Assumption) const;
  void checkLocation(SVal l, bool isLoad, const Stmt *S,
                     CheckerContext &C) const;

  ProgramStateRef checkPointerEscape(ProgramStateRef State,
                                    const InvalidatedSymbols &Escaped,
                                    const CallEvent *Call,
                                    PointerEscapeKind Kind) const;
  ProgramStateRef checkConstPointerEscape(ProgramStateRef State,
                                          const InvalidatedSymbols &Escaped,
                                          const CallEvent *Call,
                                          PointerEscapeKind Kind) const;

  void printState(raw_ostream &Out, ProgramStateRef State,
                  const char *NL, const char *Sep) const override;

private:
  mutable std::unique_ptr<BugType> BT_DoubleFree[CK_NumCheckKinds];
  mutable std::unique_ptr<BugType> BT_DoubleDelete;
  mutable std::unique_ptr<BugType> BT_Leak[CK_NumCheckKinds];
  mutable std::unique_ptr<BugType> BT_UseFree[CK_NumCheckKinds];
  mutable std::unique_ptr<BugType> BT_BadFree[CK_NumCheckKinds];
  mutable std::unique_ptr<BugType> BT_FreeAlloca[CK_NumCheckKinds];
  mutable std::unique_ptr<BugType> BT_MismatchedDealloc;
  mutable std::unique_ptr<BugType> BT_OffsetFree[CK_NumCheckKinds];
  mutable std::unique_ptr<BugType> BT_UseZerroAllocated[CK_NumCheckKinds];

#define CHECK_FN(NAME)                                                         \
  void NAME(const CallEvent &Call, CheckerContext &C) const;

  CHECK_FN(checkFree)
  CHECK_FN(checkIfNameIndex)
  CHECK_FN(checkBasicAlloc)
  CHECK_FN(checkKernelMalloc)
  CHECK_FN(checkCalloc)
  CHECK_FN(checkAlloca)
  CHECK_FN(checkStrdup)
  CHECK_FN(checkIfFreeNameIndex)
  CHECK_FN(checkCXXNewOrCXXDelete)
  CHECK_FN(checkGMalloc0)
  CHECK_FN(checkGMemdup)
  CHECK_FN(checkGMallocN)
  CHECK_FN(checkGMallocN0)
  CHECK_FN(checkReallocN)
  CHECK_FN(checkOwnershipAttr)

  void checkRealloc(const CallEvent &Call, CheckerContext &C,
                    bool ShouldFreeOnFail) const;

  using CheckFn = std::function<void(const MallocChecker *,
                                     const CallEvent &Call, CheckerContext &C)>;

  const CallDescriptionMap<CheckFn> FreeingMemFnMap{
      {{"free", 1}, &MallocChecker::checkFree},
      {{"if_freenameindex", 1}, &MallocChecker::checkIfFreeNameIndex},
      {{"kfree", 1}, &MallocChecker::checkFree},
      {{"g_free", 1}, &MallocChecker::checkFree},
  };

  bool isFreeingCall(const CallEvent &Call) const;
  static bool isFreeingOwnershipAttrCall(const FunctionDecl *Func);

  friend class NoOwnershipChangeVisitor;

  CallDescriptionMap<CheckFn> AllocatingMemFnMap{
      {{"alloca", 1}, &MallocChecker::checkAlloca},
      {{"_alloca", 1}, &MallocChecker::checkAlloca},
      {{"malloc", 1}, &MallocChecker::checkBasicAlloc},
      {{"malloc", 3}, &MallocChecker::checkKernelMalloc},
      {{"calloc", 2}, &MallocChecker::checkCalloc},
      {{"valloc", 1}, &MallocChecker::checkBasicAlloc},
      {{CDF_MaybeBuiltin, "strndup", 2}, &MallocChecker::checkStrdup},
      {{CDF_MaybeBuiltin, "strdup", 1}, &MallocChecker::checkStrdup},
      {{"_strdup", 1}, &MallocChecker::checkStrdup},
      {{"kmalloc", 2}, &MallocChecker::checkKernelMalloc},
      {{"if_nameindex", 1}, &MallocChecker::checkIfNameIndex},
      {{CDF_MaybeBuiltin, "wcsdup", 1}, &MallocChecker::checkStrdup},
      {{CDF_MaybeBuiltin, "_wcsdup", 1}, &MallocChecker::checkStrdup},
      {{"g_malloc", 1}, &MallocChecker::checkBasicAlloc},
      {{"g_malloc0", 1}, &MallocChecker::checkGMalloc0},
      {{"g_try_malloc", 1}, &MallocChecker::checkBasicAlloc},
      {{"g_try_malloc0", 1}, &MallocChecker::checkGMalloc0},
      {{"g_memdup", 2}, &MallocChecker::checkGMemdup},
      {{"g_malloc_n", 2}, &MallocChecker::checkGMallocN},
      {{"g_malloc0_n", 2}, &MallocChecker::checkGMallocN0},
      {{"g_try_malloc_n", 2}, &MallocChecker::checkGMallocN},
      {{"g_try_malloc0_n", 2}, &MallocChecker::checkGMallocN0},
  };

  CallDescriptionMap<CheckFn> ReallocatingMemFnMap{
      {{"realloc", 2},
       std::bind(&MallocChecker::checkRealloc, _1, _2, _3, false)},
      {{"reallocf", 2},
       std::bind(&MallocChecker::checkRealloc, _1, _2, _3, true)},
      {{"g_realloc", 2},
       std::bind(&MallocChecker::checkRealloc, _1, _2, _3, false)},
      {{"g_try_realloc", 2},
       std::bind(&MallocChecker::checkRealloc, _1, _2, _3, false)},
      {{"g_realloc_n", 3}, &MallocChecker::checkReallocN},
      {{"g_try_realloc_n", 3}, &MallocChecker::checkReallocN},
  };

  bool isMemCall(const CallEvent &Call) const;

  // TODO: Remove mutable by moving the initializtaion to the registry function.
  mutable std::optional<uint64_t> KernelZeroFlagVal;

  using KernelZeroSizePtrValueTy = Optional<int>;
  /// Store the value of macro called `ZERO_SIZE_PTR`.
  /// The value is initialized at first use, before first use the outer
  /// Optional is empty, afterwards it contains another Optional that indicates
  /// if the macro value could be determined, and if yes the value itself.
  mutable std::optional<KernelZeroSizePtrValueTy> KernelZeroSizePtrValue;

  /// Process C++ operator new()'s allocation, which is the part of C++
  /// new-expression that goes before the constructor.
  [[nodiscard]] ProgramStateRef
  processNewAllocation(const CXXAllocatorCall &Call, CheckerContext &C,
                       AllocationFamily Family) const;

  /// Perform a zero-allocation check.
  ///
  /// \param [in] Call The expression that allocates memory.
  /// \param [in] IndexOfSizeArg Index of the argument that specifies the size
  ///   of the memory that needs to be allocated. E.g. for malloc, this would be
  ///   0.
  /// \param [in] RetVal Specifies the newly allocated pointer value;
  ///   if unspecified, the value of expression \p E is used.
  [[nodiscard]] static ProgramStateRef
  ProcessZeroAllocCheck(const CallEvent &Call, const unsigned IndexOfSizeArg,
                        ProgramStateRef State,
                        Optional<SVal> RetVal = std::nullopt);

  /// Model functions with the ownership_returns attribute.
  ///
  /// User-defined function may have the ownership_returns attribute, which
  /// annotates that the function returns with an object that was allocated on
  /// the heap, and passes the ownertship to the callee.
  ///
  ///   void __attribute((ownership_returns(malloc, 1))) *my_malloc(size_t);
  ///
  /// It has two parameters:
  ///   - first: name of the resource (e.g. 'malloc')
  ///   - (OPTIONAL) second: size of the allocated region
  ///
  /// \param [in] Call The expression that allocates memory.
  /// \param [in] Att The ownership_returns attribute.
  /// \param [in] State The \c ProgramState right before allocation.
  /// \returns The ProgramState right after allocation.
  [[nodiscard]] ProgramStateRef
  MallocMemReturnsAttr(CheckerContext &C, const CallEvent &Call,
                       const OwnershipAttr *Att, ProgramStateRef State) const;

  /// Models memory allocation.
  ///
  /// \param [in] Call The expression that allocates memory.
  /// \param [in] SizeEx Size of the memory that needs to be allocated.
  /// \param [in] Init The value the allocated memory needs to be initialized.
  /// with. For example, \c calloc initializes the allocated memory to 0,
  /// malloc leaves it undefined.
  /// \param [in] State The \c ProgramState right before allocation.
  /// \returns The ProgramState right after allocation.
  [[nodiscard]] static ProgramStateRef
  MallocMemAux(CheckerContext &C, const CallEvent &Call, const Expr *SizeEx,
               SVal Init, ProgramStateRef State, AllocationFamily Family);

  /// Models memory allocation.
  ///
  /// \param [in] Call The expression that allocates memory.
  /// \param [in] Size Size of the memory that needs to be allocated.
  /// \param [in] Init The value the allocated memory needs to be initialized.
  /// with. For example, \c calloc initializes the allocated memory to 0,
  /// malloc leaves it undefined.
  /// \param [in] State The \c ProgramState right before allocation.
  /// \returns The ProgramState right after allocation.
  [[nodiscard]] static ProgramStateRef
  MallocMemAux(CheckerContext &C, const CallEvent &Call, SVal Size, SVal Init,
               ProgramStateRef State, AllocationFamily Family);

  // Check if this malloc() for special flags. At present that means M_ZERO or
  // __GFP_ZERO (in which case, treat it like calloc).
  [[nodiscard]] llvm::Optional<ProgramStateRef>
  performKernelMalloc(const CallEvent &Call, CheckerContext &C,
                      const ProgramStateRef &State) const;

  /// Model functions with the ownership_takes and ownership_holds attributes.
  ///
  /// User-defined function may have the ownership_takes and/or ownership_holds
  /// attributes, which annotates that the function frees the memory passed as a
  /// parameter.
  ///
  ///   void __attribute((ownership_takes(malloc, 1))) my_free(void *);
  ///   void __attribute((ownership_holds(malloc, 1))) my_hold(void *);
  ///
  /// They have two parameters:
  ///   - first: name of the resource (e.g. 'malloc')
  ///   - second: index of the parameter the attribute applies to
  ///
  /// \param [in] Call The expression that frees memory.
  /// \param [in] Att The ownership_takes or ownership_holds attribute.
  /// \param [in] State The \c ProgramState right before allocation.
  /// \returns The ProgramState right after deallocation.
  [[nodiscard]] ProgramStateRef FreeMemAttr(CheckerContext &C,
                                            const CallEvent &Call,
                                            const OwnershipAttr *Att,
                                            ProgramStateRef State) const;

  /// Models memory deallocation.
  ///
  /// \param [in] Call The expression that frees memory.
  /// \param [in] State The \c ProgramState right before allocation.
  /// \param [in] Num Index of the argument that needs to be freed. This is
  ///   normally 0, but for custom free functions it may be different.
  /// \param [in] Hold Whether the parameter at \p Index has the ownership_holds
  ///   attribute.
  /// \param [out] IsKnownToBeAllocated Whether the memory to be freed is known
  ///   to have been allocated, or in other words, the symbol to be freed was
  ///   registered as allocated by this checker. In the following case, \c ptr
  ///   isn't known to be allocated.
  ///      void Haha(int *ptr) {
  ///        ptr = realloc(ptr, 67);
  ///        // ...
  ///      }
  /// \param [in] ReturnsNullOnFailure Whether the memory deallocation function
  ///   we're modeling returns with Null on failure.
  /// \returns The ProgramState right after deallocation.
  [[nodiscard]] ProgramStateRef
  FreeMemAux(CheckerContext &C, const CallEvent &Call, ProgramStateRef State,
             unsigned Num, bool Hold, bool &IsKnownToBeAllocated,
             AllocationFamily Family, bool ReturnsNullOnFailure = false) const;

  /// Models memory deallocation.
  ///
  /// \param [in] ArgExpr The variable who's pointee needs to be freed.
  /// \param [in] Call The expression that frees the memory.
  /// \param [in] State The \c ProgramState right before allocation.
  ///   normally 0, but for custom free functions it may be different.
  /// \param [in] Hold Whether the parameter at \p Index has the ownership_holds
  ///   attribute.
  /// \param [out] IsKnownToBeAllocated Whether the memory to be freed is known
  ///   to have been allocated, or in other words, the symbol to be freed was
  ///   registered as allocated by this checker. In the following case, \c ptr
  ///   isn't known to be allocated.
  ///      void Haha(int *ptr) {
  ///        ptr = realloc(ptr, 67);
  ///        // ...
  ///      }
  /// \param [in] ReturnsNullOnFailure Whether the memory deallocation function
  ///   we're modeling returns with Null on failure.
  /// \returns The ProgramState right after deallocation.
  [[nodiscard]] ProgramStateRef
  FreeMemAux(CheckerContext &C, const Expr *ArgExpr, const CallEvent &Call,
             ProgramStateRef State, bool Hold, bool &IsKnownToBeAllocated,
             AllocationFamily Family, bool ReturnsNullOnFailure = false) const;

  // TODO: Needs some refactoring, as all other deallocation modeling
  // functions are suffering from out parameters and messy code due to how
  // realloc is handled.
  //
  /// Models memory reallocation.
  ///
  /// \param [in] Call The expression that reallocated memory
  /// \param [in] ShouldFreeOnFail Whether if reallocation fails, the supplied
  ///   memory should be freed.
  /// \param [in] State The \c ProgramState right before reallocation.
  /// \param [in] SuffixWithN Whether the reallocation function we're modeling
  ///   has an '_n' suffix, such as g_realloc_n.
  /// \returns The ProgramState right after reallocation.
  [[nodiscard]] ProgramStateRef
  ReallocMemAux(CheckerContext &C, const CallEvent &Call, bool ShouldFreeOnFail,
                ProgramStateRef State, AllocationFamily Family,
                bool SuffixWithN = false) const;

  /// Evaluates the buffer size that needs to be allocated.
  ///
  /// \param [in] Blocks The amount of blocks that needs to be allocated.
  /// \param [in] BlockBytes The size of a block.
  /// \returns The symbolic value of \p Blocks * \p BlockBytes.
  [[nodiscard]] static SVal evalMulForBufferSize(CheckerContext &C,
                                                 const Expr *Blocks,
                                                 const Expr *BlockBytes);

  /// Models zero initialized array allocation.
  ///
  /// \param [in] Call The expression that reallocated memory
  /// \param [in] State The \c ProgramState right before reallocation.
  /// \returns The ProgramState right after allocation.
  [[nodiscard]] static ProgramStateRef
  CallocMem(CheckerContext &C, const CallEvent &Call, ProgramStateRef State);

  /// See if deallocation happens in a suspicious context. If so, escape the
  /// pointers that otherwise would have been deallocated and return true.
  bool suppressDeallocationsInSuspiciousContexts(const CallEvent &Call,
                                                 CheckerContext &C) const;

  /// If in \p S  \p Sym is used, check whether \p Sym was already freed.
  bool checkUseAfterFree(SymbolRef Sym, CheckerContext &C, const Stmt *S) const;

  /// If in \p S \p Sym is used, check whether \p Sym was allocated as a zero
  /// sized memory region.
  void checkUseZeroAllocated(SymbolRef Sym, CheckerContext &C,
                             const Stmt *S) const;

  /// If in \p S \p Sym is being freed, check whether \p Sym was already freed.
  bool checkDoubleDelete(SymbolRef Sym, CheckerContext &C) const;

  /// Check if the function is known to free memory, or if it is
  /// "interesting" and should be modeled explicitly.
  ///
  /// \param [out] EscapingSymbol A function might not free memory in general,
  ///   but could be known to free a particular symbol. In this case, false is
  ///   returned and the single escaping symbol is returned through the out
  ///   parameter.
  ///
  /// We assume that pointers do not escape through calls to system functions
  /// not handled by this checker.
  bool mayFreeAnyEscapedMemoryOrIsModeledExplicitly(const CallEvent *Call,
                                   ProgramStateRef State,
                                   SymbolRef &EscapingSymbol) const;

