text: //===--- PPMacroExpansion.cpp - Top level Macro Expansion -----------------===//
  //
  // 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 implements the top level handling of macro expansion for the
  // preprocessor.
  //
  //===----------------------------------------------------------------------===//
  
  #include "clang/Basic/Attributes.h"
  #include "clang/Basic/Builtins.h"
  #include "clang/Basic/FileManager.h"
  #include "clang/Basic/IdentifierTable.h"
  #include "clang/Basic/LLVM.h"
  #include "clang/Basic/LangOptions.h"
  #include "clang/Basic/ObjCRuntime.h"
  #include "clang/Basic/SourceLocation.h"
  #include "clang/Basic/TargetInfo.h"
  #include "clang/Lex/CodeCompletionHandler.h"
  #include "clang/Lex/DirectoryLookup.h"
  #include "clang/Lex/ExternalPreprocessorSource.h"
  #include "clang/Lex/HeaderSearch.h"
  #include "clang/Lex/LexDiagnostic.h"
  #include "clang/Lex/LiteralSupport.h"
  #include "clang/Lex/MacroArgs.h"
  #include "clang/Lex/MacroInfo.h"
  #include "clang/Lex/Preprocessor.h"
  #include "clang/Lex/PreprocessorLexer.h"
  #include "clang/Lex/PreprocessorOptions.h"
  #include "clang/Lex/Token.h"
  #include "llvm/ADT/ArrayRef.h"
  #include "llvm/ADT/DenseMap.h"
  #include "llvm/ADT/DenseSet.h"
  #include "llvm/ADT/FoldingSet.h"
  #include "llvm/ADT/None.h"
  #include "llvm/ADT/Optional.h"
  #include "llvm/ADT/STLExtras.h"
  #include "llvm/ADT/SmallString.h"
  #include "llvm/ADT/SmallVector.h"
  #include "llvm/ADT/StringRef.h"
  #include "llvm/ADT/StringSwitch.h"
  #include "llvm/Support/Casting.h"
  #include "llvm/Support/ErrorHandling.h"
  #include "llvm/Support/Format.h"
  #include "llvm/Support/Path.h"
  #include "llvm/Support/raw_ostream.h"
  #include <algorithm>
  #include <cassert>
  #include <cstddef>
  #include <cstring>
  #include <ctime>
  #include <string>
  #include <tuple>
  #include <utility>
  
  using namespace clang;
  
  MacroDirective *
  Preprocessor::getLocalMacroDirectiveHistory(const IdentifierInfo *II) const {
    if (!II->hadMacroDefinition())
      return nullptr;
    auto Pos = CurSubmoduleState->Macros.find(II);
    return Pos == CurSubmoduleState->Macros.end() ? nullptr
                                                  : Pos->second.getLatest();
  }
  
  void Preprocessor::appendMacroDirective(IdentifierInfo *II, MacroDirective *MD){
    assert(MD && "MacroDirective should be non-zero!");
    assert(!MD->getPrevious() && "Already attached to a MacroDirective history.");
  
    MacroState &StoredMD = CurSubmoduleState->Macros[II];
    auto *OldMD = StoredMD.getLatest();
    MD->setPrevious(OldMD);
    StoredMD.setLatest(MD);
    StoredMD.overrideActiveModuleMacros(*this, II);
  
    if (needModuleMacros()) {
      // Track that we created a new macro directive, so we know we should
      // consider building a ModuleMacro for it when we get to the end of
      // the module.
      PendingModuleMacroNames.push_back(II);
    }
  
    // Set up the identifier as having associated macro history.
    II->setHasMacroDefinition(true);
    if (!MD->isDefined() && LeafModuleMacros.find(II) == LeafModuleMacros.end())
      II->setHasMacroDefinition(false);
    if (II->isFromAST())
      II->setChangedSinceDeserialization();
  }
  
  void Preprocessor::setLoadedMacroDirective(IdentifierInfo *II,
                                             MacroDirective *ED,
                                             MacroDirective *MD) {
    // Normally, when a macro is defined, it goes through appendMacroDirective()
    // above, which chains a macro to previous defines, undefs, etc.
    // However, in a pch, the whole macro history up to the end of the pch is
    // stored, so ASTReader goes through this function instead.
    // However, built-in macros are already registered in the Preprocessor
    // ctor, and ASTWriter stops writing the macro chain at built-in macros,
    // so in that case the chain from the pch needs to be spliced to the existing
    // built-in.
  
    assert(II && MD);
    MacroState &StoredMD = CurSubmoduleState->Macros[II];
  
    if (auto *OldMD = StoredMD.getLatest()) {
      // shouldIgnoreMacro() in ASTWriter also stops at macros from the
      // predefines buffer in module builds. However, in module builds, modules
      // are loaded completely before predefines are processed, so StoredMD
      // will be nullptr for them when they're loaded. StoredMD should only be
      // non-nullptr for builtins read from a pch file.
      assert(OldMD->getMacroInfo()->isBuiltinMacro() &&
             "only built-ins should have an entry here");
      assert(!OldMD->getPrevious() && "builtin should only have a single entry");
      ED->setPrevious(OldMD);
      StoredMD.setLatest(MD);
    } else {
      StoredMD = MD;
    }
  
    // Setup the identifier as having associated macro history.
    II->setHasMacroDefinition(true);
    if (!MD->isDefined() && LeafModuleMacros.find(II) == LeafModuleMacros.end())
      II->setHasMacroDefinition(false);
  }
  
  ModuleMacro *Preprocessor::addModuleMacro(Module *Mod, IdentifierInfo *II,
                                            MacroInfo *Macro,
                                            ArrayRef<ModuleMacro *> Overrides,
                                            bool &New) {
    llvm::FoldingSetNodeID ID;
    ModuleMacro::Profile(ID, Mod, II);
  
    void *InsertPos;
    if (auto *MM = ModuleMacros.FindNodeOrInsertPos(ID, InsertPos)) {
      New = false;
      return MM;
    }
  
    auto *MM = ModuleMacro::create(*this, Mod, II, Macro, Overrides);
    ModuleMacros.InsertNode(MM, InsertPos);
  
    // Each overridden macro is now overridden by one more macro.
    bool HidAny = false;
    for (auto *O : Overrides) {
      HidAny |= (O->NumOverriddenBy == 0);
      ++O->NumOverriddenBy;
    }
  
    // If we were the first overrider for any macro, it's no longer a leaf.
    auto &LeafMacros = LeafModuleMacros[II];
    if (HidAny) {
      llvm::erase_if(LeafMacros,
                     [](ModuleMacro *MM) { return MM->NumOverriddenBy != 0; });
    }
  
    // The new macro is always a leaf macro.
    LeafMacros.push_back(MM);
    // The identifier now has defined macros (that may or may not be visible).
    II->setHasMacroDefinition(true);
  
    New = true;
    return MM;
  }
  
  ModuleMacro *Preprocessor::getModuleMacro(Module *Mod,
                                            const IdentifierInfo *II) {
    llvm::FoldingSetNodeID ID;
    ModuleMacro::Profile(ID, Mod, II);
  
    void *InsertPos;
    return ModuleMacros.FindNodeOrInsertPos(ID, InsertPos);
  }
  
  void Preprocessor::updateModuleMacroInfo(const IdentifierInfo *II,
                                           ModuleMacroInfo &Info) {
    assert(Info.ActiveModuleMacrosGeneration !=
               CurSubmoduleState->VisibleModules.getGeneration() &&
           "don't need to update this macro name info");
    Info.ActiveModuleMacrosGeneration =
        CurSubmoduleState->VisibleModules.getGeneration();
  
    auto Leaf = LeafModuleMacros.find(II);
    if (Leaf == LeafModuleMacros.end()) {
      // No imported macros at all: nothing to do.
      return;
    }
  
    Info.ActiveModuleMacros.clear();
  
    // Every macro that's locally overridden is overridden by a visible macro.
    llvm::DenseMap<ModuleMacro *, int> NumHiddenOverrides;
    for (auto *O : Info.OverriddenMacros)
      NumHiddenOverrides[O] = -1;
  
    // Collect all macros that are not overridden by a visible macro.
    llvm::SmallVector<ModuleMacro *, 16> Worklist;
    for (auto *LeafMM : Leaf->second) {
      assert(LeafMM->getNumOverridingMacros() == 0 && "leaf macro overridden");
      if (NumHiddenOverrides.lookup(LeafMM) == 0)
        Worklist.push_back(LeafMM);
    }
    while (!Worklist.empty()) {
      auto *MM = Worklist.pop_back_val();
      if (CurSubmoduleState->VisibleModules.isVisible(MM->getOwningModule())) {
        // We only care about collecting definitions; undefinitions only act
        // to override other definitions.
        if (MM->getMacroInfo())
          Info.ActiveModuleMacros.push_back(MM);
      } else {
        for (auto *O : MM->overrides())
          if ((unsigned)++NumHiddenOverrides[O] == O->getNumOverridingMacros())
            Worklist.push_back(O);
      }
    }
    // Our reverse postorder walk found the macros in reverse order.
    std::reverse(Info.ActiveModuleMacros.begin(), Info.ActiveModuleMacros.end());
  
    // Determine whether the macro name is ambiguous.
    MacroInfo *MI = nullptr;
    bool IsSystemMacro = true;
    bool IsAmbiguous = false;
    if (auto *MD = Info.MD) {
      while (MD && isa<VisibilityMacroDirective>(MD))
        MD = MD->getPrevious();
      if (auto *DMD = dyn_cast_or_null<DefMacroDirective>(MD)) {
        MI = DMD->getInfo();
        IsSystemMacro &= SourceMgr.isInSystemHeader(DMD->getLocation());
      }
    }
    for (auto *Active : Info.ActiveModuleMacros) {
      auto *NewMI = Active->getMacroInfo();
  
