Module.h

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//===- Module.h - Describe a module -----------------------------*- 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::Module class, which describes a module in the
/// source code.
//
//===----------------------------------------------------------------------===//
 
#ifndef LLVM_CLANG_BASIC_MODULE_H
#define LLVM_CLANG_BASIC_MODULE_H
 
#include "clang/Basic/DirectoryEntry.h"
#include "clang/Basic/FileEntry.h"
#include "clang/Basic/SourceLocation.h"
#include "llvm/ADT/ArrayRef.h"
#include "llvm/ADT/DenseSet.h"
#include "llvm/ADT/PointerIntPair.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/SetVector.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/StringMap.h"
#include "llvm/ADT/StringRef.h"
#include "llvm/ADT/iterator_range.h"
#include <array>
#include <cassert>
#include <cstdint>
#include <ctime>
#include <iterator>
#include <optional>
#include <string>
#include <utility>
#include <variant>
#include <vector>
 
namespace llvm {
 
class raw_ostream;
 
} // namespace llvm
 
namespace clang {
 
class FileManager;
class LangOptions;
class Module;
class ModuleMap;
class TargetInfo;
 
/// Interface for on-demand deserialization of submodules stored in a PCM file.
class ExternalSubmoduleSource {
public:
  virtual Module *getSubmodule(uint32_t GlobalID) = 0;
  virtual ~ExternalSubmoduleSource() = default;
};
 
/// Describes the name of a module.
using ModuleId = SmallVector<std::pair<std::string, SourceLocation>, 2>;
 
/// Deduplication key for a loaded module file in \c ModuleManager.
///
/// For implicitly-built modules, this is a pointer representing the module
/// cache directory and the module file name with the (optional) context hash.
/// This enables using inode-based canonicalization of the user-provided module
/// cache path without hitting issues on file systems that recycle inodes for
/// recompiled module files.
///
/// For explicitly-built modules, this is \c FileEntry.
/// This uses \c FileManager's inode-based canonicalization of the user-provided
/// module file path. Because input explicitly-built modules do not change
/// during the lifetime of the compiler, inode recycling is not of concern here.
///
/// For in-memory modules, this is the \c MemoryBuffer in InMemoryModuleCache.
class ModuleFileKey {
  /// The entity used for deduplication.
  const void *Ptr;
  /// The path relative to the module cache path for implicit module file, empty
  /// for other kinds of module files.
  std::string ImplicitModulePathSuffix;
 
  friend llvm::DenseMapInfo<ModuleFileKey>;
 
public:
  ModuleFileKey(const void *ModuleFile) : Ptr(ModuleFile) {}
 
  ModuleFileKey(const void *ModuleCacheDir, StringRef PathSuffix)
      : Ptr(ModuleCacheDir), ImplicitModulePathSuffix(PathSuffix) {}
 
  bool operator==(const ModuleFileKey &Other) const {
    return Ptr == Other.Ptr &&
           ImplicitModulePathSuffix == Other.ImplicitModulePathSuffix;
  }
 
  bool operator!=(const ModuleFileKey &Other) const {
    return !operator==(Other);
  }
};
 
/// Identifies a module file to be loaded.
///
/// For implicitly-built module files, the path is split into the module cache
/// path and the module file name with the (optional) context hash. For all
/// other types of module files, this is just the file system path.
class ModuleFileName {
  enum Kind : unsigned {
    InMemory = 0,
    Explicit = 1,
    ImplicitSuffixLength,
  };
 
  std::string Path;
  /// The kind of the module file (\c Kind), or the length of the implicit
  /// module file name suffix in \c Path (integer values 2+).
  Kind KindOrSuffixLength;
 
public:
  /// Creates an empty module file name.
  ModuleFileName() = default;
 
  /// Creates a file name from the raw kind value.
  static ModuleFileName makeFromRaw(StringRef Name, unsigned RawKind) {
    ModuleFileName File;
    File.Path = Name;
    File.KindOrSuffixLength = static_cast<Kind>(RawKind);
    return File;
  }
 
  /// Creates a file name for an in-memory module.
  static ModuleFileName makeInMemory(StringRef Name) {
    ModuleFileName File;
    File.Path = Name;
    File.KindOrSuffixLength = InMemory;
    return File;
  }
 
  /// Creates a file name for an explicit module.
  static ModuleFileName makeExplicit(std::string Name) {
    ModuleFileName File;
    File.Path = std::move(Name);
    File.KindOrSuffixLength = Explicit;
    return File;
  }
 
  /// Creates a file name for an explicit module.
  static ModuleFileName makeExplicit(StringRef Name) {
    return makeExplicit(Name.str());
  }
 
  /// Creates a file name for an implicit module.
  static ModuleFileName makeImplicit(std::string Name, unsigned SuffixLength) {
    assert(SuffixLength >= 2 && "Invalid suffix for implicit module file name");
    assert(SuffixLength <= Name.size() &&
           "Suffix for implicit module file name out-of-bounds");
    ModuleFileName File;
    File.Path = std::move(Name);
    File.KindOrSuffixLength = static_cast<Kind>(SuffixLength);
    return File;
  }
 
