1//===- CXXInheritance.h - C++ Inheritance -----------------------*- C++ -*-===// 2// 3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 4// See https://llvm.org/LICENSE.txt for license information. 5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 6// 7//===----------------------------------------------------------------------===// 8// 9// This file provides routines that help analyzing C++ inheritance hierarchies. 10// 11//===----------------------------------------------------------------------===// 12 13#ifndef LLVM_CLANG_AST_CXXINHERITANCE_H 14#define LLVM_CLANG_AST_CXXINHERITANCE_H 15 16#include "clang/AST/DeclBase.h" 17#include "clang/AST/DeclCXX.h" 18#include "clang/AST/DeclarationName.h" 19#include "clang/AST/Type.h" 20#include "clang/AST/TypeOrdering.h" 21#include "clang/Basic/Specifiers.h" 22#include "llvm/ADT/DenseMap.h" 23#include "llvm/ADT/DenseSet.h" 24#include "llvm/ADT/MapVector.h" 25#include "llvm/ADT/SmallSet.h" 26#include "llvm/ADT/SmallVector.h" 27#include "llvm/ADT/iterator_range.h" 28#include <list> 29#include <memory> 30#include <utility> 31 32namespace clang { 33 34class ASTContext; 35class NamedDecl; 36 37/// Represents an element in a path from a derived class to a 38/// base class. 39/// 40/// Each step in the path references the link from a 41/// derived class to one of its direct base classes, along with a 42/// base "number" that identifies which base subobject of the 43/// original derived class we are referencing. 44struct CXXBasePathElement { 45 /// The base specifier that states the link from a derived 46 /// class to a base class, which will be followed by this base 47 /// path element. 48 const CXXBaseSpecifier *Base; 49 50 /// The record decl of the class that the base is a base of. 51 const CXXRecordDecl *Class; 52 53 /// Identifies which base class subobject (of type 54 /// \c Base->getType()) this base path element refers to. 55 /// 56 /// This value is only valid if \c !Base->isVirtual(), because there 57 /// is no base numbering for the zero or one virtual bases of a 58 /// given type. 59 int SubobjectNumber; 60}; 61 62/// Represents a path from a specific derived class 63/// (which is not represented as part of the path) to a particular 64/// (direct or indirect) base class subobject. 65/// 66/// Individual elements in the path are described by the \c CXXBasePathElement 67/// structure, which captures both the link from a derived class to one of its 68/// direct bases and identification describing which base class 69/// subobject is being used. 70class CXXBasePath : public SmallVector<CXXBasePathElement, 4> { 71public: 72 /// The access along this inheritance path. This is only 73 /// calculated when recording paths. AS_none is a special value 74 /// used to indicate a path which permits no legal access. 75 AccessSpecifier Access = AS_public; 76 77 CXXBasePath() = default; 78 79 /// The set of declarations found inside this base class 80 /// subobject. 81 DeclContext::lookup_result Decls; 82 83 void clear() { 84 SmallVectorImpl<CXXBasePathElement>::clear(); 85 Access = AS_public; 86 } 87}; 88 89/// BasePaths - Represents the set of paths from a derived class to 90/// one of its (direct or indirect) bases. For example, given the 91/// following class hierarchy: 92/// 93/// @code 94/// class A { }; 95/// class B : public A { }; 96/// class C : public A { }; 97/// class D : public B, public C{ }; 98/// @endcode 99/// 100/// There are two potential BasePaths to represent paths from D to a 101/// base subobject of type A. One path is (D,0) -> (B,0) -> (A,0) 102/// and another is (D,0)->(C,0)->(A,1). These two paths actually 103/// refer to two different base class subobjects of the same type, 104/// so the BasePaths object refers to an ambiguous path. On the 105/// other hand, consider the following class hierarchy: 106/// 107/// @code 108/// class A { }; 109/// class B : public virtual A { }; 110/// class C : public virtual A { }; 111/// class D : public B, public C{ }; 112/// @endcode 113/// 114/// Here, there are two potential BasePaths again, (D, 0) -> (B, 0) 115/// -> (A,v) and (D, 0) -> (C, 0) -> (A, v), but since both of them 116/// refer to the same base class subobject of type A (the virtual 117/// one), there is no ambiguity. 