      // Before marking the macro as ambiguous, check if this is a case where
      // both macros are in system headers. If so, we trust that the system
      // did not get it wrong. This also handles cases where Clang's own
      // headers have a different spelling of certain system macros:
      //   #define LONG_MAX __LONG_MAX__ (clang's limits.h)
      //   #define LONG_MAX 0x7fffffffffffffffL (system's limits.h)
      //
      // FIXME: Remove the defined-in-system-headers check. clang's limits.h
      // overrides the system limits.h's macros, so there's no conflict here.
      if (MI && NewMI != MI &&
          !MI->isIdenticalTo(*NewMI, *this, /*Syntactically=*/true))
        IsAmbiguous = true;
      IsSystemMacro &= Active->getOwningModule()->IsSystem ||
                       SourceMgr.isInSystemHeader(NewMI->getDefinitionLoc());
      MI = NewMI;
    }
    Info.IsAmbiguous = IsAmbiguous && !IsSystemMacro;
  }
  
  void Preprocessor::dumpMacroInfo(const IdentifierInfo *II) {
    ArrayRef<ModuleMacro*> Leaf;
    auto LeafIt = LeafModuleMacros.find(II);
    if (LeafIt != LeafModuleMacros.end())
      Leaf = LeafIt->second;
    const MacroState *State = nullptr;
    auto Pos = CurSubmoduleState->Macros.find(II);
    if (Pos != CurSubmoduleState->Macros.end())
      State = &Pos->second;
  
    llvm::errs() << "MacroState " << State << " " << II->getNameStart();
    if (State && State->isAmbiguous(*this, II))
      llvm::errs() << " ambiguous";
    if (State && !State->getOverriddenMacros().empty()) {
      llvm::errs() << " overrides";
      for (auto *O : State->getOverriddenMacros())
        llvm::errs() << " " << O->getOwningModule()->getFullModuleName();
    }
    llvm::errs() << "\n";
  
    // Dump local macro directives.
    for (auto *MD = State ? State->getLatest() : nullptr; MD;
         MD = MD->getPrevious()) {
      llvm::errs() << " ";
      MD->dump();
    }
  
    // Dump module macros.
    llvm::DenseSet<ModuleMacro*> Active;
    for (auto *MM : State ? State->getActiveModuleMacros(*this, II) : None)
      Active.insert(MM);
    llvm::DenseSet<ModuleMacro*> Visited;
    llvm::SmallVector<ModuleMacro *, 16> Worklist(Leaf.begin(), Leaf.end());
    while (!Worklist.empty()) {
      auto *MM = Worklist.pop_back_val();
      llvm::errs() << " ModuleMacro " << MM << " "
                   << MM->getOwningModule()->getFullModuleName();
      if (!MM->getMacroInfo())
        llvm::errs() << " undef";
  
      if (Active.count(MM))
        llvm::errs() << " active";
      else if (!CurSubmoduleState->VisibleModules.isVisible(
                   MM->getOwningModule()))
        llvm::errs() << " hidden";
      else if (MM->getMacroInfo())
        llvm::errs() << " overridden";
  
      if (!MM->overrides().empty()) {
        llvm::errs() << " overrides";
        for (auto *O : MM->overrides()) {
          llvm::errs() << " " << O->getOwningModule()->getFullModuleName();
          if (Visited.insert(O).second)
            Worklist.push_back(O);
        }
      }
      llvm::errs() << "\n";
      if (auto *MI = MM->getMacroInfo()) {
        llvm::errs() << "  ";
        MI->dump();
        llvm::errs() << "\n";
      }
    }
  }
  
  /// RegisterBuiltinMacro - Register the specified identifier in the identifier
  /// table and mark it as a builtin macro to be expanded.
  static IdentifierInfo *RegisterBuiltinMacro(Preprocessor &PP, const char *Name){
    // Get the identifier.
    IdentifierInfo *Id = PP.getIdentifierInfo(Name);
  
    // Mark it as being a macro that is builtin.
    MacroInfo *MI = PP.AllocateMacroInfo(SourceLocation());
    MI->setIsBuiltinMacro();
    PP.appendDefMacroDirective(Id, MI);
    return Id;
  }
  
  /// RegisterBuiltinMacros - Register builtin macros, such as __LINE__ with the
  /// identifier table.
  void Preprocessor::RegisterBuiltinMacros() {
    Ident__LINE__ = RegisterBuiltinMacro(*this, "__LINE__");
    Ident__FILE__ = RegisterBuiltinMacro(*this, "__FILE__");
    Ident__DATE__ = RegisterBuiltinMacro(*this, "__DATE__");
    Ident__TIME__ = RegisterBuiltinMacro(*this, "__TIME__");
    Ident__COUNTER__ = RegisterBuiltinMacro(*this, "__COUNTER__");
    Ident_Pragma  = RegisterBuiltinMacro(*this, "_Pragma");
    Ident__FLT_EVAL_METHOD__ = RegisterBuiltinMacro(*this, "__FLT_EVAL_METHOD__");
  
    // C++ Standing Document Extensions.
    if (getLangOpts().CPlusPlus)
      Ident__has_cpp_attribute =
          RegisterBuiltinMacro(*this, "__has_cpp_attribute");
    else
      Ident__has_cpp_attribute = nullptr;
  
    // GCC Extensions.
    Ident__BASE_FILE__     = RegisterBuiltinMacro(*this, "__BASE_FILE__");
    Ident__INCLUDE_LEVEL__ = RegisterBuiltinMacro(*this, "__INCLUDE_LEVEL__");
    Ident__TIMESTAMP__     = RegisterBuiltinMacro(*this, "__TIMESTAMP__");
  
    // Microsoft Extensions.
    if (getLangOpts().MicrosoftExt) {
      Ident__identifier = RegisterBuiltinMacro(*this, "__identifier");
      Ident__pragma = RegisterBuiltinMacro(*this, "__pragma");
    } else {
      Ident__identifier = nullptr;
      Ident__pragma = nullptr;
    }
  
    // Clang Extensions.
    Ident__FILE_NAME__      = RegisterBuiltinMacro(*this, "__FILE_NAME__");
    Ident__has_feature      = RegisterBuiltinMacro(*this, "__has_feature");
    Ident__has_extension    = RegisterBuiltinMacro(*this, "__has_extension");
    Ident__has_builtin      = RegisterBuiltinMacro(*this, "__has_builtin");
    Ident__has_attribute    = RegisterBuiltinMacro(*this, "__has_attribute");
    if (!getLangOpts().CPlusPlus)
      Ident__has_c_attribute = RegisterBuiltinMacro(*this, "__has_c_attribute");
    else
      Ident__has_c_attribute = nullptr;
  
    Ident__has_declspec = RegisterBuiltinMacro(*this, "__has_declspec_attribute");
    Ident__has_include      = RegisterBuiltinMacro(*this, "__has_include");
    Ident__has_include_next = RegisterBuiltinMacro(*this, "__has_include_next");
    Ident__has_warning      = RegisterBuiltinMacro(*this, "__has_warning");
    Ident__is_identifier    = RegisterBuiltinMacro(*this, "__is_identifier");
    Ident__is_target_arch   = RegisterBuiltinMacro(*this, "__is_target_arch");
    Ident__is_target_vendor = RegisterBuiltinMacro(*this, "__is_target_vendor");
    Ident__is_target_os     = RegisterBuiltinMacro(*this, "__is_target_os");
    Ident__is_target_environment =
        RegisterBuiltinMacro(*this, "__is_target_environment");
  
    // Modules.
    Ident__building_module  = RegisterBuiltinMacro(*this, "__building_module");
    if (!getLangOpts().CurrentModule.empty())
      Ident__MODULE__ = RegisterBuiltinMacro(*this, "__MODULE__");
    else
      Ident__MODULE__ = nullptr;
  }
  
  /// isTrivialSingleTokenExpansion - Return true if MI, which has a single token
  /// in its expansion, currently expands to that token literally.
  static bool isTrivialSingleTokenExpansion(const MacroInfo *MI,
                                            const IdentifierInfo *MacroIdent,
                                            Preprocessor &PP) {
    IdentifierInfo *II = MI->getReplacementToken(0).getIdentifierInfo();
  
    // If the token isn't an identifier, it's always literally expanded.
    if (!II) return true;
  
    // If the information about this identifier is out of date, update it from
    // the external source.
    if (II->isOutOfDate())
      PP.getExternalSource()->updateOutOfDateIdentifier(*II);
  
    // If the identifier is a macro, and if that macro is enabled, it may be
    // expanded so it's not a trivial expansion.
    if (auto *ExpansionMI = PP.getMacroInfo(II))
      if (ExpansionMI->isEnabled() &&
          // Fast expanding "#define X X" is ok, because X would be disabled.
          II != MacroIdent)
        return false;
  
    // If this is an object-like macro invocation, it is safe to trivially expand
    // it.
    if (MI->isObjectLike()) return true;
  
    // If this is a function-like macro invocation, it's safe to trivially expand
    // as long as the identifier is not a macro argument.
    return !llvm::is_contained(MI->params(), II);
  }
  
  /// isNextPPTokenLParen - Determine whether the next preprocessor token to be
  /// lexed is a '('.  If so, consume the token and return true, if not, this
  /// method should have no observable side-effect on the lexed tokens.
  bool Preprocessor::isNextPPTokenLParen() {
    // Do some quick tests for rejection cases.
    unsigned Val;
    if (CurLexer)
      Val = CurLexer->isNextPPTokenLParen();
    else
      Val = CurTokenLexer->isNextTokenLParen();
  
    if (Val == 2) {
      // We have run off the end.  If it's a source file we don't
      // examine enclosing ones (C99 5.1.1.2p4).  Otherwise walk up the
      // macro stack.
      if (CurPPLexer)
        return false;
      for (const IncludeStackInfo &Entry : llvm::reverse(IncludeMacroStack)) {
        if (Entry.TheLexer)
          Val = Entry.TheLexer->isNextPPTokenLParen();
        else
          Val = Entry.TheTokenLexer->isNextTokenLParen();
  
        if (Val != 2)
          break;
  