  /// Creates a file name for an implicit module.
  static ModuleFileName makeImplicit(StringRef Name, unsigned SuffixLength) {
    return makeImplicit(Name.str(), SuffixLength);
  }
 
  /// Returns the suffix length for an implicit module name, zero otherwise.
  unsigned getImplicitModuleSuffixLength() const {
    switch (KindOrSuffixLength) {
    case InMemory:
    case Explicit:
      return 0;
    default:
      return KindOrSuffixLength;
    }
  }
 
  /// Returns \c true iff this is an in-memory module file, \c false otherwise.
  bool isInMemory() const { return KindOrSuffixLength == InMemory; }
 
  /// Returns the raw value representing the kind of the module file.
  unsigned getRawKind() const { return KindOrSuffixLength; }
 
  /// Returns the plain module file name.
  StringRef str() const { return Path; }
 
  /// Converts to StringRef representing the plain module file name.
  operator StringRef() const { return Path; }
 
  /// Checks whether the module file name is empty.
  bool empty() const { return Path.empty(); }
};
 
/// The signature of a module, which is a hash of the AST content.
struct ASTFileSignature : std::array<uint8_t, 20> {
  using BaseT = std::array<uint8_t, 20>;
 
  static constexpr size_t size = std::tuple_size<BaseT>::value;
 
  ASTFileSignature(BaseT S = {{0}}) : BaseT(std::move(S)) {}
 
  explicit operator bool() const { return *this != BaseT({{0}}); }
 
  // Support implicit cast to ArrayRef.  Note that ASTFileSignature::size
  // prevents implicit cast to ArrayRef because one of the implicit constructors
  // of ArrayRef requires access to BaseT::size.
  operator ArrayRef<uint8_t>() const { return ArrayRef<uint8_t>(data(), size); }
 
  /// Returns the value truncated to the size of an uint64_t.
  uint64_t truncatedValue() const {
    uint64_t Value = 0;
    static_assert(sizeof(*this) >= sizeof(uint64_t), "No need to truncate.");
    for (unsigned I = 0; I < sizeof(uint64_t); ++I)
      Value |= static_cast<uint64_t>((*this)[I]) << (I * 8);
    return Value;
  }
 
  static ASTFileSignature create(std::array<uint8_t, 20> Bytes) {
    return ASTFileSignature(std::move(Bytes));
  }
 
  static ASTFileSignature createDISentinel() {
    ASTFileSignature Sentinel;
    Sentinel.fill(0xFF);
    return Sentinel;
  }
 
  static ASTFileSignature createDummy() {
    ASTFileSignature Dummy;
    Dummy.fill(0x00);
    return Dummy;
  }
 
  template <typename InputIt>
  static ASTFileSignature create(InputIt First, InputIt Last) {
    assert(std::distance(First, Last) == size &&
           "Wrong amount of bytes to create an ASTFileSignature");
 
    ASTFileSignature Signature;
    std::copy(First, Last, Signature.begin());
    return Signature;
  }
};
 
/// The set of attributes that can be attached to a module.
struct ModuleAttributes {
  /// Whether this is a system module.
  LLVM_PREFERRED_TYPE(bool)
  unsigned IsSystem : 1;
 
  /// Whether this is an extern "C" module.
  LLVM_PREFERRED_TYPE(bool)
  unsigned IsExternC : 1;
 
  /// Whether this is an exhaustive set of configuration macros.
  LLVM_PREFERRED_TYPE(bool)
  unsigned IsExhaustive : 1;
 
  /// Whether files in this module can only include non-modular headers
  /// and headers from used modules.
  LLVM_PREFERRED_TYPE(bool)
  unsigned NoUndeclaredIncludes : 1;
 
  ModuleAttributes()
      : IsSystem(false), IsExternC(false), IsExhaustive(false),
        NoUndeclaredIncludes(false) {}
};
 
/// Reference to a module that consists of either an existing/materialized
/// Module object, reference to a serialized submodule record, both, or
/// neither (null).
class ModuleRef {
  /// The existing/materialized Module object.
  mutable Module *Existing = nullptr;
 
  /// The external submodule source (i.e. \c ASTReader), and a boolean
  /// signifying whether it's already been used to deserialize \c SubmoduleID.
  mutable llvm::PointerIntPair<ExternalSubmoduleSource *, 1, bool>
      ExternalSource = {nullptr, false};
 
  /// Identifier of the external submodule in \c ExternalSource.
  mutable uint64_t SubmoduleID = 0;
 
public:
  /// Create an empty reference.
  ModuleRef() = default;
 
  /// Create reference to a materialized module.
  ModuleRef(Module *M) : Existing(M) {}
 
  /// Create reference to a serialized submodule record.
  ModuleRef(ExternalSubmoduleSource *ExtSrc, uint64_t SubmoduleID)
      : ExternalSource(ExtSrc, false), SubmoduleID(SubmoduleID) {}
 
  /// Get the existing/materialized module, if there's any.
  Module *getExisting() const { return Existing; }
  /// Add the existing/materialized module.
  void setExisting(Module *E) { Existing = E; }
 
  /// Add the serialized submodule record reference.
  void setExternal(ExternalSubmoduleSource *ExtSrc, uint64_t ID) {
    ExternalSource = {ExtSrc, false};
    SubmoduleID = ID;
  }
 
