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 72 inline bool isExternallyVisible(Linkage L) { 73 return L == ExternalLinkage || L == VisibleNoLinkage; 74 } 75 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 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. 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
