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//===- CXXInheritance.h - C++ Inheritance -----------------------*- 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 provides routines that help analyzing C++ inheritance hierarchies.

//

//===----------------------------------------------------------------------===//

#ifndef LLVM_CLANG_AST_CXXINHERITANCE_H

#define LLVM_CLANG_AST_CXXINHERITANCE_H

#include "clang/AST/DeclBase.h"

#include "clang/AST/DeclCXX.h"

#include "clang/AST/DeclarationName.h"

#include "clang/AST/Type.h"

#include "clang/AST/TypeOrdering.h"

#include "clang/Basic/Specifiers.h"

#include "llvm/ADT/DenseMap.h"

#include "llvm/ADT/DenseSet.h"

#include "llvm/ADT/MapVector.h"

#include "llvm/ADT/SmallSet.h"

#include "llvm/ADT/SmallVector.h"

#include "llvm/ADT/iterator_range.h"

#include <list>

#include <memory>

#include <utility>

namespace clang {

class ASTContext;

class NamedDecl;

/// Represents an element in a path from a derived class to a

/// base class.

///

/// Each step in the path references the link from a

/// derived class to one of its direct base classes, along with a

/// base "number" that identifies which base subobject of the

/// original derived class we are referencing.

struct CXXBasePathElement {

  /// The base specifier that states the link from a derived

  /// class to a base class, which will be followed by this base

  /// path element.

  const CXXBaseSpecifier *Base;

  /// The record decl of the class that the base is a base of.

  const CXXRecordDecl *Class;

  /// Identifies which base class subobject (of type

  /// \c Base->getType()) this base path element refers to.

  ///

  /// This value is only valid if \c !Base->isVirtual(), because there

  /// is no base numbering for the zero or one virtual bases of a

  /// given type.

  int SubobjectNumber;

};

/// Represents a path from a specific derived class

/// (which is not represented as part of the path) to a particular

/// (direct or indirect) base class subobject.

///

/// Individual elements in the path are described by the \c CXXBasePathElement

/// structure, which captures both the link from a derived class to one of its

/// direct bases and identification describing which base class

/// subobject is being used.

class CXXBasePath : public SmallVector<CXXBasePathElement, 4> {

public:

  /// The access along this inheritance path.  This is only

  /// calculated when recording paths.  AS_none is a special value

  /// used to indicate a path which permits no legal access.

  AccessSpecifier Access = AS_public;

  CXXBasePath() = default;

  /// The declarations found inside this base class subobject.

  DeclContext::lookup_iterator Decls;

  void clear() {

    SmallVectorImpl<CXXBasePathElement>::clear();

    Access = AS_public;

  }

};

/// BasePaths - Represents the set of paths from a derived class to

/// one of its (direct or indirect) bases. For example, given the

/// following class hierarchy:

///

/// @code

/// class A { };

/// class B : public A { };

/// class C : public A { };

/// class D : public B, public C{ };

/// @endcode

///

/// There are two potential BasePaths to represent paths from D to a

/// base subobject of type A. One path is (D,0) -> (B,0) -> (A,0)

/// and another is (D,0)->(C,0)->(A,1). These two paths actually

/// refer to two different base class subobjects of the same type,

/// so the BasePaths object refers to an ambiguous path. On the

/// other hand, consider the following class hierarchy:

///

/// @code

/// class A { };

/// class B : public virtual A { };

/// class C : public virtual A { };

/// class D : public B, public C{ };

/// @endcode

///

/// Here, there are two potential BasePaths again, (D, 0) -> (B, 0)

/// -> (A,v) and (D, 0) -> (C, 0) -> (A, v), but since both of them

/// refer to the same base class subobject of type A (the virtual

/// one), there is no ambiguity.

class CXXBasePaths {

  friend class CXXRecordDecl;

  /// The type from which this search originated.

  const CXXRecordDecl *Origin = nullptr;

  /// Paths - The actual set of paths that can be taken from the

  /// derived class to the same base class.

  std::list<CXXBasePath> Paths;

  /// ClassSubobjects - Records the class subobjects for each class

  /// type that we've seen. The first element IsVirtBase says

  /// whether we found a path to a virtual base for that class type,

  /// while NumberOfNonVirtBases contains the number of non-virtual base

  /// class subobjects for that class type. The key of the map is

  /// the cv-unqualified canonical type of the base class subobject.

  struct IsVirtBaseAndNumberNonVirtBases {

    unsigned IsVirtBase : 1;

    unsigned NumberOfNonVirtBases : 31;

  };

  llvm::SmallDenseMap<QualType, IsVirtBaseAndNumberNonVirtBases, 8>

      ClassSubobjects;

  /// VisitedDependentRecords - Records the dependent records that have been

  /// already visited.

  llvm::SmallPtrSet<const CXXRecordDecl *, 4> VisitedDependentRecords;

  /// DetectedVirtual - The base class that is virtual.

  const RecordType *DetectedVirtual = nullptr;

  /// ScratchPath - A BasePath that is used by Sema::lookupInBases

  /// to help build the set of paths.

