text: //===--- MacroExpansion.cpp - Top level Macro Expansion -------------------===//
  //
  //                     The LLVM Compiler Infrastructure
  //
  // This file is distributed under the University of Illinois Open Source
  // License. See LICENSE.TXT for details.
  //
  //===----------------------------------------------------------------------===//
  //
  // This file implements the top level handling of macro expansion for the
  // preprocessor.
  //
  //===----------------------------------------------------------------------===//
  
  #include "clang/Lex/Preprocessor.h"
  #include "clang/Basic/Attributes.h"
  #include "clang/Basic/FileManager.h"
  #include "clang/Basic/SourceManager.h"
  #include "clang/Basic/TargetInfo.h"
  #include "clang/Lex/CodeCompletionHandler.h"
  #include "clang/Lex/ExternalPreprocessorSource.h"
  #include "clang/Lex/LexDiagnostic.h"
  #include "clang/Lex/MacroArgs.h"
  #include "clang/Lex/MacroInfo.h"
  #include "llvm/ADT/STLExtras.h"
  #include "llvm/ADT/SmallString.h"
  #include "llvm/ADT/StringSwitch.h"
  #include "llvm/Config/llvm-config.h"
  #include "llvm/Support/ErrorHandling.h"
  #include "llvm/Support/Format.h"
  #include "llvm/Support/raw_ostream.h"
  #include <cstdio>
  #include <ctime>
  using namespace clang;
  
  MacroDirective *
  Preprocessor::getMacroDirectiveHistory(const IdentifierInfo *II) const {
    assert(II->hadMacroDefinition() && "Identifier has not been not a macro!");
  
    macro_iterator Pos = Macros.find(II);
    assert(Pos != Macros.end() && "Identifier macro info is missing!");
    return Pos->second;
  }
  
  void Preprocessor::appendMacroDirective(IdentifierInfo *II, MacroDirective *MD){
    assert(MD && "MacroDirective should be non-zero!");
    assert(!MD->getPrevious() && "Already attached to a MacroDirective history.");
  
    MacroDirective *&StoredMD = Macros[II];
    MD->setPrevious(StoredMD);
    StoredMD = MD;
    II->setHasMacroDefinition(MD->isDefined());
    bool isImportedMacro = isa<DefMacroDirective>(MD) &&
                           cast<DefMacroDirective>(MD)->isImported();
    if (II->isFromAST() && !isImportedMacro)
      II->setChangedSinceDeserialization();
  }
  
  void Preprocessor::setLoadedMacroDirective(IdentifierInfo *II,
                                             MacroDirective *MD) {
    assert(II && MD);
    MacroDirective *&StoredMD = Macros[II];
    assert(!StoredMD &&
           "the macro history was modified before initializing it from a pch");
    StoredMD = MD;
    // Setup the identifier as having associated macro history.
    II->setHasMacroDefinition(true);
    if (!MD->isDefined())
      II->setHasMacroDefinition(false);
  }
  
  /// 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");
  
    // GCC Extensions.
    Ident__BASE_FILE__     = RegisterBuiltinMacro(*this, "__BASE_FILE__");
    Ident__INCLUDE_LEVEL__ = RegisterBuiltinMacro(*this, "__INCLUDE_LEVEL__");
    Ident__TIMESTAMP__     = RegisterBuiltinMacro(*this, "__TIMESTAMP__");
  
    // Microsoft Extensions.
    if (LangOpts.MicrosoftExt) {
      Ident__identifier = RegisterBuiltinMacro(*this, "__identifier");
      Ident__pragma = RegisterBuiltinMacro(*this, "__pragma");
    } else {
      Ident__identifier = nullptr;
      Ident__pragma = nullptr;
    }
  
    // Clang Extensions.
    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");
    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");
  
    // Modules.
    if (LangOpts.Modules) {
      Ident__building_module  = RegisterBuiltinMacro(*this, "__building_module");
  
