1//===-- Redeclarable.h - Base for Decls that can be redeclared -*- 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 defines the Redeclarable interface.
11//
12//===----------------------------------------------------------------------===//
13
14#ifndef LLVM_CLANG_AST_REDECLARABLE_H
15#define LLVM_CLANG_AST_REDECLARABLE_H
16
17#include "clang/AST/ExternalASTSource.h"
18#include "llvm/ADT/PointerIntPair.h"
19#include "llvm/Support/Casting.h"
20#include <iterator>
21
22namespace clang {
23
24/// \brief Provides common interface for the Decls that can be redeclared.
25template<typename decl_type>
26class Redeclarable {
27protected:
28  class DeclLink {
29    /// A pointer to a known latest declaration, either statically known or
30    /// generationally updated as decls are added by an external source.
31    typedef LazyGenerationalUpdatePtr<const Decl*, Decl*,
32                                      &ExternalASTSource::CompleteRedeclChain>
33                                          KnownLatest;
34
35    typedef const ASTContext *UninitializedLatest;
36    typedef Decl *Previous;
37
38    /// A pointer to either an uninitialized latest declaration (where either
39    /// we've not yet set the previous decl or there isn't one), or to a known
40    /// previous declaration.
41    typedef llvm::PointerUnion<Previous, UninitializedLatest> NotKnownLatest;
42
43    mutable llvm::PointerUnion<NotKnownLatest, KnownLatest> Next;
44
45  public:
46    enum PreviousTag { PreviousLink };
47    enum LatestTag { LatestLink };
48
49    DeclLink(LatestTag, const ASTContext &Ctx)
50        : Next(NotKnownLatest(&Ctx)) {}
51    DeclLink(PreviousTag, decl_type *D)
52        : Next(NotKnownLatest(Previous(D))) {}
53
54    bool NextIsPrevious() const {
55      return Next.is<NotKnownLatest>() &&
56             // FIXME: 'template' is required on the next line due to an
57             // apparent clang bug.
58             Next.get<NotKnownLatest>().template is<Previous>();
59    }
60
61    bool NextIsLatest() const { return !NextIsPrevious(); }
62
63    decl_type *getNext(const decl_type *D) const {
64      if (Next.is<NotKnownLatest>()) {
65        NotKnownLatest NKL = Next.get<NotKnownLatest>();
66        if (NKL.is<Previous>())
67          return static_cast<decl_type*>(NKL.get<Previous>());
68
69        // Allocate the generational 'most recent' cache now, if needed.
70        Next = KnownLatest(*NKL.get<UninitializedLatest>(),
71                           const_cast<decl_type *>(D));
72      }
73
74      return static_cast<decl_type*>(Next.get<KnownLatest>().get(D));
75    }
76
77    void setPrevious(decl_type *D) {
78      assert(NextIsPrevious() && "decl became non-canonical unexpectedly");
79      Next = Previous(D);
80    }
81
82    void setLatest(decl_type *D) {
83      assert(NextIsLatest() && "decl became canonical unexpectedly");
84      if (Next.is<NotKnownLatest>()) {
85        NotKnownLatest NKL = Next.get<NotKnownLatest>();
86        Next = KnownLatest(*NKL.get<UninitializedLatest>(), D);
87      } else {
88        auto Latest = Next.get<KnownLatest>();
89        Latest.set(D);
90        Next = Latest;
91      }
92    }
93
94    void markIncomplete() { Next.get<KnownLatest>().markIncomplete(); }
95
96    Decl *getLatestNotUpdated() const {
97      assert(NextIsLatest() && "expected a canonical decl");
98      if (Next.is<NotKnownLatest>())
99        return nullptr;
100      return Next.get<KnownLatest>().getNotUpdated();
101    }
102  };
103
104  static DeclLink PreviousDeclLink(decl_type *D) {
105    return DeclLink(DeclLink::PreviousLink, D);
106  }
107
108  static DeclLink LatestDeclLink(const ASTContext &Ctx) {
109    return DeclLink(DeclLink::LatestLink, Ctx);
110  }
111
112  /// \brief Points to the next redeclaration in the chain.
113  ///
114  /// If NextIsPrevious() is true, this is a link to the previous declaration
115  /// of this same Decl. If NextIsLatest() is true, this is the first
116  /// declaration and Link points to the latest declaration. For example:
117  ///
118  ///  #1 int f(int x, int y = 1); // <pointer to #3, true>
119  ///  #2 int f(int x = 0, int y); // <pointer to #1, false>
120  ///  #3 int f(int x, int y) { return x + y; } // <pointer to #2, false>
121  ///
122  /// If there is only one declaration, it is <pointer to self, true>
123  DeclLink RedeclLink;
124  decl_type *First;
125
126  decl_type *getNextRedeclaration() const {
127    return RedeclLink.getNext(static_cast<const decl_type *>(this));
128  }
129
130public:
131 Redeclarable(const ASTContext &Ctx)
132     : RedeclLink(LatestDeclLink(Ctx)), First(static_cast<decl_type *>(this)) {}
133
134  /// \brief Return the previous declaration of this declaration or NULL if this
135  /// is the first declaration.
