gflags.cc

// Copyright (c) 1999, Google Inc.
// All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
//
//     * Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
//     * Redistributions in binary form must reproduce the above
// copyright notice, this list of conditions and the following disclaimer
// in the documentation and/or other materials provided with the
// distribution.
//     * Neither the name of Google Inc. nor the names of its
// contributors may be used to endorse or promote products derived from
// this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

// ---
// Revamped and reorganized by Craig Silverstein
//
// This file contains the implementation of all our command line flags
// stuff.  Here's how everything fits together
//
// * FlagRegistry owns CommandLineFlags owns FlagValue.
// * FlagSaver holds a FlagRegistry (saves it at construct time,
//     restores it at destroy time).
// * CommandLineFlagParser lives outside that hierarchy, but works on
//     CommandLineFlags (modifying the FlagValues).
// * Free functions like SetCommandLineOption() work via one of the
//     above (such as CommandLineFlagParser).
//
// In more detail:
//
// -- The main classes that hold flag data:
//
// FlagValue holds the current value of a flag.  It's
// pseudo-templatized: every operation on a FlagValue is typed.  It
// also deals with storage-lifetime issues (so flag values don't go
// away in a destructor), which is why we need a whole class to hold a
// variable's value.
//
// CommandLineFlag is all the information about a single command-line
// flag.  It has a FlagValue for the flag's current value, but also
// the flag's name, type, etc.
//
// FlagRegistry is a collection of CommandLineFlags.  There's the
// global registry, which is where flags defined via DEFINE_foo()
// live.  But it's possible to define your own flag, manually, in a
// different registry you create.  (In practice, multiple registries
// are used only by FlagSaver).
//
// A given FlagValue is owned by exactly one CommandLineFlag.  A given
// CommandLineFlag is owned by exactly one FlagRegistry.  FlagRegistry
// has a lock; any operation that writes to a FlagValue or
// CommandLineFlag owned by that registry must acquire the
// FlagRegistry lock before doing so.
//
// --- Some other classes and free functions:
//
// CommandLineFlagInfo is a client-exposed version of CommandLineFlag.
// Once it's instantiated, it has no dependencies or relationships
// with any other part of this file.
//
// FlagRegisterer is the helper class used by the DEFINE_* macros to
// allow work to be done at global initialization time.
//
// CommandLineFlagParser is the class that reads from the commandline
// and instantiates flag values based on that.  It needs to poke into
// the innards of the FlagValue->CommandLineFlag->FlagRegistry class
// hierarchy to do that.  It's careful to acquire the FlagRegistry
// lock before doing any writing or other non-const actions.
//
// GetCommandLineOption is just a hook into registry routines to
// retrieve a flag based on its name.  SetCommandLineOption, on the
// other hand, hooks into CommandLineFlagParser.  Other API functions
// are, similarly, mostly hooks into the functionality described above.

// This comes first to ensure we define __STDC_FORMAT_MACROS in time.
#include <config.h>
#if defined(HAVE_INTTYPES_H) && !defined(__STDC_FORMAT_MACROS)
# define __STDC_FORMAT_MACROS 1   // gcc requires this to get PRId64, etc.
#endif

#include <gflags/gflags.h>
#include <assert.h>
#include <ctype.h>
#include <errno.h>
#ifdef HAVE_FNMATCH_H
# include <fnmatch.h>
#endif
#include <stdarg.h> // For va_list and related operations
#include <stdio.h>
#include <string.h>

#include <algorithm>
#include <map>
#include <string>
#include <utility>     // for pair<>
#include <vector>
#include "mutex.h"
#include "util.h"

#ifndef PATH_SEPARATOR
#define PATH_SEPARATOR  '/'
#endif


// Special flags, type 1: the 'recursive' flags.  They set another flag's val.
DEFINE_string(flagfile, "",
              "load flags from file");
DEFINE_string(fromenv, "",
              "set flags from the environment"
              " [use 'export FLAGS_flag1=value']");
DEFINE_string(tryfromenv, "",
              "set flags from the environment if present");

// Special flags, type 2: the 'parsing' flags.  They modify how we parse.
DEFINE_string(undefok, "",
              "comma-separated list of flag names that it is okay to specify "
              "on the command line even if the program does not define a flag "
              "with that name.  IMPORTANT: flags in this list that have "
              "arguments MUST use the flag=value format");

_START_GOOGLE_NAMESPACE_

using std::map;
using std::pair;
using std::sort;
using std::string;
using std::vector;

// This is used by the unittest to test error-exit code
void GFLAGS_DLL_DECL (*gflags_exitfunc)(int) = &exit;  // from stdlib.h


