lib/Parse/ParsePragma.cpp

//===--- ParsePragma.cpp - Language specific pragma parsing ---------------===//
//
//                     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 language specific #pragma handlers.
//
//===----------------------------------------------------------------------===//

#include "clang/Lex/Preprocessor.h"
#include "clang/Parse/ParseDiagnostic.h"
#include "clang/Parse/Parser.h"
#include "clang/Sema/Scope.h"
#include "llvm/ADT/StringSwitch.h"
using namespace clang;

namespace {

struct PragmaAlignHandler : public PragmaHandler {
  explicit PragmaAlignHandler() : PragmaHandler("align") {}
  void HandlePragma(Preprocessor &PP, PragmaIntroducerKind Introducer,
                    Token &FirstToken) override;
};

struct PragmaGCCVisibilityHandler : public PragmaHandler {
  explicit PragmaGCCVisibilityHandler() : PragmaHandler("visibility") {}
  void HandlePragma(Preprocessor &PP, PragmaIntroducerKind Introducer,
                    Token &FirstToken) override;
};

struct PragmaOptionsHandler : public PragmaHandler {
  explicit PragmaOptionsHandler() : PragmaHandler("options") {}
  void HandlePragma(Preprocessor &PP, PragmaIntroducerKind Introducer,
                    Token &FirstToken) override;
};

struct PragmaPackHandler : public PragmaHandler {
  explicit PragmaPackHandler() : PragmaHandler("pack") {}
  void HandlePragma(Preprocessor &PP, PragmaIntroducerKind Introducer,
                    Token &FirstToken) override;
};

struct PragmaMSStructHandler : public PragmaHandler {
  explicit PragmaMSStructHandler() : PragmaHandler("ms_struct") {}
  void HandlePragma(Preprocessor &PP, PragmaIntroducerKind Introducer,
                    Token &FirstToken) override;
};

struct PragmaUnusedHandler : public PragmaHandler {
  PragmaUnusedHandler() : PragmaHandler("unused") {}
  void HandlePragma(Preprocessor &PP, PragmaIntroducerKind Introducer,
                    Token &FirstToken) override;
};

struct PragmaWeakHandler : public PragmaHandler {
  explicit PragmaWeakHandler() : PragmaHandler("weak") {}
  void HandlePragma(Preprocessor &PP, PragmaIntroducerKind Introducer,
                    Token &FirstToken) override;
};

struct PragmaRedefineExtnameHandler : public PragmaHandler {
  explicit PragmaRedefineExtnameHandler() : PragmaHandler("redefine_extname") {}
  void HandlePragma(Preprocessor &PP, PragmaIntroducerKind Introducer,
                    Token &FirstToken) override;
};

struct PragmaOpenCLExtensionHandler : public PragmaHandler {
  PragmaOpenCLExtensionHandler() : PragmaHandler("EXTENSION") {}
  void HandlePragma(Preprocessor &PP, PragmaIntroducerKind Introducer,
                    Token &FirstToken) override;
};


struct PragmaFPContractHandler : public PragmaHandler {
  PragmaFPContractHandler() : PragmaHandler("FP_CONTRACT") {}
  void HandlePragma(Preprocessor &PP, PragmaIntroducerKind Introducer,
                    Token &FirstToken) override;
};

struct PragmaNoOpenMPHandler : public PragmaHandler {
  PragmaNoOpenMPHandler() : PragmaHandler("omp") { }
  void HandlePragma(Preprocessor &PP, PragmaIntroducerKind Introducer,
                    Token &FirstToken) override;
};

struct PragmaOpenMPHandler : public PragmaHandler {
  PragmaOpenMPHandler() : PragmaHandler("omp") { }
  void HandlePragma(Preprocessor &PP, PragmaIntroducerKind Introducer,
                    Token &FirstToken) override;
};

/// PragmaCommentHandler - "\#pragma comment ...".
struct PragmaCommentHandler : public PragmaHandler {
  PragmaCommentHandler(Sema &Actions)
    : PragmaHandler("comment"), Actions(Actions) {}
  void HandlePragma(Preprocessor &PP, PragmaIntroducerKind Introducer,
                    Token &FirstToken) override;
private:
  Sema &Actions;
};

struct PragmaDetectMismatchHandler : public PragmaHandler {
  PragmaDetectMismatchHandler(Sema &Actions)
    : PragmaHandler("detect_mismatch"), Actions(Actions) {}
  void HandlePragma(Preprocessor &PP, PragmaIntroducerKind Introducer,
                    Token &FirstToken) override;
private:
  Sema &Actions;
};

struct PragmaMSPointersToMembers : public PragmaHandler {
  explicit PragmaMSPointersToMembers() : PragmaHandler("pointers_to_members") {}
  void HandlePragma(Preprocessor &PP, PragmaIntroducerKind Introducer,
                    Token &FirstToken) override;
};

struct PragmaMSVtorDisp : public PragmaHandler {
  explicit PragmaMSVtorDisp() : PragmaHandler("vtordisp") {}
  void HandlePragma(Preprocessor &PP, PragmaIntroducerKind Introducer,
                    Token &FirstToken) override;
};

}  // end namespace

void Parser::initializePragmaHandlers() {
  AlignHandler.reset(new PragmaAlignHandler());
  PP.AddPragmaHandler(AlignHandler.get());

  GCCVisibilityHandler.reset(new PragmaGCCVisibilityHandler());
  PP.AddPragmaHandler("GCC", GCCVisibilityHandler.get());

  OptionsHandler.reset(new PragmaOptionsHandler());
  PP.AddPragmaHandler(OptionsHandler.get());

  PackHandler.reset(new PragmaPackHandler());
  PP.AddPragmaHandler(PackHandler.get());

  MSStructHandler.reset(new PragmaMSStructHandler());
  PP.AddPragmaHandler(MSStructHandler.get());

  UnusedHandler.reset(new PragmaUnusedHandler());
  PP.AddPragmaHandler(UnusedHandler.get());

  WeakHandler.reset(new PragmaWeakHandler());
  PP.AddPragmaHandler(WeakHandler.get());

  RedefineExtnameHandler.reset(new PragmaRedefineExtnameHandler());
  PP.AddPragmaHandler(RedefineExtnameHandler.get());

  FPContractHandler.reset(new PragmaFPContractHandler());
  PP.AddPragmaHandler("STDC", FPContractHandler.get());

  if (getLangOpts().OpenCL) {
    OpenCLExtensionHandler.reset(new PragmaOpenCLExtensionHandler());
    PP.AddPragmaHandler("OPENCL", OpenCLExtensionHandler.get());

