xref: /llvm-project-15.0.7/clang/lib/Lex/ModuleMap.cpp (revision bf8da9d7)

//===--- ModuleMap.cpp - Describe the layout of modules ---------*- C++ -*-===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file defines the ModuleMap implementation, which describes the layout
// of a module as it relates to headers.
//
//===----------------------------------------------------------------------===//
#include "clang/Lex/ModuleMap.h"
#include "clang/Lex/Lexer.h"
#include "clang/Lex/LiteralSupport.h"
#include "clang/Lex/LexDiagnostic.h"
#include "clang/Basic/Diagnostic.h"
#include "clang/Basic/FileManager.h"
#include "clang/Basic/TargetInfo.h"
#include "clang/Basic/TargetOptions.h"
#include "llvm/Support/Allocator.h"
#include "llvm/Support/FileSystem.h"
#include "llvm/Support/Host.h"
#include "llvm/Support/PathV2.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/ADT/StringRef.h"
#include "llvm/ADT/StringSwitch.h"
using namespace clang;

Module::ExportDecl
ModuleMap::resolveExport(Module *Mod,
                         const Module::UnresolvedExportDecl &Unresolved,
                         bool Complain) {
  // We may have just a wildcard.
  if (Unresolved.Id.empty()) {
    assert(Unresolved.Wildcard && "Invalid unresolved export");
    return Module::ExportDecl(0, true);
  }

  // Find the starting module.
  Module *Context = lookupModuleUnqualified(Unresolved.Id[0].first, Mod);
  if (!Context) {
    if (Complain)
      Diags->Report(Unresolved.Id[0].second,
                    diag::err_mmap_missing_module_unqualified)
        << Unresolved.Id[0].first << Mod->getFullModuleName();

    return Module::ExportDecl();
  }

  // Dig into the module path.
  for (unsigned I = 1, N = Unresolved.Id.size(); I != N; ++I) {
    Module *Sub = lookupModuleQualified(Unresolved.Id[I].first,
                                        Context);
    if (!Sub) {
      if (Complain)
        Diags->Report(Unresolved.Id[I].second,
                      diag::err_mmap_missing_module_qualified)
          << Unresolved.Id[I].first << Context->getFullModuleName()
          << SourceRange(Unresolved.Id[0].second, Unresolved.Id[I-1].second);

      return Module::ExportDecl();
    }

    Context = Sub;
  }

  return Module::ExportDecl(Context, Unresolved.Wildcard);
}

ModuleMap::ModuleMap(FileManager &FileMgr, const DiagnosticConsumer &DC,
                     const LangOptions &LangOpts, const TargetInfo *Target)
  : LangOpts(LangOpts), Target(Target), BuiltinIncludeDir(0)
{
  llvm::IntrusiveRefCntPtr<DiagnosticIDs> DiagIDs(new DiagnosticIDs);
  Diags = llvm::IntrusiveRefCntPtr<DiagnosticsEngine>(
            new DiagnosticsEngine(DiagIDs));
  Diags->setClient(DC.clone(*Diags), /*ShouldOwnClient=*/true);
  SourceMgr = new SourceManager(*Diags, FileMgr);
}

ModuleMap::~ModuleMap() {
  for (llvm::StringMap<Module *>::iterator I = Modules.begin(),
                                        IEnd = Modules.end();
       I != IEnd; ++I) {
    delete I->getValue();
  }

  delete SourceMgr;
}

void ModuleMap::setTarget(const TargetInfo &Target) {
  assert((!this->Target || this->Target == &Target) &&
         "Improper target override");
  this->Target = &Target;
}

Module *ModuleMap::findModuleForHeader(const FileEntry *File) {
  llvm::DenseMap<const FileEntry *, Module *>::iterator Known
    = Headers.find(File);
  if (Known != Headers.end()) {
    // If a header corresponds to an unavailable module, don't report
    // that it maps to anything.
    if (!Known->second->isAvailable())
      return 0;

    return Known->second;
  }

  const DirectoryEntry *Dir = File->getDir();
  llvm::SmallVector<const DirectoryEntry *, 2> SkippedDirs;
  StringRef DirName = Dir->getName();

  // Keep walking up the directory hierarchy, looking for a directory with
  // an umbrella header.
  do {
    llvm::DenseMap<const DirectoryEntry *, Module *>::iterator KnownDir
      = UmbrellaDirs.find(Dir);
    if (KnownDir != UmbrellaDirs.end()) {
      Module *Result = KnownDir->second;

      // Search up the module stack until we find a module with an umbrella
      // directory.
      Module *UmbrellaModule = Result;
      while (!UmbrellaModule->getUmbrellaDir() && UmbrellaModule->Parent)
        UmbrellaModule = UmbrellaModule->Parent;

      if (UmbrellaModule->InferSubmodules) {
        // Infer submodules for each of the directories we found between
        // the directory of the umbrella header and the directory where
        // the actual header is located.
        bool Explicit = UmbrellaModule->InferExplicitSubmodules;

        for (unsigned I = SkippedDirs.size(); I != 0; --I) {
          // Find or create the module that corresponds to this directory name.
          StringRef Name = llvm::sys::path::stem(SkippedDirs[I-1]->getName());
          Result = findOrCreateModule(Name, Result, /*IsFramework=*/false,
                                      Explicit).first;

          // Associate the module and the directory.
          UmbrellaDirs[SkippedDirs[I-1]] = Result;

          // If inferred submodules export everything they import, add a
          // wildcard to the set of exports.
          if (UmbrellaModule->InferExportWildcard && Result->Exports.empty())
            Result->Exports.push_back(Module::ExportDecl(0, true));
        }

        // Infer a submodule with the same name as this header file.
        StringRef Name = llvm::sys::path::stem(File->getName());
        Result = findOrCreateModule(Name, Result, /*IsFramework=*/false,
                                    Explicit).first;

