text: //===- llvm/Support/CommandLine.h - Command line handler --------*- C++ -*-===//
  //
  //                     The LLVM Compiler Infrastructure
  //
  // This file is distributed under the University of Illinois Open Source
  // License. See LICENSE.TXT for details.
  //
  //===----------------------------------------------------------------------===//
  //
  // This class implements a command line argument processor that is useful when
  // creating a tool.  It provides a simple, minimalistic interface that is easily
  // extensible and supports nonlocal (library) command line options.
  //
  // Note that rather than trying to figure out what this code does, you should
  // read the library documentation located in docs/CommandLine.html or looks at
  // the many example usages in tools/*/*.cpp
  //
  //===----------------------------------------------------------------------===//
  
  #ifndef LLVM_SUPPORT_COMMANDLINE_H
  #define LLVM_SUPPORT_COMMANDLINE_H
  
  #include "llvm/ADT/ArrayRef.h"
  #include "llvm/ADT/STLExtras.h"
  #include "llvm/ADT/SmallPtrSet.h"
  #include "llvm/ADT/SmallVector.h"
  #include "llvm/ADT/StringMap.h"
  #include "llvm/ADT/StringRef.h"
  #include "llvm/ADT/Twine.h"
  #include "llvm/ADT/iterator_range.h"
  #include "llvm/Support/ErrorHandling.h"
  #include "llvm/Support/ManagedStatic.h"
  #include <cassert>
  #include <climits>
  #include <cstddef>
  #include <functional>
  #include <initializer_list>
  #include <string>
  #include <type_traits>
  #include <vector>
  
  namespace llvm {
  
  class StringSaver;
  class raw_ostream;
  
  /// cl Namespace - This namespace contains all of the command line option
  /// processing machinery.  It is intentionally a short name to make qualified
  /// usage concise.
  namespace cl {
  
  //===----------------------------------------------------------------------===//
  // ParseCommandLineOptions - Command line option processing entry point.
  //
  // Returns true on success. Otherwise, this will print the error message to
  // stderr and exit if \p Errs is not set (nullptr by default), or print the
  // error message to \p Errs and return false if \p Errs is provided.
  bool ParseCommandLineOptions(int argc, const char *const *argv,
                               StringRef Overview = "",
                               raw_ostream *Errs = nullptr);
  
  //===----------------------------------------------------------------------===//
  // ParseEnvironmentOptions - Environment variable option processing alternate
  //                           entry point.
  //
  void ParseEnvironmentOptions(const char *progName, const char *envvar,
                               const char *Overview = "");
  
  // Function pointer type for printing version information.
  using VersionPrinterTy = std::function<void(raw_ostream &)>;
  
  ///===---------------------------------------------------------------------===//
  /// SetVersionPrinter - Override the default (LLVM specific) version printer
  ///                     used to print out the version when --version is given
  ///                     on the command line. This allows other systems using the
  ///                     CommandLine utilities to print their own version string.
  void SetVersionPrinter(VersionPrinterTy func);
  
  ///===---------------------------------------------------------------------===//
  /// AddExtraVersionPrinter - Add an extra printer to use in addition to the
  ///                          default one. This can be called multiple times,
  ///                          and each time it adds a new function to the list
  ///                          which will be called after the basic LLVM version
  ///                          printing is complete. Each can then add additional
  ///                          information specific to the tool.
  void AddExtraVersionPrinter(VersionPrinterTy func);
  
  // PrintOptionValues - Print option values.
  // With -print-options print the difference between option values and defaults.
  // With -print-all-options print all option values.
  // (Currently not perfect, but best-effort.)
  void PrintOptionValues();
  
  // Forward declaration - AddLiteralOption needs to be up here to make gcc happy.
  class Option;
  
  /// \brief Adds a new option for parsing and provides the option it refers to.
  ///
  /// \param O pointer to the option
  /// \param Name the string name for the option to handle during parsing
  ///
  /// Literal options are used by some parsers to register special option values.
  /// This is how the PassNameParser registers pass names for opt.
  void AddLiteralOption(Option &O, StringRef Name);
  
  //===----------------------------------------------------------------------===//
  // Flags permitted to be passed to command line arguments
  //
  
  enum NumOccurrencesFlag { // Flags for the number of occurrences allowed
    Optional = 0x00,        // Zero or One occurrence
    ZeroOrMore = 0x01,      // Zero or more occurrences allowed
    Required = 0x02,        // One occurrence required
    OneOrMore = 0x03,       // One or more occurrences required
  
    // ConsumeAfter - Indicates that this option is fed anything that follows the
    // last positional argument required by the application (it is an error if
    // there are zero positional arguments, and a ConsumeAfter option is used).
    // Thus, for example, all arguments to LLI are processed until a filename is
    // found.  Once a filename is found, all of the succeeding arguments are
    // passed, unprocessed, to the ConsumeAfter option.
    //
    ConsumeAfter = 0x04
  };
  
  enum ValueExpected { // Is a value required for the option?
    // zero reserved for the unspecified value
    ValueOptional = 0x01,  // The value can appear... or not
    ValueRequired = 0x02,  // The value is required to appear!
    ValueDisallowed = 0x03 // A value may not be specified (for flags)
  };
  
  enum OptionHidden {   // Control whether -help shows this option
    NotHidden = 0x00,   // Option included in -help & -help-hidden
    Hidden = 0x01,      // -help doesn't, but -help-hidden does
    ReallyHidden = 0x02 // Neither -help nor -help-hidden show this arg
  };
  
  // Formatting flags - This controls special features that the option might have
  // that cause it to be parsed differently...
  //
  // Prefix - This option allows arguments that are otherwise unrecognized to be
  // matched by options that are a prefix of the actual value.  This is useful for
  // cases like a linker, where options are typically of the form '-lfoo' or
  // '-L../../include' where -l or -L are the actual flags.  When prefix is
  // enabled, and used, the value for the flag comes from the suffix of the
  // argument.
  //
  // Grouping - With this option enabled, multiple letter options are allowed to
  // bunch together with only a single hyphen for the whole group.  This allows
  // emulation of the behavior that ls uses for example: ls -la === ls -l -a
  //
  
  enum FormattingFlags {
    NormalFormatting = 0x00, // Nothing special
    Positional = 0x01,       // Is a positional argument, no '-' required
    Prefix = 0x02,           // Can this option directly prefix its value?
    Grouping = 0x03          // Can this option group with other options?
  };
  
  enum MiscFlags {             // Miscellaneous flags to adjust argument
    CommaSeparated = 0x01,     // Should this cl::list split between commas?
    PositionalEatsArgs = 0x02, // Should this positional cl::list eat -args?
    Sink = 0x04                // Should this cl::list eat all unknown options?
  };
  
  //===----------------------------------------------------------------------===//
  // Option Category class
  //
  class OptionCategory {
  private:
    StringRef const Name;
    StringRef const Description;
  
    void registerCategory();
  
  public:
    OptionCategory(StringRef const Name,
                   StringRef const Description = "")
        : Name(Name), Description(Description) {
      registerCategory();
    }
  
    StringRef getName() const { return Name; }
    StringRef getDescription() const { return Description; }
  };
  
  // The general Option Category (used as default category).
  extern OptionCategory GeneralCategory;
  
  //===----------------------------------------------------------------------===//
  // SubCommand class
  //
  class SubCommand {
  private:
    StringRef Name;
    StringRef Description;
  
  protected:
    void registerSubCommand();
    void unregisterSubCommand();
  
  public:
    SubCommand(StringRef Name, StringRef Description = "")
        : Name(Name), Description(Description) {
          registerSubCommand();
    }
    SubCommand() = default;
  
    void reset();
  
    explicit operator bool() const;
  
    StringRef getName() const { return Name; }
    StringRef getDescription() const { return Description; }
  
    SmallVector<Option *, 4> PositionalOpts;
    SmallVector<Option *, 4> SinkOpts;
    StringMap<Option *> OptionsMap;
  
    Option *ConsumeAfterOpt = nullptr; // The ConsumeAfter option if it exists.
  };
  