  /// Implementation of the checkPointerEscape callbacks.
  [[nodiscard]] ProgramStateRef
  checkPointerEscapeAux(ProgramStateRef State,
                        const InvalidatedSymbols &Escaped,
                        const CallEvent *Call, PointerEscapeKind Kind,
                        bool IsConstPointerEscape) const;

  // Implementation of the checkPreStmt and checkEndFunction callbacks.
  void checkEscapeOnReturn(const ReturnStmt *S, CheckerContext &C) const;

  ///@{
  /// Tells if a given family/call/symbol is tracked by the current checker.
  /// Sets CheckKind to the kind of the checker responsible for this
  /// family/call/symbol.
  Optional<CheckKind> getCheckIfTracked(AllocationFamily Family,
                                        bool IsALeakCheck = false) const;

  Optional<CheckKind> getCheckIfTracked(CheckerContext &C, SymbolRef Sym,
                                        bool IsALeakCheck = false) const;
  ///@}
  static bool SummarizeValue(raw_ostream &os, SVal V);
  static bool SummarizeRegion(raw_ostream &os, const MemRegion *MR);

  void HandleNonHeapDealloc(CheckerContext &C, SVal ArgVal, SourceRange Range,
                            const Expr *DeallocExpr,
                            AllocationFamily Family) const;

  void HandleFreeAlloca(CheckerContext &C, SVal ArgVal,
                        SourceRange Range) const;

  void HandleMismatchedDealloc(CheckerContext &C, SourceRange Range,
                               const Expr *DeallocExpr, const RefState *RS,
                               SymbolRef Sym, bool OwnershipTransferred) const;

  void HandleOffsetFree(CheckerContext &C, SVal ArgVal, SourceRange Range,
                        const Expr *DeallocExpr, AllocationFamily Family,
                        const Expr *AllocExpr = nullptr) const;

  void HandleUseAfterFree(CheckerContext &C, SourceRange Range,
                          SymbolRef Sym) const;

  void HandleDoubleFree(CheckerContext &C, SourceRange Range, bool Released,
                        SymbolRef Sym, SymbolRef PrevSym) const;

  void HandleDoubleDelete(CheckerContext &C, SymbolRef Sym) const;

  void HandleUseZeroAlloc(CheckerContext &C, SourceRange Range,
                          SymbolRef Sym) const;

  void HandleFunctionPtrFree(CheckerContext &C, SVal ArgVal, SourceRange Range,
                             const Expr *FreeExpr,
                             AllocationFamily Family) const;

  /// Find the location of the allocation for Sym on the path leading to the
  /// exploded node N.
  static LeakInfo getAllocationSite(const ExplodedNode *N, SymbolRef Sym,
                                    CheckerContext &C);

  void HandleLeak(SymbolRef Sym, ExplodedNode *N, CheckerContext &C) const;

  /// Test if value in ArgVal equals to value in macro `ZERO_SIZE_PTR`.
  bool isArgZERO_SIZE_PTR(ProgramStateRef State, CheckerContext &C,
                          SVal ArgVal) const;
};
} // end anonymous namespace

//===----------------------------------------------------------------------===//
// Definition of NoOwnershipChangeVisitor.
//===----------------------------------------------------------------------===//

namespace {
class NoOwnershipChangeVisitor final : public NoStateChangeFuncVisitor {
  // The symbol whose (lack of) ownership change we are interested in.
  SymbolRef Sym;
  const MallocChecker &Checker;
  using OwnerSet = llvm::SmallPtrSet<const MemRegion *, 8>;

  // Collect which entities point to the allocated memory, and could be
  // responsible for deallocating it.
  class OwnershipBindingsHandler : public StoreManager::BindingsHandler {
    SymbolRef Sym;
    OwnerSet &Owners;

  public:
    OwnershipBindingsHandler(SymbolRef Sym, OwnerSet &Owners)
        : Sym(Sym), Owners(Owners) {}

    bool HandleBinding(StoreManager &SMgr, Store Store, const MemRegion *Region,
                       SVal Val) override {
      if (Val.getAsSymbol() == Sym)
        Owners.insert(Region);
      return true;
    }

    LLVM_DUMP_METHOD void dump() const { dumpToStream(llvm::errs()); }
    LLVM_DUMP_METHOD void dumpToStream(llvm::raw_ostream &out) const {
      out << "Owners: {\n";
      for (const MemRegion *Owner : Owners) {
        out << "  ";
        Owner->dumpToStream(out);
        out << ",\n";
      }
      out << "}\n";
    }
  };

protected:
  OwnerSet getOwnersAtNode(const ExplodedNode *N) {
    OwnerSet Ret;

    ProgramStateRef State = N->getState();
    OwnershipBindingsHandler Handler{Sym, Ret};
    State->getStateManager().getStoreManager().iterBindings(State->getStore(),
                                                            Handler);
    return Ret;
  }

  LLVM_DUMP_METHOD static std::string
  getFunctionName(const ExplodedNode *CallEnterN) {
    if (const CallExpr *CE = llvm::dyn_cast_or_null<CallExpr>(
            CallEnterN->getLocationAs<CallEnter>()->getCallExpr()))
      if (const FunctionDecl *FD = CE->getDirectCallee())
        return FD->getQualifiedNameAsString();
    return "";
  }

  /// Syntactically checks whether the callee is a deallocating function. Since
  /// we have no path-sensitive information on this call (we would need a
  /// CallEvent instead of a CallExpr for that), its possible that a
  /// deallocation function was called indirectly through a function pointer,
  /// but we are not able to tell, so this is a best effort analysis.
  /// See namespace `memory_passed_to_fn_call_free_through_fn_ptr` in
  /// clang/test/Analysis/NewDeleteLeaks.cpp.
  bool isFreeingCallAsWritten(const CallExpr &Call) const {
    if (Checker.FreeingMemFnMap.lookupAsWritten(Call) ||
        Checker.ReallocatingMemFnMap.lookupAsWritten(Call))
      return true;

    if (const auto *Func =
            llvm::dyn_cast_or_null<FunctionDecl>(Call.getCalleeDecl()))
      return MallocChecker::isFreeingOwnershipAttrCall(Func);

    return false;
  }

  /// Heuristically guess whether the callee intended to free memory. This is
  /// done syntactically, because we are trying to argue about alternative
  /// paths of execution, and as a consequence we don't have path-sensitive
  /// information.
  bool doesFnIntendToHandleOwnership(const Decl *Callee, ASTContext &ACtx) {
    using namespace clang::ast_matchers;
    const FunctionDecl *FD = dyn_cast<FunctionDecl>(Callee);

    // Given that the stack frame was entered, the body should always be
    // theoretically obtainable. In case of body farms, the synthesized body
    // is not attached to declaration, thus triggering the '!FD->hasBody()'
    // branch. That said, would a synthesized body ever intend to handle
    // ownership? As of today they don't. And if they did, how would we
    // put notes inside it, given that it doesn't match any source locations?
    if (!FD || !FD->hasBody())
      return false;

    auto Matches = match(findAll(stmt(anyOf(cxxDeleteExpr().bind("delete"),
                                            callExpr().bind("call")))),
                         *FD->getBody(), ACtx);
    for (BoundNodes Match : Matches) {
      if (Match.getNodeAs<CXXDeleteExpr>("delete"))
        return true;

      if (const auto *Call = Match.getNodeAs<CallExpr>("call"))
        if (isFreeingCallAsWritten(*Call))
          return true;
    }
    // TODO: Ownership might change with an attempt to store the allocated
    // memory, not only through deallocation. Check for attempted stores as
    // well.
    return false;
  }

  bool wasModifiedInFunction(const ExplodedNode *CallEnterN,
                             const ExplodedNode *CallExitEndN) override {
    if (!doesFnIntendToHandleOwnership(
            CallExitEndN->getFirstPred()->getLocationContext()->getDecl(),
            CallExitEndN->getState()->getAnalysisManager().getASTContext()))
      return true;

    if (CallEnterN->getState()->get<RegionState>(Sym) !=
        CallExitEndN->getState()->get<RegionState>(Sym))
      return true;

    OwnerSet CurrOwners = getOwnersAtNode(CallEnterN);
    OwnerSet ExitOwners = getOwnersAtNode(CallExitEndN);

    // Owners in the current set may be purged from the analyzer later on.
    // If a variable is dead (is not referenced directly or indirectly after
    // some point), it will be removed from the Store before the end of its
    // actual lifetime.
    // This means that if the ownership status didn't change, CurrOwners
    // must be a superset of, but not necessarily equal to ExitOwners.
    return !llvm::set_is_subset(ExitOwners, CurrOwners);
  }

  static PathDiagnosticPieceRef emitNote(const ExplodedNode *N) {
    PathDiagnosticLocation L = PathDiagnosticLocation::create(
        N->getLocation(),
        N->getState()->getStateManager().getContext().getSourceManager());
    return std::make_shared<PathDiagnosticEventPiece>(
        L, "Returning without deallocating memory or storing the pointer for "
           "later deallocation");
  }

  PathDiagnosticPieceRef
  maybeEmitNoteForObjCSelf(PathSensitiveBugReport &R,
                           const ObjCMethodCall &Call,
                           const ExplodedNode *N) override {
    // TODO: Implement.
    return nullptr;
  }

  PathDiagnosticPieceRef
  maybeEmitNoteForCXXThis(PathSensitiveBugReport &R,
                          const CXXConstructorCall &Call,
                          const ExplodedNode *N) override {
    // TODO: Implement.
    return nullptr;
  }

  PathDiagnosticPieceRef
  maybeEmitNoteForParameters(PathSensitiveBugReport &R, const CallEvent &Call,
                             const ExplodedNode *N) override {
    // TODO: Factor the logic of "what constitutes as an entity being passed
    // into a function call" out by reusing the code in
    // NoStoreFuncVisitor::maybeEmitNoteForParameters, maybe by incorporating
    // the printing technology in UninitializedObject's FieldChainInfo.
    ArrayRef<ParmVarDecl *> Parameters = Call.parameters();
    for (unsigned I = 0; I < Call.getNumArgs() && I < Parameters.size(); ++I) {
      SVal V = Call.getArgSVal(I);
      if (V.getAsSymbol() == Sym)
        return emitNote(N);
    }
    return nullptr;
  }

public:
  NoOwnershipChangeVisitor(SymbolRef Sym, const MallocChecker *Checker)
      : NoStateChangeFuncVisitor(bugreporter::TrackingKind::Thorough), Sym(Sym),
        Checker(*Checker) {}

  void Profile(llvm::FoldingSetNodeID &ID) const override {
    static int Tag = 0;
    ID.AddPointer(&Tag);
    ID.AddPointer(Sym);
  }
};

} // end anonymous namespace

//===----------------------------------------------------------------------===//
// Definition of MallocBugVisitor.
//===----------------------------------------------------------------------===//

namespace {
/// The bug visitor which allows us to print extra diagnostics along the
/// BugReport path. For example, showing the allocation site of the leaked
/// region.
class MallocBugVisitor final : public BugReporterVisitor {
protected:
  enum NotificationMode { Normal, ReallocationFailed };

  // The allocated region symbol tracked by the main analysis.
  SymbolRef Sym;

  // The mode we are in, i.e. what kind of diagnostics will be emitted.
  NotificationMode Mode;

  // A symbol from when the primary region should have been reallocated.
  SymbolRef FailedReallocSymbol;

  // A C++ destructor stack frame in which memory was released. Used for
  // miscellaneous false positive suppression.
  const StackFrameContext *ReleaseDestructorLC;

  bool IsLeak;

public:
  MallocBugVisitor(SymbolRef S, bool isLeak = false)
      : Sym(S), Mode(Normal), FailedReallocSymbol(nullptr),
        ReleaseDestructorLC(nullptr), IsLeak(isLeak) {}

  static void *getTag() {
    static int Tag = 0;
    return &Tag;
  }

  void Profile(llvm::FoldingSetNodeID &ID) const override {
    ID.AddPointer(getTag());
    ID.AddPointer(Sym);
  }

  /// Did not track -> allocated. Other state (released) -> allocated.
  static inline bool isAllocated(const RefState *RSCurr, const RefState *RSPrev,
                                 const Stmt *Stmt) {
    return (isa_and_nonnull<CallExpr, CXXNewExpr>(Stmt) &&
            (RSCurr &&
             (RSCurr->isAllocated() || RSCurr->isAllocatedOfSizeZero())) &&
            (!RSPrev ||
             !(RSPrev->isAllocated() || RSPrev->isAllocatedOfSizeZero())));
  }

  /// Did not track -> released. Other state (allocated) -> released.
  /// The statement associated with the release might be missing.
  static inline bool isReleased(const RefState *RSCurr, const RefState *RSPrev,
                                const Stmt *Stmt) {
    bool IsReleased =
        (RSCurr && RSCurr->isReleased()) && (!RSPrev || !RSPrev->isReleased());
    assert(!IsReleased || (isa_and_nonnull<CallExpr, CXXDeleteExpr>(Stmt)) ||
           (!Stmt && RSCurr->getAllocationFamily() == AF_InnerBuffer));
    return IsReleased;
  }

  /// Did not track -> relinquished. Other state (allocated) -> relinquished.
  static inline bool isRelinquished(const RefState *RSCurr,
                                    const RefState *RSPrev, const Stmt *Stmt) {
    return (
        isa_and_nonnull<CallExpr, ObjCMessageExpr, ObjCPropertyRefExpr>(Stmt) &&
        (RSCurr && RSCurr->isRelinquished()) &&
        (!RSPrev || !RSPrev->isRelinquished()));
  }

  /// If the expression is not a call, and the state change is
  /// released -> allocated, it must be the realloc return value
  /// check. If we have to handle more cases here, it might be cleaner just
  /// to track this extra bit in the state itself.
  static inline bool hasReallocFailed(const RefState *RSCurr,
                                      const RefState *RSPrev,
                                      const Stmt *Stmt) {
    return ((!isa_and_nonnull<CallExpr>(Stmt)) &&
            (RSCurr &&
             (RSCurr->isAllocated() || RSCurr->isAllocatedOfSizeZero())) &&
            (RSPrev &&
             !(RSPrev->isAllocated() || RSPrev->isAllocatedOfSizeZero())));
  }

  PathDiagnosticPieceRef VisitNode(const ExplodedNode *N,
                                   BugReporterContext &BRC,
                                   PathSensitiveBugReport &BR) override;

  PathDiagnosticPieceRef getEndPath(BugReporterContext &BRC,
                                    const ExplodedNode *EndPathNode,
                                    PathSensitiveBugReport &BR) override {
    if (!IsLeak)
      return nullptr;

    PathDiagnosticLocation L = BR.getLocation();
    // Do not add the statement itself as a range in case of leak.
    return std::make_shared<PathDiagnosticEventPiece>(L, BR.getDescription(),
                                                      false);
  }

private:
  class StackHintGeneratorForReallocationFailed
      : public StackHintGeneratorForSymbol {
  public:
    StackHintGeneratorForReallocationFailed(SymbolRef S, StringRef M)
        : StackHintGeneratorForSymbol(S, M) {}

    std::string getMessageForArg(const Expr *ArgE, unsigned ArgIndex) override {
      // Printed parameters start at 1, not 0.
      ++ArgIndex;

      SmallString<200> buf;
      llvm::raw_svector_ostream os(buf);

      os << "Reallocation of " << ArgIndex << llvm::getOrdinalSuffix(ArgIndex)
         << " parameter failed";

      return std::string(os.str());
    }

    std::string getMessageForReturn(const CallExpr *CallExpr) override {
      return "Reallocation of returned value failed";
    }
  };
};
} // end anonymous namespace

// A map from the freed symbol to the symbol representing the return value of
// the free function.
REGISTER_MAP_WITH_PROGRAMSTATE(FreeReturnValue, SymbolRef, SymbolRef)

namespace {
class StopTrackingCallback final : public SymbolVisitor {
  ProgramStateRef state;

public:
  StopTrackingCallback(ProgramStateRef st) : state(std::move(st)) {}
  ProgramStateRef getState() const { return state; }

  bool VisitSymbol(SymbolRef sym) override {
    state = state->remove<RegionState>(sym);
    return true;
  }
};
} // end anonymous namespace

static bool isStandardNewDelete(const FunctionDecl *FD) {
  if (!FD)
    return false;

  OverloadedOperatorKind Kind = FD->getOverloadedOperator();
  if (Kind != OO_New && Kind != OO_Array_New && Kind != OO_Delete &&
      Kind != OO_Array_Delete)
    return false;

  // This is standard if and only if it's not defined in a user file.
  SourceLocation L = FD->getLocation();
  // If the header for operator delete is not included, it's still defined
  // in an invalid source location. Check to make sure we don't crash.
  return !L.isValid() ||
         FD->getASTContext().getSourceManager().isInSystemHeader(L);
}

//===----------------------------------------------------------------------===//
// Methods of MallocChecker and MallocBugVisitor.
//===----------------------------------------------------------------------===//

bool MallocChecker::isFreeingOwnershipAttrCall(const FunctionDecl *Func) {
  if (Func->hasAttrs()) {
    for (const auto *I : Func->specific_attrs<OwnershipAttr>()) {
      OwnershipAttr::OwnershipKind OwnKind = I->getOwnKind();
      if (OwnKind == OwnershipAttr::Takes || OwnKind == OwnershipAttr::Holds)
        return true;
    }
  }
  return false;
}

bool MallocChecker::isFreeingCall(const CallEvent &Call) const {
  if (FreeingMemFnMap.lookup(Call) || ReallocatingMemFnMap.lookup(Call))
    return true;

  if (const auto *Func = dyn_cast_or_null<FunctionDecl>(Call.getDecl()))
    return isFreeingOwnershipAttrCall(Func);

  return false;
}

bool MallocChecker::isMemCall(const CallEvent &Call) const {
  if (FreeingMemFnMap.lookup(Call) || AllocatingMemFnMap.lookup(Call) ||
      ReallocatingMemFnMap.lookup(Call))
    return true;

  if (!ShouldIncludeOwnershipAnnotatedFunctions)
    return false;

  const auto *Func = dyn_cast<FunctionDecl>(Call.getDecl());
  return Func && Func->hasAttr<OwnershipAttr>();
}

llvm::Optional<ProgramStateRef>
MallocChecker::performKernelMalloc(const CallEvent &Call, CheckerContext &C,
                                   const ProgramStateRef &State) const {
  // 3-argument malloc(), as commonly used in {Free,Net,Open}BSD Kernels:
  //
  // void *malloc(unsigned long size, struct malloc_type *mtp, int flags);
  //
  // One of the possible flags is M_ZERO, which means 'give me back an
  // allocation which is already zeroed', like calloc.

