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//===- ModuleMap.h - Describe the layout of modules -------------*- 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

//

//===----------------------------------------------------------------------===//

//

// This file defines the ModuleMap interface, which describes the layout of a

// module as it relates to headers.

//

//===----------------------------------------------------------------------===//

#ifndef LLVM_CLANG_LEX_MODULEMAP_H

#define LLVM_CLANG_LEX_MODULEMAP_H

#include "clang/Basic/IdentifierTable.h"

#include "clang/Basic/LangOptions.h"

#include "clang/Basic/Module.h"

#include "clang/Basic/SourceLocation.h"

#include "llvm/ADT/ArrayRef.h"

#include "llvm/ADT/DenseMap.h"

#include "llvm/ADT/PointerIntPair.h"

#include "llvm/ADT/SmallPtrSet.h"

#include "llvm/ADT/SmallVector.h"

#include "llvm/ADT/StringMap.h"

#include "llvm/ADT/StringRef.h"

#include "llvm/ADT/StringSet.h"

#include "llvm/ADT/TinyPtrVector.h"

#include "llvm/ADT/Twine.h"

#include <ctime>

#include <memory>

#include <optional>

#include <string>

#include <utility>

namespace clang {

class DiagnosticsEngine;

class DirectoryEntry;

class FileEntry;

class FileManager;

class HeaderSearch;

class SourceManager;

/// A mechanism to observe the actions of the module map parser as it

/// reads module map files.

class ModuleMapCallbacks {

  virtual void anchor();

public:

  virtual ~ModuleMapCallbacks() = default;

  /// Called when a module map file has been read.

  ///

  /// \param FileStart A SourceLocation referring to the start of the file's

  /// contents.

  /// \param File The file itself.

  /// \param IsSystem Whether this is a module map from a system include path.

  virtual void moduleMapFileRead(SourceLocation FileStart,

                                 const FileEntry &File, bool IsSystem) {}

  /// Called when a header is added during module map parsing.

  ///

  /// \param Filename The header file itself.

  virtual void moduleMapAddHeader(StringRef Filename) {}

  /// Called when an umbrella header is added during module map parsing.

  ///

  /// \param FileMgr FileManager instance

  /// \param Header The umbrella header to collect.

  virtual void moduleMapAddUmbrellaHeader(FileManager *FileMgr,

                                          const FileEntry *Header) {}

};

class ModuleMap {

  SourceManager &SourceMgr;

  DiagnosticsEngine &Diags;

  const LangOptions &LangOpts;

  const TargetInfo *Target;

  HeaderSearch &HeaderInfo;

  llvm::SmallVector<std::unique_ptr<ModuleMapCallbacks>, 1> Callbacks;

  /// The directory used for Clang-supplied, builtin include headers,

  /// such as "stdint.h".

  const DirectoryEntry *BuiltinIncludeDir = nullptr;

  /// Language options used to parse the module map itself.

  ///

  /// These are always simple C language options.

  LangOptions MMapLangOpts;

  /// The module that the main source file is associated with (the module

  /// named LangOpts::CurrentModule, if we've loaded it).

  Module *SourceModule = nullptr;

  /// Submodules of the current module that have not yet been attached to it.

  /// (Ownership is transferred if/when we create an enclosing module.)

  llvm::SmallVector<std::unique_ptr<Module>, 8> PendingSubmodules;

  /// The top-level modules that are known.

  llvm::StringMap<Module *> Modules;

  /// Module loading cache that includes submodules, indexed by IdentifierInfo.

  /// nullptr is stored for modules that are known to fail to load.

  llvm::DenseMap<const IdentifierInfo *, Module *> CachedModuleLoads;

  /// Shadow modules created while building this module map.

  llvm::SmallVector<Module*, 2> ShadowModules;

  /// The number of modules we have created in total.

  unsigned NumCreatedModules = 0;

  /// In case a module has a export_as entry, it might have a pending link

  /// name to be determined if that module is imported.

  llvm::StringMap<llvm::StringSet<>> PendingLinkAsModule;

public:

  /// Use PendingLinkAsModule information to mark top level link names that

  /// are going to be replaced by export_as aliases.

  void resolveLinkAsDependencies(Module *Mod);

  /// Make module to use export_as as the link dependency name if enough

  /// information is available or add it to a pending list otherwise.

  void addLinkAsDependency(Module *Mod);

  /// Flags describing the role of a module header.

  enum ModuleHeaderRole {

    /// This header is normally included in the module.