// The help message indicating that the commandline flag has been
// 'stripped'. It will not show up when doing "-help" and its
// variants. The flag is stripped if STRIP_FLAG_HELP is set to 1
// before including base/gflags.h

// This is used by this file, and also in gflags_reporting.cc
const char kStrippedFlagHelp[] = "\001\002\003\004 (unknown) \004\003\002\001";

namespace {

// There are also 'reporting' flags, in gflags_reporting.cc.

static const char kError[] = "ERROR: ";

// Indicates that undefined options are to be ignored.
// Enables deferred processing of flags in dynamically loaded libraries.
static bool allow_command_line_reparsing = false;

static bool logging_is_probably_set_up = false;

// This is a 'prototype' validate-function.  'Real' validate
// functions, take a flag-value as an argument: ValidateFn(bool) or
// ValidateFn(uint64).  However, for easier storage, we strip off this
// argument and then restore it when actually calling the function on
// a flag value.
typedef bool (*ValidateFnProto)();

// Whether we should die when reporting an error.
enum DieWhenReporting { DIE, DO_NOT_DIE };

// Report Error and exit if requested.
static void ReportError(DieWhenReporting should_die, const char* format, ...) {
  char error_message[255];
  va_list ap;
  va_start(ap, format);
  vsnprintf(error_message, sizeof(error_message), format, ap);
  va_end(ap);
  fprintf(stderr, "%s", error_message);
  fflush(stderr);   // should be unnecessary, but cygwin's rxvt buffers stderr
  if (should_die == DIE) gflags_exitfunc(1);
}


// --------------------------------------------------------------------
// FlagValue
//    This represent the value a single flag might have.  The major
//    functionality is to convert from a string to an object of a
//    given type, and back.  Thread-compatible.
// --------------------------------------------------------------------

class CommandLineFlag;
class FlagValue {
 public:
  FlagValue(void* valbuf, const char* type, bool transfer_ownership_of_value);
  ~FlagValue();

  bool ParseFrom(const char* spec);
  string ToString() const;

 private:
  friend class CommandLineFlag;  // for many things, including Validate()
  friend class GOOGLE_NAMESPACE::FlagSaverImpl;  // calls New()
  friend class FlagRegistry;     // checks value_buffer_ for flags_by_ptr_ map
  template <typename T> friend T GetFromEnv(const char*, const char*, T);
  friend bool TryParseLocked(const CommandLineFlag*, FlagValue*,
                             const char*, string*);  // for New(), CopyFrom()

  enum ValueType {
    FV_BOOL = 0,
    FV_INT32 = 1,
    FV_INT64 = 2,
    FV_UINT64 = 3,
    FV_DOUBLE = 4,
    FV_STRING = 5,
    FV_MAX_INDEX = 5,
  };
  const char* TypeName() const;
  bool Equal(const FlagValue& x) const;
  FlagValue* New() const;   // creates a new one with default value
  void CopyFrom(const FlagValue& x);
  int ValueSize() const;

  // Calls the given validate-fn on value_buffer_, and returns
  // whatever it returns.  But first casts validate_fn_proto to a
  // function that takes our value as an argument (eg void
  // (*validate_fn)(bool) for a bool flag).
  bool Validate(const char* flagname, ValidateFnProto validate_fn_proto) const;

  void* value_buffer_;          // points to the buffer holding our data
  int8 type_;                   // how to interpret value_
  bool owns_value_;         // whether to free value on destruct

  FlagValue(const FlagValue&);   // no copying!
  void operator=(const FlagValue&);
};


// This could be a templated method of FlagValue, but doing so adds to the
// size of the .o.  Since there's no type-safety here anyway, macro is ok.
#define VALUE_AS(type)  *reinterpret_cast<type*>(value_buffer_)
#define OTHER_VALUE_AS(fv, type)  *reinterpret_cast<type*>(fv.value_buffer_)
#define SET_VALUE_AS(type, value)  VALUE_AS(type) = (value)

FlagValue::FlagValue(void* valbuf, const char* type,
                     bool transfer_ownership_of_value)
    : value_buffer_(valbuf),
      owns_value_(transfer_ownership_of_value) {
  for (type_ = 0; type_ <= FV_MAX_INDEX; ++type_) {
    if (!strcmp(type, TypeName())) {
      break;
    }
  }
  assert(type_ <= FV_MAX_INDEX);  // Unknown typename
}

