//===- TokenLexer.cpp - Lex from a token stream ---------------------------===//

//

// 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 TokenLexer interface.

//

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

#include "clang/Lex/TokenLexer.h"

#include "clang/Basic/Diagnostic.h"

#include "clang/Basic/IdentifierTable.h"

#include "clang/Basic/LangOptions.h"

#include "clang/Basic/SourceLocation.h"

#include "clang/Basic/SourceManager.h"

#include "clang/Basic/TokenKinds.h"

#include "clang/Lex/LexDiagnostic.h"

#include "clang/Lex/Lexer.h"

#include "clang/Lex/MacroArgs.h"

#include "clang/Lex/MacroInfo.h"

#include "clang/Lex/Preprocessor.h"

#include "clang/Lex/Token.h"

#include "clang/Lex/VariadicMacroSupport.h"

#include "llvm/ADT/ArrayRef.h"

#include "llvm/ADT/STLExtras.h"

#include "llvm/ADT/SmallString.h"

#include "llvm/ADT/SmallVector.h"

#include "llvm/ADT/iterator_range.h"

#include <cassert>

#include <cstring>

#include <optional>

using namespace clang;

/// Create a TokenLexer for the specified macro with the specified actual

/// arguments.  Note that this ctor takes ownership of the ActualArgs pointer.

void TokenLexer::Init(Token &Tok, SourceLocation ELEnd, MacroInfo *MI,

                      MacroArgs *Actuals) {

  // If the client is reusing a TokenLexer, make sure to free any memory

  // associated with it.

  destroy();

  Macro = MI;

  ActualArgs = Actuals;

  CurTokenIdx = 0;

  ExpandLocStart = Tok.getLocation();

  ExpandLocEnd = ELEnd;

  AtStartOfLine = Tok.isAtStartOfLine();

  HasLeadingSpace = Tok.hasLeadingSpace();

  NextTokGetsSpace = false;

  Tokens = &*Macro->tokens_begin();

  OwnsTokens = false;

  DisableMacroExpansion = false;

  IsReinject = false;

  NumTokens = Macro->tokens_end()-Macro->tokens_begin();

  MacroExpansionStart = SourceLocation();

  SourceManager &SM = PP.getSourceManager();

  MacroStartSLocOffset = SM.getNextLocalOffset();

  if (NumTokens > 0) {

    assert(Tokens[0].getLocation().isValid());

    assert((Tokens[0].getLocation().isFileID() || Tokens[0].is(tok::comment)) &&

           "Macro defined in macro?");

    assert(ExpandLocStart.isValid());

    // Reserve a source location entry chunk for the length of the macro

    // definition. Tokens that get lexed directly from the definition will

    // have their locations pointing inside this chunk. This is to avoid

    // creating separate source location entries for each token.

    MacroDefStart = SM.getExpansionLoc(Tokens[0].getLocation());

    MacroDefLength = Macro->getDefinitionLength(SM);

    MacroExpansionStart = SM.createExpansionLoc(MacroDefStart,

                                                ExpandLocStart,

                                                ExpandLocEnd,

                                                MacroDefLength);

  }

  // If this is a function-like macro, expand the arguments and change

  // Tokens to point to the expanded tokens.

  if (Macro->isFunctionLike() && Macro->getNumParams())

    ExpandFunctionArguments();

  // Mark the macro as currently disabled, so that it is not recursively

  // expanded.  The macro must be disabled only after argument pre-expansion of

  // function-like macro arguments occurs.

  Macro->DisableMacro();

}

/// Create a TokenLexer for the specified token stream.  This does not

/// take ownership of the specified token vector.

void TokenLexer::Init(const Token *TokArray, unsigned NumToks,

                      bool disableMacroExpansion, bool ownsTokens,

                      bool isReinject) {

  assert(!isReinject || disableMacroExpansion);

  // If the client is reusing a TokenLexer, make sure to free any memory

  // associated with it.

  destroy();

  Macro = nullptr;

  ActualArgs = nullptr;

  Tokens = TokArray;

  OwnsTokens = ownsTokens;

  DisableMacroExpansion = disableMacroExpansion;

  IsReinject = isReinject;

  NumTokens = NumToks;

  CurTokenIdx = 0;

  ExpandLocStart = ExpandLocEnd = SourceLocation();

  AtStartOfLine = false;

  HasLeadingSpace = false;

  NextTokGetsSpace = false;

  MacroExpansionStart = SourceLocation();

  // Set HasLeadingSpace/AtStartOfLine so that the first token will be

  // returned unmodified.

  if (NumToks != 0) {

    AtStartOfLine   = TokArray[0].isAtStartOfLine();

    HasLeadingSpace = TokArray[0].hasLeadingSpace();

  }

}

void TokenLexer::destroy() {

  // If this was a function-like macro that actually uses its arguments, delete

  // the expanded tokens.

  if (OwnsTokens) {

    delete [] Tokens;

    Tokens = nullptr;

    OwnsTokens = false;

  }

  // TokenLexer owns its formal arguments.

  if (ActualArgs) ActualArgs->destroy(PP);