  CXXBasePath ScratchPath;

  /// FindAmbiguities - Whether Sema::IsDerivedFrom should try find

  /// ambiguous paths while it is looking for a path from a derived

  /// type to a base type.

  bool FindAmbiguities;

  /// RecordPaths - Whether Sema::IsDerivedFrom should record paths

  /// while it is determining whether there are paths from a derived

  /// type to a base type.

  bool RecordPaths;

  /// DetectVirtual - Whether Sema::IsDerivedFrom should abort the search

  /// if it finds a path that goes across a virtual base. The virtual class

  /// is also recorded.

  bool DetectVirtual;

  bool lookupInBases(ASTContext &Context, const CXXRecordDecl *Record,

                     CXXRecordDecl::BaseMatchesCallback BaseMatches,

                     bool LookupInDependent = false);

public:

  using paths_iterator = std::list<CXXBasePath>::iterator;

  using const_paths_iterator = std::list<CXXBasePath>::const_iterator;

  using decl_iterator = NamedDecl **;

  /// BasePaths - Construct a new BasePaths structure to record the

  /// paths for a derived-to-base search.

  explicit CXXBasePaths(bool FindAmbiguities = true, bool RecordPaths = true,

                        bool DetectVirtual = true)

      : FindAmbiguities(FindAmbiguities), RecordPaths(RecordPaths),

        DetectVirtual(DetectVirtual) {}

  paths_iterator begin() { return Paths.begin(); }

  paths_iterator end()   { return Paths.end(); }

  const_paths_iterator begin() const { return Paths.begin(); }

  const_paths_iterator end()   const { return Paths.end(); }

  CXXBasePath&       front()       { return Paths.front(); }

  const CXXBasePath& front() const { return Paths.front(); }

  using decl_range = llvm::iterator_range<decl_iterator>;

  /// Determine whether the path from the most-derived type to the

  /// given base type is ambiguous (i.e., it refers to multiple subobjects of

  /// the same base type).

  bool isAmbiguous(CanQualType BaseType);

  /// Whether we are finding multiple paths to detect ambiguities.

  bool isFindingAmbiguities() const { return FindAmbiguities; }

  /// Whether we are recording paths.

  bool isRecordingPaths() const { return RecordPaths; }

  /// Specify whether we should be recording paths or not.

  void setRecordingPaths(bool RP) { RecordPaths = RP; }

  /// Whether we are detecting virtual bases.

  bool isDetectingVirtual() const { return DetectVirtual; }

  /// The virtual base discovered on the path (if we are merely

  /// detecting virtuals).

  const RecordType* getDetectedVirtual() const {

    return DetectedVirtual;

  }

  /// Retrieve the type from which this base-paths search

  /// began

  const CXXRecordDecl *getOrigin() const { return Origin; }

  void setOrigin(const CXXRecordDecl *Rec) { Origin = Rec; }

  /// Clear the base-paths results.

  void clear();

  /// Swap this data structure's contents with another CXXBasePaths

  /// object.

  void swap(CXXBasePaths &Other);

};

/// Uniquely identifies a virtual method within a class

/// hierarchy by the method itself and a class subobject number.

struct UniqueVirtualMethod {

  /// The overriding virtual method.

  CXXMethodDecl *Method = nullptr;

  /// The subobject in which the overriding virtual method

  /// resides.

  unsigned Subobject = 0;

  /// The virtual base class subobject of which this overridden

  /// virtual method is a part. Note that this records the closest

  /// derived virtual base class subobject.

  const CXXRecordDecl *InVirtualSubobject = nullptr;

  UniqueVirtualMethod() = default;

  UniqueVirtualMethod(CXXMethodDecl *Method, unsigned Subobject,

                      const CXXRecordDecl *InVirtualSubobject)

      : Method(Method), Subobject(Subobject),

        InVirtualSubobject(InVirtualSubobject) {}

  friend bool operator==(const UniqueVirtualMethod &X,

                         const UniqueVirtualMethod &Y) {

    return X.Method == Y.Method && X.Subobject == Y.Subobject &&

      X.InVirtualSubobject == Y.InVirtualSubobject;

  }

  friend bool operator!=(const UniqueVirtualMethod &X,

                         const UniqueVirtualMethod &Y) {

    return !(X == Y);

  }

};

/// The set of methods that override a given virtual method in

/// each subobject where it occurs.

