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 namespace clang {
18
19 /// \brief Describes the different kinds of linkage
20 /// (C++ [basic.link], C99 6.2.2) that an entity may have.
21 enum Linkage : unsigned char {
22 /// \brief No linkage, which means that the entity is unique and
23 /// can only be referred to from within its scope.
24 NoLinkage = 0,
25
26 /// \brief Internal linkage, which indicates that the entity can
27 /// be referred to from within the translation unit (but not other
28 /// translation units).
29 InternalLinkage,
30
31 /// \brief External linkage within a unique namespace.
32 ///
33 /// From the language perspective, these entities have external
34 /// linkage. However, since they reside in an anonymous namespace,
35 /// their names are unique to this translation unit, which is
36 /// equivalent to having internal linkage from the code-generation
37 /// point of view.
38 UniqueExternalLinkage,
39
40 /// \brief No linkage according to the standard, but is visible from other
41 /// translation units because of types defined in a inline function.
42 VisibleNoLinkage,
43
44 /// \brief External linkage, which indicates that the entity can
45 /// be referred to from other translation units.
46 ExternalLinkage
47 };
48
49 /// \brief Describes the different kinds of language linkage
50 /// (C++ [dcl.link]) that an entity may have.
51 enum LanguageLinkage {
52 CLanguageLinkage,
53 CXXLanguageLinkage,
54 NoLanguageLinkage
55 };
56
57 /// \brief A more specific kind of linkage than enum Linkage.
58 ///
59 /// This is relevant to CodeGen and AST file reading.
60 enum GVALinkage {
61 GVA_Internal,
62 GVA_AvailableExternally,
63 GVA_DiscardableODR,
64 GVA_StrongExternal,
65 GVA_StrongODR
66 };
67
isExternallyVisible(Linkage L)68 inline bool isExternallyVisible(Linkage L) {
69 return L == ExternalLinkage || L == VisibleNoLinkage;
70 }
71
getFormalLinkage(Linkage L)72 inline Linkage getFormalLinkage(Linkage L) {
73 if (L == UniqueExternalLinkage)
74 return ExternalLinkage;
75 if (L == VisibleNoLinkage)
76 return NoLinkage;
77 return L;
78 }
79
isExternalFormalLinkage(Linkage L)80 inline bool isExternalFormalLinkage(Linkage L) {
81 return getFormalLinkage(L) == ExternalLinkage;
82 }
83
84 /// \brief Compute the minimum linkage given two linkages.
85 ///
86 /// The linkage can be interpreted as a pair formed by the formal linkage and
87 /// a boolean for external visibility. This is just what getFormalLinkage and
88 /// isExternallyVisible return. We want the minimum of both components. The
89 /// Linkage enum is defined in an order that makes this simple, we just need
90 /// special cases for when VisibleNoLinkage would lose the visible bit and
91 /// become NoLinkage.
minLinkage(Linkage L1,Linkage L2)92 inline Linkage minLinkage(Linkage L1, Linkage L2) {
93 if (L2 == VisibleNoLinkage)
94 std::swap(L1, L2);
95 if (L1 == VisibleNoLinkage) {
96 if (L2 == InternalLinkage)
97 return NoLinkage;
98 if (L2 == UniqueExternalLinkage)
99 return NoLinkage;
100 }
101 return L1 < L2 ? L1 : L2;
102 }
103
104 } // end namespace clang
105
106 #endif // LLVM_CLANG_BASIC_LINKAGE_H
107