CXXInheritance.h source code [clang_source_code/include/clang/AST/CXXInheritance.h]

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/DenseSet.h"
24	#include "llvm/ADT/MapVector.h"
25	#include "llvm/ADT/SmallSet.h"
26	#include "llvm/ADT/SmallVector.h"
27	#include "llvm/ADT/iterator_range.h"
28	#include <list>
29	#include <memory>
30	#include <utility>
31
32	namespace clang {
33
34	class ASTContext;
35	class NamedDecl;
36
37	/// Represents an element in a path from a derived class to a
38	/// base class.
39	///
40	/// Each step in the path references the link from a
41	/// derived class to one of its direct base classes, along with a
42	/// base "number" that identifies which base subobject of the
43	/// original derived class we are referencing.
44	struct CXXBasePathElement {
45	/// The base specifier that states the link from a derived
46	/// class to a base class, which will be followed by this base
47	/// path element.
48	const CXXBaseSpecifier *Base;
49
50	/// The record decl of the class that the base is a base of.
51	const CXXRecordDecl *Class;
52
53	/// Identifies which base class subobject (of type
54	/// \c Base->getType()) this base path element refers to.
55	///
56	/// This value is only valid if \c !Base->isVirtual(), because there
57	/// is no base numbering for the zero or one virtual bases of a
58	/// given type.
59	int SubobjectNumber;
60	};
61
62	/// Represents a path from a specific derived class
63	/// (which is not represented as part of the path) to a particular
64	/// (direct or indirect) base class subobject.
65	///
66	/// Individual elements in the path are described by the \c CXXBasePathElement
67	/// structure, which captures both the link from a derived class to one of its
68	/// direct bases and identification describing which base class
69	/// subobject is being used.
70	class CXXBasePath : public SmallVector<CXXBasePathElement, 4> {
71	public:
72	/// The access along this inheritance path. This is only
73	/// calculated when recording paths. AS_none is a special value
74	/// used to indicate a path which permits no legal access.
75	AccessSpecifier Access = AS_public;
76
77	CXXBasePath() = default;
78
79	/// The set of declarations found inside this base class
80	/// subobject.
81	DeclContext::lookup_result Decls;
82
83	void clear() {
84	SmallVectorImpl<CXXBasePathElement>::clear();
85	Access = AS_public;
86	}
87	};
88
89	/// BasePaths - Represents the set of paths from a derived class to
90	/// one of its (direct or indirect) bases. For example, given the
91	/// following class hierarchy:
92	///
93	/// @code
94	/// class A { };
95	/// class B : public A { };
96	/// class C : public A { };
97	/// class D : public B, public C{ };
98	/// @endcode
99	///
100	/// There are two potential BasePaths to represent paths from D to a
101	/// base subobject of type A. One path is (D,0) -> (B,0) -> (A,0)
102	/// and another is (D,0)->(C,0)->(A,1). These two paths actually
103	/// refer to two different base class subobjects of the same type,
104	/// so the BasePaths object refers to an ambiguous path. On the
105	/// other hand, consider the following class hierarchy:
106	///
107	/// @code
108	/// class A { };
109	/// class B : public virtual A { };
110	/// class C : public virtual A { };
111	/// class D : public B, public C{ };
112	/// @endcode
113	///
114	/// Here, there are two potential BasePaths again, (D, 0) -> (B, 0)
115	/// -> (A,v) and (D, 0) -> (C, 0) -> (A, v), but since both of them
116	/// refer to the same base class subobject of type A (the virtual
117	/// one), there is no ambiguity.
118	class CXXBasePaths {
119	friend class CXXRecordDecl;
120
121	/// The type from which this search originated.
122	CXXRecordDecl *Origin = nullptr;
123
124	/// Paths - The actual set of paths that can be taken from the
125	/// derived class to the same base class.
126	std::list<CXXBasePath> Paths;
127
128	/// ClassSubobjects - Records the class subobjects for each class
129	/// type that we've seen. The first element IsVirtBase says
130	/// whether we found a path to a virtual base for that class type,
131	/// while NumberOfNonVirtBases contains the number of non-virtual base
132	/// class subobjects for that class type. The key of the map is
133	/// the cv-unqualified canonical type of the base class subobject.
134	struct IsVirtBaseAndNumberNonVirtBases {
135	unsigned IsVirtBase : 1;
136	unsigned NumberOfNonVirtBases : 31;
137	};
138	llvm::SmallDenseMap<QualType, IsVirtBaseAndNumberNonVirtBases, 8>
139	ClassSubobjects;
140
141	/// VisitedDependentRecords - Records the dependent records that have been
142	/// already visited.
143	llvm::SmallPtrSet<const CXXRecordDecl *, 4> VisitedDependentRecords;
144
145	/// DetectedVirtual - The base class that is virtual.