136  decl_type *getPreviousDecl() {
137    if (RedeclLink.NextIsPrevious())
138      return getNextRedeclaration();
139    return nullptr;
140  }
141  const decl_type *getPreviousDecl() const {
142    return const_cast<decl_type *>(
143                 static_cast<const decl_type*>(this))->getPreviousDecl();
144  }
145
146  /// \brief Return the first declaration of this declaration or itself if this
147  /// is the only declaration.
148  decl_type *getFirstDecl() { return First; }
149
150  /// \brief Return the first declaration of this declaration or itself if this
151  /// is the only declaration.
152  const decl_type *getFirstDecl() const { return First; }
153
154  /// \brief True if this is the first declaration in its redeclaration chain.
155  bool isFirstDecl() const { return RedeclLink.NextIsLatest(); }
156
157  /// \brief Returns the most recent (re)declaration of this declaration.
158  decl_type *getMostRecentDecl() {
159    return getFirstDecl()->getNextRedeclaration();
160  }
161
162  /// \brief Returns the most recent (re)declaration of this declaration.
163  const decl_type *getMostRecentDecl() const {
164    return getFirstDecl()->getNextRedeclaration();
165  }
166
167  /// \brief Set the previous declaration. If PrevDecl is NULL, set this as the
168  /// first and only declaration.
169  void setPreviousDecl(decl_type *PrevDecl);
170
171  /// \brief Iterates through all the redeclarations of the same decl.
172  class redecl_iterator {
173    /// Current - The current declaration.
174    decl_type *Current;
175    decl_type *Starter;
176    bool PassedFirst;
177
178  public:
179    typedef decl_type*                value_type;
180    typedef decl_type*                reference;
181    typedef decl_type*                pointer;
182    typedef std::forward_iterator_tag iterator_category;
183    typedef std::ptrdiff_t            difference_type;
184
185    redecl_iterator() : Current(nullptr) { }
186    explicit redecl_iterator(decl_type *C)
187      : Current(C), Starter(C), PassedFirst(false) { }
188
189    reference operator*() const { return Current; }
190    pointer operator->() const { return Current; }
191
192    redecl_iterator& operator++() {
193      assert(Current && "Advancing while iterator has reached end");
194      // Sanity check to avoid infinite loop on invalid redecl chain.
195      if (Current->isFirstDecl()) {
196        if (PassedFirst) {
197          assert(0 && "Passed first decl twice, invalid redecl chain!");
198          Current = nullptr;
199          return *this;
200        }
201        PassedFirst = true;
202      }
203
204      // Get either previous decl or latest decl.
205      decl_type *Next = Current->getNextRedeclaration();
206      Current = (Next != Starter) ? Next : nullptr;
207      return *this;
208    }
209
210    redecl_iterator operator++(int) {
211      redecl_iterator tmp(*this);
212      ++(*this);
213      return tmp;
214    }
215
216    friend bool operator==(redecl_iterator x, redecl_iterator y) {
217      return x.Current == y.Current;
218    }
219    friend bool operator!=(redecl_iterator x, redecl_iterator y) {
220      return x.Current != y.Current;
221    }
222  };
223
224  typedef llvm::iterator_range<redecl_iterator> redecl_range;
225
226  /// \brief Returns an iterator range for all the redeclarations of the same
227  /// decl. It will iterate at least once (when this decl is the only one).
228  redecl_range redecls() const {
229    return redecl_range(redecl_iterator(const_cast<decl_type *>(
230                            static_cast<const decl_type *>(this))),
231                        redecl_iterator());
232  }
233
234  redecl_iterator redecls_begin() const { return redecls().begin(); }
235  redecl_iterator redecls_end() const { return redecls().end(); }
236
237  friend class ASTDeclReader;
238  friend class ASTDeclWriter;
239};
240
241/// \brief Get the primary declaration for a declaration from an AST file. That
242/// will be the first-loaded declaration.
243Decl *getPrimaryMergedDecl(Decl *D);
244
245/// \brief Provides common interface for the Decls that cannot be redeclared,
246/// but can be merged if the same declaration is brought in from multiple
247/// modules.
248template<typename decl_type>
249class Mergeable {
250public:
251  Mergeable() {}
252
253  /// \brief Return the first declaration of this declaration or itself if this
254  /// is the only declaration.
255  decl_type *getFirstDecl() {
256    decl_type *D = static_cast<decl_type*>(this);
257    if (!D->isFromASTFile())
258      return D;
259    return cast<decl_type>(getPrimaryMergedDecl(const_cast<decl_type*>(D)));
260  }
261
262  /// \brief Return the first declaration of this declaration or itself if this
263  /// is the only declaration.
264  const decl_type *getFirstDecl() const {
265    const decl_type *D = static_cast<const decl_type*>(this);
266    if (!D->isFromASTFile())
267      return D;
268    return cast<decl_type>(getPrimaryMergedDecl(const_cast<decl_type*>(D)));
269  }
270
271  /// \brief Returns true if this is the first declaration.
272  bool isFirstDecl() const { return getFirstDecl() == this; }
273};
274
275}
276
277#endif
278