        // Ran off the end of a source file?
        if (Entry.ThePPLexer)
          return false;
      }
    }
  
    // Okay, if we know that the token is a '(', lex it and return.  Otherwise we
    // have found something that isn't a '(' or we found the end of the
    // translation unit.  In either case, return false.
    return Val == 1;
  }
  
  /// HandleMacroExpandedIdentifier - If an identifier token is read that is to be
  /// expanded as a macro, handle it and return the next token as 'Identifier'.
  bool Preprocessor::HandleMacroExpandedIdentifier(Token &Identifier,
                                                   const MacroDefinition &M) {
    emitMacroExpansionWarnings(Identifier);
  
    MacroInfo *MI = M.getMacroInfo();
  
    // If this is a macro expansion in the "#if !defined(x)" line for the file,
    // then the macro could expand to different things in other contexts, we need
    // to disable the optimization in this case.
    if (CurPPLexer) CurPPLexer->MIOpt.ExpandedMacro();
  
    // If this is a builtin macro, like __LINE__ or _Pragma, handle it specially.
    if (MI->isBuiltinMacro()) {
      if (Callbacks)
        Callbacks->MacroExpands(Identifier, M, Identifier.getLocation(),
                                /*Args=*/nullptr);
      ExpandBuiltinMacro(Identifier);
      return true;
    }
  
    /// Args - If this is a function-like macro expansion, this contains,
    /// for each macro argument, the list of tokens that were provided to the
    /// invocation.
    MacroArgs *Args = nullptr;
  
    // Remember where the end of the expansion occurred.  For an object-like
    // macro, this is the identifier.  For a function-like macro, this is the ')'.
    SourceLocation ExpansionEnd = Identifier.getLocation();
  
    // If this is a function-like macro, read the arguments.
    if (MI->isFunctionLike()) {
      // Remember that we are now parsing the arguments to a macro invocation.
      // Preprocessor directives used inside macro arguments are not portable, and
      // this enables the warning.
      InMacroArgs = true;
      ArgMacro = &Identifier;
  
      Args = ReadMacroCallArgumentList(Identifier, MI, ExpansionEnd);
  
      // Finished parsing args.
      InMacroArgs = false;
      ArgMacro = nullptr;
  
      // If there was an error parsing the arguments, bail out.
      if (!Args) return true;
  
      ++NumFnMacroExpanded;
    } else {
      ++NumMacroExpanded;
    }
  
    // Notice that this macro has been used.
    markMacroAsUsed(MI);
  
    // Remember where the token is expanded.
    SourceLocation ExpandLoc = Identifier.getLocation();
    SourceRange ExpansionRange(ExpandLoc, ExpansionEnd);
  
    if (Callbacks) {
      if (InMacroArgs) {
        // We can have macro expansion inside a conditional directive while
        // reading the function macro arguments. To ensure, in that case, that
        // MacroExpands callbacks still happen in source order, queue this
        // callback to have it happen after the function macro callback.
        DelayedMacroExpandsCallbacks.push_back(
            MacroExpandsInfo(Identifier, M, ExpansionRange));
      } else {
        Callbacks->MacroExpands(Identifier, M, ExpansionRange, Args);
        if (!DelayedMacroExpandsCallbacks.empty()) {
          for (const MacroExpandsInfo &Info : DelayedMacroExpandsCallbacks) {
            // FIXME: We lose macro args info with delayed callback.
            Callbacks->MacroExpands(Info.Tok, Info.MD, Info.Range,
                                    /*Args=*/nullptr);
          }
          DelayedMacroExpandsCallbacks.clear();
        }
      }
    }
  
    // If the macro definition is ambiguous, complain.
    if (M.isAmbiguous()) {
      Diag(Identifier, diag::warn_pp_ambiguous_macro)
        << Identifier.getIdentifierInfo();
      Diag(MI->getDefinitionLoc(), diag::note_pp_ambiguous_macro_chosen)
        << Identifier.getIdentifierInfo();
      M.forAllDefinitions([&](const MacroInfo *OtherMI) {
        if (OtherMI != MI)
          Diag(OtherMI->getDefinitionLoc(), diag::note_pp_ambiguous_macro_other)
            << Identifier.getIdentifierInfo();
      });
    }
  
    // If we started lexing a macro, enter the macro expansion body.
  
    // If this macro expands to no tokens, don't bother to push it onto the
    // expansion stack, only to take it right back off.
    if (MI->getNumTokens() == 0) {
      // No need for arg info.
      if (Args) Args->destroy(*this);
  
      // Propagate whitespace info as if we had pushed, then popped,
      // a macro context.
      Identifier.setFlag(Token::LeadingEmptyMacro);
      PropagateLineStartLeadingSpaceInfo(Identifier);
      ++NumFastMacroExpanded;
      return false;
    } else if (MI->getNumTokens() == 1 &&
               isTrivialSingleTokenExpansion(MI, Identifier.getIdentifierInfo(),
                                             *this)) {
      // Otherwise, if this macro expands into a single trivially-expanded
      // token: expand it now.  This handles common cases like
      // "#define VAL 42".
  
      // No need for arg info.
      if (Args) Args->destroy(*this);
  
      // Propagate the isAtStartOfLine/hasLeadingSpace markers of the macro
      // identifier to the expanded token.
      bool isAtStartOfLine = Identifier.isAtStartOfLine();
      bool hasLeadingSpace = Identifier.hasLeadingSpace();
  
      // Replace the result token.
      Identifier = MI->getReplacementToken(0);
  
      // Restore the StartOfLine/LeadingSpace markers.
      Identifier.setFlagValue(Token::StartOfLine , isAtStartOfLine);
      Identifier.setFlagValue(Token::LeadingSpace, hasLeadingSpace);
  
      // Update the tokens location to include both its expansion and physical
      // locations.
      SourceLocation Loc =
        SourceMgr.createExpansionLoc(Identifier.getLocation(), ExpandLoc,
                                     ExpansionEnd,Identifier.getLength());
      Identifier.setLocation(Loc);
  
      // If this is a disabled macro or #define X X, we must mark the result as
      // unexpandable.
      if (IdentifierInfo *NewII = Identifier.getIdentifierInfo()) {
        if (MacroInfo *NewMI = getMacroInfo(NewII))
          if (!NewMI->isEnabled() || NewMI == MI) {
            Identifier.setFlag(Token::DisableExpand);
            // Don't warn for "#define X X" like "#define bool bool" from
            // stdbool.h.
            if (NewMI != MI || MI->isFunctionLike())
              Diag(Identifier, diag::pp_disabled_macro_expansion);
          }
      }
  
      // Since this is not an identifier token, it can't be macro expanded, so
      // we're done.
      ++NumFastMacroExpanded;
      return true;
    }
  
    // Start expanding the macro.
    EnterMacro(Identifier, ExpansionEnd, MI, Args);
    return false;
  }
  
  enum Bracket {
    Brace,
    Paren
  };
  
  /// CheckMatchedBrackets - Returns true if the braces and parentheses in the
  /// token vector are properly nested.
  static bool CheckMatchedBrackets(const SmallVectorImpl<Token> &Tokens) {
    SmallVector<Bracket, 8> Brackets;
    for (SmallVectorImpl<Token>::const_iterator I = Tokens.begin(),
                                                E = Tokens.end();
         I != E; ++I) {
      if (I->is(tok::l_paren)) {
        Brackets.push_back(Paren);
      } else if (I->is(tok::r_paren)) {
        if (Brackets.empty() || Brackets.back() == Brace)
          return false;
        Brackets.pop_back();
      } else if (I->is(tok::l_brace)) {
        Brackets.push_back(Brace);
      } else if (I->is(tok::r_brace)) {
        if (Brackets.empty() || Brackets.back() == Paren)
          return false;
        Brackets.pop_back();
      }
    }
    return Brackets.empty();
  }
  
  /// GenerateNewArgTokens - Returns true if OldTokens can be converted to a new
  /// vector of tokens in NewTokens.  The new number of arguments will be placed
  /// in NumArgs and the ranges which need to surrounded in parentheses will be
  /// in ParenHints.
  /// Returns false if the token stream cannot be changed.  If this is because
  /// of an initializer list starting a macro argument, the range of those
  /// initializer lists will be place in InitLists.
  static bool GenerateNewArgTokens(Preprocessor &PP,
                                   SmallVectorImpl<Token> &OldTokens,
                                   SmallVectorImpl<Token> &NewTokens,
                                   unsigned &NumArgs,
                                   SmallVectorImpl<SourceRange> &ParenHints,
                                   SmallVectorImpl<SourceRange> &InitLists) {
    if (!CheckMatchedBrackets(OldTokens))
      return false;
  
    // Once it is known that the brackets are matched, only a simple count of the
    // braces is needed.
    unsigned Braces = 0;
  
    // First token of a new macro argument.
    SmallVectorImpl<Token>::iterator ArgStartIterator = OldTokens.begin();
  
    // First closing brace in a new macro argument.  Used to generate
    // SourceRanges for InitLists.
    SmallVectorImpl<Token>::iterator ClosingBrace = OldTokens.end();
    NumArgs = 0;
    Token TempToken;
    // Set to true when a macro separator token is found inside a braced list.
    // If true, the fixed argument spans multiple old arguments and ParenHints
    // will be updated.
    bool FoundSeparatorToken = false;
    for (SmallVectorImpl<Token>::iterator I = OldTokens.begin(),
                                          E = OldTokens.end();
         I != E; ++I) {
      if (I->is(tok::l_brace)) {
        ++Braces;
      } else if (I->is(tok::r_brace)) {
        --Braces;
        if (Braces == 0 && ClosingBrace == E && FoundSeparatorToken)
          ClosingBrace = I;
      } else if (I->is(tok::eof)) {
        // EOF token is used to separate macro arguments
        if (Braces != 0) {
          // Assume comma separator is actually braced list separator and change
          // it back to a comma.
          FoundSeparatorToken = true;
          I->setKind(tok::comma);
          I->setLength(1);
        } else { // Braces == 0
          // Separator token still separates arguments.
          ++NumArgs;
  
