gflags.cc

  // 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, ',');
    int len;
    if (p) {
      len = static_cast<int>(p - value);
      p++;
    } else {
      len = static_cast<int>(strlen(value));
    }

    if (len == 0) {
      fprintf(stderr, "ERROR: empty flaglist entry\n");
      commandlineflags_exitfunc(1);   // almost certainly exit()
    }
    if (value[0] == '-') {
      fprintf(stderr, "ERROR: flag \"%*s\" begins with '-'\n", len, value);
      commandlineflags_exitfunc(1);
    }

    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); commandlineflags_exitfunc(1); } while (0)

static string ReadFileIntoString(const char* filename) {
  const int kBufSize = 8092;
  char buffer[kBufSize];
  string s;
  FILE* fp = fopen(filename, "r");
  if (!fp)  PFATAL(filename);
  size_t n;
  while ( (n=fread(buffer, 1, kBufSize, fp)) > 0 ) {
    if (ferror(fp))  PFATAL(filename);
    s.append(buffer, n);
  }
  fclose(fp);
  return s;
}

uint32 CommandLineFlagParser::ParseNewCommandLineFlags(int* argc, char*** argv,
                                                       bool remove_flags) {
  const char *program_name = strrchr((*argv)[0], PATH_SEPARATOR);   // nix path
  program_name = (program_name == NULL ? (*argv)[0] : program_name+1);

  int first_nonopt = *argc;        // for non-options moved to the end

  registry_->Lock();
  for (int i = 1; i < first_nonopt; i++) {
    char* arg = (*argv)[i];

    // Like getopt(), we permute non-option flags to be at the end.
    if (arg[0] != '-' ||           // must be a program argument
        (arg[0] == '-' && arg[1] == '\0')) {  // "-" is an argument, not a flag
      memmove((*argv) + i, (*argv) + i+1, (*argc - (i+1)) * sizeof((*argv)[i]));
      (*argv)[*argc-1] = arg;      // we go last
      first_nonopt--;              // we've been pushed onto the stack
      i--;                         // to undo the i++ in the loop
      continue;
    }

    if (arg[0] == '-') arg++;      // allow leading '-'
    if (arg[0] == '-') arg++;      // or leading '--'

    // -- alone means what it does for GNU: stop options parsing
    if (*arg == '\0') {
      first_nonopt = i+1;
      break;
    }

    // Find the flag object for this option
    string key;
    const char* value;
    string error_message;
    CommandLineFlag* flag = registry_->SplitArgumentLocked(arg, &key, &value,
                                                           &error_message);
    if (flag == NULL) {
      undefined_names_[key] = "";    // value isn't actually used
      error_flags_[key] = error_message;
      continue;
    }

    if (value == NULL) {
      // Boolean options are always assigned a value by SplitArgumentLocked()
      assert(strcmp(flag->type_name(), "bool") != 0);
      if (i+1 >= first_nonopt) {
        // This flag needs a value, but there is nothing available
        error_flags_[key] = (string(kError) + "flag '" + (*argv)[i] + "'"
                             + " is missing its argument");
        if (flag->help() && flag->help()[0] > '\001') {
          // Be useful in case we have a non-stripped description.
          error_flags_[key] += string("; flag description: ") + flag->help();
        }
        error_flags_[key] += "\n";
        break;    // we treat this as an unrecoverable error
      } else {
        value = (*argv)[++i];                   // read next arg for value
      }
    }

    // TODO(csilvers): only set a flag if we hadn't set it before here
    ProcessSingleOptionLocked(flag, value, SET_FLAGS_VALUE);
  }
  registry_->Unlock();

  if (remove_flags) {   // Fix up argc and argv by removing command line flags
    (*argv)[first_nonopt-1] = (*argv)[0];
    (*argv) += (first_nonopt-1);
    (*argc) -= (first_nonopt-1);
    first_nonopt = 1;   // because we still don't count argv[0]
  }

  logging_is_probably_set_up = true;   // because we've parsed --logdir, etc.

