lib/Support/CommandLine.cpp

//===-- CommandLine.cpp - Command line parser implementation --------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// This 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 could try
// reading the library documentation located in docs/CommandLine.html
//
//===----------------------------------------------------------------------===//

#include "llvm/Support/CommandLine.h"
#include "llvm-c/Support.h"
#include "llvm/ADT/ArrayRef.h"
#include "llvm/ADT/Optional.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/SmallString.h"
#include "llvm/ADT/StringExtras.h"
#include "llvm/ADT/StringMap.h"
#include "llvm/ADT/Triple.h"
#include "llvm/ADT/Twine.h"
#include "llvm/Config/config.h"
#include "llvm/Support/ConvertUTF.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/FileSystem.h"
#include "llvm/Support/Host.h"
#include "llvm/Support/ManagedStatic.h"
#include "llvm/Support/MemoryBuffer.h"
#include "llvm/Support/Path.h"
#include "llvm/Support/Process.h"
#include "llvm/Support/StringSaver.h"
#include "llvm/Support/raw_ostream.h"
#include <cstdlib>
#include <map>
using namespace llvm;
using namespace cl;

#define DEBUG_TYPE "commandline"

//===----------------------------------------------------------------------===//
// Template instantiations and anchors.
//
namespace llvm {
namespace cl {
template class basic_parser<bool>;
template class basic_parser<boolOrDefault>;
template class basic_parser<int>;
template class basic_parser<unsigned>;
template class basic_parser<unsigned long>;
template class basic_parser<unsigned long long>;
template class basic_parser<double>;
template class basic_parser<float>;
template class basic_parser<std::string>;
template class basic_parser<char>;

template class opt<unsigned>;
template class opt<int>;
template class opt<std::string>;
template class opt<char>;
template class opt<bool>;
}
} // end namespace llvm::cl

// Pin the vtables to this file.
void GenericOptionValue::anchor() {}
void OptionValue<boolOrDefault>::anchor() {}
void OptionValue<std::string>::anchor() {}
void Option::anchor() {}
void basic_parser_impl::anchor() {}
void parser<bool>::anchor() {}
void parser<boolOrDefault>::anchor() {}
void parser<int>::anchor() {}
void parser<unsigned>::anchor() {}
void parser<unsigned long>::anchor() {}
void parser<unsigned long long>::anchor() {}
void parser<double>::anchor() {}
void parser<float>::anchor() {}
void parser<std::string>::anchor() {}
void parser<char>::anchor() {}

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

static StringRef ArgPrefix = "  -";
static StringRef ArgPrefixLong = "  --";
static StringRef ArgHelpPrefix = " - ";

static size_t argPlusPrefixesSize(StringRef ArgName) {
  size_t Len = ArgName.size();
  if (Len == 1)
    return Len + ArgPrefix.size() + ArgHelpPrefix.size();
  return Len + ArgPrefixLong.size() + ArgHelpPrefix.size();
}

static StringRef argPrefix(StringRef ArgName) {
  if (ArgName.size() == 1)
    return ArgPrefix;
  return ArgPrefixLong;
}

// Option predicates...
static inline bool isGrouping(const Option *O) {
  return O->getMiscFlags() & cl::Grouping;
}
static inline bool isPrefixedOrGrouping(const Option *O) {
  return isGrouping(O) || O->getFormattingFlag() == cl::Prefix ||
         O->getFormattingFlag() == cl::AlwaysPrefix;
}


namespace {

class PrintArg {
  StringRef ArgName;
public:
  PrintArg(StringRef ArgName) : ArgName(ArgName) {}
  friend raw_ostream &operator<<(raw_ostream &OS, const PrintArg&);
};

raw_ostream &operator<<(raw_ostream &OS, const PrintArg& Arg) {
  OS << argPrefix(Arg.ArgName) << Arg.ArgName;
  return OS;
}

class CommandLineParser {
public:
  // Globals for name and overview of program.  Program name is not a string to
  // avoid static ctor/dtor issues.
  std::string ProgramName;
  StringRef ProgramOverview;

  // This collects additional help to be printed.
  std::vector<StringRef> MoreHelp;

  // This collects Options added with the cl::DefaultOption flag. Since they can
  // be overridden, they are not added to the appropriate SubCommands until
  // ParseCommandLineOptions actually runs.
  SmallVector<Option*, 4> DefaultOptions;

  // This collects the different option categories that have been registered.
  SmallPtrSet<OptionCategory *, 16> RegisteredOptionCategories;

  // This collects the different subcommands that have been registered.
  SmallPtrSet<SubCommand *, 4> RegisteredSubCommands;

  CommandLineParser() : ActiveSubCommand(nullptr) {
    registerSubCommand(&*TopLevelSubCommand);
    registerSubCommand(&*AllSubCommands);
  }

  void ResetAllOptionOccurrences();

  bool ParseCommandLineOptions(int argc, const char *const *argv,
                               StringRef Overview, raw_ostream *Errs = nullptr,
                               bool LongOptionsUseDoubleDash = false);

  void addLiteralOption(Option &Opt, SubCommand *SC, StringRef Name) {
    if (Opt.hasArgStr())
      return;
    if (!SC->OptionsMap.insert(std::make_pair(Name, &Opt)).second) {
      errs() << ProgramName << ": CommandLine Error: Option '" << Name
             << "' registered more than once!\n";
      report_fatal_error("inconsistency in registered CommandLine options");
    }

    // If we're adding this to all sub-commands, add it to the ones that have
    // already been registered.
    if (SC == &*AllSubCommands) {
      for (const auto &Sub : RegisteredSubCommands) {
        if (SC == Sub)
          continue;
        addLiteralOption(Opt, Sub, Name);
      }
    }
  }

  void addLiteralOption(Option &Opt, StringRef Name) {
    if (Opt.Subs.empty())
      addLiteralOption(Opt, &*TopLevelSubCommand, Name);
    else {
      for (auto SC : Opt.Subs)
        addLiteralOption(Opt, SC, Name);
    }
  }

  void addOption(Option *O, SubCommand *SC) {
    bool HadErrors = false;
    if (O->hasArgStr()) {
      // If it's a DefaultOption, check to make sure it isn't already there.
      if (O->isDefaultOption() &&
          SC->OptionsMap.find(O->ArgStr) != SC->OptionsMap.end())
        return;

      // Add argument to the argument map!
      if (!SC->OptionsMap.insert(std::make_pair(O->ArgStr, O)).second) {
        errs() << ProgramName << ": CommandLine Error: Option '" << O->ArgStr
               << "' registered more than once!\n";
        HadErrors = true;
      }
    }

    // Remember information about positional options.
    if (O->getFormattingFlag() == cl::Positional)
      SC->PositionalOpts.push_back(O);
    else if (O->getMiscFlags() & cl::Sink) // Remember sink options
      SC->SinkOpts.push_back(O);
    else if (O->getNumOccurrencesFlag() == cl::ConsumeAfter) {
      if (SC->ConsumeAfterOpt) {
        O->error("Cannot specify more than one option with cl::ConsumeAfter!");
        HadErrors = true;
      }
      SC->ConsumeAfterOpt = O;
    }

    // Fail hard if there were errors. These are strictly unrecoverable and
    // indicate serious issues such as conflicting option names or an
    // incorrectly
    // linked LLVM distribution.
    if (HadErrors)
      report_fatal_error("inconsistency in registered CommandLine options");

    // If we're adding this to all sub-commands, add it to the ones that have
    // already been registered.
    if (SC == &*AllSubCommands) {
      for (const auto &Sub : RegisteredSubCommands) {
        if (SC == Sub)
          continue;
        addOption(O, Sub);
      }
    }
  }

  void addOption(Option *O, bool ProcessDefaultOption = false) {
    if (!ProcessDefaultOption && O->isDefaultOption()) {
      DefaultOptions.push_back(O);
      return;
    }

    if (O->Subs.empty()) {
      addOption(O, &*TopLevelSubCommand);
    } else {
      for (auto SC : O->Subs)
        addOption(O, SC);
    }
  }

  void removeOption(Option *O, SubCommand *SC) {
    SmallVector<StringRef, 16> OptionNames;
    O->getExtraOptionNames(OptionNames);
    if (O->hasArgStr())
      OptionNames.push_back(O->ArgStr);

    SubCommand &Sub = *SC;
    auto End = Sub.OptionsMap.end();
    for (auto Name : OptionNames) {
      auto I = Sub.OptionsMap.find(Name);
      if (I != End && I->getValue() == O)
        Sub.OptionsMap.erase(I);
      }

    if (O->getFormattingFlag() == cl::Positional)
      for (auto Opt = Sub.PositionalOpts.begin();
           Opt != Sub.PositionalOpts.end(); ++Opt) {
        if (*Opt == O) {
          Sub.PositionalOpts.erase(Opt);
          break;
        }
      }
    else if (O->getMiscFlags() & cl::Sink)
      for (auto Opt = Sub.SinkOpts.begin(); Opt != Sub.SinkOpts.end(); ++Opt) {
        if (*Opt == O) {
          Sub.SinkOpts.erase(Opt);
          break;
        }
      }
    else if (O == Sub.ConsumeAfterOpt)
      Sub.ConsumeAfterOpt = nullptr;
  }

  void removeOption(Option *O) {
    if (O->Subs.empty())
      removeOption(O, &*TopLevelSubCommand);
    else {
      if (O->isInAllSubCommands()) {
        for (auto SC : RegisteredSubCommands)
          removeOption(O, SC);
      } else {
        for (auto SC : O->Subs)
          removeOption(O, SC);
      }
    }
  }

  bool hasOptions(const SubCommand &Sub) const {
    return (!Sub.OptionsMap.empty() || !Sub.PositionalOpts.empty() ||
            nullptr != Sub.ConsumeAfterOpt);
  }

  bool hasOptions() const {
    for (const auto &S : RegisteredSubCommands) {
      if (hasOptions(*S))
        return true;
    }
    return false;
  }

  SubCommand *getActiveSubCommand() { return ActiveSubCommand; }

  void updateArgStr(Option *O, StringRef NewName, SubCommand *SC) {
    SubCommand &Sub = *SC;
    if (!Sub.OptionsMap.insert(std::make_pair(NewName, O)).second) {
      errs() << ProgramName << ": CommandLine Error: Option '" << O->ArgStr
             << "' registered more than once!\n";
      report_fatal_error("inconsistency in registered CommandLine options");
    }
    Sub.OptionsMap.erase(O->ArgStr);
  }

  void updateArgStr(Option *O, StringRef NewName) {
    if (O->Subs.empty())
      updateArgStr(O, NewName, &*TopLevelSubCommand);
    else {
      if (O->isInAllSubCommands()) {
        for (auto SC : RegisteredSubCommands)
          updateArgStr(O, NewName, SC);
      } else {
        for (auto SC : O->Subs)
          updateArgStr(O, NewName, SC);
      }
    }
  }

  void printOptionValues();

  void registerCategory(OptionCategory *cat) {
    assert(count_if(RegisteredOptionCategories,
                    [cat](const OptionCategory *Category) {
             return cat->getName() == Category->getName();
           }) == 0 &&
           "Duplicate option categories");

