C++ SmallString::data方法代码示例

/// Determine whether the given text matches a property name.
static bool textMatchesPropertyName(StringRef text,
                                    const InheritedNameSet *allPropertyNames) {
  if (!allPropertyNames) return false;

  SmallString<16> localScratch;
  auto name = camel_case::toLowercaseWord(text, localScratch);

  // A property with exactly this name.
  if (allPropertyNames->contains(name)) return true;

  // From here on, we'll be working with scratch space.
  if (name.data() != localScratch.data())
    localScratch = name;

  if (localScratch.back() == 'y') {
    // If the last letter is a 'y', try 'ies'.
    localScratch.pop_back();
    localScratch += "ies";
    if (allPropertyNames->contains(localScratch)) return true;
  } else {
    // Otherwise, add an 's' and try again.
    localScratch += 's';
    if (allPropertyNames->contains(localScratch)) return true;

    // Alternatively, try to add 'es'.
    localScratch.pop_back();
    localScratch += "es";
    if (allPropertyNames->contains(localScratch)) return true;
  }

  return false;
}

static void PrintHeaderInfo(raw_ostream *OutputFile, const char* Filename,
                            bool ShowDepth, unsigned CurrentIncludeDepth,
                            bool MSStyle) {
    // Write to a temporary string to avoid unnecessary flushing on errs().
    SmallString<512> Pathname(Filename);
    if (!MSStyle)
      Lexer::Stringify(Pathname);

    SmallString<256> Msg;
    if (MSStyle)
      Msg += "Note: including file:";

    if (ShowDepth) {
      // The main source file is at depth 1, so skip one dot.
      for (unsigned i = 1; i != CurrentIncludeDepth; ++i)
        Msg += MSStyle ? ' ' : '.';

      if (!MSStyle)
        Msg += ' ';
    }
    Msg += Pathname;
    Msg += '\n';

    OutputFile->write(Msg.data(), Msg.size());
    OutputFile->flush();
}

void HeaderIncludesCallback::FileChanged(SourceLocation Loc,
                                         FileChangeReason Reason,
                                       SrcMgr::CharacteristicKind NewFileType,
                                       FileID PrevFID) {
  // Unless we are exiting a #include, make sure to skip ahead to the line the
  // #include directive was at.
  PresumedLoc UserLoc = SM.getPresumedLoc(Loc);
  if (UserLoc.isInvalid())
    return;

  // Adjust the current include depth.
  if (Reason == PPCallbacks::EnterFile) {
    ++CurrentIncludeDepth;
  } else if (Reason == PPCallbacks::ExitFile) {
    if (CurrentIncludeDepth)
      --CurrentIncludeDepth;

    // We track when we are done with the predefines by watching for the first
    // place where we drop back to a nesting depth of 1.
    if (CurrentIncludeDepth == 1 && !HasProcessedPredefines)
      HasProcessedPredefines = true;

    return;
  } else
    return;

  // Show the header if we are (a) past the predefines, or (b) showing all
  // headers and in the predefines at a depth past the initial file and command
  // line buffers.
  bool ShowHeader = (HasProcessedPredefines ||
                     (ShowAllHeaders && CurrentIncludeDepth > 2));

  // Dump the header include information we are past the predefines buffer or
  // are showing all headers.
  if (ShowHeader && Reason == PPCallbacks::EnterFile) {
    // Write to a temporary string to avoid unnecessary flushing on errs().
    SmallString<512> Filename(UserLoc.getFilename());
    if (!MSStyle)
      Lexer::Stringify(Filename);

    SmallString<256> Msg;
    if (MSStyle)
      Msg += "Note: including file:";

    if (ShowDepth) {
      // The main source file is at depth 1, so skip one dot.
      for (unsigned i = 1; i != CurrentIncludeDepth; ++i)
        Msg += MSStyle ? ' ' : '.';

      if (!MSStyle)
        Msg += ' ';
    }
    Msg += Filename;
    Msg += '\n';

    OutputFile->write(Msg.data(), Msg.size());
    OutputFile->flush();
  }
}

void Value::setName(const Twine &NewName) {
  // Fast path for common IRBuilder case of setName("") when there is no name.
  if (NewName.isTriviallyEmpty() && !hasName())
    return;

  SmallString<256> NameData;
  NewName.toVector(NameData);

  const char *NameStr = NameData.data();
  unsigned NameLen = NameData.size();

