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
22namespace 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.
34enum 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
49inline Visibility minVisibility(Visibility L, Visibility R) {
50 return L < R ? L : R;
51}
52
53class 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
61 void setVisibility(Visibility V, bool E) { visibility_ = V; explicit_ = E; }
62public:
63 LinkageInfo()
64 : linkage_(llvm::to_underlying(E: Linkage::External)),
65 visibility_(DefaultVisibility), explicit_(false) {}
66 LinkageInfo(Linkage L, Visibility V, bool E)
67 : linkage_(llvm::to_underlying(E: L)), visibility_(V), explicit_(E) {
68 assert(getLinkage() == L && getVisibility() == V &&
69 isVisibilityExplicit() == E && "Enum truncated!");
70 }
71
72 static LinkageInfo external() {
73 return LinkageInfo();
74 }
75 static LinkageInfo internal() {
76 return LinkageInfo(Linkage::Internal, DefaultVisibility, false);
77 }
78 static LinkageInfo uniqueExternal() {
79 return LinkageInfo(Linkage::UniqueExternal, DefaultVisibility, false);
80 }
81 static LinkageInfo none() {
82 return LinkageInfo(Linkage::None, DefaultVisibility, false);
83 }
84 static LinkageInfo visible_none() {
85 return LinkageInfo(Linkage::VisibleNone, DefaultVisibility, false);
86 }
87
88 Linkage getLinkage() const { return static_cast<Linkage>(linkage_); }
89 Visibility getVisibility() const { return (Visibility)visibility_; }
90 bool isVisibilityExplicit() const { return explicit_; }
91
92 void setLinkage(Linkage L) { linkage_ = llvm::to_underlying(E: L); }
93
94 void mergeLinkage(Linkage L) {
95 setLinkage(minLinkage(L1: getLinkage(), L2: L));
96 }
97 void mergeLinkage(LinkageInfo other) {
98 mergeLinkage(L: other.getLinkage());
99 }
100
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 }
111 void mergeExternalVisibility(LinkageInfo Other) {
112 mergeExternalVisibility(L: Other.getLinkage());
113 }
114
115 /// Merge in the visibility 'newVis'.
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(V: newVis, E: newExplicit);
131 }
132 void mergeVisibility(LinkageInfo other) {
133 mergeVisibility(newVis: other.getVisibility(), newExplicit: other.isVisibilityExplicit());
134 }
135
136 /// Merge both linkage and visibility.
137 void merge(LinkageInfo other) {
138 mergeLinkage(other);
139 mergeVisibility(other);
140 }
141
142 /// Merge linkage and conditionally merge visibility.
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

source code of clang/include/clang/Basic/Visibility.h