    RegisteredOptionCategories.insert(cat);
  }

  void registerSubCommand(SubCommand *sub) {
    assert(count_if(RegisteredSubCommands,
                    [sub](const SubCommand *Sub) {
                      return (!sub->getName().empty()) &&
                             (Sub->getName() == sub->getName());
                    }) == 0 &&
           "Duplicate subcommands");
    RegisteredSubCommands.insert(sub);

    // For all options that have been registered for all subcommands, add the
    // option to this subcommand now.
    if (sub != &*AllSubCommands) {
      for (auto &E : AllSubCommands->OptionsMap) {
        Option *O = E.second;
        if ((O->isPositional() || O->isSink() || O->isConsumeAfter()) ||
            O->hasArgStr())
          addOption(O, sub);
        else
          addLiteralOption(*O, sub, E.first());
      }
    }
  }

  void unregisterSubCommand(SubCommand *sub) {
    RegisteredSubCommands.erase(sub);
  }

  iterator_range<typename SmallPtrSet<SubCommand *, 4>::iterator>
  getRegisteredSubcommands() {
    return make_range(RegisteredSubCommands.begin(),
                      RegisteredSubCommands.end());
  }

  void reset() {
    ActiveSubCommand = nullptr;
    ProgramName.clear();
    ProgramOverview = StringRef();

    MoreHelp.clear();
    RegisteredOptionCategories.clear();

    ResetAllOptionOccurrences();
    RegisteredSubCommands.clear();

    TopLevelSubCommand->reset();
    AllSubCommands->reset();
    registerSubCommand(&*TopLevelSubCommand);
    registerSubCommand(&*AllSubCommands);

    DefaultOptions.clear();
  }

private:
  SubCommand *ActiveSubCommand;

  Option *LookupOption(SubCommand &Sub, StringRef &Arg, StringRef &Value);
  Option *LookupLongOption(SubCommand &Sub, StringRef &Arg, StringRef &Value,
                           bool LongOptionsUseDoubleDash, bool HaveDoubleDash) {
    Option *Opt = LookupOption(Sub, Arg, Value);
    if (Opt && LongOptionsUseDoubleDash && !HaveDoubleDash && !isGrouping(Opt))
      return nullptr;
    return Opt;
  }
  SubCommand *LookupSubCommand(StringRef Name);
};

} // namespace

static ManagedStatic<CommandLineParser> GlobalParser;

void cl::AddLiteralOption(Option &O, StringRef Name) {
  GlobalParser->addLiteralOption(O, Name);
}

extrahelp::extrahelp(StringRef Help) : morehelp(Help) {
  GlobalParser->MoreHelp.push_back(Help);
}

void Option::addArgument() {
  GlobalParser->addOption(this);
  FullyInitialized = true;
}

void Option::removeArgument() { GlobalParser->removeOption(this); }

void Option::setArgStr(StringRef S) {
  if (FullyInitialized)
    GlobalParser->updateArgStr(this, S);
  assert((S.empty() || S[0] != '-') && "Option can't start with '-");
  ArgStr = S;
  if (ArgStr.size() == 1)
    setMiscFlag(Grouping);
}

void Option::addCategory(OptionCategory &C) {
  assert(!Categories.empty() && "Categories cannot be empty.");
  // Maintain backward compatibility by replacing the default GeneralCategory
  // if it's still set.  Otherwise, just add the new one.  The GeneralCategory
  // must be explicitly added if you want multiple categories that include it.
  if (&C != &GeneralCategory && Categories[0] == &GeneralCategory)
    Categories[0] = &C;
  else if (find(Categories, &C) == Categories.end())
    Categories.push_back(&C);
}

void Option::reset() {
  NumOccurrences = 0;
  setDefault();
  if (isDefaultOption())
    removeArgument();
}

// Initialise the general option category.
OptionCategory llvm::cl::GeneralCategory("General options");

void OptionCategory::registerCategory() {
  GlobalParser->registerCategory(this);
}

// A special subcommand representing no subcommand. It is particularly important
// that this ManagedStatic uses constant initailization and not dynamic
// initialization because it is referenced from cl::opt constructors, which run
// dynamically in an arbitrary order.
LLVM_REQUIRE_CONSTANT_INITIALIZATION
ManagedStatic<SubCommand> llvm::cl::TopLevelSubCommand;

// A special subcommand that can be used to put an option into all subcommands.
ManagedStatic<SubCommand> llvm::cl::AllSubCommands;

void SubCommand::registerSubCommand() {
  GlobalParser->registerSubCommand(this);
}

void SubCommand::unregisterSubCommand() {
  GlobalParser->unregisterSubCommand(this);
}

void SubCommand::reset() {
  PositionalOpts.clear();
  SinkOpts.clear();
  OptionsMap.clear();

  ConsumeAfterOpt = nullptr;
}

SubCommand::operator bool() const {
  return (GlobalParser->getActiveSubCommand() == this);
}

//===----------------------------------------------------------------------===//
// Basic, shared command line option processing machinery.
//

/// LookupOption - Lookup the option specified by the specified option on the
/// command line.  If there is a value specified (after an equal sign) return
/// that as well.  This assumes that leading dashes have already been stripped.
Option *CommandLineParser::LookupOption(SubCommand &Sub, StringRef &Arg,
                                        StringRef &Value) {
  // Reject all dashes.
  if (Arg.empty())
    return nullptr;
  assert(&Sub != &*AllSubCommands);

  size_t EqualPos = Arg.find('=');

  // If we have an equals sign, remember the value.
  if (EqualPos == StringRef::npos) {
    // Look up the option.
    auto I = Sub.OptionsMap.find(Arg);
    if (I == Sub.OptionsMap.end())
      return nullptr;

    return I != Sub.OptionsMap.end() ? I->second : nullptr;
  }

  // If the argument before the = is a valid option name and the option allows
  // non-prefix form (ie is not AlwaysPrefix), we match.  If not, signal match
  // failure by returning nullptr.
  auto I = Sub.OptionsMap.find(Arg.substr(0, EqualPos));
  if (I == Sub.OptionsMap.end())
    return nullptr;

  auto O = I->second;
  if (O->getFormattingFlag() == cl::AlwaysPrefix)
    return nullptr;

  Value = Arg.substr(EqualPos + 1);
  Arg = Arg.substr(0, EqualPos);
  return I->second;
}

SubCommand *CommandLineParser::LookupSubCommand(StringRef Name) {
  if (Name.empty())
    return &*TopLevelSubCommand;
  for (auto S : RegisteredSubCommands) {
    if (S == &*AllSubCommands)
      continue;
    if (S->getName().empty())
      continue;

    if (StringRef(S->getName()) == StringRef(Name))
      return S;
  }
  return &*TopLevelSubCommand;
}

/// LookupNearestOption - Lookup the closest match to the option specified by
/// the specified option on the command line.  If there is a value specified
/// (after an equal sign) return that as well.  This assumes that leading dashes
/// have already been stripped.
static Option *LookupNearestOption(StringRef Arg,
                                   const StringMap<Option *> &OptionsMap,
                                   std::string &NearestString) {
  // Reject all dashes.
  if (Arg.empty())
    return nullptr;

  // Split on any equal sign.
  std::pair<StringRef, StringRef> SplitArg = Arg.split('=');
  StringRef &LHS = SplitArg.first; // LHS == Arg when no '=' is present.
  StringRef &RHS = SplitArg.second;

  // Find the closest match.
  Option *Best = nullptr;
  unsigned BestDistance = 0;
  for (StringMap<Option *>::const_iterator it = OptionsMap.begin(),
                                           ie = OptionsMap.end();
       it != ie; ++it) {
    Option *O = it->second;
    SmallVector<StringRef, 16> OptionNames;
    O->getExtraOptionNames(OptionNames);
    if (O->hasArgStr())
      OptionNames.push_back(O->ArgStr);

    bool PermitValue = O->getValueExpectedFlag() != cl::ValueDisallowed;
    StringRef Flag = PermitValue ? LHS : Arg;
    for (auto Name : OptionNames) {
      unsigned Distance = StringRef(Name).edit_distance(
          Flag, /*AllowReplacements=*/true, /*MaxEditDistance=*/BestDistance);
      if (!Best || Distance < BestDistance) {
        Best = O;
        BestDistance = Distance;
        if (RHS.empty() || !PermitValue)
          NearestString = Name;
        else
          NearestString = (Twine(Name) + "=" + RHS).str();
      }
    }
  }

  return Best;
}

/// CommaSeparateAndAddOccurrence - A wrapper around Handler->addOccurrence()
/// that does special handling of cl::CommaSeparated options.
static bool CommaSeparateAndAddOccurrence(Option *Handler, unsigned pos,
                                          StringRef ArgName, StringRef Value,
                                          bool MultiArg = false) {
  // Check to see if this option accepts a comma separated list of values.  If
  // it does, we have to split up the value into multiple values.
  if (Handler->getMiscFlags() & CommaSeparated) {
    StringRef Val(Value);
    StringRef::size_type Pos = Val.find(',');

    while (Pos != StringRef::npos) {
      // Process the portion before the comma.
      if (Handler->addOccurrence(pos, ArgName, Val.substr(0, Pos), MultiArg))
        return true;
      // Erase the portion before the comma, AND the comma.
      Val = Val.substr(Pos + 1);
      // Check for another comma.
      Pos = Val.find(',');
    }

    Value = Val;
  }

  return Handler->addOccurrence(pos, ArgName, Value, MultiArg);
}

/// ProvideOption - For Value, this differentiates between an empty value ("")
/// and a null value (StringRef()).  The later is accepted for arguments that
/// don't allow a value (-foo) the former is rejected (-foo=).
static inline bool ProvideOption(Option *Handler, StringRef ArgName,
                                 StringRef Value, int argc,
                                 const char *const *argv, int &i) {
  // Is this a multi-argument option?
  unsigned NumAdditionalVals = Handler->getNumAdditionalVals();

  // Enforce value requirements
  switch (Handler->getValueExpectedFlag()) {
  case ValueRequired:
    if (!Value.data()) { // No value specified?
      // If no other argument or the option only supports prefix form, we
      // cannot look at the next argument.
      if (i + 1 >= argc || Handler->getFormattingFlag() == cl::AlwaysPrefix)
        return Handler->error("requires a value!");
      // Steal the next argument, like for '-o filename'
      assert(argv && "null check");
      Value = StringRef(argv[++i]);
    }
    break;
  case ValueDisallowed:
    if (NumAdditionalVals > 0)
      return Handler->error("multi-valued option specified"
                            " with ValueDisallowed modifier!");

    if (Value.data())
      return Handler->error("does not allow a value! '" + Twine(Value) +
                            "' specified.");
    break;
  case ValueOptional:
    break;
  }

  // If this isn't a multi-arg option, just run the handler.
  if (NumAdditionalVals == 0)
    return CommaSeparateAndAddOccurrence(Handler, i, ArgName, Value);