  // Name isn't changing?
  if (getName() == StringRef(NameStr, NameLen))
    return;

  assert(getType() != Type::getVoidTy(getContext()) &&
         "Cannot assign a name to void values!");

  // Get the symbol table to update for this object.
  ValueSymbolTable *ST;
  if (getSymTab(this, ST))
    return;  // Cannot set a name on this value (e.g. constant).

  if (!ST) { // No symbol table to update?  Just do the change.
    if (NameLen == 0) {
      // Free the name for this value.
      Name->Destroy();
      Name = 0;
      return;
    }

    if (Name)
      Name->Destroy();

    // NOTE: Could optimize for the case the name is shrinking to not deallocate
    // then reallocated.

    // Create the new name.
    Name = ValueName::Create(NameStr, NameStr+NameLen);
    Name->setValue(this);
    return;
  }

  // NOTE: Could optimize for the case the name is shrinking to not deallocate
  // then reallocated.
  if (hasName()) {
    // Remove old name.
    ST->removeValueName(Name);
    Name->Destroy();
    Name = 0;

    if (NameLen == 0)
      return;
  }

  // Name is changing to something new.
  Name = ST->createValueName(StringRef(NameStr, NameLen), this);
}

void verifyEncoding(MCDwarfLineTableParams Params, int LineDelta, int AddrDelta,
                    ArrayRef<uint8_t> ExpectedEncoding) {
  SmallString<16> Buffer;
  raw_svector_ostream EncodingOS(Buffer);
  MCDwarfLineAddr::Encode(getContext(), Params, LineDelta, AddrDelta,
                          EncodingOS);
  ArrayRef<uint8_t> Encoding(reinterpret_cast<uint8_t *>(Buffer.data()),
                             Buffer.size());
  EXPECT_EQ(ExpectedEncoding, Encoding);
}

void ObjCMigrateASTConsumer::HandleTranslationUnit(ASTContext &Ctx) {
  
  TranslationUnitDecl *TU = Ctx.getTranslationUnitDecl();
  if (MigrateProperty)
    for (DeclContext::decl_iterator D = TU->decls_begin(), DEnd = TU->decls_end();
         D != DEnd; ++D) {
      if (ObjCInterfaceDecl *CDecl = dyn_cast<ObjCInterfaceDecl>(*D))
        migrateObjCInterfaceDecl(Ctx, CDecl);
      else if (ObjCProtocolDecl *PDecl = dyn_cast<ObjCProtocolDecl>(*D))
        ObjCProtocolDecls.insert(PDecl);
      else if (const ObjCImplementationDecl *ImpDecl =
               dyn_cast<ObjCImplementationDecl>(*D))
        migrateProtocolConformance(Ctx, ImpDecl);
      else if (const EnumDecl *ED = dyn_cast<EnumDecl>(*D)) {
        DeclContext::decl_iterator N = D;
        ++N;
        if (N != DEnd)
          if (const TypedefDecl *TD = dyn_cast<TypedefDecl>(*N))
            migrateNSEnumDecl(Ctx, ED, TD);
      }
      // migrate methods which can have instancetype as their result type.
      if (ObjCContainerDecl *CDecl = dyn_cast<ObjCContainerDecl>(*D))
        migrateInstanceType(Ctx, CDecl);
    }
  
  Rewriter rewriter(Ctx.getSourceManager(), Ctx.getLangOpts());
  RewritesReceiver Rec(rewriter);
  Editor->applyRewrites(Rec);

  for (Rewriter::buffer_iterator
        I = rewriter.buffer_begin(), E = rewriter.buffer_end(); I != E; ++I) {
    FileID FID = I->first;
    RewriteBuffer &buf = I->second;
    const FileEntry *file = Ctx.getSourceManager().getFileEntryForID(FID);
    assert(file);
    SmallString<512> newText;
    llvm::raw_svector_ostream vecOS(newText);
    buf.write(vecOS);
    vecOS.flush();
    llvm::MemoryBuffer *memBuf = llvm::MemoryBuffer::getMemBufferCopy(
                   StringRef(newText.data(), newText.size()), file->getName());
    SmallString<64> filePath(file->getName());
    FileMgr.FixupRelativePath(filePath);
    Remapper.remap(filePath.str(), memBuf);
  }

  if (IsOutputFile) {
    Remapper.flushToFile(MigrateDir, Ctx.getDiagnostics());
  } else {
    Remapper.flushToDisk(MigrateDir, Ctx.getDiagnostics());
  }
}

bool MigrationProcess::applyTransform(TransformFn trans,
                                      RewriteListener *listener) {
  OwningPtr<CompilerInvocation> CInvok;
  CInvok.reset(createInvocationForMigration(OrigCI));
  CInvok->getDiagnosticOpts().IgnoreWarnings = true;

