Subversion Repositories QNX 8.QNX8 LLVM/Clang compiler suite

//===- 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 <vector>

namespace llvm {

class raw_ostream;

} // namespace llvm

namespace clang {

class FileManager;

class LangOptions;

class TargetInfo;

/// Describes the name of a module.

using ModuleId = SmallVector<std::pair<std::string, SourceLocation>, 2>;

/// 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}}); }

  /// 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;

  }

  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;

  }

};

/// 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;

  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 module interface unit.

    ModuleInterfaceUnit,

    /// This is a C++ 20 header unit.

    ModuleHeaderUnit,

    /// This is a C++ 20 module partition interface.

    ModulePartitionInterface,

    /// This is a C++ 20 module partition implementation.

    ModulePartitionImplementation,

    /// This is a fragment of the global module within some C++ module.

    GlobalModuleFragment,

    /// This is the private module fragment within some C++ module.

    PrivateModuleFragment,

  };

  /// 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.

  const DirectoryEntry *Directory = nullptr;

  /// 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.

  llvm::PointerUnion<const FileEntryRef::MapEntry *, const DirectoryEntry *>

      Umbrella;

  /// 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;

  /// Does this Module scope describe part of the purview of a standard named

  /// C++ module?

  bool isModulePurview() const {

    return Kind == ModuleInterfaceUnit || Kind == ModulePartitionInterface ||

           Kind == ModulePartitionImplementation ||

           Kind == PrivateModuleFragment;

  }

  /// Does this Module scope describe a fragment of the global module within

  /// some C++ module.

  bool isGlobalModule() const { return Kind == GlobalModuleFragment; }

  bool isPrivateModule() const { return Kind == PrivateModuleFragment; }

  bool isModuleMapModule() const { return Kind == ModuleMapModule; }

private:

  /// The submodules of this module, indexed by name.

  std::vector<Module *> 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 if this is a top-level module which has a

  /// corresponding serialized AST file, or null otherwise.

  OptionalFileEntryRef ASTFile;

  /// The top-level headers associated with this module.

  llvm::SmallSetVector<const FileEntry *, 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

  };

  static const int NumHeaderKinds = HK_Excluded + 1;

  /// Information about a header directive as found in the module map

  /// file.

  struct Header {

    std::string NameAsWritten;

    std::string PathRelativeToRootModuleDirectory;

    OptionalFileEntryRefDegradesToFileEntryPtr Entry;

    explicit operator bool() { return Entry.has_value(); }

  };

  /// Information about a directory name as found in the module map

  /// file.

  struct DirectoryName {

    std::string NameAsWritten;

    std::string PathRelativeToRootModuleDirectory;

    const DirectoryEntry *Entry;

    explicit operator bool() { return Entry; }

  };

  /// The headers that are part of this module.

  SmallVector<Header, 2> Headers[5];

  /// 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;

  /// An individual requirement: a feature name and a flag indicating

  /// the required state of that feature.

  using Requirement = std::pair<std::string, bool>;

  /// 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.

  unsigned IsUnimportable : 1;

  /// Whether we tried and failed to load a module file for this module.

  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.

  unsigned IsAvailable : 1;

  /// Whether this module was loaded from a module file.

  unsigned IsFromModuleFile : 1;

  /// Whether this is a framework module.

  unsigned IsFramework : 1;

  /// Whether this is an explicit submodule.

  unsigned IsExplicit : 1;

  /// Whether this is a "system" module (which assumes that all

  /// headers in it are system headers).

  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).

  unsigned IsExternC : 1;

  /// Whether this is an inferred submodule (module * { ... }).

  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.

  unsigned InferSubmodules : 1;

  /// Whether, when inferring submodules, the inferred submodules

  /// should be explicit.

  unsigned InferExplicitSubmodules : 1;

  /// Whether, when inferring submodules, the inferr submodules should

  /// export all modules they import (e.g., the equivalent of "export *").