  // If it is, run the handle several times.
  bool MultiArg = false;

  if (Value.data()) {
    if (CommaSeparateAndAddOccurrence(Handler, i, ArgName, Value, MultiArg))
      return true;
    --NumAdditionalVals;
    MultiArg = true;
  }

  while (NumAdditionalVals > 0) {
    if (i + 1 >= argc)
      return Handler->error("not enough values!");
    assert(argv && "null check");
    Value = StringRef(argv[++i]);

    if (CommaSeparateAndAddOccurrence(Handler, i, ArgName, Value, MultiArg))
      return true;
    MultiArg = true;
    --NumAdditionalVals;
  }
  return false;
}

bool llvm::cl::ProvidePositionalOption(Option *Handler, StringRef Arg, int i) {
  int Dummy = i;
  return ProvideOption(Handler, Handler->ArgStr, Arg, 0, nullptr, Dummy);
}

// getOptionPred - Check to see if there are any options that satisfy the
// specified predicate with names that are the prefixes in Name.  This is
// checked by progressively stripping characters off of the name, checking to
// see if there options that satisfy the predicate.  If we find one, return it,
// otherwise return null.
//
static Option *getOptionPred(StringRef Name, size_t &Length,
                             bool (*Pred)(const Option *),
                             const StringMap<Option *> &OptionsMap) {
  StringMap<Option *>::const_iterator OMI = OptionsMap.find(Name);
  if (OMI != OptionsMap.end() && !Pred(OMI->getValue()))
    OMI = OptionsMap.end();

  // Loop while we haven't found an option and Name still has at least two
  // characters in it (so that the next iteration will not be the empty
  // string.
  while (OMI == OptionsMap.end() && Name.size() > 1) {
    Name = Name.substr(0, Name.size() - 1); // Chop off the last character.
    OMI = OptionsMap.find(Name);
    if (OMI != OptionsMap.end() && !Pred(OMI->getValue()))
      OMI = OptionsMap.end();
  }

  if (OMI != OptionsMap.end() && Pred(OMI->second)) {
    Length = Name.size();
    return OMI->second; // Found one!
  }
  return nullptr; // No option found!
}

/// HandlePrefixedOrGroupedOption - The specified argument string (which started
/// with at least one '-') does not fully match an available option.  Check to
/// see if this is a prefix or grouped option.  If so, split arg into output an
/// Arg/Value pair and return the Option to parse it with.
static Option *
HandlePrefixedOrGroupedOption(StringRef &Arg, StringRef &Value,
                              bool &ErrorParsing,
                              const StringMap<Option *> &OptionsMap) {
  if (Arg.size() == 1)
    return nullptr;

  // Do the lookup!
  size_t Length = 0;
  Option *PGOpt = getOptionPred(Arg, Length, isPrefixedOrGrouping, OptionsMap);
  if (!PGOpt)
    return nullptr;

  do {
    StringRef MaybeValue =
        (Length < Arg.size()) ? Arg.substr(Length) : StringRef();
    Arg = Arg.substr(0, Length);
    assert(OptionsMap.count(Arg) && OptionsMap.find(Arg)->second == PGOpt);

    // cl::Prefix options do not preserve '=' when used separately.
    // The behavior for them with grouped options should be the same.
    if (MaybeValue.empty() || PGOpt->getFormattingFlag() == cl::AlwaysPrefix ||
        (PGOpt->getFormattingFlag() == cl::Prefix && MaybeValue[0] != '=')) {
      Value = MaybeValue;
      return PGOpt;
    }

    if (MaybeValue[0] == '=') {
      Value = MaybeValue.substr(1);
      return PGOpt;
    }

    // This must be a grouped option.
    assert(isGrouping(PGOpt) && "Broken getOptionPred!");

    // Grouping options inside a group can't have values.
    if (PGOpt->getValueExpectedFlag() == cl::ValueRequired) {
      ErrorParsing |= PGOpt->error("may not occur within a group!");
      return nullptr;
    }

    // Because the value for the option is not required, we don't need to pass
    // argc/argv in.
    int Dummy = 0;
    ErrorParsing |= ProvideOption(PGOpt, Arg, StringRef(), 0, nullptr, Dummy);

    // Get the next grouping option.
    Arg = MaybeValue;
    PGOpt = getOptionPred(Arg, Length, isGrouping, OptionsMap);
  } while (PGOpt);

  // We could not find a grouping option in the remainder of Arg.
  return nullptr;
}

static bool RequiresValue(const Option *O) {
  return O->getNumOccurrencesFlag() == cl::Required ||
         O->getNumOccurrencesFlag() == cl::OneOrMore;
}

static bool EatsUnboundedNumberOfValues(const Option *O) {
  return O->getNumOccurrencesFlag() == cl::ZeroOrMore ||
         O->getNumOccurrencesFlag() == cl::OneOrMore;
}

static bool isWhitespace(char C) {
  return C == ' ' || C == '\t' || C == '\r' || C == '\n';
}

static bool isWhitespaceOrNull(char C) {
  return isWhitespace(C) || C == '\0';
}

static bool isQuote(char C) { return C == '\"' || C == '\''; }

void cl::TokenizeGNUCommandLine(StringRef Src, StringSaver &Saver,
                                SmallVectorImpl<const char *> &NewArgv,
                                bool MarkEOLs) {
  SmallString<128> Token;
  for (size_t I = 0, E = Src.size(); I != E; ++I) {
    // Consume runs of whitespace.
    if (Token.empty()) {
      while (I != E && isWhitespace(Src[I])) {
        // Mark the end of lines in response files
        if (MarkEOLs && Src[I] == '\n')
          NewArgv.push_back(nullptr);
        ++I;
      }
      if (I == E)
        break;
    }

    char C = Src[I];

    // Backslash escapes the next character.
    if (I + 1 < E && C == '\\') {
      ++I; // Skip the escape.
      Token.push_back(Src[I]);
      continue;
    }

    // Consume a quoted string.
    if (isQuote(C)) {
      ++I;
      while (I != E && Src[I] != C) {
        // Backslash escapes the next character.
        if (Src[I] == '\\' && I + 1 != E)
          ++I;
        Token.push_back(Src[I]);
        ++I;
      }
      if (I == E)
        break;
      continue;
    }

    // End the token if this is whitespace.
    if (isWhitespace(C)) {
      if (!Token.empty())
        NewArgv.push_back(Saver.save(StringRef(Token)).data());
      Token.clear();
      continue;
    }

    // This is a normal character.  Append it.
    Token.push_back(C);
  }

  // Append the last token after hitting EOF with no whitespace.
  if (!Token.empty())
    NewArgv.push_back(Saver.save(StringRef(Token)).data());
  // Mark the end of response files
  if (MarkEOLs)
    NewArgv.push_back(nullptr);
}

/// Backslashes are interpreted in a rather complicated way in the Windows-style
/// command line, because backslashes are used both to separate path and to
/// escape double quote. This method consumes runs of backslashes as well as the
/// following double quote if it's escaped.
///
///  * If an even number of backslashes is followed by a double quote, one
///    backslash is output for every pair of backslashes, and the last double
///    quote remains unconsumed. The double quote will later be interpreted as
///    the start or end of a quoted string in the main loop outside of this
///    function.
///
///  * If an odd number of backslashes is followed by a double quote, one
///    backslash is output for every pair of backslashes, and a double quote is
///    output for the last pair of backslash-double quote. The double quote is
///    consumed in this case.
///
///  * Otherwise, backslashes are interpreted literally.
static size_t parseBackslash(StringRef Src, size_t I, SmallString<128> &Token) {
  size_t E = Src.size();
  int BackslashCount = 0;
  // Skip the backslashes.
  do {
    ++I;
    ++BackslashCount;
  } while (I != E && Src[I] == '\\');

  bool FollowedByDoubleQuote = (I != E && Src[I] == '"');
  if (FollowedByDoubleQuote) {
    Token.append(BackslashCount / 2, '\\');
    if (BackslashCount % 2 == 0)
      return I - 1;
    Token.push_back('"');
    return I;
  }
  Token.append(BackslashCount, '\\');
  return I - 1;
}

void cl::TokenizeWindowsCommandLine(StringRef Src, StringSaver &Saver,
                                    SmallVectorImpl<const char *> &NewArgv,
                                    bool MarkEOLs) {
  SmallString<128> Token;

  // This is a small state machine to consume characters until it reaches the
  // end of the source string.
  enum { INIT, UNQUOTED, QUOTED } State = INIT;
  for (size_t I = 0, E = Src.size(); I != E; ++I) {
    char C = Src[I];

    // INIT state indicates that the current input index is at the start of
    // the string or between tokens.
    if (State == INIT) {
      if (isWhitespaceOrNull(C)) {
        // Mark the end of lines in response files
        if (MarkEOLs && C == '\n')
          NewArgv.push_back(nullptr);
        continue;
      }
      if (C == '"') {
        State = QUOTED;
        continue;
      }
      if (C == '\\') {
        I = parseBackslash(Src, I, Token);
        State = UNQUOTED;
        continue;
      }
      Token.push_back(C);
      State = UNQUOTED;
      continue;
    }

    // UNQUOTED state means that it's reading a token not quoted by double
    // quotes.
    if (State == UNQUOTED) {
      // Whitespace means the end of the token.
      if (isWhitespaceOrNull(C)) {
        NewArgv.push_back(Saver.save(StringRef(Token)).data());
        Token.clear();
        State = INIT;
        // Mark the end of lines in response files
        if (MarkEOLs && C == '\n')
          NewArgv.push_back(nullptr);
        continue;
      }
      if (C == '"') {
        State = QUOTED;
        continue;
      }
      if (C == '\\') {
        I = parseBackslash(Src, I, Token);
        continue;
      }
      Token.push_back(C);
      continue;
    }

    // QUOTED state means that it's reading a token quoted by double quotes.
    if (State == QUOTED) {
      if (C == '"') {
        if (I < (E - 1) && Src[I + 1] == '"') {
          // Consecutive double-quotes inside a quoted string implies one
          // double-quote.
          Token.push_back('"');
          I = I + 1;
          continue;
        }
        State = UNQUOTED;
        continue;
      }
      if (C == '\\') {
        I = parseBackslash(Src, I, Token);
        continue;
      }
      Token.push_back(C);
    }
  }
  // Append the last token after hitting EOF with no whitespace.
  if (!Token.empty())
    NewArgv.push_back(Saver.save(StringRef(Token)).data());
  // Mark the end of response files
  if (MarkEOLs)
    NewArgv.push_back(nullptr);
}

void cl::tokenizeConfigFile(StringRef Source, StringSaver &Saver,
                            SmallVectorImpl<const char *> &NewArgv,
                            bool MarkEOLs) {
  for (const char *Cur = Source.begin(); Cur != Source.end();) {
    SmallString<128> Line;
    // Check for comment line.
    if (isWhitespace(*Cur)) {
      while (Cur != Source.end() && isWhitespace(*Cur))
        ++Cur;
      continue;
    }
    if (*Cur == '#') {
      while (Cur != Source.end() && *Cur != '\n')
        ++Cur;
      continue;
    }
    // Find end of the current line.
    const char *Start = Cur;
    for (const char *End = Source.end(); Cur != End; ++Cur) {
      if (*Cur == '\\') {
        if (Cur + 1 != End) {
          ++Cur;
          if (*Cur == '\n' ||
              (*Cur == '\r' && (Cur + 1 != End) && Cur[1] == '\n')) {
            Line.append(Start, Cur - 1);
            if (*Cur == '\r')
              ++Cur;
            Start = Cur + 1;
          }
        }
      } else if (*Cur == '\n')
        break;
    }
    // Tokenize line.
    Line.append(Start, Cur);
    cl::TokenizeGNUCommandLine(Line, Saver, NewArgv, MarkEOLs);
  }
}