  Remapper.applyMappings(CInvok->getPreprocessorOpts());

  CapturedDiagList capturedDiags;
  std::vector<SourceLocation> ARCMTMacroLocs;

  assert(DiagClient);
  IntrusiveRefCntPtr<DiagnosticIDs> DiagID(new DiagnosticIDs());
  IntrusiveRefCntPtr<DiagnosticsEngine> Diags(
      new DiagnosticsEngine(DiagID, DiagClient, /*ShouldOwnClient=*/false));

  // Filter of all diagnostics.
  CaptureDiagnosticConsumer errRec(*Diags, capturedDiags);
  Diags->setClient(&errRec, /*ShouldOwnClient=*/false);

  OwningPtr<ARCMTMacroTrackerAction> ASTAction;
  ASTAction.reset(new ARCMTMacroTrackerAction(ARCMTMacroLocs));

  OwningPtr<ASTUnit> Unit(
      ASTUnit::LoadFromCompilerInvocationAction(CInvok.take(), Diags,
                                                ASTAction.get()));
  if (!Unit)
    return true;
  Unit->setOwnsRemappedFileBuffers(false); // FileRemapper manages that.

  // Don't filter diagnostics anymore.
  Diags->setClient(DiagClient, /*ShouldOwnClient=*/false);

  ASTContext &Ctx = Unit->getASTContext();

  if (Diags->hasFatalErrorOccurred()) {
    Diags->Reset();
    DiagClient->BeginSourceFile(Ctx.getLangOpts(), &Unit->getPreprocessor());
    capturedDiags.reportDiagnostics(*Diags);
    DiagClient->EndSourceFile();
    return true;
  }

  // After parsing of source files ended, we want to reuse the
  // diagnostics objects to emit further diagnostics.
  // We call BeginSourceFile because DiagnosticConsumer requires that 
  // diagnostics with source range information are emitted only in between
  // BeginSourceFile() and EndSourceFile().
  DiagClient->BeginSourceFile(Ctx.getLangOpts(), &Unit->getPreprocessor());

  Rewriter rewriter(Ctx.getSourceManager(), Ctx.getLangOpts());
  TransformActions TA(*Diags, capturedDiags, Ctx, Unit->getPreprocessor());
  MigrationPass pass(Ctx, OrigCI.getLangOpts()->getGC(),
                     Unit->getSema(), TA, ARCMTMacroLocs);

  trans(pass);

  {
    RewritesApplicator applicator(rewriter, Ctx, listener);
    TA.applyRewrites(applicator);
  }

  DiagClient->EndSourceFile();

  if (DiagClient->getNumErrors())
    return true;

  for (Rewriter::buffer_iterator
        I = rewriter.buffer_begin(), E = rewriter.buffer_end(); I != E; ++I) {
    FileID FID = I->first;
    RewriteBuffer &buf = I->second;
    const FileEntry *file = Ctx.getSourceManager().getFileEntryForID(FID);
    assert(file);
    std::string newFname = file->getName();
    newFname += "-trans";
    SmallString<512> newText;
    llvm::raw_svector_ostream vecOS(newText);
    buf.write(vecOS);
    vecOS.flush();
    llvm::MemoryBuffer *memBuf = llvm::MemoryBuffer::getMemBufferCopy(
                   StringRef(newText.data(), newText.size()), newFname);
    SmallString<64> filePath(file->getName());
    Unit->getFileManager().FixupRelativePath(filePath);
    Remapper.remap(filePath.str(), memBuf);
  }

  return false;
}

//.........这里部分代码省略.........
        break;
      }

      case PartOfSpeech::Preposition:
      case PartOfSpeech::Gerund:
      case PartOfSpeech::Unknown:
        return name;
      }
      break;

    case NameRole::BaseName:
    case NameRole::FirstParameter:
    case NameRole::Partial:
    case NameRole::SubsequentParameter:
      // Classify the part of speech of the word before the type
      // information we would strip off.
      switch (getPartOfSpeech(*nameWordRevIter)) {
      case PartOfSpeech::Preposition:
        if (role == NameRole::BaseName) {
          // Strip off the part of the name that is redundant with
          // type information, so long as there's something preceding the
          // preposition.
          if (std::next(nameWordRevIter) != nameWordRevIterEnd)
            name = name.substr(0, nameWordRevIter.base().getPosition());
          break;
        }