146	const RecordType *DetectedVirtual = nullptr;
147
148	/// ScratchPath - A BasePath that is used by Sema::lookupInBases
149	/// to help build the set of paths.
150	CXXBasePath ScratchPath;
151
152	/// Array of the declarations that have been found. This
153	/// array is constructed only if needed, e.g., to iterate over the
154	/// results within LookupResult.
155	std::unique_ptr<NamedDecl *[]> DeclsFound;
156	unsigned NumDeclsFound = 0;
157
158	/// FindAmbiguities - Whether Sema::IsDerivedFrom should try find
159	/// ambiguous paths while it is looking for a path from a derived
160	/// type to a base type.
161	bool FindAmbiguities;
162
163	/// RecordPaths - Whether Sema::IsDerivedFrom should record paths
164	/// while it is determining whether there are paths from a derived
165	/// type to a base type.
166	bool RecordPaths;
167
168	/// DetectVirtual - Whether Sema::IsDerivedFrom should abort the search
169	/// if it finds a path that goes across a virtual base. The virtual class
170	/// is also recorded.
171	bool DetectVirtual;
172
173	void ComputeDeclsFound();
174
175	bool lookupInBases(ASTContext &Context, const CXXRecordDecl *Record,
176	CXXRecordDecl::BaseMatchesCallback BaseMatches,
177	bool LookupInDependent = false);
178
179	public:
180	using paths_iterator = std::list<CXXBasePath>::iterator;
181	using const_paths_iterator = std::list<CXXBasePath>::const_iterator;
182	using decl_iterator = NamedDecl **;
183
184	/// BasePaths - Construct a new BasePaths structure to record the
185	/// paths for a derived-to-base search.
186	explicit CXXBasePaths(bool FindAmbiguities = true, bool RecordPaths = true,
187	bool DetectVirtual = true)
188	: FindAmbiguities(FindAmbiguities), RecordPaths(RecordPaths),
189	DetectVirtual(DetectVirtual) {}
190
191	paths_iterator begin() { return Paths.begin(); }
192	paths_iterator end() { return Paths.end(); }
193	const_paths_iterator begin() const { return Paths.begin(); }
194	const_paths_iterator end() const { return Paths.end(); }
195
196	CXXBasePath& front() { return Paths.front(); }
197	const CXXBasePath& front() const { return Paths.front(); }
198
199	using decl_range = llvm::iterator_range<decl_iterator>;
200
201	decl_range found_decls();
202
203	/// Determine whether the path from the most-derived type to the
204	/// given base type is ambiguous (i.e., it refers to multiple subobjects of
205	/// the same base type).
206	bool isAmbiguous(CanQualType BaseType);
207
208	/// Whether we are finding multiple paths to detect ambiguities.
209	bool isFindingAmbiguities() const { return FindAmbiguities; }
210
211	/// Whether we are recording paths.
212	bool isRecordingPaths() const { return RecordPaths; }
213
214	/// Specify whether we should be recording paths or not.
215	void setRecordingPaths(bool RP) { RecordPaths = RP; }
216
217	/// Whether we are detecting virtual bases.
218	bool isDetectingVirtual() const { return DetectVirtual; }
219
220	/// The virtual base discovered on the path (if we are merely
221	/// detecting virtuals).
222	const RecordType* getDetectedVirtual() const {
223	return DetectedVirtual;
224	}
225
226	/// Retrieve the type from which this base-paths search
227	/// began
228	CXXRecordDecl *getOrigin() const { return Origin; }
229	void setOrigin(CXXRecordDecl *Rec) { Origin = Rec; }
230
231	/// Clear the base-paths results.
232	void clear();
233
234	/// Swap this data structure's contents with another CXXBasePaths
235	/// object.
236	void swap(CXXBasePaths &Other);
237	};
238
239	/// Uniquely identifies a virtual method within a class
240	/// hierarchy by the method itself and a class subobject number.
241	struct UniqueVirtualMethod {
242	/// The overriding virtual method.
243	CXXMethodDecl *Method = nullptr;
244
245	/// The subobject in which the overriding virtual method
246	/// resides.
247	unsigned Subobject = 0;
248
249	/// The virtual base class subobject of which this overridden
250	/// virtual method is a part. Note that this records the closest
251	/// derived virtual base class subobject.
252	const CXXRecordDecl *InVirtualSubobject = nullptr;
253
254	UniqueVirtualMethod() = default;
255
256	UniqueVirtualMethod(CXXMethodDecl *Method, unsigned Subobject,
257	const CXXRecordDecl *InVirtualSubobject)
258	: Method(Method), Subobject(Subobject),
259	InVirtualSubobject(InVirtualSubobject) {}
260
261	friend bool operator==(const UniqueVirtualMethod &X,
262	const UniqueVirtualMethod &Y) {
263	return X.Method == Y.Method && X.Subobject == Y.Subobject &&
264	X.InVirtualSubobject == Y.InVirtualSubobject;
265	}
266
267	friend bool operator!=(const UniqueVirtualMethod &X,
268	const UniqueVirtualMethod &Y) {
269	return !(X == Y);
270	}
271	};
272
273	/// The set of methods that override a given virtual method in
274	/// each subobject where it occurs.