  // A special subcommand representing no subcommand
  extern ManagedStatic<SubCommand> TopLevelSubCommand;
  
  // A special subcommand that can be used to put an option into all subcommands.
  extern ManagedStatic<SubCommand> AllSubCommands;
  
  //===----------------------------------------------------------------------===//
  // Option Base class
  //
  class Option {
    friend class alias;
  
    // handleOccurrences - Overriden by subclasses to handle the value passed into
    // an argument.  Should return true if there was an error processing the
    // argument and the program should exit.
    //
    virtual bool handleOccurrence(unsigned pos, StringRef ArgName,
                                  StringRef Arg) = 0;
  
    virtual enum ValueExpected getValueExpectedFlagDefault() const {
      return ValueOptional;
    }
  
    // Out of line virtual function to provide home for the class.
    virtual void anchor();
  
    int NumOccurrences = 0; // The number of times specified
    // Occurrences, HiddenFlag, and Formatting are all enum types but to avoid
    // problems with signed enums in bitfields.
    unsigned Occurrences : 3; // enum NumOccurrencesFlag
    // not using the enum type for 'Value' because zero is an implementation
    // detail representing the non-value
    unsigned Value : 2;
    unsigned HiddenFlag : 2; // enum OptionHidden
    unsigned Formatting : 2; // enum FormattingFlags
    unsigned Misc : 3;
    unsigned Position = 0;       // Position of last occurrence of the option
    unsigned AdditionalVals = 0; // Greater than 0 for multi-valued option.
  
  public:
    StringRef ArgStr;   // The argument string itself (ex: "help", "o")
    StringRef HelpStr;  // The descriptive text message for -help
    StringRef ValueStr; // String describing what the value of this option is
    OptionCategory *Category; // The Category this option belongs to
    SmallPtrSet<SubCommand *, 4> Subs; // The subcommands this option belongs to.
    bool FullyInitialized = false; // Has addArgument been called?
  
    inline enum NumOccurrencesFlag getNumOccurrencesFlag() const {
      return (enum NumOccurrencesFlag)Occurrences;
    }
  
    inline enum ValueExpected getValueExpectedFlag() const {
      return Value ? ((enum ValueExpected)Value) : getValueExpectedFlagDefault();
    }
  
    inline enum OptionHidden getOptionHiddenFlag() const {
      return (enum OptionHidden)HiddenFlag;
    }
  
    inline enum FormattingFlags getFormattingFlag() const {
      return (enum FormattingFlags)Formatting;
    }
  
    inline unsigned getMiscFlags() const { return Misc; }
    inline unsigned getPosition() const { return Position; }
    inline unsigned getNumAdditionalVals() const { return AdditionalVals; }
  
    // hasArgStr - Return true if the argstr != ""
    bool hasArgStr() const { return !ArgStr.empty(); }
    bool isPositional() const { return getFormattingFlag() == cl::Positional; }
    bool isSink() const { return getMiscFlags() & cl::Sink; }
  
    bool isConsumeAfter() const {
      return getNumOccurrencesFlag() == cl::ConsumeAfter;
    }
  
    bool isInAllSubCommands() const {
      return any_of(Subs, [](const SubCommand *SC) {
        return SC == &*AllSubCommands;
      });
    }
  
    //-------------------------------------------------------------------------===
    // Accessor functions set by OptionModifiers
    //
    void setArgStr(StringRef S);
    void setDescription(StringRef S) { HelpStr = S; }
    void setValueStr(StringRef S) { ValueStr = S; }
    void setNumOccurrencesFlag(enum NumOccurrencesFlag Val) { Occurrences = Val; }
    void setValueExpectedFlag(enum ValueExpected Val) { Value = Val; }
    void setHiddenFlag(enum OptionHidden Val) { HiddenFlag = Val; }
    void setFormattingFlag(enum FormattingFlags V) { Formatting = V; }
    void setMiscFlag(enum MiscFlags M) { Misc |= M; }
    void setPosition(unsigned pos) { Position = pos; }
    void setCategory(OptionCategory &C) { Category = &C; }
    void addSubCommand(SubCommand &S) { Subs.insert(&S); }
  
  protected:
    explicit Option(enum NumOccurrencesFlag OccurrencesFlag,
                    enum OptionHidden Hidden)
        : Occurrences(OccurrencesFlag), Value(0), HiddenFlag(Hidden),
          Formatting(NormalFormatting), Misc(0), Category(&GeneralCategory) {}
  
    inline void setNumAdditionalVals(unsigned n) { AdditionalVals = n; }
  
  public:
    virtual ~Option() = default;
  
    // addArgument - Register this argument with the commandline system.
    //
    void addArgument();
  
    /// Unregisters this option from the CommandLine system.
    ///
    /// This option must have been the last option registered.
    /// For testing purposes only.
    void removeArgument();
  
    // Return the width of the option tag for printing...
    virtual size_t getOptionWidth() const = 0;
  
    // printOptionInfo - Print out information about this option.  The
    // to-be-maintained width is specified.
    //
    virtual void printOptionInfo(size_t GlobalWidth) const = 0;
  
    virtual void printOptionValue(size_t GlobalWidth, bool Force) const = 0;
  
    virtual void setDefault() = 0;
  
    static void printHelpStr(StringRef HelpStr, size_t Indent,
                             size_t FirstLineIndentedBy);
  
    virtual void getExtraOptionNames(SmallVectorImpl<StringRef> &) {}
  
    // addOccurrence - Wrapper around handleOccurrence that enforces Flags.
    //
    virtual bool addOccurrence(unsigned pos, StringRef ArgName, StringRef Value,
                               bool MultiArg = false);
  
    // Prints option name followed by message.  Always returns true.
    bool error(const Twine &Message, StringRef ArgName = StringRef());
  
    inline int getNumOccurrences() const { return NumOccurrences; }
    inline void reset() { NumOccurrences = 0; }
  };
  
  //===----------------------------------------------------------------------===//
  // Command line option modifiers that can be used to modify the behavior of
  // command line option parsers...
  //
  
  // desc - Modifier to set the description shown in the -help output...
  struct desc {
    StringRef Desc;
  
    desc(StringRef Str) : Desc(Str) {}
  
    void apply(Option &O) const { O.setDescription(Desc); }
  };
  
  // value_desc - Modifier to set the value description shown in the -help
  // output...
  struct value_desc {
    StringRef Desc;
  
    value_desc(StringRef Str) : Desc(Str) {}
  
    void apply(Option &O) const { O.setValueStr(Desc); }
  };
  
  // init - Specify a default (initial) value for the command line argument, if
  // the default constructor for the argument type does not give you what you
  // want.  This is only valid on "opt" arguments, not on "list" arguments.
  //
  template <class Ty> struct initializer {
    const Ty &Init;
    initializer(const Ty &Val) : Init(Val) {}
  
    template <class Opt> void apply(Opt &O) const { O.setInitialValue(Init); }
  };
  
  template <class Ty> initializer<Ty> init(const Ty &Val) {
    return initializer<Ty>(Val);
  }
  
  // location - Allow the user to specify which external variable they want to
  // store the results of the command line argument processing into, if they don't
  // want to store it in the option itself.
  //
  template <class Ty> struct LocationClass {
    Ty &Loc;
  
    LocationClass(Ty &L) : Loc(L) {}
  
    template <class Opt> void apply(Opt &O) const { O.setLocation(O, Loc); }
  };
  
  template <class Ty> LocationClass<Ty> location(Ty &L) {
    return LocationClass<Ty>(L);
  }
  
  // cat - Specifiy the Option category for the command line argument to belong
  // to.
  struct cat {
    OptionCategory &Category;
  
    cat(OptionCategory &c) : Category(c) {}
  
    template <class Opt> void apply(Opt &O) const { O.setCategory(Category); }
  };
  
  // sub - Specify the subcommand that this option belongs to.
  struct sub {
    SubCommand &Sub;
  
    sub(SubCommand &S) : Sub(S) {}
  
    template <class Opt> void apply(Opt &O) const { O.addSubCommand(Sub); }
  };
  
  //===----------------------------------------------------------------------===//
  // OptionValue class
  