118class CXXBasePaths { 119 friend class CXXRecordDecl; 120 121 /// The type from which this search originated. 122 CXXRecordDecl *Origin = nullptr; 123 124 /// Paths - The actual set of paths that can be taken from the 125 /// derived class to the same base class. 126 std::list<CXXBasePath> Paths; 127 128 /// ClassSubobjects - Records the class subobjects for each class 129 /// type that we've seen. The first element IsVirtBase says 130 /// whether we found a path to a virtual base for that class type, 131 /// while NumberOfNonVirtBases contains the number of non-virtual base 132 /// class subobjects for that class type. The key of the map is 133 /// the cv-unqualified canonical type of the base class subobject. 134 struct IsVirtBaseAndNumberNonVirtBases { 135 unsigned IsVirtBase : 1; 136 unsigned NumberOfNonVirtBases : 31; 137 }; 138 llvm::SmallDenseMap<QualType, IsVirtBaseAndNumberNonVirtBases, 8> 139 ClassSubobjects; 140 141 /// VisitedDependentRecords - Records the dependent records that have been 142 /// already visited. 143 llvm::SmallPtrSet<const CXXRecordDecl *, 4> VisitedDependentRecords; 144 145 /// DetectedVirtual - The base class that is virtual. 146 const RecordType *DetectedVirtual = nullptr; 147 148 /// ScratchPath - A BasePath that is used by Sema::lookupInBases 149 /// to help build the set of paths. 150 CXXBasePath ScratchPath; 151 152 /// Array of the declarations that have been found. This 153 /// array is constructed only if needed, e.g., to iterate over the 154 /// results within LookupResult. 155 std::unique_ptr<NamedDecl *[]> DeclsFound; 156 unsigned NumDeclsFound = 0; 157 158 /// FindAmbiguities - Whether Sema::IsDerivedFrom should try find 159 /// ambiguous paths while it is looking for a path from a derived 160 /// type to a base type. 161 bool FindAmbiguities; 162 163 /// RecordPaths - Whether Sema::IsDerivedFrom should record paths 164 /// while it is determining whether there are paths from a derived 165 /// type to a base type. 166 bool RecordPaths; 167 168 /// DetectVirtual - Whether Sema::IsDerivedFrom should abort the search 169 /// if it finds a path that goes across a virtual base. The virtual class 170 /// is also recorded. 171 bool DetectVirtual; 172 173 void ComputeDeclsFound(); 174 175 bool lookupInBases(ASTContext &Context, const CXXRecordDecl *Record, 176 CXXRecordDecl::BaseMatchesCallback BaseMatches, 177 bool LookupInDependent = false); 178 179public: 180 using paths_iterator = std::list<CXXBasePath>::iterator; 181 using const_paths_iterator = std::list<CXXBasePath>::const_iterator; 182 using decl_iterator = NamedDecl **; 183 184 /// BasePaths - Construct a new BasePaths structure to record the 185 /// paths for a derived-to-base search. 186 explicit CXXBasePaths(bool FindAmbiguities = true, bool RecordPaths = true, 187 bool DetectVirtual = true) 188 : FindAmbiguities(FindAmbiguities), RecordPaths(RecordPaths), 189 DetectVirtual(DetectVirtual) {} 190 191 paths_iterator begin() { return Paths.begin(); } 192 paths_iterator end() { return Paths.end(); } 193 const_paths_iterator begin() const { return Paths.begin(); } 194 const_paths_iterator end() const { return Paths.end(); } 195 196 CXXBasePath& front() { return Paths.front(); } 197 const CXXBasePath& front() const { return Paths.front(); } 198 199 using decl_range = llvm::iterator_range<decl_iterator>; 200 201 decl_range found_decls(); 202 203 /// Determine whether the path from the most-derived type to the 204 /// given base type is ambiguous (i.e., it refers to multiple subobjects of 205 /// the same base type). 206 bool isAmbiguous(CanQualType BaseType); 207 208 /// Whether we are finding multiple paths to detect ambiguities. 