  return first_nonopt;
}

string CommandLineFlagParser::ProcessFlagfileLocked(const string& flagval,
                                                    FlagSettingMode set_mode) {
  if (flagval.empty())
    return "";

  string msg;
  vector<string> filename_list;
  ParseFlagList(flagval.c_str(), &filename_list);  // take a list of filenames
  for (size_t i = 0; i < filename_list.size(); ++i) {
    const char* file = filename_list[i].c_str();
    msg += ProcessOptionsFromStringLocked(ReadFileIntoString(file), set_mode);
  }
  return msg;
}

string CommandLineFlagParser::ProcessFromenvLocked(const string& flagval,
                                                   FlagSettingMode set_mode,
                                                   bool errors_are_fatal) {
  if (flagval.empty())
    return "";

  string msg;
  vector<string> flaglist;
  ParseFlagList(flagval.c_str(), &flaglist);

  for (size_t i = 0; i < flaglist.size(); ++i) {
    const char* flagname = flaglist[i].c_str();
    CommandLineFlag* flag = registry_->FindFlagLocked(flagname);
    if (flag == NULL) {
      error_flags_[flagname] = (string(kError) + "unknown command line flag"
                                + " '" + flagname + "'"
                                + " (via --fromenv or --tryfromenv)\n");
      undefined_names_[flagname] = "";
      continue;
    }

    const string envname = string("FLAGS_") + string(flagname);
    const char* envval = getenv(envname.c_str());
    if (!envval) {
      if (errors_are_fatal) {
        error_flags_[flagname] = (string(kError) + envname +
                                  " not found in environment\n");
      }
      continue;
    }

    // Avoid infinite recursion.
    if ((strcmp(envval, "fromenv") == 0) ||
        (strcmp(envval, "tryfromenv") == 0)) {
      error_flags_[flagname] = (string(kError) + "infinite recursion on " +
                                "environment flag '" + envval + "'\n");
      continue;
    }

    msg += ProcessSingleOptionLocked(flag, envval, set_mode);
  }
  return msg;
}

string CommandLineFlagParser::ProcessSingleOptionLocked(
    CommandLineFlag* flag, const char* value, FlagSettingMode set_mode) {
  string msg;
  if (value && !registry_->SetFlagLocked(flag, value, set_mode, &msg)) {
    error_flags_[flag->name()] = msg;
    return "";
  }

  // The recursive flags, --flagfile and --fromenv and --tryfromenv,
  // must be dealt with as soon as they're seen.  They will emit
  // messages of their own.
  if (strcmp(flag->name(), "flagfile") == 0) {
    msg += ProcessFlagfileLocked(FLAGS_flagfile, set_mode);

  } else if (strcmp(flag->name(), "fromenv") == 0) {
    // last arg indicates envval-not-found is fatal (unlike in --tryfromenv)
    msg += ProcessFromenvLocked(FLAGS_fromenv, set_mode, true);

  } else if (strcmp(flag->name(), "tryfromenv") == 0) {
    msg += ProcessFromenvLocked(FLAGS_tryfromenv, set_mode, false);
  }

  return msg;
}

void CommandLineFlagParser::ValidateAllFlags() {
  FlagRegistryLock frl(registry_);
  for (FlagRegistry::FlagConstIterator i = registry_->flags_.begin();
       i != registry_->flags_.end(); ++i) {
    if (!i->second->ValidateCurrent()) {
      // only set a message if one isn't already there.  (If there's
      // an error message, our job is done, even if it's not exactly
      // the same error.)
      if (error_flags_[i->second->name()].empty())
        error_flags_[i->second->name()] = (string(kError) +
                                           "--" + i->second->name() +
                                           " must be set on the commandline" +
                                           " (default value fails validation)");
    }
  }
}

bool CommandLineFlagParser::ReportErrors() {
  // error_flags_ indicates errors we saw while parsing.
  // But we ignore undefined-names if ok'ed by --undef_ok
  if (!FLAGS_undefok.empty()) {
    vector<string> flaglist;
    ParseFlagList(FLAGS_undefok.c_str(), &flaglist);
    for (size_t i = 0; i < flaglist.size(); ++i)
      if (undefined_names_.find(flaglist[i]) != undefined_names_.end()) {
        error_flags_[flaglist[i]] = "";    // clear the error message
      }
  }
  // Likewise, if they decided to allow reparsing, all undefined-names
  // are ok; we just silently ignore them now, and hope that a future
  // parse will pick them up somehow.
  if (allow_command_line_reparsing) {
    for (map<string, string>::const_iterator it = undefined_names_.begin();
         it != undefined_names_.end();  ++it)
      error_flags_[it->first] = "";      // clear the error message
  }

