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+//===--- Visibility.h - Visibility enumeration and utilities ----*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+///
+/// \file
+/// Defines the clang::Visibility enumeration and various utility
+/// functions.
+///
+//===----------------------------------------------------------------------===//
+#ifndef LLVM_CLANG_BASIC_VISIBILITY_H
+#define LLVM_CLANG_BASIC_VISIBILITY_H
+
+#include "clang/Basic/Linkage.h"
+#include <cassert>
+#include <cstdint>
+
+namespace clang {
+
+/// Describes the different kinds of visibility that a declaration
+/// may have.
+///
+/// Visibility determines how a declaration interacts with the dynamic
+/// linker. It may also affect whether the symbol can be found by runtime
+/// symbol lookup APIs.
+///
+/// Visibility is not described in any language standard and
+/// (nonetheless) sometimes has odd behavior. Not all platforms
+/// support all visibility kinds.
+enum Visibility {
+ /// Objects with "hidden" visibility are not seen by the dynamic
+ /// linker.
+ HiddenVisibility,
+
+ /// Objects with "protected" visibility are seen by the dynamic
+ /// linker but always dynamically resolve to an object within this
+ /// shared object.
+ ProtectedVisibility,
+
+ /// Objects with "default" visibility are seen by the dynamic linker
+ /// and act like normal objects.
+ DefaultVisibility
+};
+
+inline Visibility minVisibility(Visibility L, Visibility R) {
+ return L < R ? L : R;
+}
+
+class LinkageInfo {
+ uint8_t linkage_ : 3;
+ uint8_t visibility_ : 2;
+ uint8_t explicit_ : 1;
+
+ void setVisibility(Visibility V, bool E) { visibility_ = V; explicit_ = E; }
+public:
+ LinkageInfo() : linkage_(ExternalLinkage), visibility_(DefaultVisibility),
+ explicit_(false) {}
+ LinkageInfo(Linkage L, Visibility V, bool E)
+ : linkage_(L), visibility_(V), explicit_(E) {
+ assert(getLinkage() == L && getVisibility() == V &&
+ isVisibilityExplicit() == E && "Enum truncated!");
+ }
+
+ static LinkageInfo external() {
+ return LinkageInfo();
+ }
+ static LinkageInfo internal() {
+ return LinkageInfo(InternalLinkage, DefaultVisibility, false);
+ }
+ static LinkageInfo uniqueExternal() {
+ return LinkageInfo(UniqueExternalLinkage, DefaultVisibility, false);
+ }
+ static LinkageInfo none() {
+ return LinkageInfo(NoLinkage, DefaultVisibility, false);
+ }
+ static LinkageInfo visible_none() {
+ return LinkageInfo(VisibleNoLinkage, DefaultVisibility, false);
+ }
+
+ Linkage getLinkage() const { return (Linkage)linkage_; }
+ Visibility getVisibility() const { return (Visibility)visibility_; }
+ bool isVisibilityExplicit() const { return explicit_; }
+
+ void setLinkage(Linkage L) { linkage_ = L; }
+
+ void mergeLinkage(Linkage L) {
+ setLinkage(minLinkage(getLinkage(), L));
+ }
+ void mergeLinkage(LinkageInfo other) {
+ mergeLinkage(other.getLinkage());
+ }
+
+ void mergeExternalVisibility(Linkage L) {
+ Linkage ThisL = getLinkage();
+ if (!isExternallyVisible(L)) {
+ if (ThisL == VisibleNoLinkage)
+ ThisL = NoLinkage;
+ else if (ThisL == ExternalLinkage)
+ ThisL = UniqueExternalLinkage;
+ }
+ setLinkage(ThisL);
+ }
+ void mergeExternalVisibility(LinkageInfo Other) {
+ mergeExternalVisibility(Other.getLinkage());
+ }
+
+ /// Merge in the visibility 'newVis'.
+ void mergeVisibility(Visibility newVis, bool newExplicit) {
+ Visibility oldVis = getVisibility();
+
+ // Never increase visibility.
+ if (oldVis < newVis)
+ return;
+
+ // If the new visibility is the same as the old and the new
+ // visibility isn't explicit, we have nothing to add.
+ if (oldVis == newVis && !newExplicit)
+ return;
+
+ // Otherwise, we're either decreasing visibility or making our
+ // existing visibility explicit.
+ setVisibility(newVis, newExplicit);
+ }
+ void mergeVisibility(LinkageInfo other) {
+ mergeVisibility(other.getVisibility(), other.isVisibilityExplicit());
+ }
+
+ /// Merge both linkage and visibility.
+ void merge(LinkageInfo other) {
+ mergeLinkage(other);
+ mergeVisibility(other);
+ }
+
+ /// Merge linkage and conditionally merge visibility.
+ void mergeMaybeWithVisibility(LinkageInfo other, bool withVis) {
+ mergeLinkage(other);
+ if (withVis) mergeVisibility(other);
+ }
+};
+}
+
+#endif // LLVM_CLANG_BASIC_VISIBILITY_H