        // If inferred submodules export everything they import, add a
        // wildcard to the set of exports.
        if (UmbrellaModule->InferExportWildcard && Result->Exports.empty())
          Result->Exports.push_back(Module::ExportDecl(0, true));
      } else {
        // Record each of the directories we stepped through as being part of
        // the module we found, since the umbrella header covers them all.
        for (unsigned I = 0, N = SkippedDirs.size(); I != N; ++I)
          UmbrellaDirs[SkippedDirs[I]] = Result;
      }

      Headers[File] = Result;

      // If a header corresponds to an unavailable module, don't report
      // that it maps to anything.
      if (!Result->isAvailable())
        return 0;

      return Result;
    }

    SkippedDirs.push_back(Dir);

    // Retrieve our parent path.
    DirName = llvm::sys::path::parent_path(DirName);
    if (DirName.empty())
      break;

    // Resolve the parent path to a directory entry.
    Dir = SourceMgr->getFileManager().getDirectory(DirName);
  } while (Dir);

  return 0;
}

bool ModuleMap::isHeaderInUnavailableModule(const FileEntry *Header) {
  llvm::DenseMap<const FileEntry *, Module *>::iterator Known
    = Headers.find(Header);
  if (Known != Headers.end())
    return !Known->second->isAvailable();

  const DirectoryEntry *Dir = Header->getDir();
  llvm::SmallVector<const DirectoryEntry *, 2> SkippedDirs;
  StringRef DirName = Dir->getName();

  // Keep walking up the directory hierarchy, looking for a directory with
  // an umbrella header.
  do {
    llvm::DenseMap<const DirectoryEntry *, Module *>::iterator KnownDir
      = UmbrellaDirs.find(Dir);
    if (KnownDir != UmbrellaDirs.end()) {
      Module *Found = KnownDir->second;
      if (!Found->isAvailable())
        return true;

      // Search up the module stack until we find a module with an umbrella
      // directory.
      Module *UmbrellaModule = Found;
      while (!UmbrellaModule->getUmbrellaDir() && UmbrellaModule->Parent)
        UmbrellaModule = UmbrellaModule->Parent;

      if (UmbrellaModule->InferSubmodules) {
        for (unsigned I = SkippedDirs.size(); I != 0; --I) {
          // Find or create the module that corresponds to this directory name.
          StringRef Name = llvm::sys::path::stem(SkippedDirs[I-1]->getName());
          Found = lookupModuleQualified(Name, Found);
          if (!Found)
            return false;
          if (!Found->isAvailable())
            return true;
        }

        // Infer a submodule with the same name as this header file.
        StringRef Name = llvm::sys::path::stem(Header->getName());
        Found = lookupModuleQualified(Name, Found);
        if (!Found)
          return false;
      }

      return !Found->isAvailable();
    }

    SkippedDirs.push_back(Dir);

    // Retrieve our parent path.
    DirName = llvm::sys::path::parent_path(DirName);
    if (DirName.empty())
      break;

    // Resolve the parent path to a directory entry.
    Dir = SourceMgr->getFileManager().getDirectory(DirName);
  } while (Dir);

  return false;
}

Module *ModuleMap::findModule(StringRef Name) {
  llvm::StringMap<Module *>::iterator Known = Modules.find(Name);
  if (Known != Modules.end())
    return Known->getValue();

  return 0;
}

Module *ModuleMap::lookupModuleUnqualified(StringRef Name, Module *Context) {
  for(; Context; Context = Context->Parent) {
    if (Module *Sub = lookupModuleQualified(Name, Context))
      return Sub;
  }

  return findModule(Name);
}

Module *ModuleMap::lookupModuleQualified(StringRef Name, Module *Context) {
  if (!Context)
    return findModule(Name);

  return Context->findSubmodule(Name);
}

std::pair<Module *, bool>
ModuleMap::findOrCreateModule(StringRef Name, Module *Parent, bool IsFramework,
                              bool IsExplicit) {
  // Try to find an existing module with this name.
  if (Module *Sub = lookupModuleQualified(Name, Parent))
    return std::make_pair(Sub, false);

  // Create a new module with this name.
  Module *Result = new Module(Name, SourceLocation(), Parent, IsFramework,
                              IsExplicit);
  if (!Parent)
    Modules[Name] = Result;
  return std::make_pair(Result, true);
}

Module *
ModuleMap::inferFrameworkModule(StringRef ModuleName,
                                const DirectoryEntry *FrameworkDir,
                                bool IsSystem,
                                Module *Parent) {
  // Check whether we've already found this module.
  if (Module *Mod = lookupModuleQualified(ModuleName, Parent))
    return Mod;

  FileManager &FileMgr = SourceMgr->getFileManager();

  // Look for an umbrella header.
  SmallString<128> UmbrellaName = StringRef(FrameworkDir->getName());
  llvm::sys::path::append(UmbrellaName, "Headers");
  llvm::sys::path::append(UmbrellaName, ModuleName + ".h");
  const FileEntry *UmbrellaHeader = FileMgr.getFile(UmbrellaName);

  // FIXME: If there's no umbrella header, we could probably scan the
  // framework to load *everything*. But, it's not clear that this is a good
  // idea.
  if (!UmbrellaHeader)
    return 0;

  Module *Result = new Module(ModuleName, SourceLocation(), Parent,
                              /*IsFramework=*/true, /*IsExplicit=*/false);
  if (IsSystem)
    Result->IsSystem = IsSystem;

  if (!Parent)
    Modules[ModuleName] = Result;

  // umbrella header "umbrella-header-name"
  Result->Umbrella = UmbrellaHeader;
  Headers[UmbrellaHeader] = Result;
  UmbrellaDirs[UmbrellaHeader->getDir()] = Result;

