1//===--- ExternalASTMerger.h - Merging External AST Interface ---*- 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 declares the ExternalASTMerger, which vends a combination of ASTs
10//  from several different ASTContext/FileManager pairs
11//
12//===----------------------------------------------------------------------===//
13#ifndef LLVM_CLANG_AST_EXTERNALASTMERGER_H
14#define LLVM_CLANG_AST_EXTERNALASTMERGER_H
15
16#include "clang/AST/ASTImporter.h"
17#include "clang/AST/ASTImporterSharedState.h"
18#include "clang/AST/ExternalASTSource.h"
19#include "llvm/Support/raw_ostream.h"
20
21namespace clang {
22
23/// ExternalASTSource implementation that merges information from several
24/// ASTContexts.
25///
26/// ExternalASTMerger maintains a vector of ASTImporters that it uses to import
27/// (potentially incomplete) Decls and DeclContexts from the source ASTContexts
28/// in response to ExternalASTSource API calls.
29///
30/// When lookup occurs in the resulting imported DeclContexts, the original
31/// DeclContexts need to be queried.  Roughly, there are three cases here:
32///
33/// - The DeclContext of origin can be found by simple name lookup.  In this
34///   case, no additional state is required.
35///
36/// - The DeclContext of origin is different from what would be found by name
37///   lookup.  In this case, Origins contains an entry overriding lookup and
38///   specifying the correct pair of DeclContext/ASTContext.
39///
40/// - The DeclContext of origin was determined by another ExternalASTMerger.
41///   (This is possible when the source ASTContext for one of the Importers has
42///   its own ExternalASTMerger).  The origin must be properly forwarded in this
43///   case.
44///
45/// ExternalASTMerger's job is to maintain the data structures necessary to
46/// allow this.  The data structures themselves can be extracted (read-only) and
47/// copied for re-use.
48class ExternalASTMerger : public ExternalASTSource {
49public:
50  /// A single origin for a DeclContext.  Unlike Decls, DeclContexts do
51  /// not allow their containing ASTContext to be determined in all cases.
52  struct DCOrigin {
53    DeclContext *DC;
54    ASTContext *AST;
55  };
56
57  typedef std::map<const DeclContext *, DCOrigin> OriginMap;
58  typedef std::vector<std::unique_ptr<ASTImporter>> ImporterVector;
59private:
60  /// One importer exists for each source.
61  ImporterVector Importers;
62  /// Overrides in case name lookup would return nothing or would return
63  /// the wrong thing.
64  OriginMap Origins;
65  /// The installed log stream.
66  llvm::raw_ostream *LogStream;
67
68public:
69  /// The target for an ExternalASTMerger.
70  ///
71  /// ASTImporters require both ASTContext and FileManager to be able to
72  /// import SourceLocations properly.
73  struct ImporterTarget {
74    ASTContext &AST;
75    FileManager &FM;
76  };
77  /// A source for an ExternalASTMerger.
78  ///
79  /// ASTImporters require both ASTContext and FileManager to be able to
80  /// import SourceLocations properly.  Additionally, when import occurs for
81  /// a DeclContext whose origin has been overridden, then this
82  /// ExternalASTMerger must be able to determine that.
83  class ImporterSource {
84    ASTContext &AST;
85    FileManager &FM;
86    const OriginMap &OM;
87    /// True iff the source only exists temporary, i.e., it will be removed from
88    /// the ExternalASTMerger during the life time of the ExternalASTMerger.
89    bool Temporary;
90    /// If the ASTContext of this source has an ExternalASTMerger that imports
91    /// into this source, then this will point to that other ExternalASTMerger.
92    ExternalASTMerger *Merger;
93
94  public:
95    ImporterSource(ASTContext &AST, FileManager &FM, const OriginMap &OM,
96                   bool Temporary = false, ExternalASTMerger *Merger = nullptr)
97        : AST(AST), FM(FM), OM(OM), Temporary(Temporary), Merger(Merger) {}
98    ASTContext &getASTContext() const { return AST; }
99    FileManager &getFileManager() const { return FM; }
100    const OriginMap &getOriginMap() const { return OM; }
101    bool isTemporary() const { return Temporary; }
102    ExternalASTMerger *getMerger() const { return Merger; }
103  };
104
105private:
106  /// The target for this ExternalASTMerger.
