1 //===--- Visibility.h - Visibility 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 clang::Visibility enumeration and various utility 11 /// functions. 12 /// 13 //===----------------------------------------------------------------------===// 14 #ifndef LLVM_CLANG_BASIC_VISIBILITY_H 15 #define LLVM_CLANG_BASIC_VISIBILITY_H 16 17 #include "clang/Basic/Linkage.h" 18 #include "llvm/ADT/STLForwardCompat.h" 19 #include <cassert> 20 #include <cstdint> 21 22 namespace clang { 23 24 /// Describes the different kinds of visibility that a declaration 25 /// may have. 26 /// 27 /// Visibility determines how a declaration interacts with the dynamic 28 /// linker. It may also affect whether the symbol can be found by runtime 29 /// symbol lookup APIs. 30 /// 31 /// Visibility is not described in any language standard and 32 /// (nonetheless) sometimes has odd behavior. Not all platforms 33 /// support all visibility kinds. 34 enum Visibility { 35 /// Objects with "hidden" visibility are not seen by the dynamic 36 /// linker. 37 HiddenVisibility, 38 39 /// Objects with "protected" visibility are seen by the dynamic 40 /// linker but always dynamically resolve to an object within this 41 /// shared object. 42 ProtectedVisibility, 43 44 /// Objects with "default" visibility are seen by the dynamic linker 45 /// and act like normal objects. 46 DefaultVisibility 47 }; 48 49 inline Visibility minVisibility(Visibility L, Visibility R) { 50 return L < R ? L : R; 51 } 52 53 class LinkageInfo { 54 uint8_t linkage_ : 3; 55 uint8_t visibility_ : 2; 56 uint8_t explicit_ : 1; 57 58 void setVisibility(Visibility V, bool E) { visibility_ = V; explicit_ = E; } 59 public: 60 LinkageInfo() 61 : linkage_(llvm::to_underlying(Linkage::External)), 62 visibility_(DefaultVisibility), explicit_(false) {} 63 LinkageInfo(Linkage L, Visibility V, bool E) 64 : linkage_(llvm::to_underlying(L)), visibility_(V), explicit_(E) { 65 assert(getLinkage() == L && getVisibility() == V && 66 isVisibilityExplicit() == E && "Enum truncated!"); 67 } 68 69 static LinkageInfo external() { 70 return LinkageInfo(); 71 } 72 static LinkageInfo internal() { 73 return LinkageInfo(Linkage::Internal, DefaultVisibility, false); 74 } 75 static LinkageInfo uniqueExternal() { 76 return LinkageInfo(Linkage::UniqueExternal, DefaultVisibility, false); 77 } 78 static LinkageInfo none() { 79 return LinkageInfo(Linkage::None, DefaultVisibility, false); 80 } 81 static LinkageInfo visible_none() { 82 return LinkageInfo(Linkage::VisibleNone, DefaultVisibility, false); 83 } 84 85 Linkage getLinkage() const { return static_cast<Linkage>(linkage_); } 86 Visibility getVisibility() const { return (Visibility)visibility_; } 87 bool isVisibilityExplicit() const { return explicit_; } 88 89 void setLinkage(Linkage L) { linkage_ = llvm::to_underlying(L); } 90 91 void mergeLinkage(Linkage L) { 92 setLinkage(minLinkage(getLinkage(), L)); 93 } 94 void mergeLinkage(LinkageInfo other) { 95 mergeLinkage(other.getLinkage()); 96 } 97 98 void mergeExternalVisibility(Linkage L) { 99 Linkage ThisL = getLinkage(); 100 if (!isExternallyVisible(L)) { 101 if (ThisL == Linkage::VisibleNone) 102 ThisL = Linkage::None; 103 else if (ThisL == Linkage::External) 104 ThisL = Linkage::UniqueExternal; 105 } 106 setLinkage(ThisL); 107 } 108 void mergeExternalVisibility(LinkageInfo Other) { 109 mergeExternalVisibility(Other.getLinkage()); 110 } 111 112 /// Merge in the visibility 'newVis'. 113 void mergeVisibility(Visibility newVis, bool newExplicit) { 114 Visibility oldVis = getVisibility(); 115 116 // Never increase visibility. 117 if (oldVis < newVis) 118 return; 119 120 // If the new visibility is the same as the old and the new 121 // visibility isn't explicit, we have nothing to add. 122 if (oldVis == newVis && !newExplicit) 123 return; 124 125 // Otherwise, we're either decreasing visibility or making our 126 // existing visibility explicit. 127 setVisibility(newVis, newExplicit); 128 } 129 void mergeVisibility(LinkageInfo other) { 130 mergeVisibility(other.getVisibility(), other.isVisibilityExplicit()); 131 } 132 133 /// Merge both linkage and visibility. 134 void merge(LinkageInfo other) { 135 mergeLinkage(other); 136 mergeVisibility(other); 137 } 138 139 /// Merge linkage and conditionally merge visibility. 140 void mergeMaybeWithVisibility(LinkageInfo other, bool withVis) { 141 mergeLinkage(other); 142 if (withVis) mergeVisibility(other); 143 } 144 }; 145 } 146 147 #endif // LLVM_CLANG_BASIC_VISIBILITY_H 148