  /// Check whether this is a non-empty reference.
  operator bool() const {
    return Existing || (ExternalSource.getPointer() && SubmoduleID);
  }
 
  /// Get the existing/materialized module. Try materializing it on-demand from
  /// the serialized submodule record if possible.
  operator Module *() const {
    if (!ExternalSource.getInt() && ExternalSource.getPointer() &&
        SubmoduleID) {
      Existing = ExternalSource.getPointer()->getSubmodule(SubmoduleID);
      ExternalSource.setInt(true);
    }
    return Existing;
  }
 
  Module *operator->() const { return *this; }
};
 
/// Required to construct a Module.
///
/// This tag type is only constructible by ModuleMap, guaranteeing it ownership
/// of all Module instances.
class ModuleConstructorTag {
  explicit ModuleConstructorTag() = default;
  friend ModuleMap;
};
 
/// Describes a module or submodule.
///
/// Aligned to 8 bytes to allow for llvm::PointerIntPair<Module *, 3>.
class alignas(8) Module {
public:
  /// The name of this module.
  std::string Name;
 
  /// The location of the module definition.
  SourceLocation DefinitionLoc;
 
  // FIXME: Consider if reducing the size of this enum (having Partition and
  // Named modules only) then representing interface/implementation separately
  // is more efficient.
  enum ModuleKind {
    /// This is a module that was defined by a module map and built out
    /// of header files.
    ModuleMapModule,
 
    /// This is a C++20 header unit.
    ModuleHeaderUnit,
 
    /// This is a C++20 module interface unit.
    ModuleInterfaceUnit,
 
    /// This is a C++20 module implementation unit.
    ModuleImplementationUnit,
 
    /// This is a C++20 module partition interface.
    ModulePartitionInterface,
 
    /// This is a C++20 module partition implementation.
    ModulePartitionImplementation,
 
    /// This is the explicit Global Module Fragment of a modular TU.
    /// As per C++ [module.global.frag].
    ExplicitGlobalModuleFragment,
 
    /// This is the private module fragment within some C++ module.
    PrivateModuleFragment,
 
    /// This is an implicit fragment of the global module which contains
    /// only language linkage declarations (made in the purview of the
    /// named module).
    ImplicitGlobalModuleFragment,
  };
 
  /// The kind of this module.
  ModuleKind Kind = ModuleMapModule;
 
  /// The parent of this module. This will be NULL for the top-level
  /// module.
  Module *Parent;
 
  /// The build directory of this module. This is the directory in
  /// which the module is notionally built, and relative to which its headers
  /// are found.
  OptionalDirectoryEntryRef Directory;
 
  /// The presumed file name for the module map defining this module.
  /// Only non-empty when building from preprocessed source.
  std::string PresumedModuleMapFile;
 
  /// The umbrella header or directory.
  std::variant<std::monostate, FileEntryRef, DirectoryEntryRef> Umbrella;
 
  /// The location of the umbrella header or directory declaration.
  SourceLocation UmbrellaDeclLoc;
 
  /// Directories this module depends on the listing of.
  std::vector<std::string> DirectoryDependencies;
 
  /// The module signature.
  ASTFileSignature Signature;
 
  /// The name of the umbrella entry, as written in the module map.
  std::string UmbrellaAsWritten;
 
  // The path to the umbrella entry relative to the root module's \c Directory.
  std::string UmbrellaRelativeToRootModuleDirectory;
 
  /// The module through which entities defined in this module will
  /// eventually be exposed, for use in "private" modules.
  std::string ExportAsModule;
 
  /// For the debug info, the path to this module's .apinotes file, if any.
  std::string APINotesFile;
 
  /// Does this Module is a named module of a standard named module?
  bool isNamedModule() const {
    switch (Kind) {
    case ModuleInterfaceUnit:
    case ModuleImplementationUnit:
    case ModulePartitionInterface:
    case ModulePartitionImplementation:
    case PrivateModuleFragment:
      return true;
    default:
      return false;
    }
  }
 
  /// Does this Module scope describe a fragment of the global module within
  /// some C++ module.
  bool isGlobalModule() const {
    return isExplicitGlobalModule() || isImplicitGlobalModule();
  }
  bool isExplicitGlobalModule() const {
    return Kind == ExplicitGlobalModuleFragment;
  }
  bool isImplicitGlobalModule() const {
    return Kind == ImplicitGlobalModuleFragment;
  }
 
  bool isPrivateModule() const { return Kind == PrivateModuleFragment; }
 
  bool isModuleMapModule() const { return Kind == ModuleMapModule; }
 
private:
  /// The submodules of this module, indexed by name.
  std::vector<ModuleRef> SubModules;
 
  /// A mapping from the submodule name to the index into the
  /// \c SubModules vector at which that submodule resides.
  llvm::StringMap<unsigned> SubModuleIndex;
 
  /// The AST file name and key if this is a top-level module which has a
  /// corresponding serialized AST file, or null otherwise.
  std::optional<ModuleFileName> ASTFileName;
  std::optional<ModuleFileKey> ASTFileKey;
 