  // Support value comparison outside the template.
  struct GenericOptionValue {
    virtual bool compare(const GenericOptionValue &V) const = 0;
  
  protected:
    GenericOptionValue() = default;
    GenericOptionValue(const GenericOptionValue&) = default;
    GenericOptionValue &operator=(const GenericOptionValue &) = default;
    ~GenericOptionValue() = default;
  
  private:
    virtual void anchor();
  };
  
  template <class DataType> struct OptionValue;
  
  // The default value safely does nothing. Option value printing is only
  // best-effort.
  template <class DataType, bool isClass>
  struct OptionValueBase : public GenericOptionValue {
    // Temporary storage for argument passing.
    using WrapperType = OptionValue<DataType>;
  
    bool hasValue() const { return false; }
  
    const DataType &getValue() const { llvm_unreachable("no default value"); }
  
    // Some options may take their value from a different data type.
    template <class DT> void setValue(const DT & /*V*/) {}
  
    bool compare(const DataType & /*V*/) const { return false; }
  
    bool compare(const GenericOptionValue & /*V*/) const override {
      return false;
    }
  
  protected:
    ~OptionValueBase() = default;
  };
  
  // Simple copy of the option value.
  template <class DataType> class OptionValueCopy : public GenericOptionValue {
    DataType Value;
    bool Valid = false;
  
  protected:
    OptionValueCopy(const OptionValueCopy&) = default;
    OptionValueCopy &operator=(const OptionValueCopy &) = default;
    ~OptionValueCopy() = default;
  
  public:
    OptionValueCopy() = default;
  
    bool hasValue() const { return Valid; }
  
    const DataType &getValue() const {
      assert(Valid && "invalid option value");
      return Value;
    }
  
    void setValue(const DataType &V) {
      Valid = true;
      Value = V;
    }
  
    bool compare(const DataType &V) const { return Valid && (Value != V); }
  
    bool compare(const GenericOptionValue &V) const override {
      const OptionValueCopy<DataType> &VC =
          static_cast<const OptionValueCopy<DataType> &>(V);
      if (!VC.hasValue())
        return false;
      return compare(VC.getValue());
    }
  };
  
  // Non-class option values.
  template <class DataType>
  struct OptionValueBase<DataType, false> : OptionValueCopy<DataType> {
    using WrapperType = DataType;
  
  protected:
    OptionValueBase() = default;
    OptionValueBase(const OptionValueBase&) = default;
    OptionValueBase &operator=(const OptionValueBase &) = default;
    ~OptionValueBase() = default;
  };
  
  // Top-level option class.
  template <class DataType>
  struct OptionValue final
      : OptionValueBase<DataType, std::is_class<DataType>::value> {
    OptionValue() = default;
  
    OptionValue(const DataType &V) { this->setValue(V); }
  
    // Some options may take their value from a different data type.
    template <class DT> OptionValue<DataType> &operator=(const DT &V) {
      this->setValue(V);
      return *this;
    }
  };
  
  // Other safe-to-copy-by-value common option types.
  enum boolOrDefault { BOU_UNSET, BOU_TRUE, BOU_FALSE };
  template <>
  struct OptionValue<cl::boolOrDefault> final
      : OptionValueCopy<cl::boolOrDefault> {
    using WrapperType = cl::boolOrDefault;
  
    OptionValue() = default;
  
    OptionValue(const cl::boolOrDefault &V) { this->setValue(V); }
  
    OptionValue<cl::boolOrDefault> &operator=(const cl::boolOrDefault &V) {
      setValue(V);
      return *this;
    }
  
  private:
    void anchor() override;
  };
  
  template <>
  struct OptionValue<std::string> final : OptionValueCopy<std::string> {
    using WrapperType = StringRef;
  
    OptionValue() = default;
  
    OptionValue(const std::string &V) { this->setValue(V); }
  
    OptionValue<std::string> &operator=(const std::string &V) {
      setValue(V);
      return *this;
    }
  
  private:
    void anchor() override;
  };
  
  //===----------------------------------------------------------------------===//
  // Enum valued command line option
  //
  
  // This represents a single enum value, using "int" as the underlying type.
  struct OptionEnumValue {
    StringRef Name;
    int Value;
    StringRef Description;
  };
  
  #define clEnumVal(ENUMVAL, DESC)                                               \
    llvm::cl::OptionEnumValue { #ENUMVAL, int(ENUMVAL), DESC }
  #define clEnumValN(ENUMVAL, FLAGNAME, DESC)                                    \
    llvm::cl::OptionEnumValue { FLAGNAME, int(ENUMVAL), DESC }
  
  // values - For custom data types, allow specifying a group of values together
  // as the values that go into the mapping that the option handler uses.
  //
  class ValuesClass {
    // Use a vector instead of a map, because the lists should be short,
    // the overhead is less, and most importantly, it keeps them in the order
    // inserted so we can print our option out nicely.
    SmallVector<OptionEnumValue, 4> Values;
  
  public:
    ValuesClass(std::initializer_list<OptionEnumValue> Options)
        : Values(Options) {}
  
    template <class Opt> void apply(Opt &O) const {
      for (auto Value : Values)
        O.getParser().addLiteralOption(Value.Name, Value.Value,
                                       Value.Description);
    }
  };
  
  /// Helper to build a ValuesClass by forwarding a variable number of arguments
  /// as an initializer list to the ValuesClass constructor.
  template <typename... OptsTy> ValuesClass values(OptsTy... Options) {
    return ValuesClass({Options...});
  }
  
  //===----------------------------------------------------------------------===//
  // parser class - Parameterizable parser for different data types.  By default,
  // known data types (string, int, bool) have specialized parsers, that do what
  // you would expect.  The default parser, used for data types that are not
  // built-in, uses a mapping table to map specific options to values, which is
  // used, among other things, to handle enum types.
  
  //--------------------------------------------------
  // generic_parser_base - This class holds all the non-generic code that we do
  // not need replicated for every instance of the generic parser.  This also
  // allows us to put stuff into CommandLine.cpp
  //
  class generic_parser_base {
  protected:
    class GenericOptionInfo {
    public:
      GenericOptionInfo(StringRef name, StringRef helpStr)
          : Name(name), HelpStr(helpStr) {}
      StringRef Name;
      StringRef HelpStr;
    };
  
  public:
    generic_parser_base(Option &O) : Owner(O) {}
  
    virtual ~generic_parser_base() = default;
    // Base class should have virtual-destructor
  
    // getNumOptions - Virtual function implemented by generic subclass to
    // indicate how many entries are in Values.
    //
    virtual unsigned getNumOptions() const = 0;
  
    // getOption - Return option name N.
    virtual StringRef getOption(unsigned N) const = 0;
  
    // getDescription - Return description N
    virtual StringRef getDescription(unsigned N) const = 0;
  
    // Return the width of the option tag for printing...
    virtual size_t getOptionWidth(const Option &O) const;
  
    virtual const GenericOptionValue &getOptionValue(unsigned N) const = 0;
  
    // printOptionInfo - Print out information about this option.  The
    // to-be-maintained width is specified.
    //
    virtual void printOptionInfo(const Option &O, size_t GlobalWidth) const;
  
    void printGenericOptionDiff(const Option &O, const GenericOptionValue &V,
                                const GenericOptionValue &Default,
                                size_t GlobalWidth) const;
  
    // printOptionDiff - print the value of an option and it's default.
    //
    // Template definition ensures that the option and default have the same
    // DataType (via the same AnyOptionValue).
    template <class AnyOptionValue>
    void printOptionDiff(const Option &O, const AnyOptionValue &V,
                         const AnyOptionValue &Default,
                         size_t GlobalWidth) const {
      printGenericOptionDiff(O, V, Default, GlobalWidth);
    }
  
    void initialize() {}
  
    void getExtraOptionNames(SmallVectorImpl<StringRef> &OptionNames) {
      // If there has been no argstr specified, that means that we need to add an
      // argument for every possible option.  This ensures that our options are
      // vectored to us.
      if (!Owner.hasArgStr())
        for (unsigned i = 0, e = getNumOptions(); i != e; ++i)
          OptionNames.push_back(getOption(i));
    }
  
    enum ValueExpected getValueExpectedFlagDefault() const {
      // If there is an ArgStr specified, then we are of the form:
      //
      //    -opt=O2   or   -opt O2  or  -optO2
      //
      // In which case, the value is required.  Otherwise if an arg str has not
      // been specified, we are of the form:
      //
      //    -O2 or O2 or -la (where -l and -a are separate options)
      //
      // If this is the case, we cannot allow a value.
      //
      if (Owner.hasArgStr())
        return ValueRequired;
      else
        return ValueDisallowed;
    }
  