FlagValue::~FlagValue() {
  if (!owns_value_) {
    return;
  }
  switch (type_) {
    case FV_BOOL: delete reinterpret_cast<bool*>(value_buffer_); break;
    case FV_INT32: delete reinterpret_cast<int32*>(value_buffer_); break;
    case FV_INT64: delete reinterpret_cast<int64*>(value_buffer_); break;
    case FV_UINT64: delete reinterpret_cast<uint64*>(value_buffer_); break;
    case FV_DOUBLE: delete reinterpret_cast<double*>(value_buffer_); break;
    case FV_STRING: delete reinterpret_cast<string*>(value_buffer_); break;
  }
}

bool FlagValue::ParseFrom(const char* value) {
  if (type_ == FV_BOOL) {
    const char* kTrue[] = { "1", "t", "true", "y", "yes" };
    const char* kFalse[] = { "0", "f", "false", "n", "no" };
    COMPILE_ASSERT(sizeof(kTrue) == sizeof(kFalse), true_false_equal);
    for (size_t i = 0; i < sizeof(kTrue)/sizeof(*kTrue); ++i) {
      if (strcasecmp(value, kTrue[i]) == 0) {
        SET_VALUE_AS(bool, true);
        return true;
      } else if (strcasecmp(value, kFalse[i]) == 0) {
        SET_VALUE_AS(bool, false);
        return true;
      }
    }
    return false;   // didn't match a legal input

  } else if (type_ == FV_STRING) {
    SET_VALUE_AS(string, value);
    return true;
  }

  // OK, it's likely to be numeric, and we'll be using a strtoXXX method.
  if (value[0] == '\0')   // empty-string is only allowed for string type.
    return false;
  char* end;
  // Leading 0x puts us in base 16.  But leading 0 does not put us in base 8!
  // It caused too many bugs when we had that behavior.
  int base = 10;    // by default
  if (value[0] == '0' && (value[1] == 'x' || value[1] == 'X'))
    base = 16;
  errno = 0;

  switch (type_) {
    case FV_INT32: {
      const int64 r = strto64(value, &end, base);
      if (errno || end != value + strlen(value))  return false;  // bad parse
      if (static_cast<int32>(r) != r)  // worked, but number out of range
        return false;
      SET_VALUE_AS(int32, static_cast<int32>(r));
      return true;
    }
    case FV_INT64: {
      const int64 r = strto64(value, &end, base);
      if (errno || end != value + strlen(value))  return false;  // bad parse
      SET_VALUE_AS(int64, r);
      return true;
    }
    case FV_UINT64: {
      while (*value == ' ') value++;
      if (*value == '-') return false;  // negative number
      const uint64 r = strtou64(value, &end, base);
      if (errno || end != value + strlen(value))  return false;  // bad parse
      SET_VALUE_AS(uint64, r);
      return true;
    }
    case FV_DOUBLE: {
      const double r = strtod(value, &end);
      if (errno || end != value + strlen(value))  return false;  // bad parse
      SET_VALUE_AS(double, r);
      return true;
    }
    default: {
      assert(false);  // unknown type
      return false;
    }
  }
}

string FlagValue::ToString() const {
  char intbuf[64];    // enough to hold even the biggest number
  switch (type_) {
    case FV_BOOL:
      return VALUE_AS(bool) ? "true" : "false";
    case FV_INT32:
      snprintf(intbuf, sizeof(intbuf), "%" PRId32, VALUE_AS(int32));
      return intbuf;
    case FV_INT64:
      snprintf(intbuf, sizeof(intbuf), "%" PRId64, VALUE_AS(int64));
      return intbuf;
    case FV_UINT64:
      snprintf(intbuf, sizeof(intbuf), "%" PRIu64, VALUE_AS(uint64));
      return intbuf;
    case FV_DOUBLE:
      snprintf(intbuf, sizeof(intbuf), "%.17g", VALUE_AS(double));
      return intbuf;
    case FV_STRING:
      return VALUE_AS(string);
    default:
      assert(false);
      return "";  // unknown type
  }
}

bool FlagValue::Validate(const char* flagname,
                         ValidateFnProto validate_fn_proto) const {
  switch (type_) {
    case FV_BOOL:
      return reinterpret_cast<bool (*)(const char*, bool)>(
          validate_fn_proto)(flagname, VALUE_AS(bool));
    case FV_INT32:
      return reinterpret_cast<bool (*)(const char*, int32)>(
          validate_fn_proto)(flagname, VALUE_AS(int32));
    case FV_INT64:
      return reinterpret_cast<bool (*)(const char*, int64)>(
          validate_fn_proto)(flagname, VALUE_AS(int64));
    case FV_UINT64:
      return reinterpret_cast<bool (*)(const char*, uint64)>(
          validate_fn_proto)(flagname, VALUE_AS(uint64));
    case FV_DOUBLE:
      return reinterpret_cast<bool (*)(const char*, double)>(
          validate_fn_proto)(flagname, VALUE_AS(double));
    case FV_STRING:
      return reinterpret_cast<bool (*)(const char*, const string&)>(
          validate_fn_proto)(flagname, VALUE_AS(string));
    default:
      assert(false);  // unknown type
      return false;
  }
}