  /// The top-level headers associated with this module.
  llvm::SmallSetVector<FileEntryRef, 2> TopHeaders;
 
  /// top-level header filenames that aren't resolved to FileEntries yet.
  std::vector<std::string> TopHeaderNames;
 
  /// Cache of modules visible to lookup in this module.
  mutable llvm::DenseSet<const Module*> VisibleModulesCache;
 
  /// The ID used when referencing this module within a VisibleModuleSet.
  unsigned VisibilityID;
 
public:
  enum HeaderKind {
    HK_Normal,
    HK_Textual,
    HK_Private,
    HK_PrivateTextual,
    HK_Excluded
  };
  /// Information about a header directive as found in the module map
  /// file.
  struct Header {
    std::string NameAsWritten;
    std::string PathRelativeToRootModuleDirectory;
    FileEntryRef Entry;
  };
 
private:
  static const int NumHeaderKinds = HK_Excluded + 1;
  // The begin index for a HeaderKind also acts the end index of HeaderKind - 1.
  // The extra element at the end acts as the end index of the last HeaderKind.
  unsigned HeaderKindBeginIndex[NumHeaderKinds + 1] = {};
  SmallVector<Header, 2> HeadersStorage;
 
public:
  ArrayRef<Header> getAllHeaders() const { return HeadersStorage; }
  ArrayRef<Header> getHeaders(HeaderKind HK) const {
    assert(HK < NumHeaderKinds && "Invalid Module::HeaderKind");
    auto BeginIt = HeadersStorage.begin() + HeaderKindBeginIndex[HK];
    auto EndIt = HeadersStorage.begin() + HeaderKindBeginIndex[HK + 1];
    return {BeginIt, EndIt};
  }
  void addHeader(HeaderKind HK, Header H) {
    assert(HK < NumHeaderKinds && "Invalid Module::HeaderKind");
    auto EndIt = HeadersStorage.begin() + HeaderKindBeginIndex[HK + 1];
    HeadersStorage.insert(EndIt, std::move(H));
    for (unsigned HKI = HK + 1; HKI != NumHeaderKinds + 1; ++HKI)
      ++HeaderKindBeginIndex[HKI];
  }
 
  /// Information about a directory name as found in the module map file.
  struct DirectoryName {
    std::string NameAsWritten;
    std::string PathRelativeToRootModuleDirectory;
    DirectoryEntryRef Entry;
  };
 
  /// Stored information about a header directive that was found in the
  /// module map file but has not been resolved to a file.
  struct UnresolvedHeaderDirective {
    HeaderKind Kind = HK_Normal;
    SourceLocation FileNameLoc;
    std::string FileName;
    bool IsUmbrella = false;
    bool HasBuiltinHeader = false;
    std::optional<off_t> Size;
    std::optional<time_t> ModTime;
  };
 
  /// Headers that are mentioned in the module map file but that we have not
  /// yet attempted to resolve to a file on the file system.
  SmallVector<UnresolvedHeaderDirective, 1> UnresolvedHeaders;
 
  /// Headers that are mentioned in the module map file but could not be
  /// found on the file system.
  SmallVector<UnresolvedHeaderDirective, 1> MissingHeaders;
 
  struct Requirement {
    std::string FeatureName;
    bool RequiredState;
  };
 
  /// The set of language features required to use this module.
  ///
  /// If any of these requirements are not available, the \c IsAvailable bit
  /// will be false to indicate that this (sub)module is not available.
  SmallVector<Requirement, 2> Requirements;
 
  /// A module with the same name that shadows this module.
  Module *ShadowingModule = nullptr;
 
  /// Whether this module has declared itself unimportable, either because
  /// it's missing a requirement from \p Requirements or because it's been
  /// shadowed by another module.
  LLVM_PREFERRED_TYPE(bool)
  unsigned IsUnimportable : 1;
 
  /// Whether we tried and failed to load a module file for this module.
  LLVM_PREFERRED_TYPE(bool)
  unsigned HasIncompatibleModuleFile : 1;
 
  /// Whether this module is available in the current translation unit.
  ///
  /// If the module is missing headers or does not meet all requirements then
  /// this bit will be 0.
  LLVM_PREFERRED_TYPE(bool)
  unsigned IsAvailable : 1;
 
  /// Whether this module was loaded from a module file.
  LLVM_PREFERRED_TYPE(bool)
  unsigned IsFromModuleFile : 1;
 
  /// Whether this is a framework module.
  LLVM_PREFERRED_TYPE(bool)
  unsigned IsFramework : 1;
 
  /// Whether this is an explicit submodule.
  LLVM_PREFERRED_TYPE(bool)
  unsigned IsExplicit : 1;
 
  /// Whether this is a "system" module (which assumes that all
  /// headers in it are system headers).
  LLVM_PREFERRED_TYPE(bool)
  unsigned IsSystem : 1;
 
  /// Whether this is an 'extern "C"' module (which implicitly puts all
  /// headers in it within an 'extern "C"' block, and allows the module to be
  /// imported within such a block).
  LLVM_PREFERRED_TYPE(bool)
  unsigned IsExternC : 1;
 
  /// Whether this is an inferred submodule (module * { ... }).
  LLVM_PREFERRED_TYPE(bool)
  unsigned IsInferred : 1;
 