  // 2-argument kmalloc(), as used in the Linux kernel:
  //
  // void *kmalloc(size_t size, gfp_t flags);
  //
  // Has the similar flag value __GFP_ZERO.

  // This logic is largely cloned from O_CREAT in UnixAPIChecker, maybe some
  // code could be shared.

  ASTContext &Ctx = C.getASTContext();
  llvm::Triple::OSType OS = Ctx.getTargetInfo().getTriple().getOS();

  if (!KernelZeroFlagVal) {
    if (OS == llvm::Triple::FreeBSD)
      KernelZeroFlagVal = 0x0100;
    else if (OS == llvm::Triple::NetBSD)
      KernelZeroFlagVal = 0x0002;
    else if (OS == llvm::Triple::OpenBSD)
      KernelZeroFlagVal = 0x0008;
    else if (OS == llvm::Triple::Linux)
      // __GFP_ZERO
      KernelZeroFlagVal = 0x8000;
    else
      // FIXME: We need a more general way of getting the M_ZERO value.
      // See also: O_CREAT in UnixAPIChecker.cpp.

      // Fall back to normal malloc behavior on platforms where we don't
      // know M_ZERO.
      return std::nullopt;
  }

  // We treat the last argument as the flags argument, and callers fall-back to
  // normal malloc on a None return. This works for the FreeBSD kernel malloc
  // as well as Linux kmalloc.
  if (Call.getNumArgs() < 2)
    return std::nullopt;

  const Expr *FlagsEx = Call.getArgExpr(Call.getNumArgs() - 1);
  const SVal V = C.getSVal(FlagsEx);
  if (!isa<NonLoc>(V)) {
    // The case where 'V' can be a location can only be due to a bad header,
    // so in this case bail out.
    return std::nullopt;
  }

  NonLoc Flags = V.castAs<NonLoc>();
  NonLoc ZeroFlag = C.getSValBuilder()
                        .makeIntVal(*KernelZeroFlagVal, FlagsEx->getType())
                        .castAs<NonLoc>();
  SVal MaskedFlagsUC = C.getSValBuilder().evalBinOpNN(State, BO_And,
                                                      Flags, ZeroFlag,
                                                      FlagsEx->getType());
  if (MaskedFlagsUC.isUnknownOrUndef())
    return std::nullopt;
  DefinedSVal MaskedFlags = MaskedFlagsUC.castAs<DefinedSVal>();

  // Check if maskedFlags is non-zero.
  ProgramStateRef TrueState, FalseState;
  std::tie(TrueState, FalseState) = State->assume(MaskedFlags);

  // If M_ZERO is set, treat this like calloc (initialized).
  if (TrueState && !FalseState) {
    SVal ZeroVal = C.getSValBuilder().makeZeroVal(Ctx.CharTy);
    return MallocMemAux(C, Call, Call.getArgExpr(0), ZeroVal, TrueState,
                        AF_Malloc);
  }

  return std::nullopt;
}

SVal MallocChecker::evalMulForBufferSize(CheckerContext &C, const Expr *Blocks,
                                         const Expr *BlockBytes) {
  SValBuilder &SB = C.getSValBuilder();
  SVal BlocksVal = C.getSVal(Blocks);
  SVal BlockBytesVal = C.getSVal(BlockBytes);
  ProgramStateRef State = C.getState();
  SVal TotalSize = SB.evalBinOp(State, BO_Mul, BlocksVal, BlockBytesVal,
                                SB.getContext().getSizeType());
  return TotalSize;
}

void MallocChecker::checkBasicAlloc(const CallEvent &Call,
                                    CheckerContext &C) const {
  ProgramStateRef State = C.getState();
  State = MallocMemAux(C, Call, Call.getArgExpr(0), UndefinedVal(), State,
                       AF_Malloc);
  State = ProcessZeroAllocCheck(Call, 0, State);
  C.addTransition(State);
}

void MallocChecker::checkKernelMalloc(const CallEvent &Call,
                                      CheckerContext &C) const {
  ProgramStateRef State = C.getState();
  llvm::Optional<ProgramStateRef> MaybeState =
      performKernelMalloc(Call, C, State);
  if (MaybeState)
    State = MaybeState.value();
  else
    State = MallocMemAux(C, Call, Call.getArgExpr(0), UndefinedVal(), State,
                         AF_Malloc);
  C.addTransition(State);
}

static bool isStandardRealloc(const CallEvent &Call) {
  const FunctionDecl *FD = dyn_cast<FunctionDecl>(Call.getDecl());
  assert(FD);
  ASTContext &AC = FD->getASTContext();

  if (isa<CXXMethodDecl>(FD))
    return false;

  return FD->getDeclaredReturnType().getDesugaredType(AC) == AC.VoidPtrTy &&
         FD->getParamDecl(0)->getType().getDesugaredType(AC) == AC.VoidPtrTy &&
         FD->getParamDecl(1)->getType().getDesugaredType(AC) ==
             AC.getSizeType();
}

static bool isGRealloc(const CallEvent &Call) {
  const FunctionDecl *FD = dyn_cast<FunctionDecl>(Call.getDecl());
  assert(FD);
  ASTContext &AC = FD->getASTContext();

  if (isa<CXXMethodDecl>(FD))
    return false;

  return FD->getDeclaredReturnType().getDesugaredType(AC) == AC.VoidPtrTy &&
         FD->getParamDecl(0)->getType().getDesugaredType(AC) == AC.VoidPtrTy &&
         FD->getParamDecl(1)->getType().getDesugaredType(AC) ==
             AC.UnsignedLongTy;
}

void MallocChecker::checkRealloc(const CallEvent &Call, CheckerContext &C,
                                 bool ShouldFreeOnFail) const {
  // HACK: CallDescription currently recognizes non-standard realloc functions
  // as standard because it doesn't check the type, or wether its a non-method
  // function. This should be solved by making CallDescription smarter.
  // Mind that this came from a bug report, and all other functions suffer from
  // this.
  // https://bugs.llvm.org/show_bug.cgi?id=46253
  if (!isStandardRealloc(Call) && !isGRealloc(Call))
    return;
  ProgramStateRef State = C.getState();
  State = ReallocMemAux(C, Call, ShouldFreeOnFail, State, AF_Malloc);
  State = ProcessZeroAllocCheck(Call, 1, State);
  C.addTransition(State);
}

void MallocChecker::checkCalloc(const CallEvent &Call,
                                CheckerContext &C) const {
  ProgramStateRef State = C.getState();
  State = CallocMem(C, Call, State);
  State = ProcessZeroAllocCheck(Call, 0, State);
  State = ProcessZeroAllocCheck(Call, 1, State);
  C.addTransition(State);
}

void MallocChecker::checkFree(const CallEvent &Call, CheckerContext &C) const {
  ProgramStateRef State = C.getState();
  bool IsKnownToBeAllocatedMemory = false;
  if (suppressDeallocationsInSuspiciousContexts(Call, C))
    return;
  State = FreeMemAux(C, Call, State, 0, false, IsKnownToBeAllocatedMemory,
                     AF_Malloc);
  C.addTransition(State);
}

void MallocChecker::checkAlloca(const CallEvent &Call,
                                CheckerContext &C) const {
  ProgramStateRef State = C.getState();
  State = MallocMemAux(C, Call, Call.getArgExpr(0), UndefinedVal(), State,
                       AF_Alloca);
  State = ProcessZeroAllocCheck(Call, 0, State);
  C.addTransition(State);
}

void MallocChecker::checkStrdup(const CallEvent &Call,
                                CheckerContext &C) const {
  ProgramStateRef State = C.getState();
  const auto *CE = dyn_cast_or_null<CallExpr>(Call.getOriginExpr());
  if (!CE)
    return;
  State = MallocUpdateRefState(C, CE, State, AF_Malloc);

  C.addTransition(State);
}

void MallocChecker::checkIfNameIndex(const CallEvent &Call,
                                     CheckerContext &C) const {
  ProgramStateRef State = C.getState();
  // Should we model this differently? We can allocate a fixed number of
  // elements with zeros in the last one.
  State =
      MallocMemAux(C, Call, UnknownVal(), UnknownVal(), State, AF_IfNameIndex);

  C.addTransition(State);
}

void MallocChecker::checkIfFreeNameIndex(const CallEvent &Call,
                                         CheckerContext &C) const {
  ProgramStateRef State = C.getState();
  bool IsKnownToBeAllocatedMemory = false;
  State = FreeMemAux(C, Call, State, 0, false, IsKnownToBeAllocatedMemory,
                     AF_IfNameIndex);
  C.addTransition(State);
}

void MallocChecker::checkCXXNewOrCXXDelete(const CallEvent &Call,
                                           CheckerContext &C) const {
  ProgramStateRef State = C.getState();
  bool IsKnownToBeAllocatedMemory = false;
  const auto *CE = dyn_cast_or_null<CallExpr>(Call.getOriginExpr());
  if (!CE)
    return;

  assert(isStandardNewDelete(Call));

  // Process direct calls to operator new/new[]/delete/delete[] functions
  // as distinct from new/new[]/delete/delete[] expressions that are
  // processed by the checkPostStmt callbacks for CXXNewExpr and
  // CXXDeleteExpr.
  const FunctionDecl *FD = C.getCalleeDecl(CE);
  switch (FD->getOverloadedOperator()) {
  case OO_New:
    State =
        MallocMemAux(C, Call, CE->getArg(0), UndefinedVal(), State, AF_CXXNew);
    State = ProcessZeroAllocCheck(Call, 0, State);
    break;
  case OO_Array_New:
    State = MallocMemAux(C, Call, CE->getArg(0), UndefinedVal(), State,
                         AF_CXXNewArray);
    State = ProcessZeroAllocCheck(Call, 0, State);
    break;
  case OO_Delete:
    State = FreeMemAux(C, Call, State, 0, false, IsKnownToBeAllocatedMemory,
                       AF_CXXNew);
    break;
  case OO_Array_Delete:
    State = FreeMemAux(C, Call, State, 0, false, IsKnownToBeAllocatedMemory,
                       AF_CXXNewArray);
    break;
  default:
    llvm_unreachable("not a new/delete operator");
  }

  C.addTransition(State);
}

void MallocChecker::checkGMalloc0(const CallEvent &Call,
                                  CheckerContext &C) const {
  ProgramStateRef State = C.getState();
  SValBuilder &svalBuilder = C.getSValBuilder();
  SVal zeroVal = svalBuilder.makeZeroVal(svalBuilder.getContext().CharTy);
  State = MallocMemAux(C, Call, Call.getArgExpr(0), zeroVal, State, AF_Malloc);
  State = ProcessZeroAllocCheck(Call, 0, State);
  C.addTransition(State);
}

void MallocChecker::checkGMemdup(const CallEvent &Call,
                                 CheckerContext &C) const {
  ProgramStateRef State = C.getState();
  State =
      MallocMemAux(C, Call, Call.getArgExpr(1), UnknownVal(), State, AF_Malloc);
  State = ProcessZeroAllocCheck(Call, 1, State);
  C.addTransition(State);
}

void MallocChecker::checkGMallocN(const CallEvent &Call,
                                  CheckerContext &C) const {
  ProgramStateRef State = C.getState();
  SVal Init = UndefinedVal();
  SVal TotalSize = evalMulForBufferSize(C, Call.getArgExpr(0), Call.getArgExpr(1));
  State = MallocMemAux(C, Call, TotalSize, Init, State, AF_Malloc);
  State = ProcessZeroAllocCheck(Call, 0, State);
  State = ProcessZeroAllocCheck(Call, 1, State);
  C.addTransition(State);
}

void MallocChecker::checkGMallocN0(const CallEvent &Call,
                                   CheckerContext &C) const {
  ProgramStateRef State = C.getState();
  SValBuilder &SB = C.getSValBuilder();
  SVal Init = SB.makeZeroVal(SB.getContext().CharTy);
  SVal TotalSize = evalMulForBufferSize(C, Call.getArgExpr(0), Call.getArgExpr(1));
  State = MallocMemAux(C, Call, TotalSize, Init, State, AF_Malloc);
  State = ProcessZeroAllocCheck(Call, 0, State);
  State = ProcessZeroAllocCheck(Call, 1, State);
  C.addTransition(State);
}

void MallocChecker::checkReallocN(const CallEvent &Call,
                                  CheckerContext &C) const {
  ProgramStateRef State = C.getState();
  State = ReallocMemAux(C, Call, /*ShouldFreeOnFail=*/false, State, AF_Malloc,
                        /*SuffixWithN=*/true);
  State = ProcessZeroAllocCheck(Call, 1, State);
  State = ProcessZeroAllocCheck(Call, 2, State);
  C.addTransition(State);
}

void MallocChecker::checkOwnershipAttr(const CallEvent &Call,
                                       CheckerContext &C) const {
  ProgramStateRef State = C.getState();
  const auto *CE = dyn_cast_or_null<CallExpr>(Call.getOriginExpr());
  if (!CE)
    return;
  const FunctionDecl *FD = C.getCalleeDecl(CE);
  if (!FD)
    return;
  if (ShouldIncludeOwnershipAnnotatedFunctions ||
      ChecksEnabled[CK_MismatchedDeallocatorChecker]) {
    // Check all the attributes, if there are any.
    // There can be multiple of these attributes.
    if (FD->hasAttrs())
      for (const auto *I : FD->specific_attrs<OwnershipAttr>()) {
        switch (I->getOwnKind()) {
        case OwnershipAttr::Returns:
          State = MallocMemReturnsAttr(C, Call, I, State);
          break;
        case OwnershipAttr::Takes:
        case OwnershipAttr::Holds:
          State = FreeMemAttr(C, Call, I, State);
          break;
        }
      }
  }
  C.addTransition(State);
}

void MallocChecker::checkPostCall(const CallEvent &Call,
                                  CheckerContext &C) const {
  if (C.wasInlined)
    return;
  if (!Call.getOriginExpr())
    return;