    // findOption - Return the option number corresponding to the specified
    // argument string.  If the option is not found, getNumOptions() is returned.
    //
    unsigned findOption(StringRef Name);
  
  protected:
    Option &Owner;
  };
  
  // Default parser implementation - This implementation depends on having a
  // mapping of recognized options to values of some sort.  In addition to this,
  // each entry in the mapping also tracks a help message that is printed with the
  // command line option for -help.  Because this is a simple mapping parser, the
  // data type can be any unsupported type.
  //
  template <class DataType> class parser : public generic_parser_base {
  protected:
    class OptionInfo : public GenericOptionInfo {
    public:
      OptionInfo(StringRef name, DataType v, StringRef helpStr)
          : GenericOptionInfo(name, helpStr), V(v) {}
  
      OptionValue<DataType> V;
    };
    SmallVector<OptionInfo, 8> Values;
  
  public:
    parser(Option &O) : generic_parser_base(O) {}
  
    using parser_data_type = DataType;
  
    // Implement virtual functions needed by generic_parser_base
    unsigned getNumOptions() const override { return unsigned(Values.size()); }
    StringRef getOption(unsigned N) const override { return Values[N].Name; }
    StringRef getDescription(unsigned N) const override {
      return Values[N].HelpStr;
    }
  
    // getOptionValue - Return the value of option name N.
    const GenericOptionValue &getOptionValue(unsigned N) const override {
      return Values[N].V;
    }
  
    // parse - Return true on error.
    bool parse(Option &O, StringRef ArgName, StringRef Arg, DataType &V) {
      StringRef ArgVal;
      if (Owner.hasArgStr())
        ArgVal = Arg;
      else
        ArgVal = ArgName;
  
      for (size_t i = 0, e = Values.size(); i != e; ++i)
        if (Values[i].Name == ArgVal) {
          V = Values[i].V.getValue();
          return false;
        }
  
      return O.error("Cannot find option named '" + ArgVal + "'!");
    }
  
    /// addLiteralOption - Add an entry to the mapping table.
    ///
    template <class DT>
    void addLiteralOption(StringRef Name, const DT &V, StringRef HelpStr) {
      assert(findOption(Name) == Values.size() && "Option already exists!");
      OptionInfo X(Name, static_cast<DataType>(V), HelpStr);
      Values.push_back(X);
      AddLiteralOption(Owner, Name);
    }
  
    /// removeLiteralOption - Remove the specified option.
    ///
    void removeLiteralOption(StringRef Name) {
      unsigned N = findOption(Name);
      assert(N != Values.size() && "Option not found!");
      Values.erase(Values.begin() + N);
    }
  };
  
  //--------------------------------------------------
  // basic_parser - Super class of parsers to provide boilerplate code
  //
  class basic_parser_impl { // non-template implementation of basic_parser<t>
  public:
    basic_parser_impl(Option &) {}
  
    enum ValueExpected getValueExpectedFlagDefault() const {
      return ValueRequired;
    }
  
    void getExtraOptionNames(SmallVectorImpl<StringRef> &) {}
  
    void initialize() {}
  
    // Return the width of the option tag for printing...
    size_t getOptionWidth(const Option &O) const;
  
    // printOptionInfo - Print out information about this option.  The
    // to-be-maintained width is specified.
    //
    void printOptionInfo(const Option &O, size_t GlobalWidth) const;
  
    // printOptionNoValue - Print a placeholder for options that don't yet support
    // printOptionDiff().
    void printOptionNoValue(const Option &O, size_t GlobalWidth) const;
  
    // getValueName - Overload in subclass to provide a better default value.
    virtual StringRef getValueName() const { return "value"; }
  
    // An out-of-line virtual method to provide a 'home' for this class.
    virtual void anchor();
  
  protected:
    ~basic_parser_impl() = default;
  
    // A helper for basic_parser::printOptionDiff.
    void printOptionName(const Option &O, size_t GlobalWidth) const;
  };
  
  // basic_parser - The real basic parser is just a template wrapper that provides
  // a typedef for the provided data type.
  //
  template <class DataType> class basic_parser : public basic_parser_impl {
  public:
    using parser_data_type = DataType;
    using OptVal = OptionValue<DataType>;
  
    basic_parser(Option &O) : basic_parser_impl(O) {}
  
  protected:
    ~basic_parser() = default;
  };
  
  //--------------------------------------------------
  // parser<bool>
  //
  template <> class parser<bool> final : public basic_parser<bool> {
  public:
    parser(Option &O) : basic_parser(O) {}
  
    // parse - Return true on error.
    bool parse(Option &O, StringRef ArgName, StringRef Arg, bool &Val);
  
    void initialize() {}
  
    enum ValueExpected getValueExpectedFlagDefault() const {
      return ValueOptional;
    }
  
    // getValueName - Do not print =<value> at all.
    StringRef getValueName() const override { return StringRef(); }
  
    void printOptionDiff(const Option &O, bool V, OptVal Default,
                         size_t GlobalWidth) const;
  
    // An out-of-line virtual method to provide a 'home' for this class.
    void anchor() override;
  };
  
  extern template class basic_parser<bool>;
  
  //--------------------------------------------------
  // parser<boolOrDefault>
  template <>
  class parser<boolOrDefault> final : public basic_parser<boolOrDefault> {
  public:
    parser(Option &O) : basic_parser(O) {}
  
    // parse - Return true on error.
    bool parse(Option &O, StringRef ArgName, StringRef Arg, boolOrDefault &Val);
  
    enum ValueExpected getValueExpectedFlagDefault() const {
      return ValueOptional;
    }
  
    // getValueName - Do not print =<value> at all.
    StringRef getValueName() const override { return StringRef(); }
  
    void printOptionDiff(const Option &O, boolOrDefault V, OptVal Default,
                         size_t GlobalWidth) const;
  
    // An out-of-line virtual method to provide a 'home' for this class.
    void anchor() override;
  };
  
  extern template class basic_parser<boolOrDefault>;
  
  //--------------------------------------------------
  // parser<int>
  //
  template <> class parser<int> final : public basic_parser<int> {
  public:
    parser(Option &O) : basic_parser(O) {}
  
    // parse - Return true on error.
    bool parse(Option &O, StringRef ArgName, StringRef Arg, int &Val);
  
    // getValueName - Overload in subclass to provide a better default value.
    StringRef getValueName() const override { return "int"; }
  
    void printOptionDiff(const Option &O, int V, OptVal Default,
                         size_t GlobalWidth) const;
  
    // An out-of-line virtual method to provide a 'home' for this class.
    void anchor() override;
  };
  
  extern template class basic_parser<int>;
  
  //--------------------------------------------------
  // parser<unsigned>
  //
  template <> class parser<unsigned> final : public basic_parser<unsigned> {
  public:
    parser(Option &O) : basic_parser(O) {}
  
    // parse - Return true on error.
    bool parse(Option &O, StringRef ArgName, StringRef Arg, unsigned &Val);
  
    // getValueName - Overload in subclass to provide a better default value.
    StringRef getValueName() const override { return "uint"; }
  
    void printOptionDiff(const Option &O, unsigned V, OptVal Default,
                         size_t GlobalWidth) const;
  
    // An out-of-line virtual method to provide a 'home' for this class.
    void anchor() override;
  };
  
  extern template class basic_parser<unsigned>;
  
  //--------------------------------------------------
  // parser<unsigned long long>
  //
  template <>
  class parser<unsigned long long> final
      : public basic_parser<unsigned long long> {
  public:
    parser(Option &O) : basic_parser(O) {}
  
