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 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(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(ArrayRef<ImporterSource> Sources);
141
142 /// Implementation of the ExternalASTSource API.
143 bool FindExternalVisibleDeclsByName(const DeclContext *DC,
144 DeclarationName Name,
145 const DeclContext *OriginalDC) override;
146
147 /// Implementation of the ExternalASTSource API.
148 void
149 FindExternalLexicalDecls(const DeclContext *DC,
150 llvm::function_ref<bool(Decl::Kind)> IsKindWeWant,
151 SmallVectorImpl<Decl *> &Result) override;
152
153 /// Implementation of the ExternalASTSource API.
154 void CompleteType(TagDecl *Tag) override;
155
156 /// Implementation of the ExternalASTSource API.
157 void CompleteType(ObjCInterfaceDecl *Interface) override;
158
159 /// Returns true if DC can be found in any source AST context.
160 bool CanComplete(DeclContext *DC);
161
162 /// Records an origin in Origins only if name lookup would find
163 /// something different or nothing at all.
164 void MaybeRecordOrigin(const DeclContext *ToDC, DCOrigin Origin);
165
166 /// Regardless of any checks, override the Origin for a DeclContext.
167 void ForceRecordOrigin(const DeclContext *ToDC, DCOrigin Origin);
168
169 /// Get a read-only view of the Origins map, for use in constructing
170 /// an ImporterSource for another ExternalASTMerger.
171 const OriginMap &GetOrigins() { return Origins; }
172
173 /// Returns true if Importers contains an ASTImporter whose source is
174 /// OriginContext.
175 bool HasImporterForOrigin(ASTContext &OriginContext);
176
177 /// Returns a reference to the ASTImporter from Importers whose origin
178 /// is OriginContext. This allows manual import of ASTs while preserving the
179 /// OriginMap correctly.
180 ASTImporter &ImporterForOrigin(ASTContext &OriginContext);
181
182 /// Sets the current log stream.
183 void SetLogStream(llvm::raw_string_ostream &Stream) { LogStream = &Stream; }
184private:
185 /// Records and origin in Origins.
186 void RecordOriginImpl(const DeclContext *ToDC, DCOrigin Origin,
187 ASTImporter &importer);
188
189 /// Performs an action for every DeclContext that is identified as
190 /// corresponding (either by forced origin or by name lookup) to DC.
191 template <typename CallbackType>
192 void ForEachMatchingDC(const DeclContext *DC, CallbackType Callback);
193
194public:
195 /// Log something if there is a logging callback installed.
196 llvm::raw_ostream &logs() { return *LogStream; }
197
198 /// True if the log stream is not llvm::nulls();
199 bool LoggingEnabled() { return LogStream != &llvm::nulls(); }
200};
201
202} // end namespace clang
203
204#endif
205