    PP.AddPragmaHandler("OPENCL", FPContractHandler.get());
  }
  if (getLangOpts().OpenMP)
    OpenMPHandler.reset(new PragmaOpenMPHandler());
  else
    OpenMPHandler.reset(new PragmaNoOpenMPHandler());
  PP.AddPragmaHandler(OpenMPHandler.get());

  if (getLangOpts().MicrosoftExt) {
    MSCommentHandler.reset(new PragmaCommentHandler(Actions));
    PP.AddPragmaHandler(MSCommentHandler.get());
    MSDetectMismatchHandler.reset(new PragmaDetectMismatchHandler(Actions));
    PP.AddPragmaHandler(MSDetectMismatchHandler.get());
    MSPointersToMembers.reset(new PragmaMSPointersToMembers());
    PP.AddPragmaHandler(MSPointersToMembers.get());
    MSVtorDisp.reset(new PragmaMSVtorDisp());
    PP.AddPragmaHandler(MSVtorDisp.get());
  }
}

void Parser::resetPragmaHandlers() {
  // Remove the pragma handlers we installed.
  PP.RemovePragmaHandler(AlignHandler.get());
  AlignHandler.reset();
  PP.RemovePragmaHandler("GCC", GCCVisibilityHandler.get());
  GCCVisibilityHandler.reset();
  PP.RemovePragmaHandler(OptionsHandler.get());
  OptionsHandler.reset();
  PP.RemovePragmaHandler(PackHandler.get());
  PackHandler.reset();
  PP.RemovePragmaHandler(MSStructHandler.get());
  MSStructHandler.reset();
  PP.RemovePragmaHandler(UnusedHandler.get());
  UnusedHandler.reset();
  PP.RemovePragmaHandler(WeakHandler.get());
  WeakHandler.reset();
  PP.RemovePragmaHandler(RedefineExtnameHandler.get());
  RedefineExtnameHandler.reset();

  if (getLangOpts().OpenCL) {
    PP.RemovePragmaHandler("OPENCL", OpenCLExtensionHandler.get());
    OpenCLExtensionHandler.reset();
    PP.RemovePragmaHandler("OPENCL", FPContractHandler.get());
  }
  PP.RemovePragmaHandler(OpenMPHandler.get());
  OpenMPHandler.reset();

  if (getLangOpts().MicrosoftExt) {
    PP.RemovePragmaHandler(MSCommentHandler.get());
    MSCommentHandler.reset();
    PP.RemovePragmaHandler(MSDetectMismatchHandler.get());
    MSDetectMismatchHandler.reset();
    PP.RemovePragmaHandler(MSPointersToMembers.get());
    MSPointersToMembers.reset();
    PP.RemovePragmaHandler(MSVtorDisp.get());
    MSVtorDisp.reset();
  }

  PP.RemovePragmaHandler("STDC", FPContractHandler.get());
  FPContractHandler.reset();
}

/// \brief Handle the annotation token produced for #pragma unused(...)
///
/// Each annot_pragma_unused is followed by the argument token so e.g.
/// "#pragma unused(x,y)" becomes:
/// annot_pragma_unused 'x' annot_pragma_unused 'y'
void Parser::HandlePragmaUnused() {
  assert(Tok.is(tok::annot_pragma_unused));
  SourceLocation UnusedLoc = ConsumeToken();
  Actions.ActOnPragmaUnused(Tok, getCurScope(), UnusedLoc);
  ConsumeToken(); // The argument token.
}

void Parser::HandlePragmaVisibility() {
  assert(Tok.is(tok::annot_pragma_vis));
  const IdentifierInfo *VisType =
    static_cast<IdentifierInfo *>(Tok.getAnnotationValue());
  SourceLocation VisLoc = ConsumeToken();
  Actions.ActOnPragmaVisibility(VisType, VisLoc);
}

struct PragmaPackInfo {
  Sema::PragmaPackKind Kind;
  IdentifierInfo *Name;
  Token Alignment;
  SourceLocation LParenLoc;
  SourceLocation RParenLoc;
};

void Parser::HandlePragmaPack() {
  assert(Tok.is(tok::annot_pragma_pack));
  PragmaPackInfo *Info =
    static_cast<PragmaPackInfo *>(Tok.getAnnotationValue());
  SourceLocation PragmaLoc = ConsumeToken();
  ExprResult Alignment;
  if (Info->Alignment.is(tok::numeric_constant)) {
    Alignment = Actions.ActOnNumericConstant(Info->Alignment);
    if (Alignment.isInvalid())
      return;
  }
  Actions.ActOnPragmaPack(Info->Kind, Info->Name, Alignment.get(), PragmaLoc,
                          Info->LParenLoc, Info->RParenLoc);
}

void Parser::HandlePragmaMSStruct() {
  assert(Tok.is(tok::annot_pragma_msstruct));
  Sema::PragmaMSStructKind Kind =
    static_cast<Sema::PragmaMSStructKind>(
    reinterpret_cast<uintptr_t>(Tok.getAnnotationValue()));
  Actions.ActOnPragmaMSStruct(Kind);
  ConsumeToken(); // The annotation token.
}

void Parser::HandlePragmaAlign() {
  assert(Tok.is(tok::annot_pragma_align));
  Sema::PragmaOptionsAlignKind Kind =
    static_cast<Sema::PragmaOptionsAlignKind>(
    reinterpret_cast<uintptr_t>(Tok.getAnnotationValue()));
  SourceLocation PragmaLoc = ConsumeToken();
  Actions.ActOnPragmaOptionsAlign(Kind, PragmaLoc);
}

void Parser::HandlePragmaWeak() {
  assert(Tok.is(tok::annot_pragma_weak));
  SourceLocation PragmaLoc = ConsumeToken();
  Actions.ActOnPragmaWeakID(Tok.getIdentifierInfo(), PragmaLoc,
                            Tok.getLocation());
  ConsumeToken(); // The weak name.
}

void Parser::HandlePragmaWeakAlias() {
  assert(Tok.is(tok::annot_pragma_weakalias));
  SourceLocation PragmaLoc = ConsumeToken();
  IdentifierInfo *WeakName = Tok.getIdentifierInfo();
  SourceLocation WeakNameLoc = Tok.getLocation();
  ConsumeToken();
  IdentifierInfo *AliasName = Tok.getIdentifierInfo();
  SourceLocation AliasNameLoc = Tok.getLocation();
  ConsumeToken();
  Actions.ActOnPragmaWeakAlias(WeakName, AliasName, PragmaLoc,
                               WeakNameLoc, AliasNameLoc);