        SWIFT_FALLTHROUGH;

      case PartOfSpeech::Verb:
      case PartOfSpeech::Gerund:
        // Don't prune redundant type information from the base name if
        // there is a corresponding property (either singular or plural).
        if (allPropertyNames && role == NameRole::BaseName) {
          SmallString<16> localScratch;
          auto removedText = name.substr(nameWordRevIter.base().getPosition());
          auto removedName = camel_case::toLowercaseWord(removedText,
                                                         localScratch);

          // A property with exactly this name.
          if (allPropertyNames->contains(removedName)) return name;

          // From here on, we'll be working with scratch space.
          if (removedName.data() != localScratch.data())
            localScratch = removedName;

          if (localScratch.back() == 'y') {
            // If the last letter is a 'y', try 'ies'.
            localScratch.pop_back();
            localScratch += "ies";
            if (allPropertyNames->contains(localScratch)) return name;
          } else {
            // Otherwise, add an 's' and try again.
            localScratch += 's';
            if (allPropertyNames->contains(localScratch)) return name;

            // Alternatively, try to add 'es'.
            localScratch.pop_back();
            localScratch += "es";
            if (allPropertyNames->contains(localScratch)) return name;
          }
        }

        // Strip off the part of the name that is redundant with
        // type information.
        name = name.substr(0, nameWordRevIter.base().getPosition());
        break;

      case PartOfSpeech::Unknown:
        // Assume it's a noun or adjective; don't strip anything.
        break;
      }
      break;
    }

  }

  // If we ended up with a vacuous name like "get" or "set", do nothing.
  if (isVacuousName(name))
    return origName;

  switch (role) {
  case NameRole::BaseName:
  case NameRole::BaseNameSelf:
  case NameRole::Property:
    // If we ended up with a keyword for a property name or base name,
    // do nothing.
    if (isKeyword(name))
      return origName;
    break;

  case NameRole::SubsequentParameter:
  case NameRole::FirstParameter:
  case NameRole::Partial:
    break;
  }

  // We're done.
  return name;
}

C2::ExprResult C2Sema::ActOnNumericConstant(const Token& Tok) {
#ifdef SEMA_DEBUG
    std::cerr << COL_SEMA << "SEMA: numeric constant" << ANSI_NORMAL"\n";
#endif
    // Fast path for a single digit (which is quite common).  A single digit
    // cannot have a trigraph, escaped newline, radix prefix, or suffix.
    if (Tok.getLength() == 1) {
        const char Val = PP.getSpellingOfSingleCharacterNumericConstant(Tok);
        return ActOnIntegerConstant(Tok.getLocation(), Val-'0');
    }
  SmallString<128> SpellingBuffer;
  // NumericLiteralParser wants to overread by one character.  Add padding to
  // the buffer in case the token is copied to the buffer.  If getSpelling()
  // returns a StringRef to the memory buffer, it should have a null char at
  // the EOF, so it is also safe.
  SpellingBuffer.resize(Tok.getLength() + 1);

  // Get the spelling of the token, which eliminates trigraphs, etc.
  bool Invalid = false;
  StringRef TokSpelling = PP.getSpelling(Tok, SpellingBuffer, &Invalid);
  if (Invalid)
    return ExprError();

  NumericLiteralParser Literal(TokSpelling, Tok.getLocation(), PP);
  if (Literal.hadError)
    return ExprError();

    if (Literal.hasUDSuffix()) {
        assert(0 && "HUH?");
    }

    Expr* Res;

    if (Literal.isFloatingLiteral()) {
        // clang::Sema::BuildFloatingLiteral()
        // TEMP Hardcoded
        const llvm::fltSemantics& Format = llvm::APFloat::IEEEsingle;
        APFloat Val(Format);

