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
21namespace 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.
33enum 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
48inline Visibility minVisibility(Visibility L, Visibility R) {
49 return L < R ? L : R;
50}
51
52class LinkageInfo {
53 uint8_t linkage_ : 3;
54 uint8_t visibility_ : 2;
55 uint8_t explicit_ : 1;
56
57 void setVisibility(Visibility V, bool E) { visibility_ = V; explicit_ = E; }
58public:
59 LinkageInfo() : linkage_(ExternalLinkage), visibility_(DefaultVisibility),
60 explicit_(false) {}
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
67 static LinkageInfo external() {
68 return LinkageInfo();
69 }
70 static LinkageInfo internal() {
71 return LinkageInfo(InternalLinkage, DefaultVisibility, false);
72 }
73 static LinkageInfo uniqueExternal() {
74 return LinkageInfo(UniqueExternalLinkage, DefaultVisibility, false);
75 }
76 static LinkageInfo none() {
77 return LinkageInfo(NoLinkage, DefaultVisibility, false);
78 }
79 static LinkageInfo visible_none() {
80 return LinkageInfo(VisibleNoLinkage, DefaultVisibility, false);
81 }
82
83 Linkage getLinkage() const { return (Linkage)linkage_; }
84 Visibility getVisibility() const { return (Visibility)visibility_; }
85 bool isVisibilityExplicit() const { return explicit_; }
86
87 void setLinkage(Linkage L) { linkage_ = L; }
88
89 void mergeLinkage(Linkage L) {
90 setLinkage(minLinkage(getLinkage(), L));
91 }
92 void mergeLinkage(LinkageInfo other) {
93 mergeLinkage(other.getLinkage());
94 }
95
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 }
106 void mergeExternalVisibility(LinkageInfo Other) {
107 mergeExternalVisibility(Other.getLinkage());
108 }
109
110 /// Merge in the visibility 'newVis'.
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 }
127 void mergeVisibility(LinkageInfo other) {
128 mergeVisibility(other.getVisibility(), other.isVisibilityExplicit());
129 }
130
131 /// Merge both linkage and visibility.
132 void merge(LinkageInfo other) {
133 mergeLinkage(other);
134 mergeVisibility(other);
135 }
136
137 /// Merge linkage and conditionally merge visibility.
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