209 bool isFindingAmbiguities() const { return FindAmbiguities; } 210 211 /// Whether we are recording paths. 212 bool isRecordingPaths() const { return RecordPaths; } 213 214 /// Specify whether we should be recording paths or not. 215 void setRecordingPaths(bool RP) { RecordPaths = RP; } 216 217 /// Whether we are detecting virtual bases. 218 bool isDetectingVirtual() const { return DetectVirtual; } 219 220 /// The virtual base discovered on the path (if we are merely 221 /// detecting virtuals). 222 const RecordType* getDetectedVirtual() const { 223 return DetectedVirtual; 224 } 225 226 /// Retrieve the type from which this base-paths search 227 /// began 228 CXXRecordDecl *getOrigin() const { return Origin; } 229 void setOrigin(CXXRecordDecl *Rec) { Origin = Rec; } 230 231 /// Clear the base-paths results. 232 void clear(); 233 234 /// Swap this data structure's contents with another CXXBasePaths 235 /// object. 236 void swap(CXXBasePaths &Other); 237}; 238 239/// Uniquely identifies a virtual method within a class 240/// hierarchy by the method itself and a class subobject number. 241struct UniqueVirtualMethod { 242 /// The overriding virtual method. 243 CXXMethodDecl *Method = nullptr; 244 245 /// The subobject in which the overriding virtual method 246 /// resides. 247 unsigned Subobject = 0; 248 249 /// The virtual base class subobject of which this overridden 250 /// virtual method is a part. Note that this records the closest 251 /// derived virtual base class subobject. 252 const CXXRecordDecl *InVirtualSubobject = nullptr; 253 254 UniqueVirtualMethod() = default; 255 256 UniqueVirtualMethod(CXXMethodDecl *Method, unsigned Subobject, 257 const CXXRecordDecl *InVirtualSubobject) 258 : Method(Method), Subobject(Subobject), 259 InVirtualSubobject(InVirtualSubobject) {} 260 261 friend bool operator==(const UniqueVirtualMethod &X, 262 const UniqueVirtualMethod &Y) { 263 return X.Method == Y.Method && X.Subobject == Y.Subobject && 264 X.InVirtualSubobject == Y.InVirtualSubobject; 265 } 266 267 friend bool operator!=(const UniqueVirtualMethod &X, 268 const UniqueVirtualMethod &Y) { 269 return !(X == Y); 270 } 271}; 272 273/// The set of methods that override a given virtual method in 274/// each subobject where it occurs. 275/// 276/// The first part of the pair is the subobject in which the 277/// overridden virtual function occurs, while the second part of the 278/// pair is the virtual method that overrides it (including the 279/// subobject in which that virtual function occurs). 280class OverridingMethods { 281 using ValuesT = SmallVector<UniqueVirtualMethod, 4>; 282 using MapType = llvm::MapVector<unsigned, ValuesT>; 283 284 MapType Overrides; 285 286public: 287 // Iterate over the set of subobjects that have overriding methods. 288 using iterator = MapType::iterator; 289 using const_iterator = MapType::const_iterator; 290 291 iterator begin() { return Overrides.begin(); } 292 const_iterator begin() const { return Overrides.begin(); } 293 iterator end() { return Overrides.end(); } 294 const_iterator end() const { return Overrides.end(); } 295 unsigned size() const { return Overrides.size(); } 296 297 // Iterate over the set of overriding virtual methods in a given 298 // subobject. 299 using overriding_iterator = 300 SmallVectorImpl<UniqueVirtualMethod>::iterator; 301 using overriding_const_iterator = 302 SmallVectorImpl<UniqueVirtualMethod>::const_iterator; 303 304 // Add a new overriding method for a particular subobject. 305 void add(unsigned OverriddenSubobject, UniqueVirtualMethod Overriding); 306 307 // Add all of the overriding methods from "other" into overrides for 308 // this method. Used when merging the overrides from multiple base 309 // class subobjects. 310 void add(const OverridingMethods &Other); 311 312 // Replace all overriding virtual methods in all subobjects with the 313 // given virtual method. 