}

bool TokenLexer::MaybeRemoveCommaBeforeVaArgs(

    SmallVectorImpl<Token> &ResultToks, bool HasPasteOperator, MacroInfo *Macro,

    unsigned MacroArgNo, Preprocessor &PP) {

  // Is the macro argument __VA_ARGS__?

  if (!Macro->isVariadic() || MacroArgNo != Macro->getNumParams()-1)

    return false;

  // In Microsoft-compatibility mode, a comma is removed in the expansion

  // of " ... , __VA_ARGS__ " if __VA_ARGS__ is empty.  This extension is

  // not supported by gcc.

  if (!HasPasteOperator && !PP.getLangOpts().MSVCCompat)

    return false;

  // GCC removes the comma in the expansion of " ... , ## __VA_ARGS__ " if

  // __VA_ARGS__ is empty, but not in strict C99 mode where there are no

  // named arguments, where it remains.  In all other modes, including C99

  // with GNU extensions, it is removed regardless of named arguments.

  // Microsoft also appears to support this extension, unofficially.

  if (PP.getLangOpts().C99 && !PP.getLangOpts().GNUMode

        && Macro->getNumParams() < 2)

    return false;

  // Is a comma available to be removed?

  if (ResultToks.empty() || !ResultToks.back().is(tok::comma))

    return false;

  // Issue an extension diagnostic for the paste operator.

  if (HasPasteOperator)

    PP.Diag(ResultToks.back().getLocation(), diag::ext_paste_comma);

  // Remove the comma.

  ResultToks.pop_back();

  if (!ResultToks.empty()) {

    // If the comma was right after another paste (e.g. "X##,##__VA_ARGS__"),

    // then removal of the comma should produce a placemarker token (in C99

    // terms) which we model by popping off the previous ##, giving us a plain

    // "X" when __VA_ARGS__ is empty.

    if (ResultToks.back().is(tok::hashhash))

      ResultToks.pop_back();

    // Remember that this comma was elided.

    ResultToks.back().setFlag(Token::CommaAfterElided);

  }

  // Never add a space, even if the comma, ##, or arg had a space.

  NextTokGetsSpace = false;

  return true;

}

void TokenLexer::stringifyVAOPTContents(

    SmallVectorImpl<Token> &ResultToks, const VAOptExpansionContext &VCtx,

    const SourceLocation VAOPTClosingParenLoc) {

  const int NumToksPriorToVAOpt = VCtx.getNumberOfTokensPriorToVAOpt();

  const unsigned int NumVAOptTokens = ResultToks.size() - NumToksPriorToVAOpt;

  Token *const VAOPTTokens =

      NumVAOptTokens ? &ResultToks[NumToksPriorToVAOpt] : nullptr;

  SmallVector<Token, 64> ConcatenatedVAOPTResultToks;

  // FIXME: Should we keep track within VCtx that we did or didnot

  // encounter pasting - and only then perform this loop.

  // Perform token pasting (concatenation) prior to stringization.

  for (unsigned int CurTokenIdx = 0; CurTokenIdx != NumVAOptTokens;

       ++CurTokenIdx) {

    if (VAOPTTokens[CurTokenIdx].is(tok::hashhash)) {

      assert(CurTokenIdx != 0 &&

             "Can not have __VAOPT__ contents begin with a ##");

      Token &LHS = VAOPTTokens[CurTokenIdx - 1];

      pasteTokens(LHS, llvm::ArrayRef(VAOPTTokens, NumVAOptTokens),

                  CurTokenIdx);

      // Replace the token prior to the first ## in this iteration.

      ConcatenatedVAOPTResultToks.back() = LHS;

      if (CurTokenIdx == NumVAOptTokens)

        break;

    }

    ConcatenatedVAOPTResultToks.push_back(VAOPTTokens[CurTokenIdx]);

  }

  ConcatenatedVAOPTResultToks.push_back(VCtx.getEOFTok());

  // Get the SourceLocation that represents the start location within

  // the macro definition that marks where this string is substituted

  // into: i.e. the __VA_OPT__ and the ')' within the spelling of the

  // macro definition, and use it to indicate that the stringified token

  // was generated from that location.

  const SourceLocation ExpansionLocStartWithinMacro =

      getExpansionLocForMacroDefLoc(VCtx.getVAOptLoc());

  const SourceLocation ExpansionLocEndWithinMacro =

      getExpansionLocForMacroDefLoc(VAOPTClosingParenLoc);

  Token StringifiedVAOPT = MacroArgs::StringifyArgument(

      &ConcatenatedVAOPTResultToks[0], PP, VCtx.hasCharifyBefore() /*Charify*/,

      ExpansionLocStartWithinMacro, ExpansionLocEndWithinMacro);

  if (VCtx.getLeadingSpaceForStringifiedToken())

    StringifiedVAOPT.setFlag(Token::LeadingSpace);

  StringifiedVAOPT.setFlag(Token::StringifiedInMacro);

  // Resize (shrink) the token stream to just capture this stringified token.