///

/// The first part of the pair is the subobject in which the

/// overridden virtual function occurs, while the second part of the

/// pair is the virtual method that overrides it (including the

/// subobject in which that virtual function occurs).

class OverridingMethods {

  using ValuesT = SmallVector<UniqueVirtualMethod, 4>;

  using MapType = llvm::MapVector<unsigned, ValuesT>;

  MapType Overrides;

public:

  // Iterate over the set of subobjects that have overriding methods.

  using iterator = MapType::iterator;

  using const_iterator = MapType::const_iterator;

  iterator begin() { return Overrides.begin(); }

  const_iterator begin() const { return Overrides.begin(); }

  iterator end() { return Overrides.end(); }

  const_iterator end() const { return Overrides.end(); }

  unsigned size() const { return Overrides.size(); }

  // Iterate over the set of overriding virtual methods in a given

  // subobject.

  using overriding_iterator =

      SmallVectorImpl<UniqueVirtualMethod>::iterator;

  using overriding_const_iterator =

      SmallVectorImpl<UniqueVirtualMethod>::const_iterator;

  // Add a new overriding method for a particular subobject.

  void add(unsigned OverriddenSubobject, UniqueVirtualMethod Overriding);

  // Add all of the overriding methods from "other" into overrides for

  // this method. Used when merging the overrides from multiple base

  // class subobjects.

  void add(const OverridingMethods &Other);

  // Replace all overriding virtual methods in all subobjects with the

  // given virtual method.

  void replaceAll(UniqueVirtualMethod Overriding);

};

/// A mapping from each virtual member function to its set of

/// final overriders.

///

/// Within a class hierarchy for a given derived class, each virtual

/// member function in that hierarchy has one or more "final

/// overriders" (C++ [class.virtual]p2). A final overrider for a

/// virtual function "f" is the virtual function that will actually be

/// invoked when dispatching a call to "f" through the

/// vtable. Well-formed classes have a single final overrider for each

/// virtual function; in abstract classes, the final overrider for at

/// least one virtual function is a pure virtual function. Due to

/// multiple, virtual inheritance, it is possible for a class to have

/// more than one final overrider. Athough this is an error (per C++

/// [class.virtual]p2), it is not considered an error here: the final

/// overrider map can represent multiple final overriders for a

/// method, and it is up to the client to determine whether they are

/// problem. For example, the following class \c D has two final

/// overriders for the virtual function \c A::f(), one in \c C and one

/// in \c D:

///

/// \code

///   struct A { virtual void f(); };

///   struct B : virtual A { virtual void f(); };

///   struct C : virtual A { virtual void f(); };

///   struct D : B, C { };

/// \endcode

///

/// This data structure contains a mapping from every virtual

/// function *that does not override an existing virtual function* and

/// in every subobject where that virtual function occurs to the set

/// of virtual functions that override it. Thus, the same virtual

/// function \c A::f can actually occur in multiple subobjects of type

/// \c A due to multiple inheritance, and may be overridden by

/// different virtual functions in each, as in the following example:

///

/// \code

///   struct A { virtual void f(); };

///   struct B : A { virtual void f(); };

///   struct C : A { virtual void f(); };

///   struct D : B, C { };

/// \endcode

///

/// Unlike in the previous example, where the virtual functions \c

/// B::f and \c C::f both overrode \c A::f in the same subobject of

/// type \c A, in this example the two virtual functions both override

/// \c A::f but in *different* subobjects of type A. This is

/// represented by numbering the subobjects in which the overridden

/// and the overriding virtual member functions are located. Subobject

/// 0 represents the virtual base class subobject of that type, while

/// subobject numbers greater than 0 refer to non-virtual base class

/// subobjects of that type.

class CXXFinalOverriderMap

  : public llvm::MapVector<const CXXMethodDecl *, OverridingMethods> {};

/// A set of all the primary bases for a class.

class CXXIndirectPrimaryBaseSet

  : public llvm::SmallSet<const CXXRecordDecl*, 32> {};

inline bool

inheritanceModelHasVBPtrOffsetField(MSInheritanceModel Inheritance) {

  return Inheritance == MSInheritanceModel::Unspecified;

}

// Only member pointers to functions need a this adjustment, since it can be

// combined with the field offset for data pointers.

inline bool inheritanceModelHasNVOffsetField(bool IsMemberFunction,

                                             MSInheritanceModel Inheritance) {

  return IsMemberFunction && Inheritance >= MSInheritanceModel::Multiple;

}

inline bool

inheritanceModelHasVBTableOffsetField(MSInheritanceModel Inheritance) {

  return Inheritance >= MSInheritanceModel::Virtual;

}

inline bool inheritanceModelHasOnlyOneField(bool IsMemberFunction,

                                            MSInheritanceModel Inheritance) {

  if (IsMemberFunction)

    return Inheritance <= MSInheritanceModel::Single;

  return Inheritance <= MSInheritanceModel::Multiple;

}

} // namespace clang

#endif // LLVM_CLANG_AST_CXXINHERITANCE_H