          // If the argument starts with a brace, it can't be fixed with
          // parentheses.  A different diagnostic will be given.
          if (FoundSeparatorToken && ArgStartIterator->is(tok::l_brace)) {
            InitLists.push_back(
                SourceRange(ArgStartIterator->getLocation(),
                            PP.getLocForEndOfToken(ClosingBrace->getLocation())));
            ClosingBrace = E;
          }
  
          // Add left paren
          if (FoundSeparatorToken) {
            TempToken.startToken();
            TempToken.setKind(tok::l_paren);
            TempToken.setLocation(ArgStartIterator->getLocation());
            TempToken.setLength(0);
            NewTokens.push_back(TempToken);
          }
  
          // Copy over argument tokens
          NewTokens.insert(NewTokens.end(), ArgStartIterator, I);
  
          // Add right paren and store the paren locations in ParenHints
          if (FoundSeparatorToken) {
            SourceLocation Loc = PP.getLocForEndOfToken((I - 1)->getLocation());
            TempToken.startToken();
            TempToken.setKind(tok::r_paren);
            TempToken.setLocation(Loc);
            TempToken.setLength(0);
            NewTokens.push_back(TempToken);
            ParenHints.push_back(SourceRange(ArgStartIterator->getLocation(),
                                             Loc));
          }
  
          // Copy separator token
          NewTokens.push_back(*I);
  
          // Reset values
          ArgStartIterator = I + 1;
          FoundSeparatorToken = false;
        }
      }
    }
  
    return !ParenHints.empty() && InitLists.empty();
  }
  
  /// ReadFunctionLikeMacroArgs - After reading "MACRO" and knowing that the next
  /// token is the '(' of the macro, this method is invoked to read all of the
  /// actual arguments specified for the macro invocation.  This returns null on
  /// error.
  MacroArgs *Preprocessor::ReadMacroCallArgumentList(Token &MacroName,
                                                     MacroInfo *MI,
                                                     SourceLocation &MacroEnd) {
    // The number of fixed arguments to parse.
    unsigned NumFixedArgsLeft = MI->getNumParams();
    bool isVariadic = MI->isVariadic();
  
    // Outer loop, while there are more arguments, keep reading them.
    Token Tok;
  
    // Read arguments as unexpanded tokens.  This avoids issues, e.g., where
    // an argument value in a macro could expand to ',' or '(' or ')'.
    LexUnexpandedToken(Tok);
    assert(Tok.is(tok::l_paren) && "Error computing l-paren-ness?");
  
    // ArgTokens - Build up a list of tokens that make up each argument.  Each
    // argument is separated by an EOF token.  Use a SmallVector so we can avoid
    // heap allocations in the common case.
    SmallVector<Token, 64> ArgTokens;
    bool ContainsCodeCompletionTok = false;
    bool FoundElidedComma = false;
  
    SourceLocation TooManyArgsLoc;
  
    unsigned NumActuals = 0;
    while (Tok.isNot(tok::r_paren)) {
      if (ContainsCodeCompletionTok && Tok.isOneOf(tok::eof, tok::eod))
        break;
  
      assert(Tok.isOneOf(tok::l_paren, tok::comma) &&
             "only expect argument separators here");
  
      size_t ArgTokenStart = ArgTokens.size();
      SourceLocation ArgStartLoc = Tok.getLocation();
  
      // C99 6.10.3p11: Keep track of the number of l_parens we have seen.  Note
      // that we already consumed the first one.
      unsigned NumParens = 0;
  
      while (true) {
        // Read arguments as unexpanded tokens.  This avoids issues, e.g., where
        // an argument value in a macro could expand to ',' or '(' or ')'.
        LexUnexpandedToken(Tok);
  
        if (Tok.isOneOf(tok::eof, tok::eod)) { // "#if f(<eof>" & "#if f(\n"
          if (!ContainsCodeCompletionTok) {
            Diag(MacroName, diag::err_unterm_macro_invoc);
            Diag(MI->getDefinitionLoc(), diag::note_macro_here)
              << MacroName.getIdentifierInfo();
            // Do not lose the EOF/EOD.  Return it to the client.
            MacroName = Tok;
            return nullptr;
          }
          // Do not lose the EOF/EOD.
          auto Toks = std::make_unique<Token[]>(1);
          Toks[0] = Tok;
          EnterTokenStream(std::move(Toks), 1, true, /*IsReinject*/ false);
          break;
        } else if (Tok.is(tok::r_paren)) {
          // If we found the ) token, the macro arg list is done.
          if (NumParens-- == 0) {
            MacroEnd = Tok.getLocation();
            if (!ArgTokens.empty() &&
                ArgTokens.back().commaAfterElided()) {
              FoundElidedComma = true;
            }
            break;
          }
        } else if (Tok.is(tok::l_paren)) {
          ++NumParens;
        } else if (Tok.is(tok::comma)) {
          // In Microsoft-compatibility mode, single commas from nested macro
          // expansions should not be considered as argument separators. We test
          // for this with the IgnoredComma token flag.
          if (Tok.getFlags() & Token::IgnoredComma) {
            // However, in MSVC's preprocessor, subsequent expansions do treat
            // these commas as argument separators. This leads to a common
            // workaround used in macros that need to work in both MSVC and
            // compliant preprocessors. Therefore, the IgnoredComma flag can only
            // apply once to any given token.
            Tok.clearFlag(Token::IgnoredComma);
          } else if (NumParens == 0) {
            // Comma ends this argument if there are more fixed arguments
            // expected. However, if this is a variadic macro, and this is part of
            // the variadic part, then the comma is just an argument token.
            if (!isVariadic)
              break;
            if (NumFixedArgsLeft > 1)
              break;
          }
        } else if (Tok.is(tok::comment) && !KeepMacroComments) {
          // If this is a comment token in the argument list and we're just in
          // -C mode (not -CC mode), discard the comment.
          continue;
        } else if (!Tok.isAnnotation() && Tok.getIdentifierInfo() != nullptr) {
          // Reading macro arguments can cause macros that we are currently
          // expanding from to be popped off the expansion stack.  Doing so causes
          // them to be reenabled for expansion.  Here we record whether any
          // identifiers we lex as macro arguments correspond to disabled macros.
          // If so, we mark the token as noexpand.  This is a subtle aspect of
          // C99 6.10.3.4p2.
          if (MacroInfo *MI = getMacroInfo(Tok.getIdentifierInfo()))
            if (!MI->isEnabled())
              Tok.setFlag(Token::DisableExpand);
        } else if (Tok.is(tok::code_completion)) {
          ContainsCodeCompletionTok = true;
          if (CodeComplete)
            CodeComplete->CodeCompleteMacroArgument(MacroName.getIdentifierInfo(),
                                                    MI, NumActuals);
          // Don't mark that we reached the code-completion point because the
          // parser is going to handle the token and there will be another
          // code-completion callback.
        }
  
        ArgTokens.push_back(Tok);
      }
  
      // If this was an empty argument list foo(), don't add this as an empty
      // argument.
      if (ArgTokens.empty() && Tok.getKind() == tok::r_paren)
        break;
  
      // If this is not a variadic macro, and too many args were specified, emit
      // an error.
      if (!isVariadic && NumFixedArgsLeft == 0 && TooManyArgsLoc.isInvalid()) {
        if (ArgTokens.size() != ArgTokenStart)
          TooManyArgsLoc = ArgTokens[ArgTokenStart].getLocation();
        else
          TooManyArgsLoc = ArgStartLoc;
      }
  
      // Empty arguments are standard in C99 and C++0x, and are supported as an
      // extension in other modes.
      if (ArgTokens.size() == ArgTokenStart && !getLangOpts().C99)
        Diag(Tok, getLangOpts().CPlusPlus11
                      ? diag::warn_cxx98_compat_empty_fnmacro_arg
                      : diag::ext_empty_fnmacro_arg);
  
      // Add a marker EOF token to the end of the token list for this argument.
      Token EOFTok;
      EOFTok.startToken();
      EOFTok.setKind(tok::eof);
      EOFTok.setLocation(Tok.getLocation());
      EOFTok.setLength(0);
      ArgTokens.push_back(EOFTok);
      ++NumActuals;
      if (!ContainsCodeCompletionTok && NumFixedArgsLeft != 0)
        --NumFixedArgsLeft;
    }
  
    // Okay, we either found the r_paren.  Check to see if we parsed too few
    // arguments.
    unsigned MinArgsExpected = MI->getNumParams();
  
    // If this is not a variadic macro, and too many args were specified, emit
    // an error.
    if (!isVariadic && NumActuals > MinArgsExpected &&
        !ContainsCodeCompletionTok) {
      // Emit the diagnostic at the macro name in case there is a missing ).
      // Emitting it at the , could be far away from the macro name.
      Diag(TooManyArgsLoc, diag::err_too_many_args_in_macro_invoc);
      Diag(MI->getDefinitionLoc(), diag::note_macro_here)
        << MacroName.getIdentifierInfo();
  
      // Commas from braced initializer lists will be treated as argument
      // separators inside macros.  Attempt to correct for this with parentheses.
      // TODO: See if this can be generalized to angle brackets for templates
      // inside macro arguments.
  