  ProgramStateRef State = C.getState();

  if (const CheckFn *Callback = FreeingMemFnMap.lookup(Call)) {
    (*Callback)(this, Call, C);
    return;
  }

  if (const CheckFn *Callback = AllocatingMemFnMap.lookup(Call)) {
    (*Callback)(this, Call, C);
    return;
  }

  if (const CheckFn *Callback = ReallocatingMemFnMap.lookup(Call)) {
    (*Callback)(this, Call, C);
    return;
  }

  if (isStandardNewDelete(Call)) {
    checkCXXNewOrCXXDelete(Call, C);
    return;
  }

  checkOwnershipAttr(Call, C);
}

// Performs a 0-sized allocations check.
ProgramStateRef MallocChecker::ProcessZeroAllocCheck(
    const CallEvent &Call, const unsigned IndexOfSizeArg, ProgramStateRef State,
    Optional<SVal> RetVal) {
  if (!State)
    return nullptr;

  if (!RetVal)
    RetVal = Call.getReturnValue();

  const Expr *Arg = nullptr;

  if (const CallExpr *CE = dyn_cast<CallExpr>(Call.getOriginExpr())) {
    Arg = CE->getArg(IndexOfSizeArg);
  } else if (const CXXNewExpr *NE =
                 dyn_cast<CXXNewExpr>(Call.getOriginExpr())) {
    if (NE->isArray()) {
      Arg = *NE->getArraySize();
    } else {
      return State;
    }
  } else
    llvm_unreachable("not a CallExpr or CXXNewExpr");

  assert(Arg);

  auto DefArgVal =
      State->getSVal(Arg, Call.getLocationContext()).getAs<DefinedSVal>();

  if (!DefArgVal)
    return State;

  // Check if the allocation size is 0.
  ProgramStateRef TrueState, FalseState;
  SValBuilder &SvalBuilder = State->getStateManager().getSValBuilder();
  DefinedSVal Zero =
      SvalBuilder.makeZeroVal(Arg->getType()).castAs<DefinedSVal>();

  std::tie(TrueState, FalseState) =
      State->assume(SvalBuilder.evalEQ(State, *DefArgVal, Zero));

  if (TrueState && !FalseState) {
    SymbolRef Sym = RetVal->getAsLocSymbol();
    if (!Sym)
      return State;

    const RefState *RS = State->get<RegionState>(Sym);
    if (RS) {
      if (RS->isAllocated())
        return TrueState->set<RegionState>(Sym,
                                          RefState::getAllocatedOfSizeZero(RS));
      else
        return State;
    } else {
      // Case of zero-size realloc. Historically 'realloc(ptr, 0)' is treated as
      // 'free(ptr)' and the returned value from 'realloc(ptr, 0)' is not
      // tracked. Add zero-reallocated Sym to the state to catch references
      // to zero-allocated memory.
      return TrueState->add<ReallocSizeZeroSymbols>(Sym);
    }
  }

  // Assume the value is non-zero going forward.
  assert(FalseState);
  return FalseState;
}

static QualType getDeepPointeeType(QualType T) {
  QualType Result = T, PointeeType = T->getPointeeType();
  while (!PointeeType.isNull()) {
    Result = PointeeType;
    PointeeType = PointeeType->getPointeeType();
  }
  return Result;
}

/// \returns true if the constructor invoked by \p NE has an argument of a
/// pointer/reference to a record type.
static bool hasNonTrivialConstructorCall(const CXXNewExpr *NE) {

  const CXXConstructExpr *ConstructE = NE->getConstructExpr();
  if (!ConstructE)
    return false;

  if (!NE->getAllocatedType()->getAsCXXRecordDecl())
    return false;

  const CXXConstructorDecl *CtorD = ConstructE->getConstructor();

  // Iterate over the constructor parameters.
  for (const auto *CtorParam : CtorD->parameters()) {

    QualType CtorParamPointeeT = CtorParam->getType()->getPointeeType();
    if (CtorParamPointeeT.isNull())
      continue;

    CtorParamPointeeT = getDeepPointeeType(CtorParamPointeeT);

    if (CtorParamPointeeT->getAsCXXRecordDecl())
      return true;
  }

  return false;
}

ProgramStateRef
MallocChecker::processNewAllocation(const CXXAllocatorCall &Call,
                                    CheckerContext &C,
                                    AllocationFamily Family) const {
  if (!isStandardNewDelete(Call))
    return nullptr;

  const CXXNewExpr *NE = Call.getOriginExpr();
  const ParentMap &PM = C.getLocationContext()->getParentMap();
  ProgramStateRef State = C.getState();

  // Non-trivial constructors have a chance to escape 'this', but marking all
  // invocations of trivial constructors as escaped would cause too great of
  // reduction of true positives, so let's just do that for constructors that
  // have an argument of a pointer-to-record type.
  if (!PM.isConsumedExpr(NE) && hasNonTrivialConstructorCall(NE))
    return State;

  // The return value from operator new is bound to a specified initialization
  // value (if any) and we don't want to loose this value. So we call
  // MallocUpdateRefState() instead of MallocMemAux() which breaks the
  // existing binding.
  SVal Target = Call.getObjectUnderConstruction();
  State = MallocUpdateRefState(C, NE, State, Family, Target);
  State = ProcessZeroAllocCheck(Call, 0, State, Target);
  return State;
}

void MallocChecker::checkNewAllocator(const CXXAllocatorCall &Call,
                                      CheckerContext &C) const {
  if (!C.wasInlined) {
    ProgramStateRef State = processNewAllocation(
        Call, C,
        (Call.getOriginExpr()->isArray() ? AF_CXXNewArray : AF_CXXNew));
    C.addTransition(State);
  }
}

static bool isKnownDeallocObjCMethodName(const ObjCMethodCall &Call) {
  // If the first selector piece is one of the names below, assume that the
  // object takes ownership of the memory, promising to eventually deallocate it
  // with free().
  // Ex:  [NSData dataWithBytesNoCopy:bytes length:10];
  // (...unless a 'freeWhenDone' parameter is false, but that's checked later.)
  StringRef FirstSlot = Call.getSelector().getNameForSlot(0);
  return FirstSlot == "dataWithBytesNoCopy" ||
         FirstSlot == "initWithBytesNoCopy" ||
         FirstSlot == "initWithCharactersNoCopy";
}

static std::optional<bool> getFreeWhenDoneArg(const ObjCMethodCall &Call) {
  Selector S = Call.getSelector();

  // FIXME: We should not rely on fully-constrained symbols being folded.
  for (unsigned i = 1; i < S.getNumArgs(); ++i)
    if (S.getNameForSlot(i).equals("freeWhenDone"))
      return !Call.getArgSVal(i).isZeroConstant();

  return std::nullopt;
}

void MallocChecker::checkPostObjCMessage(const ObjCMethodCall &Call,
                                         CheckerContext &C) const {
  if (C.wasInlined)
    return;

  if (!isKnownDeallocObjCMethodName(Call))
    return;

  if (std::optional<bool> FreeWhenDone = getFreeWhenDoneArg(Call))
    if (!*FreeWhenDone)
      return;

  if (Call.hasNonZeroCallbackArg())
    return;

  bool IsKnownToBeAllocatedMemory;
  ProgramStateRef State =
      FreeMemAux(C, Call.getArgExpr(0), Call, C.getState(),
                 /*Hold=*/true, IsKnownToBeAllocatedMemory, AF_Malloc,
                 /*ReturnsNullOnFailure=*/true);

  C.addTransition(State);
}

ProgramStateRef
MallocChecker::MallocMemReturnsAttr(CheckerContext &C, const CallEvent &Call,
                                    const OwnershipAttr *Att,
                                    ProgramStateRef State) const {
  if (!State)
    return nullptr;

  if (Att->getModule()->getName() != "malloc")
    return nullptr;

  OwnershipAttr::args_iterator I = Att->args_begin(), E = Att->args_end();
  if (I != E) {
    return MallocMemAux(C, Call, Call.getArgExpr(I->getASTIndex()),
                        UndefinedVal(), State, AF_Malloc);
  }
  return MallocMemAux(C, Call, UnknownVal(), UndefinedVal(), State, AF_Malloc);
}

ProgramStateRef MallocChecker::MallocMemAux(CheckerContext &C,
                                            const CallEvent &Call,
                                            const Expr *SizeEx, SVal Init,
                                            ProgramStateRef State,
                                            AllocationFamily Family) {
  if (!State)
    return nullptr;

  assert(SizeEx);
  return MallocMemAux(C, Call, C.getSVal(SizeEx), Init, State, Family);
}

ProgramStateRef MallocChecker::MallocMemAux(CheckerContext &C,
                                            const CallEvent &Call, SVal Size,
                                            SVal Init, ProgramStateRef State,
                                            AllocationFamily Family) {
  if (!State)
    return nullptr;

  const Expr *CE = Call.getOriginExpr();

  // We expect the malloc functions to return a pointer.
  if (!Loc::isLocType(CE->getType()))
    return nullptr;

  // Bind the return value to the symbolic value from the heap region.
  // TODO: We could rewrite post visit to eval call; 'malloc' does not have
  // side effects other than what we model here.
  unsigned Count = C.blockCount();
  SValBuilder &svalBuilder = C.getSValBuilder();
  const LocationContext *LCtx = C.getPredecessor()->getLocationContext();
  DefinedSVal RetVal = svalBuilder.getConjuredHeapSymbolVal(CE, LCtx, Count)
      .castAs<DefinedSVal>();
  State = State->BindExpr(CE, C.getLocationContext(), RetVal);

  // Fill the region with the initialization value.
  State = State->bindDefaultInitial(RetVal, Init, LCtx);

  // If Size is somehow undefined at this point, this line prevents a crash.
  if (Size.isUndef())
    Size = UnknownVal();

  // Set the region's extent.
  State = setDynamicExtent(State, RetVal.getAsRegion(),
                           Size.castAs<DefinedOrUnknownSVal>(), svalBuilder);

  return MallocUpdateRefState(C, CE, State, Family);
}

static ProgramStateRef MallocUpdateRefState(CheckerContext &C, const Expr *E,
                                            ProgramStateRef State,
                                            AllocationFamily Family,
                                            Optional<SVal> RetVal) {
  if (!State)
    return nullptr;

  // Get the return value.
  if (!RetVal)
    RetVal = C.getSVal(E);

  // We expect the malloc functions to return a pointer.
  if (!RetVal->getAs<Loc>())
    return nullptr;

  SymbolRef Sym = RetVal->getAsLocSymbol();
  // This is a return value of a function that was not inlined, such as malloc()
  // or new(). We've checked that in the caller. Therefore, it must be a symbol.
  assert(Sym);

  // Set the symbol's state to Allocated.
  return State->set<RegionState>(Sym, RefState::getAllocated(Family, E));
}

ProgramStateRef MallocChecker::FreeMemAttr(CheckerContext &C,
                                           const CallEvent &Call,
                                           const OwnershipAttr *Att,
                                           ProgramStateRef State) const {
  if (!State)
    return nullptr;

  if (Att->getModule()->getName() != "malloc")
    return nullptr;

  bool IsKnownToBeAllocated = false;

  for (const auto &Arg : Att->args()) {
    ProgramStateRef StateI =
        FreeMemAux(C, Call, State, Arg.getASTIndex(),
                   Att->getOwnKind() == OwnershipAttr::Holds,
                   IsKnownToBeAllocated, AF_Malloc);
    if (StateI)
      State = StateI;
  }
  return State;
}

ProgramStateRef MallocChecker::FreeMemAux(CheckerContext &C,
                                          const CallEvent &Call,
                                          ProgramStateRef State, unsigned Num,
                                          bool Hold, bool &IsKnownToBeAllocated,
                                          AllocationFamily Family,
                                          bool ReturnsNullOnFailure) const {
  if (!State)
    return nullptr;

  if (Call.getNumArgs() < (Num + 1))
    return nullptr;

  return FreeMemAux(C, Call.getArgExpr(Num), Call, State, Hold,
                    IsKnownToBeAllocated, Family, ReturnsNullOnFailure);
}

/// Checks if the previous call to free on the given symbol failed - if free
/// failed, returns true. Also, returns the corresponding return value symbol.
static bool didPreviousFreeFail(ProgramStateRef State,
                                SymbolRef Sym, SymbolRef &RetStatusSymbol) {
  const SymbolRef *Ret = State->get<FreeReturnValue>(Sym);
  if (Ret) {
    assert(*Ret && "We should not store the null return symbol");
    ConstraintManager &CMgr = State->getConstraintManager();
    ConditionTruthVal FreeFailed = CMgr.isNull(State, *Ret);
    RetStatusSymbol = *Ret;
    return FreeFailed.isConstrainedTrue();
  }
  return false;
}

static bool printMemFnName(raw_ostream &os, CheckerContext &C, const Expr *E) {
  if (const CallExpr *CE = dyn_cast<CallExpr>(E)) {
    // FIXME: This doesn't handle indirect calls.
    const FunctionDecl *FD = CE->getDirectCallee();
    if (!FD)
      return false;

    os << *FD;
    if (!FD->isOverloadedOperator())
      os << "()";
    return true;
  }

  if (const ObjCMessageExpr *Msg = dyn_cast<ObjCMessageExpr>(E)) {
    if (Msg->isInstanceMessage())
      os << "-";
    else
      os << "+";
    Msg->getSelector().print(os);
    return true;
  }

  if (const CXXNewExpr *NE = dyn_cast<CXXNewExpr>(E)) {
    os << "'"
       << getOperatorSpelling(NE->getOperatorNew()->getOverloadedOperator())
       << "'";
    return true;
  }

  if (const CXXDeleteExpr *DE = dyn_cast<CXXDeleteExpr>(E)) {
    os << "'"
       << getOperatorSpelling(DE->getOperatorDelete()->getOverloadedOperator())
       << "'";
    return true;
  }

  return false;
}

static void printExpectedAllocName(raw_ostream &os, AllocationFamily Family) {

  switch(Family) {
    case AF_Malloc: os << "malloc()"; return;
    case AF_CXXNew: os << "'new'"; return;
    case AF_CXXNewArray: os << "'new[]'"; return;
    case AF_IfNameIndex: os << "'if_nameindex()'"; return;
    case AF_InnerBuffer: os << "container-specific allocator"; return;
    case AF_Alloca:
    case AF_None: llvm_unreachable("not a deallocation expression");
  }
}

static void printExpectedDeallocName(raw_ostream &os, AllocationFamily Family) {
  switch(Family) {
    case AF_Malloc: os << "free()"; return;
    case AF_CXXNew: os << "'delete'"; return;
    case AF_CXXNewArray: os << "'delete[]'"; return;
    case AF_IfNameIndex: os << "'if_freenameindex()'"; return;
    case AF_InnerBuffer: os << "container-specific deallocator"; return;
    case AF_Alloca:
    case AF_None: llvm_unreachable("suspicious argument");
  }
}

ProgramStateRef MallocChecker::FreeMemAux(
    CheckerContext &C, const Expr *ArgExpr, const CallEvent &Call,
    ProgramStateRef State, bool Hold, bool &IsKnownToBeAllocated,
    AllocationFamily Family, bool ReturnsNullOnFailure) const {

  if (!State)
    return nullptr;

  SVal ArgVal = C.getSVal(ArgExpr);
  if (!isa<DefinedOrUnknownSVal>(ArgVal))
    return nullptr;
  DefinedOrUnknownSVal location = ArgVal.castAs<DefinedOrUnknownSVal>();

  // Check for null dereferences.
  if (!isa<Loc>(location))
    return nullptr;

  // The explicit NULL case, no operation is performed.
  ProgramStateRef notNullState, nullState;
  std::tie(notNullState, nullState) = State->assume(location);
  if (nullState && !notNullState)
    return nullptr;

  // Unknown values could easily be okay
  // Undefined values are handled elsewhere
  if (ArgVal.isUnknownOrUndef())
    return nullptr;

  const MemRegion *R = ArgVal.getAsRegion();
  const Expr *ParentExpr = Call.getOriginExpr();

  // NOTE: We detected a bug, but the checker under whose name we would emit the
  // error could be disabled. Generally speaking, the MallocChecker family is an
  // integral part of the Static Analyzer, and disabling any part of it should
  // only be done under exceptional circumstances, such as frequent false
  // positives. If this is the case, we can reasonably believe that there are
  // serious faults in our understanding of the source code, and even if we
  // don't emit an warning, we should terminate further analysis with a sink
  // node.