const char* FlagValue::TypeName() const {
  static const char types[] =
      "bool\0xx"
      "int32\0x"
      "int64\0x"
      "uint64\0"
      "double\0"
      "string";
  if (type_ > FV_MAX_INDEX) {
    assert(false);
    return "";
  }
  // Directly indexing the strigns in the 'types' string, each of them
  // is 7 bytes long.
  return &types[type_ * 7];
}

bool FlagValue::Equal(const FlagValue& x) const {
  if (type_ != x.type_)
    return false;
  switch (type_) {
    case FV_BOOL:   return VALUE_AS(bool) == OTHER_VALUE_AS(x, bool);
    case FV_INT32:  return VALUE_AS(int32) == OTHER_VALUE_AS(x, int32);
    case FV_INT64:  return VALUE_AS(int64) == OTHER_VALUE_AS(x, int64);
    case FV_UINT64: return VALUE_AS(uint64) == OTHER_VALUE_AS(x, uint64);
    case FV_DOUBLE: return VALUE_AS(double) == OTHER_VALUE_AS(x, double);
    case FV_STRING: return VALUE_AS(string) == OTHER_VALUE_AS(x, string);
    default: assert(false); return false;  // unknown type
  }
}

FlagValue* FlagValue::New() const {
  const char *type = TypeName();
  switch (type_) {
    case FV_BOOL:   return new FlagValue(new bool(false), type, true);
    case FV_INT32:  return new FlagValue(new int32(0), type, true);
    case FV_INT64:  return new FlagValue(new int64(0), type, true);
    case FV_UINT64: return new FlagValue(new uint64(0), type, true);
    case FV_DOUBLE: return new FlagValue(new double(0.0), type, true);
    case FV_STRING: return new FlagValue(new string, type, true);
    default: assert(false); return NULL;  // unknown type
  }
}

void FlagValue::CopyFrom(const FlagValue& x) {
  assert(type_ == x.type_);
  switch (type_) {
    case FV_BOOL:   SET_VALUE_AS(bool, OTHER_VALUE_AS(x, bool));      break;
    case FV_INT32:  SET_VALUE_AS(int32, OTHER_VALUE_AS(x, int32));    break;
    case FV_INT64:  SET_VALUE_AS(int64, OTHER_VALUE_AS(x, int64));    break;
    case FV_UINT64: SET_VALUE_AS(uint64, OTHER_VALUE_AS(x, uint64));  break;
    case FV_DOUBLE: SET_VALUE_AS(double, OTHER_VALUE_AS(x, double));  break;
    case FV_STRING: SET_VALUE_AS(string, OTHER_VALUE_AS(x, string));  break;
    default: assert(false);  // unknown type
  }
}

int FlagValue::ValueSize() const {
  if (type_ > FV_MAX_INDEX) {
    assert(false);  // unknown type
    return 0;
  }
  static const uint8 valuesize[] = {
    sizeof(bool),
    sizeof(int32),
    sizeof(int64),
    sizeof(uint64),
    sizeof(double),
    sizeof(string),
  };
  return valuesize[type_];
}

// --------------------------------------------------------------------
// CommandLineFlag
//    This represents a single flag, including its name, description,
//    default value, and current value.  Mostly this serves as a
//    struct, though it also knows how to register itself.
//       All CommandLineFlags are owned by a (exactly one)
//    FlagRegistry.  If you wish to modify fields in this class, you
//    should acquire the FlagRegistry lock for the registry that owns
//    this flag.
// --------------------------------------------------------------------

class CommandLineFlag {
 public:
  // Note: we take over memory-ownership of current_val and default_val.
  CommandLineFlag(const char* name, const char* help, const char* filename,
                  FlagValue* current_val, FlagValue* default_val);
  ~CommandLineFlag();

  const char* name() const { return name_; }
  const char* help() const { return help_; }
  const char* filename() const { return file_; }
  const char* CleanFileName() const;  // nixes irrelevant prefix such as homedir
  string current_value() const { return current_->ToString(); }
  string default_value() const { return defvalue_->ToString(); }
  const char* type_name() const { return defvalue_->TypeName(); }
  ValidateFnProto validate_function() const { return validate_fn_proto_; }
  const void* flag_ptr() const { return current_->value_buffer_; }

  void FillCommandLineFlagInfo(struct CommandLineFlagInfo* result);

