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/MapVector.h" |
24 | #include "llvm/ADT/SmallSet.h" |
25 | #include "llvm/ADT/SmallVector.h" |
26 | #include "llvm/ADT/iterator_range.h" |
27 | #include <list> |
28 | #include <memory> |
29 | #include <utility> |
30 | |
31 | namespace clang { |
32 | |
33 | class ASTContext; |
34 | class NamedDecl; |
35 | |
36 | /// 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 | /// 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 | /// The record decl of the class that the base is a base of. |
50 | const CXXRecordDecl *Class; |
51 | |
52 | /// 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 | /// 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 | /// 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 = AS_public; |
75 | |
76 | CXXBasePath() = default; |
77 | |
78 | /// The declarations found inside this base class subobject. |
79 | DeclContext::lookup_iterator Decls; |
80 | |
81 | void clear() { |
82 | SmallVectorImpl<CXXBasePathElement>::clear(); |
83 | Access = AS_public; |
84 | } |
85 | }; |
86 | |
87 | /// BasePaths - Represents the set of paths from a derived class to |
88 | /// one of its (direct or indirect) bases. For example, given the |
89 | /// following class hierarchy: |
90 | /// |
91 | /// @code |
92 | /// class A { }; |
93 | /// class B : public A { }; |
94 | /// class C : public A { }; |
95 | /// class D : public B, public C{ }; |
96 | /// @endcode |
97 | /// |
98 | /// There are two potential BasePaths to represent paths from D to a |
99 | /// base subobject of type A. One path is (D,0) -> (B,0) -> (A,0) |
100 | /// and another is (D,0)->(C,0)->(A,1). These two paths actually |
101 | /// refer to two different base class subobjects of the same type, |
102 | /// so the BasePaths object refers to an ambiguous path. On the |
103 | /// other hand, consider the following class hierarchy: |
104 | /// |
105 | /// @code |
106 | /// class A { }; |
107 | /// class B : public virtual A { }; |
108 | /// class C : public virtual A { }; |
109 | /// class D : public B, public C{ }; |
110 | /// @endcode |
111 | /// |
112 | /// Here, there are two potential BasePaths again, (D, 0) -> (B, 0) |
113 | /// -> (A,v) and (D, 0) -> (C, 0) -> (A, v), but since both of them |
114 | /// refer to the same base class subobject of type A (the virtual |
115 | /// one), there is no ambiguity. |
116 | class CXXBasePaths { |
117 | friend class CXXRecordDecl; |
118 | |
119 | /// The type from which this search originated. |
120 | const CXXRecordDecl *Origin = nullptr; |
121 | |
122 | /// Paths - The actual set of paths that can be taken from the |
123 | /// derived class to the same base class. |
124 | std::list<CXXBasePath> Paths; |
125 | |
126 | /// ClassSubobjects - Records the class subobjects for each class |
127 | /// type that we've seen. The first element IsVirtBase says |
128 | /// whether we found a path to a virtual base for that class type, |
129 | /// while NumberOfNonVirtBases contains the number of non-virtual base |
130 | /// class subobjects for that class type. The key of the map is |
131 | /// the cv-unqualified canonical type of the base class subobject. |
132 | struct IsVirtBaseAndNumberNonVirtBases { |
133 | LLVM_PREFERRED_TYPE(bool) |
134 | unsigned IsVirtBase : 1; |
135 | unsigned NumberOfNonVirtBases : 31; |
136 | }; |
137 | llvm::SmallDenseMap<QualType, IsVirtBaseAndNumberNonVirtBases, 8> |
138 | ClassSubobjects; |
139 | |
140 | /// VisitedDependentRecords - Records the dependent records that have been |
141 | /// already visited. |
142 | llvm::SmallPtrSet<const CXXRecordDecl *, 4> VisitedDependentRecords; |
143 | |
144 | /// DetectedVirtual - The base class that is virtual. |
145 | const RecordType *DetectedVirtual = nullptr; |
146 | |
147 | /// ScratchPath - A BasePath that is used by Sema::lookupInBases |
148 | /// to help build the set of paths. |
149 | CXXBasePath ScratchPath; |
150 | |
151 | /// FindAmbiguities - Whether Sema::IsDerivedFrom should try find |
152 | /// ambiguous paths while it is looking for a path from a derived |
153 | /// type to a base type. |
154 | bool FindAmbiguities; |
155 | |
156 | /// RecordPaths - Whether Sema::IsDerivedFrom should record paths |
157 | /// while it is determining whether there are paths from a derived |
158 | /// type to a base type. |
159 | bool RecordPaths; |
160 | |
161 | /// DetectVirtual - Whether Sema::IsDerivedFrom should abort the search |
162 | /// if it finds a path that goes across a virtual base. The virtual class |
163 | /// is also recorded. |
164 | bool DetectVirtual; |
165 | |
166 | bool lookupInBases(ASTContext &Context, const CXXRecordDecl *Record, |
167 | CXXRecordDecl::BaseMatchesCallback BaseMatches, |
168 | bool LookupInDependent = false); |
169 | |
170 | public: |
171 | using paths_iterator = std::list<CXXBasePath>::iterator; |