  // Nonlocs can't be freed, of course.
  // Non-region locations (labels and fixed addresses) also shouldn't be freed.
  if (!R) {
    // Exception:
    // If the macro ZERO_SIZE_PTR is defined, this could be a kernel source
    // code. In that case, the ZERO_SIZE_PTR defines a special value used for a
    // zero-sized memory block which is allowed to be freed, despite not being a
    // null pointer.
    if (Family != AF_Malloc || !isArgZERO_SIZE_PTR(State, C, ArgVal))
      HandleNonHeapDealloc(C, ArgVal, ArgExpr->getSourceRange(), ParentExpr,
                           Family);
    return nullptr;
  }

  R = R->StripCasts();

  // Blocks might show up as heap data, but should not be free()d
  if (isa<BlockDataRegion>(R)) {
    HandleNonHeapDealloc(C, ArgVal, ArgExpr->getSourceRange(), ParentExpr,
                         Family);
    return nullptr;
  }

  const MemSpaceRegion *MS = R->getMemorySpace();

  // Parameters, locals, statics, globals, and memory returned by
  // __builtin_alloca() shouldn't be freed.
  if (!isa<UnknownSpaceRegion, HeapSpaceRegion>(MS)) {
    // FIXME: at the time this code was written, malloc() regions were
    // represented by conjured symbols, which are all in UnknownSpaceRegion.
    // This means that there isn't actually anything from HeapSpaceRegion
    // that should be freed, even though we allow it here.
    // Of course, free() can work on memory allocated outside the current
    // function, so UnknownSpaceRegion is always a possibility.
    // False negatives are better than false positives.

    if (isa<AllocaRegion>(R))
      HandleFreeAlloca(C, ArgVal, ArgExpr->getSourceRange());
    else
      HandleNonHeapDealloc(C, ArgVal, ArgExpr->getSourceRange(), ParentExpr,
                           Family);

    return nullptr;
  }

  const SymbolicRegion *SrBase = dyn_cast<SymbolicRegion>(R->getBaseRegion());
  // Various cases could lead to non-symbol values here.
  // For now, ignore them.
  if (!SrBase)
    return nullptr;

  SymbolRef SymBase = SrBase->getSymbol();
  const RefState *RsBase = State->get<RegionState>(SymBase);
  SymbolRef PreviousRetStatusSymbol = nullptr;

  IsKnownToBeAllocated =
      RsBase && (RsBase->isAllocated() || RsBase->isAllocatedOfSizeZero());

  if (RsBase) {

    // Memory returned by alloca() shouldn't be freed.
    if (RsBase->getAllocationFamily() == AF_Alloca) {
      HandleFreeAlloca(C, ArgVal, ArgExpr->getSourceRange());
      return nullptr;
    }

    // Check for double free first.
    if ((RsBase->isReleased() || RsBase->isRelinquished()) &&
        !didPreviousFreeFail(State, SymBase, PreviousRetStatusSymbol)) {
      HandleDoubleFree(C, ParentExpr->getSourceRange(), RsBase->isReleased(),
                       SymBase, PreviousRetStatusSymbol);
      return nullptr;

    // If the pointer is allocated or escaped, but we are now trying to free it,
    // check that the call to free is proper.
    } else if (RsBase->isAllocated() || RsBase->isAllocatedOfSizeZero() ||
               RsBase->isEscaped()) {

      // Check if an expected deallocation function matches the real one.
      bool DeallocMatchesAlloc = RsBase->getAllocationFamily() == Family;
      if (!DeallocMatchesAlloc) {
        HandleMismatchedDealloc(C, ArgExpr->getSourceRange(), ParentExpr,
                                RsBase, SymBase, Hold);
        return nullptr;
      }

      // Check if the memory location being freed is the actual location
      // allocated, or an offset.
      RegionOffset Offset = R->getAsOffset();
      if (Offset.isValid() &&
          !Offset.hasSymbolicOffset() &&
          Offset.getOffset() != 0) {
        const Expr *AllocExpr = cast<Expr>(RsBase->getStmt());
        HandleOffsetFree(C, ArgVal, ArgExpr->getSourceRange(), ParentExpr,
                         Family, AllocExpr);
        return nullptr;
      }
    }
  }

  if (SymBase->getType()->isFunctionPointerType()) {
    HandleFunctionPtrFree(C, ArgVal, ArgExpr->getSourceRange(), ParentExpr,
                          Family);
    return nullptr;
  }

  // Clean out the info on previous call to free return info.
  State = State->remove<FreeReturnValue>(SymBase);

  // Keep track of the return value. If it is NULL, we will know that free
  // failed.
  if (ReturnsNullOnFailure) {
    SVal RetVal = C.getSVal(ParentExpr);
    SymbolRef RetStatusSymbol = RetVal.getAsSymbol();
    if (RetStatusSymbol) {
      C.getSymbolManager().addSymbolDependency(SymBase, RetStatusSymbol);
      State = State->set<FreeReturnValue>(SymBase, RetStatusSymbol);
    }
  }

  // If we don't know anything about this symbol, a free on it may be totally
  // valid. If this is the case, lets assume that the allocation family of the
  // freeing function is the same as the symbols allocation family, and go with
  // that.
  assert(!RsBase || (RsBase && RsBase->getAllocationFamily() == Family));

  // Normal free.
  if (Hold)
    return State->set<RegionState>(SymBase,
                                   RefState::getRelinquished(Family,
                                                             ParentExpr));

  return State->set<RegionState>(SymBase,
                                 RefState::getReleased(Family, ParentExpr));
}

Optional<MallocChecker::CheckKind>
MallocChecker::getCheckIfTracked(AllocationFamily Family,
                                 bool IsALeakCheck) const {
  switch (Family) {
  case AF_Malloc:
  case AF_Alloca:
  case AF_IfNameIndex: {
    if (ChecksEnabled[CK_MallocChecker])
      return CK_MallocChecker;
    return std::nullopt;
  }
  case AF_CXXNew:
  case AF_CXXNewArray: {
    if (IsALeakCheck) {
      if (ChecksEnabled[CK_NewDeleteLeaksChecker])
        return CK_NewDeleteLeaksChecker;
    }
    else {
      if (ChecksEnabled[CK_NewDeleteChecker])
        return CK_NewDeleteChecker;
    }
    return std::nullopt;
  }
  case AF_InnerBuffer: {
    if (ChecksEnabled[CK_InnerPointerChecker])
      return CK_InnerPointerChecker;
    return std::nullopt;
  }
  case AF_None: {
    llvm_unreachable("no family");
  }
  }
  llvm_unreachable("unhandled family");
}

Optional<MallocChecker::CheckKind>
MallocChecker::getCheckIfTracked(CheckerContext &C, SymbolRef Sym,
                                 bool IsALeakCheck) const {
  if (C.getState()->contains<ReallocSizeZeroSymbols>(Sym))
    return CK_MallocChecker;

  const RefState *RS = C.getState()->get<RegionState>(Sym);
  assert(RS);
  return getCheckIfTracked(RS->getAllocationFamily(), IsALeakCheck);
}

bool MallocChecker::SummarizeValue(raw_ostream &os, SVal V) {
  if (Optional<nonloc::ConcreteInt> IntVal = V.getAs<nonloc::ConcreteInt>())
    os << "an integer (" << IntVal->getValue() << ")";
  else if (Optional<loc::ConcreteInt> ConstAddr = V.getAs<loc::ConcreteInt>())
    os << "a constant address (" << ConstAddr->getValue() << ")";
  else if (Optional<loc::GotoLabel> Label = V.getAs<loc::GotoLabel>())
    os << "the address of the label '" << Label->getLabel()->getName() << "'";
  else
    return false;

  return true;
}

bool MallocChecker::SummarizeRegion(raw_ostream &os,
                                    const MemRegion *MR) {
  switch (MR->getKind()) {
  case MemRegion::FunctionCodeRegionKind: {
    const NamedDecl *FD = cast<FunctionCodeRegion>(MR)->getDecl();
    if (FD)
      os << "the address of the function '" << *FD << '\'';
    else
      os << "the address of a function";
    return true;
  }
  case MemRegion::BlockCodeRegionKind:
    os << "block text";
    return true;
  case MemRegion::BlockDataRegionKind:
    // FIXME: where the block came from?
    os << "a block";
    return true;
  default: {
    const MemSpaceRegion *MS = MR->getMemorySpace();

    if (isa<StackLocalsSpaceRegion>(MS)) {
      const VarRegion *VR = dyn_cast<VarRegion>(MR);
      const VarDecl *VD;
      if (VR)
        VD = VR->getDecl();
      else
        VD = nullptr;

      if (VD)
        os << "the address of the local variable '" << VD->getName() << "'";
      else
        os << "the address of a local stack variable";
      return true;
    }

    if (isa<StackArgumentsSpaceRegion>(MS)) {
      const VarRegion *VR = dyn_cast<VarRegion>(MR);
      const VarDecl *VD;
      if (VR)
        VD = VR->getDecl();
      else
        VD = nullptr;

      if (VD)
        os << "the address of the parameter '" << VD->getName() << "'";
      else
        os << "the address of a parameter";
      return true;
    }

    if (isa<GlobalsSpaceRegion>(MS)) {
      const VarRegion *VR = dyn_cast<VarRegion>(MR);
      const VarDecl *VD;
      if (VR)
        VD = VR->getDecl();
      else
        VD = nullptr;

      if (VD) {
        if (VD->isStaticLocal())
          os << "the address of the static variable '" << VD->getName() << "'";
        else
          os << "the address of the global variable '" << VD->getName() << "'";
      } else
        os << "the address of a global variable";
      return true;
    }

    return false;
  }
  }
}

void MallocChecker::HandleNonHeapDealloc(CheckerContext &C, SVal ArgVal,
                                         SourceRange Range,
                                         const Expr *DeallocExpr,
                                         AllocationFamily Family) const {

  if (!ChecksEnabled[CK_MallocChecker] && !ChecksEnabled[CK_NewDeleteChecker]) {
    C.addSink();
    return;
  }

  Optional<MallocChecker::CheckKind> CheckKind = getCheckIfTracked(Family);
  if (!CheckKind)
    return;

  if (ExplodedNode *N = C.generateErrorNode()) {
    if (!BT_BadFree[*CheckKind])
      BT_BadFree[*CheckKind].reset(new BugType(
          CheckNames[*CheckKind], "Bad free", categories::MemoryError));

    SmallString<100> buf;
    llvm::raw_svector_ostream os(buf);

    const MemRegion *MR = ArgVal.getAsRegion();
    while (const ElementRegion *ER = dyn_cast_or_null<ElementRegion>(MR))
      MR = ER->getSuperRegion();

    os << "Argument to ";
    if (!printMemFnName(os, C, DeallocExpr))
      os << "deallocator";

    os << " is ";
    bool Summarized = MR ? SummarizeRegion(os, MR)
                         : SummarizeValue(os, ArgVal);
    if (Summarized)
      os << ", which is not memory allocated by ";
    else
      os << "not memory allocated by ";

    printExpectedAllocName(os, Family);

    auto R = std::make_unique<PathSensitiveBugReport>(*BT_BadFree[*CheckKind],
                                                      os.str(), N);
    R->markInteresting(MR);
    R->addRange(Range);
    C.emitReport(std::move(R));
  }
}

void MallocChecker::HandleFreeAlloca(CheckerContext &C, SVal ArgVal,
                                     SourceRange Range) const {

  std::optional<MallocChecker::CheckKind> CheckKind;

  if (ChecksEnabled[CK_MallocChecker])
    CheckKind = CK_MallocChecker;
  else if (ChecksEnabled[CK_MismatchedDeallocatorChecker])
    CheckKind = CK_MismatchedDeallocatorChecker;
  else {
    C.addSink();
    return;
  }

  if (ExplodedNode *N = C.generateErrorNode()) {
    if (!BT_FreeAlloca[*CheckKind])
      BT_FreeAlloca[*CheckKind].reset(new BugType(
          CheckNames[*CheckKind], "Free alloca()", categories::MemoryError));

    auto R = std::make_unique<PathSensitiveBugReport>(
        *BT_FreeAlloca[*CheckKind],
        "Memory allocated by alloca() should not be deallocated", N);
    R->markInteresting(ArgVal.getAsRegion());
    R->addRange(Range);
    C.emitReport(std::move(R));
  }
}

void MallocChecker::HandleMismatchedDealloc(CheckerContext &C,
                                            SourceRange Range,
                                            const Expr *DeallocExpr,
                                            const RefState *RS, SymbolRef Sym,
                                            bool OwnershipTransferred) const {

  if (!ChecksEnabled[CK_MismatchedDeallocatorChecker]) {
    C.addSink();
    return;
  }

  if (ExplodedNode *N = C.generateErrorNode()) {
    if (!BT_MismatchedDealloc)
      BT_MismatchedDealloc.reset(
          new BugType(CheckNames[CK_MismatchedDeallocatorChecker],
                      "Bad deallocator", categories::MemoryError));

    SmallString<100> buf;
    llvm::raw_svector_ostream os(buf);

    const Expr *AllocExpr = cast<Expr>(RS->getStmt());
    SmallString<20> AllocBuf;
    llvm::raw_svector_ostream AllocOs(AllocBuf);
    SmallString<20> DeallocBuf;
    llvm::raw_svector_ostream DeallocOs(DeallocBuf);

    if (OwnershipTransferred) {
      if (printMemFnName(DeallocOs, C, DeallocExpr))
        os << DeallocOs.str() << " cannot";
      else
        os << "Cannot";

      os << " take ownership of memory";

      if (printMemFnName(AllocOs, C, AllocExpr))
        os << " allocated by " << AllocOs.str();
    } else {
      os << "Memory";
      if (printMemFnName(AllocOs, C, AllocExpr))
        os << " allocated by " << AllocOs.str();

      os << " should be deallocated by ";
        printExpectedDeallocName(os, RS->getAllocationFamily());

        if (printMemFnName(DeallocOs, C, DeallocExpr))
          os << ", not " << DeallocOs.str();
    }

    auto R = std::make_unique<PathSensitiveBugReport>(*BT_MismatchedDealloc,
                                                      os.str(), N);
    R->markInteresting(Sym);
    R->addRange(Range);
    R->addVisitor<MallocBugVisitor>(Sym);
    C.emitReport(std::move(R));
  }
}

void MallocChecker::HandleOffsetFree(CheckerContext &C, SVal ArgVal,
                                     SourceRange Range, const Expr *DeallocExpr,
                                     AllocationFamily Family,
                                     const Expr *AllocExpr) const {

  if (!ChecksEnabled[CK_MallocChecker] && !ChecksEnabled[CK_NewDeleteChecker]) {
    C.addSink();
    return;
  }

  Optional<MallocChecker::CheckKind> CheckKind = getCheckIfTracked(Family);
  if (!CheckKind)
    return;

  ExplodedNode *N = C.generateErrorNode();
  if (!N)
    return;

  if (!BT_OffsetFree[*CheckKind])
    BT_OffsetFree[*CheckKind].reset(new BugType(
        CheckNames[*CheckKind], "Offset free", categories::MemoryError));

  SmallString<100> buf;
  llvm::raw_svector_ostream os(buf);
  SmallString<20> AllocNameBuf;
  llvm::raw_svector_ostream AllocNameOs(AllocNameBuf);

  const MemRegion *MR = ArgVal.getAsRegion();
  assert(MR && "Only MemRegion based symbols can have offset free errors");

  RegionOffset Offset = MR->getAsOffset();
  assert((Offset.isValid() &&
          !Offset.hasSymbolicOffset() &&
          Offset.getOffset() != 0) &&
         "Only symbols with a valid offset can have offset free errors");

  int offsetBytes = Offset.getOffset() / C.getASTContext().getCharWidth();

  os << "Argument to ";
  if (!printMemFnName(os, C, DeallocExpr))
    os << "deallocator";
  os << " is offset by "
     << offsetBytes
     << " "
     << ((abs(offsetBytes) > 1) ? "bytes" : "byte")
     << " from the start of ";
  if (AllocExpr && printMemFnName(AllocNameOs, C, AllocExpr))
    os << "memory allocated by " << AllocNameOs.str();
  else
    os << "allocated memory";

  auto R = std::make_unique<PathSensitiveBugReport>(*BT_OffsetFree[*CheckKind],
                                                    os.str(), N);
  R->markInteresting(MR->getBaseRegion());
  R->addRange(Range);
  C.emitReport(std::move(R));
}

void MallocChecker::HandleUseAfterFree(CheckerContext &C, SourceRange Range,
                                       SymbolRef Sym) const {

  if (!ChecksEnabled[CK_MallocChecker] && !ChecksEnabled[CK_NewDeleteChecker] &&
      !ChecksEnabled[CK_InnerPointerChecker]) {
    C.addSink();
    return;
  }