    NormalHeader  = 0x0,

    /// This header is included but private.

    PrivateHeader = 0x1,

    /// This header is part of the module (for layering purposes) but

    /// should be textually included.

    TextualHeader = 0x2,

    /// This header is explicitly excluded from the module.

    ExcludedHeader = 0x4,

    // Caution: Adding an enumerator needs other changes.

    // Adjust the number of bits for KnownHeader::Storage.

    // Adjust the HeaderFileInfoTrait::ReadData streaming.

    // Adjust the HeaderFileInfoTrait::EmitData streaming.

    // Adjust ModuleMap::addHeader.

  };

  /// Convert a header kind to a role. Requires Kind to not be HK_Excluded.

  static ModuleHeaderRole headerKindToRole(Module::HeaderKind Kind);

  /// Convert a header role to a kind.

  static Module::HeaderKind headerRoleToKind(ModuleHeaderRole Role);

  /// Check if the header with the given role is a modular one.

  static bool isModular(ModuleHeaderRole Role);

  /// A header that is known to reside within a given module,

  /// whether it was included or excluded.

  class KnownHeader {

    llvm::PointerIntPair<Module *, 3, ModuleHeaderRole> Storage;

  public:

    KnownHeader() : Storage(nullptr, NormalHeader) {}

    KnownHeader(Module *M, ModuleHeaderRole Role) : Storage(M, Role) {}

    friend bool operator==(const KnownHeader &A, const KnownHeader &B) {

      return A.Storage == B.Storage;

    }

    friend bool operator!=(const KnownHeader &A, const KnownHeader &B) {

      return A.Storage != B.Storage;

    }

    /// Retrieve the module the header is stored in.

    Module *getModule() const { return Storage.getPointer(); }

    /// The role of this header within the module.

    ModuleHeaderRole getRole() const { return Storage.getInt(); }

    /// Whether this header is available in the module.

    bool isAvailable() const {

      return getRole() != ExcludedHeader && getModule()->isAvailable();

    }

    /// Whether this header is accessible from the specified module.

    bool isAccessibleFrom(Module *M) const {

      return !(getRole() & PrivateHeader) ||

             (M && M->getTopLevelModule() == getModule()->getTopLevelModule());

    }

    // Whether this known header is valid (i.e., it has an

    // associated module).

    explicit operator bool() const {

      return Storage.getPointer() != nullptr;

    }

  };

  using AdditionalModMapsSet = llvm::SmallPtrSet<const FileEntry *, 1>;

private:

  friend class ModuleMapParser;

  using HeadersMap =

      llvm::DenseMap<const FileEntry *, SmallVector<KnownHeader, 1>>;

  /// Mapping from each header to the module that owns the contents of

  /// that header.

  HeadersMap Headers;

  /// Map from file sizes to modules with lazy header directives of that size.

  mutable llvm::DenseMap<off_t, llvm::TinyPtrVector<Module*>> LazyHeadersBySize;

  /// Map from mtimes to modules with lazy header directives with those mtimes.

  mutable llvm::DenseMap<time_t, llvm::TinyPtrVector<Module*>>

              LazyHeadersByModTime;

  /// Mapping from directories with umbrella headers to the module

  /// that is generated from the umbrella header.

  ///

  /// This mapping is used to map headers that haven't explicitly been named

  /// in the module map over to the module that includes them via its umbrella

  /// header.

  llvm::DenseMap<const DirectoryEntry *, Module *> UmbrellaDirs;

  /// A generation counter that is used to test whether modules of the

  /// same name may shadow or are illegal redefinitions.

  ///

  /// Modules from earlier scopes may shadow modules from later ones.