275	///
276	/// The first part of the pair is the subobject in which the
277	/// overridden virtual function occurs, while the second part of the
278	/// pair is the virtual method that overrides it (including the
279	/// subobject in which that virtual function occurs).
280	class OverridingMethods {
281	using ValuesT = SmallVector<UniqueVirtualMethod, 4>;
282	using MapType = llvm::MapVector<unsigned, ValuesT>;
283
284	MapType Overrides;
285
286	public:
287	// Iterate over the set of subobjects that have overriding methods.
288	using iterator = MapType::iterator;
289	using const_iterator = MapType::const_iterator;
290
291	iterator begin() { return Overrides.begin(); }
292	const_iterator begin() const { return Overrides.begin(); }
293	iterator end() { return Overrides.end(); }
294	const_iterator end() const { return Overrides.end(); }
295	unsigned size() const { return Overrides.size(); }
296
297	// Iterate over the set of overriding virtual methods in a given
298	// subobject.
299	using overriding_iterator =
300	SmallVectorImpl<UniqueVirtualMethod>::iterator;
301	using overriding_const_iterator =
302	SmallVectorImpl<UniqueVirtualMethod>::const_iterator;
303
304	// Add a new overriding method for a particular subobject.
305	void add(unsigned OverriddenSubobject, UniqueVirtualMethod Overriding);
306
307	// Add all of the overriding methods from "other" into overrides for
308	// this method. Used when merging the overrides from multiple base
309	// class subobjects.
310	void add(const OverridingMethods &Other);
311
312	// Replace all overriding virtual methods in all subobjects with the
313	// given virtual method.
314	void replaceAll(UniqueVirtualMethod Overriding);
315	};
316
317	/// A mapping from each virtual member function to its set of
318	/// final overriders.
319	///
320	/// Within a class hierarchy for a given derived class, each virtual
321	/// member function in that hierarchy has one or more "final
322	/// overriders" (C++ [class.virtual]p2). A final overrider for a
323	/// virtual function "f" is the virtual function that will actually be
324	/// invoked when dispatching a call to "f" through the
325	/// vtable. Well-formed classes have a single final overrider for each
326	/// virtual function; in abstract classes, the final overrider for at
327	/// least one virtual function is a pure virtual function. Due to
328	/// multiple, virtual inheritance, it is possible for a class to have
329	/// more than one final overrider. Athough this is an error (per C++
330	/// [class.virtual]p2), it is not considered an error here: the final
331	/// overrider map can represent multiple final overriders for a
332	/// method, and it is up to the client to determine whether they are
333	/// problem. For example, the following class \c D has two final
334	/// overriders for the virtual function \c A::f(), one in \c C and one
335	/// in \c D:
336	///
337	/// \code
338	/// struct A { virtual void f(); };
339	/// struct B : virtual A { virtual void f(); };
340	/// struct C : virtual A { virtual void f(); };
341	/// struct D : B, C { };
342	/// \endcode
343	///
344	/// This data structure contains a mapping from every virtual
345	/// function that does not override an existing virtual function and
346	/// in every subobject where that virtual function occurs to the set
347	/// of virtual functions that override it. Thus, the same virtual
348	/// function \c A::f can actually occur in multiple subobjects of type
349	/// \c A due to multiple inheritance, and may be overridden by
350	/// different virtual functions in each, as in the following example:
351	///
352	/// \code
353	/// struct A { virtual void f(); };
354	/// struct B : A { virtual void f(); };
355	/// struct C : A { virtual void f(); };
356	/// struct D : B, C { };
357	/// \endcode
358	///
359	/// Unlike in the previous example, where the virtual functions \c
360	/// B::f and \c C::f both overrode \c A::f in the same subobject of
361	/// type \c A, in this example the two virtual functions both override
362	/// \c A::f but in different subobjects of type A. This is
363	/// represented by numbering the subobjects in which the overridden
364	/// and the overriding virtual member functions are located. Subobject
365	/// 0 represents the virtual base class subobject of that type, while
366	/// subobject numbers greater than 0 refer to non-virtual base class
367	/// subobjects of that type.
368	class CXXFinalOverriderMap
369	: public llvm::MapVector<const CXXMethodDecl *, OverridingMethods> {};
370
371	/// A set of all the primary bases for a class.
372	class CXXIndirectPrimaryBaseSet
373	: public llvm::SmallSet<const CXXRecordDecl*, 32> {};
374
375	} // namespace clang
376
377	#endif // LLVM_CLANG_AST_CXXINHERITANCE_H
378