1 //===- CXXInheritance.h - C++ Inheritance -----------------------*- C++ -*-===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file provides routines that help analyzing C++ inheritance hierarchies.
12 //===----------------------------------------------------------------------===//
14 #ifndef LLVM_CLANG_AST_CXXINHERITANCE_H
15 #define LLVM_CLANG_AST_CXXINHERITANCE_H
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"
38 /// Represents an element in a path from a derived class to a
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.
45 struct CXXBasePathElement {
46 /// The base specifier that states the link from a derived
47 /// class to a base class, which will be followed by this base
49 const CXXBaseSpecifier *Base;
51 /// The record decl of the class that the base is a base of.
52 const CXXRecordDecl *Class;
54 /// Identifies which base class subobject (of type
55 /// \c Base->getType()) this base path element refers to.
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
63 /// 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.
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.
71 class CXXBasePath : public SmallVector<CXXBasePathElement, 4> {
73 /// 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;
78 CXXBasePath() = default;
80 /// The set of declarations found inside this base class
82 DeclContext::lookup_result Decls;
85 SmallVectorImpl<CXXBasePathElement>::clear();
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:
96 /// class B : public A { };
97 /// class C : public A { };
98 /// class D : public B, public C{ };
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:
110 /// class B : public virtual A { };
111 /// class C : public virtual A { };
112 /// class D : public B, public C{ };
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.
120 friend class CXXRecordDecl;
122 /// The type from which this search originated.
123 CXXRecordDecl *Origin = nullptr;
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;
129 /// ClassSubobjects - Records the class subobjects for each class
130 /// type that we've seen. The first element IsVirtBase says
131 /// whether we found a path to a virtual base for that class type,
132 /// while NumberOfNonVirtBases 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 struct IsVirtBaseAndNumberNonVirtBases {
136 unsigned IsVirtBase : 1;
137 unsigned NumberOfNonVirtBases : 31;
139 llvm::SmallDenseMap<QualType, IsVirtBaseAndNumberNonVirtBases, 8>
142 /// VisitedDependentRecords - Records the dependent records that have been
144 llvm::SmallPtrSet<const CXXRecordDecl *, 4> VisitedDependentRecords;
146 /// DetectedVirtual - The base class that is virtual.
147 const RecordType *DetectedVirtual = nullptr;
149 /// ScratchPath - A BasePath that is used by Sema::lookupInBases
150 /// to help build the set of paths.
151 CXXBasePath ScratchPath;
153 /// 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 = 0;
159 /// FindAmbiguities - Whether Sema::IsDerivedFrom should try find
160 /// ambiguous paths while it is looking for a path from a derived
161 /// type to a base type.
162 bool FindAmbiguities;
164 /// RecordPaths - Whether Sema::IsDerivedFrom should record paths
165 /// while it is determining whether there are paths from a derived
166 /// type to a base type.
169 /// DetectVirtual - Whether Sema::IsDerivedFrom should abort the search
170 /// if it finds a path that goes across a virtual base. The virtual class
171 /// is also recorded.
174 void ComputeDeclsFound();
176 bool lookupInBases(ASTContext &Context, const CXXRecordDecl *Record,
177 CXXRecordDecl::BaseMatchesCallback BaseMatches,
178 bool LookupInDependent = false);
181 using paths_iterator = std::list<CXXBasePath>::iterator;
182 using const_paths_iterator = std::list<CXXBasePath>::const_iterator;
183 using decl_iterator = NamedDecl **;
185 /// BasePaths - Construct a new BasePaths structure to record the
186 /// paths for a derived-to-base search.
187 explicit CXXBasePaths(bool FindAmbiguities = true, bool RecordPaths = true,
188 bool DetectVirtual = true)
189 : FindAmbiguities(FindAmbiguities), RecordPaths(RecordPaths),
190 DetectVirtual(DetectVirtual) {}
192 paths_iterator begin() { return Paths.begin(); }
193 paths_iterator end() { return Paths.end(); }
194 const_paths_iterator begin() const { return Paths.begin(); }
195 const_paths_iterator end() const { return Paths.end(); }
197 CXXBasePath& front() { return Paths.front(); }
198 const CXXBasePath& front() const { return Paths.front(); }
200 using decl_range = llvm::iterator_range<decl_iterator>;
202 decl_range found_decls();
204 /// Determine whether the path from the most-derived type to the
205 /// given base type is ambiguous (i.e., it refers to multiple subobjects of
206 /// the same base type).
207 bool isAmbiguous(CanQualType BaseType);
209 /// Whether we are finding multiple paths to detect ambiguities.
210 bool isFindingAmbiguities() const { return FindAmbiguities; }
212 /// Whether we are recording paths.
213 bool isRecordingPaths() const { return RecordPaths; }
215 /// Specify whether we should be recording paths or not.
216 void setRecordingPaths(bool RP) { RecordPaths = RP; }
218 /// Whether we are detecting virtual bases.
219 bool isDetectingVirtual() const { return DetectVirtual; }
221 /// The virtual base discovered on the path (if we are merely
222 /// detecting virtuals).
223 const RecordType* getDetectedVirtual() const {
224 return DetectedVirtual;
227 /// Retrieve the type from which this base-paths search
229 CXXRecordDecl *getOrigin() const { return Origin; }
230 void setOrigin(CXXRecordDecl *Rec) { Origin = Rec; }
232 /// Clear the base-paths results.