  ResultToks.resize(NumToksPriorToVAOpt + 1);

  ResultToks.back() = StringifiedVAOPT;

}

/// Expand the arguments of a function-like macro so that we can quickly

/// return preexpanded tokens from Tokens.

void TokenLexer::ExpandFunctionArguments() {

  SmallVector<Token, 128> ResultToks;

  // Loop through 'Tokens', expanding them into ResultToks.  Keep

  // track of whether we change anything.  If not, no need to keep them.  If so,

  // we install the newly expanded sequence as the new 'Tokens' list.

  bool MadeChange = false;

  std::optional<bool> CalledWithVariadicArguments;

  VAOptExpansionContext VCtx(PP);

  for (unsigned I = 0, E = NumTokens; I != E; ++I) {

    const Token &CurTok = Tokens[I];

    // We don't want a space for the next token after a paste

    // operator.  In valid code, the token will get smooshed onto the

    // preceding one anyway. In assembler-with-cpp mode, invalid

    // pastes are allowed through: in this case, we do not want the

    // extra whitespace to be added.  For example, we want ". ## foo"

    // -> ".foo" not ". foo".

    if (I != 0 && !Tokens[I-1].is(tok::hashhash) && CurTok.hasLeadingSpace())

      NextTokGetsSpace = true;

    if (VCtx.isVAOptToken(CurTok)) {

      MadeChange = true;

      assert(Tokens[I + 1].is(tok::l_paren) &&

             "__VA_OPT__ must be followed by '('");

      ++I;             // Skip the l_paren

      VCtx.sawVAOptFollowedByOpeningParens(CurTok.getLocation(),

                                           ResultToks.size());

      continue;

    }

    // We have entered into the __VA_OPT__ context, so handle tokens

    // appropriately.

    if (VCtx.isInVAOpt()) {

      // If we are about to process a token that is either an argument to

      // __VA_OPT__ or its closing rparen, then:

      //  1) If the token is the closing rparen that exits us out of __VA_OPT__,

      //  perform any necessary stringification or placemarker processing,

      //  and/or skip to the next token.

      //  2) else if macro was invoked without variadic arguments skip this

      //  token.

      //  3) else (macro was invoked with variadic arguments) process the token

      //  normally.

      if (Tokens[I].is(tok::l_paren))

        VCtx.sawOpeningParen(Tokens[I].getLocation());

      // Continue skipping tokens within __VA_OPT__ if the macro was not

      // called with variadic arguments, else let the rest of the loop handle

      // this token. Note sawClosingParen() returns true only if the r_paren matches

      // the closing r_paren of the __VA_OPT__.

      if (!Tokens[I].is(tok::r_paren) || !VCtx.sawClosingParen()) {

        // Lazily expand __VA_ARGS__ when we see the first __VA_OPT__.

        if (!CalledWithVariadicArguments) {

          CalledWithVariadicArguments =

              ActualArgs->invokedWithVariadicArgument(Macro, PP);

        }

        if (!*CalledWithVariadicArguments) {

          // Skip this token.

          continue;

        }

        // ... else the macro was called with variadic arguments, and we do not

        // have a closing rparen - so process this token normally.

      } else {

        // Current token is the closing r_paren which marks the end of the

        // __VA_OPT__ invocation, so handle any place-marker pasting (if

        // empty) by removing hashhash either before (if exists) or after. And

        // also stringify the entire contents if VAOPT was preceded by a hash,

        // but do so only after any token concatenation that needs to occur

        // within the contents of VAOPT.

        if (VCtx.hasStringifyOrCharifyBefore()) {

          // Replace all the tokens just added from within VAOPT into a single

          // stringified token. This requires token-pasting to eagerly occur

          // within these tokens. If either the contents of VAOPT were empty

          // or the macro wasn't called with any variadic arguments, the result

          // is a token that represents an empty string.

          stringifyVAOPTContents(ResultToks, VCtx,

                                 /*ClosingParenLoc*/ Tokens[I].getLocation());

        } else if (/*No tokens within VAOPT*/

                   ResultToks.size() == VCtx.getNumberOfTokensPriorToVAOpt()) {

          // Treat VAOPT as a placemarker token.  Eat either the '##' before the

          // RHS/VAOPT (if one exists, suggesting that the LHS (if any) to that

          // hashhash was not a placemarker) or the '##'

          // after VAOPT, but not both.

          if (ResultToks.size() && ResultToks.back().is(tok::hashhash)) {

            ResultToks.pop_back();

          } else if ((I + 1 != E) && Tokens[I + 1].is(tok::hashhash)) {

            ++I; // Skip the following hashhash.

