1//===- Linkage.h - Linkage enumeration and utilities ------------*- 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/// \file
10/// Defines the Linkage enumeration and various utility functions.
11//
12//===----------------------------------------------------------------------===//
13
14#ifndef LLVM_CLANG_BASIC_LINKAGE_H
15#define LLVM_CLANG_BASIC_LINKAGE_H
16
17#include <utility>
18
19namespace clang {
20
21/// Describes the different kinds of linkage
22/// (C++ [basic.link], C99 6.2.2) that an entity may have.
23enum Linkage : unsigned char {
24 /// No linkage, which means that the entity is unique and
25 /// can only be referred to from within its scope.
26 NoLinkage = 0,
27
28 /// Internal linkage, which indicates that the entity can
29 /// be referred to from within the translation unit (but not other
30 /// translation units).
31 InternalLinkage,
32
33 /// External linkage within a unique namespace.
34 ///
35 /// From the language perspective, these entities have external
36 /// linkage. However, since they reside in an anonymous namespace,
37 /// their names are unique to this translation unit, which is
38 /// equivalent to having internal linkage from the code-generation
39 /// point of view.
40 UniqueExternalLinkage,
41
42 /// No linkage according to the standard, but is visible from other
43 /// translation units because of types defined in a inline function.
44 VisibleNoLinkage,
45
46 /// Internal linkage according to the Modules TS, but can be referred
47 /// to from other translation units indirectly through inline functions and
48 /// templates in the module interface.
49 ModuleInternalLinkage,
50
51 /// Module linkage, which indicates that the entity can be referred
52 /// to from other translation units within the same module, and indirectly
53 /// from arbitrary other translation units through inline functions and
54 /// templates in the module interface.
55 ModuleLinkage,
56
57 /// External linkage, which indicates that the entity can
58 /// be referred to from other translation units.
59 ExternalLinkage
60};
61
62/// Describes the different kinds of language linkage
63/// (C++ [dcl.link]) that an entity may have.
64enum LanguageLinkage {
65 CLanguageLinkage,
66 CXXLanguageLinkage,
67 NoLanguageLinkage
68};
69
70/// A more specific kind of linkage than enum Linkage.
71///
72/// This is relevant to CodeGen and AST file reading.
73enum GVALinkage {
74 GVA_Internal,
75 GVA_AvailableExternally,
76 GVA_DiscardableODR,
77 GVA_StrongExternal,
78 GVA_StrongODR
79};
80
81inline bool isDiscardableGVALinkage(GVALinkage L) {
82 return L <= GVA_DiscardableODR;
83}
84
85/// Do we know that this will be the only definition of this symbol (excluding
86/// inlining-only definitions)?
87inline bool isUniqueGVALinkage(GVALinkage L) {
88 return L == GVA_Internal || L == GVA_StrongExternal;
89}
90
91inline bool isExternallyVisible(Linkage L) {
92 return L >= VisibleNoLinkage;
93}
94
95inline Linkage getFormalLinkage(Linkage L) {
96 switch (L) {
97 case UniqueExternalLinkage:
98 return ExternalLinkage;
99 case VisibleNoLinkage:
100 return NoLinkage;
101 case ModuleInternalLinkage:
102 return InternalLinkage;
103 default:
104 return L;
105 }
106}
107
108inline bool isExternalFormalLinkage(Linkage L) {
109 return getFormalLinkage(L) == ExternalLinkage;
110}
111
112/// Compute the minimum linkage given two linkages.
113///
114/// The linkage can be interpreted as a pair formed by the formal linkage and
115/// a boolean for external visibility. This is just what getFormalLinkage and
116/// isExternallyVisible return. We want the minimum of both components. The
117/// Linkage enum is defined in an order that makes this simple, we just need
118/// special cases for when VisibleNoLinkage would lose the visible bit and
119/// become NoLinkage.
120inline Linkage minLinkage(Linkage L1, Linkage L2) {
121 if (L2 == VisibleNoLinkage)
122 std::swap(L1, L2);
123 if (L1 == VisibleNoLinkage) {
124 if (L2 == InternalLinkage)
125 return NoLinkage;
126 if (L2 == UniqueExternalLinkage)
127 return NoLinkage;
128 }
129 return L1 < L2 ? L1 : L2;
130}
131
132} // namespace clang
133
134#endif // LLVM_CLANG_BASIC_LINKAGE_H
135