  // If validate_fn_proto_ is non-NULL, calls it on value, returns result.
  bool Validate(const FlagValue& value) const;
  bool ValidateCurrent() const { return Validate(*current_); }

 private:
  // for SetFlagLocked() and setting flags_by_ptr_
  friend class FlagRegistry;
  friend class GOOGLE_NAMESPACE::FlagSaverImpl;  // for cloning the values
  // set validate_fn
  friend bool AddFlagValidator(const void*, ValidateFnProto);

  // This copies all the non-const members: modified, processed, defvalue, etc.
  void CopyFrom(const CommandLineFlag& src);

  void UpdateModifiedBit();

  const char* const name_;     // Flag name
  const char* const help_;     // Help message
  const char* const file_;     // Which file did this come from?
  bool modified_;              // Set after default assignment?
  FlagValue* defvalue_;        // Default value for flag
  FlagValue* current_;         // Current value for flag
  // This is a casted, 'generic' version of validate_fn, which actually
  // takes a flag-value as an arg (void (*validate_fn)(bool), say).
  // When we pass this to current_->Validate(), it will cast it back to
  // the proper type.  This may be NULL to mean we have no validate_fn.
  ValidateFnProto validate_fn_proto_;

  CommandLineFlag(const CommandLineFlag&);   // no copying!
  void operator=(const CommandLineFlag&);
};

CommandLineFlag::CommandLineFlag(const char* name, const char* help,
                                 const char* filename,
                                 FlagValue* current_val, FlagValue* default_val)
    : name_(name), help_(help), file_(filename), modified_(false),
      defvalue_(default_val), current_(current_val), validate_fn_proto_(NULL) {
}

CommandLineFlag::~CommandLineFlag() {
  delete current_;
  delete defvalue_;
}

const char* CommandLineFlag::CleanFileName() const {
  // Compute top-level directory & file that this appears in
  // search full path backwards.
  // Stop going backwards at kRootDir; and skip by the first slash.
  static const char kRootDir[] = "";    // can set this to root directory,

  if (sizeof(kRootDir)-1 == 0)          // no prefix to strip
    return filename();

  const char* clean_name = filename() + strlen(filename()) - 1;
  while ( clean_name > filename() ) {
    if (*clean_name == PATH_SEPARATOR) {
      if (strncmp(clean_name, kRootDir, sizeof(kRootDir)-1) == 0) {
        clean_name += sizeof(kRootDir)-1;    // past root-dir
        break;
      }
    }
    --clean_name;
  }
  while ( *clean_name == PATH_SEPARATOR ) ++clean_name;  // Skip any slashes
  return clean_name;
}

void CommandLineFlag::FillCommandLineFlagInfo(
    CommandLineFlagInfo* result) {
  result->name = name();
  result->type = type_name();
  result->description = help();
  result->current_value = current_value();
  result->default_value = default_value();
  result->filename = CleanFileName();
  UpdateModifiedBit();
  result->is_default = !modified_;
  result->has_validator_fn = validate_function() != NULL;
  result->flag_ptr = flag_ptr();
}

void CommandLineFlag::UpdateModifiedBit() {
  // Update the "modified" bit in case somebody bypassed the
  // Flags API and wrote directly through the FLAGS_name variable.
  if (!modified_ && !current_->Equal(*defvalue_)) {
    modified_ = true;
  }
}

void CommandLineFlag::CopyFrom(const CommandLineFlag& src) {
  // Note we only copy the non-const members; others are fixed at construct time
  if (modified_ != src.modified_) modified_ = src.modified_;
  if (!current_->Equal(*src.current_)) current_->CopyFrom(*src.current_);
  if (!defvalue_->Equal(*src.defvalue_)) defvalue_->CopyFrom(*src.defvalue_);
  if (validate_fn_proto_ != src.validate_fn_proto_)
    validate_fn_proto_ = src.validate_fn_proto_;
}

bool CommandLineFlag::Validate(const FlagValue& value) const {

  if (validate_function() == NULL)
    return true;
  else
    return value.Validate(name(), validate_function());
}


// --------------------------------------------------------------------
// FlagRegistry
//    A FlagRegistry singleton object holds all flag objects indexed
//    by their names so that if you know a flag's name (as a C
//    string), you can access or set it.  If the function is named
//    FooLocked(), you must own the registry lock before calling
//    the function; otherwise, you should *not* hold the lock, and
//    the function will acquire it itself if needed.
// --------------------------------------------------------------------

struct StringCmp {  // Used by the FlagRegistry map class to compare char*'s
  bool operator() (const char* s1, const char* s2) const {
    return (strcmp(s1, s2) < 0);
  }
};


class FlagRegistry {
 public:
  FlagRegistry() {
  }
  ~FlagRegistry() {
    // Not using STLDeleteElements as that resides in util and this
    // class is base.
    for (FlagMap::iterator p = flags_.begin(), e = flags_.end(); p != e; ++p) {
      CommandLineFlag* flag = p->second;
      delete flag;
    }
  }

  static void DeleteGlobalRegistry() {
    delete global_registry_;
    global_registry_ = NULL;
  }