  bool found_error = false;
  for (map<string, string>::const_iterator it = error_flags_.begin();
       it != error_flags_.end(); ++it) {
    if (!it->second.empty()) {
      fprintf(stderr, "%s", it->second.c_str());
      found_error = true;
    }
  }
  return found_error;
}

string CommandLineFlagParser::ProcessOptionsFromStringLocked(
    const string& contentdata, FlagSettingMode set_mode) {
  string retval;
  const char* flagfile_contents = contentdata.c_str();
  bool flags_are_relevant = true;   // set to false when filenames don't match
  bool in_filename_section = false;

  const char* line_end = flagfile_contents;
  // We read this file a line at a time.
  for (; line_end; flagfile_contents = line_end + 1) {
    while (*flagfile_contents && isspace(*flagfile_contents))
      ++flagfile_contents;
    line_end = strchr(flagfile_contents, '\n');
    size_t len = line_end ? static_cast<size_t>(line_end - flagfile_contents)
                          : strlen(flagfile_contents);
    string line(flagfile_contents, len);

    // Each line can be one of four things:
    // 1) A comment line -- we skip it
    // 2) An empty line -- we skip it
    // 3) A list of filenames -- starts a new filenames+flags section
    // 4) A --flag=value line -- apply if previous filenames match
    if (line.empty() || line[0] == '#') {
      // comment or empty line; just ignore

    } else if (line[0] == '-') {    // flag
      in_filename_section = false;  // instead, it was a flag-line
      if (!flags_are_relevant)      // skip this flag; applies to someone else
        continue;

      const char* name_and_val = line.c_str() + 1;    // skip the leading -
      if (*name_and_val == '-')
        name_and_val++;                               // skip second - too
      string key;
      const char* value;
      string error_message;
      CommandLineFlag* flag = registry_->SplitArgumentLocked(name_and_val,
                                                             &key, &value,
                                                             &error_message);
      // By API, errors parsing flagfile lines are silently ignored.
      if (flag == NULL) {
        // "WARNING: flagname '" + key + "' not found\n"
      } else if (value == NULL) {
        // "WARNING: flagname '" + key + "' missing a value\n"
      } else {
        retval += ProcessSingleOptionLocked(flag, value, set_mode);
      }

    } else {                        // a filename!
      if (!in_filename_section) {   // start over: assume filenames don't match
        in_filename_section = true;
        flags_are_relevant = false;
      }

      // Split the line up at spaces into glob-patterns
      const char* space = line.c_str();   // just has to be non-NULL
      for (const char* word = line.c_str(); *space; word = space+1) {
        if (flags_are_relevant)     // we can stop as soon as we match
          break;
        space = strchr(word, ' ');
        if (space == NULL)
          space = word + strlen(word);
        const string glob(word, space - word);
        // We try matching both against the full argv0 and basename(argv0)
#ifdef HAVE_FNMATCH_H
        if (fnmatch(glob.c_str(),
                    ProgramInvocationName(),
                    FNM_PATHNAME) == 0 ||
            fnmatch(glob.c_str(),
                    ProgramInvocationShortName(),
                    FNM_PATHNAME) == 0) {
#else  // !HAVE_FNMATCH_H
        if ((glob == ProgramInvocationName()) ||
            (glob == ProgramInvocationShortName())) {
#endif  // HAVE_FNMATCH_H
          flags_are_relevant = true;
        }
      }
    }
  }
  return retval;
}

// --------------------------------------------------------------------
// GetFromEnv()
// AddFlagValidator()
//    These are helper functions for routines like BoolFromEnv() and
//    RegisterFlagValidator, defined below.  They're defined here so
//    they can live in the unnamed namespace (which makes friendship
//    declarations for these classes possible).
// --------------------------------------------------------------------

template<typename T>
T GetFromEnv(const char *varname, const char* type, T dflt) {
  const char* const valstr = getenv(varname);
  if (!valstr)
    return dflt;
  FlagValue ifv(new T, type);
  if (!ifv.ParseFrom(valstr)) {
    fprintf(stderr, "ERROR: error parsing env variable '%s' with value '%s'\n",
            varname, valstr);
    commandlineflags_exitfunc(1);
  }
  return OTHER_VALUE_AS(ifv, T);
}