      // __MODULE__
      if (!LangOpts.CurrentModule.empty())
        Ident__MODULE__ = RegisterBuiltinMacro(*this, "__MODULE__");
      else
        Ident__MODULE__ = nullptr;
    } else {
      Ident__building_module = nullptr;
      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 (II->hasMacroDefinition() && PP.getMacroInfo(II)->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.
    for (MacroInfo::arg_iterator I = MI->arg_begin(), E = MI->arg_end();
         I != E; ++I)
      if (*I == II)
        return false;   // Identifier is a macro argument.
  
    return true;
  }
  
  
  /// 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 if (CurPTHLexer)
      Val = CurPTHLexer->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 (unsigned i = IncludeMacroStack.size(); i != 0; --i) {
        IncludeStackInfo &Entry = IncludeMacroStack[i-1];
        if (Entry.TheLexer)
          Val = Entry.TheLexer->isNextPPTokenLParen();
        else if (Entry.ThePTHLexer)
          Val = Entry.ThePTHLexer->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,
                                                   MacroDirective *MD) {
    MacroDirective::DefInfo Def = MD->getDefinition();
    assert(Def.isValid());
    MacroInfo *MI = Def.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, MD,
                                             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;
      Args = ReadFunctionLikeMacroArgs(Identifier, MI, ExpansionEnd);
  
      // Finished parsing args.
      InMacroArgs = false;
  
      // 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, MD, ExpansionRange));
      } else {
        Callbacks->MacroExpands(Identifier, MD, ExpansionRange, Args);
        if (!DelayedMacroExpandsCallbacks.empty()) {
          for (unsigned i=0, e = DelayedMacroExpandsCallbacks.size(); i!=e; ++i) {
            MacroExpandsInfo &Info = DelayedMacroExpandsCallbacks[i];
            // 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 (Def.getDirective()->isAmbiguous()) {
      Diag(Identifier, diag::warn_pp_ambiguous_macro)
        << Identifier.getIdentifierInfo();
      Diag(MI->getDefinitionLoc(), diag::note_pp_ambiguous_macro_chosen)
        << Identifier.getIdentifierInfo();
      for (MacroDirective::DefInfo PrevDef = Def.getPreviousDefinition();
           PrevDef && !PrevDef.isUndefined();
           PrevDef = PrevDef.getPreviousDefinition()) {
        Diag(PrevDef.getMacroInfo()->getDefinitionLoc(),
             diag::note_pp_ambiguous_macro_other)
          << Identifier.getIdentifierInfo();
        if (!PrevDef.getDirective()->isAmbiguous())
          break;
      }
    }
  
    // 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();
      }
    }
    if (!Brackets.empty())
      return false;
    return true;
  }
  
  /// 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::ReadFunctionLikeMacroArgs(Token &MacroName,
                                                     MacroInfo *MI,
                                                     SourceLocation &MacroEnd) {
    // The number of fixed arguments to parse.
    unsigned NumFixedArgsLeft = MI->getNumArgs();
    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;
  
    SourceLocation TooManyArgsLoc;
  
    unsigned NumActuals = 0;
    while (Tok.isNot(tok::r_paren)) {
      if (ContainsCodeCompletionTok && (Tok.is(tok::eof) || Tok.is(tok::eod)))
        break;
  
      assert((Tok.is(tok::l_paren) || Tok.is(tok::comma)) &&
             "only expect argument separators here");
  
      unsigned 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 (1) {
        // 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.is(tok::eof) || Tok.is(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;
          } else {
            // Do not lose the EOF/EOD.
            Token *Toks = new Token[1];
            Toks[0] = Tok;
            EnterTokenStream(Toks, 1, true, true);
            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();
            break;
          }
        } else if (Tok.is(tok::l_paren)) {
          ++NumParens;
        } else if (Tok.is(tok::comma) && NumParens == 0 &&
                   !(Tok.getFlags() & Token::IgnoredComma)) {
          // 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 above.
  