  // Store a flag in this registry.  Takes ownership of the given pointer.
  void RegisterFlag(CommandLineFlag* flag);

  void Lock() { lock_.Lock(); }
  void Unlock() { lock_.Unlock(); }

  // Returns the flag object for the specified name, or NULL if not found.
  CommandLineFlag* FindFlagLocked(const char* name);

  // Returns the flag object whose current-value is stored at flag_ptr.
  // That is, for whom current_->value_buffer_ == flag_ptr
  CommandLineFlag* FindFlagViaPtrLocked(const void* flag_ptr);

  // A fancier form of FindFlag that works correctly if name is of the
  // form flag=value.  In that case, we set key to point to flag, and
  // modify v to point to the value (if present), and return the flag
  // with the given name.  If the flag does not exist, returns NULL
  // and sets error_message.
  CommandLineFlag* SplitArgumentLocked(const char* argument,
                                       string* key, const char** v,
                                       string* error_message);

  // Set the value of a flag.  If the flag was successfully set to
  // value, set msg to indicate the new flag-value, and return true.
  // Otherwise, set msg to indicate the error, leave flag unchanged,
  // and return false.  msg can be NULL.
  bool SetFlagLocked(CommandLineFlag* flag, const char* value,
                     FlagSettingMode set_mode, string* msg);

  static FlagRegistry* GlobalRegistry();   // returns a singleton registry

 private:
  friend class GOOGLE_NAMESPACE::FlagSaverImpl;  // reads all the flags in order to copy them
  friend class CommandLineFlagParser;    // for ValidateAllFlags
  friend void GOOGLE_NAMESPACE::GetAllFlags(vector<CommandLineFlagInfo>*);

  // The map from name to flag, for FindFlagLocked().
  typedef map<const char*, CommandLineFlag*, StringCmp> FlagMap;
  typedef FlagMap::iterator FlagIterator;
  typedef FlagMap::const_iterator FlagConstIterator;
  FlagMap flags_;

  // The map from current-value pointer to flag, fo FindFlagViaPtrLocked().
  typedef map<const void*, CommandLineFlag*> FlagPtrMap;
  FlagPtrMap flags_by_ptr_;

  static FlagRegistry* global_registry_;   // a singleton registry

  Mutex lock_;
  static Mutex global_registry_lock_;

  static void InitGlobalRegistry();

  // Disallow
  FlagRegistry(const FlagRegistry&);
  FlagRegistry& operator=(const FlagRegistry&);
};

class FlagRegistryLock {
 public:
  explicit FlagRegistryLock(FlagRegistry* fr) : fr_(fr) { fr_->Lock(); }
  ~FlagRegistryLock() { fr_->Unlock(); }
 private:
  FlagRegistry *const fr_;
};


void FlagRegistry::RegisterFlag(CommandLineFlag* flag) {
  Lock();
  pair<FlagIterator, bool> ins =
    flags_.insert(pair<const char*, CommandLineFlag*>(flag->name(), flag));
  if (ins.second == false) {   // means the name was already in the map
    if (strcmp(ins.first->second->filename(), flag->filename()) != 0) {
      ReportError(DIE, "ERROR: flag '%s' was defined more than once "
                  "(in files '%s' and '%s').\n",
                  flag->name(),
                  ins.first->second->filename(),
                  flag->filename());
    } else {
      ReportError(DIE, "ERROR: something wrong with flag '%s' in file '%s'.  "
                  "One possibility: file '%s' is being linked both statically "
                  "and dynamically into this executable.\n",
                  flag->name(),
                  flag->filename(), flag->filename());
    }
  }
  // Also add to the flags_by_ptr_ map.
  flags_by_ptr_[flag->current_->value_buffer_] = flag;
  Unlock();
}

CommandLineFlag* FlagRegistry::FindFlagLocked(const char* name) {
  FlagConstIterator i = flags_.find(name);
  if (i == flags_.end()) {
    return NULL;
  } else {
    return i->second;
  }
}

CommandLineFlag* FlagRegistry::FindFlagViaPtrLocked(const void* flag_ptr) {
  FlagPtrMap::const_iterator i = flags_by_ptr_.find(flag_ptr);
  if (i == flags_by_ptr_.end()) {
    return NULL;
  } else {
    return i->second;
  }
}