          }

        } else {

          // If there's a ## before the __VA_OPT__, we might have discovered

          // that the __VA_OPT__ begins with a placeholder. We delay action on

          // that to now to avoid messing up our stashed count of tokens before

          // __VA_OPT__.

          if (VCtx.beginsWithPlaceholder()) {

            assert(VCtx.getNumberOfTokensPriorToVAOpt() > 0 &&

                   ResultToks.size() >= VCtx.getNumberOfTokensPriorToVAOpt() &&

                   ResultToks[VCtx.getNumberOfTokensPriorToVAOpt() - 1].is(

                       tok::hashhash) &&

                   "no token paste before __VA_OPT__");

            ResultToks.erase(ResultToks.begin() +

                             VCtx.getNumberOfTokensPriorToVAOpt() - 1);

          }

          // If the expansion of __VA_OPT__ ends with a placeholder, eat any

          // following '##' token.

          if (VCtx.endsWithPlaceholder() && I + 1 != E &&

              Tokens[I + 1].is(tok::hashhash)) {

            ++I;

          }

        }

        VCtx.reset();

        // We processed __VA_OPT__'s closing paren (and the exit out of

        // __VA_OPT__), so skip to the next token.

        continue;

      }

    }

    // If we found the stringify operator, get the argument stringified.  The

    // preprocessor already verified that the following token is a macro

    // parameter or __VA_OPT__ when the #define was lexed.

    if (CurTok.isOneOf(tok::hash, tok::hashat)) {

      int ArgNo = Macro->getParameterNum(Tokens[I+1].getIdentifierInfo());

      assert((ArgNo != -1 || VCtx.isVAOptToken(Tokens[I + 1])) &&

             "Token following # is not an argument or __VA_OPT__!");

      if (ArgNo == -1) {

        // Handle the __VA_OPT__ case.

        VCtx.sawHashOrHashAtBefore(NextTokGetsSpace,

                                   CurTok.is(tok::hashat));

        continue;

      }

      // Else handle the simple argument case.

      SourceLocation ExpansionLocStart =

          getExpansionLocForMacroDefLoc(CurTok.getLocation());

      SourceLocation ExpansionLocEnd =

          getExpansionLocForMacroDefLoc(Tokens[I+1].getLocation());

      bool Charify = CurTok.is(tok::hashat);

      const Token *UnexpArg = ActualArgs->getUnexpArgument(ArgNo);

      Token Res = MacroArgs::StringifyArgument(

          UnexpArg, PP, Charify, ExpansionLocStart, ExpansionLocEnd);

      Res.setFlag(Token::StringifiedInMacro);

      // The stringified/charified string leading space flag gets set to match

      // the #/#@ operator.

      if (NextTokGetsSpace)

        Res.setFlag(Token::LeadingSpace);

      ResultToks.push_back(Res);

      MadeChange = true;

      ++I;  // Skip arg name.

      NextTokGetsSpace = false;

      continue;

    }

    // Find out if there is a paste (##) operator before or after the token.

    bool NonEmptyPasteBefore =

      !ResultToks.empty() && ResultToks.back().is(tok::hashhash);

    bool PasteBefore = I != 0 && Tokens[I-1].is(tok::hashhash);

    bool PasteAfter = I+1 != E && Tokens[I+1].is(tok::hashhash);

    bool RParenAfter = I+1 != E && Tokens[I+1].is(tok::r_paren);

    assert((!NonEmptyPasteBefore || PasteBefore || VCtx.isInVAOpt()) &&

           "unexpected ## in ResultToks");

    // Otherwise, if this is not an argument token, just add the token to the

    // output buffer.

    IdentifierInfo *II = CurTok.getIdentifierInfo();

    int ArgNo = II ? Macro->getParameterNum(II) : -1;

    if (ArgNo == -1) {

      // This isn't an argument, just add it.

      ResultToks.push_back(CurTok);

      if (NextTokGetsSpace) {

        ResultToks.back().setFlag(Token::LeadingSpace);

        NextTokGetsSpace = false;

      } else if (PasteBefore && !NonEmptyPasteBefore)

        ResultToks.back().clearFlag(Token::LeadingSpace);

      continue;

    }

    // An argument is expanded somehow, the result is different than the

    // input.

    MadeChange = true;

    // Otherwise, this is a use of the argument.

    // In Microsoft mode, remove the comma before __VA_ARGS__ to ensure there

    // are no trailing commas if __VA_ARGS__ is empty.

    if (!PasteBefore && ActualArgs->isVarargsElidedUse() &&

        MaybeRemoveCommaBeforeVaArgs(ResultToks,

                                     /*HasPasteOperator=*/false,

                                     Macro, ArgNo, PP))

      continue;

    // If it is not the LHS/RHS of a ## operator, we must pre-expand the

    // argument and substitute the expanded tokens into the result.  This is

    // C99 6.10.3.1p1.

    if (!PasteBefore && !PasteAfter) {

      const Token *ResultArgToks;

      // Only preexpand the argument if it could possibly need it.  This

      // avoids some work in common cases.

      const Token *ArgTok = ActualArgs->getUnexpArgument(ArgNo);

      if (ActualArgs->ArgNeedsPreexpansion(ArgTok, PP))

        ResultArgToks = &ActualArgs->getPreExpArgument(ArgNo, PP)[0];

      else

        ResultArgToks = ArgTok;  // Use non-preexpanded tokens.

