CXXInheritance.h revision 327952
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 "clang/Basic/Specifiers.h" 23#include "llvm/ADT/DenseMap.h" 24#include "llvm/ADT/DenseSet.h" 25#include "llvm/ADT/MapVector.h" 26#include "llvm/ADT/SmallSet.h" 27#include "llvm/ADT/SmallVector.h" 28#include "llvm/ADT/iterator_range.h" 29#include <list> 30#include <memory> 31#include <utility> 32 33namespace clang { 34 35class ASTContext; 36class NamedDecl; 37 38/// \brief Represents an element in a path from a derived class to a 39/// base class. 40/// 41/// Each step in the path references the link from a 42/// derived class to one of its direct base classes, along with a 43/// base "number" that identifies which base subobject of the 44/// original derived class we are referencing. 45struct CXXBasePathElement { 46 /// \brief The base specifier that states the link from a derived 47 /// class to a base class, which will be followed by this base 48 /// path element. 49 const CXXBaseSpecifier *Base; 50 51 /// \brief The record decl of the class that the base is a base of. 52 const CXXRecordDecl *Class; 53 54 /// \brief Identifies which base class subobject (of type 55 /// \c Base->getType()) this base path element refers to. 56 /// 57 /// This value is only valid if \c !Base->isVirtual(), because there 58 /// is no base numbering for the zero or one virtual bases of a 59 /// given type. 60 int SubobjectNumber; 61}; 62 63/// \brief Represents a path from a specific derived class 64/// (which is not represented as part of the path) to a particular 65/// (direct or indirect) base class subobject. 66/// 67/// Individual elements in the path are described by the \c CXXBasePathElement 68/// structure, which captures both the link from a derived class to one of its 69/// direct bases and identification describing which base class 70/// subobject is being used. 71class CXXBasePath : public SmallVector<CXXBasePathElement, 4> { 72public: 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 = AS_public; 77 78 CXXBasePath() = default; 79 80 /// \brief The set of declarations found inside this base class 81 /// subobject. 82 DeclContext::lookup_result Decls; 83 84 void clear() { 85 SmallVectorImpl<CXXBasePathElement>::clear(); 86 Access = AS_public; 87 } 88}; 89 90/// BasePaths - Represents the set of paths from a derived class to 91/// one of its (direct or indirect) bases. For example, given the 92/// following class hierarchy: 93/// 94/// @code 95/// class A { }; 96/// class B : public A { }; 97/// class C : public A { }; 98/// class D : public B, public C{ }; 99/// @endcode 100/// 101/// There are two potential BasePaths to represent paths from D to a 102/// base subobject of type A. One path is (D,0) -> (B,0) -> (A,0) 103/// and another is (D,0)->(C,0)->(A,1). These two paths actually 104/// refer to two different base class subobjects of the same type, 105/// so the BasePaths object refers to an ambiguous path. On the 106/// other hand, consider the following class hierarchy: 107/// 108/// @code 109/// class A { }; 110/// class B : public virtual A { }; 111/// class C : public virtual A { }; 112/// class D : public B, public C{ }; 113/// @endcode 114/// 115/// Here, there are two potential BasePaths again, (D, 0) -> (B, 0) 116/// -> (A,v) and (D, 0) -> (C, 0) -> (A, v), but since both of them 117/// refer to the same base class subobject of type A (the virtual 118/// one), there is no ambiguity. 119class CXXBasePaths { 120 friend class CXXRecordDecl; 121 122 /// \brief The type from which this search originated. 123 CXXRecordDecl *Origin = nullptr; 124 125 /// Paths - The actual set of paths that can be taken from the 126 /// derived class to the same base class. 127 std::list<CXXBasePath> Paths; 128 129 /// ClassSubobjects - Records the class subobjects for each class 130 /// type that we've seen. The first element in the pair says 131 /// whether we found a path to a virtual base for that class type, 132 /// while the element contains the number of non-virtual base 133 /// class subobjects for that class type. The key of the map is 134 /// the cv-unqualified canonical type of the base class subobject. 135 llvm::SmallDenseMap<QualType, std::pair<bool, unsigned>, 8> ClassSubobjects; 136 137 /// VisitedDependentRecords - Records the dependent records that have been 138 /// already visited. 139 llvm::SmallDenseSet<const CXXRecordDecl *, 4> VisitedDependentRecords; 140 141 /// FindAmbiguities - Whether Sema::IsDerivedFrom should try find 142 /// ambiguous paths while it is looking for a path from a derived 143 /// type to a base type. 144 bool FindAmbiguities; 145 146 /// RecordPaths - Whether Sema::IsDerivedFrom should record paths 147 /// while it is determining whether there are paths from a derived 148 /// type to a base type. 149 bool RecordPaths; 150 151 /// DetectVirtual - Whether Sema::IsDerivedFrom should abort the search 152 /// if it finds a path that goes across a virtual base. The virtual class 153 /// is also recorded. 