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).
33 InternalLinkage,
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.
42 UniqueExternalLinkage,
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.
46 VisibleNoLinkage,
47
48 /// \brief External linkage, which indicates that the entity can
49 /// be referred to from other translation units.
50 ExternalLinkage
51 };
52
53 /// \brief Describes the different kinds of language linkage
54 /// (C++ [dcl.link]) that an entity may have.
55 enum LanguageLinkage {
56 CLanguageLinkage,
57 CXXLanguageLinkage,
58 NoLanguageLinkage
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 {
65 GVA_Internal,
66 GVA_AvailableExternally,
67 GVA_DiscardableODR,
68 GVA_StrongExternal,
69 GVA_StrongODR
70 };
71
isExternallyVisible(Linkage L)72 inline bool isExternallyVisible(Linkage L) {
73 return L == ExternalLinkage || L == VisibleNoLinkage;
74 }
75
getFormalLinkage(Linkage L)76 inline Linkage getFormalLinkage(Linkage L) {
77 if (L == UniqueExternalLinkage)
78 return ExternalLinkage;
79 if (L == VisibleNoLinkage)
80 return NoLinkage;
81 return L;
82 }
83
isExternalFormalLinkage(Linkage L)84 inline bool isExternalFormalLinkage(Linkage L) {
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.
minLinkage(Linkage L1,Linkage L2)96 inline Linkage minLinkage(Linkage L1, Linkage L2) {
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
111