314 void replaceAll(UniqueVirtualMethod Overriding); 315}; 316 317/// A mapping from each virtual member function to its set of 318/// final overriders. 319/// 320/// Within a class hierarchy for a given derived class, each virtual 321/// member function in that hierarchy has one or more "final 322/// overriders" (C++ [class.virtual]p2). A final overrider for a 323/// virtual function "f" is the virtual function that will actually be 324/// invoked when dispatching a call to "f" through the 325/// vtable. Well-formed classes have a single final overrider for each 326/// virtual function; in abstract classes, the final overrider for at 327/// least one virtual function is a pure virtual function. Due to 328/// multiple, virtual inheritance, it is possible for a class to have 329/// more than one final overrider. Athough this is an error (per C++ 330/// [class.virtual]p2), it is not considered an error here: the final 331/// overrider map can represent multiple final overriders for a 332/// method, and it is up to the client to determine whether they are 333/// problem. For example, the following class \c D has two final 334/// overriders for the virtual function \c A::f(), one in \c C and one 335/// in \c D: 336/// 337/// \code 338/// struct A { virtual void f(); }; 339/// struct B : virtual A { virtual void f(); }; 340/// struct C : virtual A { virtual void f(); }; 341/// struct D : B, C { }; 342/// \endcode 343/// 344/// This data structure contains a mapping from every virtual 345/// function *that does not override an existing virtual function* and 346/// in every subobject where that virtual function occurs to the set 347/// of virtual functions that override it. Thus, the same virtual 348/// function \c A::f can actually occur in multiple subobjects of type 349/// \c A due to multiple inheritance, and may be overridden by 350/// different virtual functions in each, as in the following example: 351/// 352/// \code 353/// struct A { virtual void f(); }; 354/// struct B : A { virtual void f(); }; 355/// struct C : A { virtual void f(); }; 356/// struct D : B, C { }; 357/// \endcode 358/// 359/// Unlike in the previous example, where the virtual functions \c 360/// B::f and \c C::f both overrode \c A::f in the same subobject of 361/// type \c A, in this example the two virtual functions both override 362/// \c A::f but in *different* subobjects of type A. This is 363/// represented by numbering the subobjects in which the overridden 364/// and the overriding virtual member functions are located. Subobject 365/// 0 represents the virtual base class subobject of that type, while 366/// subobject numbers greater than 0 refer to non-virtual base class 367/// subobjects of that type. 368class CXXFinalOverriderMap 369 : public llvm::MapVector<const CXXMethodDecl *, OverridingMethods> {}; 370 371/// A set of all the primary bases for a class. 372class CXXIndirectPrimaryBaseSet 373 : public llvm::SmallSet<const CXXRecordDecl*, 32> {}; 374 375inline bool 376inheritanceModelHasVBPtrOffsetField(MSInheritanceModel Inheritance) { 377 return Inheritance == MSInheritanceModel::Unspecified; 378} 379 380// Only member pointers to functions need a this adjustment, since it can be 381// combined with the field offset for data pointers. 382inline bool inheritanceModelHasNVOffsetField(bool IsMemberFunction, 383 MSInheritanceModel Inheritance) { 384 return IsMemberFunction && Inheritance >= MSInheritanceModel::Multiple; 385} 386 387inline bool 388inheritanceModelHasVBTableOffsetField(MSInheritanceModel Inheritance) { 389 return Inheritance >= MSInheritanceModel::Virtual; 390} 391 392inline bool inheritanceModelHasOnlyOneField(bool IsMemberFunction, 393 MSInheritanceModel Inheritance) { 394 if (IsMemberFunction) 395 return Inheritance <= MSInheritanceModel::Single; 396 return Inheritance <= MSInheritanceModel::Multiple; 397} 398 399} // namespace clang 400 401#endif // LLVM_CLANG_AST_CXXINHERITANCE_H 402