  // export *
  Result->Exports.push_back(Module::ExportDecl(0, true));

  // module * { export * }
  Result->InferSubmodules = true;
  Result->InferExportWildcard = true;

  // Look for subframeworks.
  llvm::error_code EC;
  SmallString<128> SubframeworksDirName
    = StringRef(FrameworkDir->getName());
  llvm::sys::path::append(SubframeworksDirName, "Frameworks");
  SmallString<128> SubframeworksDirNameNative;
  llvm::sys::path::native(SubframeworksDirName.str(),
                          SubframeworksDirNameNative);
  for (llvm::sys::fs::directory_iterator
         Dir(SubframeworksDirNameNative.str(), EC), DirEnd;
       Dir != DirEnd && !EC; Dir.increment(EC)) {
    if (!StringRef(Dir->path()).endswith(".framework"))
      continue;

    if (const DirectoryEntry *SubframeworkDir
          = FileMgr.getDirectory(Dir->path())) {
      // FIXME: Do we want to warn about subframeworks without umbrella headers?
      inferFrameworkModule(llvm::sys::path::stem(Dir->path()), SubframeworkDir,
                           IsSystem, Result);
    }
  }

  return Result;
}

void ModuleMap::setUmbrellaHeader(Module *Mod, const FileEntry *UmbrellaHeader){
  Headers[UmbrellaHeader] = Mod;
  Mod->Umbrella = UmbrellaHeader;
  UmbrellaDirs[UmbrellaHeader->getDir()] = Mod;
}

void ModuleMap::setUmbrellaDir(Module *Mod, const DirectoryEntry *UmbrellaDir) {
  Mod->Umbrella = UmbrellaDir;
  UmbrellaDirs[UmbrellaDir] = Mod;
}

void ModuleMap::addHeader(Module *Mod, const FileEntry *Header) {
  Mod->Headers.push_back(Header);
  Headers[Header] = Mod;
}

const FileEntry *
ModuleMap::getContainingModuleMapFile(Module *Module) {
  if (Module->DefinitionLoc.isInvalid() || !SourceMgr)
    return 0;

  return SourceMgr->getFileEntryForID(
           SourceMgr->getFileID(Module->DefinitionLoc));
}

void ModuleMap::dump() {
  llvm::errs() << "Modules:";
  for (llvm::StringMap<Module *>::iterator M = Modules.begin(),
                                        MEnd = Modules.end();
       M != MEnd; ++M)
    M->getValue()->print(llvm::errs(), 2);

  llvm::errs() << "Headers:";
  for (llvm::DenseMap<const FileEntry *, Module *>::iterator
            H = Headers.begin(),
         HEnd = Headers.end();
       H != HEnd; ++H) {
    llvm::errs() << "  \"" << H->first->getName() << "\" -> "
                 << H->second->getFullModuleName() << "\n";
  }
}

bool ModuleMap::resolveExports(Module *Mod, bool Complain) {
  bool HadError = false;
  for (unsigned I = 0, N = Mod->UnresolvedExports.size(); I != N; ++I) {
    Module::ExportDecl Export = resolveExport(Mod, Mod->UnresolvedExports[I],
                                              Complain);
    if (Export.getPointer() || Export.getInt())
      Mod->Exports.push_back(Export);
    else
      HadError = true;
  }
  Mod->UnresolvedExports.clear();
  return HadError;
}

Module *ModuleMap::inferModuleFromLocation(FullSourceLoc Loc) {
  if (Loc.isInvalid())
    return 0;

  // Use the expansion location to determine which module we're in.
  FullSourceLoc ExpansionLoc = Loc.getExpansionLoc();
  if (!ExpansionLoc.isFileID())
    return 0;


  const SourceManager &SrcMgr = Loc.getManager();
  FileID ExpansionFileID = ExpansionLoc.getFileID();

  while (const FileEntry *ExpansionFile
           = SrcMgr.getFileEntryForID(ExpansionFileID)) {
    // Find the module that owns this header (if any).
    if (Module *Mod = findModuleForHeader(ExpansionFile))
      return Mod;

    // No module owns this header, so look up the inclusion chain to see if
    // any included header has an associated module.
    SourceLocation IncludeLoc = SrcMgr.getIncludeLoc(ExpansionFileID);
    if (IncludeLoc.isInvalid())
      return 0;

    ExpansionFileID = SrcMgr.getFileID(IncludeLoc);
  }

  return 0;
}

//----------------------------------------------------------------------------//
// Module map file parser
//----------------------------------------------------------------------------//

namespace clang {
  /// \brief A token in a module map file.
  struct MMToken {
    enum TokenKind {
      Comma,
      EndOfFile,
      HeaderKeyword,
      Identifier,
      ExplicitKeyword,
      ExportKeyword,
      FrameworkKeyword,
      ModuleKeyword,
      Period,
      UmbrellaKeyword,
      RequiresKeyword,
      Star,
      StringLiteral,
      LBrace,
      RBrace,
      LSquare,
      RSquare
    } Kind;

    unsigned Location;
    unsigned StringLength;
    const char *StringData;

    void clear() {
      Kind = EndOfFile;
      Location = 0;
      StringLength = 0;
      StringData = 0;
    }

    bool is(TokenKind K) const { return Kind == K; }

    SourceLocation getLocation() const {
      return SourceLocation::getFromRawEncoding(Location);
    }

    StringRef getString() const {
      return StringRef(StringData, StringLength);
    }
  };

  class ModuleMapParser {
    Lexer &L;
    SourceManager &SourceMgr;
    DiagnosticsEngine &Diags;
    ModuleMap &Map;

    /// \brief The directory that this module map resides in.
    const DirectoryEntry *Directory;

    /// \brief The directory containing Clang-supplied headers.
    const DirectoryEntry *BuiltinIncludeDir;

    /// \brief Whether an error occurred.
    bool HadError;