  /// Modules from the same scope may not have the same name.

  unsigned CurrentModuleScopeID = 0;

  llvm::DenseMap<Module *, unsigned> ModuleScopeIDs;

  /// The set of attributes that can be attached to a module.

  struct Attributes {

    /// Whether this is a system module.

    unsigned IsSystem : 1;

    /// Whether this is an extern "C" module.

    unsigned IsExternC : 1;

    /// Whether this is an exhaustive set of configuration macros.

    unsigned IsExhaustive : 1;

    /// Whether files in this module can only include non-modular headers

    /// and headers from used modules.

    unsigned NoUndeclaredIncludes : 1;

    Attributes()

        : IsSystem(false), IsExternC(false), IsExhaustive(false),

          NoUndeclaredIncludes(false) {}

  };

  /// A directory for which framework modules can be inferred.

  struct InferredDirectory {

    /// Whether to infer modules from this directory.

    unsigned InferModules : 1;

    /// The attributes to use for inferred modules.

    Attributes Attrs;

    /// If \c InferModules is non-zero, the module map file that allowed

    /// inferred modules.  Otherwise, nullptr.

    const FileEntry *ModuleMapFile;

    /// The names of modules that cannot be inferred within this

    /// directory.

    SmallVector<std::string, 2> ExcludedModules;

    InferredDirectory() : InferModules(false) {}

  };

  /// A mapping from directories to information about inferring

  /// framework modules from within those directories.

  llvm::DenseMap<const DirectoryEntry *, InferredDirectory> InferredDirectories;

  /// A mapping from an inferred module to the module map that allowed the

  /// inference.

  llvm::DenseMap<const Module *, const FileEntry *> InferredModuleAllowedBy;

  llvm::DenseMap<const Module *, AdditionalModMapsSet> AdditionalModMaps;

  /// Describes whether we haved parsed a particular file as a module

  /// map.

  llvm::DenseMap<const FileEntry *, bool> ParsedModuleMap;

  /// Resolve the given export declaration into an actual export

  /// declaration.

  ///

  /// \param Mod The module in which we're resolving the export declaration.

  ///

  /// \param Unresolved The export declaration to resolve.

  ///

  /// \param Complain Whether this routine should complain about unresolvable

  /// exports.

  ///

  /// \returns The resolved export declaration, which will have a NULL pointer

  /// if the export could not be resolved.

  Module::ExportDecl

  resolveExport(Module *Mod, const Module::UnresolvedExportDecl &Unresolved,

                bool Complain) const;

  /// Resolve the given module id to an actual module.

  ///

  /// \param Id The module-id to resolve.

  ///

  /// \param Mod The module in which we're resolving the module-id.

  ///

  /// \param Complain Whether this routine should complain about unresolvable

  /// module-ids.

  ///

  /// \returns The resolved module, or null if the module-id could not be

  /// resolved.

  Module *resolveModuleId(const ModuleId &Id, Module *Mod, bool Complain) const;

  /// Add an unresolved header to a module.

  ///

  /// \param Mod The module in which we're adding the unresolved header

  ///        directive.

  /// \param Header The unresolved header directive.

  /// \param NeedsFramework If Mod is not a framework but a missing header would

  ///        be found in case Mod was, set it to true. False otherwise.

  void addUnresolvedHeader(Module *Mod,

                           Module::UnresolvedHeaderDirective Header,

                           bool &NeedsFramework);

  /// Look up the given header directive to find an actual header file.

  ///

  /// \param M The module in which we're resolving the header directive.

  /// \param Header The header directive to resolve.

  /// \param RelativePathName Filled in with the relative path name from the

  ///        module to the resolved header.

  /// \param NeedsFramework If M is not a framework but a missing header would

  ///        be found in case M was, set it to true. False otherwise.

  /// \return The resolved file, if any.

  OptionalFileEntryRef

  findHeader(Module *M, const Module::UnresolvedHeaderDirective &Header,

             SmallVectorImpl<char> &RelativePathName, bool &NeedsFramework);

  /// Resolve the given header directive.