      SmallVector<Token, 4> FixedArgTokens;
      unsigned FixedNumArgs = 0;
      SmallVector<SourceRange, 4> ParenHints, InitLists;
      if (!GenerateNewArgTokens(*this, ArgTokens, FixedArgTokens, FixedNumArgs,
                                ParenHints, InitLists)) {
        if (!InitLists.empty()) {
          DiagnosticBuilder DB =
              Diag(MacroName,
                   diag::note_init_list_at_beginning_of_macro_argument);
          for (SourceRange Range : InitLists)
            DB << Range;
        }
        return nullptr;
      }
      if (FixedNumArgs != MinArgsExpected)
        return nullptr;
  
      DiagnosticBuilder DB = Diag(MacroName, diag::note_suggest_parens_for_macro);
      for (SourceRange ParenLocation : ParenHints) {
        DB << FixItHint::CreateInsertion(ParenLocation.getBegin(), "(");
        DB << FixItHint::CreateInsertion(ParenLocation.getEnd(), ")");
      }
      ArgTokens.swap(FixedArgTokens);
      NumActuals = FixedNumArgs;
    }
  
    // See MacroArgs instance var for description of this.
    bool isVarargsElided = false;
  
    if (ContainsCodeCompletionTok) {
      // Recover from not-fully-formed macro invocation during code-completion.
      Token EOFTok;
      EOFTok.startToken();
      EOFTok.setKind(tok::eof);
      EOFTok.setLocation(Tok.getLocation());
      EOFTok.setLength(0);
      for (; NumActuals < MinArgsExpected; ++NumActuals)
        ArgTokens.push_back(EOFTok);
    }
  
    if (NumActuals < MinArgsExpected) {
      // There are several cases where too few arguments is ok, handle them now.
      if (NumActuals == 0 && MinArgsExpected == 1) {
        // #define A(X)  or  #define A(...)   ---> A()
  
        // If there is exactly one argument, and that argument is missing,
        // then we have an empty "()" argument empty list.  This is fine, even if
        // the macro expects one argument (the argument is just empty).
        isVarargsElided = MI->isVariadic();
      } else if ((FoundElidedComma || MI->isVariadic()) &&
                 (NumActuals+1 == MinArgsExpected ||  // A(x, ...) -> A(X)
                  (NumActuals == 0 && MinArgsExpected == 2))) {// A(x,...) -> A()
        // Varargs where the named vararg parameter is missing: OK as extension.
        //   #define A(x, ...)
        //   A("blah")
        //
        // If the macro contains the comma pasting extension, the diagnostic
        // is suppressed; we know we'll get another diagnostic later.
        if (!MI->hasCommaPasting()) {
          // C++20 allows this construct, but standards before C++20 and all C
          // standards do not allow the construct (we allow it as an extension).
          Diag(Tok, getLangOpts().CPlusPlus20
                        ? diag::warn_cxx17_compat_missing_varargs_arg
                        : diag::ext_missing_varargs_arg);
          Diag(MI->getDefinitionLoc(), diag::note_macro_here)
            << MacroName.getIdentifierInfo();
        }
  
        // Remember this occurred, allowing us to elide the comma when used for
        // cases like:
        //   #define A(x, foo...) blah(a, ## foo)
        //   #define B(x, ...) blah(a, ## __VA_ARGS__)
        //   #define C(...) blah(a, ## __VA_ARGS__)
        //  A(x) B(x) C()
        isVarargsElided = true;
      } else if (!ContainsCodeCompletionTok) {
        // Otherwise, emit the error.
        Diag(Tok, diag::err_too_few_args_in_macro_invoc);
        Diag(MI->getDefinitionLoc(), diag::note_macro_here)
          << MacroName.getIdentifierInfo();
        return nullptr;
      }
  
      // Add a marker EOF token to the end of the token list for this argument.
      SourceLocation EndLoc = Tok.getLocation();
      Tok.startToken();
      Tok.setKind(tok::eof);
      Tok.setLocation(EndLoc);
      Tok.setLength(0);
      ArgTokens.push_back(Tok);
  
      // If we expect two arguments, add both as empty.
      if (NumActuals == 0 && MinArgsExpected == 2)
        ArgTokens.push_back(Tok);
  
    } else if (NumActuals > MinArgsExpected && !MI->isVariadic() &&
               !ContainsCodeCompletionTok) {
      // Emit the diagnostic at the macro name in case there is a missing ).
      // Emitting it at the , could be far away from the macro name.
      Diag(MacroName, diag::err_too_many_args_in_macro_invoc);
      Diag(MI->getDefinitionLoc(), diag::note_macro_here)
        << MacroName.getIdentifierInfo();
      return nullptr;
    }
  
    return MacroArgs::create(MI, ArgTokens, isVarargsElided, *this);
  }
  
  /// Keeps macro expanded tokens for TokenLexers.
  //
  /// Works like a stack; a TokenLexer adds the macro expanded tokens that is
  /// going to lex in the cache and when it finishes the tokens are removed
  /// from the end of the cache.
  Token *Preprocessor::cacheMacroExpandedTokens(TokenLexer *tokLexer,
                                                ArrayRef<Token> tokens) {
    assert(tokLexer);
    if (tokens.empty())
      return nullptr;
  
    size_t newIndex = MacroExpandedTokens.size();
    bool cacheNeedsToGrow = tokens.size() >
                        MacroExpandedTokens.capacity()-MacroExpandedTokens.size();
    MacroExpandedTokens.append(tokens.begin(), tokens.end());
  
    if (cacheNeedsToGrow) {
      // Go through all the TokenLexers whose 'Tokens' pointer points in the
      // buffer and update the pointers to the (potential) new buffer array.
      for (const auto &Lexer : MacroExpandingLexersStack) {
        TokenLexer *prevLexer;
        size_t tokIndex;
        std::tie(prevLexer, tokIndex) = Lexer;
        prevLexer->Tokens = MacroExpandedTokens.data() + tokIndex;
      }
    }
  
    MacroExpandingLexersStack.push_back(std::make_pair(tokLexer, newIndex));
    return MacroExpandedTokens.data() + newIndex;
  }
  
  void Preprocessor::removeCachedMacroExpandedTokensOfLastLexer() {
    assert(!MacroExpandingLexersStack.empty());
    size_t tokIndex = MacroExpandingLexersStack.back().second;
    assert(tokIndex < MacroExpandedTokens.size());
    // Pop the cached macro expanded tokens from the end.
    MacroExpandedTokens.resize(tokIndex);
    MacroExpandingLexersStack.pop_back();
  }
  
  /// ComputeDATE_TIME - Compute the current time, enter it into the specified
  /// scratch buffer, then return DATELoc/TIMELoc locations with the position of
  /// the identifier tokens inserted.
  static void ComputeDATE_TIME(SourceLocation &DATELoc, SourceLocation &TIMELoc,
                               Preprocessor &PP) {
    time_t TT = time(nullptr);
    struct tm *TM = localtime(&TT);
  
    static const char * const Months[] = {
      "Jan","Feb","Mar","Apr","May","Jun","Jul","Aug","Sep","Oct","Nov","Dec"
    };
  
    {
      SmallString<32> TmpBuffer;
      llvm::raw_svector_ostream TmpStream(TmpBuffer);
      TmpStream << llvm::format("\"%s %2d %4d\"", Months[TM->tm_mon],
                                TM->tm_mday, TM->tm_year + 1900);
      Token TmpTok;
      TmpTok.startToken();
      PP.CreateString(TmpStream.str(), TmpTok);
      DATELoc = TmpTok.getLocation();
    }
  
    {
      SmallString<32> TmpBuffer;
      llvm::raw_svector_ostream TmpStream(TmpBuffer);
      TmpStream << llvm::format("\"%02d:%02d:%02d\"",
                                TM->tm_hour, TM->tm_min, TM->tm_sec);
      Token TmpTok;
      TmpTok.startToken();
      PP.CreateString(TmpStream.str(), TmpTok);
      TIMELoc = TmpTok.getLocation();
    }
  }
  
  /// HasFeature - Return true if we recognize and implement the feature
  /// specified by the identifier as a standard language feature.
  static bool HasFeature(const Preprocessor &PP, StringRef Feature) {
    const LangOptions &LangOpts = PP.getLangOpts();
  
    // Normalize the feature name, __foo__ becomes foo.
    if (Feature.startswith("__") && Feature.endswith("__") && Feature.size() >= 4)
      Feature = Feature.substr(2, Feature.size() - 4);
  
  #define FEATURE(Name, Predicate) .Case(#Name, Predicate)
    return llvm::StringSwitch<bool>(Feature)
  #include "clang/Basic/Features.def"
        .Default(false);
  #undef FEATURE
  }
  
  /// HasExtension - Return true if we recognize and implement the feature
  /// specified by the identifier, either as an extension or a standard language
  /// feature.
  static bool HasExtension(const Preprocessor &PP, StringRef Extension) {
    if (HasFeature(PP, Extension))
      return true;
  
    // If the use of an extension results in an error diagnostic, extensions are
    // effectively unavailable, so just return false here.
    if (PP.getDiagnostics().getExtensionHandlingBehavior() >=
        diag::Severity::Error)
      return false;
  
    const LangOptions &LangOpts = PP.getLangOpts();
  
    // Normalize the extension name, __foo__ becomes foo.
    if (Extension.startswith("__") && Extension.endswith("__") &&
        Extension.size() >= 4)
      Extension = Extension.substr(2, Extension.size() - 4);
  
      // Because we inherit the feature list from HasFeature, this string switch
      // must be less restrictive than HasFeature's.
  #define EXTENSION(Name, Predicate) .Case(#Name, Predicate)
    return llvm::StringSwitch<bool>(Extension)
  #include "clang/Basic/Features.def"
        .Default(false);
  #undef EXTENSION
  }
  
  /// EvaluateHasIncludeCommon - Process a '__has_include("path")'
  /// or '__has_include_next("path")' expression.
  /// Returns true if successful.
  static bool EvaluateHasIncludeCommon(Token &Tok, IdentifierInfo *II,
                                       Preprocessor &PP,
                                       ConstSearchDirIterator LookupFrom,
                                       const FileEntry *LookupFromFile) {
    // Save the location of the current token.  If a '(' is later found, use
    // that location.  If not, use the end of this location instead.
    SourceLocation LParenLoc = Tok.getLocation();
  
    // These expressions are only allowed within a preprocessor directive.
    if (!PP.isParsingIfOrElifDirective()) {
      PP.Diag(LParenLoc, diag::err_pp_directive_required) << II;
      // Return a valid identifier token.
      assert(Tok.is(tok::identifier));
      Tok.setIdentifierInfo(II);
      return false;
    }
  