    /// \brief Default target information, used only for string literal
    /// parsing.
    TargetInfo *Target;

    /// \brief Stores string data for the various string literals referenced
    /// during parsing.
    llvm::BumpPtrAllocator StringData;

    /// \brief The current token.
    MMToken Tok;

    /// \brief The active module.
    Module *ActiveModule;

    /// \brief Consume the current token and return its location.
    SourceLocation consumeToken();

    /// \brief Skip tokens until we reach the a token with the given kind
    /// (or the end of the file).
    void skipUntil(MMToken::TokenKind K);

    typedef llvm::SmallVector<std::pair<std::string, SourceLocation>, 2>
      ModuleId;
    bool parseModuleId(ModuleId &Id);
    void parseModuleDecl();
    void parseRequiresDecl();
    void parseHeaderDecl(SourceLocation UmbrellaLoc);
    void parseUmbrellaDirDecl(SourceLocation UmbrellaLoc);
    void parseExportDecl();
    void parseInferredSubmoduleDecl(bool Explicit);

    const DirectoryEntry *getOverriddenHeaderSearchDir();

  public:
    explicit ModuleMapParser(Lexer &L, SourceManager &SourceMgr,
                             DiagnosticsEngine &Diags,
                             ModuleMap &Map,
                             const DirectoryEntry *Directory,
                             const DirectoryEntry *BuiltinIncludeDir)
      : L(L), SourceMgr(SourceMgr), Diags(Diags), Map(Map),
        Directory(Directory), BuiltinIncludeDir(BuiltinIncludeDir),
        HadError(false), ActiveModule(0)
    {
      TargetOptions TargetOpts;
      TargetOpts.Triple = llvm::sys::getDefaultTargetTriple();
      Target = TargetInfo::CreateTargetInfo(Diags, TargetOpts);

      Tok.clear();
      consumeToken();
    }

    bool parseModuleMapFile();
  };
}

SourceLocation ModuleMapParser::consumeToken() {
retry:
  SourceLocation Result = Tok.getLocation();
  Tok.clear();

  Token LToken;
  L.LexFromRawLexer(LToken);
  Tok.Location = LToken.getLocation().getRawEncoding();
  switch (LToken.getKind()) {
  case tok::raw_identifier:
    Tok.StringData = LToken.getRawIdentifierData();
    Tok.StringLength = LToken.getLength();
    Tok.Kind = llvm::StringSwitch<MMToken::TokenKind>(Tok.getString())
                 .Case("header", MMToken::HeaderKeyword)
                 .Case("explicit", MMToken::ExplicitKeyword)
                 .Case("export", MMToken::ExportKeyword)
                 .Case("framework", MMToken::FrameworkKeyword)
                 .Case("module", MMToken::ModuleKeyword)
                 .Case("requires", MMToken::RequiresKeyword)
                 .Case("umbrella", MMToken::UmbrellaKeyword)
                 .Default(MMToken::Identifier);
    break;

  case tok::comma:
    Tok.Kind = MMToken::Comma;
    break;

  case tok::eof:
    Tok.Kind = MMToken::EndOfFile;
    break;

  case tok::l_brace:
    Tok.Kind = MMToken::LBrace;
    break;

  case tok::l_square:
    Tok.Kind = MMToken::LSquare;
    break;

  case tok::period:
    Tok.Kind = MMToken::Period;
    break;

  case tok::r_brace:
    Tok.Kind = MMToken::RBrace;
    break;

  case tok::r_square:
    Tok.Kind = MMToken::RSquare;
    break;

  case tok::star:
    Tok.Kind = MMToken::Star;
    break;

  case tok::string_literal: {
    // Parse the string literal.
    LangOptions LangOpts;
    StringLiteralParser StringLiteral(&LToken, 1, SourceMgr, LangOpts, *Target);
    if (StringLiteral.hadError)
      goto retry;

    // Copy the string literal into our string data allocator.
    unsigned Length = StringLiteral.GetStringLength();
    char *Saved = StringData.Allocate<char>(Length + 1);
    memcpy(Saved, StringLiteral.GetString().data(), Length);
    Saved[Length] = 0;

    // Form the token.
    Tok.Kind = MMToken::StringLiteral;
    Tok.StringData = Saved;
    Tok.StringLength = Length;
    break;
  }

  case tok::comment:
    goto retry;

  default:
    Diags.Report(LToken.getLocation(), diag::err_mmap_unknown_token);
    HadError = true;
    goto retry;
  }

  return Result;
}

void ModuleMapParser::skipUntil(MMToken::TokenKind K) {
  unsigned braceDepth = 0;
  unsigned squareDepth = 0;
  do {
    switch (Tok.Kind) {
    case MMToken::EndOfFile:
      return;

    case MMToken::LBrace:
      if (Tok.is(K) && braceDepth == 0 && squareDepth == 0)
        return;

      ++braceDepth;
      break;

    case MMToken::LSquare:
      if (Tok.is(K) && braceDepth == 0 && squareDepth == 0)
        return;

      ++squareDepth;
      break;

    case MMToken::RBrace:
      if (braceDepth > 0)
        --braceDepth;
      else if (Tok.is(K))
        return;
      break;

    case MMToken::RSquare:
      if (squareDepth > 0)
        --squareDepth;
      else if (Tok.is(K))
        return;
      break;

    default:
      if (braceDepth == 0 && squareDepth == 0 && Tok.is(K))
        return;
      break;
    }

   consumeToken();
  } while (true);
}

/// \brief Parse a module-id.
///
///   module-id:
///     identifier
///     identifier '.' module-id
///
/// \returns true if an error occurred, false otherwise.
bool ModuleMapParser::parseModuleId(ModuleId &Id) {
  Id.clear();
  do {
    if (Tok.is(MMToken::Identifier)) {
      Id.push_back(std::make_pair(Tok.getString(), Tok.getLocation()));
      consumeToken();
    } else {
      Diags.Report(Tok.getLocation(), diag::err_mmap_expected_module_name);
      return true;
    }

    if (!Tok.is(MMToken::Period))
      break;

    consumeToken();
  } while (true);

  return false;
}

namespace {
  /// \brief Enumerates the known attributes.
  enum AttributeKind {
    /// \brief An unknown attribute.
    AT_unknown,
    /// \brief The 'system' attribute.
    AT_system
  };
}