          // 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.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 && !LangOpts.C99)
        Diag(Tok, LangOpts.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->getNumArgs();
  
    // 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 (const SourceRange &Range : InitLists)
            DB << Range;
        }
        return nullptr;
      }
      if (FixedNumArgs != MinArgsExpected)
        return nullptr;
  
      DiagnosticBuilder DB = Diag(MacroName, diag::note_suggest_parens_for_macro);
      for (const 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 (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()) {
          Diag(Tok, 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);
  }
  
  /// \brief 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 (unsigned i = 0, e = MacroExpandingLexersStack.size(); i != e; ++i) {
        TokenLexer *prevLexer;
        size_t tokIndex;
        std::tie(prevLexer, tokIndex) = MacroExpandingLexersStack[i];
        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, const IdentifierInfo *II) {
    const LangOptions &LangOpts = PP.getLangOpts();
    StringRef Feature = II->getName();
  
    // Normalize the feature name, __foo__ becomes foo.
    if (Feature.startswith("__") && Feature.endswith("__") && Feature.size() >= 4)
      Feature = Feature.substr(2, Feature.size() - 4);
  
    return llvm::StringSwitch<bool>(Feature)
             .Case("address_sanitizer", LangOpts.Sanitize.Address)
             .Case("attribute_analyzer_noreturn", true)
             .Case("attribute_availability", true)
             .Case("attribute_availability_with_message", true)
             .Case("attribute_cf_returns_not_retained", true)
             .Case("attribute_cf_returns_retained", true)
             .Case("attribute_deprecated_with_message", true)
             .Case("attribute_ext_vector_type", true)
             .Case("attribute_ns_returns_not_retained", true)
             .Case("attribute_ns_returns_retained", true)
             .Case("attribute_ns_consumes_self", true)
             .Case("attribute_ns_consumed", true)
             .Case("attribute_cf_consumed", true)
             .Case("attribute_objc_ivar_unused", true)
             .Case("attribute_objc_method_family", true)
             .Case("attribute_overloadable", true)
             .Case("attribute_unavailable_with_message", true)
             .Case("attribute_unused_on_fields", true)
             .Case("blocks", LangOpts.Blocks)
             .Case("c_thread_safety_attributes", true)
             .Case("cxx_exceptions", LangOpts.CXXExceptions)
             .Case("cxx_rtti", LangOpts.RTTI)
             .Case("enumerator_attributes", true)
             .Case("memory_sanitizer", LangOpts.Sanitize.Memory)
             .Case("thread_sanitizer", LangOpts.Sanitize.Thread)
             .Case("dataflow_sanitizer", LangOpts.Sanitize.DataFlow)
             // Objective-C features
             .Case("objc_arr", LangOpts.ObjCAutoRefCount) // FIXME: REMOVE?
             .Case("objc_arc", LangOpts.ObjCAutoRefCount)
             .Case("objc_arc_weak", LangOpts.ObjCARCWeak)
             .Case("objc_default_synthesize_properties", LangOpts.ObjC2)
             .Case("objc_fixed_enum", LangOpts.ObjC2)
             .Case("objc_instancetype", LangOpts.ObjC2)
             .Case("objc_modules", LangOpts.ObjC2 && LangOpts.Modules)
             .Case("objc_nonfragile_abi", LangOpts.ObjCRuntime.isNonFragile())
             .Case("objc_property_explicit_atomic", true) // Does clang support explicit "atomic" keyword?
             .Case("objc_protocol_qualifier_mangling", true)
             .Case("objc_weak_class", LangOpts.ObjCRuntime.hasWeakClassImport())
             .Case("ownership_holds", true)
             .Case("ownership_returns", true)
             .Case("ownership_takes", true)
             .Case("objc_bool", true)
             .Case("objc_subscripting", LangOpts.ObjCRuntime.isNonFragile())
             .Case("objc_array_literals", LangOpts.ObjC2)
             .Case("objc_dictionary_literals", LangOpts.ObjC2)
             .Case("objc_boxed_expressions", LangOpts.ObjC2)
             .Case("arc_cf_code_audited", true)
             // C11 features
             .Case("c_alignas", LangOpts.C11)
             .Case("c_atomic", LangOpts.C11)
             .Case("c_generic_selections", LangOpts.C11)
             .Case("c_static_assert", LangOpts.C11)
             .Case("c_thread_local",
                   LangOpts.C11 && PP.getTargetInfo().isTLSSupported())
             // C++11 features
             .Case("cxx_access_control_sfinae", LangOpts.CPlusPlus11)
             .Case("cxx_alias_templates", LangOpts.CPlusPlus11)
             .Case("cxx_alignas", LangOpts.CPlusPlus11)
             .Case("cxx_atomic", LangOpts.CPlusPlus11)