235 /// Swap this data structure's contents with another CXXBasePaths
237 void swap(CXXBasePaths &Other);
240 /// Uniquely identifies a virtual method within a class
241 /// hierarchy by the method itself and a class subobject number.
242 struct UniqueVirtualMethod {
243 /// The overriding virtual method.
244 CXXMethodDecl *Method = nullptr;
246 /// The subobject in which the overriding virtual method
248 unsigned Subobject = 0;
250 /// The virtual base class subobject of which this overridden
251 /// virtual method is a part. Note that this records the closest
252 /// derived virtual base class subobject.
253 const CXXRecordDecl *InVirtualSubobject = nullptr;
255 UniqueVirtualMethod() = default;
257 UniqueVirtualMethod(CXXMethodDecl *Method, unsigned Subobject,
258 const CXXRecordDecl *InVirtualSubobject)
259 : Method(Method), Subobject(Subobject),
260 InVirtualSubobject(InVirtualSubobject) {}
262 friend bool operator==(const UniqueVirtualMethod &X,
263 const UniqueVirtualMethod &Y) {
264 return X.Method == Y.Method && X.Subobject == Y.Subobject &&
265 X.InVirtualSubobject == Y.InVirtualSubobject;
268 friend bool operator!=(const UniqueVirtualMethod &X,
269 const UniqueVirtualMethod &Y) {
274 /// The set of methods that override a given virtual method in
275 /// each subobject where it occurs.
277 /// The first part of the pair is the subobject in which the
278 /// overridden virtual function occurs, while the second part of the
279 /// pair is the virtual method that overrides it (including the
280 /// subobject in which that virtual function occurs).
281 class OverridingMethods {
282 using ValuesT = SmallVector<UniqueVirtualMethod, 4>;
283 using MapType = llvm::MapVector<unsigned, ValuesT>;
288 // Iterate over the set of subobjects that have overriding methods.
289 using iterator = MapType::iterator;
290 using const_iterator = MapType::const_iterator;
292 iterator begin() { return Overrides.begin(); }
293 const_iterator begin() const { return Overrides.begin(); }
294 iterator end() { return Overrides.end(); }
295 const_iterator end() const { return Overrides.end(); }
296 unsigned size() const { return Overrides.size(); }
298 // Iterate over the set of overriding virtual methods in a given
300 using overriding_iterator =
301 SmallVectorImpl<UniqueVirtualMethod>::iterator;
302 using overriding_const_iterator =
303 SmallVectorImpl<UniqueVirtualMethod>::const_iterator;
305 // Add a new overriding method for a particular subobject.
306 void add(unsigned OverriddenSubobject, UniqueVirtualMethod Overriding);
308 // Add all of the overriding methods from "other" into overrides for
309 // this method. Used when merging the overrides from multiple base
311 void add(const OverridingMethods &Other);
313 // Replace all overriding virtual methods in all subobjects with the
314 // given virtual method.
315 void replaceAll(UniqueVirtualMethod Overriding);
318 /// A mapping from each virtual member function to its set of
319 /// final overriders.
321 /// Within a class hierarchy for a given derived class, each virtual
322 /// member function in that hierarchy has one or more "final
323 /// overriders" (C++ [class.virtual]p2). A final overrider for a
324 /// virtual function "f" is the virtual function that will actually be
325 /// invoked when dispatching a call to "f" through the
326 /// vtable. Well-formed classes have a single final overrider for each
327 /// virtual function; in abstract classes, the final overrider for at
328 /// least one virtual function is a pure virtual function. Due to
329 /// multiple, virtual inheritance, it is possible for a class to have
330 /// more than one final overrider. Athough this is an error (per C++
331 /// [class.virtual]p2), it is not considered an error here: the final
332 /// overrider map can represent multiple final overriders for a
333 /// method, and it is up to the client to determine whether they are
334 /// problem. For example, the following class \c D has two final
335 /// overriders for the virtual function \c A::f(), one in \c C and one
339 /// struct A { virtual void f(); };
340 /// struct B : virtual A { virtual void f(); };
341 /// struct C : virtual A { virtual void f(); };
342 /// struct D : B, C { };
345 /// This data structure contains a mapping from every virtual
346 /// function *that does not override an existing virtual function* and
347 /// in every subobject where that virtual function occurs to the set
348 /// of virtual functions that override it. Thus, the same virtual
349 /// function \c A::f can actually occur in multiple subobjects of type
350 /// \c A due to multiple inheritance, and may be overridden by
351 /// different virtual functions in each, as in the following example:
354 /// struct A { virtual void f(); };
355 /// struct B : A { virtual void f(); };
356 /// struct C : A { virtual void f(); };
357 /// struct D : B, C { };
360 /// Unlike in the previous example, where the virtual functions \c
361 /// B::f and \c C::f both overrode \c A::f in the same subobject of
362 /// type \c A, in this example the two virtual functions both override
363 /// \c A::f but in *different* subobjects of type A. This is
364 /// represented by numbering the subobjects in which the overridden
365 /// and the overriding virtual member functions are located. Subobject
366 /// 0 represents the virtual base class subobject of that type, while
367 /// subobject numbers greater than 0 refer to non-virtual base class
368 /// subobjects of that type.
369 class CXXFinalOverriderMap
370 : public llvm::MapVector<const CXXMethodDecl *, OverridingMethods> {};
372 /// A set of all the primary bases for a class.
373 class CXXIndirectPrimaryBaseSet
374 : public llvm::SmallSet<const CXXRecordDecl*, 32> {};
378 #endif // LLVM_CLANG_AST_CXXINHERITANCE_H