  /// Whether we should infer submodules for this module based on
  /// the headers.
  ///
  /// Submodules can only be inferred for modules with an umbrella header.
  LLVM_PREFERRED_TYPE(bool)
  unsigned InferSubmodules : 1;
 
  /// Whether, when inferring submodules, the inferred submodules
  /// should be explicit.
  LLVM_PREFERRED_TYPE(bool)
  unsigned InferExplicitSubmodules : 1;
 
  /// Whether, when inferring submodules, the inferr submodules should
  /// export all modules they import (e.g., the equivalent of "export *").
  LLVM_PREFERRED_TYPE(bool)
  unsigned InferExportWildcard : 1;
 
  /// Whether the set of configuration macros is exhaustive.
  ///
  /// When the set of configuration macros is exhaustive, meaning
  /// that no identifier not in this list should affect how the module is
  /// built.
  LLVM_PREFERRED_TYPE(bool)
  unsigned ConfigMacrosExhaustive : 1;
 
  /// Whether files in this module can only include non-modular headers
  /// and headers from used modules.
  LLVM_PREFERRED_TYPE(bool)
  unsigned NoUndeclaredIncludes : 1;
 
  /// Whether this module came from a "private" module map, found next
  /// to a regular (public) module map.
  LLVM_PREFERRED_TYPE(bool)
  unsigned ModuleMapIsPrivate : 1;
 
  /// Whether this C++20 named modules doesn't need an initializer.
  /// This is only meaningful for C++20 modules.
  LLVM_PREFERRED_TYPE(bool)
  unsigned NamedModuleHasInit : 1;
 
  /// Describes the visibility of the various names within a
  /// particular module.
  enum NameVisibilityKind {
    /// All of the names in this module are hidden.
    Hidden,
    /// All of the names in this module are visible.
    AllVisible
  };
 
  /// The visibility of names within this particular module.
  NameVisibilityKind NameVisibility;
 
  /// The location of the inferred submodule.
  SourceLocation InferredSubmoduleLoc;
 
  /// The set of modules imported by this module, and on which this
  /// module depends.
  llvm::SmallVector<ModuleRef, 2> Imports;
 
  /// The set of top-level modules that affected the compilation of this module,
  /// but were not imported.
  llvm::SmallVector<ModuleRef, 2> AffectingClangModules;
 
  /// Describes an exported module.
  ///
  /// The pointer is the module being re-exported, while the bit will be true
  /// to indicate that this is a wildcard export.
  using ExportDecl = std::pair<ModuleRef, bool>;
 
  /// The set of export declarations.
  SmallVector<ExportDecl, 2> Exports;
 
  /// Describes an exported module that has not yet been resolved
  /// (perhaps because the module it refers to has not yet been loaded).
  struct UnresolvedExportDecl {
    /// The location of the 'export' keyword in the module map file.
    SourceLocation ExportLoc;
 
    /// The name of the module.
    ModuleId Id;
 
    /// Whether this export declaration ends in a wildcard, indicating
    /// that all of its submodules should be exported (rather than the named
    /// module itself).
    bool Wildcard;
  };
 
  /// The set of export declarations that have yet to be resolved.
  SmallVector<UnresolvedExportDecl, 2> UnresolvedExports;
 
  /// The directly used modules.
  SmallVector<Module *, 2> DirectUses;
 
  /// The set of use declarations that have yet to be resolved.
  SmallVector<ModuleId, 2> UnresolvedDirectUses;
 
  /// When \c NoUndeclaredIncludes is true, the set of modules this module tried
  /// to import but didn't because they are not direct uses.
  llvm::SmallSetVector<const Module *, 2> UndeclaredUses;
 
  /// A library or framework to link against when an entity from this
  /// module is used.
  struct LinkLibrary {
    LinkLibrary() = default;
    LinkLibrary(const std::string &Library, bool IsFramework)
        : Library(Library), IsFramework(IsFramework) {}
 
    /// The library to link against.
    ///
    /// This will typically be a library or framework name, but can also
    /// be an absolute path to the library or framework.
    std::string Library;
 
    /// Whether this is a framework rather than a library.
    bool IsFramework = false;
  };
 
  /// The set of libraries or frameworks to link against when
  /// an entity from this module is used.
  llvm::SmallVector<LinkLibrary, 2> LinkLibraries;
 
  /// Autolinking uses the framework name for linking purposes
  /// when this is false and the export_as name otherwise.
  bool UseExportAsModuleLinkName = false;
 
  /// The set of "configuration macros", which are macros that
  /// (intentionally) change how this module is built.
  std::vector<std::string> ConfigMacros;
 
  /// An unresolved conflict with another module.
  struct UnresolvedConflict {
    /// The (unresolved) module id.
    ModuleId Id;
 
    /// The message provided to the user when there is a conflict.
    std::string Message;
  };
 
  /// The list of conflicts for which the module-id has not yet been
  /// resolved.
  std::vector<UnresolvedConflict> UnresolvedConflicts;
 
  /// A conflict between two modules.
  struct Conflict {
    /// The module that this module conflicts with.
    ModuleRef Other;
 