}

void Parser::HandlePragmaRedefineExtname() {
  assert(Tok.is(tok::annot_pragma_redefine_extname));
  SourceLocation RedefLoc = ConsumeToken();
  IdentifierInfo *RedefName = Tok.getIdentifierInfo();
  SourceLocation RedefNameLoc = Tok.getLocation();
  ConsumeToken();
  IdentifierInfo *AliasName = Tok.getIdentifierInfo();
  SourceLocation AliasNameLoc = Tok.getLocation();
  ConsumeToken();
  Actions.ActOnPragmaRedefineExtname(RedefName, AliasName, RedefLoc,
                                     RedefNameLoc, AliasNameLoc);
}

void Parser::HandlePragmaFPContract() {
  assert(Tok.is(tok::annot_pragma_fp_contract));
  tok::OnOffSwitch OOS =
    static_cast<tok::OnOffSwitch>(
    reinterpret_cast<uintptr_t>(Tok.getAnnotationValue()));
  Actions.ActOnPragmaFPContract(OOS);
  ConsumeToken(); // The annotation token.
}

StmtResult Parser::HandlePragmaCaptured()
{
  assert(Tok.is(tok::annot_pragma_captured));
  ConsumeToken();

  if (Tok.isNot(tok::l_brace)) {
    PP.Diag(Tok, diag::err_expected) << tok::l_brace;
    return StmtError();
  }

  SourceLocation Loc = Tok.getLocation();

  ParseScope CapturedRegionScope(this, Scope::FnScope | Scope::DeclScope);
  Actions.ActOnCapturedRegionStart(Loc, getCurScope(), CR_Default,
                                   /*NumParams=*/1);

  StmtResult R = ParseCompoundStatement();
  CapturedRegionScope.Exit();

  if (R.isInvalid()) {
    Actions.ActOnCapturedRegionError();
    return StmtError();
  }

  return Actions.ActOnCapturedRegionEnd(R.get());
}

namespace {
  typedef llvm::PointerIntPair<IdentifierInfo *, 1, bool> OpenCLExtData;
}

void Parser::HandlePragmaOpenCLExtension() {
  assert(Tok.is(tok::annot_pragma_opencl_extension));
  OpenCLExtData data =
      OpenCLExtData::getFromOpaqueValue(Tok.getAnnotationValue());
  unsigned state = data.getInt();
  IdentifierInfo *ename = data.getPointer();
  SourceLocation NameLoc = Tok.getLocation();
  ConsumeToken(); // The annotation token.

  OpenCLOptions &f = Actions.getOpenCLOptions();
  // OpenCL 1.1 9.1: "The all variant sets the behavior for all extensions,
  // overriding all previously issued extension directives, but only if the
  // behavior is set to disable."
  if (state == 0 && ename->isStr("all")) {
#define OPENCLEXT(nm)   f.nm = 0;
#include "clang/Basic/OpenCLExtensions.def"
  }
#define OPENCLEXT(nm) else if (ename->isStr(#nm)) { f.nm = state; }
#include "clang/Basic/OpenCLExtensions.def"
  else {
    PP.Diag(NameLoc, diag::warn_pragma_unknown_extension) << ename;
    return;
  }
}

void Parser::HandlePragmaMSPointersToMembers() {
  assert(Tok.is(tok::annot_pragma_ms_pointers_to_members));
  LangOptions::PragmaMSPointersToMembersKind RepresentationMethod =
      static_cast<LangOptions::PragmaMSPointersToMembersKind>(
          reinterpret_cast<uintptr_t>(Tok.getAnnotationValue()));
  SourceLocation PragmaLoc = ConsumeToken(); // The annotation token.
  Actions.ActOnPragmaMSPointersToMembers(RepresentationMethod, PragmaLoc);
}

void Parser::HandlePragmaMSVtorDisp() {
  assert(Tok.is(tok::annot_pragma_ms_vtordisp));
  uintptr_t Value = reinterpret_cast<uintptr_t>(Tok.getAnnotationValue());
  Sema::PragmaVtorDispKind Kind =
      static_cast<Sema::PragmaVtorDispKind>((Value >> 16) & 0xFFFF);
  MSVtorDispAttr::Mode Mode = MSVtorDispAttr::Mode(Value & 0xFFFF);
  SourceLocation PragmaLoc = ConsumeToken(); // The annotation token.
  Actions.ActOnPragmaMSVtorDisp(Kind, PragmaLoc, Mode);
}

// #pragma GCC visibility comes in two variants:
//   'push' '(' [visibility] ')'
//   'pop'
void PragmaGCCVisibilityHandler::HandlePragma(Preprocessor &PP, 
                                              PragmaIntroducerKind Introducer,
                                              Token &VisTok) {
  SourceLocation VisLoc = VisTok.getLocation();

  Token Tok;
  PP.LexUnexpandedToken(Tok);

  const IdentifierInfo *PushPop = Tok.getIdentifierInfo();

  const IdentifierInfo *VisType;
  if (PushPop && PushPop->isStr("pop")) {
    VisType = 0;
  } else if (PushPop && PushPop->isStr("push")) {
    PP.LexUnexpandedToken(Tok);
    if (Tok.isNot(tok::l_paren)) {
      PP.Diag(Tok.getLocation(), diag::warn_pragma_expected_lparen)
        << "visibility";
      return;
    }
    PP.LexUnexpandedToken(Tok);
    VisType = Tok.getIdentifierInfo();
    if (!VisType) {
      PP.Diag(Tok.getLocation(), diag::warn_pragma_expected_identifier)
        << "visibility";
      return;
    }
    PP.LexUnexpandedToken(Tok);
    if (Tok.isNot(tok::r_paren)) {
      PP.Diag(Tok.getLocation(), diag::warn_pragma_expected_rparen)
        << "visibility";
      return;
    }
  } else {
    PP.Diag(Tok.getLocation(), diag::warn_pragma_expected_identifier)
      << "visibility";
    return;
  }
  PP.LexUnexpandedToken(Tok);
  if (Tok.isNot(tok::eod)) {
    PP.Diag(Tok.getLocation(), diag::warn_pragma_extra_tokens_at_eol)
      << "visibility";
    return;
  }

  Token *Toks = new Token[1];
  Toks[0].startToken();
  Toks[0].setKind(tok::annot_pragma_vis);
  Toks[0].setLocation(VisLoc);
  Toks[0].setAnnotationValue(
                          const_cast<void*>(static_cast<const void*>(VisType)));
  PP.EnterTokenStream(Toks, 1, /*DisableMacroExpansion=*/true,
                      /*OwnsTokens=*/true);
}

// #pragma pack(...) comes in the following delicious flavors:
//   pack '(' [integer] ')'
//   pack '(' 'show' ')'
//   pack '(' ('push' | 'pop') [',' identifier] [, integer] ')'
void PragmaPackHandler::HandlePragma(Preprocessor &PP, 
                                     PragmaIntroducerKind Introducer,
                                     Token &PackTok) {
  SourceLocation PackLoc = PackTok.getLocation();