    // Get '('. If we don't have a '(', try to form a header-name token.
    do {
      if (PP.LexHeaderName(Tok))
        return false;
    } while (Tok.getKind() == tok::comment);
  
    // Ensure we have a '('.
    if (Tok.isNot(tok::l_paren)) {
      // No '(', use end of last token.
      LParenLoc = PP.getLocForEndOfToken(LParenLoc);
      PP.Diag(LParenLoc, diag::err_pp_expected_after) << II << tok::l_paren;
      // If the next token looks like a filename or the start of one,
      // assume it is and process it as such.
      if (Tok.isNot(tok::header_name))
        return false;
    } else {
      // Save '(' location for possible missing ')' message.
      LParenLoc = Tok.getLocation();
      if (PP.LexHeaderName(Tok))
        return false;
    }
  
    if (Tok.isNot(tok::header_name)) {
      PP.Diag(Tok.getLocation(), diag::err_pp_expects_filename);
      return false;
    }
  
    // Reserve a buffer to get the spelling.
    SmallString<128> FilenameBuffer;
    bool Invalid = false;
    StringRef Filename = PP.getSpelling(Tok, FilenameBuffer, &Invalid);
    if (Invalid)
      return false;
  
    SourceLocation FilenameLoc = Tok.getLocation();
  
    // Get ')'.
    PP.LexNonComment(Tok);
  
    // Ensure we have a trailing ).
    if (Tok.isNot(tok::r_paren)) {
      PP.Diag(PP.getLocForEndOfToken(FilenameLoc), diag::err_pp_expected_after)
          << II << tok::r_paren;
      PP.Diag(LParenLoc, diag::note_matching) << tok::l_paren;
      return false;
    }
  
    bool isAngled = PP.GetIncludeFilenameSpelling(Tok.getLocation(), Filename);
    // If GetIncludeFilenameSpelling set the start ptr to null, there was an
    // error.
    if (Filename.empty())
      return false;
  
    // Search include directories.
    Optional<FileEntryRef> File =
        PP.LookupFile(FilenameLoc, Filename, isAngled, LookupFrom, LookupFromFile,
                      nullptr, nullptr, nullptr, nullptr, nullptr, nullptr);
  
    if (PPCallbacks *Callbacks = PP.getPPCallbacks()) {
      SrcMgr::CharacteristicKind FileType = SrcMgr::C_User;
      if (File)
        FileType =
            PP.getHeaderSearchInfo().getFileDirFlavor(&File->getFileEntry());
      Callbacks->HasInclude(FilenameLoc, Filename, isAngled, File, FileType);
    }
  
    // Get the result value.  A result of true means the file exists.
    return File.hasValue();
  }
  
  bool Preprocessor::EvaluateHasInclude(Token &Tok, IdentifierInfo *II) {
    return EvaluateHasIncludeCommon(Tok, II, *this, nullptr, nullptr);
  }
  
  bool Preprocessor::EvaluateHasIncludeNext(Token &Tok, IdentifierInfo *II) {
    ConstSearchDirIterator Lookup = nullptr;
    const FileEntry *LookupFromFile;
    std::tie(Lookup, LookupFromFile) = getIncludeNextStart(Tok);
  
    return EvaluateHasIncludeCommon(Tok, II, *this, Lookup, LookupFromFile);
  }
  
  /// Process single-argument builtin feature-like macros that return
  /// integer values.
  static void EvaluateFeatureLikeBuiltinMacro(llvm::raw_svector_ostream& OS,
                                              Token &Tok, IdentifierInfo *II,
                                              Preprocessor &PP, bool ExpandArgs,
                                              llvm::function_ref<
                                                int(Token &Tok,
                                                    bool &HasLexedNextTok)> Op) {
    // Parse the initial '('.
    PP.LexUnexpandedToken(Tok);
    if (Tok.isNot(tok::l_paren)) {
      PP.Diag(Tok.getLocation(), diag::err_pp_expected_after) << II
                                                              << tok::l_paren;
  
      // Provide a dummy '0' value on output stream to elide further errors.
      if (!Tok.isOneOf(tok::eof, tok::eod)) {
        OS << 0;
        Tok.setKind(tok::numeric_constant);
      }
      return;
    }
  
    unsigned ParenDepth = 1;
    SourceLocation LParenLoc = Tok.getLocation();
    llvm::Optional<int> Result;
  
    Token ResultTok;
    bool SuppressDiagnostic = false;
    while (true) {
      // Parse next token.
      if (ExpandArgs)
        PP.Lex(Tok);
      else
        PP.LexUnexpandedToken(Tok);
  
  already_lexed:
      switch (Tok.getKind()) {
        case tok::eof:
        case tok::eod:
          // Don't provide even a dummy value if the eod or eof marker is
          // reached.  Simply provide a diagnostic.
          PP.Diag(Tok.getLocation(), diag::err_unterm_macro_invoc);
          return;
  
        case tok::comma:
          if (!SuppressDiagnostic) {
            PP.Diag(Tok.getLocation(), diag::err_too_many_args_in_macro_invoc);
            SuppressDiagnostic = true;
          }
          continue;
  
        case tok::l_paren:
          ++ParenDepth;
          if (Result.hasValue())
            break;
          if (!SuppressDiagnostic) {
            PP.Diag(Tok.getLocation(), diag::err_pp_nested_paren) << II;
            SuppressDiagnostic = true;
          }
          continue;
  
        case tok::r_paren:
          if (--ParenDepth > 0)
            continue;
  
          // The last ')' has been reached; return the value if one found or
          // a diagnostic and a dummy value.
          if (Result.hasValue()) {
            OS << Result.getValue();
            // For strict conformance to __has_cpp_attribute rules, use 'L'
            // suffix for dated literals.
            if (Result.getValue() > 1)
              OS << 'L';
          } else {
            OS << 0;
            if (!SuppressDiagnostic)
              PP.Diag(Tok.getLocation(), diag::err_too_few_args_in_macro_invoc);
          }
          Tok.setKind(tok::numeric_constant);
          return;
  
        default: {
          // Parse the macro argument, if one not found so far.
          if (Result.hasValue())
            break;
  
          bool HasLexedNextToken = false;
          Result = Op(Tok, HasLexedNextToken);
          ResultTok = Tok;
          if (HasLexedNextToken)
            goto already_lexed;
          continue;
        }
      }
  
      // Diagnose missing ')'.
      if (!SuppressDiagnostic) {
        if (auto Diag = PP.Diag(Tok.getLocation(), diag::err_pp_expected_after)) {
          if (IdentifierInfo *LastII = ResultTok.getIdentifierInfo())
            Diag << LastII;
          else
            Diag << ResultTok.getKind();
          Diag << tok::r_paren << ResultTok.getLocation();
        }
        PP.Diag(LParenLoc, diag::note_matching) << tok::l_paren;
        SuppressDiagnostic = true;
      }
    }
  }
  
  /// Helper function to return the IdentifierInfo structure of a Token
  /// or generate a diagnostic if none available.
  static IdentifierInfo *ExpectFeatureIdentifierInfo(Token &Tok,
                                                     Preprocessor &PP,
                                                     signed DiagID) {
    IdentifierInfo *II;
    if (!Tok.isAnnotation() && (II = Tok.getIdentifierInfo()))
      return II;
  
    PP.Diag(Tok.getLocation(), DiagID);
    return nullptr;
  }
  
  /// Implements the __is_target_arch builtin macro.
  static bool isTargetArch(const TargetInfo &TI, const IdentifierInfo *II) {
    std::string ArchName = II->getName().lower() + "--";
    llvm::Triple Arch(ArchName);
    const llvm::Triple &TT = TI.getTriple();
    if (TT.isThumb()) {
      // arm matches thumb or thumbv7. armv7 matches thumbv7.
      if ((Arch.getSubArch() == llvm::Triple::NoSubArch ||
           Arch.getSubArch() == TT.getSubArch()) &&
          ((TT.getArch() == llvm::Triple::thumb &&
            Arch.getArch() == llvm::Triple::arm) ||
           (TT.getArch() == llvm::Triple::thumbeb &&
            Arch.getArch() == llvm::Triple::armeb)))
        return true;
    }
    // Check the parsed arch when it has no sub arch to allow Clang to
    // match thumb to thumbv7 but to prohibit matching thumbv6 to thumbv7.
    return (Arch.getSubArch() == llvm::Triple::NoSubArch ||
            Arch.getSubArch() == TT.getSubArch()) &&
           Arch.getArch() == TT.getArch();
  }
  
  /// Implements the __is_target_vendor builtin macro.
  static bool isTargetVendor(const TargetInfo &TI, const IdentifierInfo *II) {
    StringRef VendorName = TI.getTriple().getVendorName();
    if (VendorName.empty())
      VendorName = "unknown";
    return VendorName.equals_insensitive(II->getName());
  }
  
  /// Implements the __is_target_os builtin macro.
  static bool isTargetOS(const TargetInfo &TI, const IdentifierInfo *II) {
    std::string OSName =
        (llvm::Twine("unknown-unknown-") + II->getName().lower()).str();
    llvm::Triple OS(OSName);
    if (OS.getOS() == llvm::Triple::Darwin) {
      // Darwin matches macos, ios, etc.
      return TI.getTriple().isOSDarwin();
    }
    return TI.getTriple().getOS() == OS.getOS();
  }
  
  /// Implements the __is_target_environment builtin macro.
  static bool isTargetEnvironment(const TargetInfo &TI,
                                  const IdentifierInfo *II) {
    std::string EnvName = (llvm::Twine("---") + II->getName().lower()).str();
    llvm::Triple Env(EnvName);
    return TI.getTriple().getEnvironment() == Env.getEnvironment();
  }
  