  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.

  unsigned ConfigMacrosExhaustive : 1;

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

  /// and headers from used modules.

  unsigned NoUndeclaredIncludes : 1;

  /// Whether this module came from a "private" module map, found next

  /// to a regular (public) module map.

  unsigned ModuleMapIsPrivate : 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::SmallSetVector<Module *, 2> Imports;

  /// The set of top-level modules that affected the compilation of this module,

  /// but were not imported.

  llvm::SmallSetVector<Module *, 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 = llvm::PointerIntPair<Module *, 1, 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.

    Module *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(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[Name] = Parent->SubModules.size();

    Parent->SubModules.push_back(this);

  }

  /// 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 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();

  }

  bool isModuleInterfaceUnit() const {

    return Kind == ModuleInterfaceUnit || Kind == ModulePartitionInterface;

  }

  /// 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 for this module, if one was created.

  OptionalFileEntryRefDegradesToFileEntryPtr getASTFile() const {

    return getTopLevelModule()->ASTFile;

  }

  /// Set the serialized AST file for the top-level module of this module.

  void setASTFile(OptionalFileEntryRef File) {

    assert((!getASTFile() || getASTFile() == File) && "file path changed");

    getTopLevelModule()->ASTFile = File;

  }

  /// Retrieve the directory for which this module serves as the

  /// umbrella.

  DirectoryName getUmbrellaDir() const;

  /// Retrieve the header that serves as the umbrella header for this

  /// module.

  Header getUmbrellaHeader() const {

    if (auto *ME = Umbrella.dyn_cast<const FileEntryRef::MapEntry *>())

      return Header{UmbrellaAsWritten, UmbrellaRelativeToRootModuleDirectory,

                    FileEntryRef(*ME)};

    return Header{};

  }

  /// Determine whether this module has an umbrella directory that is

  /// not based on an umbrella header.

  bool hasUmbrellaDir() const {

    return Umbrella && Umbrella.is<const DirectoryEntry *>();

  }

  /// Add a top-level header associated with this module.

  void addTopHeader(const FileEntry *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<const FileEntry *> 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.

  Module *findSubmodule(StringRef Name) const;

  Module *findOrInferSubmodule(StringRef Name);

  /// 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() { return findSubmodule("<global>"); }

  /// 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() { return findSubmodule("<private>"); }

  /// 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<Module *>::iterator;

  using submodule_const_iterator = std::vector<Module *>::const_iterator;

  submodule_iterator submodule_begin() { return SubModules.begin(); }

  submodule_const_iterator submodule_begin() const {return SubModules.begin();}

  submodule_iterator submodule_end()   { return SubModules.end(); }

  submodule_const_iterator submodule_end() const { return SubModules.end(); }

  llvm::iterator_range<submodule_iterator> submodules() {

    return llvm::make_range(submodule_begin(), submodule_end());

  }

  llvm::iterator_range<submodule_const_iterator> submodules() const {

    return llvm::make_range(submodule_begin(), submodule_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->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,

                  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;

};

/// Abstracts clang modules and precompiled header files and holds

/// everything needed to generate debug info for an imported module

/// or PCH.

class ASTSourceDescriptor {

  StringRef PCHModuleName;

  StringRef Path;

  StringRef ASTFile;

  ASTFileSignature Signature;

  Module *ClangModule = nullptr;

public:

  ASTSourceDescriptor() = default;

  ASTSourceDescriptor(StringRef Name, StringRef Path, StringRef ASTFile,

                      ASTFileSignature Signature)

      : PCHModuleName(std::move(Name)), Path(std::move(Path)),

        ASTFile(std::move(ASTFile)), Signature(Signature) {}

  ASTSourceDescriptor(Module &M);

  std::string getModuleName() const;

  StringRef getPath() const { return Path; }

  StringRef getASTFile() const { return ASTFile; }

  ASTFileSignature getSignature() const { return Signature; }

  Module *getModuleOrNull() const { return ClangModule; }

};

} // namespace clang

#endif // LLVM_CLANG_BASIC_MODULE_H