  ///

  /// \param M The module in which we're resolving the header directive.

  /// \param Header The header directive to resolve.

  /// \param NeedsFramework If M is not a framework but a missing header would

  ///        be found in case M was, set it to true. False otherwise.

  void resolveHeader(Module *M, const Module::UnresolvedHeaderDirective &Header,

                     bool &NeedsFramework);

  /// Attempt to resolve the specified header directive as naming a builtin

  /// header.

  /// \return \c true if a corresponding builtin header was found.

  bool resolveAsBuiltinHeader(Module *M,

                              const Module::UnresolvedHeaderDirective &Header);

  /// Looks up the modules that \p File corresponds to.

  ///

  /// If \p File represents a builtin header within Clang's builtin include

  /// directory, this also loads all of the module maps to see if it will get

  /// associated with a specific module (e.g. in /usr/include).

  HeadersMap::iterator findKnownHeader(const FileEntry *File);

  /// Searches for a module whose umbrella directory contains \p File.

  ///

  /// \param File The header to search for.

  ///

  /// \param IntermediateDirs On success, contains the set of directories

  /// searched before finding \p File.

  KnownHeader findHeaderInUmbrellaDirs(const FileEntry *File,

                    SmallVectorImpl<const DirectoryEntry *> &IntermediateDirs);

  /// Given that \p File is not in the Headers map, look it up within

  /// umbrella directories and find or create a module for it.

  KnownHeader findOrCreateModuleForHeaderInUmbrellaDir(const FileEntry *File);

  /// A convenience method to determine if \p File is (possibly nested)

  /// in an umbrella directory.

  bool isHeaderInUmbrellaDirs(const FileEntry *File) {

    SmallVector<const DirectoryEntry *, 2> IntermediateDirs;

    return static_cast<bool>(findHeaderInUmbrellaDirs(File, IntermediateDirs));

  }

  Module *inferFrameworkModule(const DirectoryEntry *FrameworkDir,

                               Attributes Attrs, Module *Parent);

public:

  /// Construct a new module map.

  ///

  /// \param SourceMgr The source manager used to find module files and headers.

  /// This source manager should be shared with the header-search mechanism,

  /// since they will refer to the same headers.

  ///

  /// \param Diags A diagnostic engine used for diagnostics.

  ///

  /// \param LangOpts Language options for this translation unit.

  ///

  /// \param Target The target for this translation unit.

  ModuleMap(SourceManager &SourceMgr, DiagnosticsEngine &Diags,

            const LangOptions &LangOpts, const TargetInfo *Target,

            HeaderSearch &HeaderInfo);

  /// Destroy the module map.

  ~ModuleMap();

  /// Set the target information.

  void setTarget(const TargetInfo &Target);

  /// Set the directory that contains Clang-supplied include

  /// files, such as our stdarg.h or tgmath.h.

  void setBuiltinIncludeDir(const DirectoryEntry *Dir) {

    BuiltinIncludeDir = Dir;

  }

  /// Get the directory that contains Clang-supplied include files.

  const DirectoryEntry *getBuiltinDir() const {

    return BuiltinIncludeDir;

  }

  /// Is this a compiler builtin header?

  static bool isBuiltinHeader(StringRef FileName);

  bool isBuiltinHeader(const FileEntry *File);

  /// Add a module map callback.

  void addModuleMapCallbacks(std::unique_ptr<ModuleMapCallbacks> Callback) {

    Callbacks.push_back(std::move(Callback));

  }

  /// Retrieve the module that owns the given header file, if any. Note that

  /// this does not implicitly load module maps, except for builtin headers,

  /// and does not consult the external source. (Those checks are the

  /// responsibility of \ref HeaderSearch.)

  ///

  /// \param File The header file that is likely to be included.

  ///

  /// \param AllowTextual If \c true and \p File is a textual header, return

  /// its owning module. Otherwise, no KnownHeader will be returned if the

  /// file is only known as a textual header.