/// \brief Parse a module declaration.
///
///   module-declaration:
///     'explicit'[opt] 'framework'[opt] 'module' module-id attributes[opt]
///       { module-member* }
///
///   attributes:
///     attribute attributes
///     attribute
///
///   attribute:
///     [ identifier ]
///
///   module-member:
///     requires-declaration
///     header-declaration
///     submodule-declaration
///     export-declaration
///
///   submodule-declaration:
///     module-declaration
///     inferred-submodule-declaration
void ModuleMapParser::parseModuleDecl() {
  assert(Tok.is(MMToken::ExplicitKeyword) || Tok.is(MMToken::ModuleKeyword) ||
         Tok.is(MMToken::FrameworkKeyword));
  // Parse 'explicit' or 'framework' keyword, if present.
  SourceLocation ExplicitLoc;
  bool Explicit = false;
  bool Framework = false;

  // Parse 'explicit' keyword, if present.
  if (Tok.is(MMToken::ExplicitKeyword)) {
    ExplicitLoc = consumeToken();
    Explicit = true;
  }

  // Parse 'framework' keyword, if present.
  if (Tok.is(MMToken::FrameworkKeyword)) {
    consumeToken();
    Framework = true;
  }

  // Parse 'module' keyword.
  if (!Tok.is(MMToken::ModuleKeyword)) {
    Diags.Report(Tok.getLocation(), diag::err_mmap_expected_module);
    consumeToken();
    HadError = true;
    return;
  }
  consumeToken(); // 'module' keyword

  // If we have a wildcard for the module name, this is an inferred submodule.
  // Parse it.
  if (Tok.is(MMToken::Star))
    return parseInferredSubmoduleDecl(Explicit);

  // Parse the module name.
  ModuleId Id;
  if (parseModuleId(Id)) {
    HadError = true;
    return;
  }

  if (ActiveModule) {
    if (Id.size() > 1) {
      Diags.Report(Id.front().second, diag::err_mmap_nested_submodule_id)
        << SourceRange(Id.front().second, Id.back().second);

      HadError = true;
      return;
    }
  } else if (Id.size() == 1 && Explicit) {
    // Top-level modules can't be explicit.
    Diags.Report(ExplicitLoc, diag::err_mmap_explicit_top_level);
    Explicit = false;
    ExplicitLoc = SourceLocation();
    HadError = true;
  }

  Module *PreviousActiveModule = ActiveModule;
  if (Id.size() > 1) {
    // This module map defines a submodule. Go find the module of which it
    // is a submodule.
    ActiveModule = 0;
    for (unsigned I = 0, N = Id.size() - 1; I != N; ++I) {
      if (Module *Next = Map.lookupModuleQualified(Id[I].first, ActiveModule)) {
        ActiveModule = Next;
        continue;
      }

      if (ActiveModule) {
        Diags.Report(Id[I].second, diag::err_mmap_missing_module_qualified)
          << Id[I].first << ActiveModule->getTopLevelModule();
      } else {
        Diags.Report(Id[I].second, diag::err_mmap_expected_module_name);
      }
      HadError = true;
      return;
    }
  }

  StringRef ModuleName = Id.back().first;
  SourceLocation ModuleNameLoc = Id.back().second;

  // Parse the optional attribute list.
  bool IsSystem = false;
  while (Tok.is(MMToken::LSquare)) {
    // Consume the '['.
    SourceLocation LSquareLoc = consumeToken();

    // Check whether we have an attribute name here.
    if (!Tok.is(MMToken::Identifier)) {
      Diags.Report(Tok.getLocation(), diag::err_mmap_expected_attribute);
      skipUntil(MMToken::RSquare);
      if (Tok.is(MMToken::RSquare))
        consumeToken();
      continue;
    }

    // Decode the attribute name.
    AttributeKind Attribute
      = llvm::StringSwitch<AttributeKind>(Tok.getString())
        .Case("system", AT_system)
        .Default(AT_unknown);
    switch (Attribute) {
    case AT_unknown:
      Diags.Report(Tok.getLocation(), diag::warn_mmap_unknown_attribute)
        << Tok.getString();
      break;

    case AT_system:
      IsSystem = true;
      break;
    }
    consumeToken();

    // Consume the ']'.
    if (!Tok.is(MMToken::RSquare)) {
      Diags.Report(Tok.getLocation(), diag::err_mmap_expected_rsquare);
      Diags.Report(LSquareLoc, diag::note_mmap_lsquare_match);
      skipUntil(MMToken::RSquare);
    }

    if (Tok.is(MMToken::RSquare))
      consumeToken();
  }

  // Parse the opening brace.
  if (!Tok.is(MMToken::LBrace)) {
    Diags.Report(Tok.getLocation(), diag::err_mmap_expected_lbrace)
      << ModuleName;
    HadError = true;
    return;
  }
  SourceLocation LBraceLoc = consumeToken();

  // Determine whether this (sub)module has already been defined.
  if (Module *Existing = Map.lookupModuleQualified(ModuleName, ActiveModule)) {
    if (Existing->DefinitionLoc.isInvalid() && !ActiveModule) {
      // Skip the module definition.
      skipUntil(MMToken::RBrace);
      if (Tok.is(MMToken::RBrace))
        consumeToken();
      else {
        Diags.Report(Tok.getLocation(), diag::err_mmap_expected_rbrace);
        Diags.Report(LBraceLoc, diag::note_mmap_lbrace_match);
        HadError = true;
      }
      return;
    }