      // If the arg token expanded into anything, append it.

      if (ResultArgToks->isNot(tok::eof)) {

        size_t FirstResult = ResultToks.size();

        unsigned NumToks = MacroArgs::getArgLength(ResultArgToks);

        ResultToks.append(ResultArgToks, ResultArgToks+NumToks);

        // In Microsoft-compatibility mode, we follow MSVC's preprocessing

        // behavior by not considering single commas from nested macro

        // expansions as argument separators. Set a flag on the token so we can

        // test for this later when the macro expansion is processed.

        if (PP.getLangOpts().MSVCCompat && NumToks == 1 &&

            ResultToks.back().is(tok::comma))

          ResultToks.back().setFlag(Token::IgnoredComma);

        // If the '##' came from expanding an argument, turn it into 'unknown'

        // to avoid pasting.

        for (Token &Tok : llvm::drop_begin(ResultToks, FirstResult))

          if (Tok.is(tok::hashhash))

            Tok.setKind(tok::unknown);

        if(ExpandLocStart.isValid()) {

          updateLocForMacroArgTokens(CurTok.getLocation(),

                                     ResultToks.begin()+FirstResult,

                                     ResultToks.end());

        }

        // If any tokens were substituted from the argument, the whitespace

        // before the first token should match the whitespace of the arg

        // identifier.

        ResultToks[FirstResult].setFlagValue(Token::LeadingSpace,

                                             NextTokGetsSpace);

        ResultToks[FirstResult].setFlagValue(Token::StartOfLine, false);

        NextTokGetsSpace = false;

      } else {

        // We're creating a placeholder token. Usually this doesn't matter,

        // but it can affect paste behavior when at the start or end of a

        // __VA_OPT__.

        if (NonEmptyPasteBefore) {

          // We're imagining a placeholder token is inserted here. If this is

          // the first token in a __VA_OPT__ after a ##, delete the ##.

          assert(VCtx.isInVAOpt() && "should only happen inside a __VA_OPT__");

          VCtx.hasPlaceholderAfterHashhashAtStart();

        } else if (RParenAfter)

          VCtx.hasPlaceholderBeforeRParen();

      }

      continue;

    }

    // Okay, we have a token that is either the LHS or RHS of a paste (##)

    // argument.  It gets substituted as its non-pre-expanded tokens.

    const Token *ArgToks = ActualArgs->getUnexpArgument(ArgNo);

    unsigned NumToks = MacroArgs::getArgLength(ArgToks);

    if (NumToks) {  // Not an empty argument?

      bool VaArgsPseudoPaste = false;

      // If this is the GNU ", ## __VA_ARGS__" extension, and we just learned

      // that __VA_ARGS__ expands to multiple tokens, avoid a pasting error when

      // the expander tries to paste ',' with the first token of the __VA_ARGS__

      // expansion.

      if (NonEmptyPasteBefore && ResultToks.size() >= 2 &&

          ResultToks[ResultToks.size()-2].is(tok::comma) &&

          (unsigned)ArgNo == Macro->getNumParams()-1 &&

          Macro->isVariadic()) {

        VaArgsPseudoPaste = true;

        // Remove the paste operator, report use of the extension.

        PP.Diag(ResultToks.pop_back_val().getLocation(), diag::ext_paste_comma);

      }

      ResultToks.append(ArgToks, ArgToks+NumToks);

      // If the '##' came from expanding an argument, turn it into 'unknown'

      // to avoid pasting.

      for (Token &Tok : llvm::make_range(ResultToks.end() - NumToks,

                                         ResultToks.end())) {

        if (Tok.is(tok::hashhash))

          Tok.setKind(tok::unknown);

      }

      if (ExpandLocStart.isValid()) {

        updateLocForMacroArgTokens(CurTok.getLocation(),

                                   ResultToks.end()-NumToks, ResultToks.end());

      }

      // Transfer the leading whitespace information from the token

      // (the macro argument) onto the first token of the

      // expansion. Note that we don't do this for the GNU

      // pseudo-paste extension ", ## __VA_ARGS__".

      if (!VaArgsPseudoPaste) {

        ResultToks[ResultToks.size() - NumToks].setFlagValue(Token::StartOfLine,

                                                             false);

        ResultToks[ResultToks.size() - NumToks].setFlagValue(

            Token::LeadingSpace, NextTokGetsSpace);

      }

      NextTokGetsSpace = false;

      continue;

    }

    // If an empty argument is on the LHS or RHS of a paste, the standard (C99

    // 6.10.3.3p2,3) calls for a bunch of placemarker stuff to occur.  We

    // implement this by eating ## operators when a LHS or RHS expands to

    // empty.

    if (PasteAfter) {

      // Discard the argument token and skip (don't copy to the expansion

      // buffer) the paste operator after it.

      ++I;

      continue;

    }

    if (RParenAfter && !NonEmptyPasteBefore)

      VCtx.hasPlaceholderBeforeRParen();

    // If this is on the RHS of a paste operator, we've already copied the

    // paste operator to the ResultToks list, unless the LHS was empty too.