// It is called byte order marker but the UTF-8 BOM is actually not affected
// by the host system's endianness.
static bool hasUTF8ByteOrderMark(ArrayRef<char> S) {
  return (S.size() >= 3 && S[0] == '\xef' && S[1] == '\xbb' && S[2] == '\xbf');
}

static bool ExpandResponseFile(StringRef FName, StringSaver &Saver,
                               TokenizerCallback Tokenizer,
                               SmallVectorImpl<const char *> &NewArgv,
                               bool MarkEOLs, bool RelativeNames) {
  ErrorOr<std::unique_ptr<MemoryBuffer>> MemBufOrErr =
      MemoryBuffer::getFile(FName);
  if (!MemBufOrErr)
    return false;
  MemoryBuffer &MemBuf = *MemBufOrErr.get();
  StringRef Str(MemBuf.getBufferStart(), MemBuf.getBufferSize());

  // If we have a UTF-16 byte order mark, convert to UTF-8 for parsing.
  ArrayRef<char> BufRef(MemBuf.getBufferStart(), MemBuf.getBufferEnd());
  std::string UTF8Buf;
  if (hasUTF16ByteOrderMark(BufRef)) {
    if (!convertUTF16ToUTF8String(BufRef, UTF8Buf))
      return false;
    Str = StringRef(UTF8Buf);
  }
  // If we see UTF-8 BOM sequence at the beginning of a file, we shall remove
  // these bytes before parsing.
  // Reference: http://en.wikipedia.org/wiki/UTF-8#Byte_order_mark
  else if (hasUTF8ByteOrderMark(BufRef))
    Str = StringRef(BufRef.data() + 3, BufRef.size() - 3);

  // Tokenize the contents into NewArgv.
  Tokenizer(Str, Saver, NewArgv, MarkEOLs);

  // If names of nested response files should be resolved relative to including
  // file, replace the included response file names with their full paths
  // obtained by required resolution.
  if (RelativeNames)
    for (unsigned I = 0; I < NewArgv.size(); ++I)
      if (NewArgv[I]) {
        StringRef Arg = NewArgv[I];
        if (Arg.front() == '@') {
          StringRef FileName = Arg.drop_front();
          if (llvm::sys::path::is_relative(FileName)) {
            SmallString<128> ResponseFile;
            ResponseFile.append(1, '@');
            if (llvm::sys::path::is_relative(FName)) {
              SmallString<128> curr_dir;
              llvm::sys::fs::current_path(curr_dir);
              ResponseFile.append(curr_dir.str());
            }
            llvm::sys::path::append(
                ResponseFile, llvm::sys::path::parent_path(FName), FileName);
            NewArgv[I] = Saver.save(ResponseFile.c_str()).data();
          }
        }
      }

  return true;
}

/// Expand response files on a command line recursively using the given
/// StringSaver and tokenization strategy.
bool cl::ExpandResponseFiles(StringSaver &Saver, TokenizerCallback Tokenizer,
                             SmallVectorImpl<const char *> &Argv,
                             bool MarkEOLs, bool RelativeNames) {
  bool AllExpanded = true;
  struct ResponseFileRecord {
    const char *File;
    size_t End;
  };

  // To detect recursive response files, we maintain a stack of files and the
  // position of the last argument in the file. This position is updated
  // dynamically as we recursively expand files.
  SmallVector<ResponseFileRecord, 3> FileStack;

  // Push a dummy entry that represents the initial command line, removing
  // the need to check for an empty list.
  FileStack.push_back({"", Argv.size()});

  // Don't cache Argv.size() because it can change.
  for (unsigned I = 0; I != Argv.size();) {
    while (I == FileStack.back().End) {
      // Passing the end of a file's argument list, so we can remove it from the
      // stack.
      FileStack.pop_back();
    }

    const char *Arg = Argv[I];
    // Check if it is an EOL marker
    if (Arg == nullptr) {
      ++I;
      continue;
    }

    if (Arg[0] != '@') {
      ++I;
      continue;
    }

    const char *FName = Arg + 1;
    auto IsEquivalent = [FName](const ResponseFileRecord &RFile) {
      return sys::fs::equivalent(RFile.File, FName);
    };

    // Check for recursive response files.
    if (std::any_of(FileStack.begin() + 1, FileStack.end(), IsEquivalent)) {
      // This file is recursive, so we leave it in the argument stream and
      // move on.
      AllExpanded = false;
      ++I;
      continue;
    }

    // Replace this response file argument with the tokenization of its
    // contents.  Nested response files are expanded in subsequent iterations.
    SmallVector<const char *, 0> ExpandedArgv;
    if (!ExpandResponseFile(FName, Saver, Tokenizer, ExpandedArgv, MarkEOLs,
                            RelativeNames)) {
      // We couldn't read this file, so we leave it in the argument stream and
      // move on.
      AllExpanded = false;
      ++I;
      continue;
    }

    for (ResponseFileRecord &Record : FileStack) {
      // Increase the end of all active records by the number of newly expanded
      // arguments, minus the response file itself.
      Record.End += ExpandedArgv.size() - 1;
    }

    FileStack.push_back({FName, I + ExpandedArgv.size()});
    Argv.erase(Argv.begin() + I);
    Argv.insert(Argv.begin() + I, ExpandedArgv.begin(), ExpandedArgv.end());
  }

  // If successful, the top of the file stack will mark the end of the Argv
  // stream. A failure here indicates a bug in the stack popping logic above.
  // Note that FileStack may have more than one element at this point because we
  // don't have a chance to pop the stack when encountering recursive files at
  // the end of the stream, so seeing that doesn't indicate a bug.
  assert(FileStack.size() > 0 && Argv.size() == FileStack.back().End);
  return AllExpanded;
}

bool cl::readConfigFile(StringRef CfgFile, StringSaver &Saver,
                        SmallVectorImpl<const char *> &Argv) {
  if (!ExpandResponseFile(CfgFile, Saver, cl::tokenizeConfigFile, Argv,
                          /*MarkEOLs*/ false, /*RelativeNames*/ true))
    return false;
  return ExpandResponseFiles(Saver, cl::tokenizeConfigFile, Argv,
                             /*MarkEOLs*/ false, /*RelativeNames*/ true);
}

/// ParseEnvironmentOptions - An alternative entry point to the
/// CommandLine library, which allows you to read the program's name
/// from the caller (as PROGNAME) and its command-line arguments from
/// an environment variable (whose name is given in ENVVAR).
///
void cl::ParseEnvironmentOptions(const char *progName, const char *envVar,
                                 const char *Overview) {
  // Check args.
  assert(progName && "Program name not specified");
  assert(envVar && "Environment variable name missing");

  // Get the environment variable they want us to parse options out of.
  llvm::Optional<std::string> envValue = sys::Process::GetEnv(StringRef(envVar));
  if (!envValue)
    return;

  // Get program's "name", which we wouldn't know without the caller
  // telling us.
  SmallVector<const char *, 20> newArgv;
  BumpPtrAllocator A;
  StringSaver Saver(A);
  newArgv.push_back(Saver.save(progName).data());

  // Parse the value of the environment variable into a "command line"
  // and hand it off to ParseCommandLineOptions().
  TokenizeGNUCommandLine(*envValue, Saver, newArgv);
  int newArgc = static_cast<int>(newArgv.size());
  ParseCommandLineOptions(newArgc, &newArgv[0], StringRef(Overview));
}

bool cl::ParseCommandLineOptions(int argc, const char *const *argv,
                                 StringRef Overview, raw_ostream *Errs,
                                 const char *EnvVar,
                                 bool LongOptionsUseDoubleDash) {
  SmallVector<const char *, 20> NewArgv;
  BumpPtrAllocator A;
  StringSaver Saver(A);
  NewArgv.push_back(argv[0]);

  // Parse options from environment variable.
  if (EnvVar) {
    if (llvm::Optional<std::string> EnvValue =
            sys::Process::GetEnv(StringRef(EnvVar)))
      TokenizeGNUCommandLine(*EnvValue, Saver, NewArgv);
  }

  // Append options from command line.
  for (int I = 1; I < argc; ++I)
    NewArgv.push_back(argv[I]);
  int NewArgc = static_cast<int>(NewArgv.size());

  // Parse all options.
  return GlobalParser->ParseCommandLineOptions(NewArgc, &NewArgv[0], Overview,
                                               Errs, LongOptionsUseDoubleDash);
}

void CommandLineParser::ResetAllOptionOccurrences() {
  // So that we can parse different command lines multiple times in succession
  // we reset all option values to look like they have never been seen before.
  for (auto SC : RegisteredSubCommands) {
    for (auto &O : SC->OptionsMap)
      O.second->reset();
  }
}

bool CommandLineParser::ParseCommandLineOptions(int argc,
                                                const char *const *argv,
                                                StringRef Overview,
                                                raw_ostream *Errs,
                                                bool LongOptionsUseDoubleDash) {
  assert(hasOptions() && "No options specified!");

  // Expand response files.
  SmallVector<const char *, 20> newArgv(argv, argv + argc);
  BumpPtrAllocator A;
  StringSaver Saver(A);
  ExpandResponseFiles(Saver,
         Triple(sys::getProcessTriple()).isOSWindows() ?
         cl::TokenizeWindowsCommandLine : cl::TokenizeGNUCommandLine,
         newArgv);
  argv = &newArgv[0];
  argc = static_cast<int>(newArgv.size());

  // Copy the program name into ProgName, making sure not to overflow it.
  ProgramName = sys::path::filename(StringRef(argv[0]));

  ProgramOverview = Overview;
  bool IgnoreErrors = Errs;
  if (!Errs)
    Errs = &errs();
  bool ErrorParsing = false;

  // Check out the positional arguments to collect information about them.
  unsigned NumPositionalRequired = 0;

