1 //===- Linkage.h - Linkage enumeration and utilities ------------*- C++ -*-===//
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
7 //===----------------------------------------------------------------------===//
10 /// Defines the Linkage enumeration and various utility functions.
12 //===----------------------------------------------------------------------===//
14 #ifndef LLVM_CLANG_BASIC_LINKAGE_H
15 #define LLVM_CLANG_BASIC_LINKAGE_H
21 /// Describes the different kinds of linkage
22 /// (C++ [basic.link], C99 6.2.2) that an entity may have.
23 enum Linkage : unsigned char {
24 /// No linkage, which means that the entity is unique and
25 /// can only be referred to from within its scope.
28 /// Internal linkage, which indicates that the entity can
29 /// be referred to from within the translation unit (but not other
30 /// translation units).
33 /// External linkage within a unique namespace.
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
40 UniqueExternalLinkage,
42 /// No linkage according to the standard, but is visible from other
43 /// translation units because of types defined in a inline function.
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,
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.
57 /// External linkage, which indicates that the entity can
58 /// be referred to from other translation units.
62 /// Describes the different kinds of language linkage
63 /// (C++ [dcl.link]) that an entity may have.
64 enum LanguageLinkage {
70 /// A more specific kind of linkage than enum Linkage.
72 /// This is relevant to CodeGen and AST file reading.
75 GVA_AvailableExternally,
81 inline bool isDiscardableGVALinkage(GVALinkage L) {
82 return L <= GVA_DiscardableODR;
85 inline bool isExternallyVisible(Linkage L) {
86 return L >= VisibleNoLinkage;
89 inline Linkage getFormalLinkage(Linkage L) {
91 case UniqueExternalLinkage:
92 return ExternalLinkage;
93 case VisibleNoLinkage:
95 case ModuleInternalLinkage:
96 return InternalLinkage;
102 inline bool isExternalFormalLinkage(Linkage L) {
103 return getFormalLinkage(L) == ExternalLinkage;
106 /// Compute the minimum linkage given two linkages.
108 /// The linkage can be interpreted as a pair formed by the formal linkage and
109 /// a boolean for external visibility. This is just what getFormalLinkage and
110 /// isExternallyVisible return. We want the minimum of both components. The
111 /// Linkage enum is defined in an order that makes this simple, we just need
112 /// special cases for when VisibleNoLinkage would lose the visible bit and
113 /// become NoLinkage.
114 inline Linkage minLinkage(Linkage L1, Linkage L2) {
115 if (L2 == VisibleNoLinkage)
117 if (L1 == VisibleNoLinkage) {
118 if (L2 == InternalLinkage)
120 if (L2 == UniqueExternalLinkage)
123 return L1 < L2 ? L1 : L2;
128 #endif // LLVM_CLANG_BASIC_LINKAGE_H