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