  // Determine whether or not there are an unlimited number of positionals
  bool HasUnlimitedPositionals = false;

  int FirstArg = 1;
  SubCommand *ChosenSubCommand = &*TopLevelSubCommand;
  if (argc >= 2 && argv[FirstArg][0] != '-') {
    // If the first argument specifies a valid subcommand, start processing
    // options from the second argument.
    ChosenSubCommand = LookupSubCommand(StringRef(argv[FirstArg]));
    if (ChosenSubCommand != &*TopLevelSubCommand)
      FirstArg = 2;
  }
  GlobalParser->ActiveSubCommand = ChosenSubCommand;

  assert(ChosenSubCommand);
  auto &ConsumeAfterOpt = ChosenSubCommand->ConsumeAfterOpt;
  auto &PositionalOpts = ChosenSubCommand->PositionalOpts;
  auto &SinkOpts = ChosenSubCommand->SinkOpts;
  auto &OptionsMap = ChosenSubCommand->OptionsMap;

  for (auto O: DefaultOptions) {
    addOption(O, true);
  }

  if (ConsumeAfterOpt) {
    assert(PositionalOpts.size() > 0 &&
           "Cannot specify cl::ConsumeAfter without a positional argument!");
  }
  if (!PositionalOpts.empty()) {

    // Calculate how many positional values are _required_.
    bool UnboundedFound = false;
    for (size_t i = 0, e = PositionalOpts.size(); i != e; ++i) {
      Option *Opt = PositionalOpts[i];
      if (RequiresValue(Opt))
        ++NumPositionalRequired;
      else if (ConsumeAfterOpt) {
        // ConsumeAfter cannot be combined with "optional" positional options
        // unless there is only one positional argument...
        if (PositionalOpts.size() > 1) {
          if (!IgnoreErrors)
            Opt->error("error - this positional option will never be matched, "
                       "because it does not Require a value, and a "
                       "cl::ConsumeAfter option is active!");
          ErrorParsing = true;
        }
      } else if (UnboundedFound && !Opt->hasArgStr()) {
        // This option does not "require" a value...  Make sure this option is
        // not specified after an option that eats all extra arguments, or this
        // one will never get any!
        //
        if (!IgnoreErrors)
          Opt->error("error - option can never match, because "
                     "another positional argument will match an "
                     "unbounded number of values, and this option"
                     " does not require a value!");
        *Errs << ProgramName << ": CommandLine Error: Option '" << Opt->ArgStr
              << "' is all messed up!\n";
        *Errs << PositionalOpts.size();
        ErrorParsing = true;
      }
      UnboundedFound |= EatsUnboundedNumberOfValues(Opt);
    }
    HasUnlimitedPositionals = UnboundedFound || ConsumeAfterOpt;
  }

  // PositionalVals - A vector of "positional" arguments we accumulate into
  // the process at the end.
  //
  SmallVector<std::pair<StringRef, unsigned>, 4> PositionalVals;

  // If the program has named positional arguments, and the name has been run
  // across, keep track of which positional argument was named.  Otherwise put
  // the positional args into the PositionalVals list...
  Option *ActivePositionalArg = nullptr;

  // Loop over all of the arguments... processing them.
  bool DashDashFound = false; // Have we read '--'?
  for (int i = FirstArg; i < argc; ++i) {
    Option *Handler = nullptr;
    Option *NearestHandler = nullptr;
    std::string NearestHandlerString;
    StringRef Value;
    StringRef ArgName = "";
    bool HaveDoubleDash = false;

    // Check to see if this is a positional argument.  This argument is
    // considered to be positional if it doesn't start with '-', if it is "-"
    // itself, or if we have seen "--" already.
    //
    if (argv[i][0] != '-' || argv[i][1] == 0 || DashDashFound) {
      // Positional argument!
      if (ActivePositionalArg) {
        ProvidePositionalOption(ActivePositionalArg, StringRef(argv[i]), i);
        continue; // We are done!
      }

      if (!PositionalOpts.empty()) {
        PositionalVals.push_back(std::make_pair(StringRef(argv[i]), i));

        // All of the positional arguments have been fulfulled, give the rest to
        // the consume after option... if it's specified...
        //
        if (PositionalVals.size() >= NumPositionalRequired && ConsumeAfterOpt) {
          for (++i; i < argc; ++i)
            PositionalVals.push_back(std::make_pair(StringRef(argv[i]), i));
          break; // Handle outside of the argument processing loop...
        }

        // Delay processing positional arguments until the end...
        continue;
      }
    } else if (argv[i][0] == '-' && argv[i][1] == '-' && argv[i][2] == 0 &&
               !DashDashFound) {
      DashDashFound = true; // This is the mythical "--"?
      continue;             // Don't try to process it as an argument itself.
    } else if (ActivePositionalArg &&
               (ActivePositionalArg->getMiscFlags() & PositionalEatsArgs)) {
      // If there is a positional argument eating options, check to see if this
      // option is another positional argument.  If so, treat it as an argument,
      // otherwise feed it to the eating positional.
      ArgName = StringRef(argv[i] + 1);
      // Eat second dash.
      if (!ArgName.empty() && ArgName[0] == '-') {
        HaveDoubleDash = true;
        ArgName = ArgName.substr(1);
      }

      Handler = LookupLongOption(*ChosenSubCommand, ArgName, Value,
                                 LongOptionsUseDoubleDash, HaveDoubleDash);
      if (!Handler || Handler->getFormattingFlag() != cl::Positional) {
        ProvidePositionalOption(ActivePositionalArg, StringRef(argv[i]), i);
        continue; // We are done!
      }
    } else { // We start with a '-', must be an argument.
      ArgName = StringRef(argv[i] + 1);
      // Eat second dash.
      if (!ArgName.empty() && ArgName[0] == '-') {
        HaveDoubleDash = true;
        ArgName = ArgName.substr(1);
      }

      Handler = LookupLongOption(*ChosenSubCommand, ArgName, Value,
                                 LongOptionsUseDoubleDash, HaveDoubleDash);

      // Check to see if this "option" is really a prefixed or grouped argument.
      if (!Handler && !(LongOptionsUseDoubleDash && HaveDoubleDash))
        Handler = HandlePrefixedOrGroupedOption(ArgName, Value, ErrorParsing,
                                                OptionsMap);

      // Otherwise, look for the closest available option to report to the user
      // in the upcoming error.
      if (!Handler && SinkOpts.empty())
        NearestHandler =
            LookupNearestOption(ArgName, OptionsMap, NearestHandlerString);
    }

    if (!Handler) {
      if (SinkOpts.empty()) {
        *Errs << ProgramName << ": Unknown command line argument '" << argv[i]
              << "'.  Try: '" << argv[0] << " --help'\n";

        if (NearestHandler) {
          // If we know a near match, report it as well.
          *Errs << ProgramName << ": Did you mean '"
                << PrintArg(NearestHandlerString) << "'?\n";
        }

        ErrorParsing = true;
      } else {
        for (SmallVectorImpl<Option *>::iterator I = SinkOpts.begin(),
                                                 E = SinkOpts.end();
             I != E; ++I)
          (*I)->addOccurrence(i, "", StringRef(argv[i]));
      }
      continue;
    }

    // If this is a named positional argument, just remember that it is the
    // active one...
    if (Handler->getFormattingFlag() == cl::Positional) {
      if ((Handler->getMiscFlags() & PositionalEatsArgs) && !Value.empty()) {
        Handler->error("This argument does not take a value.\n"
                       "\tInstead, it consumes any positional arguments until "
                       "the next recognized option.", *Errs);
        ErrorParsing = true;
      }
      ActivePositionalArg = Handler;
    }
    else
      ErrorParsing |= ProvideOption(Handler, ArgName, Value, argc, argv, i);
  }

  // Check and handle positional arguments now...
  if (NumPositionalRequired > PositionalVals.size()) {
      *Errs << ProgramName
             << ": Not enough positional command line arguments specified!\n"
             << "Must specify at least " << NumPositionalRequired
             << " positional argument" << (NumPositionalRequired > 1 ? "s" : "")
             << ": See: " << argv[0] << " --help\n";

    ErrorParsing = true;
  } else if (!HasUnlimitedPositionals &&
             PositionalVals.size() > PositionalOpts.size()) {
    *Errs << ProgramName << ": Too many positional arguments specified!\n"
          << "Can specify at most " << PositionalOpts.size()
          << " positional arguments: See: " << argv[0] << " --help\n";
    ErrorParsing = true;

  } else if (!ConsumeAfterOpt) {
    // Positional args have already been handled if ConsumeAfter is specified.
    unsigned ValNo = 0, NumVals = static_cast<unsigned>(PositionalVals.size());
    for (size_t i = 0, e = PositionalOpts.size(); i != e; ++i) {
      if (RequiresValue(PositionalOpts[i])) {
        ProvidePositionalOption(PositionalOpts[i], PositionalVals[ValNo].first,
                                PositionalVals[ValNo].second);
        ValNo++;
        --NumPositionalRequired; // We fulfilled our duty...
      }

      // If we _can_ give this option more arguments, do so now, as long as we
      // do not give it values that others need.  'Done' controls whether the
      // option even _WANTS_ any more.
      //
      bool Done = PositionalOpts[i]->getNumOccurrencesFlag() == cl::Required;
      while (NumVals - ValNo > NumPositionalRequired && !Done) {
        switch (PositionalOpts[i]->getNumOccurrencesFlag()) {
        case cl::Optional:
          Done = true; // Optional arguments want _at most_ one value
          LLVM_FALLTHROUGH;
        case cl::ZeroOrMore: // Zero or more will take all they can get...
        case cl::OneOrMore:  // One or more will take all they can get...
          ProvidePositionalOption(PositionalOpts[i],
                                  PositionalVals[ValNo].first,
                                  PositionalVals[ValNo].second);
          ValNo++;
          break;
        default:
          llvm_unreachable("Internal error, unexpected NumOccurrences flag in "
                           "positional argument processing!");
        }
      }
    }
  } else {
    assert(ConsumeAfterOpt && NumPositionalRequired <= PositionalVals.size());
    unsigned ValNo = 0;
    for (size_t j = 1, e = PositionalOpts.size(); j != e; ++j)
      if (RequiresValue(PositionalOpts[j])) {
        ErrorParsing |= ProvidePositionalOption(PositionalOpts[j],
                                                PositionalVals[ValNo].first,
                                                PositionalVals[ValNo].second);
        ValNo++;
      }

    // Handle the case where there is just one positional option, and it's
    // optional.  In this case, we want to give JUST THE FIRST option to the
    // positional option and keep the rest for the consume after.  The above
    // loop would have assigned no values to positional options in this case.
    //
    if (PositionalOpts.size() == 1 && ValNo == 0 && !PositionalVals.empty()) {
      ErrorParsing |= ProvidePositionalOption(PositionalOpts[0],
                                              PositionalVals[ValNo].first,
                                              PositionalVals[ValNo].second);
      ValNo++;
    }

    // Handle over all of the rest of the arguments to the
    // cl::ConsumeAfter command line option...
    for (; ValNo != PositionalVals.size(); ++ValNo)
      ErrorParsing |=
          ProvidePositionalOption(ConsumeAfterOpt, PositionalVals[ValNo].first,
                                  PositionalVals[ValNo].second);
  }

