1 //===- DeclFriend.h - Classes for C++ friend declarations -------*- 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 defines the section of the AST representing C++ friend
10 // declarations.
11 //
12 //===----------------------------------------------------------------------===//
13 
14 #ifndef LLVM_CLANG_AST_DECLFRIEND_H
15 #define LLVM_CLANG_AST_DECLFRIEND_H
16 
17 #include "clang/AST/Decl.h"
18 #include "clang/AST/DeclBase.h"
19 #include "clang/AST/DeclCXX.h"
20 #include "clang/AST/DeclTemplate.h"
21 #include "clang/AST/ExternalASTSource.h"
22 #include "clang/AST/TypeLoc.h"
23 #include "clang/Basic/LLVM.h"
24 #include "clang/Basic/SourceLocation.h"
25 #include "llvm/ADT/ArrayRef.h"
26 #include "llvm/ADT/None.h"
27 #include "llvm/ADT/PointerUnion.h"
28 #include "llvm/Support/Casting.h"
29 #include "llvm/Support/Compiler.h"
30 #include "llvm/Support/TrailingObjects.h"
31 #include <cassert>
32 #include <iterator>
33 
34 namespace clang {
35 
36 class ASTContext;
37 
38 /// FriendDecl - Represents the declaration of a friend entity,
39 /// which can be a function, a type, or a templated function or type.
40 /// For example:
41 ///
42 /// @code
43 /// template <typename T> class A {
44 ///   friend int foo(T);
45 ///   friend class B;
46 ///   friend T; // only in C++0x
47 ///   template <typename U> friend class C;
48 ///   template <typename U> friend A& operator+=(A&, const U&) { ... }
49 /// };
50 /// @endcode
51 ///
52 /// The semantic context of a friend decl is its declaring class.
53 class FriendDecl final
54     : public Decl,
55       private llvm::TrailingObjects<FriendDecl, TemplateParameterList *> {
56   virtual void anchor();
57 
58 public:
59   using FriendUnion = llvm::PointerUnion<NamedDecl *, TypeSourceInfo *>;
60 
61 private:
62   friend class CXXRecordDecl;
63   friend class CXXRecordDecl::friend_iterator;
64 
65   // The declaration that's a friend of this class.
66   FriendUnion Friend;
67 
68   // A pointer to the next friend in the sequence.
69   LazyDeclPtr NextFriend;
70 
71   // Location of the 'friend' specifier.
72   SourceLocation FriendLoc;
73 
74   /// True if this 'friend' declaration is unsupported.  Eventually we
75   /// will support every possible friend declaration, but for now we
76   /// silently ignore some and set this flag to authorize all access.
77   unsigned UnsupportedFriend : 1;
78 
79   // The number of "outer" template parameter lists in non-templatic
80   // (currently unsupported) friend type declarations, such as
81   //     template <class T> friend class A<T>::B;
82   unsigned NumTPLists : 31;
83 
84   FriendDecl(DeclContext *DC, SourceLocation L, FriendUnion Friend,
85              SourceLocation FriendL,
86              ArrayRef<TemplateParameterList *> FriendTypeTPLists)
87       : Decl(Decl::Friend, DC, L), Friend(Friend), FriendLoc(FriendL),
88         UnsupportedFriend(false), NumTPLists(FriendTypeTPLists.size()) {
89     for (unsigned i = 0; i < NumTPLists; ++i)
90       getTrailingObjects<TemplateParameterList *>()[i] = FriendTypeTPLists[i];
91   }
92 
93   FriendDecl(EmptyShell Empty, unsigned NumFriendTypeTPLists)
94       : Decl(Decl::Friend, Empty), UnsupportedFriend(false),
95         NumTPLists(NumFriendTypeTPLists) {}
96 
97   FriendDecl *getNextFriend() {
98     if (!NextFriend.isOffset())
99       return cast_or_null<FriendDecl>(NextFriend.get(nullptr));
100     return getNextFriendSlowCase();
101   }
102 
103   FriendDecl *getNextFriendSlowCase();
104 
105 public:
106   friend class ASTDeclReader;
107   friend class ASTDeclWriter;
108   friend class ASTNodeImporter;
109   friend TrailingObjects;
110 
111   static FriendDecl *Create(ASTContext &C, DeclContext *DC,
112                             SourceLocation L, FriendUnion Friend_,
113                             SourceLocation FriendL,
114                             ArrayRef<TemplateParameterList*> FriendTypeTPLists
115                             = None);
116   static FriendDecl *CreateDeserialized(ASTContext &C, unsigned ID,
117                                         unsigned FriendTypeNumTPLists);
118 
119   /// If this friend declaration names an (untemplated but possibly
120   /// dependent) type, return the type; otherwise return null.  This
121   /// is used for elaborated-type-specifiers and, in C++0x, for
122   /// arbitrary friend type declarations.