    /// The message provided to the user when there is a conflict.
    std::string Message;
  };
 
  /// The list of conflicts.
  std::vector<Conflict> Conflicts;
 
  /// Construct a new module or submodule.
  Module(ModuleConstructorTag, StringRef Name, SourceLocation DefinitionLoc,
         Module *Parent, bool IsFramework, bool IsExplicit,
         unsigned VisibilityID);
 
  ~Module();
 
  /// Determine whether this module has been declared unimportable.
  bool isUnimportable() const { return IsUnimportable; }
 
  /// Determine whether this module has been declared unimportable.
  ///
  /// \param LangOpts The language options used for the current
  /// translation unit.
  ///
  /// \param Target The target options used for the current translation unit.
  ///
  /// \param Req If this module is unimportable because of a missing
  /// requirement, this parameter will be set to one of the requirements that
  /// is not met for use of this module.
  ///
  /// \param ShadowingModule If this module is unimportable because it is
  /// shadowed, this parameter will be set to the shadowing module.
  bool isUnimportable(const LangOptions &LangOpts, const TargetInfo &Target,
                      Requirement &Req, Module *&ShadowingModule) const;
 
  /// Determine whether this module can be built in this compilation.
  bool isForBuilding(const LangOptions &LangOpts) const;
 
  /// Determine whether this module is available for use within the
  /// current translation unit.
  bool isAvailable() const { return IsAvailable; }
 
  /// Determine whether this module is available for use within the
  /// current translation unit.
  ///
  /// \param LangOpts The language options used for the current
  /// translation unit.
  ///
  /// \param Target The target options used for the current translation unit.
  ///
  /// \param Req If this module is unavailable because of a missing requirement,
  /// this parameter will be set to one of the requirements that is not met for
  /// use of this module.
  ///
  /// \param MissingHeader If this module is unavailable because of a missing
  /// header, this parameter will be set to one of the missing headers.
  ///
  /// \param ShadowingModule If this module is unavailable because it is
  /// shadowed, this parameter will be set to the shadowing module.
  bool isAvailable(const LangOptions &LangOpts,
                   const TargetInfo &Target,
                   Requirement &Req,
                   UnresolvedHeaderDirective &MissingHeader,
                   Module *&ShadowingModule) const;
 
  /// Determine whether this module is a submodule.
  bool isSubModule() const { return Parent != nullptr; }
 
  /// Check if this module is a (possibly transitive) submodule of \p Other.
  ///
  /// The 'A is a submodule of B' relation is a partial order based on the
  /// the parent-child relationship between individual modules.
  ///
  /// Returns \c false if \p Other is \c nullptr.
  bool isSubModuleOf(const Module *Other) const;
 
  /// Determine whether this module is a part of a framework,
  /// either because it is a framework module or because it is a submodule
  /// of a framework module.
  bool isPartOfFramework() const {
    for (const Module *Mod = this; Mod; Mod = Mod->Parent)
      if (Mod->IsFramework)
        return true;
 
    return false;
  }
 
  /// Determine whether this module is a subframework of another
  /// framework.
  bool isSubFramework() const {
    return IsFramework && Parent && Parent->isPartOfFramework();
  }
 
  /// Set the parent of this module. This should only be used if the parent
  /// could not be set during module creation.
  void setParent(Module *M) {
    assert(!Parent);
    Parent = M;
    Parent->SubModuleIndex[M->Name] = Parent->SubModules.size();
    Parent->SubModules.push_back(this);
  }
 
  /// Add a child submodule.
  void addSubmodule(StringRef Name, Module *Submodule) {
    auto [It, New] = SubModuleIndex.insert({Name, SubModules.size()});
    if (New)
      SubModules.emplace_back();
    SubModules[It->second].setExisting(Submodule);
  }
 
  /// Add the external part of a submodule ModuleRef.
  void addSubmodule(StringRef Name, ExternalSubmoduleSource *ExternalSource,
                    uint64_t SubmoduleID) {
    auto [It, New] = SubModuleIndex.insert({Name, SubModules.size()});
    if (New)
      SubModules.emplace_back();
    SubModules[It->second].setExternal(ExternalSource, SubmoduleID);
  }
 
  /// Is this module have similar semantics as headers.
  bool isHeaderLikeModule() const {
    return isModuleMapModule() || isHeaderUnit();
  }
 
  /// Is this a module partition.
  bool isModulePartition() const {
    return Kind == ModulePartitionInterface ||
           Kind == ModulePartitionImplementation;
  }
 
  /// Is this a module partition implementation unit.
  bool isModulePartitionImplementation() const {
    return Kind == ModulePartitionImplementation;
  }
 
  /// Is this a module implementation.
  bool isModuleImplementation() const {
    return Kind == ModuleImplementationUnit;
  }
 
  /// Is this module a header unit.
  bool isHeaderUnit() const { return Kind == ModuleHeaderUnit; }
  // Is this a C++20 module interface or a partition.
  bool isInterfaceOrPartition() const {
    return Kind == ModuleInterfaceUnit || isModulePartition();
  }
 