  // Loop over args and make sure all required args are specified!
  for (const auto &Opt : OptionsMap) {
    switch (Opt.second->getNumOccurrencesFlag()) {
    case Required:
    case OneOrMore:
      if (Opt.second->getNumOccurrences() == 0) {
        Opt.second->error("must be specified at least once!");
        ErrorParsing = true;
      }
      LLVM_FALLTHROUGH;
    default:
      break;
    }
  }

  // Now that we know if -debug is specified, we can use it.
  // Note that if ReadResponseFiles == true, this must be done before the
  // memory allocated for the expanded command line is free()d below.
  LLVM_DEBUG(dbgs() << "Args: ";
             for (int i = 0; i < argc; ++i) dbgs() << argv[i] << ' ';
             dbgs() << '\n';);

  // Free all of the memory allocated to the map.  Command line options may only
  // be processed once!
  MoreHelp.clear();

  // If we had an error processing our arguments, don't let the program execute
  if (ErrorParsing) {
    if (!IgnoreErrors)
      exit(1);
    return false;
  }
  return true;
}

//===----------------------------------------------------------------------===//
// Option Base class implementation
//

bool Option::error(const Twine &Message, StringRef ArgName, raw_ostream &Errs) {
  if (!ArgName.data())
    ArgName = ArgStr;
  if (ArgName.empty())
    Errs << HelpStr; // Be nice for positional arguments
  else
    Errs << GlobalParser->ProgramName << ": for the " << PrintArg(ArgName);

  Errs << " option: " << Message << "\n";
  return true;
}

bool Option::addOccurrence(unsigned pos, StringRef ArgName, StringRef Value,
                           bool MultiArg) {
  if (!MultiArg)
    NumOccurrences++; // Increment the number of times we have been seen

  switch (getNumOccurrencesFlag()) {
  case Optional:
    if (NumOccurrences > 1)
      return error("may only occur zero or one times!", ArgName);
    break;
  case Required:
    if (NumOccurrences > 1)
      return error("must occur exactly one time!", ArgName);
    LLVM_FALLTHROUGH;
  case OneOrMore:
  case ZeroOrMore:
  case ConsumeAfter:
    break;
  }

  return handleOccurrence(pos, ArgName, Value);
}

// getValueStr - Get the value description string, using "DefaultMsg" if nothing
// has been specified yet.
//
static StringRef getValueStr(const Option &O, StringRef DefaultMsg) {
  if (O.ValueStr.empty())
    return DefaultMsg;
  return O.ValueStr;
}

//===----------------------------------------------------------------------===//
// cl::alias class implementation
//

// Return the width of the option tag for printing...
size_t alias::getOptionWidth() const {
  return argPlusPrefixesSize(ArgStr);
}

void Option::printHelpStr(StringRef HelpStr, size_t Indent,
                          size_t FirstLineIndentedBy) {
  assert(Indent >= FirstLineIndentedBy);
  std::pair<StringRef, StringRef> Split = HelpStr.split('\n');
  outs().indent(Indent - FirstLineIndentedBy)
      << ArgHelpPrefix << Split.first << "\n";
  while (!Split.second.empty()) {
    Split = Split.second.split('\n');
    outs().indent(Indent) << Split.first << "\n";
  }
}

// Print out the option for the alias.
void alias::printOptionInfo(size_t GlobalWidth) const {
  outs() << PrintArg(ArgStr);
  printHelpStr(HelpStr, GlobalWidth, argPlusPrefixesSize(ArgStr));
}

//===----------------------------------------------------------------------===//
// Parser Implementation code...
//

// basic_parser implementation
//

// Return the width of the option tag for printing...
size_t basic_parser_impl::getOptionWidth(const Option &O) const {
  size_t Len = argPlusPrefixesSize(O.ArgStr);
  auto ValName = getValueName();
  if (!ValName.empty()) {
    size_t FormattingLen = 3;
    if (O.getMiscFlags() & PositionalEatsArgs)
      FormattingLen = 6;
    Len += getValueStr(O, ValName).size() + FormattingLen;
  }

  return Len;
}

// printOptionInfo - Print out information about this option.  The
// to-be-maintained width is specified.
//
void basic_parser_impl::printOptionInfo(const Option &O,
                                        size_t GlobalWidth) const {
  outs() << PrintArg(O.ArgStr);

  auto ValName = getValueName();
  if (!ValName.empty()) {
    if (O.getMiscFlags() & PositionalEatsArgs) {
      outs() << " <" << getValueStr(O, ValName) << ">...";
    } else {
      outs() << "=<" << getValueStr(O, ValName) << '>';
    }
  }

  Option::printHelpStr(O.HelpStr, GlobalWidth, getOptionWidth(O));
}

void basic_parser_impl::printOptionName(const Option &O,
                                        size_t GlobalWidth) const {
  outs() << PrintArg(O.ArgStr);
  outs().indent(GlobalWidth - O.ArgStr.size());
}

// parser<bool> implementation
//
bool parser<bool>::parse(Option &O, StringRef ArgName, StringRef Arg,
                         bool &Value) {
  if (Arg == "" || Arg == "true" || Arg == "TRUE" || Arg == "True" ||
      Arg == "1") {
    Value = true;
    return false;
  }

  if (Arg == "false" || Arg == "FALSE" || Arg == "False" || Arg == "0") {
    Value = false;
    return false;
  }
  return O.error("'" + Arg +
                 "' is invalid value for boolean argument! Try 0 or 1");
}

// parser<boolOrDefault> implementation
//
bool parser<boolOrDefault>::parse(Option &O, StringRef ArgName, StringRef Arg,
                                  boolOrDefault &Value) {
  if (Arg == "" || Arg == "true" || Arg == "TRUE" || Arg == "True" ||
      Arg == "1") {
    Value = BOU_TRUE;
    return false;
  }
  if (Arg == "false" || Arg == "FALSE" || Arg == "False" || Arg == "0") {
    Value = BOU_FALSE;
    return false;
  }

  return O.error("'" + Arg +
                 "' is invalid value for boolean argument! Try 0 or 1");
}

// parser<int> implementation
//
bool parser<int>::parse(Option &O, StringRef ArgName, StringRef Arg,
                        int &Value) {
  if (Arg.getAsInteger(0, Value))
    return O.error("'" + Arg + "' value invalid for integer argument!");
  return false;
}

// parser<unsigned> implementation
//
bool parser<unsigned>::parse(Option &O, StringRef ArgName, StringRef Arg,
                             unsigned &Value) {

  if (Arg.getAsInteger(0, Value))
    return O.error("'" + Arg + "' value invalid for uint argument!");
  return false;
}

// parser<unsigned long> implementation
//
bool parser<unsigned long>::parse(Option &O, StringRef ArgName, StringRef Arg,
                                  unsigned long &Value) {

  if (Arg.getAsInteger(0, Value))
    return O.error("'" + Arg + "' value invalid for ulong argument!");
  return false;
}

// parser<unsigned long long> implementation
//
bool parser<unsigned long long>::parse(Option &O, StringRef ArgName,
                                       StringRef Arg,
                                       unsigned long long &Value) {

  if (Arg.getAsInteger(0, Value))
    return O.error("'" + Arg + "' value invalid for ullong argument!");
  return false;
}

// parser<double>/parser<float> implementation
//
static bool parseDouble(Option &O, StringRef Arg, double &Value) {
  if (to_float(Arg, Value))
    return false;
  return O.error("'" + Arg + "' value invalid for floating point argument!");
}

bool parser<double>::parse(Option &O, StringRef ArgName, StringRef Arg,
                           double &Val) {
  return parseDouble(O, Arg, Val);
}

bool parser<float>::parse(Option &O, StringRef ArgName, StringRef Arg,
                          float &Val) {
  double dVal;
  if (parseDouble(O, Arg, dVal))
    return true;
  Val = (float)dVal;
  return false;
}

// generic_parser_base implementation
//

// findOption - Return the option number corresponding to the specified
// argument string.  If the option is not found, getNumOptions() is returned.
//
unsigned generic_parser_base::findOption(StringRef Name) {
  unsigned e = getNumOptions();

  for (unsigned i = 0; i != e; ++i) {
    if (getOption(i) == Name)
      return i;
  }
  return e;
}

static StringRef EqValue = "=<value>";
static StringRef EmptyOption = "<empty>";
static StringRef OptionPrefix = "    =";
static size_t OptionPrefixesSize = OptionPrefix.size() + ArgHelpPrefix.size();

static bool shouldPrintOption(StringRef Name, StringRef Description,
                              const Option &O) {
  return O.getValueExpectedFlag() != ValueOptional || !Name.empty() ||
         !Description.empty();
}

// Return the width of the option tag for printing...
size_t generic_parser_base::getOptionWidth(const Option &O) const {
  if (O.hasArgStr()) {
    size_t Size =
        argPlusPrefixesSize(O.ArgStr) + EqValue.size();
    for (unsigned i = 0, e = getNumOptions(); i != e; ++i) {
      StringRef Name = getOption(i);
      if (!shouldPrintOption(Name, getDescription(i), O))
        continue;
      size_t NameSize = Name.empty() ? EmptyOption.size() : Name.size();
      Size = std::max(Size, NameSize + OptionPrefixesSize);
    }
    return Size;
  } else {
    size_t BaseSize = 0;
    for (unsigned i = 0, e = getNumOptions(); i != e; ++i)
      BaseSize = std::max(BaseSize, getOption(i).size() + 8);
    return BaseSize;
  }
}

// printOptionInfo - Print out information about this option.  The
// to-be-maintained width is specified.
//
void generic_parser_base::printOptionInfo(const Option &O,
                                          size_t GlobalWidth) const {
  if (O.hasArgStr()) {
    // When the value is optional, first print a line just describing the
    // option without values.
    if (O.getValueExpectedFlag() == ValueOptional) {
      for (unsigned i = 0, e = getNumOptions(); i != e; ++i) {
        if (getOption(i).empty()) {
          outs() << PrintArg(O.ArgStr);
          Option::printHelpStr(O.HelpStr, GlobalWidth,
                               argPlusPrefixesSize(O.ArgStr));
          break;
        }
      }
    }

    outs() << PrintArg(O.ArgStr) << EqValue;
    Option::printHelpStr(O.HelpStr, GlobalWidth,
                         EqValue.size() +
                             argPlusPrefixesSize(O.ArgStr));
    for (unsigned i = 0, e = getNumOptions(); i != e; ++i) {
      StringRef OptionName = getOption(i);
      StringRef Description = getDescription(i);
      if (!shouldPrintOption(OptionName, Description, O))
        continue;
      assert(GlobalWidth >= OptionName.size() + OptionPrefixesSize);
      size_t NumSpaces = GlobalWidth - OptionName.size() - OptionPrefixesSize;
      outs() << OptionPrefix << OptionName;
      if (OptionName.empty()) {
        outs() << EmptyOption;
        assert(NumSpaces >= EmptyOption.size());
        NumSpaces -= EmptyOption.size();
      }
      if (!Description.empty())
        outs().indent(NumSpaces) << ArgHelpPrefix << "  " << Description;
      outs() << '\n';
    }
  } else {
    if (!O.HelpStr.empty())
      outs() << "  " << O.HelpStr << '\n';
    for (unsigned i = 0, e = getNumOptions(); i != e; ++i) {
      StringRef Option = getOption(i);
      outs() << "    " << PrintArg(Option);
      Option::printHelpStr(getDescription(i), GlobalWidth, Option.size() + 8);
    }
  }
}

static const size_t MaxOptWidth = 8; // arbitrary spacing for printOptionDiff

// printGenericOptionDiff - Print the value of this option and it's default.
//
// "Generic" options have each value mapped to a name.
void generic_parser_base::printGenericOptionDiff(
    const Option &O, const GenericOptionValue &Value,
    const GenericOptionValue &Default, size_t GlobalWidth) const {
  outs() << "  " << PrintArg(O.ArgStr);
  outs().indent(GlobalWidth - O.ArgStr.size());

  unsigned NumOpts = getNumOptions();
  for (unsigned i = 0; i != NumOpts; ++i) {
    if (Value.compare(getOptionValue(i)))
      continue;

    outs() << "= " << getOption(i);
    size_t L = getOption(i).size();
    size_t NumSpaces = MaxOptWidth > L ? MaxOptWidth - L : 0;
    outs().indent(NumSpaces) << " (default: ";
    for (unsigned j = 0; j != NumOpts; ++j) {
      if (Default.compare(getOptionValue(j)))
        continue;
      outs() << getOption(j);
      break;
    }
    outs() << ")\n";
    return;
  }
  outs() << "= *unknown option value*\n";
}