        APFloat::opStatus result = Literal.GetFloatValue(Val);
      // Overflow is always an error, but underflow is only an error if
      // we underflowed to zero (APFloat reports denormals as underflow).
      if ((result & APFloat::opOverflow) ||
          ((result & APFloat::opUnderflow) && Val.isZero())) {
        assert(0 && "TODO");
#if 0
        unsigned diagnostic;
        SmallString<20> buffer;
        if (result & APFloat::opOverflow) {
          diagnostic = diag::warn_float_overflow;
          APFloat::getLargest(Format).toString(buffer);
        } else {
          diagnostic = diag::warn_float_underflow;
          APFloat::getSmallest(Format).toString(buffer);
        }

        Diag(Tok.getLocation(), diagnostic)
          << Ty
          << StringRef(buffer.data(), buffer.size());
#endif
      }

      //bool isExact = (result == APFloat::opOK);
      //return FloatingLiteral::Create(S.Context, Val, isExact, Ty, Loc);
        Res = new FloatingLiteral(Tok.getLocation(), Val);

    } else if (!Literal.isIntegerLiteral()) {
        return ExprError();
    } else {
        QualType ty;

        const unsigned MaxWidth = 64; // for now limit to 64 bits
        llvm::APInt ResultVal(MaxWidth, 0);
        if (Literal.GetIntegerValue(ResultVal)) {
            Diag(Tok.getLocation(), diag::err_integer_literal_too_large) << 1;
        } else {
#if 0
            // Octal, Hexadecimal, and integers with a U suffix are allowed to
            // be an unsigned.
            bool AllowUnsigned = Literal.isUnsigned || Literal.getRadix() != 10;

            // Check from smallest to largest, picking the smallest type we can.
            unsigned Width = 0;
          if (!Literal.isLong && !Literal.isLongLong) {
            // Are int/unsigned possibilities?
            unsigned IntSize = 64;

            // Does it fit in a unsigned?
            if (ResultVal.isIntN(IntSize)) {
              // Does it fit in a signed int?
#if 0
              if (!Literal.isUnsigned && ResultVal[IntSize-1] == 0)
                Ty = Context.IntTy;
              else if (AllowUnsigned)
                Ty = Context.UnsignedIntTy;
#endif
              Width = IntSize;
            }
          }

//.........这里部分代码省略.........

/// StringifyArgument - Implement C99 6.10.3.2p2, converting a sequence of
/// tokens into the literal string token that should be produced by the C #
/// preprocessor operator.  If Charify is true, then it should be turned into
/// a character literal for the Microsoft charize (#@) extension.
///
Token MacroArgs::StringifyArgument(const Token *ArgToks,
                                   Preprocessor &PP, bool Charify,
                                   SourceLocation ExpansionLocStart,
                                   SourceLocation ExpansionLocEnd) {
  Token Tok;
  Tok.startToken();
  Tok.setKind(Charify ? tok::char_constant : tok::string_literal);

  const Token *ArgTokStart = ArgToks;

  // Stringify all the tokens.
  SmallString<128> Result;
  Result += "\"";

  bool isFirst = true;
  for (; ArgToks->isNot(tok::eof); ++ArgToks) {
    const Token &Tok = *ArgToks;
    if (!isFirst && (Tok.hasLeadingSpace() || Tok.isAtStartOfLine()))
      Result += ' ';
    isFirst = false;

    // If this is a string or character constant, escape the token as specified
    // by 6.10.3.2p2.
    if (tok::isStringLiteral(Tok.getKind()) || // "foo", u8R"x(foo)x"_bar, etc.
        Tok.is(tok::char_constant) ||          // 'x'
        Tok.is(tok::wide_char_constant) ||     // L'x'.
        Tok.is(tok::utf8_char_constant) ||     // u8'x'.
        Tok.is(tok::utf16_char_constant) ||    // u'x'.
        Tok.is(tok::utf32_char_constant)) {    // U'x'.
      bool Invalid = false;
      std::string TokStr = PP.getSpelling(Tok, &Invalid);
      if (!Invalid) {
        std::string Str = Lexer::Stringify(TokStr);
        Result.append(Str.begin(), Str.end());
      }
    } else if (Tok.is(tok::code_completion)) {
      PP.CodeCompleteNaturalLanguage();
    } else {
      // Otherwise, just append the token.  Do some gymnastics to get the token
      // in place and avoid copies where possible.
      unsigned CurStrLen = Result.size();
      Result.resize(CurStrLen+Tok.getLength());
      const char *BufPtr = Result.data() + CurStrLen;
      bool Invalid = false;
      unsigned ActualTokLen = PP.getSpelling(Tok, BufPtr, &Invalid);

      if (!Invalid) {
        // If getSpelling returned a pointer to an already uniqued version of
        // the string instead of filling in BufPtr, memcpy it onto our string.
        if (ActualTokLen && BufPtr != &Result[CurStrLen])
          memcpy(&Result[CurStrLen], BufPtr, ActualTokLen);