  Optional<MallocChecker::CheckKind> CheckKind = getCheckIfTracked(C, Sym);
  if (!CheckKind)
    return;

  if (ExplodedNode *N = C.generateErrorNode()) {
    if (!BT_UseFree[*CheckKind])
      BT_UseFree[*CheckKind].reset(new BugType(
          CheckNames[*CheckKind], "Use-after-free", categories::MemoryError));

    AllocationFamily AF =
        C.getState()->get<RegionState>(Sym)->getAllocationFamily();

    auto R = std::make_unique<PathSensitiveBugReport>(
        *BT_UseFree[*CheckKind],
        AF == AF_InnerBuffer
            ? "Inner pointer of container used after re/deallocation"
            : "Use of memory after it is freed",
        N);

    R->markInteresting(Sym);
    R->addRange(Range);
    R->addVisitor<MallocBugVisitor>(Sym);

    if (AF == AF_InnerBuffer)
      R->addVisitor(allocation_state::getInnerPointerBRVisitor(Sym));

    C.emitReport(std::move(R));
  }
}

void MallocChecker::HandleDoubleFree(CheckerContext &C, SourceRange Range,
                                     bool Released, SymbolRef Sym,
                                     SymbolRef PrevSym) const {

  if (!ChecksEnabled[CK_MallocChecker] && !ChecksEnabled[CK_NewDeleteChecker]) {
    C.addSink();
    return;
  }

  Optional<MallocChecker::CheckKind> CheckKind = getCheckIfTracked(C, Sym);
  if (!CheckKind)
    return;

  if (ExplodedNode *N = C.generateErrorNode()) {
    if (!BT_DoubleFree[*CheckKind])
      BT_DoubleFree[*CheckKind].reset(new BugType(
          CheckNames[*CheckKind], "Double free", categories::MemoryError));

    auto R = std::make_unique<PathSensitiveBugReport>(
        *BT_DoubleFree[*CheckKind],
        (Released ? "Attempt to free released memory"
                  : "Attempt to free non-owned memory"),
        N);
    R->addRange(Range);
    R->markInteresting(Sym);
    if (PrevSym)
      R->markInteresting(PrevSym);
    R->addVisitor<MallocBugVisitor>(Sym);
    C.emitReport(std::move(R));
  }
}

void MallocChecker::HandleDoubleDelete(CheckerContext &C, SymbolRef Sym) const {

  if (!ChecksEnabled[CK_NewDeleteChecker]) {
    C.addSink();
    return;
  }

  Optional<MallocChecker::CheckKind> CheckKind = getCheckIfTracked(C, Sym);
  if (!CheckKind)
    return;

  if (ExplodedNode *N = C.generateErrorNode()) {
    if (!BT_DoubleDelete)
      BT_DoubleDelete.reset(new BugType(CheckNames[CK_NewDeleteChecker],
                                        "Double delete",
                                        categories::MemoryError));

    auto R = std::make_unique<PathSensitiveBugReport>(
        *BT_DoubleDelete, "Attempt to delete released memory", N);

    R->markInteresting(Sym);
    R->addVisitor<MallocBugVisitor>(Sym);
    C.emitReport(std::move(R));
  }
}

void MallocChecker::HandleUseZeroAlloc(CheckerContext &C, SourceRange Range,
                                       SymbolRef Sym) const {

  if (!ChecksEnabled[CK_MallocChecker] && !ChecksEnabled[CK_NewDeleteChecker]) {
    C.addSink();
    return;
  }

  Optional<MallocChecker::CheckKind> CheckKind = getCheckIfTracked(C, Sym);

  if (!CheckKind)
    return;

  if (ExplodedNode *N = C.generateErrorNode()) {
    if (!BT_UseZerroAllocated[*CheckKind])
      BT_UseZerroAllocated[*CheckKind].reset(
          new BugType(CheckNames[*CheckKind], "Use of zero allocated",
                      categories::MemoryError));

    auto R = std::make_unique<PathSensitiveBugReport>(
        *BT_UseZerroAllocated[*CheckKind],
        "Use of memory allocated with size zero", N);

    R->addRange(Range);
    if (Sym) {
      R->markInteresting(Sym);
      R->addVisitor<MallocBugVisitor>(Sym);
    }
    C.emitReport(std::move(R));
  }
}

void MallocChecker::HandleFunctionPtrFree(CheckerContext &C, SVal ArgVal,
                                          SourceRange Range,
                                          const Expr *FreeExpr,
                                          AllocationFamily Family) const {
  if (!ChecksEnabled[CK_MallocChecker]) {
    C.addSink();
    return;
  }

  Optional<MallocChecker::CheckKind> CheckKind = getCheckIfTracked(Family);
  if (!CheckKind)
    return;

  if (ExplodedNode *N = C.generateErrorNode()) {
    if (!BT_BadFree[*CheckKind])
      BT_BadFree[*CheckKind].reset(new BugType(
          CheckNames[*CheckKind], "Bad free", categories::MemoryError));

    SmallString<100> Buf;
    llvm::raw_svector_ostream Os(Buf);

    const MemRegion *MR = ArgVal.getAsRegion();
    while (const ElementRegion *ER = dyn_cast_or_null<ElementRegion>(MR))
      MR = ER->getSuperRegion();

    Os << "Argument to ";
    if (!printMemFnName(Os, C, FreeExpr))
      Os << "deallocator";

    Os << " is a function pointer";

    auto R = std::make_unique<PathSensitiveBugReport>(*BT_BadFree[*CheckKind],
                                                      Os.str(), N);
    R->markInteresting(MR);
    R->addRange(Range);
    C.emitReport(std::move(R));
  }
}

ProgramStateRef
MallocChecker::ReallocMemAux(CheckerContext &C, const CallEvent &Call,
                             bool ShouldFreeOnFail, ProgramStateRef State,
                             AllocationFamily Family, bool SuffixWithN) const {
  if (!State)
    return nullptr;

  const CallExpr *CE = cast<CallExpr>(Call.getOriginExpr());

  if (SuffixWithN && CE->getNumArgs() < 3)
    return nullptr;
  else if (CE->getNumArgs() < 2)
    return nullptr;

  const Expr *arg0Expr = CE->getArg(0);
  SVal Arg0Val = C.getSVal(arg0Expr);
  if (!isa<DefinedOrUnknownSVal>(Arg0Val))
    return nullptr;
  DefinedOrUnknownSVal arg0Val = Arg0Val.castAs<DefinedOrUnknownSVal>();

  SValBuilder &svalBuilder = C.getSValBuilder();

  DefinedOrUnknownSVal PtrEQ = svalBuilder.evalEQ(
      State, arg0Val, svalBuilder.makeNullWithType(arg0Expr->getType()));

  // Get the size argument.
  const Expr *Arg1 = CE->getArg(1);

  // Get the value of the size argument.
  SVal TotalSize = C.getSVal(Arg1);
  if (SuffixWithN)
    TotalSize = evalMulForBufferSize(C, Arg1, CE->getArg(2));
  if (!isa<DefinedOrUnknownSVal>(TotalSize))
    return nullptr;

  // Compare the size argument to 0.
  DefinedOrUnknownSVal SizeZero =
      svalBuilder.evalEQ(State, TotalSize.castAs<DefinedOrUnknownSVal>(),
                         svalBuilder.makeIntValWithWidth(
                             svalBuilder.getContext().getSizeType(), 0));

  ProgramStateRef StatePtrIsNull, StatePtrNotNull;
  std::tie(StatePtrIsNull, StatePtrNotNull) = State->assume(PtrEQ);
  ProgramStateRef StateSizeIsZero, StateSizeNotZero;
  std::tie(StateSizeIsZero, StateSizeNotZero) = State->assume(SizeZero);
  // We only assume exceptional states if they are definitely true; if the
  // state is under-constrained, assume regular realloc behavior.
  bool PrtIsNull = StatePtrIsNull && !StatePtrNotNull;
  bool SizeIsZero = StateSizeIsZero && !StateSizeNotZero;

  // If the ptr is NULL and the size is not 0, the call is equivalent to
  // malloc(size).
  if (PrtIsNull && !SizeIsZero) {
    ProgramStateRef stateMalloc = MallocMemAux(
        C, Call, TotalSize, UndefinedVal(), StatePtrIsNull, Family);
    return stateMalloc;
  }

  if (PrtIsNull && SizeIsZero)
    return State;

  assert(!PrtIsNull);

  bool IsKnownToBeAllocated = false;

  // If the size is 0, free the memory.
  if (SizeIsZero)
    // The semantics of the return value are:
    // If size was equal to 0, either NULL or a pointer suitable to be passed
    // to free() is returned. We just free the input pointer and do not add
    // any constrains on the output pointer.
    if (ProgramStateRef stateFree = FreeMemAux(
            C, Call, StateSizeIsZero, 0, false, IsKnownToBeAllocated, Family))
      return stateFree;

  // Default behavior.
  if (ProgramStateRef stateFree =
          FreeMemAux(C, Call, State, 0, false, IsKnownToBeAllocated, Family)) {

    ProgramStateRef stateRealloc =
        MallocMemAux(C, Call, TotalSize, UnknownVal(), stateFree, Family);
    if (!stateRealloc)
      return nullptr;

    OwnershipAfterReallocKind Kind = OAR_ToBeFreedAfterFailure;
    if (ShouldFreeOnFail)
      Kind = OAR_FreeOnFailure;
    else if (!IsKnownToBeAllocated)
      Kind = OAR_DoNotTrackAfterFailure;

    // Get the from and to pointer symbols as in toPtr = realloc(fromPtr, size).
    SymbolRef FromPtr = arg0Val.getLocSymbolInBase();
    SVal RetVal = C.getSVal(CE);
    SymbolRef ToPtr = RetVal.getAsSymbol();
    assert(FromPtr && ToPtr &&
           "By this point, FreeMemAux and MallocMemAux should have checked "
           "whether the argument or the return value is symbolic!");

    // Record the info about the reallocated symbol so that we could properly
    // process failed reallocation.
    stateRealloc = stateRealloc->set<ReallocPairs>(ToPtr,
                                                   ReallocPair(FromPtr, Kind));
    // The reallocated symbol should stay alive for as long as the new symbol.
    C.getSymbolManager().addSymbolDependency(ToPtr, FromPtr);
    return stateRealloc;
  }
  return nullptr;
}

ProgramStateRef MallocChecker::CallocMem(CheckerContext &C,
                                         const CallEvent &Call,
                                         ProgramStateRef State) {
  if (!State)
    return nullptr;

  if (Call.getNumArgs() < 2)
    return nullptr;

  SValBuilder &svalBuilder = C.getSValBuilder();
  SVal zeroVal = svalBuilder.makeZeroVal(svalBuilder.getContext().CharTy);
  SVal TotalSize =
      evalMulForBufferSize(C, Call.getArgExpr(0), Call.getArgExpr(1));

  return MallocMemAux(C, Call, TotalSize, zeroVal, State, AF_Malloc);
}

MallocChecker::LeakInfo MallocChecker::getAllocationSite(const ExplodedNode *N,
                                                         SymbolRef Sym,
                                                         CheckerContext &C) {
  const LocationContext *LeakContext = N->getLocationContext();
  // Walk the ExplodedGraph backwards and find the first node that referred to
  // the tracked symbol.
  const ExplodedNode *AllocNode = N;
  const MemRegion *ReferenceRegion = nullptr;

  while (N) {
    ProgramStateRef State = N->getState();
    if (!State->get<RegionState>(Sym))
      break;

    // Find the most recent expression bound to the symbol in the current
    // context.
    if (!ReferenceRegion) {
      if (const MemRegion *MR = C.getLocationRegionIfPostStore(N)) {
        SVal Val = State->getSVal(MR);
        if (Val.getAsLocSymbol() == Sym) {
          const VarRegion *VR = MR->getBaseRegion()->getAs<VarRegion>();
          // Do not show local variables belonging to a function other than
          // where the error is reported.
          if (!VR || (VR->getStackFrame() == LeakContext->getStackFrame()))
            ReferenceRegion = MR;
        }
      }
    }

    // Allocation node, is the last node in the current or parent context in
    // which the symbol was tracked.
    const LocationContext *NContext = N->getLocationContext();
    if (NContext == LeakContext ||
        NContext->isParentOf(LeakContext))
      AllocNode = N;
    N = N->pred_empty() ? nullptr : *(N->pred_begin());
  }

  return LeakInfo(AllocNode, ReferenceRegion);
}

void MallocChecker::HandleLeak(SymbolRef Sym, ExplodedNode *N,
                               CheckerContext &C) const {

  if (!ChecksEnabled[CK_MallocChecker] &&
      !ChecksEnabled[CK_NewDeleteLeaksChecker])
    return;

  const RefState *RS = C.getState()->get<RegionState>(Sym);
  assert(RS && "cannot leak an untracked symbol");
  AllocationFamily Family = RS->getAllocationFamily();

  if (Family == AF_Alloca)
    return;

  Optional<MallocChecker::CheckKind>
      CheckKind = getCheckIfTracked(Family, true);

  if (!CheckKind)
    return;

  assert(N);
  if (!BT_Leak[*CheckKind]) {
    // Leaks should not be reported if they are post-dominated by a sink:
    // (1) Sinks are higher importance bugs.
    // (2) NoReturnFunctionChecker uses sink nodes to represent paths ending
    //     with __noreturn functions such as assert() or exit(). We choose not
    //     to report leaks on such paths.
    BT_Leak[*CheckKind].reset(new BugType(CheckNames[*CheckKind], "Memory leak",
                                          categories::MemoryError,
                                          /*SuppressOnSink=*/true));
  }

  // Most bug reports are cached at the location where they occurred.
  // With leaks, we want to unique them by the location where they were
  // allocated, and only report a single path.
  PathDiagnosticLocation LocUsedForUniqueing;
  const ExplodedNode *AllocNode = nullptr;
  const MemRegion *Region = nullptr;
  std::tie(AllocNode, Region) = getAllocationSite(N, Sym, C);

  const Stmt *AllocationStmt = AllocNode->getStmtForDiagnostics();
  if (AllocationStmt)
    LocUsedForUniqueing = PathDiagnosticLocation::createBegin(AllocationStmt,
                                              C.getSourceManager(),
                                              AllocNode->getLocationContext());

  SmallString<200> buf;
  llvm::raw_svector_ostream os(buf);
  if (Region && Region->canPrintPretty()) {
    os << "Potential leak of memory pointed to by ";
    Region->printPretty(os);
  } else {
    os << "Potential memory leak";
  }

  auto R = std::make_unique<PathSensitiveBugReport>(
      *BT_Leak[*CheckKind], os.str(), N, LocUsedForUniqueing,
      AllocNode->getLocationContext()->getDecl());
  R->markInteresting(Sym);
  R->addVisitor<MallocBugVisitor>(Sym, true);
  if (ShouldRegisterNoOwnershipChangeVisitor)
    R->addVisitor<NoOwnershipChangeVisitor>(Sym, this);
  C.emitReport(std::move(R));
}

void MallocChecker::checkDeadSymbols(SymbolReaper &SymReaper,
                                     CheckerContext &C) const
{
  ProgramStateRef state = C.getState();
  RegionStateTy OldRS = state->get<RegionState>();
  RegionStateTy::Factory &F = state->get_context<RegionState>();

