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 LLVM_PREFERRED_TYPE(Linkage)
55 uint8_t linkage_ : 3;
56 LLVM_PREFERRED_TYPE(Visibility)
57 uint8_t visibility_ : 2;
58 LLVM_PREFERRED_TYPE(bool)
59 uint8_t explicit_ : 1;
60
setVisibility(Visibility V,bool E)61 void setVisibility(Visibility V, bool E) { visibility_ = V; explicit_ = E; }
62 public:
LinkageInfo()63 LinkageInfo()
64 : linkage_(llvm::to_underlying(Linkage::External)),
65 visibility_(DefaultVisibility), explicit_(false) {}
LinkageInfo(Linkage L,Visibility V,bool E)66 LinkageInfo(Linkage L, Visibility V, bool E)
67 : linkage_(llvm::to_underlying(L)), visibility_(V), explicit_(E) {
68 assert(getLinkage() == L && getVisibility() == V &&
69 isVisibilityExplicit() == E && "Enum truncated!");
70 }
71
external()72 static LinkageInfo external() {
73 return LinkageInfo();
74 }
internal()75 static LinkageInfo internal() {
76 return LinkageInfo(Linkage::Internal, DefaultVisibility, false);
77 }
uniqueExternal()78 static LinkageInfo uniqueExternal() {
79 return LinkageInfo(Linkage::UniqueExternal, DefaultVisibility, false);
80 }
none()81 static LinkageInfo none() {
82 return LinkageInfo(Linkage::None, DefaultVisibility, false);
83 }
visible_none()84 static LinkageInfo visible_none() {
85 return LinkageInfo(Linkage::VisibleNone, DefaultVisibility, false);
86 }
87
getLinkage()88 Linkage getLinkage() const { return static_cast<Linkage>(linkage_); }
getVisibility()89 Visibility getVisibility() const { return (Visibility)visibility_; }
isVisibilityExplicit()90 bool isVisibilityExplicit() const { return explicit_; }
91
setLinkage(Linkage L)92 void setLinkage(Linkage L) { linkage_ = llvm::to_underlying(L); }
93
mergeLinkage(Linkage L)94 void mergeLinkage(Linkage L) {
95 setLinkage(minLinkage(getLinkage(), L));
96 }
mergeLinkage(LinkageInfo other)97 void mergeLinkage(LinkageInfo other) {
98 mergeLinkage(other.getLinkage());
99 }
100
mergeExternalVisibility(Linkage L)101 void mergeExternalVisibility(Linkage L) {
102 Linkage ThisL = getLinkage();
103 if (!isExternallyVisible(L)) {
104 if (ThisL == Linkage::VisibleNone)
105 ThisL = Linkage::None;
106 else if (ThisL == Linkage::External)
107 ThisL = Linkage::UniqueExternal;
108 }
109 setLinkage(ThisL);
110 }
mergeExternalVisibility(LinkageInfo Other)111 void mergeExternalVisibility(LinkageInfo Other) {
112 mergeExternalVisibility(Other.getLinkage());
113 }
114
115 /// Merge in the visibility 'newVis'.
mergeVisibility(Visibility newVis,bool newExplicit)116 void mergeVisibility(Visibility newVis, bool newExplicit) {
117 Visibility oldVis = getVisibility();
118
119 // Never increase visibility.
120 if (oldVis < newVis)
121 return;
122
123 // If the new visibility is the same as the old and the new
124 // visibility isn't explicit, we have nothing to add.
125 if (oldVis == newVis && !newExplicit)
126 return;
127
128 // Otherwise, we're either decreasing visibility or making our
129 // existing visibility explicit.
130 setVisibility(newVis, newExplicit);
131 }
mergeVisibility(LinkageInfo other)132 void mergeVisibility(LinkageInfo other) {
133 mergeVisibility(other.getVisibility(), other.isVisibilityExplicit());
134 }
135
136 /// Merge both linkage and visibility.
merge(LinkageInfo other)137 void merge(LinkageInfo other) {
138 mergeLinkage(other);
139 mergeVisibility(other);
140 }
141
142 /// Merge linkage and conditionally merge visibility.
mergeMaybeWithVisibility(LinkageInfo other,bool withVis)143 void mergeMaybeWithVisibility(LinkageInfo other, bool withVis) {
144 mergeLinkage(other);
145 if (withVis) mergeVisibility(other);
146 }
147 };
148 }
149
150 #endif // LLVM_CLANG_BASIC_VISIBILITY_H
151