  /// Is this a C++20 named module unit.
  bool isNamedModuleUnit() const {
    return isInterfaceOrPartition() || isModuleImplementation();
  }
 
  bool isModuleInterfaceUnit() const {
    return Kind == ModuleInterfaceUnit || Kind == ModulePartitionInterface;
  }
 
  bool isNamedModuleInterfaceHasInit() const { return NamedModuleHasInit; }
 
  /// Get the primary module interface name from a partition.
  StringRef getPrimaryModuleInterfaceName() const {
    // Technically, global module fragment belongs to global module. And global
    // module has no name: [module.unit]p6:
    //   The global module has no name, no module interface unit, and is not
    //   introduced by any module-declaration.
    //
    // <global> is the default name showed in module map.
    if (isGlobalModule())
      return "<global>";
 
    if (isModulePartition()) {
      auto pos = Name.find(':');
      return StringRef(Name.data(), pos);
    }
 
    if (isPrivateModule())
      return getTopLevelModuleName();
 
    return Name;
  }
 
  /// Retrieve the full name of this module, including the path from
  /// its top-level module.
  /// \param AllowStringLiterals If \c true, components that might not be
  ///        lexically valid as identifiers will be emitted as string literals.
  std::string getFullModuleName(bool AllowStringLiterals = false) const;
 
  /// Whether the full name of this module is equal to joining
  /// \p nameParts with "."s.
  ///
  /// This is more efficient than getFullModuleName().
  bool fullModuleNameIs(ArrayRef<StringRef> nameParts) const;
 
  /// Retrieve the top-level module for this (sub)module, which may
  /// be this module.
  Module *getTopLevelModule() {
    return const_cast<Module *>(
             const_cast<const Module *>(this)->getTopLevelModule());
  }
 
  /// Retrieve the top-level module for this (sub)module, which may
  /// be this module.
  const Module *getTopLevelModule() const;
 
  /// Retrieve the name of the top-level module.
  StringRef getTopLevelModuleName() const {
    return getTopLevelModule()->Name;
  }
 
  /// The serialized AST file name for this module, if one was created.
  const ModuleFileName *getASTFileName() const {
    const Module *TopLevel = getTopLevelModule();
    return TopLevel->ASTFileName ? &*TopLevel->ASTFileName : nullptr;
  }
 
  /// The serialized AST file key for this module, if one was created.
  const ModuleFileKey *getASTFileKey() const {
    const Module *TopLevel = getTopLevelModule();
    return TopLevel->ASTFileKey ? &*TopLevel->ASTFileKey : nullptr;
  }
 
  /// Set the serialized module file for the top-level module of this module.
  void setASTFileNameAndKey(ModuleFileName NewName, ModuleFileKey NewKey) {
    assert(((!getASTFileName() && !getASTFileKey()) ||
            *getASTFileKey() == NewKey) &&
           "file path changed");
    Module *TopLevel = getTopLevelModule();
    TopLevel->ASTFileName = NewName;
    TopLevel->ASTFileKey = NewKey;
  }
 
  /// Retrieve the umbrella directory as written.
  std::optional<DirectoryName> getUmbrellaDirAsWritten() const {
    if (const auto *Dir = std::get_if<DirectoryEntryRef>(&Umbrella))
      return DirectoryName{UmbrellaAsWritten,
                           UmbrellaRelativeToRootModuleDirectory, *Dir};
    return std::nullopt;
  }
 
  /// Retrieve the umbrella header as written.
  std::optional<Header> getUmbrellaHeaderAsWritten() const {
    if (const auto *Hdr = std::get_if<FileEntryRef>(&Umbrella))
      return Header{UmbrellaAsWritten, UmbrellaRelativeToRootModuleDirectory,
                    *Hdr};
    return std::nullopt;
  }
 
  /// Get the effective umbrella directory for this module: either the one
  /// explicitly written in the module map file, or the parent of the umbrella
  /// header.
  OptionalDirectoryEntryRef getEffectiveUmbrellaDir() const;
 
  /// Record that this module depends on the listing of \p Path, which must name
  /// a location in an underlying file system, not in a VFS overlay. Callers
  /// normally want \c ModuleMap::recordDirectoryDependencies.
  void addDirectoryDependency(StringRef Path);
 
  ArrayRef<std::string> getDirectoryDependencies() const {
    return DirectoryDependencies;
  }
 
  /// Add a top-level header associated with this module.
  void addTopHeader(FileEntryRef File);
 
  /// Add a top-level header filename associated with this module.
  void addTopHeaderFilename(StringRef Filename) {
    TopHeaderNames.push_back(std::string(Filename));
  }
 
  /// The top-level headers associated with this module.
  ArrayRef<FileEntryRef> getTopHeaders(FileManager &FileMgr);
 
  /// Determine whether this module has declared its intention to
  /// directly use another module.
  bool directlyUses(const Module *Requested);
 
  /// Add the given feature requirement to the list of features
  /// required by this module.
  ///
  /// \param Feature The feature that is required by this module (and
  /// its submodules).
  ///
  /// \param RequiredState The required state of this feature: \c true
  /// if it must be present, \c false if it must be absent.
  ///
  /// \param LangOpts The set of language options that will be used to
  /// evaluate the availability of this feature.
  ///
  /// \param Target The target options that will be used to evaluate the
  /// availability of this feature.
  void addRequirement(StringRef Feature, bool RequiredState,
                      const LangOptions &LangOpts,
                      const TargetInfo &Target);
 
