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1//===--- Visibility.h - Visibility enumeration and utilities ----*- C++ -*-===//
2//
3// The LLVM Compiler Infrastructure
4//
5// This file is distributed under the University of Illinois Open Source
6// License. See LICENSE.TXT for details.
7//
8//===----------------------------------------------------------------------===//
9///
10/// \file
11/// Defines the clang::Visibility enumeration and various utility
12/// functions.
13///
14//===----------------------------------------------------------------------===//
15#ifndef LLVM_CLANG_BASIC_VISIBILITY_H
16#define LLVM_CLANG_BASIC_VISIBILITY_H
17
18#include "clang/Basic/Linkage.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 uint8_t linkage_ : 3;
55 uint8_t visibility_ : 2;
56 uint8_t explicit_ : 1;
57
58 void setVisibility(Visibility V, bool E) { visibility_ = V; explicit_ = E; }
59public:
60 LinkageInfo() : linkage_(ExternalLinkage), visibility_(DefaultVisibility),
61 explicit_(false) {}
62 LinkageInfo(Linkage L, Visibility V, bool E)
63 : linkage_(L), visibility_(V), explicit_(E) {
64 assert(getLinkage() == L && getVisibility() == V &&
65 isVisibilityExplicit() == E && "Enum truncated!");
66 }
67
68 static LinkageInfo external() {
69 return LinkageInfo();
70 }
71 static LinkageInfo internal() {
72 return LinkageInfo(InternalLinkage, DefaultVisibility, false);
73 }
74 static LinkageInfo uniqueExternal() {
75 return LinkageInfo(UniqueExternalLinkage, DefaultVisibility, false);
76 }
77 static LinkageInfo none() {
78 return LinkageInfo(NoLinkage, DefaultVisibility, false);
79 }
80 static LinkageInfo visible_none() {
81 return LinkageInfo(VisibleNoLinkage, DefaultVisibility, false);
82 }
83
84 Linkage getLinkage() const { return (Linkage)linkage_; }
85 Visibility getVisibility() const { return (Visibility)visibility_; }
86 bool isVisibilityExplicit() const { return explicit_; }
87
88 void setLinkage(Linkage L) { linkage_ = L; }
89
90 void mergeLinkage(Linkage L) {
91 setLinkage(minLinkage(getLinkage(), L));
92 }
93 void mergeLinkage(LinkageInfo other) {
94 mergeLinkage(other.getLinkage());
95 }
96
97 void mergeExternalVisibility(Linkage L) {
98 Linkage ThisL = getLinkage();
99 if (!isExternallyVisible(L)) {
100 if (ThisL == VisibleNoLinkage)
101 ThisL = NoLinkage;
102 else if (ThisL == ExternalLinkage)
103 ThisL = UniqueExternalLinkage;
104 }
105 setLinkage(ThisL);
106 }
107 void mergeExternalVisibility(LinkageInfo Other) {
108 mergeExternalVisibility(Other.getLinkage());
109 }
110
111 /// Merge in the visibility 'newVis'.
112 void mergeVisibility(Visibility newVis, bool newExplicit) {
113 Visibility oldVis = getVisibility();
114
115 // Never increase visibility.
116 if (oldVis < newVis)
117 return;
118
119 // If the new visibility is the same as the old and the new
120 // visibility isn't explicit, we have nothing to add.
121 if (oldVis == newVis && !newExplicit)
122 return;
123
124 // Otherwise, we're either decreasing visibility or making our
125 // existing visibility explicit.
126 setVisibility(newVis, newExplicit);
127 }
128 void mergeVisibility(LinkageInfo other) {
129 mergeVisibility(other.getVisibility(), other.isVisibilityExplicit());
130 }
131
132 /// Merge both linkage and visibility.
133 void merge(LinkageInfo other) {
134 mergeLinkage(other);
135 mergeVisibility(other);
136 }
137
138 /// Merge linkage and conditionally merge visibility.
139 void mergeMaybeWithVisibility(LinkageInfo other, bool withVis) {
140 mergeLinkage(other);
141 if (withVis) mergeVisibility(other);
142 }
143};
144}
145
146#endif // LLVM_CLANG_BASIC_VISIBILITY_H
147

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