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