  RegionStateTy RS = OldRS;
  SmallVector<SymbolRef, 2> Errors;
  for (RegionStateTy::iterator I = RS.begin(), E = RS.end(); I != E; ++I) {
    if (SymReaper.isDead(I->first)) {
      if (I->second.isAllocated() || I->second.isAllocatedOfSizeZero())
        Errors.push_back(I->first);
      // Remove the dead symbol from the map.
      RS = F.remove(RS, I->first);
    }
  }

  if (RS == OldRS) {
    // We shouldn't have touched other maps yet.
    assert(state->get<ReallocPairs>() ==
           C.getState()->get<ReallocPairs>());
    assert(state->get<FreeReturnValue>() ==
           C.getState()->get<FreeReturnValue>());
    return;
  }

  // Cleanup the Realloc Pairs Map.
  ReallocPairsTy RP = state->get<ReallocPairs>();
  for (ReallocPairsTy::iterator I = RP.begin(), E = RP.end(); I != E; ++I) {
    if (SymReaper.isDead(I->first) ||
        SymReaper.isDead(I->second.ReallocatedSym)) {
      state = state->remove<ReallocPairs>(I->first);
    }
  }

  // Cleanup the FreeReturnValue Map.
  FreeReturnValueTy FR = state->get<FreeReturnValue>();
  for (FreeReturnValueTy::iterator I = FR.begin(), E = FR.end(); I != E; ++I) {
    if (SymReaper.isDead(I->first) ||
        SymReaper.isDead(I->second)) {
      state = state->remove<FreeReturnValue>(I->first);
    }
  }

  // Generate leak node.
  ExplodedNode *N = C.getPredecessor();
  if (!Errors.empty()) {
    static CheckerProgramPointTag Tag("MallocChecker", "DeadSymbolsLeak");
    N = C.generateNonFatalErrorNode(C.getState(), &Tag);
    if (N) {
      for (SmallVectorImpl<SymbolRef>::iterator
           I = Errors.begin(), E = Errors.end(); I != E; ++I) {
        HandleLeak(*I, N, C);
      }
    }
  }

  C.addTransition(state->set<RegionState>(RS), N);
}

void MallocChecker::checkPreCall(const CallEvent &Call,
                                 CheckerContext &C) const {

  if (const auto *DC = dyn_cast<CXXDeallocatorCall>(&Call)) {
    const CXXDeleteExpr *DE = DC->getOriginExpr();

    if (!ChecksEnabled[CK_NewDeleteChecker])
      if (SymbolRef Sym = C.getSVal(DE->getArgument()).getAsSymbol())
        checkUseAfterFree(Sym, C, DE->getArgument());

    if (!isStandardNewDelete(DC->getDecl()))
      return;

    ProgramStateRef State = C.getState();
    bool IsKnownToBeAllocated;
    State = FreeMemAux(C, DE->getArgument(), Call, State,
                       /*Hold*/ false, IsKnownToBeAllocated,
                       (DE->isArrayForm() ? AF_CXXNewArray : AF_CXXNew));

    C.addTransition(State);
    return;
  }

  if (const auto *DC = dyn_cast<CXXDestructorCall>(&Call)) {
    SymbolRef Sym = DC->getCXXThisVal().getAsSymbol();
    if (!Sym || checkDoubleDelete(Sym, C))
      return;
  }

  // We will check for double free in the post visit.
  if (const AnyFunctionCall *FC = dyn_cast<AnyFunctionCall>(&Call)) {
    const FunctionDecl *FD = FC->getDecl();
    if (!FD)
      return;

    if (ChecksEnabled[CK_MallocChecker] && isFreeingCall(Call))
      return;
  }

  // Check if the callee of a method is deleted.
  if (const CXXInstanceCall *CC = dyn_cast<CXXInstanceCall>(&Call)) {
    SymbolRef Sym = CC->getCXXThisVal().getAsSymbol();
    if (!Sym || checkUseAfterFree(Sym, C, CC->getCXXThisExpr()))
      return;
  }

  // Check arguments for being used after free.
  for (unsigned I = 0, E = Call.getNumArgs(); I != E; ++I) {
    SVal ArgSVal = Call.getArgSVal(I);
    if (isa<Loc>(ArgSVal)) {
      SymbolRef Sym = ArgSVal.getAsSymbol();
      if (!Sym)
        continue;
      if (checkUseAfterFree(Sym, C, Call.getArgExpr(I)))
        return;
    }
  }
}

void MallocChecker::checkPreStmt(const ReturnStmt *S,
                                 CheckerContext &C) const {
  checkEscapeOnReturn(S, C);
}

// In the CFG, automatic destructors come after the return statement.
// This callback checks for returning memory that is freed by automatic
// destructors, as those cannot be reached in checkPreStmt().
void MallocChecker::checkEndFunction(const ReturnStmt *S,
                                     CheckerContext &C) const {
  checkEscapeOnReturn(S, C);
}

void MallocChecker::checkEscapeOnReturn(const ReturnStmt *S,
                                        CheckerContext &C) const {
  if (!S)
    return;

  const Expr *E = S->getRetValue();
  if (!E)
    return;

  // Check if we are returning a symbol.
  ProgramStateRef State = C.getState();
  SVal RetVal = C.getSVal(E);
  SymbolRef Sym = RetVal.getAsSymbol();
  if (!Sym)
    // If we are returning a field of the allocated struct or an array element,
    // the callee could still free the memory.
    // TODO: This logic should be a part of generic symbol escape callback.
    if (const MemRegion *MR = RetVal.getAsRegion())
      if (isa<FieldRegion, ElementRegion>(MR))
        if (const SymbolicRegion *BMR =
              dyn_cast<SymbolicRegion>(MR->getBaseRegion()))
          Sym = BMR->getSymbol();

  // Check if we are returning freed memory.
  if (Sym)
    checkUseAfterFree(Sym, C, E);
}

// TODO: Blocks should be either inlined or should call invalidate regions
// upon invocation. After that's in place, special casing here will not be
// needed.
void MallocChecker::checkPostStmt(const BlockExpr *BE,
                                  CheckerContext &C) const {

  // Scan the BlockDecRefExprs for any object the retain count checker
  // may be tracking.
  if (!BE->getBlockDecl()->hasCaptures())
    return;

  ProgramStateRef state = C.getState();
  const BlockDataRegion *R =
    cast<BlockDataRegion>(C.getSVal(BE).getAsRegion());

  BlockDataRegion::referenced_vars_iterator I = R->referenced_vars_begin(),
                                            E = R->referenced_vars_end();

  if (I == E)
    return;

  SmallVector<const MemRegion*, 10> Regions;
  const LocationContext *LC = C.getLocationContext();
  MemRegionManager &MemMgr = C.getSValBuilder().getRegionManager();

  for ( ; I != E; ++I) {
    const VarRegion *VR = I.getCapturedRegion();
    if (VR->getSuperRegion() == R) {
      VR = MemMgr.getVarRegion(VR->getDecl(), LC);
    }
    Regions.push_back(VR);
  }

  state =
    state->scanReachableSymbols<StopTrackingCallback>(Regions).getState();
  C.addTransition(state);
}

static bool isReleased(SymbolRef Sym, CheckerContext &C) {
  assert(Sym);
  const RefState *RS = C.getState()->get<RegionState>(Sym);
  return (RS && RS->isReleased());
}

bool MallocChecker::suppressDeallocationsInSuspiciousContexts(
    const CallEvent &Call, CheckerContext &C) const {
  if (Call.getNumArgs() == 0)
    return false;

  StringRef FunctionStr = "";
  if (const auto *FD = dyn_cast<FunctionDecl>(C.getStackFrame()->getDecl()))
    if (const Stmt *Body = FD->getBody())
      if (Body->getBeginLoc().isValid())
        FunctionStr =
            Lexer::getSourceText(CharSourceRange::getTokenRange(
                                     {FD->getBeginLoc(), Body->getBeginLoc()}),
                                 C.getSourceManager(), C.getLangOpts());

  // We do not model the Integer Set Library's retain-count based allocation.
  if (!FunctionStr.contains("__isl_"))
    return false;

  ProgramStateRef State = C.getState();

  for (const Expr *Arg : cast<CallExpr>(Call.getOriginExpr())->arguments())
    if (SymbolRef Sym = C.getSVal(Arg).getAsSymbol())
      if (const RefState *RS = State->get<RegionState>(Sym))
        State = State->set<RegionState>(Sym, RefState::getEscaped(RS));

  C.addTransition(State);
  return true;
}

bool MallocChecker::checkUseAfterFree(SymbolRef Sym, CheckerContext &C,
                                      const Stmt *S) const {

  if (isReleased(Sym, C)) {
    HandleUseAfterFree(C, S->getSourceRange(), Sym);
    return true;
  }

  return false;
}

void MallocChecker::checkUseZeroAllocated(SymbolRef Sym, CheckerContext &C,
                                          const Stmt *S) const {
  assert(Sym);

  if (const RefState *RS = C.getState()->get<RegionState>(Sym)) {
    if (RS->isAllocatedOfSizeZero())
      HandleUseZeroAlloc(C, RS->getStmt()->getSourceRange(), Sym);
  }
  else if (C.getState()->contains<ReallocSizeZeroSymbols>(Sym)) {
    HandleUseZeroAlloc(C, S->getSourceRange(), Sym);
  }
}

bool MallocChecker::checkDoubleDelete(SymbolRef Sym, CheckerContext &C) const {

  if (isReleased(Sym, C)) {
    HandleDoubleDelete(C, Sym);
    return true;
  }
  return false;
}

// Check if the location is a freed symbolic region.
void MallocChecker::checkLocation(SVal l, bool isLoad, const Stmt *S,
                                  CheckerContext &C) const {
  SymbolRef Sym = l.getLocSymbolInBase();
  if (Sym) {
    checkUseAfterFree(Sym, C, S);
    checkUseZeroAllocated(Sym, C, S);
  }
}

// If a symbolic region is assumed to NULL (or another constant), stop tracking
// it - assuming that allocation failed on this path.
ProgramStateRef MallocChecker::evalAssume(ProgramStateRef state,
                                              SVal Cond,
                                              bool Assumption) const {
  RegionStateTy RS = state->get<RegionState>();
  for (RegionStateTy::iterator I = RS.begin(), E = RS.end(); I != E; ++I) {
    // If the symbol is assumed to be NULL, remove it from consideration.
    ConstraintManager &CMgr = state->getConstraintManager();
    ConditionTruthVal AllocFailed = CMgr.isNull(state, I.getKey());
    if (AllocFailed.isConstrainedTrue())
      state = state->remove<RegionState>(I.getKey());
  }

  // Realloc returns 0 when reallocation fails, which means that we should
  // restore the state of the pointer being reallocated.
  ReallocPairsTy RP = state->get<ReallocPairs>();
  for (ReallocPairsTy::iterator I = RP.begin(), E = RP.end(); I != E; ++I) {
    // If the symbol is assumed to be NULL, remove it from consideration.
    ConstraintManager &CMgr = state->getConstraintManager();
    ConditionTruthVal AllocFailed = CMgr.isNull(state, I.getKey());
    if (!AllocFailed.isConstrainedTrue())
      continue;

    SymbolRef ReallocSym = I.getData().ReallocatedSym;
    if (const RefState *RS = state->get<RegionState>(ReallocSym)) {
      if (RS->isReleased()) {
        switch (I.getData().Kind) {
        case OAR_ToBeFreedAfterFailure:
          state = state->set<RegionState>(ReallocSym,
              RefState::getAllocated(RS->getAllocationFamily(), RS->getStmt()));
          break;
        case OAR_DoNotTrackAfterFailure:
          state = state->remove<RegionState>(ReallocSym);
          break;
        default:
          assert(I.getData().Kind == OAR_FreeOnFailure);
        }
      }
    }
    state = state->remove<ReallocPairs>(I.getKey());
  }

  return state;
}

bool MallocChecker::mayFreeAnyEscapedMemoryOrIsModeledExplicitly(
                                              const CallEvent *Call,
                                              ProgramStateRef State,
                                              SymbolRef &EscapingSymbol) const {
  assert(Call);
  EscapingSymbol = nullptr;

  // For now, assume that any C++ or block call can free memory.
  // TODO: If we want to be more optimistic here, we'll need to make sure that
  // regions escape to C++ containers. They seem to do that even now, but for
  // mysterious reasons.
  if (!isa<SimpleFunctionCall, ObjCMethodCall>(Call))
    return true;

  // Check Objective-C messages by selector name.
  if (const ObjCMethodCall *Msg = dyn_cast<ObjCMethodCall>(Call)) {
    // If it's not a framework call, or if it takes a callback, assume it
    // can free memory.
    if (!Call->isInSystemHeader() || Call->argumentsMayEscape())
      return true;

    // If it's a method we know about, handle it explicitly post-call.
    // This should happen before the "freeWhenDone" check below.
    if (isKnownDeallocObjCMethodName(*Msg))
      return false;

    // If there's a "freeWhenDone" parameter, but the method isn't one we know
    // about, we can't be sure that the object will use free() to deallocate the
    // memory, so we can't model it explicitly. The best we can do is use it to
    // decide whether the pointer escapes.
    if (std::optional<bool> FreeWhenDone = getFreeWhenDoneArg(*Msg))
      return *FreeWhenDone;

    // If the first selector piece ends with "NoCopy", and there is no
    // "freeWhenDone" parameter set to zero, we know ownership is being
    // transferred. Again, though, we can't be sure that the object will use
    // free() to deallocate the memory, so we can't model it explicitly.
    StringRef FirstSlot = Msg->getSelector().getNameForSlot(0);
    if (FirstSlot.endswith("NoCopy"))
      return true;

    // If the first selector starts with addPointer, insertPointer,
    // or replacePointer, assume we are dealing with NSPointerArray or similar.
    // This is similar to C++ containers (vector); we still might want to check
    // that the pointers get freed by following the container itself.
    if (FirstSlot.startswith("addPointer") ||
        FirstSlot.startswith("insertPointer") ||
        FirstSlot.startswith("replacePointer") ||
        FirstSlot.equals("valueWithPointer")) {
      return true;
    }

    // We should escape receiver on call to 'init'. This is especially relevant
    // to the receiver, as the corresponding symbol is usually not referenced
    // after the call.
    if (Msg->getMethodFamily() == OMF_init) {
      EscapingSymbol = Msg->getReceiverSVal().getAsSymbol();
      return true;
    }

    // Otherwise, assume that the method does not free memory.
    // Most framework methods do not free memory.
    return false;
  }

  // At this point the only thing left to handle is straight function calls.
  const FunctionDecl *FD = cast<SimpleFunctionCall>(Call)->getDecl();
  if (!FD)
    return true;

  // If it's one of the allocation functions we can reason about, we model
  // its behavior explicitly.
  if (isMemCall(*Call))
    return false;

  // If it's not a system call, assume it frees memory.
  if (!Call->isInSystemHeader())
    return true;

  // White list the system functions whose arguments escape.
  const IdentifierInfo *II = FD->getIdentifier();
  if (!II)
    return true;
  StringRef FName = II->getName();

  // White list the 'XXXNoCopy' CoreFoundation functions.
  // We specifically check these before
  if (FName.endswith("NoCopy")) {
    // Look for the deallocator argument. We know that the memory ownership
    // is not transferred only if the deallocator argument is
    // 'kCFAllocatorNull'.
    for (unsigned i = 1; i < Call->getNumArgs(); ++i) {
      const Expr *ArgE = Call->getArgExpr(i)->IgnoreParenCasts();
      if (const DeclRefExpr *DE = dyn_cast<DeclRefExpr>(ArgE)) {
        StringRef DeallocatorName = DE->getFoundDecl()->getName();
        if (DeallocatorName == "kCFAllocatorNull")
          return false;
      }
    }
    return true;
  }

  // Associating streams with malloced buffers. The pointer can escape if
  // 'closefn' is specified (and if that function does free memory),
  // but it will not if closefn is not specified.
  // Currently, we do not inspect the 'closefn' function (PR12101).
  if (FName == "funopen")
    if (Call->getNumArgs() >= 4 && Call->getArgSVal(4).isConstant(0))
      return false;

  // Do not warn on pointers passed to 'setbuf' when used with std streams,
  // these leaks might be intentional when setting the buffer for stdio.
  // http://stackoverflow.com/questions/2671151/who-frees-setvbuf-buffer
  if (FName == "setbuf" || FName =="setbuffer" ||
      FName == "setlinebuf" || FName == "setvbuf") {
    if (Call->getNumArgs() >= 1) {
      const Expr *ArgE = Call->getArgExpr(0)->IgnoreParenCasts();
      if (const DeclRefExpr *ArgDRE = dyn_cast<DeclRefExpr>(ArgE))
        if (const VarDecl *D = dyn_cast<VarDecl>(ArgDRE->getDecl()))
          if (D->getCanonicalDecl()->getName().contains("std"))
            return true;
    }
  }