             .Case("cxx_attributes", LangOpts.CPlusPlus11)
             .Case("cxx_auto_type", LangOpts.CPlusPlus11)
             .Case("cxx_constexpr", LangOpts.CPlusPlus11)
             .Case("cxx_decltype", LangOpts.CPlusPlus11)
             .Case("cxx_decltype_incomplete_return_types", LangOpts.CPlusPlus11)
             .Case("cxx_default_function_template_args", LangOpts.CPlusPlus11)
             .Case("cxx_defaulted_functions", LangOpts.CPlusPlus11)
             .Case("cxx_delegating_constructors", LangOpts.CPlusPlus11)
             .Case("cxx_deleted_functions", LangOpts.CPlusPlus11)
             .Case("cxx_explicit_conversions", LangOpts.CPlusPlus11)
             .Case("cxx_generalized_initializers", LangOpts.CPlusPlus11)
             .Case("cxx_implicit_moves", LangOpts.CPlusPlus11)
             .Case("cxx_inheriting_constructors", LangOpts.CPlusPlus11)
             .Case("cxx_inline_namespaces", LangOpts.CPlusPlus11)
             .Case("cxx_lambdas", LangOpts.CPlusPlus11)
             .Case("cxx_local_type_template_args", LangOpts.CPlusPlus11)
             .Case("cxx_nonstatic_member_init", LangOpts.CPlusPlus11)
             .Case("cxx_noexcept", LangOpts.CPlusPlus11)
             .Case("cxx_nullptr", LangOpts.CPlusPlus11)
             .Case("cxx_override_control", LangOpts.CPlusPlus11)
             .Case("cxx_range_for", LangOpts.CPlusPlus11)
             .Case("cxx_raw_string_literals", LangOpts.CPlusPlus11)
             .Case("cxx_reference_qualified_functions", LangOpts.CPlusPlus11)
             .Case("cxx_rvalue_references", LangOpts.CPlusPlus11)
             .Case("cxx_strong_enums", LangOpts.CPlusPlus11)
             .Case("cxx_static_assert", LangOpts.CPlusPlus11)
             .Case("cxx_thread_local",
                   LangOpts.CPlusPlus11 && PP.getTargetInfo().isTLSSupported())
             .Case("cxx_trailing_return", LangOpts.CPlusPlus11)
             .Case("cxx_unicode_literals", LangOpts.CPlusPlus11)
             .Case("cxx_unrestricted_unions", LangOpts.CPlusPlus11)
             .Case("cxx_user_literals", LangOpts.CPlusPlus11)
             .Case("cxx_variadic_templates", LangOpts.CPlusPlus11)
             // C++1y features
             .Case("cxx_aggregate_nsdmi", LangOpts.CPlusPlus1y)
             .Case("cxx_binary_literals", LangOpts.CPlusPlus1y)
             .Case("cxx_contextual_conversions", LangOpts.CPlusPlus1y)
             .Case("cxx_decltype_auto", LangOpts.CPlusPlus1y)
             .Case("cxx_generic_lambdas", LangOpts.CPlusPlus1y)
             .Case("cxx_init_captures", LangOpts.CPlusPlus1y)
             .Case("cxx_relaxed_constexpr", LangOpts.CPlusPlus1y)
             .Case("cxx_return_type_deduction", LangOpts.CPlusPlus1y)
             .Case("cxx_variable_templates", LangOpts.CPlusPlus1y)
             // C++ TSes
             //.Case("cxx_runtime_arrays", LangOpts.CPlusPlusTSArrays)
             //.Case("cxx_concepts", LangOpts.CPlusPlusTSConcepts)
             // FIXME: Should this be __has_feature or __has_extension?
             //.Case("raw_invocation_type", LangOpts.CPlusPlus)
             // Type traits
             .Case("has_nothrow_assign", LangOpts.CPlusPlus)
             .Case("has_nothrow_copy", LangOpts.CPlusPlus)
             .Case("has_nothrow_constructor", LangOpts.CPlusPlus)
             .Case("has_trivial_assign", LangOpts.CPlusPlus)
             .Case("has_trivial_copy", LangOpts.CPlusPlus)
             .Case("has_trivial_constructor", LangOpts.CPlusPlus)
             .Case("has_trivial_destructor", LangOpts.CPlusPlus)
             .Case("has_virtual_destructor", LangOpts.CPlusPlus)
             .Case("is_abstract", LangOpts.CPlusPlus)
             .Case("is_base_of", LangOpts.CPlusPlus)
             .Case("is_class", LangOpts.CPlusPlus)
             .Case("is_constructible", LangOpts.CPlusPlus)
             .Case("is_convertible_to", LangOpts.CPlusPlus)
             .Case("is_empty", LangOpts.CPlusPlus)
             .Case("is_enum", LangOpts.CPlusPlus)
             .Case("is_final", LangOpts.CPlusPlus)
             .Case("is_literal", LangOpts.CPlusPlus)
             .Case("is_standard_layout", LangOpts.CPlusPlus)
             .Case("is_pod", LangOpts.CPlusPlus)
             .Case("is_polymorphic", LangOpts.CPlusPlus)
             .Case("is_sealed", LangOpts.MicrosoftExt)
             .Case("is_trivial", LangOpts.CPlusPlus)
             .Case("is_trivially_assignable", LangOpts.CPlusPlus)
             .Case("is_trivially_constructible", LangOpts.CPlusPlus)
             .Case("is_trivially_copyable", LangOpts.CPlusPlus)
             .Case("is_union", LangOpts.CPlusPlus)
             .Case("modules", LangOpts.Modules)
             .Case("tls", PP.getTargetInfo().isTLSSupported())
             .Case("underlying_type", LangOpts.CPlusPlus)
             .Default(false);
  }
  