  /// Mark this module and all of its submodules as unavailable.
  void markUnavailable(bool Unimportable);
 
  /// Find the submodule with the given name.
  ///
  /// \returns The submodule if found, or NULL otherwise.
  ModuleRef findSubmodule(StringRef Name) const;
 
  /// Get the Global Module Fragment (sub-module) for this module, it there is
  /// one.
  ///
  /// \returns The GMF sub-module if found, or NULL otherwise.
  Module *getGlobalModuleFragment() const;
 
  /// Get the Private Module Fragment (sub-module) for this module, it there is
  /// one.
  ///
  /// \returns The PMF sub-module if found, or NULL otherwise.
  Module *getPrivateModuleFragment() const;
 
  /// Determine whether the specified module would be visible to
  /// a lookup at the end of this module.
  ///
  /// FIXME: This may return incorrect results for (submodules of) the
  /// module currently being built, if it's queried before we see all
  /// of its imports.
  bool isModuleVisible(const Module *M) const {
    if (VisibleModulesCache.empty())
      buildVisibleModulesCache();
    return VisibleModulesCache.count(M);
  }
 
  unsigned getVisibilityID() const { return VisibilityID; }
 
  using submodule_iterator = std::vector<ModuleRef>::iterator;
  using submodule_const_iterator = std::vector<ModuleRef>::const_iterator;
 
  llvm::iterator_range<submodule_iterator> submodules() {
    return llvm::make_range(SubModules.begin(), SubModules.end());
  }
  llvm::iterator_range<submodule_const_iterator> submodules() const {
    return llvm::make_range(SubModules.begin(), SubModules.end());
  }
 
  /// Appends this module's list of exported modules to \p Exported.
  ///
  /// This provides a subset of immediately imported modules (the ones that are
  /// directly exported), not the complete set of exported modules.
  void getExportedModules(SmallVectorImpl<Module *> &Exported) const;
 
  static StringRef getModuleInputBufferName() {
    return "<module-includes>";
  }
 
  /// Print the module map for this module to the given stream.
  void print(raw_ostream &OS, unsigned Indent = 0, bool Dump = false) const;
 
  /// Dump the contents of this module to the given output stream.
  void dump() const;
 
private:
  void buildVisibleModulesCache() const;
};
 
/// A set of visible modules.
class VisibleModuleSet {
public:
  VisibleModuleSet() = default;
  VisibleModuleSet(VisibleModuleSet &&O)
      : ImportLocs(std::move(O.ImportLocs)), Generation(O.Generation ? 1 : 0) {
    O.ImportLocs.clear();
    ++O.Generation;
  }
 
  /// Move from another visible modules set. Guaranteed to leave the source
  /// empty and bump the generation on both.
  VisibleModuleSet &operator=(VisibleModuleSet &&O) {
    ImportLocs = std::move(O.ImportLocs);
    O.ImportLocs.clear();
    ++O.Generation;
    ++Generation;
    return *this;
  }
 
  /// Get the current visibility generation. Incremented each time the
  /// set of visible modules changes in any way.
  unsigned getGeneration() const { return Generation; }
 
  /// Determine whether a module is visible.
  bool isVisible(const Module *M) const {
    return getImportLoc(M).isValid();
  }
 
  /// Get the location at which the import of a module was triggered.
  SourceLocation getImportLoc(const Module *M) const {
    return M && M->getVisibilityID() < ImportLocs.size()
               ? ImportLocs[M->getVisibilityID()]
               : SourceLocation();
  }
 
  /// A callback to call when a module is made visible (directly or
  /// indirectly) by a call to \ref setVisible.
  using VisibleCallback = llvm::function_ref<void(Module *M)>;
 
  /// A callback to call when a module conflict is found. \p Path
  /// consists of a sequence of modules from the conflicting module to the one
  /// made visible, where each was exported by the next.
  using ConflictCallback =
      llvm::function_ref<void(ArrayRef<Module *> Path, Module *Conflict,
                         StringRef Message)>;
 
  /// Make a specific module visible.
  void setVisible(
      Module *M, SourceLocation Loc, bool IncludeExports = true,
      VisibleCallback Vis = [](Module *) {},
      ConflictCallback Cb = [](ArrayRef<Module *>, Module *, StringRef) {});
 
private:
  /// Import locations for each visible module. Indexed by the module's
  /// VisibilityID.
  std::vector<SourceLocation> ImportLocs;
 
  /// Visibility generation, bumped every time the visibility state changes.
  unsigned Generation = 0;
};
 
} // namespace clang
 
template <> struct llvm::DenseMapInfo<clang::ModuleFileKey> {
  static unsigned getHashValue(const clang::ModuleFileKey &Val) {
    return hash_combine(Val.Ptr, Val.ImplicitModulePathSuffix);
  }
 
  static bool isEqual(const clang::ModuleFileKey &LHS,
                      const clang::ModuleFileKey &RHS) {
    return LHS == RHS;
  }
};
 
#endif // LLVM_CLANG_BASIC_MODULE_H