clang  3.7.0
Linkage.h
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1 //===--- Linkage.h - Linkage enumeration and utilities ----------*- 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 /// \file
11 /// \brief Defines the Linkage enumeration and various utility functions.
12 ///
13 //===----------------------------------------------------------------------===//
14 #ifndef LLVM_CLANG_BASIC_LINKAGE_H
15 #define LLVM_CLANG_BASIC_LINKAGE_H
16 
17 #include <assert.h>
18 #include <stdint.h>
19 #include <utility>
20 
21 namespace clang {
22 
23 /// \brief Describes the different kinds of linkage
24 /// (C++ [basic.link], C99 6.2.2) that an entity may have.
25 enum Linkage : unsigned char {
26  /// \brief No linkage, which means that the entity is unique and
27  /// can only be referred to from within its scope.
28  NoLinkage = 0,
29 
30  /// \brief Internal linkage, which indicates that the entity can
31  /// be referred to from within the translation unit (but not other
32  /// translation units).
34 
35  /// \brief External linkage within a unique namespace.
36  ///
37  /// From the language perspective, these entities have external
38  /// linkage. However, since they reside in an anonymous namespace,
39  /// their names are unique to this translation unit, which is
40  /// equivalent to having internal linkage from the code-generation
41  /// point of view.
43 
44  /// \brief No linkage according to the standard, but is visible from other
45  /// translation units because of types defined in a inline function.
47 
48  /// \brief External linkage, which indicates that the entity can
49  /// be referred to from other translation units.
51 };
52 
53 /// \brief Describes the different kinds of language linkage
54 /// (C++ [dcl.link]) that an entity may have.
59 };
60 
61 /// \brief A more specific kind of linkage than enum Linkage.
62 ///
63 /// This is relevant to CodeGen and AST file reading.
64 enum GVALinkage {
70 };
71 
72 inline bool isExternallyVisible(Linkage L) {
73  return L == ExternalLinkage || L == VisibleNoLinkage;
74 }
75 
77  if (L == UniqueExternalLinkage)
78  return ExternalLinkage;
79  if (L == VisibleNoLinkage)
80  return NoLinkage;
81  return L;
82 }
83 
85  return getFormalLinkage(L) == ExternalLinkage;
86 }
87 
88 /// \brief Compute the minimum linkage given two linkages.
89 ///
90 /// The linkage can be interpreted as a pair formed by the formal linkage and
91 /// a boolean for external visibility. This is just what getFormalLinkage and
92 /// isExternallyVisible return. We want the minimum of both components. The
93 /// Linkage enum is defined in an order that makes this simple, we just need
94 /// special cases for when VisibleNoLinkage would lose the visible bit and
95 /// become NoLinkage.
97  if (L2 == VisibleNoLinkage)
98  std::swap(L1, L2);
99  if (L1 == VisibleNoLinkage) {
100  if (L2 == InternalLinkage)
101  return NoLinkage;
102  if (L2 == UniqueExternalLinkage)
103  return NoLinkage;
104  }
105  return L1 < L2 ? L1 : L2;
106 }
107 
108 } // end namespace clang
109 
110 #endif // LLVM_CLANG_BASIC_LINKAGE_H
External linkage, which indicates that the entity can be referred to from other translation units...
Definition: Linkage.h:50
No linkage, which means that the entity is unique and can only be referred to from within its scope...
Definition: Linkage.h:28
Linkage
Describes the different kinds of linkage (C++ [basic.link], C99 6.2.2) that an entity may have...
Definition: Linkage.h:25
Linkage getFormalLinkage(Linkage L)
Definition: Linkage.h:76
bool isExternalFormalLinkage(Linkage L)
Definition: Linkage.h:84
bool isExternallyVisible(Linkage L)
Definition: Linkage.h:72
LanguageLinkage
Describes the different kinds of language linkage (C++ [dcl.link]) that an entity may have...
Definition: Linkage.h:55
Linkage minLinkage(Linkage L1, Linkage L2)
Compute the minimum linkage given two linkages.
Definition: Linkage.h:96
External linkage within a unique namespace.
Definition: Linkage.h:42
Internal linkage, which indicates that the entity can be referred to from within the translation unit...
Definition: Linkage.h:33
No linkage according to the standard, but is visible from other translation units because of types de...
Definition: Linkage.h:46
GVALinkage
A more specific kind of linkage than enum Linkage.
Definition: Linkage.h:64