bool AddFlagValidator(const void* flag_ptr, ValidateFnProto validate_fn_proto) {
  // We want a lock around this routine, in case two threads try to
  // add a validator (hopefully the same one!) at once.  We could use
  // our own thread, but we need to loook at the registry anyway, so
  // we just steal that one.
  FlagRegistry* const registry = FlagRegistry::GlobalRegistry();
  FlagRegistryLock frl(registry);
  // First, find the flag whose current-flag storage is 'flag'.
  // This is the CommandLineFlag whose current_->value_buffer_ == flag
  CommandLineFlag* flag = registry->FindFlagViaPtrLocked(flag_ptr);
  if (!flag) {
    // WARNING << "Ignoring RegisterValidateFunction() for flag pointer "
    //         << flag_ptr << ": no flag found at that address";
    return false;
  } else if (validate_fn_proto == flag->validate_function()) {
    return true;    // ok to register the same function over and over again
  } else if (validate_fn_proto != NULL && flag->validate_function() != NULL) {
    // WARNING << "Ignoring RegisterValidateFunction() for flag '"
    //         << flag->name() << "': validate-fn already registered";
    return false;
  } else {
    flag->validate_fn_proto_ = validate_fn_proto;
    return true;
  }
}

}  // end unnamed namespaces


// Now define the functions that are exported via the .h file

// --------------------------------------------------------------------
// FlagRegisterer
//    This class exists merely to have a global constructor (the
//    kind that runs before main(), that goes an initializes each
//    flag that's been declared.  Note that it's very important we
//    don't have a destructor that deletes flag_, because that would
//    cause us to delete current_storage/defvalue_storage as well,
//    which can cause a crash if anything tries to access the flag
//    values in a global destructor.
// --------------------------------------------------------------------

// TODO(csilvers): When we're ready to have this error be a fatal one,
// change this to give a compilation error (via COMPILE_ASSERT(false)).
bool FlagsTypeWarn(const char *name) {
  cerr << "Flag " << name << " is of type bool, but its default"
       << " value is not a boolean.  NOTE: This will soon be a"
       << " compilations error!";
  return false;
}

FlagRegisterer::FlagRegisterer(const char* name, const char* type,
                               const char* help, const char* filename,
                               void* current_storage, void* defvalue_storage) {
  if (help == NULL)
    help = "";
  // FlagValue expects the type-name to not include any namespace
  // components, so we get rid of those, if any.
  if (strchr(type, ':'))
    type = strrchr(type, ':') + 1;
  FlagValue* current = new FlagValue(current_storage, type);
  FlagValue* defvalue = new FlagValue(defvalue_storage, type);
  // Importantly, flag_ will never be deleted, so storage is always good.
  CommandLineFlag* flag = new CommandLineFlag(name, help, filename,
                                              current, defvalue);
  FlagRegistry::GlobalRegistry()->RegisterFlag(flag);   // default registry
}

// --------------------------------------------------------------------
// GetAllFlags()
//    The main way the FlagRegistry class exposes its data.  This
//    returns, as strings, all the info about all the flags in
//    the main registry, sorted first by filename they are defined
//    in, and then by flagname.
// --------------------------------------------------------------------

struct FilenameFlagnameCmp {
  bool operator()(const CommandLineFlagInfo& a,
                  const CommandLineFlagInfo& b) const {
    int cmp = strcmp(a.filename.c_str(), b.filename.c_str());
    if (cmp == 0)
      cmp = strcmp(a.name.c_str(), b.name.c_str());  // secondary sort key
    return cmp < 0;
  }
};

void GetAllFlags(vector<CommandLineFlagInfo>* OUTPUT) {
  FlagRegistry* const registry = FlagRegistry::GlobalRegistry();
  registry->Lock();
  for (FlagRegistry::FlagConstIterator i = registry->flags_.begin();
       i != registry->flags_.end(); ++i) {
    CommandLineFlagInfo fi;
    i->second->FillCommandLineFlagInfo(&fi);
    OUTPUT->push_back(fi);
  }
  registry->Unlock();
  // Now sort the flags, first by filename they occur in, then alphabetically
  sort(OUTPUT->begin(), OUTPUT->end(), FilenameFlagnameCmp());
}

// --------------------------------------------------------------------
// SetArgv()
// GetArgvs()
// GetArgv()
// GetArgv0()
// ProgramInvocationName()
// ProgramInvocationShortName()
// SetUsageMessage()
// ProgramUsage()
//    Functions to set and get argv.  Typically the setter is called
//    by ParseCommandLineFlags.  Also can get the ProgramUsage string,
//    set by SetUsageMessage.
// --------------------------------------------------------------------