154 bool DetectVirtual; 155 156 /// ScratchPath - A BasePath that is used by Sema::lookupInBases 157 /// to help build the set of paths. 158 CXXBasePath ScratchPath; 159 160 /// DetectedVirtual - The base class that is virtual. 161 const RecordType *DetectedVirtual = nullptr; 162 163 /// \brief Array of the declarations that have been found. This 164 /// array is constructed only if needed, e.g., to iterate over the 165 /// results within LookupResult. 166 std::unique_ptr<NamedDecl *[]> DeclsFound; 167 unsigned NumDeclsFound = 0; 168 169 void ComputeDeclsFound(); 170 171 bool lookupInBases(ASTContext &Context, const CXXRecordDecl *Record, 172 CXXRecordDecl::BaseMatchesCallback BaseMatches, 173 bool LookupInDependent = false); 174 175public: 176 using paths_iterator = std::list<CXXBasePath>::iterator; 177 using const_paths_iterator = std::list<CXXBasePath>::const_iterator; 178 using decl_iterator = NamedDecl **; 179 180 /// BasePaths - Construct a new BasePaths structure to record the 181 /// paths for a derived-to-base search. 182 explicit CXXBasePaths(bool FindAmbiguities = true, bool RecordPaths = true, 183 bool DetectVirtual = true) 184 : FindAmbiguities(FindAmbiguities), RecordPaths(RecordPaths), 185 DetectVirtual(DetectVirtual) {} 186 187 paths_iterator begin() { return Paths.begin(); } 188 paths_iterator end() { return Paths.end(); } 189 const_paths_iterator begin() const { return Paths.begin(); } 190 const_paths_iterator end() const { return Paths.end(); } 191 192 CXXBasePath& front() { return Paths.front(); } 193 const CXXBasePath& front() const { return Paths.front(); } 194 195 using decl_range = llvm::iterator_range<decl_iterator>; 196 197 decl_range found_decls(); 198 199 /// \brief Determine whether the path from the most-derived type to the 200 /// given base type is ambiguous (i.e., it refers to multiple subobjects of 201 /// the same base type). 202 bool isAmbiguous(CanQualType BaseType); 203 204 /// \brief Whether we are finding multiple paths to detect ambiguities. 205 bool isFindingAmbiguities() const { return FindAmbiguities; } 206 207 /// \brief Whether we are recording paths. 208 bool isRecordingPaths() const { return RecordPaths; } 209 210 /// \brief Specify whether we should be recording paths or not. 211 void setRecordingPaths(bool RP) { RecordPaths = RP; } 212 213 /// \brief Whether we are detecting virtual bases. 214 bool isDetectingVirtual() const { return DetectVirtual; } 215 216 /// \brief The virtual base discovered on the path (if we are merely 217 /// detecting virtuals). 218 const RecordType* getDetectedVirtual() const { 219 return DetectedVirtual; 220 } 221 222 /// \brief Retrieve the type from which this base-paths search 223 /// began 224 CXXRecordDecl *getOrigin() const { return Origin; } 225 void setOrigin(CXXRecordDecl *Rec) { Origin = Rec; } 226 227 /// \brief Clear the base-paths results. 228 void clear(); 229 230 /// \brief Swap this data structure's contents with another CXXBasePaths 231 /// object. 232 void swap(CXXBasePaths &Other); 233}; 234 235/// \brief Uniquely identifies a virtual method within a class 236/// hierarchy by the method itself and a class subobject number. 237struct UniqueVirtualMethod { 238 /// \brief The overriding virtual method. 239 CXXMethodDecl *Method = nullptr; 240 241 /// \brief The subobject in which the overriding virtual method 242 /// resides. 243 unsigned Subobject = 0; 244 245 /// \brief The virtual base class subobject of which this overridden 246 /// virtual method is a part. Note that this records the closest 247 /// derived virtual base class subobject. 248 const CXXRecordDecl *InVirtualSubobject = nullptr; 249 250 UniqueVirtualMethod() = default; 251 252 UniqueVirtualMethod(CXXMethodDecl *Method, unsigned Subobject, 253 const CXXRecordDecl *InVirtualSubobject) 254 : Method(Method), Subobject(Subobject), 255 InVirtualSubobject(InVirtualSubobject) {} 256 257 friend bool operator==(const UniqueVirtualMethod &X, 258 const UniqueVirtualMethod &Y) { 259 return X.Method == Y.Method && X.Subobject == Y.Subobject && 260 X.InVirtualSubobject == Y.InVirtualSubobject; 261 } 262 263 friend bool operator!=(const UniqueVirtualMethod &X, 264 const UniqueVirtualMethod &Y) { 265 return !(X == Y); 266 } 267}; 268 269/// \brief The set of methods that override a given virtual method in 270/// each subobject where it occurs. 