  /// ExpandBuiltinMacro - If an identifier token is read that is to be expanded
  /// as a builtin macro, handle it and return the next token as 'Tok'.
  void Preprocessor::ExpandBuiltinMacro(Token &Tok) {
    // Figure out which token this is.
    IdentifierInfo *II = Tok.getIdentifierInfo();
    assert(II && "Can't be a macro without id info!");
  
    // If this is an _Pragma or Microsoft __pragma directive, expand it,
    // invoke the pragma handler, then lex the token after it.
    if (II == Ident_Pragma)
      return Handle_Pragma(Tok);
    else if (II == Ident__pragma) // in non-MS mode this is null
      return HandleMicrosoft__pragma(Tok);
  
    ++NumBuiltinMacroExpanded;
  
    SmallString<128> TmpBuffer;
    llvm::raw_svector_ostream OS(TmpBuffer);
  
    // Set up the return result.
    Tok.setIdentifierInfo(nullptr);
    Tok.clearFlag(Token::NeedsCleaning);
    bool IsAtStartOfLine = Tok.isAtStartOfLine();
    bool HasLeadingSpace = Tok.hasLeadingSpace();
  
    if (II == Ident__LINE__) {
      // C99 6.10.8: "__LINE__: The presumed line number (within the current
      // source file) of the current source line (an integer constant)".  This can
      // be affected by #line.
      SourceLocation Loc = Tok.getLocation();
  
      // Advance to the location of the first _, this might not be the first byte
      // of the token if it starts with an escaped newline.
      Loc = AdvanceToTokenCharacter(Loc, 0);
  
      // One wrinkle here is that GCC expands __LINE__ to location of the *end* of
      // a macro expansion.  This doesn't matter for object-like macros, but
      // can matter for a function-like macro that expands to contain __LINE__.
      // Skip down through expansion points until we find a file loc for the
      // end of the expansion history.
      Loc = SourceMgr.getExpansionRange(Loc).getEnd();
      PresumedLoc PLoc = SourceMgr.getPresumedLoc(Loc);
  
      // __LINE__ expands to a simple numeric value.
      OS << (PLoc.isValid()? PLoc.getLine() : 1);
      Tok.setKind(tok::numeric_constant);
    } else if (II == Ident__FILE__ || II == Ident__BASE_FILE__ ||
               II == Ident__FILE_NAME__) {
      // C99 6.10.8: "__FILE__: The presumed name of the current source file (a
      // character string literal)". This can be affected by #line.
      PresumedLoc PLoc = SourceMgr.getPresumedLoc(Tok.getLocation());
  
      // __BASE_FILE__ is a GNU extension that returns the top of the presumed
      // #include stack instead of the current file.
      if (II == Ident__BASE_FILE__ && PLoc.isValid()) {
        SourceLocation NextLoc = PLoc.getIncludeLoc();
        while (NextLoc.isValid()) {
          PLoc = SourceMgr.getPresumedLoc(NextLoc);
          if (PLoc.isInvalid())
            break;
  
          NextLoc = PLoc.getIncludeLoc();
        }
      }
  
      // Escape this filename.  Turn '\' -> '\\' '"' -> '\"'
      SmallString<256> FN;
      if (PLoc.isValid()) {
        // __FILE_NAME__ is a Clang-specific extension that expands to the
        // the last part of __FILE__.
        if (II == Ident__FILE_NAME__) {
          // Try to get the last path component, failing that return the original
          // presumed location.
          StringRef PLFileName = llvm::sys::path::filename(PLoc.getFilename());
          if (PLFileName != "")
            FN += PLFileName;
          else
            FN += PLoc.getFilename();
        } else {
          FN += PLoc.getFilename();
        }
        getLangOpts().remapPathPrefix(FN);
        Lexer::Stringify(FN);
        OS << '"' << FN << '"';
      }
      Tok.setKind(tok::string_literal);
    } else if (II == Ident__DATE__) {
      Diag(Tok.getLocation(), diag::warn_pp_date_time);
      if (!DATELoc.isValid())
        ComputeDATE_TIME(DATELoc, TIMELoc, *this);
      Tok.setKind(tok::string_literal);
      Tok.setLength(strlen("\"Mmm dd yyyy\""));
      Tok.setLocation(SourceMgr.createExpansionLoc(DATELoc, Tok.getLocation(),
                                                   Tok.getLocation(),
                                                   Tok.getLength()));
      return;
    } else if (II == Ident__TIME__) {
      Diag(Tok.getLocation(), diag::warn_pp_date_time);
      if (!TIMELoc.isValid())
        ComputeDATE_TIME(DATELoc, TIMELoc, *this);
      Tok.setKind(tok::string_literal);
      Tok.setLength(strlen("\"hh:mm:ss\""));
      Tok.setLocation(SourceMgr.createExpansionLoc(TIMELoc, Tok.getLocation(),
                                                   Tok.getLocation(),
                                                   Tok.getLength()));
      return;
    } else if (II == Ident__INCLUDE_LEVEL__) {
      // Compute the presumed include depth of this token.  This can be affected
      // by GNU line markers.
      unsigned Depth = 0;
  
      PresumedLoc PLoc = SourceMgr.getPresumedLoc(Tok.getLocation());
      if (PLoc.isValid()) {
        PLoc = SourceMgr.getPresumedLoc(PLoc.getIncludeLoc());
        for (; PLoc.isValid(); ++Depth)
          PLoc = SourceMgr.getPresumedLoc(PLoc.getIncludeLoc());
      }
  
      // __INCLUDE_LEVEL__ expands to a simple numeric value.
      OS << Depth;
      Tok.setKind(tok::numeric_constant);
    } else if (II == Ident__TIMESTAMP__) {
      Diag(Tok.getLocation(), diag::warn_pp_date_time);
      // MSVC, ICC, GCC, VisualAge C++ extension.  The generated string should be
      // of the form "Ddd Mmm dd hh::mm::ss yyyy", which is returned by asctime.
  
      // Get the file that we are lexing out of.  If we're currently lexing from
      // a macro, dig into the include stack.
      const FileEntry *CurFile = nullptr;
      PreprocessorLexer *TheLexer = getCurrentFileLexer();
  
      if (TheLexer)
        CurFile = SourceMgr.getFileEntryForID(TheLexer->getFileID());
  
      const char *Result;
      if (CurFile) {
        time_t TT = CurFile->getModificationTime();
        struct tm *TM = localtime(&TT);
        Result = asctime(TM);
      } else {
        Result = "??? ??? ?? ??:??:?? ????\n";
      }
      // Surround the string with " and strip the trailing newline.
      OS << '"' << StringRef(Result).drop_back() << '"';
      Tok.setKind(tok::string_literal);
    } else if (II == Ident__FLT_EVAL_METHOD__) {
      // __FLT_EVAL_METHOD__ is set to the default value.
      OS << getTUFPEvalMethod();
      // __FLT_EVAL_METHOD__ expands to a simple numeric value.
      Tok.setKind(tok::numeric_constant);
      if (getLastFPEvalPragmaLocation().isValid()) {
        // The program is ill-formed. The value of __FLT_EVAL_METHOD__ is altered
        // by the pragma.
        Diag(Tok, diag::err_illegal_use_of_flt_eval_macro);
        Diag(getLastFPEvalPragmaLocation(), diag::note_pragma_entered_here);
      }
    } else if (II == Ident__COUNTER__) {
      // __COUNTER__ expands to a simple numeric value.
      OS << CounterValue++;
      Tok.setKind(tok::numeric_constant);
    } else if (II == Ident__has_feature) {
      EvaluateFeatureLikeBuiltinMacro(OS, Tok, II, *this, false,
        [this](Token &Tok, bool &HasLexedNextToken) -> int {
          IdentifierInfo *II = ExpectFeatureIdentifierInfo(Tok, *this,
                                             diag::err_feature_check_malformed);
          return II && HasFeature(*this, II->getName());
        });
    } else if (II == Ident__has_extension) {
      EvaluateFeatureLikeBuiltinMacro(OS, Tok, II, *this, false,
        [this](Token &Tok, bool &HasLexedNextToken) -> int {
          IdentifierInfo *II = ExpectFeatureIdentifierInfo(Tok, *this,
                                             diag::err_feature_check_malformed);
          return II && HasExtension(*this, II->getName());
        });
    } else if (II == Ident__has_builtin) {
      EvaluateFeatureLikeBuiltinMacro(OS, Tok, II, *this, false,
        [this](Token &Tok, bool &HasLexedNextToken) -> int {
          IdentifierInfo *II = ExpectFeatureIdentifierInfo(Tok, *this,
                                             diag::err_feature_check_malformed);
          if (!II)
            return false;
          else if (II->getBuiltinID() != 0) {
            switch (II->getBuiltinID()) {
            case Builtin::BI__builtin_operator_new:
            case Builtin::BI__builtin_operator_delete:
              // denotes date of behavior change to support calling arbitrary
              // usual allocation and deallocation functions. Required by libc++
              return 201802;
            default:
              return true;
            }
            return true;
          } else if (II->getTokenID() != tok::identifier ||
                     II->hasRevertedTokenIDToIdentifier()) {
            // Treat all keywords that introduce a custom syntax of the form
            //
            //   '__some_keyword' '(' [...] ')'
            //
            // as being "builtin functions", even if the syntax isn't a valid
            // function call (for example, because the builtin takes a type
            // argument).
            if (II->getName().startswith("__builtin_") ||
                II->getName().startswith("__is_") ||
                II->getName().startswith("__has_"))
              return true;
            return llvm::StringSwitch<bool>(II->getName())
                .Case("__array_rank", true)
                .Case("__array_extent", true)
                .Case("__reference_binds_to_temporary", true)
                .Case("__underlying_type", true)
                .Default(false);
          } else {
            return llvm::StringSwitch<bool>(II->getName())
                // Report builtin templates as being builtins.
                .Case("__make_integer_seq", getLangOpts().CPlusPlus)
                .Case("__type_pack_element", getLangOpts().CPlusPlus)
                // Likewise for some builtin preprocessor macros.
                // FIXME: This is inconsistent; we usually suggest detecting
                // builtin macros via #ifdef. Don't add more cases here.
                .Case("__is_target_arch", true)
                .Case("__is_target_vendor", true)
                .Case("__is_target_os", true)
                .Case("__is_target_environment", true)
                .Default(false);
          }
        });
    } else if (II == Ident__is_identifier) {
      EvaluateFeatureLikeBuiltinMacro(OS, Tok, II, *this, false,
        [](Token &Tok, bool &HasLexedNextToken) -> int {
          return Tok.is(tok::identifier);
        });
    } else if (II == Ident__has_attribute) {
      EvaluateFeatureLikeBuiltinMacro(OS, Tok, II, *this, true,
        [this](Token &Tok, bool &HasLexedNextToken) -> int {
          IdentifierInfo *II = ExpectFeatureIdentifierInfo(Tok, *this,
                                             diag::err_feature_check_malformed);
          return II ? hasAttribute(AttrSyntax::GNU, nullptr, II,
                                   getTargetInfo(), getLangOpts()) : 0;
        });
    } else if (II == Ident__has_declspec) {
      EvaluateFeatureLikeBuiltinMacro(OS, Tok, II, *this, true,
        [this](Token &Tok, bool &HasLexedNextToken) -> int {
          IdentifierInfo *II = ExpectFeatureIdentifierInfo(Tok, *this,
                                             diag::err_feature_check_malformed);
          if (II) {
            const LangOptions &LangOpts = getLangOpts();
            return LangOpts.DeclSpecKeyword &&
                   hasAttribute(AttrSyntax::Declspec, nullptr, II,
                                getTargetInfo(), LangOpts);
          }
  