        // If the token was dirty, the spelling may be shorter than the token.
        if (ActualTokLen != Tok.getLength())
          Result.resize(CurStrLen+ActualTokLen);
      }
    }
  }

  // If the last character of the string is a \, and if it isn't escaped, this
  // is an invalid string literal, diagnose it as specified in C99.
  if (Result.back() == '\\') {
    // Count the number of consecutive \ characters.  If even, then they are
    // just escaped backslashes, otherwise it's an error.
    unsigned FirstNonSlash = Result.size()-2;
    // Guaranteed to find the starting " if nothing else.
    while (Result[FirstNonSlash] == '\\')
      --FirstNonSlash;
    if ((Result.size()-1-FirstNonSlash) & 1) {
      // Diagnose errors for things like: #define F(X) #X   /   F(\)
      PP.Diag(ArgToks[-1], diag::pp_invalid_string_literal);
      Result.pop_back();  // remove one of the \'s.
    }
  }
  Result += '"';

  // If this is the charify operation and the result is not a legal character
  // constant, diagnose it.
  if (Charify) {
    // First step, turn double quotes into single quotes:
    Result[0] = '\'';
    Result[Result.size()-1] = '\'';

    // Check for bogus character.
    bool isBad = false;
    if (Result.size() == 3)
      isBad = Result[1] == '\'';   // ''' is not legal. '\' already fixed above.
    else
      isBad = (Result.size() != 4 || Result[1] != '\\');  // Not '\x'

    if (isBad) {
      PP.Diag(ArgTokStart[0], diag::err_invalid_character_to_charify);
      Result = "' '";  // Use something arbitrary, but legal.
    }
  }
//.........这里部分代码省略.........

/// PasteTokens - Tok is the LHS of a ## operator, and CurToken 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 Tok.
/// If this returns true, the caller should immediately return the token.
bool TokenLexer::PasteTokens(Token &Tok) {
  // 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 && (CurToken >= 2) &&
      Tokens[CurToken - 2].is(tok::hashhash))
    Tok.clearFlag(Token::LeadingSpace);
  
  SmallString<128> Buffer;
  const char *ResultTokStrPtr = nullptr;
  SourceLocation StartLoc = Tok.getLocation();
  SourceLocation PasteOpLoc;
  do {
    // Consume the ## operator if any.
    PasteOpLoc = Tokens[CurToken].getLocation();
    if (Tokens[CurToken].is(tok::hashhash))
      ++CurToken;
    assert(!isAtEnd() && "No token on the RHS of a paste operator!");

    // Get the RHS token.
    const Token &RHS = Tokens[CurToken];

    // Allocate space for the result token.  This is guaranteed to be enough for
    // the two tokens.
    Buffer.resize(Tok.getLength() + RHS.getLength());

    // Get the spelling of the LHS token in Buffer.
    const char *BufPtr = &Buffer[0];
    bool Invalid = false;
    unsigned LHSLen = PP.getSpelling(Tok, 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 (Tok.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);

//.........这里部分代码省略.........

int main(int ac, char **av)
{
    SourceMgr SrcMgr;

    //LLVMInitializeX86TargetInfo();
    llvm::InitializeAllTargetInfos();
    //LLVMInitializeX86AsmParser();
    llvm::InitializeAllTargetMCs();
    //LLVMInitializeX86TargetMC();
    llvm::InitializeAllAsmParsers();
    //LLVMInitializeX86AsmParser();
    llvm::InitializeAllDisassemblers();
    //LLVMInitializeX86Disassembler();

    // arg0:
    // llvm::Target encapsulating the "x86_64-apple-darwin14.5.0" information 