  ///

  /// \returns The module KnownHeader, which provides the module that owns the

  /// given header file.  The KnownHeader is default constructed to indicate

  /// that no module owns this header file.

  KnownHeader findModuleForHeader(const FileEntry *File,

                                  bool AllowTextual = false,

                                  bool AllowExcluded = false);

  /// Retrieve all the modules that contain the given header file. Note that

  /// this does not implicitly load module maps, except for builtin headers,

  /// and does not consult the external source. (Those checks are the

  /// responsibility of \ref HeaderSearch.)

  ///

  /// Typically, \ref findModuleForHeader should be used instead, as it picks

  /// the preferred module for the header.

  ArrayRef<KnownHeader> findAllModulesForHeader(const FileEntry *File);

  /// Like \ref findAllModulesForHeader, but do not attempt to infer module

  /// ownership from umbrella headers if we've not already done so.

  ArrayRef<KnownHeader>

  findResolvedModulesForHeader(const FileEntry *File) const;

  /// Resolve all lazy header directives for the specified file.

  ///

  /// This ensures that the HeaderFileInfo on HeaderSearch is up to date. This

  /// is effectively internal, but is exposed so HeaderSearch can call it.

  void resolveHeaderDirectives(const FileEntry *File) const;

  /// Resolve lazy header directives for the specified module. If File is

  /// provided, only headers with same size and modtime are resolved. If File

  /// is not set, all headers are resolved.

  void resolveHeaderDirectives(Module *Mod,

                               std::optional<const FileEntry *> File) const;

  /// Reports errors if a module must not include a specific file.

  ///

  /// \param RequestingModule The module including a file.

  ///

  /// \param RequestingModuleIsModuleInterface \c true if the inclusion is in

  ///        the interface of RequestingModule, \c false if it's in the

  ///        implementation of RequestingModule. Value is ignored and

  ///        meaningless if RequestingModule is nullptr.

  ///

  /// \param FilenameLoc The location of the inclusion's filename.

  ///

  /// \param Filename The included filename as written.

  ///

  /// \param File The included file.

  void diagnoseHeaderInclusion(Module *RequestingModule,

                               bool RequestingModuleIsModuleInterface,

                               SourceLocation FilenameLoc, StringRef Filename,

                               FileEntryRef File);

  /// Determine whether the given header is part of a module

  /// marked 'unavailable'.

  bool isHeaderInUnavailableModule(const FileEntry *Header) const;

  /// Determine whether the given header is unavailable as part

  /// of the specified module.

  bool isHeaderUnavailableInModule(const FileEntry *Header,

                                   const Module *RequestingModule) const;

  /// Retrieve a module with the given name.

  ///

  /// \param Name The name of the module to look up.

  ///

  /// \returns The named module, if known; otherwise, returns null.

  Module *findModule(StringRef Name) const;

  /// Retrieve a module with the given name using lexical name lookup,

  /// starting at the given context.

  ///

  /// \param Name The name of the module to look up.

  ///

  /// \param Context The module context, from which we will perform lexical

  /// name lookup.

  ///

  /// \returns The named module, if known; otherwise, returns null.

  Module *lookupModuleUnqualified(StringRef Name, Module *Context) const;

  /// Retrieve a module with the given name within the given context,

  /// using direct (qualified) name lookup.

  ///

  /// \param Name The name of the module to look up.

  ///

  /// \param Context The module for which we will look for a submodule. If

  /// null, we will look for a top-level module.

  ///

  /// \returns The named submodule, if known; otherwose, returns null.

  Module *lookupModuleQualified(StringRef Name, Module *Context) const;

  /// Find a new module or submodule, or create it if it does not already

  /// exist.

  ///

  /// \param Name The name of the module to find or create.

  ///

  /// \param Parent The module that will act as the parent of this submodule,

  /// or nullptr to indicate that this is a top-level module.

  ///

  /// \param IsFramework Whether this is a framework module.

  ///

  /// \param IsExplicit Whether this is an explicit submodule.