    // Remove it.

    assert(PasteBefore);

    if (NonEmptyPasteBefore) {

      assert(ResultToks.back().is(tok::hashhash));

      // Do not remove the paste operator if it is the one before __VA_OPT__

      // (and we are still processing tokens within VA_OPT).  We handle the case

      // of removing the paste operator if __VA_OPT__ reduces to the notional

      // placemarker above when we encounter the closing paren of VA_OPT.

      if (!VCtx.isInVAOpt() ||

          ResultToks.size() > VCtx.getNumberOfTokensPriorToVAOpt())

        ResultToks.pop_back();

      else

        VCtx.hasPlaceholderAfterHashhashAtStart();

    }

    // If this is the __VA_ARGS__ token, and if the argument wasn't provided,

    // and if the macro had at least one real argument, and if the token before

    // the ## was a comma, remove the comma.  This is a GCC extension which is

    // disabled when using -std=c99.

    if (ActualArgs->isVarargsElidedUse())

      MaybeRemoveCommaBeforeVaArgs(ResultToks,

                                   /*HasPasteOperator=*/true,

                                   Macro, ArgNo, PP);

  }

  // If anything changed, install this as the new Tokens list.

  if (MadeChange) {

    assert(!OwnsTokens && "This would leak if we already own the token list");

    // This is deleted in the dtor.

    NumTokens = ResultToks.size();

    // The tokens will be added to Preprocessor's cache and will be removed

    // when this TokenLexer finishes lexing them.

    Tokens = PP.cacheMacroExpandedTokens(this, ResultToks);

    // The preprocessor cache of macro expanded tokens owns these tokens,not us.

    OwnsTokens = false;

  }

}

/// Checks if two tokens form wide string literal.

static bool isWideStringLiteralFromMacro(const Token &FirstTok,

                                         const Token &SecondTok) {

  return FirstTok.is(tok::identifier) &&

         FirstTok.getIdentifierInfo()->isStr("L") && SecondTok.isLiteral() &&

         SecondTok.stringifiedInMacro();

}

/// Lex - Lex and return a token from this macro stream.

bool TokenLexer::Lex(Token &Tok) {

  // Lexing off the end of the macro, pop this macro off the expansion stack.

  if (isAtEnd()) {

    // If this is a macro (not a token stream), mark the macro enabled now

    // that it is no longer being expanded.

    if (Macro) Macro->EnableMacro();

    Tok.startToken();

    Tok.setFlagValue(Token::StartOfLine , AtStartOfLine);

    Tok.setFlagValue(Token::LeadingSpace, HasLeadingSpace || NextTokGetsSpace);

    if (CurTokenIdx == 0)

      Tok.setFlag(Token::LeadingEmptyMacro);

    return PP.HandleEndOfTokenLexer(Tok);

  }

  SourceManager &SM = PP.getSourceManager();

  // If this is the first token of the expanded result, we inherit spacing

  // properties later.

  bool isFirstToken = CurTokenIdx == 0;

  // Get the next token to return.

  Tok = Tokens[CurTokenIdx++];

  if (IsReinject)

    Tok.setFlag(Token::IsReinjected);

  bool TokenIsFromPaste = false;

  // If this token is followed by a token paste (##) operator, paste the tokens!

  // Note that ## is a normal token when not expanding a macro.

  if (!isAtEnd() && Macro &&

      (Tokens[CurTokenIdx].is(tok::hashhash) ||

       // Special processing of L#x macros in -fms-compatibility mode.

       // Microsoft compiler is able to form a wide string literal from

       // 'L#macro_arg' construct in a function-like macro.

       (PP.getLangOpts().MSVCCompat &&

        isWideStringLiteralFromMacro(Tok, Tokens[CurTokenIdx])))) {

    // When handling the microsoft /##/ extension, the final token is

    // returned by pasteTokens, not the pasted token.

    if (pasteTokens(Tok))

      return true;

    TokenIsFromPaste = true;

  }

  // The token's current location indicate where the token was lexed from.  We

  // need this information to compute the spelling of the token, but any

  // diagnostics for the expanded token should appear as if they came from

  // ExpansionLoc.  Pull this information together into a new SourceLocation

  // that captures all of this.

  if (ExpandLocStart.isValid() &&   // Don't do this for token streams.

      // Check that the token's location was not already set properly.

      SM.isBeforeInSLocAddrSpace(Tok.getLocation(), MacroStartSLocOffset)) {

    SourceLocation instLoc;

    if (Tok.is(tok::comment)) {

      instLoc = SM.createExpansionLoc(Tok.getLocation(),

                                      ExpandLocStart,

                                      ExpandLocEnd,

                                      Tok.getLength());

    } else {

      instLoc = getExpansionLocForMacroDefLoc(Tok.getLocation());

    }

    Tok.setLocation(instLoc);

  }

  // If this is the first token, set the lexical properties of the token to

  // match the lexical properties of the macro identifier.

  if (isFirstToken) {

    Tok.setFlagValue(Token::StartOfLine , AtStartOfLine);

    Tok.setFlagValue(Token::LeadingSpace, HasLeadingSpace);

  } else {

    // If this is not the first token, we may still need to pass through

    // leading whitespace if we've expanded a macro.

    if (AtStartOfLine) Tok.setFlag(Token::StartOfLine);

    if (HasLeadingSpace) Tok.setFlag(Token::LeadingSpace);

  }

  AtStartOfLine = false;

  HasLeadingSpace = false;

  // Handle recursive expansion!

  if (!Tok.isAnnotation() && Tok.getIdentifierInfo() != nullptr) {

    // Change the kind of this identifier to the appropriate token kind, e.g.