  Token Tok;
  PP.Lex(Tok);
  if (Tok.isNot(tok::l_paren)) {
    PP.Diag(Tok.getLocation(), diag::warn_pragma_expected_lparen) << "pack";
    return;
  }

  Sema::PragmaPackKind Kind = Sema::PPK_Default;
  IdentifierInfo *Name = 0;
  Token Alignment;
  Alignment.startToken();
  SourceLocation LParenLoc = Tok.getLocation();
  PP.Lex(Tok);
  if (Tok.is(tok::numeric_constant)) {
    Alignment = Tok;

    PP.Lex(Tok);

    // In MSVC/gcc, #pragma pack(4) sets the alignment without affecting
    // the push/pop stack.
    // In Apple gcc, #pragma pack(4) is equivalent to #pragma pack(push, 4)
    if (PP.getLangOpts().ApplePragmaPack)
      Kind = Sema::PPK_Push;
  } else if (Tok.is(tok::identifier)) {
    const IdentifierInfo *II = Tok.getIdentifierInfo();
    if (II->isStr("show")) {
      Kind = Sema::PPK_Show;
      PP.Lex(Tok);
    } else {
      if (II->isStr("push")) {
        Kind = Sema::PPK_Push;
      } else if (II->isStr("pop")) {
        Kind = Sema::PPK_Pop;
      } else {
        PP.Diag(Tok.getLocation(), diag::warn_pragma_invalid_action) << "pack";
        return;
      }
      PP.Lex(Tok);

      if (Tok.is(tok::comma)) {
        PP.Lex(Tok);

        if (Tok.is(tok::numeric_constant)) {
          Alignment = Tok;

          PP.Lex(Tok);
        } else if (Tok.is(tok::identifier)) {
          Name = Tok.getIdentifierInfo();
          PP.Lex(Tok);

          if (Tok.is(tok::comma)) {
            PP.Lex(Tok);

            if (Tok.isNot(tok::numeric_constant)) {
              PP.Diag(Tok.getLocation(), diag::warn_pragma_pack_malformed);
              return;
            }

            Alignment = Tok;

            PP.Lex(Tok);
          }
        } else {
          PP.Diag(Tok.getLocation(), diag::warn_pragma_pack_malformed);
          return;
        }
      }
    }
  } else if (PP.getLangOpts().ApplePragmaPack) {
    // In MSVC/gcc, #pragma pack() resets the alignment without affecting
    // the push/pop stack.
    // In Apple gcc #pragma pack() is equivalent to #pragma pack(pop).
    Kind = Sema::PPK_Pop;
  }

  if (Tok.isNot(tok::r_paren)) {
    PP.Diag(Tok.getLocation(), diag::warn_pragma_expected_rparen) << "pack";
    return;
  }

  SourceLocation RParenLoc = Tok.getLocation();
  PP.Lex(Tok);
  if (Tok.isNot(tok::eod)) {
    PP.Diag(Tok.getLocation(), diag::warn_pragma_extra_tokens_at_eol) << "pack";
    return;
  }

  PragmaPackInfo *Info = 
    (PragmaPackInfo*) PP.getPreprocessorAllocator().Allocate(
      sizeof(PragmaPackInfo), llvm::alignOf<PragmaPackInfo>());
  new (Info) PragmaPackInfo();
  Info->Kind = Kind;
  Info->Name = Name;
  Info->Alignment = Alignment;
  Info->LParenLoc = LParenLoc;
  Info->RParenLoc = RParenLoc;

  Token *Toks = 
    (Token*) PP.getPreprocessorAllocator().Allocate(
      sizeof(Token) * 1, llvm::alignOf<Token>());
  new (Toks) Token();
  Toks[0].startToken();
  Toks[0].setKind(tok::annot_pragma_pack);
  Toks[0].setLocation(PackLoc);
  Toks[0].setAnnotationValue(static_cast<void*>(Info));
  PP.EnterTokenStream(Toks, 1, /*DisableMacroExpansion=*/true,
                      /*OwnsTokens=*/false);
}

// #pragma ms_struct on
// #pragma ms_struct off
void PragmaMSStructHandler::HandlePragma(Preprocessor &PP, 
                                         PragmaIntroducerKind Introducer,
                                         Token &MSStructTok) {
  Sema::PragmaMSStructKind Kind = Sema::PMSST_OFF;
  
  Token Tok;
  PP.Lex(Tok);
  if (Tok.isNot(tok::identifier)) {
    PP.Diag(Tok.getLocation(), diag::warn_pragma_ms_struct);
    return;
  }
  const IdentifierInfo *II = Tok.getIdentifierInfo();
  if (II->isStr("on")) {
    Kind = Sema::PMSST_ON;
    PP.Lex(Tok);
  }
  else if (II->isStr("off") || II->isStr("reset"))
    PP.Lex(Tok);
  else {
    PP.Diag(Tok.getLocation(), diag::warn_pragma_ms_struct);
    return;
  }
  
  if (Tok.isNot(tok::eod)) {
    PP.Diag(Tok.getLocation(), diag::warn_pragma_extra_tokens_at_eol)
      << "ms_struct";
    return;
  }

  Token *Toks =
    (Token*) PP.getPreprocessorAllocator().Allocate(
      sizeof(Token) * 1, llvm::alignOf<Token>());
  new (Toks) Token();
  Toks[0].startToken();
  Toks[0].setKind(tok::annot_pragma_msstruct);
  Toks[0].setLocation(MSStructTok.getLocation());
  Toks[0].setAnnotationValue(reinterpret_cast<void*>(
                             static_cast<uintptr_t>(Kind)));
  PP.EnterTokenStream(Toks, 1, /*DisableMacroExpansion=*/true,
                      /*OwnsTokens=*/false);
}

// #pragma 'align' '=' {'native','natural','mac68k','power','reset'}
// #pragma 'options 'align' '=' {'native','natural','mac68k','power','reset'}
static void ParseAlignPragma(Preprocessor &PP, Token &FirstTok,
                             bool IsOptions) {
  Token Tok;

  if (IsOptions) {
    PP.Lex(Tok);
    if (Tok.isNot(tok::identifier) ||
        !Tok.getIdentifierInfo()->isStr("align")) {
      PP.Diag(Tok.getLocation(), diag::warn_pragma_options_expected_align);
      return;
    }
  }

  PP.Lex(Tok);
  if (Tok.isNot(tok::equal)) {
    PP.Diag(Tok.getLocation(), diag::warn_pragma_align_expected_equal)
      << IsOptions;
    return;
  }