// These values are not protected by a Mutex because they are normally
// set only once during program startup.
static const char* argv0 = "UNKNOWN";      // just the program name
static const char* cmdline = "";           // the entire command-line
static vector<string> argvs;
static uint32 argv_sum = 0;
static const char* program_usage = NULL;

void SetArgv(int argc, const char** argv) {
  static bool called_set_argv = false;
  if (called_set_argv)         // we already have an argv for you
    return;

  called_set_argv = true;

  assert(argc > 0);            // every program has at least a progname
  argv0 = strdup(argv[0]);     // small memory leak, but fn only called once
  assert(argv0);

  string cmdline_string;       // easier than doing strcats
  for (int i = 0; i < argc; i++) {
    if (i != 0) {
      cmdline_string += " ";
    }
    cmdline_string += argv[i];
    argvs.push_back(argv[i]);
  }
  cmdline = strdup(cmdline_string.c_str());  // another small memory leak
  assert(cmdline);

  // Compute a simple sum of all the chars in argv
  for (const char* c = cmdline; *c; c++)
    argv_sum += *c;
}

const vector<string>& GetArgvs() { return argvs; }
const char* GetArgv()            { return cmdline; }
const char* GetArgv0()           { return argv0; }
uint32 GetArgvSum()              { return argv_sum; }
const char* ProgramInvocationName() {             // like the GNU libc fn
  return GetArgv0();
}
const char* ProgramInvocationShortName() {        // like the GNU libc fn
  const char* slash = strrchr(argv0, '/');
#ifdef OS_WINDOWS
  if (!slash)  slash = strrchr(argv0, '\\');
#endif
  return slash ? slash + 1 : argv0;
}

void SetUsageMessage(const string& usage) {
  if (program_usage != NULL) {
    fprintf(stderr, "ERROR: SetUsageMessage() called twice\n");
    exit(1);
  }
  program_usage = strdup(usage.c_str());      // small memory leak
}

const char* ProgramUsage() {
  if (program_usage) {
    return program_usage;
  }
  return "Warning: SetUsageMessage() never called";
}

// --------------------------------------------------------------------
// GetCommandLineOption()
// GetCommandLineFlagInfo()
// GetCommandLineFlagInfoOrDie()
// SetCommandLineOption()
// SetCommandLineOptionWithMode()
//    The programmatic way to set a flag's value, using a string
//    for its name rather than the variable itself (that is,
//    SetCommandLineOption("foo", x) rather than FLAGS_foo = x).
//    There's also a bit more flexibility here due to the various
//    set-modes, but typically these are used when you only have
//    that flag's name as a string, perhaps at runtime.
//    All of these work on the default, global registry.
//       For GetCommandLineOption, return false if no such flag
//    is known, true otherwise.  We clear "value" if a suitable
//    flag is found.
// --------------------------------------------------------------------


bool GetCommandLineOption(const char* name, string* value) {
  if (NULL == name)
    return false;
  assert(value);

  FlagRegistry* const registry = FlagRegistry::GlobalRegistry();
  FlagRegistryLock frl(registry);
  CommandLineFlag* flag = registry->FindFlagLocked(name);
  if (flag == NULL) {
    return false;
  } else {
    *value = flag->current_value();
    return true;
  }
}

bool GetCommandLineFlagInfo(const char* name, CommandLineFlagInfo* OUTPUT) {
  if (NULL == name) return false;
  FlagRegistry* const registry = FlagRegistry::GlobalRegistry();
  FlagRegistryLock frl(registry);
  CommandLineFlag* flag = registry->FindFlagLocked(name);
  if (flag == NULL) {
    return false;
  } else {
    assert(OUTPUT);
    flag->FillCommandLineFlagInfo(OUTPUT);
    return true;
  }
}

CommandLineFlagInfo GetCommandLineFlagInfoOrDie(const char* name) {
  CommandLineFlagInfo info;
  if (!GetCommandLineFlagInfo(name, &info)) {
    fprintf(stderr, "FATAL ERROR: flag name '%s' doesn't exit", name);
    commandlineflags_exitfunc(1);    // almost certainly exit()
  }
  return info;
}

string SetCommandLineOptionWithMode(const char* name, const char* value,
                                    FlagSettingMode set_mode) {
  string result;
  FlagRegistry* const registry = FlagRegistry::GlobalRegistry();
  FlagRegistryLock frl(registry);
  CommandLineFlag* flag = registry->FindFlagLocked(name);
  if (flag) {
    CommandLineFlagParser parser(registry);
    result = parser.ProcessSingleOptionLocked(flag, value, set_mode);
    if (!result.empty()) {   // in the error case, we've already logged
      // You could consider logging this change, if you wanted to know it:
      //fprintf(stderr, "%sFLAGS_%s\n",
      //        (set_mode == SET_FLAGS_DEFAULT ? "default value of " : ""),
      //        result);
    }
  }
  // The API of this function is that we return empty string on error
  return result;
}

string SetCommandLineOption(const char* name, const char* value) {
  return SetCommandLineOptionWithMode(name, value, SET_FLAGS_VALUE);
}

