clang  14.0.0git
ASTImporterLookupTable.h
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1 //===- ASTImporterLookupTable.h - ASTImporter specific lookup--*- 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 ASTImporterLookupTable class which implements a
10 // lookup procedure for the import mechanism.
11 //
12 //===----------------------------------------------------------------------===//
13 
14 #ifndef LLVM_CLANG_AST_ASTIMPORTERLOOKUPTABLE_H
15 #define LLVM_CLANG_AST_ASTIMPORTERLOOKUPTABLE_H
16 
17 #include "clang/AST/DeclBase.h" // lookup_result
19 #include "llvm/ADT/DenseMap.h"
20 #include "llvm/ADT/SetVector.h"
21 
22 namespace clang {
23 
24 class ASTContext;
25 class NamedDecl;
26 class DeclContext;
27 
28 // There are certain cases when normal C/C++ lookup (localUncachedLookup)
29 // does not find AST nodes. E.g.:
30 // Example 1:
31 // template <class T>
32 // struct X {
33 // friend void foo(); // this is never found in the DC of the TU.
34 // };
35 // Example 2:
36 // // The fwd decl to Foo is not found in the lookupPtr of the DC of the
37 // // translation unit decl.
38 // // Here we could find the node by doing a traverse throught the list of
39 // // the Decls in the DC, but that would not scale.
40 // struct A { struct Foo *p; };
41 // This is a severe problem because the importer decides if it has to create a
42 // new Decl or not based on the lookup results.
43 // To overcome these cases we need an importer specific lookup table which
44 // holds every node and we are not interested in any C/C++ specific visibility
45 // considerations. Simply, we must know if there is an existing Decl in a
46 // given DC. Once we found it then we can handle any visibility related tasks.
48 
49  // We store a list of declarations for each name.
50  // And we collect these lists for each DeclContext.
51  // We could have a flat map with (DeclContext, Name) tuple as key, but a two
52  // level map seems easier to handle.
54  using NameMap = llvm::SmallDenseMap<DeclarationName, DeclList, 4>;
55  using DCMap = llvm::DenseMap<DeclContext *, NameMap>;
56 
57  void add(DeclContext *DC, NamedDecl *ND);
58  void remove(DeclContext *DC, NamedDecl *ND);
59 
60  DCMap LookupTable;
61 
62 public:
64  void add(NamedDecl *ND);
65  void remove(NamedDecl *ND);
66  // Sometimes a declaration is created first with a temporarily value of decl
67  // context (often the translation unit) and later moved to the final context.
68  // This happens for declarations that are created before the final declaration
69  // context. In such cases the lookup table needs to be updated.
70  // (The declaration is in these cases not added to the temporary decl context,
71  // only its parent is set.)
72  // FIXME: It would be better to not add the declaration to the temporary
73  // context at all in the lookup table, but this requires big change in
74  // ASTImporter.
75  // The function should be called when the old context is definitely different
76  // from the new.
77  void update(NamedDecl *ND, DeclContext *OldDC);
80  // Check if the `ND` is within the lookup table (with its current name) in
81  // context `DC`. This is intended for debug purposes when the DeclContext of a
82  // NamedDecl is changed.
83  bool contains(DeclContext *DC, NamedDecl *ND) const;
84  void dump(DeclContext *DC) const;
85  void dump() const;
86 };
87 
88 } // namespace clang
89 
90 #endif // LLVM_CLANG_AST_ASTIMPORTERLOOKUPTABLE_H
clang::DeclContext
DeclContext - This is used only as base class of specific decl types that can act as declaration cont...
Definition: DeclBase.h:1347
clang::NamedDecl
This represents a decl that may have a name.
Definition: Decl.h:249
clang::ASTImporterLookupTable::lookup
LookupResult lookup(DeclContext *DC, DeclarationName Name) const
Definition: ASTImporterLookupTable.cpp:134
clang::DeclarationName
The name of a declaration.
Definition: DeclarationName.h:145
clang::TranslationUnitDecl
The top declaration context.
Definition: Decl.h:82
DeclBase.h
clang::ASTImporterLookupTable::contains
bool contains(DeclContext *DC, NamedDecl *ND) const
Definition: ASTImporterLookupTable.cpp:147
clang::ASTImporterLookupTable::update
void update(NamedDecl *ND, DeclContext *OldDC)
Definition: ASTImporterLookupTable.cpp:120
clang::ASTImporterLookupTable::ASTImporterLookupTable
ASTImporterLookupTable(TranslationUnitDecl &TU)
Definition: ASTImporterLookupTable.cpp:84
clang::ASTImporterLookupTable
Definition: ASTImporterLookupTable.h:47
clang::ASTImporterLookupTable::dump
void dump() const
Definition: ASTImporterLookupTable.cpp:167
DeclarationName.h
clang
Definition: CalledOnceCheck.h:17
llvm::SmallSetVector
Definition: ExternalSemaSource.h:23