  ///

  /// \returns The found or newly-created module, along with a boolean value

  /// that will be true if the module is newly-created.

  std::pair<Module *, bool> findOrCreateModule(StringRef Name, Module *Parent,

                                               bool IsFramework,

                                               bool IsExplicit);

  /// Create a global module fragment for a C++ module unit.

  ///

  /// We model the global module fragment as a submodule of the module

  /// interface unit. Unfortunately, we can't create the module interface

  /// unit's Module until later, because we don't know what it will be called

  /// usually. See C++20 [module.unit]/7.2 for the case we could know its

  /// parent.

  Module *createGlobalModuleFragmentForModuleUnit(SourceLocation Loc,

                                                  Module *Parent = nullptr);

  /// Create a global module fragment for a C++ module interface unit.

  Module *createPrivateModuleFragmentForInterfaceUnit(Module *Parent,

                                                      SourceLocation Loc);

  /// Create a new module for a C++ module interface unit.

  /// The module must not already exist, and will be configured for the current

  /// compilation.

  ///

  /// Note that this also sets the current module to the newly-created module.

  ///

  /// \returns The newly-created module.

  Module *createModuleForInterfaceUnit(SourceLocation Loc, StringRef Name);

  /// Create a C++20 header unit.

  Module *createHeaderUnit(SourceLocation Loc, StringRef Name,

                           Module::Header H);

  /// Infer the contents of a framework module map from the given

  /// framework directory.

  Module *inferFrameworkModule(const DirectoryEntry *FrameworkDir,

                               bool IsSystem, Module *Parent);

  /// Create a new top-level module that is shadowed by

  /// \p ShadowingModule.

  Module *createShadowedModule(StringRef Name, bool IsFramework,

                               Module *ShadowingModule);

  /// Creates a new declaration scope for module names, allowing

  /// previously defined modules to shadow definitions from the new scope.

  ///

  /// \note Module names from earlier scopes will shadow names from the new

  /// scope, which is the opposite of how shadowing works for variables.

  void finishModuleDeclarationScope() { CurrentModuleScopeID += 1; }

  bool mayShadowNewModule(Module *ExistingModule) {

    assert(!ExistingModule->Parent && "expected top-level module");

    assert(ModuleScopeIDs.count(ExistingModule) && "unknown module");

    return ModuleScopeIDs[ExistingModule] < CurrentModuleScopeID;

  }

  /// Check whether a framework module can be inferred in the given directory.

  bool canInferFrameworkModule(const DirectoryEntry *Dir) const {

    auto It = InferredDirectories.find(Dir);

    return It != InferredDirectories.end() && It->getSecond().InferModules;

  }

  /// Retrieve the module map file containing the definition of the given

  /// module.

  ///

  /// \param Module The module whose module map file will be returned, if known.

  ///

  /// \returns The file entry for the module map file containing the given

  /// module, or nullptr if the module definition was inferred.

  OptionalFileEntryRef getContainingModuleMapFile(const Module *Module) const;

  /// Get the module map file that (along with the module name) uniquely

  /// identifies this module.

  ///

  /// The particular module that \c Name refers to may depend on how the module

  /// was found in header search. However, the combination of \c Name and

  /// this module map will be globally unique for top-level modules. In the case

  /// of inferred modules, returns the module map that allowed the inference

  /// (e.g. contained 'module *'). Otherwise, returns

  /// getContainingModuleMapFile().

  OptionalFileEntryRef getModuleMapFileForUniquing(const Module *M) const;

  void setInferredModuleAllowedBy(Module *M, const FileEntry *ModMap);

  /// Canonicalize \p Path in a manner suitable for a module map file. In

  /// particular, this canonicalizes the parent directory separately from the

  /// filename so that it does not affect header resolution relative to the

  /// modulemap.

  ///

  /// \returns an error code if any filesystem operations failed. In this case

  /// \p Path is not modified.

  std::error_code canonicalizeModuleMapPath(SmallVectorImpl<char> &Path);

  /// Get any module map files other than getModuleMapFileForUniquing(M)

  /// that define submodules of a top-level module \p M. This is cheaper than

  /// getting the module map file for each submodule individually, since the

  /// expected number of results is very small.