// --------------------------------------------------------------------
// FlagSaver
// FlagSaverImpl
//    This class stores the states of all flags at construct time,
//    and restores all flags to that state at destruct time.
//    Its major implementation challenge is that it never modifies
//    pointers in the 'main' registry, so global FLAG_* vars always
//    point to the right place.
// --------------------------------------------------------------------

class FlagSaverImpl {
 public:
  // Constructs an empty FlagSaverImpl object.
  explicit FlagSaverImpl(FlagRegistry* main_registry)
      : main_registry_(main_registry) { }
  ~FlagSaverImpl() {
    // reclaim memory from each of our CommandLineFlags
    vector<CommandLineFlag*>::const_iterator it;
    for (it = backup_registry_.begin(); it != backup_registry_.end(); ++it)
      delete *it;
  }

  // Saves the flag states from the flag registry into this object.
  // It's an error to call this more than once.
  // Must be called when the registry mutex is not held.
  void SaveFromRegistry() {
    FlagRegistryLock frl(main_registry_);
    assert(backup_registry_.empty());   // call only once!
    for (FlagRegistry::FlagConstIterator it = main_registry_->flags_.begin();
         it != main_registry_->flags_.end();
         ++it) {
      const CommandLineFlag* main = it->second;
      // Sets up all the const variables in backup correctly
      CommandLineFlag* backup = new CommandLineFlag(
          main->name(), main->help(), main->filename(),
          main->current_->New(), main->defvalue_->New());
      // Sets up all the non-const variables in backup correctly
      backup->CopyFrom(*main);
      backup_registry_.push_back(backup);   // add it to a convenient list
    }
  }

  // Restores the saved flag states into the flag registry.  We
  // assume no flags were added or deleted from the registry since
  // the SaveFromRegistry; if they were, that's trouble!  Must be
  // called when the registry mutex is not held.
  void RestoreToRegistry() {
    FlagRegistryLock frl(main_registry_);
    vector<CommandLineFlag*>::const_iterator it;
    for (it = backup_registry_.begin(); it != backup_registry_.end(); ++it) {
      CommandLineFlag* main = main_registry_->FindFlagLocked((*it)->name());
      if (main != NULL) {       // if NULL, flag got deleted from registry(!)
        main->CopyFrom(**it);
      }
    }
  }

 private:
  FlagRegistry* const main_registry_;
  vector<CommandLineFlag*> backup_registry_;

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

FlagSaver::FlagSaver()
    : impl_(new FlagSaverImpl(FlagRegistry::GlobalRegistry())) {
  impl_->SaveFromRegistry();
}

FlagSaver::~FlagSaver() {
  impl_->RestoreToRegistry();
  delete impl_;
}


// --------------------------------------------------------------------
// CommandlineFlagsIntoString()
// ReadFlagsFromString()
// AppendFlagsIntoFile()
// ReadFromFlagsFile()
//    These are mostly-deprecated routines that stick the
//    commandline flags into a file/string and read them back
//    out again.  I can see a use for CommandlineFlagsIntoString,
//    for creating a flagfile, but the rest don't seem that useful
//    -- some, I think, are a poor-man's attempt at FlagSaver --
//    and are included only until we can delete them from callers.
//    Note they don't save --flagfile flags (though they do save
//    the result of having called the flagfile, of course).
// --------------------------------------------------------------------

static string TheseCommandlineFlagsIntoString(
    const vector<CommandLineFlagInfo>& flags) {
  vector<CommandLineFlagInfo>::const_iterator i;

  size_t retval_space = 0;
  for (i = flags.begin(); i != flags.end(); ++i) {
    // An (over)estimate of how much space it will take to print this flag
    retval_space += i->name.length() + i->current_value.length() + 5;
  }