    // parse - Return true on error.
    bool parse(Option &O, StringRef ArgName, StringRef Arg,
               unsigned long long &Val);
  
    // getValueName - Overload in subclass to provide a better default value.
    StringRef getValueName() const override { return "uint"; }
  
    void printOptionDiff(const Option &O, unsigned long long V, OptVal Default,
                         size_t GlobalWidth) const;
  
    // An out-of-line virtual method to provide a 'home' for this class.
    void anchor() override;
  };
  
  extern template class basic_parser<unsigned long long>;
  
  //--------------------------------------------------
  // parser<double>
  //
  template <> class parser<double> final : public basic_parser<double> {
  public:
    parser(Option &O) : basic_parser(O) {}
  
    // parse - Return true on error.
    bool parse(Option &O, StringRef ArgName, StringRef Arg, double &Val);
  
    // getValueName - Overload in subclass to provide a better default value.
    StringRef getValueName() const override { return "number"; }
  
    void printOptionDiff(const Option &O, double V, OptVal Default,
                         size_t GlobalWidth) const;
  
    // An out-of-line virtual method to provide a 'home' for this class.
    void anchor() override;
  };
  
  extern template class basic_parser<double>;
  
  //--------------------------------------------------
  // parser<float>
  //
  template <> class parser<float> final : public basic_parser<float> {
  public:
    parser(Option &O) : basic_parser(O) {}
  
    // parse - Return true on error.
    bool parse(Option &O, StringRef ArgName, StringRef Arg, float &Val);
  
    // getValueName - Overload in subclass to provide a better default value.
    StringRef getValueName() const override { return "number"; }
  
    void printOptionDiff(const Option &O, float V, OptVal Default,
                         size_t GlobalWidth) const;
  
    // An out-of-line virtual method to provide a 'home' for this class.
    void anchor() override;
  };
  
  extern template class basic_parser<float>;
  
  //--------------------------------------------------
  // parser<std::string>
  //
  template <> class parser<std::string> final : public basic_parser<std::string> {
  public:
    parser(Option &O) : basic_parser(O) {}
  
    // parse - Return true on error.
    bool parse(Option &, StringRef, StringRef Arg, std::string &Value) {
      Value = Arg.str();
      return false;
    }
  
    // getValueName - Overload in subclass to provide a better default value.
    StringRef getValueName() const override { return "string"; }
  
    void printOptionDiff(const Option &O, StringRef V, const OptVal &Default,
                         size_t GlobalWidth) const;
  
    // An out-of-line virtual method to provide a 'home' for this class.
    void anchor() override;
  };
  
  extern template class basic_parser<std::string>;
  
  //--------------------------------------------------
  // parser<char>
  //
  template <> class parser<char> final : public basic_parser<char> {
  public:
    parser(Option &O) : basic_parser(O) {}
  
    // parse - Return true on error.
    bool parse(Option &, StringRef, StringRef Arg, char &Value) {
      Value = Arg[0];
      return false;
    }
  
    // getValueName - Overload in subclass to provide a better default value.
    StringRef getValueName() const override { return "char"; }
  
    void printOptionDiff(const Option &O, char V, OptVal Default,
                         size_t GlobalWidth) const;
  
    // An out-of-line virtual method to provide a 'home' for this class.
    void anchor() override;
  };
  
  extern template class basic_parser<char>;
  
  //--------------------------------------------------
  // PrintOptionDiff
  //
  // This collection of wrappers is the intermediary between class opt and class
  // parser to handle all the template nastiness.
  
  // This overloaded function is selected by the generic parser.
  template <class ParserClass, class DT>
  void printOptionDiff(const Option &O, const generic_parser_base &P, const DT &V,
                       const OptionValue<DT> &Default, size_t GlobalWidth) {
    OptionValue<DT> OV = V;
    P.printOptionDiff(O, OV, Default, GlobalWidth);
  }
  
  // This is instantiated for basic parsers when the parsed value has a different
  // type than the option value. e.g. HelpPrinter.
  template <class ParserDT, class ValDT> struct OptionDiffPrinter {
    void print(const Option &O, const parser<ParserDT> &P, const ValDT & /*V*/,
               const OptionValue<ValDT> & /*Default*/, size_t GlobalWidth) {
      P.printOptionNoValue(O, GlobalWidth);
    }
  };
  
  // This is instantiated for basic parsers when the parsed value has the same
  // type as the option value.
  template <class DT> struct OptionDiffPrinter<DT, DT> {
    void print(const Option &O, const parser<DT> &P, const DT &V,
               const OptionValue<DT> &Default, size_t GlobalWidth) {
      P.printOptionDiff(O, V, Default, GlobalWidth);
    }
  };
  
  // This overloaded function is selected by the basic parser, which may parse a
  // different type than the option type.
  template <class ParserClass, class ValDT>
  void printOptionDiff(
      const Option &O,
      const basic_parser<typename ParserClass::parser_data_type> &P,
      const ValDT &V, const OptionValue<ValDT> &Default, size_t GlobalWidth) {
  
    OptionDiffPrinter<typename ParserClass::parser_data_type, ValDT> printer;
    printer.print(O, static_cast<const ParserClass &>(P), V, Default,
                  GlobalWidth);
  }
  
  //===----------------------------------------------------------------------===//
  // applicator class - This class is used because we must use partial
  // specialization to handle literal string arguments specially (const char* does
  // not correctly respond to the apply method).  Because the syntax to use this
  // is a pain, we have the 'apply' method below to handle the nastiness...
  //
  template <class Mod> struct applicator {
    template <class Opt> static void opt(const Mod &M, Opt &O) { M.apply(O); }
  };
  
  // Handle const char* as a special case...
  template <unsigned n> struct applicator<char[n]> {
    template <class Opt> static void opt(StringRef Str, Opt &O) {
      O.setArgStr(Str);
    }
  };
  template <unsigned n> struct applicator<const char[n]> {
    template <class Opt> static void opt(StringRef Str, Opt &O) {
      O.setArgStr(Str);
    }
  };
  template <> struct applicator<StringRef > {
    template <class Opt> static void opt(StringRef Str, Opt &O) {
      O.setArgStr(Str);
    }
  };
  
  template <> struct applicator<NumOccurrencesFlag> {
    static void opt(NumOccurrencesFlag N, Option &O) {
      O.setNumOccurrencesFlag(N);
    }
  };
  
  template <> struct applicator<ValueExpected> {
    static void opt(ValueExpected VE, Option &O) { O.setValueExpectedFlag(VE); }
  };
  
  template <> struct applicator<OptionHidden> {
    static void opt(OptionHidden OH, Option &O) { O.setHiddenFlag(OH); }
  };
  
  template <> struct applicator<FormattingFlags> {
    static void opt(FormattingFlags FF, Option &O) { O.setFormattingFlag(FF); }
  };
  
  template <> struct applicator<MiscFlags> {
    static void opt(MiscFlags MF, Option &O) { O.setMiscFlag(MF); }
  };
  
  // apply method - Apply modifiers to an option in a type safe way.
  template <class Opt, class Mod, class... Mods>
  void apply(Opt *O, const Mod &M, const Mods &... Ms) {
    applicator<Mod>::opt(M, *O);
    apply(O, Ms...);
  }
  
  template <class Opt, class Mod> void apply(Opt *O, const Mod &M) {
    applicator<Mod>::opt(M, *O);
  }
  
  //===----------------------------------------------------------------------===//
  // opt_storage class
  
  // Default storage class definition: external storage.  This implementation
  // assumes the user will specify a variable to store the data into with the
  // cl::location(x) modifier.
  //
  template <class DataType, bool ExternalStorage, bool isClass>
  class opt_storage {
    DataType *Location = nullptr; // Where to store the object...
    OptionValue<DataType> Default;
  
    void check_location() const {
      assert(Location && "cl::location(...) not specified for a command "
                         "line option with external storage, "
                         "or cl::init specified before cl::location()!!");
    }
  
  public:
    opt_storage() = default;
  
    bool setLocation(Option &O, DataType &L) {
      if (Location)
        return O.error("cl::location(x) specified more than once!");
      Location = &L;
      Default = L;
      return false;
    }
  
    template <class T> void setValue(const T &V, bool initial = false) {
      check_location();
      *Location = V;
      if (initial)
        Default = V;
    }
  