123   TypeSourceInfo *getFriendType() const {
124     return Friend.dyn_cast<TypeSourceInfo*>();
125   }
126 
127   unsigned getFriendTypeNumTemplateParameterLists() const {
128     return NumTPLists;
129   }
130 
131   TemplateParameterList *getFriendTypeTemplateParameterList(unsigned N) const {
132     assert(N < NumTPLists);
133     return getTrailingObjects<TemplateParameterList *>()[N];
134   }
135 
136   /// If this friend declaration doesn't name a type, return the inner
137   /// declaration.
138   NamedDecl *getFriendDecl() const {
139     return Friend.dyn_cast<NamedDecl *>();
140   }
141 
142   /// Retrieves the location of the 'friend' keyword.
143   SourceLocation getFriendLoc() const {
144     return FriendLoc;
145   }
146 
147   /// Retrieves the source range for the friend declaration.
148   SourceRange getSourceRange() const override LLVM_READONLY {
149     if (NamedDecl *ND = getFriendDecl()) {
150       if (const auto *FD = dyn_cast<FunctionDecl>(ND))
151         return FD->getSourceRange();
152       if (const auto *FTD = dyn_cast<FunctionTemplateDecl>(ND))
153         return FTD->getSourceRange();
154       if (const auto *CTD = dyn_cast<ClassTemplateDecl>(ND))
155         return CTD->getSourceRange();
156       if (const auto *DD = dyn_cast<DeclaratorDecl>(ND)) {
157         if (DD->getOuterLocStart() != DD->getInnerLocStart())
158           return DD->getSourceRange();
159       }
160       return SourceRange(getFriendLoc(), ND->getEndLoc());
161     }
162     else if (TypeSourceInfo *TInfo = getFriendType()) {
163       SourceLocation StartL =
164           (NumTPLists == 0) ? getFriendLoc()
165                             : getTrailingObjects<TemplateParameterList *>()[0]
166                                   ->getTemplateLoc();
167       return SourceRange(StartL, TInfo->getTypeLoc().getEndLoc());
168     }
169     else
170       return SourceRange(getFriendLoc(), getLocation());
171   }
172 
173   /// Determines if this friend kind is unsupported.
174   bool isUnsupportedFriend() const {
175     return UnsupportedFriend;
176   }
177   void setUnsupportedFriend(bool Unsupported) {
178     UnsupportedFriend = Unsupported;
179   }
180 
181   // Implement isa/cast/dyncast/etc.
182   static bool classof(const Decl *D) { return classofKind(D->getKind()); }
183   static bool classofKind(Kind K) { return K == Decl::Friend; }
184 };
185 
186 /// An iterator over the friend declarations of a class.
187 class CXXRecordDecl::friend_iterator {
188   friend class CXXRecordDecl;
189 
190   FriendDecl *Ptr;
191 
192   explicit friend_iterator(FriendDecl *Ptr) : Ptr(Ptr) {}
193 
194 public:
195   friend_iterator() = default;
196 
197   using value_type = FriendDecl *;
198   using reference = FriendDecl *;
199   using pointer = FriendDecl *;
200   using difference_type = int;
201   using iterator_category = std::forward_iterator_tag;
202 
203   reference operator*() const { return Ptr; }
204 
205   friend_iterator &operator++() {
206     assert(Ptr && "attempt to increment past end of friend list");
207     Ptr = Ptr->getNextFriend();
208     return *this;
209   }
210 
211   friend_iterator operator++(int) {
212     friend_iterator tmp = *this;
213     ++*this;
214     return tmp;
215   }
216 
217   bool operator==(const friend_iterator &Other) const {
218     return Ptr == Other.Ptr;
219   }
220 
221   bool operator!=(const friend_iterator &Other) const {
222     return Ptr != Other.Ptr;
223   }
224 
225   friend_iterator &operator+=(difference_type N) {
226     assert(N >= 0 && "cannot rewind a CXXRecordDecl::friend_iterator");
227     while (N--)
228       ++*this;
229     return *this;
230   }
231 
232   friend_iterator operator+(difference_type N) const {
233     friend_iterator tmp = *this;
234     tmp += N;
235     return tmp;
236   }
237 };
238 
239 inline CXXRecordDecl::friend_iterator CXXRecordDecl::friend_begin() const {
240   return friend_iterator(getFirstFriend());
241 }
242 
243 inline CXXRecordDecl::friend_iterator CXXRecordDecl::friend_end() const {
244   return friend_iterator(nullptr);
245 }
246 
247 inline CXXRecordDecl::friend_range CXXRecordDecl::friends() const {
248   return friend_range(friend_begin(), friend_end());
249 }
250 
251 inline void CXXRecordDecl::pushFriendDecl(FriendDecl *FD) {
252   assert(!FD->NextFriend && "friend already has next friend?");
253   FD->NextFriend = data().FirstFriend;
254   data().FirstFriend = FD;
255 }
256 
257 } // namespace clang
258 
259 #endif // LLVM_CLANG_AST_DECLFRIEND_H
260