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 68 inline bool isExternallyVisible(Linkage L) { 69 return L == ExternalLinkage || L == VisibleNoLinkage; 70 } 71 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 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. 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