    DataType &getValue() {
      check_location();
      return *Location;
    }
    const DataType &getValue() const {
      check_location();
      return *Location;
    }
  
    operator DataType() const { return this->getValue(); }
  
    const OptionValue<DataType> &getDefault() const { return Default; }
  };
  
  // Define how to hold a class type object, such as a string.  Since we can
  // inherit from a class, we do so.  This makes us exactly compatible with the
  // object in all cases that it is used.
  //
  template <class DataType>
  class opt_storage<DataType, false, true> : public DataType {
  public:
    OptionValue<DataType> Default;
  
    template <class T> void setValue(const T &V, bool initial = false) {
      DataType::operator=(V);
      if (initial)
        Default = V;
    }
  
    DataType &getValue() { return *this; }
    const DataType &getValue() const { return *this; }
  
    const OptionValue<DataType> &getDefault() const { return Default; }
  };
  
  // Define a partial specialization to handle things we cannot inherit from.  In
  // this case, we store an instance through containment, and overload operators
  // to get at the value.
  //
  template <class DataType> class opt_storage<DataType, false, false> {
  public:
    DataType Value;
    OptionValue<DataType> Default;
  
    // Make sure we initialize the value with the default constructor for the
    // type.
    opt_storage() : Value(DataType()), Default(DataType()) {}
  
    template <class T> void setValue(const T &V, bool initial = false) {
      Value = V;
      if (initial)
        Default = V;
    }
    DataType &getValue() { return Value; }
    DataType getValue() const { return Value; }
  
    const OptionValue<DataType> &getDefault() const { return Default; }
  
    operator DataType() const { return getValue(); }
  
    // If the datatype is a pointer, support -> on it.
    DataType operator->() const { return Value; }
  };
  
  //===----------------------------------------------------------------------===//
  // opt - A scalar command line option.
  //
  template <class DataType, bool ExternalStorage = false,
            class ParserClass = parser<DataType>>
  class opt : public Option,
              public opt_storage<DataType, ExternalStorage,
                                 std::is_class<DataType>::value> {
    ParserClass Parser;
  
    bool handleOccurrence(unsigned pos, StringRef ArgName,
                          StringRef Arg) override {
      typename ParserClass::parser_data_type Val =
          typename ParserClass::parser_data_type();
      if (Parser.parse(*this, ArgName, Arg, Val))
        return true; // Parse error!
      this->setValue(Val);
      this->setPosition(pos);
      return false;
    }
  
    enum ValueExpected getValueExpectedFlagDefault() const override {
      return Parser.getValueExpectedFlagDefault();
    }
  
    void getExtraOptionNames(SmallVectorImpl<StringRef> &OptionNames) override {
      return Parser.getExtraOptionNames(OptionNames);
    }
  
    // Forward printing stuff to the parser...
    size_t getOptionWidth() const override {
      return Parser.getOptionWidth(*this);
    }
  
    void printOptionInfo(size_t GlobalWidth) const override {
      Parser.printOptionInfo(*this, GlobalWidth);
    }
  
    void printOptionValue(size_t GlobalWidth, bool Force) const override {
      if (Force || this->getDefault().compare(this->getValue())) {
        cl::printOptionDiff<ParserClass>(*this, Parser, this->getValue(),
                                         this->getDefault(), GlobalWidth);
      }
    }
  
    template <class T, class = typename std::enable_if<
              std::is_assignable<T&, T>::value>::type>
    void setDefaultImpl() {
      const OptionValue<DataType> &V = this->getDefault();
      if (V.hasValue())
        this->setValue(V.getValue());
    }
  
    template <class T, class = typename std::enable_if<
              !std::is_assignable<T&, T>::value>::type>
    void setDefaultImpl(...) {}
  
    void setDefault() override { setDefaultImpl<DataType>(); }
  
    void done() {
      addArgument();
      Parser.initialize();
    }
  
  public:
    // Command line options should not be copyable
    opt(const opt &) = delete;
    opt &operator=(const opt &) = delete;
  
    // setInitialValue - Used by the cl::init modifier...
    void setInitialValue(const DataType &V) { this->setValue(V, true); }
  
    ParserClass &getParser() { return Parser; }
  
    template <class T> DataType &operator=(const T &Val) {
      this->setValue(Val);
      return this->getValue();
    }
  
    template <class... Mods>
    explicit opt(const Mods &... Ms)
        : Option(Optional, NotHidden), Parser(*this) {
      apply(this, Ms...);
      done();
    }
  };
  
  extern template class opt<unsigned>;
  extern template class opt<int>;
  extern template class opt<std::string>;
  extern template class opt<char>;
  extern template class opt<bool>;
  
  //===----------------------------------------------------------------------===//
  // list_storage class
  
  // Default storage class definition: external storage.  This implementation
  // assumes the user will specify a variable to store the data into with the
  // cl::location(x) modifier.
  //
  template <class DataType, class StorageClass> class list_storage {
    StorageClass *Location = nullptr; // Where to store the object...
  
  public:
    list_storage() = default;
  
    bool setLocation(Option &O, StorageClass &L) {
      if (Location)
        return O.error("cl::location(x) specified more than once!");
      Location = &L;
      return false;
    }
  
    template <class T> void addValue(const T &V) {
      assert(Location != 0 && "cl::location(...) not specified for a command "
                              "line option with external storage!");
      Location->push_back(V);
    }
  };
  
  // Define how to hold a class type object, such as a string.
  // Originally this code inherited from std::vector. In transitioning to a new
  // API for command line options we should change this. The new implementation
  // of this list_storage specialization implements the minimum subset of the
  // std::vector API required for all the current clients.
  //
  // FIXME: Reduce this API to a more narrow subset of std::vector
  //
  template <class DataType> class list_storage<DataType, bool> {
    std::vector<DataType> Storage;
  
  public:
    using iterator = typename std::vector<DataType>::iterator;
  
    iterator begin() { return Storage.begin(); }
    iterator end() { return Storage.end(); }
  
    using const_iterator = typename std::vector<DataType>::const_iterator;
  
    const_iterator begin() const { return Storage.begin(); }
    const_iterator end() const { return Storage.end(); }
  
    using size_type = typename std::vector<DataType>::size_type;
  
    size_type size() const { return Storage.size(); }
  
    bool empty() const { return Storage.empty(); }
  
    void push_back(const DataType &value) { Storage.push_back(value); }
    void push_back(DataType &&value) { Storage.push_back(value); }
  
    using reference = typename std::vector<DataType>::reference;
    using const_reference = typename std::vector<DataType>::const_reference;
  
    reference operator[](size_type pos) { return Storage[pos]; }
    const_reference operator[](size_type pos) const { return Storage[pos]; }
  
    iterator erase(const_iterator pos) { return Storage.erase(pos); }
    iterator erase(const_iterator first, const_iterator last) {
      return Storage.erase(first, last);
    }
  
    iterator erase(iterator pos) { return Storage.erase(pos); }
    iterator erase(iterator first, iterator last) {
      return Storage.erase(first, last);
    }
  
    iterator insert(const_iterator pos, const DataType &value) {
      return Storage.insert(pos, value);
    }
    iterator insert(const_iterator pos, DataType &&value) {
      return Storage.insert(pos, value);
    }
  
    iterator insert(iterator pos, const DataType &value) {
      return Storage.insert(pos, value);
    }
    iterator insert(iterator pos, DataType &&value) {
      return Storage.insert(pos, value);
    }
  
    reference front() { return Storage.front(); }
    const_reference front() const { return Storage.front(); }
  
    operator std::vector<DataType>&() { return Storage; }
    operator ArrayRef<DataType>() { return Storage; }
    std::vector<DataType> *operator&() { return &Storage; }
    const std::vector<DataType> *operator&() const { return &Storage; }
  
    template <class T> void addValue(const T &V) { Storage.push_back(V); }
  };
  