          return false;
        });
    } else if (II == Ident__has_cpp_attribute ||
               II == Ident__has_c_attribute) {
      bool IsCXX = II == Ident__has_cpp_attribute;
      EvaluateFeatureLikeBuiltinMacro(OS, Tok, II, *this, true,
          [&](Token &Tok, bool &HasLexedNextToken) -> int {
            IdentifierInfo *ScopeII = nullptr;
            IdentifierInfo *II = ExpectFeatureIdentifierInfo(
                Tok, *this, diag::err_feature_check_malformed);
            if (!II)
              return false;
  
            // It is possible to receive a scope token.  Read the "::", if it is
            // available, and the subsequent identifier.
            LexUnexpandedToken(Tok);
            if (Tok.isNot(tok::coloncolon))
              HasLexedNextToken = true;
            else {
              ScopeII = II;
              // Lex an expanded token for the attribute name.
              Lex(Tok);
              II = ExpectFeatureIdentifierInfo(Tok, *this,
                                               diag::err_feature_check_malformed);
            }
  
            AttrSyntax Syntax = IsCXX ? AttrSyntax::CXX : AttrSyntax::C;
            return II ? hasAttribute(Syntax, ScopeII, II, getTargetInfo(),
                                     getLangOpts())
                      : 0;
          });
    } else if (II == Ident__has_include ||
               II == Ident__has_include_next) {
      // The argument to these two builtins should be a parenthesized
      // file name string literal using angle brackets (<>) or
      // double-quotes ("").
      bool Value;
      if (II == Ident__has_include)
        Value = EvaluateHasInclude(Tok, II);
      else
        Value = EvaluateHasIncludeNext(Tok, II);
  
      if (Tok.isNot(tok::r_paren))
        return;
      OS << (int)Value;
      Tok.setKind(tok::numeric_constant);
    } else if (II == Ident__has_warning) {
      // The argument should be a parenthesized string literal.
      EvaluateFeatureLikeBuiltinMacro(OS, Tok, II, *this, false,
        [this](Token &Tok, bool &HasLexedNextToken) -> int {
          std::string WarningName;
          SourceLocation StrStartLoc = Tok.getLocation();
  
          HasLexedNextToken = Tok.is(tok::string_literal);
          if (!FinishLexStringLiteral(Tok, WarningName, "'__has_warning'",
                                      /*AllowMacroExpansion=*/false))
            return false;
  
          // FIXME: Should we accept "-R..." flags here, or should that be
          // handled by a separate __has_remark?
          if (WarningName.size() < 3 || WarningName[0] != '-' ||
              WarningName[1] != 'W') {
            Diag(StrStartLoc, diag::warn_has_warning_invalid_option);
            return false;
          }
  
          // Finally, check if the warning flags maps to a diagnostic group.
          // We construct a SmallVector here to talk to getDiagnosticIDs().
          // Although we don't use the result, this isn't a hot path, and not
          // worth special casing.
          SmallVector<diag::kind, 10> Diags;
          return !getDiagnostics().getDiagnosticIDs()->
                  getDiagnosticsInGroup(diag::Flavor::WarningOrError,
                                        WarningName.substr(2), Diags);
        });
    } else if (II == Ident__building_module) {
      // The argument to this builtin should be an identifier. The
      // builtin evaluates to 1 when that identifier names the module we are
      // currently building.
      EvaluateFeatureLikeBuiltinMacro(OS, Tok, II, *this, false,
        [this](Token &Tok, bool &HasLexedNextToken) -> int {
          IdentifierInfo *II = ExpectFeatureIdentifierInfo(Tok, *this,
                                         diag::err_expected_id_building_module);
          return getLangOpts().isCompilingModule() && II &&
                 (II->getName() == getLangOpts().CurrentModule);
        });
    } else if (II == Ident__MODULE__) {
      // The current module as an identifier.
      OS << getLangOpts().CurrentModule;
      IdentifierInfo *ModuleII = getIdentifierInfo(getLangOpts().CurrentModule);
      Tok.setIdentifierInfo(ModuleII);
      Tok.setKind(ModuleII->getTokenID());
    } else if (II == Ident__identifier) {
      SourceLocation Loc = Tok.getLocation();
  
      // We're expecting '__identifier' '(' identifier ')'. Try to recover
      // if the parens are missing.
      LexNonComment(Tok);
      if (Tok.isNot(tok::l_paren)) {
        // No '(', use end of last token.
        Diag(getLocForEndOfToken(Loc), diag::err_pp_expected_after)
          << II << tok::l_paren;
        // If the next token isn't valid as our argument, we can't recover.
        if (!Tok.isAnnotation() && Tok.getIdentifierInfo())
          Tok.setKind(tok::identifier);
        return;
      }
  
      SourceLocation LParenLoc = Tok.getLocation();
      LexNonComment(Tok);
  
      if (!Tok.isAnnotation() && Tok.getIdentifierInfo())
        Tok.setKind(tok::identifier);
      else if (Tok.is(tok::string_literal) && !Tok.hasUDSuffix()) {
        StringLiteralParser Literal(Tok, *this);
        if (Literal.hadError)
          return;
  
        Tok.setIdentifierInfo(getIdentifierInfo(Literal.GetString()));
        Tok.setKind(tok::identifier);
      } else {
        Diag(Tok.getLocation(), diag::err_pp_identifier_arg_not_identifier)
          << Tok.getKind();
        // Don't walk past anything that's not a real token.
        if (Tok.isOneOf(tok::eof, tok::eod) || Tok.isAnnotation())
          return;
      }
  
      // Discard the ')', preserving 'Tok' as our result.
      Token RParen;
      LexNonComment(RParen);
      if (RParen.isNot(tok::r_paren)) {
        Diag(getLocForEndOfToken(Tok.getLocation()), diag::err_pp_expected_after)
          << Tok.getKind() << tok::r_paren;
        Diag(LParenLoc, diag::note_matching) << tok::l_paren;
      }
      return;
    } else if (II == Ident__is_target_arch) {
      EvaluateFeatureLikeBuiltinMacro(
          OS, Tok, II, *this, false,
          [this](Token &Tok, bool &HasLexedNextToken) -> int {
            IdentifierInfo *II = ExpectFeatureIdentifierInfo(
                Tok, *this, diag::err_feature_check_malformed);
            return II && isTargetArch(getTargetInfo(), II);
          });
    } else if (II == Ident__is_target_vendor) {
      EvaluateFeatureLikeBuiltinMacro(
          OS, Tok, II, *this, false,
          [this](Token &Tok, bool &HasLexedNextToken) -> int {
            IdentifierInfo *II = ExpectFeatureIdentifierInfo(
                Tok, *this, diag::err_feature_check_malformed);
            return II && isTargetVendor(getTargetInfo(), II);
          });
    } else if (II == Ident__is_target_os) {
      EvaluateFeatureLikeBuiltinMacro(
          OS, Tok, II, *this, false,
          [this](Token &Tok, bool &HasLexedNextToken) -> int {
            IdentifierInfo *II = ExpectFeatureIdentifierInfo(
                Tok, *this, diag::err_feature_check_malformed);
            return II && isTargetOS(getTargetInfo(), II);
          });
    } else if (II == Ident__is_target_environment) {
      EvaluateFeatureLikeBuiltinMacro(
          OS, Tok, II, *this, false,
          [this](Token &Tok, bool &HasLexedNextToken) -> int {
            IdentifierInfo *II = ExpectFeatureIdentifierInfo(
                Tok, *this, diag::err_feature_check_malformed);
            return II && isTargetEnvironment(getTargetInfo(), II);
          });
    } else {
      llvm_unreachable("Unknown identifier!");
    }
    CreateString(OS.str(), Tok, Tok.getLocation(), Tok.getLocation());
    Tok.setFlagValue(Token::StartOfLine, IsAtStartOfLine);
    Tok.setFlagValue(Token::LeadingSpace, HasLeadingSpace);
  }
  
  void Preprocessor::markMacroAsUsed(MacroInfo *MI) {
    // If the 'used' status changed, and the macro requires 'unused' warning,
    // remove its SourceLocation from the warn-for-unused-macro locations.
    if (MI->isWarnIfUnused() && !MI->isUsed())
      WarnUnusedMacroLocs.erase(MI->getDefinitionLoc());
    MI->setIsUsed(true);
  }
  