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
minVisibility(Visibility L,Visibility R)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
setVisibility(Visibility V,bool E)58 void setVisibility(Visibility V, bool E) { visibility_ = V; explicit_ = E; }
59 public:
LinkageInfo()60 LinkageInfo()
61 : linkage_(llvm::to_underlying(Linkage::External)),
62 visibility_(DefaultVisibility), explicit_(false) {}
LinkageInfo(Linkage L,Visibility V,bool E)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
external()69 static LinkageInfo external() {
70 return LinkageInfo();
71 }
internal()72 static LinkageInfo internal() {
73 return LinkageInfo(Linkage::Internal, DefaultVisibility, false);
74 }
uniqueExternal()75 static LinkageInfo uniqueExternal() {
76 return LinkageInfo(Linkage::UniqueExternal, DefaultVisibility, false);
77 }
none()78 static LinkageInfo none() {
79 return LinkageInfo(Linkage::None, DefaultVisibility, false);
80 }
visible_none()81 static LinkageInfo visible_none() {
82 return LinkageInfo(Linkage::VisibleNone, DefaultVisibility, false);
83 }
84
getLinkage()85 Linkage getLinkage() const { return static_cast<Linkage>(linkage_); }
getVisibility()86 Visibility getVisibility() const { return (Visibility)visibility_; }
isVisibilityExplicit()87 bool isVisibilityExplicit() const { return explicit_; }
88
setLinkage(Linkage L)89 void setLinkage(Linkage L) { linkage_ = llvm::to_underlying(L); }
90
mergeLinkage(Linkage L)91 void mergeLinkage(Linkage L) {
92 setLinkage(minLinkage(getLinkage(), L));
93 }
mergeLinkage(LinkageInfo other)94 void mergeLinkage(LinkageInfo other) {
95 mergeLinkage(other.getLinkage());
96 }
97
mergeExternalVisibility(Linkage L)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 }
mergeExternalVisibility(LinkageInfo Other)108 void mergeExternalVisibility(LinkageInfo Other) {
109 mergeExternalVisibility(Other.getLinkage());
110 }
111
112 /// Merge in the visibility 'newVis'.
mergeVisibility(Visibility newVis,bool newExplicit)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 }
mergeVisibility(LinkageInfo other)129 void mergeVisibility(LinkageInfo other) {
130 mergeVisibility(other.getVisibility(), other.isVisibilityExplicit());
131 }
132
133 /// Merge both linkage and visibility.
merge(LinkageInfo other)134 void merge(LinkageInfo other) {
135 mergeLinkage(other);
136 mergeVisibility(other);
137 }
138
139 /// Merge linkage and conditionally merge visibility.
mergeMaybeWithVisibility(LinkageInfo other,bool withVis)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