    Diags.Report(ModuleNameLoc, diag::err_mmap_module_redefinition)
      << ModuleName;
    Diags.Report(Existing->DefinitionLoc, diag::note_mmap_prev_definition);

    // Skip the module definition.
    skipUntil(MMToken::RBrace);
    if (Tok.is(MMToken::RBrace))
      consumeToken();

    HadError = true;
    return;
  }

  // Start defining this module.
  ActiveModule = Map.findOrCreateModule(ModuleName, ActiveModule, Framework,
                                        Explicit).first;
  ActiveModule->DefinitionLoc = ModuleNameLoc;
  if (IsSystem)
    ActiveModule->IsSystem = true;

  bool Done = false;
  do {
    switch (Tok.Kind) {
    case MMToken::EndOfFile:
    case MMToken::RBrace:
      Done = true;
      break;

    case MMToken::ExplicitKeyword:
    case MMToken::FrameworkKeyword:
    case MMToken::ModuleKeyword:
      parseModuleDecl();
      break;

    case MMToken::ExportKeyword:
      parseExportDecl();
      break;

    case MMToken::RequiresKeyword:
      parseRequiresDecl();
      break;

    case MMToken::UmbrellaKeyword: {
      SourceLocation UmbrellaLoc = consumeToken();
      if (Tok.is(MMToken::HeaderKeyword))
        parseHeaderDecl(UmbrellaLoc);
      else
        parseUmbrellaDirDecl(UmbrellaLoc);
      break;
    }

    case MMToken::HeaderKeyword:
      parseHeaderDecl(SourceLocation());
      break;

    default:
      Diags.Report(Tok.getLocation(), diag::err_mmap_expected_member);
      consumeToken();
      break;
    }
  } while (!Done);

  if (Tok.is(MMToken::RBrace))
    consumeToken();
  else {
    Diags.Report(Tok.getLocation(), diag::err_mmap_expected_rbrace);
    Diags.Report(LBraceLoc, diag::note_mmap_lbrace_match);
    HadError = true;
  }

  // We're done parsing this module. Pop back to the previous module.
  ActiveModule = PreviousActiveModule;
}

/// \brief Parse a requires declaration.
///
///   requires-declaration:
///     'requires' feature-list
///
///   feature-list:
///     identifier ',' feature-list
///     identifier
void ModuleMapParser::parseRequiresDecl() {
  assert(Tok.is(MMToken::RequiresKeyword));

  // Parse 'requires' keyword.
  consumeToken();

  // Parse the feature-list.
  do {
    if (!Tok.is(MMToken::Identifier)) {
      Diags.Report(Tok.getLocation(), diag::err_mmap_expected_feature);
      HadError = true;
      return;
    }

    // Consume the feature name.
    std::string Feature = Tok.getString();
    consumeToken();

    // Add this feature.
    ActiveModule->addRequirement(Feature, Map.LangOpts, *Map.Target);

    if (!Tok.is(MMToken::Comma))
      break;

    // Consume the comma.
    consumeToken();
  } while (true);
}

/// \brief Append to \p Paths the set of paths needed to get to the
/// subframework in which the given module lives.
static void appendSubframeworkPaths(Module *Mod,
                                    llvm::SmallVectorImpl<char> &Path) {
  // Collect the framework names from the given module to the top-level module.
  llvm::SmallVector<StringRef, 2> Paths;
  for (; Mod; Mod = Mod->Parent) {
    if (Mod->IsFramework)
      Paths.push_back(Mod->Name);
  }

  if (Paths.empty())
    return;

  // Add Frameworks/Name.framework for each subframework.
  for (unsigned I = Paths.size() - 1; I != 0; --I) {
    llvm::sys::path::append(Path, "Frameworks");
    llvm::sys::path::append(Path, Paths[I-1] + ".framework");
  }
}

/// \brief Determine whether the given file name is the name of a builtin
/// header, supplied by Clang to replace, override, or augment existing system
/// headers.
static bool isBuiltinHeader(StringRef FileName) {
  return llvm::StringSwitch<bool>(FileName)
      .Case("float.h", true)
      .Case("iso646.h", true)
      .Case("limits.h", true)
      .Case("stdalign.h", true)
      .Case("stdarg.h", true)
      .Case("stdbool.h", true)
      .Case("stddef.h", true)
      .Case("stdint.h", true)
      .Case("tgmath.h", true)
      .Case("unwind.h", true)
      .Default(false);
}

/// \brief Parse a header declaration.
///
///   header-declaration:
///     'umbrella'[opt] 'header' string-literal
void ModuleMapParser::parseHeaderDecl(SourceLocation UmbrellaLoc) {
  assert(Tok.is(MMToken::HeaderKeyword));
  consumeToken();

  bool Umbrella = UmbrellaLoc.isValid();

  // Parse the header name.
  if (!Tok.is(MMToken::StringLiteral)) {
    Diags.Report(Tok.getLocation(), diag::err_mmap_expected_header)
      << "header";
    HadError = true;
    return;
  }
  std::string FileName = Tok.getString();
  SourceLocation FileNameLoc = consumeToken();

  // Check whether we already have an umbrella.
  if (Umbrella && ActiveModule->Umbrella) {
    Diags.Report(FileNameLoc, diag::err_mmap_umbrella_clash)
      << ActiveModule->getFullModuleName();
    HadError = true;
    return;
  }