// printOptionDiff - Specializations for printing basic value types.
//
#define PRINT_OPT_DIFF(T)                                                      \
  void parser<T>::printOptionDiff(const Option &O, T V, OptionValue<T> D,      \
                                  size_t GlobalWidth) const {                  \
    printOptionName(O, GlobalWidth);                                           \
    std::string Str;                                                           \
    {                                                                          \
      raw_string_ostream SS(Str);                                              \
      SS << V;                                                                 \
    }                                                                          \
    outs() << "= " << Str;                                                     \
    size_t NumSpaces =                                                         \
        MaxOptWidth > Str.size() ? MaxOptWidth - Str.size() : 0;               \
    outs().indent(NumSpaces) << " (default: ";                                 \
    if (D.hasValue())                                                          \
      outs() << D.getValue();                                                  \
    else                                                                       \
      outs() << "*no default*";                                                \
    outs() << ")\n";                                                           \
  }

PRINT_OPT_DIFF(bool)
PRINT_OPT_DIFF(boolOrDefault)
PRINT_OPT_DIFF(int)
PRINT_OPT_DIFF(unsigned)
PRINT_OPT_DIFF(unsigned long)
PRINT_OPT_DIFF(unsigned long long)
PRINT_OPT_DIFF(double)
PRINT_OPT_DIFF(float)
PRINT_OPT_DIFF(char)

void parser<std::string>::printOptionDiff(const Option &O, StringRef V,
                                          const OptionValue<std::string> &D,
                                          size_t GlobalWidth) const {
  printOptionName(O, GlobalWidth);
  outs() << "= " << V;
  size_t NumSpaces = MaxOptWidth > V.size() ? MaxOptWidth - V.size() : 0;
  outs().indent(NumSpaces) << " (default: ";
  if (D.hasValue())
    outs() << D.getValue();
  else
    outs() << "*no default*";
  outs() << ")\n";
}

// Print a placeholder for options that don't yet support printOptionDiff().
void basic_parser_impl::printOptionNoValue(const Option &O,
                                           size_t GlobalWidth) const {
  printOptionName(O, GlobalWidth);
  outs() << "= *cannot print option value*\n";
}

//===----------------------------------------------------------------------===//
// -help and -help-hidden option implementation
//

static int OptNameCompare(const std::pair<const char *, Option *> *LHS,
                          const std::pair<const char *, Option *> *RHS) {
  return strcmp(LHS->first, RHS->first);
}

static int SubNameCompare(const std::pair<const char *, SubCommand *> *LHS,
                          const std::pair<const char *, SubCommand *> *RHS) {
  return strcmp(LHS->first, RHS->first);
}

// Copy Options into a vector so we can sort them as we like.
static void sortOpts(StringMap<Option *> &OptMap,
                     SmallVectorImpl<std::pair<const char *, Option *>> &Opts,
                     bool ShowHidden) {
  SmallPtrSet<Option *, 32> OptionSet; // Duplicate option detection.

  for (StringMap<Option *>::iterator I = OptMap.begin(), E = OptMap.end();
       I != E; ++I) {
    // Ignore really-hidden options.
    if (I->second->getOptionHiddenFlag() == ReallyHidden)
      continue;

    // Unless showhidden is set, ignore hidden flags.
    if (I->second->getOptionHiddenFlag() == Hidden && !ShowHidden)
      continue;

    // If we've already seen this option, don't add it to the list again.
    if (!OptionSet.insert(I->second).second)
      continue;

    Opts.push_back(
        std::pair<const char *, Option *>(I->getKey().data(), I->second));
  }

  // Sort the options list alphabetically.
  array_pod_sort(Opts.begin(), Opts.end(), OptNameCompare);
}

static void
sortSubCommands(const SmallPtrSetImpl<SubCommand *> &SubMap,
                SmallVectorImpl<std::pair<const char *, SubCommand *>> &Subs) {
  for (const auto &S : SubMap) {
    if (S->getName().empty())
      continue;
    Subs.push_back(std::make_pair(S->getName().data(), S));
  }
  array_pod_sort(Subs.begin(), Subs.end(), SubNameCompare);
}

namespace {

class HelpPrinter {
protected:
  const bool ShowHidden;
  typedef SmallVector<std::pair<const char *, Option *>, 128>
      StrOptionPairVector;
  typedef SmallVector<std::pair<const char *, SubCommand *>, 128>
      StrSubCommandPairVector;
  // Print the options. Opts is assumed to be alphabetically sorted.
  virtual void printOptions(StrOptionPairVector &Opts, size_t MaxArgLen) {
    for (size_t i = 0, e = Opts.size(); i != e; ++i)
      Opts[i].second->printOptionInfo(MaxArgLen);
  }

  void printSubCommands(StrSubCommandPairVector &Subs, size_t MaxSubLen) {
    for (const auto &S : Subs) {
      outs() << "  " << S.first;
      if (!S.second->getDescription().empty()) {
        outs().indent(MaxSubLen - strlen(S.first));
        outs() << " - " << S.second->getDescription();
      }
      outs() << "\n";
    }
  }

public:
  explicit HelpPrinter(bool showHidden) : ShowHidden(showHidden) {}
  virtual ~HelpPrinter() {}

  // Invoke the printer.
  void operator=(bool Value) {
    if (!Value)
      return;
    printHelp();

    // Halt the program since help information was printed
    exit(0);
  }

  void printHelp() {
    SubCommand *Sub = GlobalParser->getActiveSubCommand();
    auto &OptionsMap = Sub->OptionsMap;
    auto &PositionalOpts = Sub->PositionalOpts;
    auto &ConsumeAfterOpt = Sub->ConsumeAfterOpt;

    StrOptionPairVector Opts;
    sortOpts(OptionsMap, Opts, ShowHidden);

    StrSubCommandPairVector Subs;
    sortSubCommands(GlobalParser->RegisteredSubCommands, Subs);

    if (!GlobalParser->ProgramOverview.empty())
      outs() << "OVERVIEW: " << GlobalParser->ProgramOverview << "\n";

    if (Sub == &*TopLevelSubCommand) {
      outs() << "USAGE: " << GlobalParser->ProgramName;
      if (Subs.size() > 2)
        outs() << " [subcommand]";
      outs() << " [options]";
    } else {
      if (!Sub->getDescription().empty()) {
        outs() << "SUBCOMMAND '" << Sub->getName()
               << "': " << Sub->getDescription() << "\n\n";
      }
      outs() << "USAGE: " << GlobalParser->ProgramName << " " << Sub->getName()
             << " [options]";
    }

    for (auto Opt : PositionalOpts) {
      if (Opt->hasArgStr())
        outs() << " --" << Opt->ArgStr;
      outs() << " " << Opt->HelpStr;
    }

    // Print the consume after option info if it exists...
    if (ConsumeAfterOpt)
      outs() << " " << ConsumeAfterOpt->HelpStr;

    if (Sub == &*TopLevelSubCommand && !Subs.empty()) {
      // Compute the maximum subcommand length...
      size_t MaxSubLen = 0;
      for (size_t i = 0, e = Subs.size(); i != e; ++i)
        MaxSubLen = std::max(MaxSubLen, strlen(Subs[i].first));

      outs() << "\n\n";
      outs() << "SUBCOMMANDS:\n\n";
      printSubCommands(Subs, MaxSubLen);
      outs() << "\n";
      outs() << "  Type \"" << GlobalParser->ProgramName
             << " <subcommand> --help\" to get more help on a specific "
                "subcommand";
    }

    outs() << "\n\n";

    // Compute the maximum argument length...
    size_t MaxArgLen = 0;
    for (size_t i = 0, e = Opts.size(); i != e; ++i)
      MaxArgLen = std::max(MaxArgLen, Opts[i].second->getOptionWidth());

    outs() << "OPTIONS:\n";
    printOptions(Opts, MaxArgLen);

    // Print any extra help the user has declared.
    for (auto I : GlobalParser->MoreHelp)
      outs() << I;
    GlobalParser->MoreHelp.clear();
  }
};

class CategorizedHelpPrinter : public HelpPrinter {
public:
  explicit CategorizedHelpPrinter(bool showHidden) : HelpPrinter(showHidden) {}

  // Helper function for printOptions().
  // It shall return a negative value if A's name should be lexicographically
  // ordered before B's name. It returns a value greater than zero if B's name
  // should be ordered before A's name, and it returns 0 otherwise.
  static int OptionCategoryCompare(OptionCategory *const *A,
                                   OptionCategory *const *B) {
    return (*A)->getName().compare((*B)->getName());
  }

  // Make sure we inherit our base class's operator=()
  using HelpPrinter::operator=;

protected:
  void printOptions(StrOptionPairVector &Opts, size_t MaxArgLen) override {
    std::vector<OptionCategory *> SortedCategories;
    std::map<OptionCategory *, std::vector<Option *>> CategorizedOptions;

    // Collect registered option categories into vector in preparation for
    // sorting.
    for (auto I = GlobalParser->RegisteredOptionCategories.begin(),
              E = GlobalParser->RegisteredOptionCategories.end();
         I != E; ++I) {
      SortedCategories.push_back(*I);
    }

    // Sort the different option categories alphabetically.
    assert(SortedCategories.size() > 0 && "No option categories registered!");
    array_pod_sort(SortedCategories.begin(), SortedCategories.end(),
                   OptionCategoryCompare);

    // Create map to empty vectors.
    for (std::vector<OptionCategory *>::const_iterator
             I = SortedCategories.begin(),
             E = SortedCategories.end();
         I != E; ++I)
      CategorizedOptions[*I] = std::vector<Option *>();