CommandLineFlag* FlagRegistry::SplitArgumentLocked(const char* arg,
                                                   string* key,
                                                   const char** v,
                                                   string* error_message) {
  // Find the flag object for this option
  const char* flag_name;
  const char* value = strchr(arg, '=');
  if (value == NULL) {
    key->assign(arg);
    *v = NULL;
  } else {
    // Strip out the "=value" portion from arg
    key->assign(arg, value-arg);
    *v = ++value;    // advance past the '='
  }
  flag_name = key->c_str();

  CommandLineFlag* flag = FindFlagLocked(flag_name);

  if (flag == NULL) {
    // If we can't find the flag-name, then we should return an error.
    // The one exception is if 1) the flag-name is 'nox', 2) there
    // exists a flag named 'x', and 3) 'x' is a boolean flag.
    // In that case, we want to return flag 'x'.
    if (!(flag_name[0] == 'n' && flag_name[1] == 'o')) {
      // flag-name is not 'nox', so we're not in the exception case.
      *error_message = StringPrintf("%sunknown command line flag '%s'\n",
                                    kError, key->c_str());
      return NULL;
    }
    flag = FindFlagLocked(flag_name+2);
    if (flag == NULL) {
      // No flag named 'x' exists, so we're not in the exception case.
      *error_message = StringPrintf("%sunknown command line flag '%s'\n",
                                    kError, key->c_str());
      return NULL;
    }
    if (strcmp(flag->type_name(), "bool") != 0) {
      // 'x' exists but is not boolean, so we're not in the exception case.
      *error_message = StringPrintf(
          "%sboolean value (%s) specified for %s command line flag\n",
          kError, key->c_str(), flag->type_name());
      return NULL;
    }
    // We're in the exception case!
    // Make up a fake value to replace the "no" we stripped out
    key->assign(flag_name+2);   // the name without the "no"
    *v = "0";
  }

  // Assign a value if this is a boolean flag
  if (*v == NULL && strcmp(flag->type_name(), "bool") == 0) {
    *v = "1";    // the --nox case was already handled, so this is the --x case
  }

  return flag;
}

bool TryParseLocked(const CommandLineFlag* flag, FlagValue* flag_value,
                    const char* value, string* msg) {
  // Use tenative_value, not flag_value, until we know value is valid.
  FlagValue* tentative_value = flag_value->New();
  if (!tentative_value->ParseFrom(value)) {
    if (msg) {
      StringAppendF(msg,
                    "%sillegal value '%s' specified for %s flag '%s'\n",
                    kError, value,
                    flag->type_name(), flag->name());
    }
    delete tentative_value;
    return false;
  } else if (!flag->Validate(*tentative_value)) {
    if (msg) {
      StringAppendF(msg,
          "%sfailed validation of new value '%s' for flag '%s'\n",
          kError, tentative_value->ToString().c_str(),
          flag->name());
    }
    delete tentative_value;
    return false;
  } else {
    flag_value->CopyFrom(*tentative_value);
    if (msg) {
      StringAppendF(msg, "%s set to %s\n",
                    flag->name(), flag_value->ToString().c_str());
    }
    delete tentative_value;
    return true;
  }
}

bool FlagRegistry::SetFlagLocked(CommandLineFlag* flag,
                                 const char* value,
                                 FlagSettingMode set_mode,
                                 string* msg) {
  flag->UpdateModifiedBit();
  switch (set_mode) {
    case SET_FLAGS_VALUE: {
      // set or modify the flag's value
      if (!TryParseLocked(flag, flag->current_, value, msg))
        return false;
      flag->modified_ = true;
      break;
    }
    case SET_FLAG_IF_DEFAULT: {
      // set the flag's value, but only if it hasn't been set by someone else
      if (!flag->modified_) {
        if (!TryParseLocked(flag, flag->current_, value, msg))
          return false;
        flag->modified_ = true;
      } else {
        *msg = StringPrintf("%s set to %s",
                            flag->name(), flag->current_value().c_str());
      }
      break;
    }
    case SET_FLAGS_DEFAULT: {
      // modify the flag's default-value
      if (!TryParseLocked(flag, flag->defvalue_, value, msg))
        return false;
      if (!flag->modified_) {
        // Need to set both defvalue *and* current, in this case
        TryParseLocked(flag, flag->current_, value, NULL);
      }
      break;
    }
    default: {
      // unknown set_mode
      assert(false);
      return false;
    }
  }

  return true;
}

// Get the singleton FlagRegistry object
FlagRegistry* FlagRegistry::global_registry_ = NULL;
Mutex FlagRegistry::global_registry_lock_(Mutex::LINKER_INITIALIZED);