  PP.Lex(Tok);
  if (Tok.isNot(tok::identifier)) {
    PP.Diag(Tok.getLocation(), diag::warn_pragma_expected_identifier)
      << (IsOptions ? "options" : "align");
    return;
  }

  Sema::PragmaOptionsAlignKind Kind = Sema::POAK_Natural;
  const IdentifierInfo *II = Tok.getIdentifierInfo();
  if (II->isStr("native"))
    Kind = Sema::POAK_Native;
  else if (II->isStr("natural"))
    Kind = Sema::POAK_Natural;
  else if (II->isStr("packed"))
    Kind = Sema::POAK_Packed;
  else if (II->isStr("power"))
    Kind = Sema::POAK_Power;
  else if (II->isStr("mac68k"))
    Kind = Sema::POAK_Mac68k;
  else if (II->isStr("reset"))
    Kind = Sema::POAK_Reset;
  else {
    PP.Diag(Tok.getLocation(), diag::warn_pragma_align_invalid_option)
      << IsOptions;
    return;
  }

  PP.Lex(Tok);
  if (Tok.isNot(tok::eod)) {
    PP.Diag(Tok.getLocation(), diag::warn_pragma_extra_tokens_at_eol)
      << (IsOptions ? "options" : "align");
    return;
  }

  Token *Toks =
    (Token*) PP.getPreprocessorAllocator().Allocate(
      sizeof(Token) * 1, llvm::alignOf<Token>());
  new (Toks) Token();
  Toks[0].startToken();
  Toks[0].setKind(tok::annot_pragma_align);
  Toks[0].setLocation(FirstTok.getLocation());
  Toks[0].setAnnotationValue(reinterpret_cast<void*>(
                             static_cast<uintptr_t>(Kind)));
  PP.EnterTokenStream(Toks, 1, /*DisableMacroExpansion=*/true,
                      /*OwnsTokens=*/false);
}

void PragmaAlignHandler::HandlePragma(Preprocessor &PP, 
                                      PragmaIntroducerKind Introducer,
                                      Token &AlignTok) {
  ParseAlignPragma(PP, AlignTok, /*IsOptions=*/false);
}

void PragmaOptionsHandler::HandlePragma(Preprocessor &PP, 
                                        PragmaIntroducerKind Introducer,
                                        Token &OptionsTok) {
  ParseAlignPragma(PP, OptionsTok, /*IsOptions=*/true);
}

// #pragma unused(identifier)
void PragmaUnusedHandler::HandlePragma(Preprocessor &PP, 
                                       PragmaIntroducerKind Introducer,
                                       Token &UnusedTok) {
  // FIXME: Should we be expanding macros here? My guess is no.
  SourceLocation UnusedLoc = UnusedTok.getLocation();

  // Lex the left '('.
  Token Tok;
  PP.Lex(Tok);
  if (Tok.isNot(tok::l_paren)) {
    PP.Diag(Tok.getLocation(), diag::warn_pragma_expected_lparen) << "unused";
    return;
  }

  // Lex the declaration reference(s).
  SmallVector<Token, 5> Identifiers;
  SourceLocation RParenLoc;
  bool LexID = true;

  while (true) {
    PP.Lex(Tok);

    if (LexID) {
      if (Tok.is(tok::identifier)) {
        Identifiers.push_back(Tok);
        LexID = false;
        continue;
      }

      // Illegal token!
      PP.Diag(Tok.getLocation(), diag::warn_pragma_unused_expected_var);
      return;
    }

    // We are execting a ')' or a ','.
    if (Tok.is(tok::comma)) {
      LexID = true;
      continue;
    }

    if (Tok.is(tok::r_paren)) {
      RParenLoc = Tok.getLocation();
      break;
    }

    // Illegal token!
    PP.Diag(Tok.getLocation(), diag::warn_pragma_expected_punc) << "unused";
    return;
  }

  PP.Lex(Tok);
  if (Tok.isNot(tok::eod)) {
    PP.Diag(Tok.getLocation(), diag::warn_pragma_extra_tokens_at_eol) <<
        "unused";
    return;
  }

  // Verify that we have a location for the right parenthesis.
  assert(RParenLoc.isValid() && "Valid '#pragma unused' must have ')'");
  assert(!Identifiers.empty() && "Valid '#pragma unused' must have arguments");

  // For each identifier token, insert into the token stream a
  // annot_pragma_unused token followed by the identifier token.
  // This allows us to cache a "#pragma unused" that occurs inside an inline
  // C++ member function.

  Token *Toks = 
    (Token*) PP.getPreprocessorAllocator().Allocate(
      sizeof(Token) * 2 * Identifiers.size(), llvm::alignOf<Token>());
  for (unsigned i=0; i != Identifiers.size(); i++) {
    Token &pragmaUnusedTok = Toks[2*i], &idTok = Toks[2*i+1];
    pragmaUnusedTok.startToken();
    pragmaUnusedTok.setKind(tok::annot_pragma_unused);
    pragmaUnusedTok.setLocation(UnusedLoc);
    idTok = Identifiers[i];
  }
  PP.EnterTokenStream(Toks, 2*Identifiers.size(),
                      /*DisableMacroExpansion=*/true, /*OwnsTokens=*/false);
}

// #pragma weak identifier
// #pragma weak identifier '=' identifier
void PragmaWeakHandler::HandlePragma(Preprocessor &PP, 
                                     PragmaIntroducerKind Introducer,
                                     Token &WeakTok) {
  SourceLocation WeakLoc = WeakTok.getLocation();

  Token Tok;
  PP.Lex(Tok);
  if (Tok.isNot(tok::identifier)) {
    PP.Diag(Tok.getLocation(), diag::warn_pragma_expected_identifier) << "weak";
    return;
  }

  Token WeakName = Tok;
  bool HasAlias = false;
  Token AliasName;