107  ImporterTarget Target;
108  /// ExternalASTMerger has multiple ASTImporters that import into the same
109  /// TU. This is the shared state for all ASTImporters of this
110  /// ExternalASTMerger.
111  /// See also the CrossTranslationUnitContext that has a similar setup.
112  std::shared_ptr<ASTImporterSharedState> SharedState;
113
114public:
115  ExternalASTMerger(const ImporterTarget &Target,
116                    llvm::ArrayRef<ImporterSource> Sources);
117
118  /// Asks all connected ASTImporters if any of them imported the given
119  /// declaration. If any ASTImporter did import the given declaration,
120  /// then this function returns the declaration that D was imported from.
121  /// Returns nullptr if no ASTImporter did import D.
122  Decl *FindOriginalDecl(Decl *D);
123
124  /// Add a set of ASTContexts as possible origins.
125  ///
126  /// Usually the set will be initialized in the constructor, but long-lived
127  /// ExternalASTMergers may need to import from new sources (for example,
128  /// newly-parsed source files).
129  ///
130  /// Ensures that Importers does not gain duplicate entries as a result.
131  void AddSources(llvm::ArrayRef<ImporterSource> Sources);
132
133  /// Remove a set of ASTContexts as possible origins.
134  ///
135  /// Sometimes an origin goes away (for example, if a source file gets
136  /// superseded by a newer version).
137  ///
138  /// The caller is responsible for ensuring that this doesn't leave
139  /// DeclContexts that can't be completed.
140  void RemoveSources(llvm::ArrayRef<ImporterSource> Sources);
141
142  /// Implementation of the ExternalASTSource API.
143  bool FindExternalVisibleDeclsByName(const DeclContext *DC,
144                                      DeclarationName Name) override;
145
146  /// Implementation of the ExternalASTSource API.
147  void
148  FindExternalLexicalDecls(const DeclContext *DC,
149                           llvm::function_ref<bool(Decl::Kind)> IsKindWeWant,
150                           SmallVectorImpl<Decl *> &Result) override;
151
152  /// Implementation of the ExternalASTSource API.
153  void CompleteType(TagDecl *Tag) override;
154
155  /// Implementation of the ExternalASTSource API.
156  void CompleteType(ObjCInterfaceDecl *Interface) override;
157
158  /// Returns true if DC can be found in any source AST context.
159  bool CanComplete(DeclContext *DC);
160
161  /// Records an origin in Origins only if name lookup would find
162  /// something different or nothing at all.
163  void MaybeRecordOrigin(const DeclContext *ToDC, DCOrigin Origin);
164
165  /// Regardless of any checks, override the Origin for a DeclContext.
166  void ForceRecordOrigin(const DeclContext *ToDC, DCOrigin Origin);
167
168  /// Get a read-only view of the Origins map, for use in constructing
169  /// an ImporterSource for another ExternalASTMerger.
170  const OriginMap &GetOrigins() { return Origins; }
171
172  /// Returns true if Importers contains an ASTImporter whose source is
173  /// OriginContext.
174  bool HasImporterForOrigin(ASTContext &OriginContext);
175
176  /// Returns a reference to the ASTImporter from Importers whose origin
177  /// is OriginContext.  This allows manual import of ASTs while preserving the
178  /// OriginMap correctly.
179  ASTImporter &ImporterForOrigin(ASTContext &OriginContext);
180
181  /// Sets the current log stream.
182  void SetLogStream(llvm::raw_string_ostream &Stream) { LogStream = &Stream; }
183private:
184  /// Records and origin in Origins.
185  void RecordOriginImpl(const DeclContext *ToDC, DCOrigin Origin,
186                                  ASTImporter &importer);
187
188  /// Performs an action for every DeclContext that is identified as
189  /// corresponding (either by forced origin or by name lookup) to DC.
190  template <typename CallbackType>
191  void ForEachMatchingDC(const DeclContext *DC, CallbackType Callback);
192
193public:
194  /// Log something if there is a logging callback installed.
195  llvm::raw_ostream &logs() { return *LogStream; }
196
197  /// True if the log stream is not llvm::nulls();
198  bool LoggingEnabled() { return LogStream != &llvm::nulls(); }
199};
200
201} // end namespace clang
202
203#endif
204