FlagRegistry* FlagRegistry::GlobalRegistry() {
  MutexLock acquire_lock(&global_registry_lock_);
  if (!global_registry_) {
    global_registry_ = new FlagRegistry;
  }
  return global_registry_;
}

// --------------------------------------------------------------------
// CommandLineFlagParser
//    Parsing is done in two stages.  In the first, we go through
//    argv.  For every flag-like arg we can make sense of, we parse
//    it and set the appropriate FLAGS_* variable.  For every flag-
//    like arg we can't make sense of, we store it in a vector,
//    along with an explanation of the trouble.  In stage 2, we
//    handle the 'reporting' flags like --help and --mpm_version.
//    (This is via a call to HandleCommandLineHelpFlags(), in
//    gflags_reporting.cc.)
//    An optional stage 3 prints out the error messages.
//       This is a bit of a simplification.  For instance, --flagfile
//    is handled as soon as it's seen in stage 1, not in stage 2.
// --------------------------------------------------------------------

class CommandLineFlagParser {
 public:
  // The argument is the flag-registry to register the parsed flags in
  explicit CommandLineFlagParser(FlagRegistry* reg) : registry_(reg) {}
  ~CommandLineFlagParser() {}

  // Stage 1: Every time this is called, it reads all flags in argv.
  // However, it ignores all flags that have been successfully set
  // before.  Typically this is only called once, so this 'reparsing'
  // behavior isn't important.  It can be useful when trying to
  // reparse after loading a dll, though.
  uint32 ParseNewCommandLineFlags(int* argc, char*** argv, bool remove_flags);

  // Stage 2: print reporting info and exit, if requested.
  // In gflags_reporting.cc:HandleCommandLineHelpFlags().

  // Stage 3: validate all the commandline flags that have validators
  // registered.
  void ValidateAllFlags();

  // Stage 4: report any errors and return true if any were found.
  bool ReportErrors();

  // Set a particular command line option.  "newval" is a string
  // describing the new value that the option has been set to.  If
  // option_name does not specify a valid option name, or value is not
  // a valid value for option_name, newval is empty.  Does recursive
  // processing for --flagfile and --fromenv.  Returns the new value
  // if everything went ok, or empty-string if not.  (Actually, the
  // return-string could hold many flag/value pairs due to --flagfile.)
  // NB: Must have called registry_->Lock() before calling this function.
  string ProcessSingleOptionLocked(CommandLineFlag* flag,
                                   const char* value,
                                   FlagSettingMode set_mode);

  // Set a whole batch of command line options as specified by contentdata,
  // which is in flagfile format (and probably has been read from a flagfile).
  // Returns the new value if everything went ok, or empty-string if
  // not.  (Actually, the return-string could hold many flag/value
  // pairs due to --flagfile.)
  // NB: Must have called registry_->Lock() before calling this function.
  string ProcessOptionsFromStringLocked(const string& contentdata,
                                        FlagSettingMode set_mode);

  // These are the 'recursive' flags, defined at the top of this file.
  // Whenever we see these flags on the commandline, we must take action.
  // These are called by ProcessSingleOptionLocked and, similarly, return
  // new values if everything went ok, or the empty-string if not.
  string ProcessFlagfileLocked(const string& flagval, FlagSettingMode set_mode);
  // diff fromenv/tryfromenv
  string ProcessFromenvLocked(const string& flagval, FlagSettingMode set_mode,
                              bool errors_are_fatal);

 private:
  FlagRegistry* const registry_;
  map<string, string> error_flags_;      // map from name to error message
  // This could be a set<string>, but we reuse the map to minimize the .o size
  map<string, string> undefined_names_;  // --[flag] name was not registered
};


// Parse a list of (comma-separated) flags.
static void ParseFlagList(const char* value, vector<string>* flags) {
  for (const char *p = value; p && *p; value = p) {
    p = strchr(value, ',');
    size_t len;
    if (p) {
      len = p - value;
      p++;
    } else {
      len = strlen(value);
    }

    if (len == 0)
      ReportError(DIE, "ERROR: empty flaglist entry\n");
    if (value[0] == '-')
      ReportError(DIE, "ERROR: flag \"%*s\" begins with '-'\n", len, value);

    flags->push_back(string(value, len));
  }
}

// Snarf an entire file into a C++ string.  This is just so that we
// can do all the I/O in one place and not worry about it everywhere.
// Plus, it's convenient to have the whole file contents at hand.
// Adds a newline at the end of the file.
#define PFATAL(s)  do { perror(s); gflags_exitfunc(1); } while (0)