  PP.Lex(Tok);
  if (Tok.is(tok::equal)) {
    HasAlias = true;
    PP.Lex(Tok);
    if (Tok.isNot(tok::identifier)) {
      PP.Diag(Tok.getLocation(), diag::warn_pragma_expected_identifier)
          << "weak";
      return;
    }
    AliasName = Tok;
    PP.Lex(Tok);
  }

  if (Tok.isNot(tok::eod)) {
    PP.Diag(Tok.getLocation(), diag::warn_pragma_extra_tokens_at_eol) << "weak";
    return;
  }

  if (HasAlias) {
    Token *Toks = 
      (Token*) PP.getPreprocessorAllocator().Allocate(
        sizeof(Token) * 3, llvm::alignOf<Token>());
    Token &pragmaUnusedTok = Toks[0];
    pragmaUnusedTok.startToken();
    pragmaUnusedTok.setKind(tok::annot_pragma_weakalias);
    pragmaUnusedTok.setLocation(WeakLoc);
    Toks[1] = WeakName;
    Toks[2] = AliasName;
    PP.EnterTokenStream(Toks, 3,
                        /*DisableMacroExpansion=*/true, /*OwnsTokens=*/false);
  } else {
    Token *Toks = 
      (Token*) PP.getPreprocessorAllocator().Allocate(
        sizeof(Token) * 2, llvm::alignOf<Token>());
    Token &pragmaUnusedTok = Toks[0];
    pragmaUnusedTok.startToken();
    pragmaUnusedTok.setKind(tok::annot_pragma_weak);
    pragmaUnusedTok.setLocation(WeakLoc);
    Toks[1] = WeakName;
    PP.EnterTokenStream(Toks, 2,
                        /*DisableMacroExpansion=*/true, /*OwnsTokens=*/false);
  }
}

// #pragma redefine_extname identifier identifier
void PragmaRedefineExtnameHandler::HandlePragma(Preprocessor &PP, 
                                               PragmaIntroducerKind Introducer,
                                                Token &RedefToken) {
  SourceLocation RedefLoc = RedefToken.getLocation();

  Token Tok;
  PP.Lex(Tok);
  if (Tok.isNot(tok::identifier)) {
    PP.Diag(Tok.getLocation(), diag::warn_pragma_expected_identifier) <<
      "redefine_extname";
    return;
  }

  Token RedefName = Tok;
  PP.Lex(Tok);

  if (Tok.isNot(tok::identifier)) {
    PP.Diag(Tok.getLocation(), diag::warn_pragma_expected_identifier)
        << "redefine_extname";
    return;
  }

  Token AliasName = Tok;
  PP.Lex(Tok);

  if (Tok.isNot(tok::eod)) {
    PP.Diag(Tok.getLocation(), diag::warn_pragma_extra_tokens_at_eol) <<
      "redefine_extname";
    return;
  }

  Token *Toks = 
    (Token*) PP.getPreprocessorAllocator().Allocate(
      sizeof(Token) * 3, llvm::alignOf<Token>());
  Token &pragmaRedefTok = Toks[0];
  pragmaRedefTok.startToken();
  pragmaRedefTok.setKind(tok::annot_pragma_redefine_extname);
  pragmaRedefTok.setLocation(RedefLoc);
  Toks[1] = RedefName;
  Toks[2] = AliasName;
  PP.EnterTokenStream(Toks, 3,
                      /*DisableMacroExpansion=*/true, /*OwnsTokens=*/false);
}


void
PragmaFPContractHandler::HandlePragma(Preprocessor &PP, 
                                      PragmaIntroducerKind Introducer,
                                      Token &Tok) {
  tok::OnOffSwitch OOS;
  if (PP.LexOnOffSwitch(OOS))
    return;

  Token *Toks =
    (Token*) PP.getPreprocessorAllocator().Allocate(
      sizeof(Token) * 1, llvm::alignOf<Token>());
  new (Toks) Token();
  Toks[0].startToken();
  Toks[0].setKind(tok::annot_pragma_fp_contract);
  Toks[0].setLocation(Tok.getLocation());
  Toks[0].setAnnotationValue(reinterpret_cast<void*>(
                             static_cast<uintptr_t>(OOS)));
  PP.EnterTokenStream(Toks, 1, /*DisableMacroExpansion=*/true,
                      /*OwnsTokens=*/false);
}

void 
PragmaOpenCLExtensionHandler::HandlePragma(Preprocessor &PP, 
                                           PragmaIntroducerKind Introducer,
                                           Token &Tok) {
  PP.LexUnexpandedToken(Tok);
  if (Tok.isNot(tok::identifier)) {
    PP.Diag(Tok.getLocation(), diag::warn_pragma_expected_identifier) <<
      "OPENCL";
    return;
  }
  IdentifierInfo *ename = Tok.getIdentifierInfo();
  SourceLocation NameLoc = Tok.getLocation();

  PP.Lex(Tok);
  if (Tok.isNot(tok::colon)) {
    PP.Diag(Tok.getLocation(), diag::warn_pragma_expected_colon) << ename;
    return;
  }

  PP.Lex(Tok);
  if (Tok.isNot(tok::identifier)) {
    PP.Diag(Tok.getLocation(), diag::warn_pragma_expected_enable_disable);
    return;
  }
  IdentifierInfo *op = Tok.getIdentifierInfo();

  unsigned state;
  if (op->isStr("enable")) {
    state = 1;
  } else if (op->isStr("disable")) {
    state = 0;
  } else {
    PP.Diag(Tok.getLocation(), diag::warn_pragma_expected_enable_disable);
    return;
  }
  SourceLocation StateLoc = Tok.getLocation();

  PP.Lex(Tok);
  if (Tok.isNot(tok::eod)) {
    PP.Diag(Tok.getLocation(), diag::warn_pragma_extra_tokens_at_eol) <<
      "OPENCL EXTENSION";
    return;
  }

  OpenCLExtData data(ename, state);
  Token *Toks =
    (Token*) PP.getPreprocessorAllocator().Allocate(
      sizeof(Token) * 1, llvm::alignOf<Token>());
  new (Toks) Token();
  Toks[0].startToken();
  Toks[0].setKind(tok::annot_pragma_opencl_extension);
  Toks[0].setLocation(NameLoc);
  Toks[0].setAnnotationValue(data.getOpaqueValue());
  PP.EnterTokenStream(Toks, 1, /*DisableMacroExpansion=*/true,
                      /*OwnsTokens=*/false);

  if (PP.getPPCallbacks())
    PP.getPPCallbacks()->PragmaOpenCLExtension(NameLoc, ename, 
                                               StateLoc, state);
}

/// \brief Handle '#pragma omp ...' when OpenMP is disabled.
///
void
PragmaNoOpenMPHandler::HandlePragma(Preprocessor &PP,
                                    PragmaIntroducerKind Introducer,
                                    Token &FirstTok) {
  if (PP.getDiagnostics().getDiagnosticLevel(diag::warn_pragma_omp_ignored,
                                             FirstTok.getLocation()) !=
      DiagnosticsEngine::Ignored) {
    PP.Diag(FirstTok, diag::warn_pragma_omp_ignored);
    PP.getDiagnostics().setDiagnosticMapping(diag::warn_pragma_omp_ignored,
                                             diag::MAP_IGNORE,
                                             SourceLocation());
  }
  PP.DiscardUntilEndOfDirective();
}