  //===----------------------------------------------------------------------===//
  // list - A list of command line options.
  //
  template <class DataType, class StorageClass = bool,
            class ParserClass = parser<DataType>>
  class list : public Option, public list_storage<DataType, StorageClass> {
    std::vector<unsigned> Positions;
    ParserClass Parser;
  
    enum ValueExpected getValueExpectedFlagDefault() const override {
      return Parser.getValueExpectedFlagDefault();
    }
  
    void getExtraOptionNames(SmallVectorImpl<StringRef> &OptionNames) override {
      return Parser.getExtraOptionNames(OptionNames);
    }
  
    bool handleOccurrence(unsigned pos, StringRef ArgName,
                          StringRef Arg) override {
      typename ParserClass::parser_data_type Val =
          typename ParserClass::parser_data_type();
      if (Parser.parse(*this, ArgName, Arg, Val))
        return true; // Parse Error!
      list_storage<DataType, StorageClass>::addValue(Val);
      setPosition(pos);
      Positions.push_back(pos);
      return false;
    }
  
    // Forward printing stuff to the parser...
    size_t getOptionWidth() const override {
      return Parser.getOptionWidth(*this);
    }
  
    void printOptionInfo(size_t GlobalWidth) const override {
      Parser.printOptionInfo(*this, GlobalWidth);
    }
  
    // Unimplemented: list options don't currently store their default value.
    void printOptionValue(size_t /*GlobalWidth*/, bool /*Force*/) const override {
    }
  
    void setDefault() override {}
  
    void done() {
      addArgument();
      Parser.initialize();
    }
  
  public:
    // Command line options should not be copyable
    list(const list &) = delete;
    list &operator=(const list &) = delete;
  
    ParserClass &getParser() { return Parser; }
  
    unsigned getPosition(unsigned optnum) const {
      assert(optnum < this->size() && "Invalid option index");
      return Positions[optnum];
    }
  
    void setNumAdditionalVals(unsigned n) { Option::setNumAdditionalVals(n); }
  
    template <class... Mods>
    explicit list(const Mods &... Ms)
        : Option(ZeroOrMore, NotHidden), Parser(*this) {
      apply(this, Ms...);
      done();
    }
  };
  
  // multi_val - Modifier to set the number of additional values.
  struct multi_val {
    unsigned AdditionalVals;
    explicit multi_val(unsigned N) : AdditionalVals(N) {}
  
    template <typename D, typename S, typename P>
    void apply(list<D, S, P> &L) const {
      L.setNumAdditionalVals(AdditionalVals);
    }
  };
  
  //===----------------------------------------------------------------------===//
  // bits_storage class
  
  // Default storage class definition: external storage.  This implementation
  // assumes the user will specify a variable to store the data into with the
  // cl::location(x) modifier.
  //
  template <class DataType, class StorageClass> class bits_storage {
    unsigned *Location = nullptr; // Where to store the bits...
  
    template <class T> static unsigned Bit(const T &V) {
      unsigned BitPos = reinterpret_cast<unsigned>(V);
      assert(BitPos < sizeof(unsigned) * CHAR_BIT &&
             "enum exceeds width of bit vector!");
      return 1 << BitPos;
    }
  
  public:
    bits_storage() = default;
  
    bool setLocation(Option &O, unsigned &L) {
      if (Location)
        return O.error("cl::location(x) specified more than once!");
      Location = &L;
      return false;
    }
  
    template <class T> void addValue(const T &V) {
      assert(Location != 0 && "cl::location(...) not specified for a command "
                              "line option with external storage!");
      *Location |= Bit(V);
    }
  
    unsigned getBits() { return *Location; }
  
    template <class T> bool isSet(const T &V) {
      return (*Location & Bit(V)) != 0;
    }
  };
  
  // Define how to hold bits.  Since we can inherit from a class, we do so.
  // This makes us exactly compatible with the bits in all cases that it is used.
  //
  template <class DataType> class bits_storage<DataType, bool> {
    unsigned Bits; // Where to store the bits...
  
    template <class T> static unsigned Bit(const T &V) {
      unsigned BitPos = (unsigned)V;
      assert(BitPos < sizeof(unsigned) * CHAR_BIT &&
             "enum exceeds width of bit vector!");
      return 1 << BitPos;
    }
  
  public:
    template <class T> void addValue(const T &V) { Bits |= Bit(V); }
  
    unsigned getBits() { return Bits; }
  
    template <class T> bool isSet(const T &V) { return (Bits & Bit(V)) != 0; }
  };
  
  //===----------------------------------------------------------------------===//
  // bits - A bit vector of command options.
  //
  template <class DataType, class Storage = bool,
            class ParserClass = parser<DataType>>
  class bits : public Option, public bits_storage<DataType, Storage> {
    std::vector<unsigned> Positions;
    ParserClass Parser;
  
    enum ValueExpected getValueExpectedFlagDefault() const override {
      return Parser.getValueExpectedFlagDefault();
    }
  
    void getExtraOptionNames(SmallVectorImpl<StringRef> &OptionNames) override {
      return Parser.getExtraOptionNames(OptionNames);
    }
  
    bool handleOccurrence(unsigned pos, StringRef ArgName,
                          StringRef Arg) override {
      typename ParserClass::parser_data_type Val =
          typename ParserClass::parser_data_type();
      if (Parser.parse(*this, ArgName, Arg, Val))
        return true; // Parse Error!
      this->addValue(Val);
      setPosition(pos);
      Positions.push_back(pos);
      return false;
    }
  
    // Forward printing stuff to the parser...
    size_t getOptionWidth() const override {
      return Parser.getOptionWidth(*this);
    }
  
    void printOptionInfo(size_t GlobalWidth) const override {
      Parser.printOptionInfo(*this, GlobalWidth);
    }
  
    // Unimplemented: bits options don't currently store their default values.
    void printOptionValue(size_t /*GlobalWidth*/, bool /*Force*/) const override {
    }
  
    void setDefault() override {}
  
    void done() {
      addArgument();
      Parser.initialize();
    }
  
  public:
    // Command line options should not be copyable
    bits(const bits &) = delete;
    bits &operator=(const bits &) = delete;
  
    ParserClass &getParser() { return Parser; }
  
    unsigned getPosition(unsigned optnum) const {
      assert(optnum < this->size() && "Invalid option index");
      return Positions[optnum];
    }
  
    template <class... Mods>
    explicit bits(const Mods &... Ms)
        : Option(ZeroOrMore, NotHidden), Parser(*this) {
      apply(this, Ms...);
      done();
    }
  };
  
  //===----------------------------------------------------------------------===//
  // Aliased command line option (alias this name to a preexisting name)
  //
  
  class alias : public Option {
    Option *AliasFor;
  
    bool handleOccurrence(unsigned pos, StringRef /*ArgName*/,
                          StringRef Arg) override {
      return AliasFor->handleOccurrence(pos, AliasFor->ArgStr, Arg);
    }
  
    bool addOccurrence(unsigned pos, StringRef /*ArgName*/, StringRef Value,
                       bool MultiArg = false) override {
      return AliasFor->addOccurrence(pos, AliasFor->ArgStr, Value, MultiArg);
    }
  
    // Handle printing stuff...
    size_t getOptionWidth() const override;
    void printOptionInfo(size_t GlobalWidth) const override;
  
    // Aliases do not need to print their values.
    void printOptionValue(size_t /*GlobalWidth*/, bool /*Force*/) const override {
    }
  
    void setDefault() override { AliasFor->setDefault(); }
  
    ValueExpected getValueExpectedFlagDefault() const override {
      return AliasFor->getValueExpectedFlag();
    }
  
    void done() {
      if (!hasArgStr())
        error("cl::alias must have argument name specified!");
      if (!AliasFor)
        error("cl::alias must have an cl::aliasopt(option) specified!");
      Subs = AliasFor->Subs;
      addArgument();
    }
  
  public:
    // Command line options should not be copyable
    alias(const alias &) = delete;
    alias &operator=(const alias &) = delete;
  
    void setAliasFor(Option &O) {
      if (AliasFor)
        error("cl::alias must only have one cl::aliasopt(...) specified!");
      AliasFor = &O;
    }
  
    template <class... Mods>
    explicit alias(const Mods &... Ms)
        : Option(Optional, Hidden), AliasFor(nullptr) {
      apply(this, Ms...);
      done();
    }
  };
  
