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