/// \brief Handle '#pragma omp ...' when OpenMP is enabled.
///
void
PragmaOpenMPHandler::HandlePragma(Preprocessor &PP,
                                  PragmaIntroducerKind Introducer,
                                  Token &FirstTok) {
  SmallVector<Token, 16> Pragma;
  Token Tok;
  Tok.startToken();
  Tok.setKind(tok::annot_pragma_openmp);
  Tok.setLocation(FirstTok.getLocation());

  while (Tok.isNot(tok::eod)) {
    Pragma.push_back(Tok);
    PP.Lex(Tok);
  }
  SourceLocation EodLoc = Tok.getLocation();
  Tok.startToken();
  Tok.setKind(tok::annot_pragma_openmp_end);
  Tok.setLocation(EodLoc);
  Pragma.push_back(Tok);

  Token *Toks = new Token[Pragma.size()];
  std::copy(Pragma.begin(), Pragma.end(), Toks);
  PP.EnterTokenStream(Toks, Pragma.size(),
                      /*DisableMacroExpansion=*/true, /*OwnsTokens=*/true);
}

/// \brief Handle '#pragma pointers_to_members'
// The grammar for this pragma is as follows:
//
// <inheritance model> ::= ('single' | 'multiple' | 'virtual') '_inheritance'
//
// #pragma pointers_to_members '(' 'best_case' ')'
// #pragma pointers_to_members '(' 'full_generality' [',' inheritance-model] ')'
// #pragma pointers_to_members '(' inheritance-model ')'
void PragmaMSPointersToMembers::HandlePragma(Preprocessor &PP,
                                             PragmaIntroducerKind Introducer,
                                             Token &Tok) {
  SourceLocation PointersToMembersLoc = Tok.getLocation();
  PP.Lex(Tok);
  if (Tok.isNot(tok::l_paren)) {
    PP.Diag(PointersToMembersLoc, diag::warn_pragma_expected_lparen)
      << "pointers_to_members";
    return;
  }
  PP.Lex(Tok);
  const IdentifierInfo *Arg = Tok.getIdentifierInfo();
  if (!Arg) {
    PP.Diag(Tok.getLocation(), diag::warn_pragma_expected_identifier)
      << "pointers_to_members";
    return;
  }
  PP.Lex(Tok);

  LangOptions::PragmaMSPointersToMembersKind RepresentationMethod;
  if (Arg->isStr("best_case")) {
    RepresentationMethod = LangOptions::PPTMK_BestCase;
  } else {
    if (Arg->isStr("full_generality")) {
      if (Tok.is(tok::comma)) {
        PP.Lex(Tok);

        Arg = Tok.getIdentifierInfo();
        if (!Arg) {
          PP.Diag(Tok.getLocation(),
                  diag::err_pragma_pointers_to_members_unknown_kind)
              << Tok.getKind() << /*OnlyInheritanceModels*/ 0;
          return;
        }
        PP.Lex(Tok);
      } else if (Tok.is(tok::r_paren)) {
        // #pragma pointers_to_members(full_generality) implicitly specifies
        // virtual_inheritance.
        Arg = 0;
        RepresentationMethod = LangOptions::PPTMK_FullGeneralityVirtualInheritance;
      } else {
        PP.Diag(Tok.getLocation(), diag::err_expected_punc)
            << "full_generality";
        return;
      }
    }

    if (Arg) {
      if (Arg->isStr("single_inheritance")) {
        RepresentationMethod =
            LangOptions::PPTMK_FullGeneralitySingleInheritance;
      } else if (Arg->isStr("multiple_inheritance")) {
        RepresentationMethod =
            LangOptions::PPTMK_FullGeneralityMultipleInheritance;
      } else if (Arg->isStr("virtual_inheritance")) {
        RepresentationMethod =
            LangOptions::PPTMK_FullGeneralityVirtualInheritance;
      } else {
        PP.Diag(Tok.getLocation(),
                diag::err_pragma_pointers_to_members_unknown_kind)
            << Arg << /*HasPointerDeclaration*/ 1;
        return;
      }
    }
  }

  if (Tok.isNot(tok::r_paren)) {
    PP.Diag(Tok.getLocation(), diag::err_expected_rparen_after)
        << (Arg ? Arg->getName() : "full_generality");
    return;
  }

  PP.Lex(Tok);
  if (Tok.isNot(tok::eod)) {
    PP.Diag(Tok.getLocation(), diag::warn_pragma_extra_tokens_at_eol)
      << "pointers_to_members";
    return;
  }

  Token AnnotTok;
  AnnotTok.startToken();
  AnnotTok.setKind(tok::annot_pragma_ms_pointers_to_members);
  AnnotTok.setLocation(PointersToMembersLoc);
  AnnotTok.setAnnotationValue(
      reinterpret_cast<void *>(static_cast<uintptr_t>(RepresentationMethod)));
  PP.EnterToken(AnnotTok);
}

/// \brief Handle '#pragma vtordisp'
// The grammar for this pragma is as follows:
//
// <vtordisp-mode> ::= ('off' | 'on' | '0' | '1' | '2' )
//
// #pragma vtordisp '(' ['push' ','] vtordisp-mode ')'
// #pragma vtordisp '(' 'pop' ')'
// #pragma vtordisp '(' ')'
void PragmaMSVtorDisp::HandlePragma(Preprocessor &PP,
                                    PragmaIntroducerKind Introducer,
                                    Token &Tok) {
  SourceLocation VtorDispLoc = Tok.getLocation();
  PP.Lex(Tok);
  if (Tok.isNot(tok::l_paren)) {
    PP.Diag(VtorDispLoc, diag::warn_pragma_expected_lparen) << "vtordisp";
    return;
  }
  PP.Lex(Tok);

  Sema::PragmaVtorDispKind Kind = Sema::PVDK_Set;
  const IdentifierInfo *II = Tok.getIdentifierInfo();
  if (II) {
    if (II->isStr("push")) {
      // #pragma vtordisp(push, mode)
      PP.Lex(Tok);
      if (Tok.isNot(tok::comma)) {
        PP.Diag(VtorDispLoc, diag::warn_pragma_expected_punc) << "vtordisp";
        return;
      }
      PP.Lex(Tok);
      Kind = Sema::PVDK_Push;
      // not push, could be on/off
    } else if (II->isStr("pop")) {
      // #pragma vtordisp(pop)
      PP.Lex(Tok);
      Kind = Sema::PVDK_Pop;
    }
    // not push or pop, could be on/off
  } else {
    if (Tok.is(tok::r_paren)) {
      // #pragma vtordisp()
      Kind = Sema::PVDK_Reset;
    }
  }


  uint64_t Value = 0;
  if (Kind == Sema::PVDK_Push || Kind == Sema::PVDK_Set) {
    const IdentifierInfo *II = Tok.getIdentifierInfo();
    if (II && II->isStr("off")) {
      PP.Lex(Tok);
      Value = 0;
    } else if (II && II->isStr("on")) {
      PP.Lex(Tok);
      Value = 1;
    } else if (Tok.is(tok::numeric_constant) &&
               PP.parseSimpleIntegerLiteral(Tok, Value)) {
      if (Value > 2) {
        PP.Diag(Tok.getLocation(), diag::warn_pragma_expected_integer)
            << 0 << 2 << "vtordisp";
        return;
      }
    } else {
      PP.Diag(Tok.getLocation(), diag::warn_pragma_invalid_action)
          << "vtordisp";
      return;
    }
  }