  /// 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, const IdentifierInfo *II) {
    if (HasFeature(PP, II))
      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();
    StringRef Extension = II->getName();
  
    // 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.
    return llvm::StringSwitch<bool>(Extension)
             // C11 features supported by other languages as extensions.
             .Case("c_alignas", true)
             .Case("c_atomic", true)
             .Case("c_generic_selections", true)
             .Case("c_static_assert", true)
             .Case("c_thread_local", PP.getTargetInfo().isTLSSupported())
             // C++11 features supported by other languages as extensions.
             .Case("cxx_atomic", LangOpts.CPlusPlus)
             .Case("cxx_deleted_functions", LangOpts.CPlusPlus)
             .Case("cxx_explicit_conversions", LangOpts.CPlusPlus)
             .Case("cxx_inline_namespaces", LangOpts.CPlusPlus)
             .Case("cxx_local_type_template_args", LangOpts.CPlusPlus)
             .Case("cxx_nonstatic_member_init", LangOpts.CPlusPlus)
             .Case("cxx_override_control", LangOpts.CPlusPlus)
             .Case("cxx_range_for", LangOpts.CPlusPlus)
             .Case("cxx_reference_qualified_functions", LangOpts.CPlusPlus)
             .Case("cxx_rvalue_references", LangOpts.CPlusPlus)
             // C++1y features supported by other languages as extensions.
             .Case("cxx_binary_literals", true)
             .Case("cxx_init_captures", LangOpts.CPlusPlus11)
             .Case("cxx_variable_templates", LangOpts.CPlusPlus)
             .Default(false);
  }
  
  /// 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,
                                       const DirectoryLookup *LookupFrom) {
    // 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->getName();
      return false;
    }
  
    // Get '('.
    PP.LexNonComment(Tok);
  
    // 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.is(tok::angle_string_literal) && !Tok.is(tok::string_literal) &&
          !Tok.is(tok::less))
        return false;
    } else {
      // Save '(' location for possible missing ')' message.
      LParenLoc = Tok.getLocation();
  
      if (PP.getCurrentLexer()) {
        // Get the file name.
        PP.getCurrentLexer()->LexIncludeFilename(Tok);
      } else {
        // We're in a macro, so we can't use LexIncludeFilename; just
        // grab the next token.
        PP.Lex(Tok);
      }
    }
  