  AdditionalModMapsSet *getAdditionalModuleMapFiles(const Module *M) {

    auto I = AdditionalModMaps.find(M);

    if (I == AdditionalModMaps.end())

      return nullptr;

    return &I->second;

  }

  void addAdditionalModuleMapFile(const Module *M, const FileEntry *ModuleMap);

  /// Resolve all of the unresolved exports in the given module.

  ///

  /// \param Mod The module whose exports should be resolved.

  ///

  /// \param Complain Whether to emit diagnostics for failures.

  ///

  /// \returns true if any errors were encountered while resolving exports,

  /// false otherwise.

  bool resolveExports(Module *Mod, bool Complain);

  /// Resolve all of the unresolved uses in the given module.

  ///

  /// \param Mod The module whose uses should be resolved.

  ///

  /// \param Complain Whether to emit diagnostics for failures.

  ///

  /// \returns true if any errors were encountered while resolving uses,

  /// false otherwise.

  bool resolveUses(Module *Mod, bool Complain);

  /// Resolve all of the unresolved conflicts in the given module.

  ///

  /// \param Mod The module whose conflicts should be resolved.

  ///

  /// \param Complain Whether to emit diagnostics for failures.

  ///

  /// \returns true if any errors were encountered while resolving conflicts,

  /// false otherwise.

  bool resolveConflicts(Module *Mod, bool Complain);

  /// Sets the umbrella header of the given module to the given

  /// header.

  void setUmbrellaHeader(Module *Mod, FileEntryRef UmbrellaHeader,

                         const Twine &NameAsWritten,

                         const Twine &PathRelativeToRootModuleDirectory);

  /// Sets the umbrella directory of the given module to the given

  /// directory.

  void setUmbrellaDir(Module *Mod, const DirectoryEntry *UmbrellaDir,

                      const Twine &NameAsWritten,

                      const Twine &PathRelativeToRootModuleDirectory);

  /// Adds this header to the given module.

  /// \param Role The role of the header wrt the module.

  void addHeader(Module *Mod, Module::Header Header,

                 ModuleHeaderRole Role, bool Imported = false);

  /// Parse the given module map file, and record any modules we

  /// encounter.

  ///

  /// \param File The file to be parsed.

  ///

  /// \param IsSystem Whether this module map file is in a system header

  /// directory, and therefore should be considered a system module.

  ///

  /// \param HomeDir The directory in which relative paths within this module

  ///        map file will be resolved.

  ///

  /// \param ID The FileID of the file to process, if we've already entered it.

  ///

  /// \param Offset [inout] On input the offset at which to start parsing. On

  ///        output, the offset at which the module map terminated.

  ///

  /// \param ExternModuleLoc The location of the "extern module" declaration

  ///        that caused us to load this module map file, if any.

  ///

  /// \returns true if an error occurred, false otherwise.

  bool parseModuleMapFile(const FileEntry *File, bool IsSystem,

                          const DirectoryEntry *HomeDir,

                          FileID ID = FileID(), unsigned *Offset = nullptr,

                          SourceLocation ExternModuleLoc = SourceLocation());

  /// Dump the contents of the module map, for debugging purposes.

  void dump();

  using module_iterator = llvm::StringMap<Module *>::const_iterator;

  module_iterator module_begin() const { return Modules.begin(); }

  module_iterator module_end()   const { return Modules.end(); }

  llvm::iterator_range<module_iterator> modules() const {

    return {module_begin(), module_end()};

  }

  /// Cache a module load.  M might be nullptr.

  void cacheModuleLoad(const IdentifierInfo &II, Module *M) {

    CachedModuleLoads[&II] = M;

  }

  /// Return a cached module load.

  std::optional<Module *> getCachedModuleLoad(const IdentifierInfo &II) {

    auto I = CachedModuleLoads.find(&II);

    if (I == CachedModuleLoads.end())

      return std::nullopt;

    return I->second;

  }

};

} // namespace clang

#endif // LLVM_CLANG_LEX_MODULEMAP_H