  // Look for this file.
  const FileEntry *File = 0;
  const FileEntry *BuiltinFile = 0;
  SmallString<128> PathName;
  if (llvm::sys::path::is_absolute(FileName)) {
    PathName = FileName;
    File = SourceMgr.getFileManager().getFile(PathName);
  } else if (const DirectoryEntry *Dir = getOverriddenHeaderSearchDir()) {
    PathName = Dir->getName();
    llvm::sys::path::append(PathName, FileName);
    File = SourceMgr.getFileManager().getFile(PathName);
  } else {
    // Search for the header file within the search directory.
    PathName = Directory->getName();
    unsigned PathLength = PathName.size();

    if (ActiveModule->isPartOfFramework()) {
      appendSubframeworkPaths(ActiveModule, PathName);

      // Check whether this file is in the public headers.
      llvm::sys::path::append(PathName, "Headers");
      llvm::sys::path::append(PathName, FileName);
      File = SourceMgr.getFileManager().getFile(PathName);

      if (!File) {
        // Check whether this file is in the private headers.
        PathName.resize(PathLength);
        llvm::sys::path::append(PathName, "PrivateHeaders");
        llvm::sys::path::append(PathName, FileName);
        File = SourceMgr.getFileManager().getFile(PathName);
      }
    } else {
      // Lookup for normal headers.
      llvm::sys::path::append(PathName, FileName);
      File = SourceMgr.getFileManager().getFile(PathName);

      // If this is a system module with a top-level header, this header
      // may have a counterpart (or replacement) in the set of headers
      // supplied by Clang. Find that builtin header.
      if (ActiveModule->IsSystem && !Umbrella && BuiltinIncludeDir &&
          BuiltinIncludeDir != Directory && isBuiltinHeader(FileName)) {
        SmallString<128> BuiltinPathName(BuiltinIncludeDir->getName());
        llvm::sys::path::append(BuiltinPathName, FileName);
        BuiltinFile = SourceMgr.getFileManager().getFile(BuiltinPathName);

        // If Clang supplies this header but the underlying system does not,
        // just silently swap in our builtin version. Otherwise, we'll end
        // up adding both (later).
        if (!File && BuiltinFile) {
          File = BuiltinFile;
          BuiltinFile = 0;
        }
      }
    }
  }

  // FIXME: We shouldn't be eagerly stat'ing every file named in a module map.
  // Come up with a lazy way to do this.
  if (File) {
    if (const Module *OwningModule = Map.Headers[File]) {
      Diags.Report(FileNameLoc, diag::err_mmap_header_conflict)
        << FileName << OwningModule->getFullModuleName();
      HadError = true;
    } else if (Umbrella) {
      const DirectoryEntry *UmbrellaDir = File->getDir();
      if ((OwningModule = Map.UmbrellaDirs[UmbrellaDir])) {
        Diags.Report(UmbrellaLoc, diag::err_mmap_umbrella_clash)
          << OwningModule->getFullModuleName();
        HadError = true;
      } else {
        // Record this umbrella header.
        Map.setUmbrellaHeader(ActiveModule, File);
      }
    } else {
      // Record this header.
      Map.addHeader(ActiveModule, File);

      // If there is a builtin counterpart to this file, add it now.
      if (BuiltinFile)
        Map.addHeader(ActiveModule, BuiltinFile);
    }
  } else {
    Diags.Report(FileNameLoc, diag::err_mmap_header_not_found)
      << Umbrella << FileName;
    HadError = true;
  }
}

/// \brief Parse an umbrella directory declaration.
///
///   umbrella-dir-declaration:
///     umbrella string-literal
void ModuleMapParser::parseUmbrellaDirDecl(SourceLocation UmbrellaLoc) {
  // Parse the directory name.
  if (!Tok.is(MMToken::StringLiteral)) {
    Diags.Report(Tok.getLocation(), diag::err_mmap_expected_header)
      << "umbrella";
    HadError = true;
    return;
  }

  std::string DirName = Tok.getString();
  SourceLocation DirNameLoc = consumeToken();

  // Check whether we already have an umbrella.
  if (ActiveModule->Umbrella) {
    Diags.Report(DirNameLoc, diag::err_mmap_umbrella_clash)
      << ActiveModule->getFullModuleName();
    HadError = true;
    return;
  }

  // Look for this file.
  const DirectoryEntry *Dir = 0;
  if (llvm::sys::path::is_absolute(DirName))
    Dir = SourceMgr.getFileManager().getDirectory(DirName);
  else {
    SmallString<128> PathName;
    PathName = Directory->getName();
    llvm::sys::path::append(PathName, DirName);
    Dir = SourceMgr.getFileManager().getDirectory(PathName);
  }

  if (!Dir) {
    Diags.Report(DirNameLoc, diag::err_mmap_umbrella_dir_not_found)
      << DirName;
    HadError = true;
    return;
  }

  if (Module *OwningModule = Map.UmbrellaDirs[Dir]) {
    Diags.Report(UmbrellaLoc, diag::err_mmap_umbrella_clash)
      << OwningModule->getFullModuleName();
    HadError = true;
    return;
  }

  // Record this umbrella directory.
  Map.setUmbrellaDir(ActiveModule, Dir);
}

/// \brief Parse a module export declaration.
///
///   export-declaration:
///     'export' wildcard-module-id
///
///   wildcard-module-id:
///     identifier
///     '*'
///     identifier '.' wildcard-module-id
void ModuleMapParser::parseExportDecl() {
  assert(Tok.is(MMToken::ExportKeyword));
  SourceLocation ExportLoc = consumeToken();

  // Parse the module-id with an optional wildcard at the end.
  ModuleId ParsedModuleId;
  bool Wildcard = false;
  do {
    if (Tok.is(MMToken::Identifier)) {
      ParsedModuleId.push_back(std::make_pair(Tok.getString(),
                                              Tok.getLocation()));
      consumeToken();

      if (Tok.is(MMToken::Period)) {
        consumeToken();
        continue;
      }

      break;
    }

    if(Tok.is(MMToken::Star)) {
      Wildcard = true;
      consumeToken();
      break;
    }