172 | using const_paths_iterator = std::list<CXXBasePath>::const_iterator; |
173 | using decl_iterator = NamedDecl **; |
174 | |
175 | /// BasePaths - Construct a new BasePaths structure to record the |
176 | /// paths for a derived-to-base search. |
177 | explicit CXXBasePaths(bool FindAmbiguities = true, bool RecordPaths = true, |
178 | bool DetectVirtual = true) |
179 | : FindAmbiguities(FindAmbiguities), RecordPaths(RecordPaths), |
180 | DetectVirtual(DetectVirtual) {} |
181 | |
182 | paths_iterator begin() { return Paths.begin(); } |
183 | paths_iterator end() { return Paths.end(); } |
184 | const_paths_iterator begin() const { return Paths.begin(); } |
185 | const_paths_iterator end() const { return Paths.end(); } |
186 | |
187 | CXXBasePath& front() { return Paths.front(); } |
188 | const CXXBasePath& front() const { return Paths.front(); } |
189 | |
190 | using decl_range = llvm::iterator_range<decl_iterator>; |
191 | |
192 | /// 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 | /// Whether we are finding multiple paths to detect ambiguities. |
198 | bool isFindingAmbiguities() const { return FindAmbiguities; } |
199 | |
200 | /// Whether we are recording paths. |
201 | bool isRecordingPaths() const { return RecordPaths; } |
202 | |
203 | /// Specify whether we should be recording paths or not. |
204 | void setRecordingPaths(bool RP) { RecordPaths = RP; } |
205 | |
206 | /// Whether we are detecting virtual bases. |
207 | bool isDetectingVirtual() const { return DetectVirtual; } |
208 | |
209 | /// 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 | /// Retrieve the type from which this base-paths search |
216 | /// began |
217 | const CXXRecordDecl *getOrigin() const { return Origin; } |
218 | void setOrigin(const CXXRecordDecl *Rec) { Origin = Rec; } |
219 | |
220 | /// Clear the base-paths results. |
221 | void clear(); |
222 | |
223 | /// Swap this data structure's contents with another CXXBasePaths |
224 | /// object. |
225 | void swap(CXXBasePaths &Other); |
226 | }; |
227 | |
228 | /// Uniquely identifies a virtual method within a class |
229 | /// hierarchy by the method itself and a class subobject number. |
230 | struct UniqueVirtualMethod { |
231 | /// The overriding virtual method. |
232 | CXXMethodDecl *Method = nullptr; |
233 | |
234 | /// The subobject in which the overriding virtual method |
235 | /// resides. |
236 | unsigned Subobject = 0; |
237 | |
238 | /// The virtual base class subobject of which this overridden |
239 | /// virtual method is a part. Note that this records the closest |
240 | /// derived virtual base class subobject. |
241 | const CXXRecordDecl *InVirtualSubobject = nullptr; |
242 | |
243 | UniqueVirtualMethod() = default; |
244 | |
245 | UniqueVirtualMethod(CXXMethodDecl *Method, unsigned Subobject, |
246 | const CXXRecordDecl *InVirtualSubobject) |
247 | : Method(Method), Subobject(Subobject), |
248 | InVirtualSubobject(InVirtualSubobject) {} |
249 | |
250 | friend bool operator==(const UniqueVirtualMethod &X, |
251 | const UniqueVirtualMethod &Y) { |
252 | return X.Method == Y.Method && X.Subobject == Y.Subobject && |
253 | X.InVirtualSubobject == Y.InVirtualSubobject; |
254 | } |
255 | |
256 | friend bool operator!=(const UniqueVirtualMethod &X, |
257 | const UniqueVirtualMethod &Y) { |
258 | return !(X == Y); |
259 | } |
260 | }; |
261 | |
262 | /// The set of methods that override a given virtual method in |
263 | /// each subobject where it occurs. |
264 | /// |
265 | /// The first part of the pair is the subobject in which the |
266 | /// overridden virtual function occurs, while the second part of the |
267 | /// pair is the virtual method that overrides it (including the |
268 | /// subobject in which that virtual function occurs). |
269 | class OverridingMethods { |
270 | using ValuesT = SmallVector<UniqueVirtualMethod, 4>; |
271 | using MapType = llvm::MapVector<unsigned, ValuesT>; |
272 | |
273 | MapType Overrides; |
274 | |
275 | public: |
276 | // Iterate over the set of subobjects that have overriding methods. |
277 | using iterator = MapType::iterator; |
278 | using const_iterator = MapType::const_iterator; |
279 | |
280 | iterator begin() { return Overrides.begin(); } |
281 | const_iterator begin() const { return Overrides.begin(); } |
282 | iterator end() { return Overrides.end(); } |
283 | const_iterator end() const { return Overrides.end(); } |
284 | unsigned size() const { return Overrides.size(); } |
285 | |
286 | // Iterate over the set of overriding virtual methods in a given |
287 | // subobject. |
288 | using overriding_iterator = |
289 | SmallVectorImpl<UniqueVirtualMethod>::iterator; |
290 | using overriding_const_iterator = |
291 | SmallVectorImpl<UniqueVirtualMethod>::const_iterator; |
292 | |
293 | // Add a new overriding method for a particular subobject. |