271/// 272/// The first part of the pair is the subobject in which the 273/// overridden virtual function occurs, while the second part of the 274/// pair is the virtual method that overrides it (including the 275/// subobject in which that virtual function occurs). 276class OverridingMethods { 277 using ValuesT = SmallVector<UniqueVirtualMethod, 4>; 278 using MapType = llvm::MapVector<unsigned, ValuesT>; 279 280 MapType Overrides; 281 282public: 283 // Iterate over the set of subobjects that have overriding methods. 284 using iterator = MapType::iterator; 285 using const_iterator = MapType::const_iterator; 286 287 iterator begin() { return Overrides.begin(); } 288 const_iterator begin() const { return Overrides.begin(); } 289 iterator end() { return Overrides.end(); } 290 const_iterator end() const { return Overrides.end(); } 291 unsigned size() const { return Overrides.size(); } 292 293 // Iterate over the set of overriding virtual methods in a given 294 // subobject. 295 using overriding_iterator = 296 SmallVectorImpl<UniqueVirtualMethod>::iterator; 297 using overriding_const_iterator = 298 SmallVectorImpl<UniqueVirtualMethod>::const_iterator; 299 300 // Add a new overriding method for a particular subobject. 301 void add(unsigned OverriddenSubobject, UniqueVirtualMethod Overriding); 302 303 // Add all of the overriding methods from "other" into overrides for 304 // this method. Used when merging the overrides from multiple base 305 // class subobjects. 306 void add(const OverridingMethods &Other); 307 308 // Replace all overriding virtual methods in all subobjects with the 309 // given virtual method. 310 void replaceAll(UniqueVirtualMethod Overriding); 311}; 312 313/// \brief A mapping from each virtual member function to its set of 314/// final overriders. 315/// 316/// Within a class hierarchy for a given derived class, each virtual 317/// member function in that hierarchy has one or more "final 318/// overriders" (C++ [class.virtual]p2). A final overrider for a 319/// virtual function "f" is the virtual function that will actually be 320/// invoked when dispatching a call to "f" through the 321/// vtable. Well-formed classes have a single final overrider for each 322/// virtual function; in abstract classes, the final overrider for at 323/// least one virtual function is a pure virtual function. Due to 324/// multiple, virtual inheritance, it is possible for a class to have 325/// more than one final overrider. Athough this is an error (per C++ 326/// [class.virtual]p2), it is not considered an error here: the final 327/// overrider map can represent multiple final overriders for a 328/// method, and it is up to the client to determine whether they are 329/// problem. For example, the following class \c D has two final 330/// overriders for the virtual function \c A::f(), one in \c C and one 331/// in \c D: 332/// 333/// \code 334/// struct A { virtual void f(); }; 335/// struct B : virtual A { virtual void f(); }; 336/// struct C : virtual A { virtual void f(); }; 337/// struct D : B, C { }; 338/// \endcode 339/// 340/// This data structure contains a mapping from every virtual 341/// function *that does not override an existing virtual function* and 342/// in every subobject where that virtual function occurs to the set 343/// of virtual functions that override it. Thus, the same virtual 344/// function \c A::f can actually occur in multiple subobjects of type 345/// \c A due to multiple inheritance, and may be overridden by 346/// different virtual functions in each, as in the following example: 347/// 348/// \code 349/// struct A { virtual void f(); }; 350/// struct B : A { virtual void f(); }; 351/// struct C : A { virtual void f(); }; 352/// struct D : B, C { }; 353/// \endcode 354/// 355/// Unlike in the previous example, where the virtual functions \c 356/// B::f and \c C::f both overrode \c A::f in the same subobject of 357/// type \c A, in this example the two virtual functions both override 358/// \c A::f but in *different* subobjects of type A. This is 359/// represented by numbering the subobjects in which the overridden 360/// and the overriding virtual member functions are located. Subobject 361/// 0 represents the virtual base class subobject of that type, while 362/// subobject numbers greater than 0 refer to non-virtual base class 363/// subobjects of that type. 364class CXXFinalOverriderMap 365 : public llvm::MapVector<const CXXMethodDecl *, OverridingMethods> {}; 366 367/// \brief A set of all the primary bases for a class. 368class CXXIndirectPrimaryBaseSet 369 : public llvm::SmallSet<const CXXRecordDecl*, 32> {}; 370 371} // namespace clang 372 373#endif // LLVM_CLANG_AST_CXXINHERITANCE_H 374