    // Reserve a buffer to get the spelling.
    SmallString<128> FilenameBuffer;
    StringRef Filename;
    SourceLocation EndLoc;
    
    switch (Tok.getKind()) {
    case tok::eod:
      // If the token kind is EOD, the error has already been diagnosed.
      return false;
  
    case tok::angle_string_literal:
    case tok::string_literal: {
      bool Invalid = false;
      Filename = PP.getSpelling(Tok, FilenameBuffer, &Invalid);
      if (Invalid)
        return false;
      break;
    }
  
    case tok::less:
      // This could be a <foo/bar.h> file coming from a macro expansion.  In this
      // case, glue the tokens together into FilenameBuffer and interpret those.
      FilenameBuffer.push_back('<');
      if (PP.ConcatenateIncludeName(FilenameBuffer, EndLoc)) {
        // Let the caller know a <eod> was found by changing the Token kind.
        Tok.setKind(tok::eod);
        return false;   // Found <eod> but no ">"?  Diagnostic already emitted.
      }
      Filename = FilenameBuffer.str();
      break;
    default:
      PP.Diag(Tok.getLocation(), diag::err_pp_expects_filename);
      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.
    const DirectoryLookup *CurDir;
    const FileEntry *File =
        PP.LookupFile(FilenameLoc, Filename, isAngled, LookupFrom, CurDir,
                      nullptr, nullptr, nullptr);
  
    // Get the result value.  A result of true means the file exists.
    return File != nullptr;
  }
  
  /// EvaluateHasInclude - Process a '__has_include("path")' expression.
  /// Returns true if successful.
  static bool EvaluateHasInclude(Token &Tok, IdentifierInfo *II,
                                 Preprocessor &PP) {
    return EvaluateHasIncludeCommon(Tok, II, PP, nullptr);
  }
  
  /// EvaluateHasIncludeNext - Process '__has_include_next("path")' expression.
  /// Returns true if successful.
  static bool EvaluateHasIncludeNext(Token &Tok,
                                     IdentifierInfo *II, Preprocessor &PP) {
    // __has_include_next is like __has_include, except that we start
    // searching after the current found directory.  If we can't do this,
    // issue a diagnostic.
    const DirectoryLookup *Lookup = PP.GetCurDirLookup();
    if (PP.isInPrimaryFile()) {
      Lookup = nullptr;
      PP.Diag(Tok, diag::pp_include_next_in_primary);
    } else if (!Lookup) {
      PP.Diag(Tok, diag::pp_include_next_absolute_path);
    } else {
      // Start looking up in the next directory.
      ++Lookup;
    }
  
    return EvaluateHasIncludeCommon(Tok, II, PP, Lookup);
  }
  
  /// \brief Process __building_module(identifier) expression.
  /// \returns true if we are building the named module, false otherwise.
  static bool EvaluateBuildingModule(Token &Tok,
                                     IdentifierInfo *II, Preprocessor &PP) {
    // Get '('.
    PP.LexNonComment(Tok);
  
    // Ensure we have a '('.
    if (Tok.isNot(tok::l_paren)) {
      PP.Diag(Tok.getLocation(), diag::err_pp_expected_after) << II
                                                              << tok::l_paren;
      return false;
    }
  
    // Save '(' location for possible missing ')' message.
    SourceLocation LParenLoc = Tok.getLocation();
  
    // Get the module name.
    PP.LexNonComment(Tok);
  
    // Ensure that we have an identifier.
    if (Tok.isNot(tok::identifier)) {
      PP.Diag(Tok.getLocation(), diag::err_expected_id_building_module);
      return false;
    }
  
    bool Result
      = Tok.getIdentifierInfo()->getName() == PP.getLangOpts().CurrentModule;
  
    // Get ')'.
    PP.LexNonComment(Tok);
  
    // Ensure we have a trailing ).
    if (Tok.isNot(tok::r_paren)) {
      PP.Diag(Tok.getLocation(), diag::err_pp_expected_after) << II
                                                              << tok::r_paren;
      PP.Diag(LParenLoc, diag::note_matching) << tok::l_paren;
      return false;
    }
  
    return Result;
  }
  
  /// 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);
  