294 | void add(unsigned OverriddenSubobject, UniqueVirtualMethod Overriding); |
295 | |
296 | // Add all of the overriding methods from "other" into overrides for |
297 | // this method. Used when merging the overrides from multiple base |
298 | // class subobjects. |
299 | void add(const OverridingMethods &Other); |
300 | |
301 | // Replace all overriding virtual methods in all subobjects with the |
302 | // given virtual method. |
303 | void replaceAll(UniqueVirtualMethod Overriding); |
304 | }; |
305 | |
306 | /// A mapping from each virtual member function to its set of |
307 | /// final overriders. |
308 | /// |
309 | /// Within a class hierarchy for a given derived class, each virtual |
310 | /// member function in that hierarchy has one or more "final |
311 | /// overriders" (C++ [class.virtual]p2). A final overrider for a |
312 | /// virtual function "f" is the virtual function that will actually be |
313 | /// invoked when dispatching a call to "f" through the |
314 | /// vtable. Well-formed classes have a single final overrider for each |
315 | /// virtual function; in abstract classes, the final overrider for at |
316 | /// least one virtual function is a pure virtual function. Due to |
317 | /// multiple, virtual inheritance, it is possible for a class to have |
318 | /// more than one final overrider. Although this is an error (per C++ |
319 | /// [class.virtual]p2), it is not considered an error here: the final |
320 | /// overrider map can represent multiple final overriders for a |
321 | /// method, and it is up to the client to determine whether they are |
322 | /// problem. For example, the following class \c D has two final |
323 | /// overriders for the virtual function \c A::f(), one in \c C and one |
324 | /// in \c D: |
325 | /// |
326 | /// \code |
327 | /// struct A { virtual void f(); }; |
328 | /// struct B : virtual A { virtual void f(); }; |
329 | /// struct C : virtual A { virtual void f(); }; |
330 | /// struct D : B, C { }; |
331 | /// \endcode |
332 | /// |
333 | /// This data structure contains a mapping from every virtual |
334 | /// function *that does not override an existing virtual function* and |
335 | /// in every subobject where that virtual function occurs to the set |
336 | /// of virtual functions that override it. Thus, the same virtual |
337 | /// function \c A::f can actually occur in multiple subobjects of type |
338 | /// \c A due to multiple inheritance, and may be overridden by |
339 | /// different virtual functions in each, as in the following example: |
340 | /// |
341 | /// \code |
342 | /// struct A { virtual void f(); }; |
343 | /// struct B : A { virtual void f(); }; |
344 | /// struct C : A { virtual void f(); }; |
345 | /// struct D : B, C { }; |
346 | /// \endcode |
347 | /// |
348 | /// Unlike in the previous example, where the virtual functions \c |
349 | /// B::f and \c C::f both overrode \c A::f in the same subobject of |
350 | /// type \c A, in this example the two virtual functions both override |
351 | /// \c A::f but in *different* subobjects of type A. This is |
352 | /// represented by numbering the subobjects in which the overridden |
353 | /// and the overriding virtual member functions are located. Subobject |
354 | /// 0 represents the virtual base class subobject of that type, while |
355 | /// subobject numbers greater than 0 refer to non-virtual base class |
356 | /// subobjects of that type. |
357 | class CXXFinalOverriderMap |
358 | : public llvm::MapVector<const CXXMethodDecl *, OverridingMethods> {}; |
359 | |
360 | /// A set of all the primary bases for a class. |
361 | class CXXIndirectPrimaryBaseSet |
362 | : public llvm::SmallSet<const CXXRecordDecl*, 32> {}; |
363 | |
364 | inline bool |
365 | inheritanceModelHasVBPtrOffsetField(MSInheritanceModel Inheritance) { |
366 | return Inheritance == MSInheritanceModel::Unspecified; |
367 | } |
368 | |
369 | // Only member pointers to functions need a this adjustment, since it can be |
370 | // combined with the field offset for data pointers. |
371 | inline bool inheritanceModelHasNVOffsetField(bool IsMemberFunction, |
372 | MSInheritanceModel Inheritance) { |
373 | return IsMemberFunction && Inheritance >= MSInheritanceModel::Multiple; |
374 | } |
375 | |
376 | inline bool |
377 | inheritanceModelHasVBTableOffsetField(MSInheritanceModel Inheritance) { |
378 | return Inheritance >= MSInheritanceModel::Virtual; |
379 | } |
380 | |
381 | inline bool inheritanceModelHasOnlyOneField(bool IsMemberFunction, |
382 | MSInheritanceModel Inheritance) { |
383 | if (IsMemberFunction) |
384 | return Inheritance <= MSInheritanceModel::Single; |
385 | return Inheritance <= MSInheritanceModel::Multiple; |
386 | } |
387 | |
388 | } // namespace clang |
389 | |
390 | #endif // LLVM_CLANG_AST_CXXINHERITANCE_H |
391 | |