    // see /lib/Support/Triple.cpp for the details
    //spec = llvm::sys::getDefaultTargetTriple();
    //std::string machSpec = "x86_64-apple-windows"; // will produce a COFF
    //std::string machSpec = "x86_64-apple-darwin14.5.0"; // will produce a Mach-O
    std::string machSpec = "arm-none-none-eabi"; //
    //std::string machSpec = "x86_64-apple-darwin";
    //std::string machSpec = "x86_64-thumb-linux-gnu";
    //std::string machSpec = "x86_64-unknown-linux-gnu";
    printf("machine spec: %s\n", machSpec.c_str());
    machSpec = Triple::normalize(machSpec);
    printf("machine spec (normalized): %s\n", machSpec.c_str());
    Triple TheTriple(machSpec);

    // Get the target specific parser.
    std::string Error;
    const Target *TheTarget = TargetRegistry::lookupTarget(/*arch*/"", TheTriple, Error);
    if (!TheTarget) {
        errs() << Error;
        return -1;
    }

    machSpec = TheTriple.getTriple();
    printf("machine spec (returned): %s\n", machSpec.c_str());
    
    printf("Target.getName(): %s\n", TheTarget->getName());
    printf("Target.getShortDescription(): %s\n", TheTarget->getShortDescription());

    /* from the target we get almost everything */
    std::unique_ptr<MCRegisterInfo> MRI(TheTarget->createMCRegInfo(machSpec));
    std::unique_ptr<MCAsmInfo> MAI(TheTarget->createMCAsmInfo(*MRI, machSpec));
    std::unique_ptr<MCInstrInfo> MCII(TheTarget->createMCInstrInfo()); /* describes target instruction set */
    MCSubtargetInfo *STI = TheTarget->createMCSubtargetInfo(machSpec, "", ""); /* subtarget instr set */
    MCAsmBackend *MAB = TheTarget->createMCAsmBackend(*MRI, machSpec, /* specific CPU */ "");

    // arg0:
    // llvm::SourceMgr (Support/SourceMgr.h) that holds assembler source
    // has vector of llvm::SrcBuffer encaps (Support/MemoryBuffer.h) and vector of include dirs
    //std::string asmSrc = ".org 0x100, 0xAA\nfoo:\nxor %eax, %ebx\npush %rbp\njmp foo\nrdtsc\n";
	//std::string asmSrc = ".text\n" "ldr pc, data_foo\n" "\n" "data_foo:\n" "    .int 0x8\n" "\n" "loop:\n" "b loop\n";
	//std::string asmSrc = ".text\n" "mov r2, r1\n";
	std::string asmSrc = ".text\n" "ldr pc, data_foo\n" "data_foo:\n" ".int 0x8\n" "loop:\n" "b loop\n";

    std::unique_ptr<MemoryBuffer> memBuf = MemoryBuffer::getMemBuffer(asmSrc);
    SrcMgr.AddNewSourceBuffer(std::move(memBuf), SMLoc());

    // arg1: the machine code context
    MCObjectFileInfo MOFI;
    MCContext Ctx(MAI.get(), MRI.get(), &MOFI, &SrcMgr);
    MOFI.InitMCObjectFileInfo(TheTriple, Reloc::Default, CodeModel::Default, Ctx);

    // this is the assembler interface
    // -methods per .s statements (emit bytes, handle directive, etc.)
    // -remembers current section
    // -implementations that write a .s, or .o in various formats
    //
    //   1. the output stream ... a formatted_raw_ostream wraps a raw_ostream to provide
    //   tracking of line and column position for padding and shit
    //
    //   but raw_ostream is abstract and is implemented by raw_fd_ostream, raw_string_ostream, etc.

	/* output stream:
		raw_svector_ostream is a raw_pwrite_stream is a raw_ostream
		since a SmallString is SmallVector (svector) we can use this and 
		retrieve bytes later with its .data() method */
	SmallString<1024> smallString;
    raw_svector_ostream rso(smallString);

    /* code emitter needs 1) instruction set info 2) register info */
    MCCodeEmitter *CE = TheTarget->createMCCodeEmitter(*MCII, *MRI, Ctx);

    MCStreamer *as = TheTarget->createMCObjectStreamer(
		TheTriple, /* Triple */	
        Ctx, /* the MCContext */
        *MAB,  /* the AsmBackend, (fixups, relaxation, objs and elfs) */
        rso, /* output stream raw_pwrite_stream */
        CE, /* code emitter */
		*STI, /* subtarget info */
		true, /* relax all fixups */
		true, /* incremental linker compatible */ 
        false /* DWARFMustBeAtTheEnd */
    );

    std::string abi = "none";
//.........这里部分代码省略.........