    // turning "for" into a keyword.

    IdentifierInfo *II = Tok.getIdentifierInfo();

    Tok.setKind(II->getTokenID());

    // If this identifier was poisoned and from a paste, emit an error.  This

    // won't be handled by Preprocessor::HandleIdentifier because this is coming

    // from a macro expansion.

    if (II->isPoisoned() && TokenIsFromPaste) {

      PP.HandlePoisonedIdentifier(Tok);

    }

    if (!DisableMacroExpansion && II->isHandleIdentifierCase())

      return PP.HandleIdentifier(Tok);

  }

  // Otherwise, return a normal token.

  return true;

}

bool TokenLexer::pasteTokens(Token &Tok) {

  return pasteTokens(Tok, llvm::ArrayRef(Tokens, NumTokens), CurTokenIdx);

}

/// LHSTok is the LHS of a ## operator, and CurTokenIdx is the ##

/// operator.  Read the ## and RHS, and paste the LHS/RHS together.  If there

/// are more ## after it, chomp them iteratively.  Return the result as LHSTok.

/// If this returns true, the caller should immediately return the token.

bool TokenLexer::pasteTokens(Token &LHSTok, ArrayRef<Token> TokenStream,

                             unsigned int &CurIdx) {

  assert(CurIdx > 0 && "## can not be the first token within tokens");

  assert((TokenStream[CurIdx].is(tok::hashhash) ||

         (PP.getLangOpts().MSVCCompat &&

          isWideStringLiteralFromMacro(LHSTok, TokenStream[CurIdx]))) &&

             "Token at this Index must be ## or part of the MSVC 'L "

             "#macro-arg' pasting pair");

  // MSVC: If previous token was pasted, this must be a recovery from an invalid

  // paste operation. Ignore spaces before this token to mimic MSVC output.

  // Required for generating valid UUID strings in some MS headers.

  if (PP.getLangOpts().MicrosoftExt && (CurIdx >= 2) &&

      TokenStream[CurIdx - 2].is(tok::hashhash))

    LHSTok.clearFlag(Token::LeadingSpace);

  SmallString<128> Buffer;

  const char *ResultTokStrPtr = nullptr;

  SourceLocation StartLoc = LHSTok.getLocation();

  SourceLocation PasteOpLoc;

  auto IsAtEnd = [&TokenStream, &CurIdx] {

    return TokenStream.size() == CurIdx;

  };

  do {

    // Consume the ## operator if any.

    PasteOpLoc = TokenStream[CurIdx].getLocation();

    if (TokenStream[CurIdx].is(tok::hashhash))

      ++CurIdx;

    assert(!IsAtEnd() && "No token on the RHS of a paste operator!");

    // Get the RHS token.

    const Token &RHS = TokenStream[CurIdx];

    // Allocate space for the result token.  This is guaranteed to be enough for

    // the two tokens.

    Buffer.resize(LHSTok.getLength() + RHS.getLength());

    // Get the spelling of the LHS token in Buffer.

    const char *BufPtr = &Buffer[0];

    bool Invalid = false;

    unsigned LHSLen = PP.getSpelling(LHSTok, BufPtr, &Invalid);

    if (BufPtr != &Buffer[0])   // Really, we want the chars in Buffer!

      memcpy(&Buffer[0], BufPtr, LHSLen);

    if (Invalid)

      return true;

    BufPtr = Buffer.data() + LHSLen;

    unsigned RHSLen = PP.getSpelling(RHS, BufPtr, &Invalid);

    if (Invalid)

      return true;

    if (RHSLen && BufPtr != &Buffer[LHSLen])

      // Really, we want the chars in Buffer!

      memcpy(&Buffer[LHSLen], BufPtr, RHSLen);

    // Trim excess space.

    Buffer.resize(LHSLen+RHSLen);

    // Plop the pasted result (including the trailing newline and null) into a

    // scratch buffer where we can lex it.

    Token ResultTokTmp;

    ResultTokTmp.startToken();

    // Claim that the tmp token is a string_literal so that we can get the

    // character pointer back from CreateString in getLiteralData().

    ResultTokTmp.setKind(tok::string_literal);

    PP.CreateString(Buffer, ResultTokTmp);

    SourceLocation ResultTokLoc = ResultTokTmp.getLocation();

    ResultTokStrPtr = ResultTokTmp.getLiteralData();

    // Lex the resultant pasted token into Result.

    Token Result;

    if (LHSTok.isAnyIdentifier() && RHS.isAnyIdentifier()) {

      // Common paste case: identifier+identifier = identifier.  Avoid creating

      // a lexer and other overhead.