  // Finish the pragma: ')' $
  if (Tok.isNot(tok::r_paren)) {
    PP.Diag(VtorDispLoc, diag::warn_pragma_expected_rparen) << "vtordisp";
    return;
  }
  PP.Lex(Tok);
  if (Tok.isNot(tok::eod)) {
    PP.Diag(Tok.getLocation(), diag::warn_pragma_extra_tokens_at_eol)
        << "vtordisp";
    return;
  }

  // Enter the annotation.
  Token AnnotTok;
  AnnotTok.startToken();
  AnnotTok.setKind(tok::annot_pragma_ms_vtordisp);
  AnnotTok.setLocation(VtorDispLoc);
  AnnotTok.setAnnotationValue(reinterpret_cast<void *>(
      static_cast<uintptr_t>((Kind << 16) | (Value & 0xFFFF))));
  PP.EnterToken(AnnotTok);
}

/// \brief Handle the Microsoft \#pragma detect_mismatch extension.
///
/// The syntax is:
/// \code
///   #pragma detect_mismatch("name", "value")
/// \endcode
/// Where 'name' and 'value' are quoted strings.  The values are embedded in
/// the object file and passed along to the linker.  If the linker detects a
/// mismatch in the object file's values for the given name, a LNK2038 error
/// is emitted.  See MSDN for more details.
void PragmaDetectMismatchHandler::HandlePragma(Preprocessor &PP,
                                               PragmaIntroducerKind Introducer,
                                               Token &Tok) {
  SourceLocation CommentLoc = Tok.getLocation();
  PP.Lex(Tok);
  if (Tok.isNot(tok::l_paren)) {
    PP.Diag(CommentLoc, diag::err_expected) << tok::l_paren;
    return;
  }

  // Read the name to embed, which must be a string literal.
  std::string NameString;
  if (!PP.LexStringLiteral(Tok, NameString,
                           "pragma detect_mismatch",
                           /*MacroExpansion=*/true))
    return;

  // Read the comma followed by a second string literal.
  std::string ValueString;
  if (Tok.isNot(tok::comma)) {
    PP.Diag(Tok.getLocation(), diag::err_pragma_detect_mismatch_malformed);
    return;
  }

  if (!PP.LexStringLiteral(Tok, ValueString, "pragma detect_mismatch",
                           /*MacroExpansion=*/true))
    return;

  if (Tok.isNot(tok::r_paren)) {
    PP.Diag(Tok.getLocation(), diag::err_expected) << tok::r_paren;
    return;
  }
  PP.Lex(Tok);  // Eat the r_paren.

  if (Tok.isNot(tok::eod)) {
    PP.Diag(Tok.getLocation(), diag::err_pragma_detect_mismatch_malformed);
    return;
  }

  // If the pragma is lexically sound, notify any interested PPCallbacks.
  if (PP.getPPCallbacks())
    PP.getPPCallbacks()->PragmaDetectMismatch(CommentLoc, NameString,
                                              ValueString);

  Actions.ActOnPragmaDetectMismatch(NameString, ValueString);
}

/// \brief Handle the microsoft \#pragma comment extension.
///
/// The syntax is:
/// \code
///   #pragma comment(linker, "foo")
/// \endcode
/// 'linker' is one of five identifiers: compiler, exestr, lib, linker, user.
/// "foo" is a string, which is fully macro expanded, and permits string
/// concatenation, embedded escape characters etc.  See MSDN for more details.
void PragmaCommentHandler::HandlePragma(Preprocessor &PP,
                                        PragmaIntroducerKind Introducer,
                                        Token &Tok) {
  SourceLocation CommentLoc = Tok.getLocation();
  PP.Lex(Tok);
  if (Tok.isNot(tok::l_paren)) {
    PP.Diag(CommentLoc, diag::err_pragma_comment_malformed);
    return;
  }

  // Read the identifier.
  PP.Lex(Tok);
  if (Tok.isNot(tok::identifier)) {
    PP.Diag(CommentLoc, diag::err_pragma_comment_malformed);
    return;
  }

  // Verify that this is one of the 5 whitelisted options.
  IdentifierInfo *II = Tok.getIdentifierInfo();
  Sema::PragmaMSCommentKind Kind =
    llvm::StringSwitch<Sema::PragmaMSCommentKind>(II->getName())
    .Case("linker",   Sema::PCK_Linker)
    .Case("lib",      Sema::PCK_Lib)
    .Case("compiler", Sema::PCK_Compiler)
    .Case("exestr",   Sema::PCK_ExeStr)
    .Case("user",     Sema::PCK_User)
    .Default(Sema::PCK_Unknown);
  if (Kind == Sema::PCK_Unknown) {
    PP.Diag(Tok.getLocation(), diag::err_pragma_comment_unknown_kind);
    return;
  }

  // Read the optional string if present.
  PP.Lex(Tok);
  std::string ArgumentString;
  if (Tok.is(tok::comma) && !PP.LexStringLiteral(Tok, ArgumentString,
                                                 "pragma comment",
                                                 /*MacroExpansion=*/true))
    return;

  // FIXME: warn that 'exestr' is deprecated.
  // FIXME: If the kind is "compiler" warn if the string is present (it is
  // ignored).
  // The MSDN docs say that "lib" and "linker" require a string and have a short
  // whitelist of linker options they support, but in practice MSVC doesn't
  // issue a diagnostic.  Therefore neither does clang.

  if (Tok.isNot(tok::r_paren)) {
    PP.Diag(Tok.getLocation(), diag::err_pragma_comment_malformed);
    return;
  }
  PP.Lex(Tok);  // eat the r_paren.

  if (Tok.isNot(tok::eod)) {
    PP.Diag(Tok.getLocation(), diag::err_pragma_comment_malformed);
    return;
  }

  // If the pragma is lexically sound, notify any interested PPCallbacks.
  if (PP.getPPCallbacks())
    PP.getPPCallbacks()->PragmaComment(CommentLoc, II, ArgumentString);

  Actions.ActOnPragmaMSComment(Kind, ArgumentString);
}