  // aliasfor - Modifier to set the option an alias aliases.
  struct aliasopt {
    Option &Opt;
  
    explicit aliasopt(Option &O) : Opt(O) {}
  
    void apply(alias &A) const { A.setAliasFor(Opt); }
  };
  
  // extrahelp - provide additional help at the end of the normal help
  // output. All occurrences of cl::extrahelp will be accumulated and
  // printed to stderr at the end of the regular help, just before
  // exit is called.
  struct extrahelp {
    StringRef morehelp;
  
    explicit extrahelp(StringRef help);
  };
  
  void PrintVersionMessage();
  
  /// This function just prints the help message, exactly the same way as if the
  /// -help or -help-hidden option had been given on the command line.
  ///
  /// \param Hidden if true will print hidden options
  /// \param Categorized if true print options in categories
  void PrintHelpMessage(bool Hidden = false, bool Categorized = false);
  
  //===----------------------------------------------------------------------===//
  // Public interface for accessing registered options.
  //
  
  /// \brief Use this to get a StringMap to all registered named options
  /// (e.g. -help). Note \p Map Should be an empty StringMap.
  ///
  /// \return A reference to the StringMap used by the cl APIs to parse options.
  ///
  /// Access to unnamed arguments (i.e. positional) are not provided because
  /// it is expected that the client already has access to these.
  ///
  /// Typical usage:
  /// \code
  /// main(int argc,char* argv[]) {
  /// StringMap<llvm::cl::Option*> &opts = llvm::cl::getRegisteredOptions();
  /// assert(opts.count("help") == 1)
  /// opts["help"]->setDescription("Show alphabetical help information")
  /// // More code
  /// llvm::cl::ParseCommandLineOptions(argc,argv);
  /// //More code
  /// }
  /// \endcode
  ///
  /// This interface is useful for modifying options in libraries that are out of
  /// the control of the client. The options should be modified before calling
  /// llvm::cl::ParseCommandLineOptions().
  ///
  /// Hopefully this API can be deprecated soon. Any situation where options need
  /// to be modified by tools or libraries should be handled by sane APIs rather
  /// than just handing around a global list.
  StringMap<Option *> &getRegisteredOptions(SubCommand &Sub = *TopLevelSubCommand);
  
  /// \brief Use this to get all registered SubCommands from the provided parser.
  ///
  /// \return A range of all SubCommand pointers registered with the parser.
  ///
  /// Typical usage:
  /// \code
  /// main(int argc, char* argv[]) {
  ///   llvm::cl::ParseCommandLineOptions(argc, argv);
  ///   for (auto* S : llvm::cl::getRegisteredSubcommands()) {
  ///     if (*S) {
  ///       std::cout << "Executing subcommand: " << S->getName() << std::endl;
  ///       // Execute some function based on the name...
  ///     }
  ///   }
  /// }
  /// \endcode
  ///
  /// This interface is useful for defining subcommands in libraries and
  /// the dispatch from a single point (like in the main function).
  iterator_range<typename SmallPtrSet<SubCommand *, 4>::iterator>
  getRegisteredSubcommands();
  
  //===----------------------------------------------------------------------===//
  // Standalone command line processing utilities.
  //
  
  /// \brief Tokenizes a command line that can contain escapes and quotes.
  //
  /// The quoting rules match those used by GCC and other tools that use
  /// libiberty's buildargv() or expandargv() utilities, and do not match bash.
  /// They differ from buildargv() on treatment of backslashes that do not escape
  /// a special character to make it possible to accept most Windows file paths.
  ///
  /// \param [in] Source The string to be split on whitespace with quotes.
  /// \param [in] Saver Delegates back to the caller for saving parsed strings.
  /// \param [in] MarkEOLs true if tokenizing a response file and you want end of
  /// lines and end of the response file to be marked with a nullptr string.
  /// \param [out] NewArgv All parsed strings are appended to NewArgv.
  void TokenizeGNUCommandLine(StringRef Source, StringSaver &Saver,
                              SmallVectorImpl<const char *> &NewArgv,
                              bool MarkEOLs = false);
  
  /// \brief Tokenizes a Windows command line which may contain quotes and escaped
  /// quotes.
  ///
  /// See MSDN docs for CommandLineToArgvW for information on the quoting rules.
  /// http://msdn.microsoft.com/en-us/library/windows/desktop/17w5ykft(v=vs.85).aspx
  ///
  /// \param [in] Source The string to be split on whitespace with quotes.
  /// \param [in] Saver Delegates back to the caller for saving parsed strings.
  /// \param [in] MarkEOLs true if tokenizing a response file and you want end of
  /// lines and end of the response file to be marked with a nullptr string.
  /// \param [out] NewArgv All parsed strings are appended to NewArgv.
  void TokenizeWindowsCommandLine(StringRef Source, StringSaver &Saver,
                                  SmallVectorImpl<const char *> &NewArgv,
                                  bool MarkEOLs = false);
  
  /// \brief String tokenization function type.  Should be compatible with either
  /// Windows or Unix command line tokenizers.
  using TokenizerCallback = void (*)(StringRef Source, StringSaver &Saver,
                                     SmallVectorImpl<const char *> &NewArgv,
                                     bool MarkEOLs);
  
  /// \brief Expand response files on a command line recursively using the given
  /// StringSaver and tokenization strategy.  Argv should contain the command line
  /// before expansion and will be modified in place. If requested, Argv will
  /// also be populated with nullptrs indicating where each response file line
  /// ends, which is useful for the "/link" argument that needs to consume all
  /// remaining arguments only until the next end of line, when in a response
  /// file.
  ///
  /// \param [in] Saver Delegates back to the caller for saving parsed strings.
  /// \param [in] Tokenizer Tokenization strategy. Typically Unix or Windows.
  /// \param [in,out] Argv Command line into which to expand response files.
  /// \param [in] MarkEOLs Mark end of lines and the end of the response file
  /// with nullptrs in the Argv vector.
  /// \param [in] RelativeNames true if names of nested response files must be
  /// resolved relative to including file.
  /// \return true if all @files were expanded successfully or there were none.
  bool ExpandResponseFiles(StringSaver &Saver, TokenizerCallback Tokenizer,
                           SmallVectorImpl<const char *> &Argv,
                           bool MarkEOLs = false, bool RelativeNames = false);
  
  /// \brief Mark all options not part of this category as cl::ReallyHidden.
  ///
  /// \param Category the category of options to keep displaying
  ///
  /// Some tools (like clang-format) like to be able to hide all options that are
  /// not specific to the tool. This function allows a tool to specify a single
  /// option category to display in the -help output.
  void HideUnrelatedOptions(cl::OptionCategory &Category,
                            SubCommand &Sub = *TopLevelSubCommand);
  
  /// \brief Mark all options not part of the categories as cl::ReallyHidden.
  ///
  /// \param Categories the categories of options to keep displaying.
  ///
  /// Some tools (like clang-format) like to be able to hide all options that are
  /// not specific to the tool. This function allows a tool to specify a single
  /// option category to display in the -help output.
  void HideUnrelatedOptions(ArrayRef<const cl::OptionCategory *> Categories,
                            SubCommand &Sub = *TopLevelSubCommand);
  
  /// \brief Reset all command line options to a state that looks as if they have
  /// never appeared on the command line.  This is useful for being able to parse
  /// a command line multiple times (especially useful for writing tests).
  void ResetAllOptionOccurrences();
  
  /// \brief Reset the command line parser back to its initial state.  This
  /// removes
  /// all options, categories, and subcommands and returns the parser to a state
  /// where no options are supported.
  void ResetCommandLineParser();
  
  } // end namespace cl
  
  } // end namespace llvm
  
  #endif // LLVM_SUPPORT_COMMANDLINE_H
  