    // Walk through pre-sorted options and assign into categories.
    // Because the options are already alphabetically sorted the
    // options within categories will also be alphabetically sorted.
    for (size_t I = 0, E = Opts.size(); I != E; ++I) {
      Option *Opt = Opts[I].second;
      for (auto &Cat : Opt->Categories) {
        assert(CategorizedOptions.count(Cat) > 0 &&
               "Option has an unregistered category");
        CategorizedOptions[Cat].push_back(Opt);
      }
    }

    // Now do printing.
    for (std::vector<OptionCategory *>::const_iterator
             Category = SortedCategories.begin(),
             E = SortedCategories.end();
         Category != E; ++Category) {
      // Hide empty categories for --help, but show for --help-hidden.
      const auto &CategoryOptions = CategorizedOptions[*Category];
      bool IsEmptyCategory = CategoryOptions.empty();
      if (!ShowHidden && IsEmptyCategory)
        continue;

      // Print category information.
      outs() << "\n";
      outs() << (*Category)->getName() << ":\n";

      // Check if description is set.
      if (!(*Category)->getDescription().empty())
        outs() << (*Category)->getDescription() << "\n\n";
      else
        outs() << "\n";

      // When using --help-hidden explicitly state if the category has no
      // options associated with it.
      if (IsEmptyCategory) {
        outs() << "  This option category has no options.\n";
        continue;
      }
      // Loop over the options in the category and print.
      for (const Option *Opt : CategoryOptions)
        Opt->printOptionInfo(MaxArgLen);
    }
  }
};

// This wraps the Uncategorizing and Categorizing printers and decides
// at run time which should be invoked.
class HelpPrinterWrapper {
private:
  HelpPrinter &UncategorizedPrinter;
  CategorizedHelpPrinter &CategorizedPrinter;

public:
  explicit HelpPrinterWrapper(HelpPrinter &UncategorizedPrinter,
                              CategorizedHelpPrinter &CategorizedPrinter)
      : UncategorizedPrinter(UncategorizedPrinter),
        CategorizedPrinter(CategorizedPrinter) {}

  // Invoke the printer.
  void operator=(bool Value);
};

} // End anonymous namespace

// Declare the four HelpPrinter instances that are used to print out help, or
// help-hidden as an uncategorized list or in categories.
static HelpPrinter UncategorizedNormalPrinter(false);
static HelpPrinter UncategorizedHiddenPrinter(true);
static CategorizedHelpPrinter CategorizedNormalPrinter(false);
static CategorizedHelpPrinter CategorizedHiddenPrinter(true);

// Declare HelpPrinter wrappers that will decide whether or not to invoke
// a categorizing help printer
static HelpPrinterWrapper WrappedNormalPrinter(UncategorizedNormalPrinter,
                                               CategorizedNormalPrinter);
static HelpPrinterWrapper WrappedHiddenPrinter(UncategorizedHiddenPrinter,
                                               CategorizedHiddenPrinter);

// Define a category for generic options that all tools should have.
static cl::OptionCategory GenericCategory("Generic Options");

// Define uncategorized help printers.
// --help-list is hidden by default because if Option categories are being used
// then --help behaves the same as --help-list.
static cl::opt<HelpPrinter, true, parser<bool>> HLOp(
    "help-list",
    cl::desc("Display list of available options (--help-list-hidden for more)"),
    cl::location(UncategorizedNormalPrinter), cl::Hidden, cl::ValueDisallowed,
    cl::cat(GenericCategory), cl::sub(*AllSubCommands));

static cl::opt<HelpPrinter, true, parser<bool>>
    HLHOp("help-list-hidden", cl::desc("Display list of all available options"),
          cl::location(UncategorizedHiddenPrinter), cl::Hidden,
          cl::ValueDisallowed, cl::cat(GenericCategory),
          cl::sub(*AllSubCommands));

// Define uncategorized/categorized help printers. These printers change their
// behaviour at runtime depending on whether one or more Option categories have
// been declared.
static cl::opt<HelpPrinterWrapper, true, parser<bool>>
    HOp("help", cl::desc("Display available options (--help-hidden for more)"),
        cl::location(WrappedNormalPrinter), cl::ValueDisallowed,
        cl::cat(GenericCategory), cl::sub(*AllSubCommands));

static cl::alias HOpA("h", cl::desc("Alias for --help"), cl::aliasopt(HOp),
                      cl::DefaultOption);

static cl::opt<HelpPrinterWrapper, true, parser<bool>>
    HHOp("help-hidden", cl::desc("Display all available options"),
         cl::location(WrappedHiddenPrinter), cl::Hidden, cl::ValueDisallowed,
         cl::cat(GenericCategory), cl::sub(*AllSubCommands));

static cl::opt<bool> PrintOptions(
    "print-options",
    cl::desc("Print non-default options after command line parsing"),
    cl::Hidden, cl::init(false), cl::cat(GenericCategory),
    cl::sub(*AllSubCommands));

static cl::opt<bool> PrintAllOptions(
    "print-all-options",
    cl::desc("Print all option values after command line parsing"), cl::Hidden,
    cl::init(false), cl::cat(GenericCategory), cl::sub(*AllSubCommands));

void HelpPrinterWrapper::operator=(bool Value) {
  if (!Value)
    return;

  // Decide which printer to invoke. If more than one option category is
  // registered then it is useful to show the categorized help instead of
  // uncategorized help.
  if (GlobalParser->RegisteredOptionCategories.size() > 1) {
    // unhide --help-list option so user can have uncategorized output if they
    // want it.
    HLOp.setHiddenFlag(NotHidden);

    CategorizedPrinter = true; // Invoke categorized printer
  } else
    UncategorizedPrinter = true; // Invoke uncategorized printer
}

// Print the value of each option.
void cl::PrintOptionValues() { GlobalParser->printOptionValues(); }

void CommandLineParser::printOptionValues() {
  if (!PrintOptions && !PrintAllOptions)
    return;

  SmallVector<std::pair<const char *, Option *>, 128> Opts;
  sortOpts(ActiveSubCommand->OptionsMap, Opts, /*ShowHidden*/ true);

  // Compute the maximum argument length...
  size_t MaxArgLen = 0;
  for (size_t i = 0, e = Opts.size(); i != e; ++i)
    MaxArgLen = std::max(MaxArgLen, Opts[i].second->getOptionWidth());

  for (size_t i = 0, e = Opts.size(); i != e; ++i)
    Opts[i].second->printOptionValue(MaxArgLen, PrintAllOptions);
}

static VersionPrinterTy OverrideVersionPrinter = nullptr;

static std::vector<VersionPrinterTy> *ExtraVersionPrinters = nullptr;

namespace {
class VersionPrinter {
public:
  void print() {
    raw_ostream &OS = outs();
#ifdef PACKAGE_VENDOR
    OS << PACKAGE_VENDOR << " ";
#else
    OS << "LLVM (http://llvm.org/):\n  ";
#endif
    OS << PACKAGE_NAME << " version " << PACKAGE_VERSION;
#ifdef LLVM_VERSION_INFO
    OS << " " << LLVM_VERSION_INFO;
#endif
    OS << "\n  ";
#ifndef __OPTIMIZE__
    OS << "DEBUG build";
#else
    OS << "Optimized build";
#endif
#ifndef NDEBUG
    OS << " with assertions";
#endif
#if LLVM_VERSION_PRINTER_SHOW_HOST_TARGET_INFO
    std::string CPU = sys::getHostCPUName();
    if (CPU == "generic")
      CPU = "(unknown)";
    OS << ".\n"
       << "  Default target: " << sys::getDefaultTargetTriple() << '\n'
       << "  Host CPU: " << CPU;
#endif
    OS << '\n';
  }
  void operator=(bool OptionWasSpecified) {
    if (!OptionWasSpecified)
      return;

    if (OverrideVersionPrinter != nullptr) {
      OverrideVersionPrinter(outs());
      exit(0);
    }
    print();

    // Iterate over any registered extra printers and call them to add further
    // information.
    if (ExtraVersionPrinters != nullptr) {
      outs() << '\n';
      for (auto I : *ExtraVersionPrinters)
        I(outs());
    }

    exit(0);
  }
};
} // End anonymous namespace

// Define the --version option that prints out the LLVM version for the tool
static VersionPrinter VersionPrinterInstance;

static cl::opt<VersionPrinter, true, parser<bool>>
    VersOp("version", cl::desc("Display the version of this program"),
           cl::location(VersionPrinterInstance), cl::ValueDisallowed,
           cl::cat(GenericCategory));

// Utility function for printing the help message.
void cl::PrintHelpMessage(bool Hidden, bool Categorized) {
  if (!Hidden && !Categorized)
    UncategorizedNormalPrinter.printHelp();
  else if (!Hidden && Categorized)
    CategorizedNormalPrinter.printHelp();
  else if (Hidden && !Categorized)
    UncategorizedHiddenPrinter.printHelp();
  else
    CategorizedHiddenPrinter.printHelp();
}

/// Utility function for printing version number.
void cl::PrintVersionMessage() { VersionPrinterInstance.print(); }

void cl::SetVersionPrinter(VersionPrinterTy func) { OverrideVersionPrinter = func; }

void cl::AddExtraVersionPrinter(VersionPrinterTy func) {
  if (!ExtraVersionPrinters)
    ExtraVersionPrinters = new std::vector<VersionPrinterTy>;

  ExtraVersionPrinters->push_back(func);
}

StringMap<Option *> &cl::getRegisteredOptions(SubCommand &Sub) {
  auto &Subs = GlobalParser->RegisteredSubCommands;
  (void)Subs;
  assert(is_contained(Subs, &Sub));
  return Sub.OptionsMap;
}

iterator_range<typename SmallPtrSet<SubCommand *, 4>::iterator>
cl::getRegisteredSubcommands() {
  return GlobalParser->getRegisteredSubcommands();
}

void cl::HideUnrelatedOptions(cl::OptionCategory &Category, SubCommand &Sub) {
  for (auto &I : Sub.OptionsMap) {
    for (auto &Cat : I.second->Categories) {
      if (Cat != &Category &&
          Cat != &GenericCategory)
        I.second->setHiddenFlag(cl::ReallyHidden);
    }
  }
}

void cl::HideUnrelatedOptions(ArrayRef<const cl::OptionCategory *> Categories,
                              SubCommand &Sub) {
  for (auto &I : Sub.OptionsMap) {
    for (auto &Cat : I.second->Categories) {
      if (find(Categories, Cat) == Categories.end() && Cat != &GenericCategory)
        I.second->setHiddenFlag(cl::ReallyHidden);
    }
  }
}

void cl::ResetCommandLineParser() { GlobalParser->reset(); }
void cl::ResetAllOptionOccurrences() {
  GlobalParser->ResetAllOptionOccurrences();
}

void LLVMParseCommandLineOptions(int argc, const char *const *argv,
                                 const char *Overview) {
  llvm::cl::ParseCommandLineOptions(argc, argv, StringRef(Overview),
                                    &llvm::nulls());
}