  // A bunch of other functions which either take ownership of a pointer or
  // wrap the result up in a struct or object, meaning it can be freed later.
  // (See RetainCountChecker.) Not all the parameters here are invalidated,
  // but the Malloc checker cannot differentiate between them. The right way
  // of doing this would be to implement a pointer escapes callback.
  if (FName == "CGBitmapContextCreate" ||
      FName == "CGBitmapContextCreateWithData" ||
      FName == "CVPixelBufferCreateWithBytes" ||
      FName == "CVPixelBufferCreateWithPlanarBytes" ||
      FName == "OSAtomicEnqueue") {
    return true;
  }

  if (FName == "postEvent" &&
      FD->getQualifiedNameAsString() == "QCoreApplication::postEvent") {
    return true;
  }

  if (FName == "connectImpl" &&
      FD->getQualifiedNameAsString() == "QObject::connectImpl") {
    return true;
  }

  // Handle cases where we know a buffer's /address/ can escape.
  // Note that the above checks handle some special cases where we know that
  // even though the address escapes, it's still our responsibility to free the
  // buffer.
  if (Call->argumentsMayEscape())
    return true;

  // Otherwise, assume that the function does not free memory.
  // Most system calls do not free the memory.
  return false;
}

ProgramStateRef MallocChecker::checkPointerEscape(ProgramStateRef State,
                                             const InvalidatedSymbols &Escaped,
                                             const CallEvent *Call,
                                             PointerEscapeKind Kind) const {
  return checkPointerEscapeAux(State, Escaped, Call, Kind,
                               /*IsConstPointerEscape*/ false);
}

ProgramStateRef MallocChecker::checkConstPointerEscape(ProgramStateRef State,
                                              const InvalidatedSymbols &Escaped,
                                              const CallEvent *Call,
                                              PointerEscapeKind Kind) const {
  // If a const pointer escapes, it may not be freed(), but it could be deleted.
  return checkPointerEscapeAux(State, Escaped, Call, Kind,
                               /*IsConstPointerEscape*/ true);
}

static bool checkIfNewOrNewArrayFamily(const RefState *RS) {
  return (RS->getAllocationFamily() == AF_CXXNewArray ||
          RS->getAllocationFamily() == AF_CXXNew);
}

ProgramStateRef MallocChecker::checkPointerEscapeAux(
    ProgramStateRef State, const InvalidatedSymbols &Escaped,
    const CallEvent *Call, PointerEscapeKind Kind,
    bool IsConstPointerEscape) const {
  // If we know that the call does not free memory, or we want to process the
  // call later, keep tracking the top level arguments.
  SymbolRef EscapingSymbol = nullptr;
  if (Kind == PSK_DirectEscapeOnCall &&
      !mayFreeAnyEscapedMemoryOrIsModeledExplicitly(Call, State,
                                                    EscapingSymbol) &&
      !EscapingSymbol) {
    return State;
  }

  for (InvalidatedSymbols::const_iterator I = Escaped.begin(),
       E = Escaped.end();
       I != E; ++I) {
    SymbolRef sym = *I;

    if (EscapingSymbol && EscapingSymbol != sym)
      continue;

    if (const RefState *RS = State->get<RegionState>(sym))
      if (RS->isAllocated() || RS->isAllocatedOfSizeZero())
        if (!IsConstPointerEscape || checkIfNewOrNewArrayFamily(RS))
          State = State->set<RegionState>(sym, RefState::getEscaped(RS));
  }
  return State;
}

bool MallocChecker::isArgZERO_SIZE_PTR(ProgramStateRef State, CheckerContext &C,
                                       SVal ArgVal) const {
  if (!KernelZeroSizePtrValue)
    KernelZeroSizePtrValue =
        tryExpandAsInteger("ZERO_SIZE_PTR", C.getPreprocessor());

  const llvm::APSInt *ArgValKnown =
      C.getSValBuilder().getKnownValue(State, ArgVal);
  return ArgValKnown && *KernelZeroSizePtrValue &&
         ArgValKnown->getSExtValue() == **KernelZeroSizePtrValue;
}

static SymbolRef findFailedReallocSymbol(ProgramStateRef currState,
                                         ProgramStateRef prevState) {
  ReallocPairsTy currMap = currState->get<ReallocPairs>();
  ReallocPairsTy prevMap = prevState->get<ReallocPairs>();

  for (const ReallocPairsTy::value_type &Pair : prevMap) {
    SymbolRef sym = Pair.first;
    if (!currMap.lookup(sym))
      return sym;
  }

  return nullptr;
}

static bool isReferenceCountingPointerDestructor(const CXXDestructorDecl *DD) {
  if (const IdentifierInfo *II = DD->getParent()->getIdentifier()) {
    StringRef N = II->getName();
    if (N.contains_insensitive("ptr") || N.contains_insensitive("pointer")) {
      if (N.contains_insensitive("ref") || N.contains_insensitive("cnt") ||
          N.contains_insensitive("intrusive") ||
          N.contains_insensitive("shared")) {
        return true;
      }
    }
  }
  return false;
}

PathDiagnosticPieceRef MallocBugVisitor::VisitNode(const ExplodedNode *N,
                                                   BugReporterContext &BRC,
                                                   PathSensitiveBugReport &BR) {
  ProgramStateRef state = N->getState();
  ProgramStateRef statePrev = N->getFirstPred()->getState();

  const RefState *RSCurr = state->get<RegionState>(Sym);
  const RefState *RSPrev = statePrev->get<RegionState>(Sym);

  const Stmt *S = N->getStmtForDiagnostics();
  // When dealing with containers, we sometimes want to give a note
  // even if the statement is missing.
  if (!S && (!RSCurr || RSCurr->getAllocationFamily() != AF_InnerBuffer))
    return nullptr;

  const LocationContext *CurrentLC = N->getLocationContext();

  // If we find an atomic fetch_add or fetch_sub within the destructor in which
  // the pointer was released (before the release), this is likely a destructor
  // of a shared pointer.
  // Because we don't model atomics, and also because we don't know that the
  // original reference count is positive, we should not report use-after-frees
  // on objects deleted in such destructors. This can probably be improved
  // through better shared pointer modeling.
  if (ReleaseDestructorLC) {
    if (const auto *AE = dyn_cast<AtomicExpr>(S)) {
      AtomicExpr::AtomicOp Op = AE->getOp();
      if (Op == AtomicExpr::AO__c11_atomic_fetch_add ||
          Op == AtomicExpr::AO__c11_atomic_fetch_sub) {
        if (ReleaseDestructorLC == CurrentLC ||
            ReleaseDestructorLC->isParentOf(CurrentLC)) {
          BR.markInvalid(getTag(), S);
        }
      }
    }
  }

  // FIXME: We will eventually need to handle non-statement-based events
  // (__attribute__((cleanup))).

  // Find out if this is an interesting point and what is the kind.
  StringRef Msg;
  std::unique_ptr<StackHintGeneratorForSymbol> StackHint = nullptr;
  SmallString<256> Buf;
  llvm::raw_svector_ostream OS(Buf);

  if (Mode == Normal) {
    if (isAllocated(RSCurr, RSPrev, S)) {
      Msg = "Memory is allocated";
      StackHint = std::make_unique<StackHintGeneratorForSymbol>(
          Sym, "Returned allocated memory");
    } else if (isReleased(RSCurr, RSPrev, S)) {
      const auto Family = RSCurr->getAllocationFamily();
      switch (Family) {
        case AF_Alloca:
        case AF_Malloc:
        case AF_CXXNew:
        case AF_CXXNewArray:
        case AF_IfNameIndex:
          Msg = "Memory is released";
          StackHint = std::make_unique<StackHintGeneratorForSymbol>(
              Sym, "Returning; memory was released");
          break;
        case AF_InnerBuffer: {
          const MemRegion *ObjRegion =
              allocation_state::getContainerObjRegion(statePrev, Sym);
          const auto *TypedRegion = cast<TypedValueRegion>(ObjRegion);
          QualType ObjTy = TypedRegion->getValueType();
          OS << "Inner buffer of '" << ObjTy << "' ";

          if (N->getLocation().getKind() == ProgramPoint::PostImplicitCallKind) {
            OS << "deallocated by call to destructor";
            StackHint = std::make_unique<StackHintGeneratorForSymbol>(
                Sym, "Returning; inner buffer was deallocated");
          } else {
            OS << "reallocated by call to '";
            const Stmt *S = RSCurr->getStmt();
            if (const auto *MemCallE = dyn_cast<CXXMemberCallExpr>(S)) {
              OS << MemCallE->getMethodDecl()->getDeclName();
            } else if (const auto *OpCallE = dyn_cast<CXXOperatorCallExpr>(S)) {
              OS << OpCallE->getDirectCallee()->getDeclName();
            } else if (const auto *CallE = dyn_cast<CallExpr>(S)) {
              auto &CEMgr = BRC.getStateManager().getCallEventManager();
              CallEventRef<> Call = CEMgr.getSimpleCall(CallE, state, CurrentLC);
              if (const auto *D = dyn_cast_or_null<NamedDecl>(Call->getDecl()))
                OS << D->getDeclName();
              else
                OS << "unknown";
            }
            OS << "'";
            StackHint = std::make_unique<StackHintGeneratorForSymbol>(
                Sym, "Returning; inner buffer was reallocated");
          }
          Msg = OS.str();
          break;
        }
        case AF_None:
          llvm_unreachable("Unhandled allocation family!");
      }

      // See if we're releasing memory while inlining a destructor
      // (or one of its callees). This turns on various common
      // false positive suppressions.
      bool FoundAnyDestructor = false;
      for (const LocationContext *LC = CurrentLC; LC; LC = LC->getParent()) {
        if (const auto *DD = dyn_cast<CXXDestructorDecl>(LC->getDecl())) {
          if (isReferenceCountingPointerDestructor(DD)) {
            // This immediately looks like a reference-counting destructor.
            // We're bad at guessing the original reference count of the object,
            // so suppress the report for now.
            BR.markInvalid(getTag(), DD);
          } else if (!FoundAnyDestructor) {
            assert(!ReleaseDestructorLC &&
                   "There can be only one release point!");
            // Suspect that it's a reference counting pointer destructor.
            // On one of the next nodes might find out that it has atomic
            // reference counting operations within it (see the code above),
            // and if so, we'd conclude that it likely is a reference counting
            // pointer destructor.
            ReleaseDestructorLC = LC->getStackFrame();
            // It is unlikely that releasing memory is delegated to a destructor
            // inside a destructor of a shared pointer, because it's fairly hard
            // to pass the information that the pointer indeed needs to be
            // released into it. So we're only interested in the innermost
            // destructor.
            FoundAnyDestructor = true;
          }
        }
      }
    } else if (isRelinquished(RSCurr, RSPrev, S)) {
      Msg = "Memory ownership is transferred";
      StackHint = std::make_unique<StackHintGeneratorForSymbol>(Sym, "");
    } else if (hasReallocFailed(RSCurr, RSPrev, S)) {
      Mode = ReallocationFailed;
      Msg = "Reallocation failed";
      StackHint = std::make_unique<StackHintGeneratorForReallocationFailed>(
          Sym, "Reallocation failed");

      if (SymbolRef sym = findFailedReallocSymbol(state, statePrev)) {
        // Is it possible to fail two reallocs WITHOUT testing in between?
        assert((!FailedReallocSymbol || FailedReallocSymbol == sym) &&
          "We only support one failed realloc at a time.");
        BR.markInteresting(sym);
        FailedReallocSymbol = sym;
      }
    }

  // We are in a special mode if a reallocation failed later in the path.
  } else if (Mode == ReallocationFailed) {
    assert(FailedReallocSymbol && "No symbol to look for.");

    // Is this is the first appearance of the reallocated symbol?
    if (!statePrev->get<RegionState>(FailedReallocSymbol)) {
      // We're at the reallocation point.
      Msg = "Attempt to reallocate memory";
      StackHint = std::make_unique<StackHintGeneratorForSymbol>(
          Sym, "Returned reallocated memory");
      FailedReallocSymbol = nullptr;
      Mode = Normal;
    }
  }

  if (Msg.empty()) {
    assert(!StackHint);
    return nullptr;
  }

  assert(StackHint);

  // Generate the extra diagnostic.
  PathDiagnosticLocation Pos;
  if (!S) {
    assert(RSCurr->getAllocationFamily() == AF_InnerBuffer);
    auto PostImplCall = N->getLocation().getAs<PostImplicitCall>();
    if (!PostImplCall)
      return nullptr;
    Pos = PathDiagnosticLocation(PostImplCall->getLocation(),
                                 BRC.getSourceManager());
  } else {
    Pos = PathDiagnosticLocation(S, BRC.getSourceManager(),
                                 N->getLocationContext());
  }

  auto P = std::make_shared<PathDiagnosticEventPiece>(Pos, Msg, true);
  BR.addCallStackHint(P, std::move(StackHint));
  return P;
}

void MallocChecker::printState(raw_ostream &Out, ProgramStateRef State,
                               const char *NL, const char *Sep) const {

  RegionStateTy RS = State->get<RegionState>();

  if (!RS.isEmpty()) {
    Out << Sep << "MallocChecker :" << NL;
    for (RegionStateTy::iterator I = RS.begin(), E = RS.end(); I != E; ++I) {
      const RefState *RefS = State->get<RegionState>(I.getKey());
      AllocationFamily Family = RefS->getAllocationFamily();
      Optional<MallocChecker::CheckKind> CheckKind = getCheckIfTracked(Family);
      if (!CheckKind)
        CheckKind = getCheckIfTracked(Family, true);

      I.getKey()->dumpToStream(Out);
      Out << " : ";
      I.getData().dump(Out);
      if (CheckKind)
        Out << " (" << CheckNames[*CheckKind].getName() << ")";
      Out << NL;
    }
  }
}

namespace clang {
namespace ento {
namespace allocation_state {

ProgramStateRef
markReleased(ProgramStateRef State, SymbolRef Sym, const Expr *Origin) {
  AllocationFamily Family = AF_InnerBuffer;
  return State->set<RegionState>(Sym, RefState::getReleased(Family, Origin));
}

} // end namespace allocation_state
} // end namespace ento
} // end namespace clang

// Intended to be used in InnerPointerChecker to register the part of
// MallocChecker connected to it.
void ento::registerInnerPointerCheckerAux(CheckerManager &mgr) {
  MallocChecker *checker = mgr.getChecker<MallocChecker>();
  checker->ChecksEnabled[MallocChecker::CK_InnerPointerChecker] = true;
  checker->CheckNames[MallocChecker::CK_InnerPointerChecker] =
      mgr.getCurrentCheckerName();
}

void ento::registerDynamicMemoryModeling(CheckerManager &mgr) {
  auto *checker = mgr.registerChecker<MallocChecker>();
  checker->ShouldIncludeOwnershipAnnotatedFunctions =
      mgr.getAnalyzerOptions().getCheckerBooleanOption(checker, "Optimistic");
  checker->ShouldRegisterNoOwnershipChangeVisitor =
      mgr.getAnalyzerOptions().getCheckerBooleanOption(
          checker, "AddNoOwnershipChangeNotes");
}

bool ento::shouldRegisterDynamicMemoryModeling(const CheckerManager &mgr) {
  return true;
}

#define REGISTER_CHECKER(name)                                                 \
  void ento::register##name(CheckerManager &mgr) {                             \
    MallocChecker *checker = mgr.getChecker<MallocChecker>();                  \
    checker->ChecksEnabled[MallocChecker::CK_##name] = true;                   \
    checker->CheckNames[MallocChecker::CK_##name] =                            \
        mgr.getCurrentCheckerName();                                           \
  }                                                                            \
                                                                               \
  bool ento::shouldRegister##name(const CheckerManager &mgr) { return true; }

REGISTER_CHECKER(MallocChecker)
REGISTER_CHECKER(NewDeleteChecker)
REGISTER_CHECKER(NewDeleteLeaksChecker)
REGISTER_CHECKER(MismatchedDeallocatorChecker)