      PP.IncrementPasteCounter(true);

      Result.startToken();

      Result.setKind(tok::raw_identifier);

      Result.setRawIdentifierData(ResultTokStrPtr);

      Result.setLocation(ResultTokLoc);

      Result.setLength(LHSLen+RHSLen);

    } else {

      PP.IncrementPasteCounter(false);

      assert(ResultTokLoc.isFileID() &&

             "Should be a raw location into scratch buffer");

      SourceManager &SourceMgr = PP.getSourceManager();

      FileID LocFileID = SourceMgr.getFileID(ResultTokLoc);

      bool Invalid = false;

      const char *ScratchBufStart

        = SourceMgr.getBufferData(LocFileID, &Invalid).data();

      if (Invalid)

        return false;

      // Make a lexer to lex this string from.  Lex just this one token.

      // Make a lexer object so that we lex and expand the paste result.

      Lexer TL(SourceMgr.getLocForStartOfFile(LocFileID),

               PP.getLangOpts(), ScratchBufStart,

               ResultTokStrPtr, ResultTokStrPtr+LHSLen+RHSLen);

      // Lex a token in raw mode.  This way it won't look up identifiers

      // automatically, lexing off the end will return an eof token, and

      // warnings are disabled.  This returns true if the result token is the

      // entire buffer.

      bool isInvalid = !TL.LexFromRawLexer(Result);

      // If we got an EOF token, we didn't form even ONE token.  For example, we

      // did "/ ## /" to get "//".

      isInvalid |= Result.is(tok::eof);

      // If pasting the two tokens didn't form a full new token, this is an

      // error.  This occurs with "x ## +"  and other stuff.  Return with LHSTok

      // unmodified and with RHS as the next token to lex.

      if (isInvalid) {

        // Explicitly convert the token location to have proper expansion

        // information so that the user knows where it came from.

        SourceManager &SM = PP.getSourceManager();

        SourceLocation Loc =

          SM.createExpansionLoc(PasteOpLoc, ExpandLocStart, ExpandLocEnd, 2);

        // Test for the Microsoft extension of /##/ turning into // here on the

        // error path.

        if (PP.getLangOpts().MicrosoftExt && LHSTok.is(tok::slash) &&

            RHS.is(tok::slash)) {

          HandleMicrosoftCommentPaste(LHSTok, Loc);

          return true;

        }

        // Do not emit the error when preprocessing assembler code.

        if (!PP.getLangOpts().AsmPreprocessor) {

          // If we're in microsoft extensions mode, downgrade this from a hard

          // error to an extension that defaults to an error.  This allows

          // disabling it.

          PP.Diag(Loc, PP.getLangOpts().MicrosoftExt ? diag::ext_pp_bad_paste_ms

                                                     : diag::err_pp_bad_paste)

              << Buffer;

        }

        // An error has occurred so exit loop.

        break;

      }

      // Turn ## into 'unknown' to avoid # ## # from looking like a paste

      // operator.

      if (Result.is(tok::hashhash))

        Result.setKind(tok::unknown);

    }

    // Transfer properties of the LHS over the Result.

    Result.setFlagValue(Token::StartOfLine , LHSTok.isAtStartOfLine());

    Result.setFlagValue(Token::LeadingSpace, LHSTok.hasLeadingSpace());

    // Finally, replace LHS with the result, consume the RHS, and iterate.

    ++CurIdx;

    LHSTok = Result;

  } while (!IsAtEnd() && TokenStream[CurIdx].is(tok::hashhash));

  SourceLocation EndLoc = TokenStream[CurIdx - 1].getLocation();

  // The token's current location indicate where the token was lexed from.  We

  // need this information to compute the spelling of the token, but any

  // diagnostics for the expanded token should appear as if the token was

  // expanded from the full ## expression. Pull this information together into

  // a new SourceLocation that captures all of this.

  SourceManager &SM = PP.getSourceManager();

  if (StartLoc.isFileID())

    StartLoc = getExpansionLocForMacroDefLoc(StartLoc);

  if (EndLoc.isFileID())

    EndLoc = getExpansionLocForMacroDefLoc(EndLoc);

  FileID MacroFID = SM.getFileID(MacroExpansionStart);

  while (SM.getFileID(StartLoc) != MacroFID)

    StartLoc = SM.getImmediateExpansionRange(StartLoc).getBegin();

  while (SM.getFileID(EndLoc) != MacroFID)

    EndLoc = SM.getImmediateExpansionRange(EndLoc).getEnd();

  LHSTok.setLocation(SM.createExpansionLoc(LHSTok.getLocation(), StartLoc, EndLoc,

                                        LHSTok.getLength()));

  // Now that we got the result token, it will be subject to expansion.  Since

  // token pasting re-lexes the result token in raw mode, identifier information

  // isn't looked up.  As such, if the result is an identifier, look up id info.

  if (LHSTok.is(tok::raw_identifier)) {

    // Look up the identifier info for the token.  We disabled identifier lookup

    // by saying we're skipping contents, so we need to do this manually.

    PP.LookUpIdentifierInfo(LHSTok);