    Diags.Report(Tok.getLocation(), diag::err_mmap_export_module_id);
    HadError = true;
    return;
  } while (true);

  Module::UnresolvedExportDecl Unresolved = {
    ExportLoc, ParsedModuleId, Wildcard
  };
  ActiveModule->UnresolvedExports.push_back(Unresolved);
}

void ModuleMapParser::parseInferredSubmoduleDecl(bool Explicit) {
  assert(Tok.is(MMToken::Star));
  SourceLocation StarLoc = consumeToken();
  bool Failed = false;

  // Inferred modules must be submodules.
  if (!ActiveModule) {
    Diags.Report(StarLoc, diag::err_mmap_top_level_inferred_submodule);
    Failed = true;
  }

  // Inferred modules must have umbrella directories.
  if (!Failed && !ActiveModule->getUmbrellaDir()) {
    Diags.Report(StarLoc, diag::err_mmap_inferred_no_umbrella);
    Failed = true;
  }

  // Check for redefinition of an inferred module.
  if (!Failed && ActiveModule->InferSubmodules) {
    Diags.Report(StarLoc, diag::err_mmap_inferred_redef);
    if (ActiveModule->InferredSubmoduleLoc.isValid())
      Diags.Report(ActiveModule->InferredSubmoduleLoc,
                   diag::note_mmap_prev_definition);
    Failed = true;
  }

  // If there were any problems with this inferred submodule, skip its body.
  if (Failed) {
    if (Tok.is(MMToken::LBrace)) {
      consumeToken();
      skipUntil(MMToken::RBrace);
      if (Tok.is(MMToken::RBrace))
        consumeToken();
    }
    HadError = true;
    return;
  }

  // Note that we have an inferred submodule.
  ActiveModule->InferSubmodules = true;
  ActiveModule->InferredSubmoduleLoc = StarLoc;
  ActiveModule->InferExplicitSubmodules = Explicit;

  // Parse the opening brace.
  if (!Tok.is(MMToken::LBrace)) {
    Diags.Report(Tok.getLocation(), diag::err_mmap_expected_lbrace_wildcard);
    HadError = true;
    return;
  }
  SourceLocation LBraceLoc = consumeToken();

  // Parse the body of the inferred submodule.
  bool Done = false;
  do {
    switch (Tok.Kind) {
    case MMToken::EndOfFile:
    case MMToken::RBrace:
      Done = true;
      break;

    case MMToken::ExportKeyword: {
      consumeToken();
      if (Tok.is(MMToken::Star))
        ActiveModule->InferExportWildcard = true;
      else
        Diags.Report(Tok.getLocation(),
                     diag::err_mmap_expected_export_wildcard);
      consumeToken();
      break;
    }

    case MMToken::ExplicitKeyword:
    case MMToken::ModuleKeyword:
    case MMToken::HeaderKeyword:
    case MMToken::UmbrellaKeyword:
    default:
      Diags.Report(Tok.getLocation(), diag::err_mmap_expected_wildcard_member);
      consumeToken();
      break;
    }
  } while (!Done);

  if (Tok.is(MMToken::RBrace))
    consumeToken();
  else {
    Diags.Report(Tok.getLocation(), diag::err_mmap_expected_rbrace);
    Diags.Report(LBraceLoc, diag::note_mmap_lbrace_match);
    HadError = true;
  }
}

/// \brief If there is a specific header search directory due the presence
/// of an umbrella directory, retrieve that directory. Otherwise, returns null.
const DirectoryEntry *ModuleMapParser::getOverriddenHeaderSearchDir() {
  for (Module *Mod = ActiveModule; Mod; Mod = Mod->Parent) {
    // If we have an umbrella directory, use that.
    if (Mod->hasUmbrellaDir())
      return Mod->getUmbrellaDir();

    // If we have a framework directory, stop looking.
    if (Mod->IsFramework)
      return 0;
  }

  return 0;
}

/// \brief Parse a module map file.
///
///   module-map-file:
///     module-declaration*
bool ModuleMapParser::parseModuleMapFile() {
  do {
    switch (Tok.Kind) {
    case MMToken::EndOfFile:
      return HadError;

    case MMToken::ExplicitKeyword:
    case MMToken::ModuleKeyword:
    case MMToken::FrameworkKeyword:
      parseModuleDecl();
      break;

    case MMToken::Comma:
    case MMToken::ExportKeyword:
    case MMToken::HeaderKeyword:
    case MMToken::Identifier:
    case MMToken::LBrace:
    case MMToken::LSquare:
    case MMToken::Period:
    case MMToken::RBrace:
    case MMToken::RSquare:
    case MMToken::RequiresKeyword:
    case MMToken::Star:
    case MMToken::StringLiteral:
    case MMToken::UmbrellaKeyword:
      Diags.Report(Tok.getLocation(), diag::err_mmap_expected_module);
      HadError = true;
      consumeToken();
      break;
    }
  } while (true);
}

bool ModuleMap::parseModuleMapFile(const FileEntry *File) {
  assert(Target != 0 && "Missing target information");
  FileID ID = SourceMgr->createFileID(File, SourceLocation(), SrcMgr::C_User);
  const llvm::MemoryBuffer *Buffer = SourceMgr->getBuffer(ID);
  if (!Buffer)
    return true;

  // Parse this module map file.
  Lexer L(ID, SourceMgr->getBuffer(ID), *SourceMgr, MMapLangOpts);
  Diags->getClient()->BeginSourceFile(MMapLangOpts);
  ModuleMapParser Parser(L, *SourceMgr, *Diags, *this, File->getDir(),
                         BuiltinIncludeDir);
  bool Result = Parser.parseModuleMapFile();
  Diags->getClient()->EndSourceFile();

  return Result;
}