    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).second;
      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__) {
      // 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<128> FN;
      if (PLoc.isValid()) {
        FN += PLoc.getFilename();
        Lexer::Stringify(FN);
        OS << '"' << FN.str() << '"';
      }
      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__COUNTER__) {
      // __COUNTER__ expands to a simple numeric value.
      OS << CounterValue++;
      Tok.setKind(tok::numeric_constant);
    } else if (II == Ident__has_feature   ||
               II == Ident__has_extension ||
               II == Ident__has_builtin   ||
               II == Ident__is_identifier ||
               II == Ident__has_attribute) {
      // The argument to these builtins should be a parenthesized identifier.
      SourceLocation StartLoc = Tok.getLocation();
  
      bool IsValid = false;
      IdentifierInfo *FeatureII = nullptr;
  
      // Read the '('.
      LexUnexpandedToken(Tok);
      if (Tok.is(tok::l_paren)) {
        // Read the identifier
        LexUnexpandedToken(Tok);
        if ((FeatureII = Tok.getIdentifierInfo())) {
          // Read the ')'.
          LexUnexpandedToken(Tok);
          if (Tok.is(tok::r_paren))
            IsValid = true;
        }
      }
  
      bool Value = false;
      if (!IsValid)
        Diag(StartLoc, diag::err_feature_check_malformed);
      else if (II == Ident__is_identifier)
        Value = FeatureII->getTokenID() == tok::identifier;
      else if (II == Ident__has_builtin) {
        // Check for a builtin is trivial.
        Value = FeatureII->getBuiltinID() != 0;
      } else if (II == Ident__has_attribute)
        Value = hasAttribute(AttrSyntax::Generic, nullptr, FeatureII,
                             getTargetInfo().getTriple(), getLangOpts());
      else if (II == Ident__has_extension)
        Value = HasExtension(*this, FeatureII);
      else {
        assert(II == Ident__has_feature && "Must be feature check");
        Value = HasFeature(*this, FeatureII);
      }
  
      OS << (int)Value;
      if (IsValid)
        Tok.setKind(tok::numeric_constant);
    } 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, *this);
      else
        Value = EvaluateHasIncludeNext(Tok, II, *this);
      OS << (int)Value;
      if (Tok.is(tok::r_paren))
        Tok.setKind(tok::numeric_constant);
    } else if (II == Ident__has_warning) {
      // The argument should be a parenthesized string literal.
      // The argument to these builtins should be a parenthesized identifier.
      SourceLocation StartLoc = Tok.getLocation();    
      bool IsValid = false;
      bool Value = false;
      // Read the '('.
      LexUnexpandedToken(Tok);
      do {
        if (Tok.isNot(tok::l_paren)) {
          Diag(StartLoc, diag::err_warning_check_malformed);
          break;
        }
  
        LexUnexpandedToken(Tok);
        std::string WarningName;
        SourceLocation StrStartLoc = Tok.getLocation();
        if (!FinishLexStringLiteral(Tok, WarningName, "'__has_warning'",
                                    /*MacroExpansion=*/false)) {
          // Eat tokens until ')'.
          while (Tok.isNot(tok::r_paren) && Tok.isNot(tok::eod) &&
                 Tok.isNot(tok::eof))
            LexUnexpandedToken(Tok);
          break;
        }
  
        // Is the end a ')'?
        if (!(IsValid = Tok.is(tok::r_paren))) {
          Diag(StartLoc, diag::err_warning_check_malformed);
          break;
        }
  
        // 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);
          break;
        }
  
        // 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;
        Value = !getDiagnostics().getDiagnosticIDs()->
          getDiagnosticsInGroup(diag::Flavor::WarningOrError,
                                WarningName.substr(2), Diags);
      } while (false);
  
      OS << (int)Value;
      if (IsValid)
        Tok.setKind(tok::numeric_constant);
    } 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.
      OS << (int)EvaluateBuildingModule(Tok, II, *this);
      Tok.setKind(tok::numeric_constant);
    } 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 {
        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.is(tok::eof) || Tok.is(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 {
      llvm_unreachable("Unknown identifier!");
    }
    CreateString(OS.str(), Tok, Tok.getLocation(), Tok.getLocation());
  }
  
  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);
  }
  