  string retval;
  retval.reserve(retval_space);
  for (i = flags.begin(); i != flags.end(); ++i) {
    retval += "--";
    retval += i->name;
    retval += "=";
    retval += i->current_value;
    retval += "\n";
  }
  return retval;
}

string CommandlineFlagsIntoString() {
  vector<CommandLineFlagInfo> sorted_flags;
  GetAllFlags(&sorted_flags);
  return TheseCommandlineFlagsIntoString(sorted_flags);
}

bool ReadFlagsFromString(const string& flagfilecontents,
                         const char* /*prog_name*/,  // TODO(csilvers): nix this
                         bool errors_are_fatal) {
  FlagRegistry* const registry = FlagRegistry::GlobalRegistry();
  FlagSaverImpl saved_states(registry);
  saved_states.SaveFromRegistry();

  CommandLineFlagParser parser(registry);
  registry->Lock();
  parser.ProcessOptionsFromStringLocked(flagfilecontents, SET_FLAGS_VALUE);
  registry->Unlock();
  // Should we handle --help and such when reading flags from a string?  Sure.
  HandleCommandLineHelpFlags();
  if (parser.ReportErrors()) {
    // Error.  Restore all global flags to their previous values.
    if (errors_are_fatal)
      commandlineflags_exitfunc(1);    // almost certainly exit()
    saved_states.RestoreToRegistry();
    return false;
  }
  return true;
}

// TODO(csilvers): nix prog_name in favor of ProgramInvocationShortName()
bool AppendFlagsIntoFile(const string& filename, const char *prog_name) {
  FILE *fp = fopen(filename.c_str(), "a");
  if (!fp) {
    return false;
  }

  if (prog_name)
    fprintf(fp, "%s\n", prog_name);

  vector<CommandLineFlagInfo> flags;
  GetAllFlags(&flags);
  // But we don't want --flagfile, which leads to weird recursion issues
  vector<CommandLineFlagInfo>::iterator i;
  for (i = flags.begin(); i != flags.end(); ++i) {
    if (strcmp(i->name.c_str(), "flagfile") == 0) {
      flags.erase(i);
      break;
    }
  }
  fprintf(fp, "%s", TheseCommandlineFlagsIntoString(flags).c_str());

  fclose(fp);
  return true;
}

bool ReadFromFlagsFile(const string& filename, const char* prog_name,
                       bool errors_are_fatal) {
  return ReadFlagsFromString(ReadFileIntoString(filename.c_str()),
                             prog_name, errors_are_fatal);
}


// --------------------------------------------------------------------
// BoolFromEnv()
// Int32FromEnv()
// Int64FromEnv()
// Uint64FromEnv()
// DoubleFromEnv()
// StringFromEnv()
//    Reads the value from the environment and returns it.
//    We use an FlagValue to make the parsing easy.
//    Example usage:
//       DEFINE_bool(myflag, BoolFromEnv("MYFLAG_DEFAULT", false), "whatever");
// --------------------------------------------------------------------

bool BoolFromEnv(const char *v, bool dflt) {
  return GetFromEnv(v, "bool", dflt);
}
int32 Int32FromEnv(const char *v, int32 dflt) {
  return GetFromEnv(v, "int32", dflt);
}
int64 Int64FromEnv(const char *v, int64 dflt)    {
  return GetFromEnv(v, "int64", dflt);
}
uint64 Uint64FromEnv(const char *v, uint64 dflt) {
  return GetFromEnv(v, "uint64", dflt);
}
double DoubleFromEnv(const char *v, double dflt) {
  return GetFromEnv(v, "double", dflt);
}
const char *StringFromEnv(const char *varname, const char *dflt) {
  const char* const val = getenv(varname);
  return val ? val : dflt;
}


// --------------------------------------------------------------------
// RegisterFlagValidator()
//    RegisterFlagValidator() is the function that clients use to
//    'decorate' a flag with a validation function.  Once this is
//    done, every time the flag is set (including when the flag
//    is parsed from argv), the validator-function is called.
//       These functions return true if the validator was added
//    successfully, or false if not: the flag already has a validator,
//    (only one allowed per flag), the 1st arg isn't a flag, etc.
//       This function is not thread-safe.
// --------------------------------------------------------------------

bool RegisterFlagValidator(const bool* flag,
                           bool (*validate_fn)(const char*, bool)) {
  return AddFlagValidator(flag, reinterpret_cast<ValidateFnProto>(validate_fn));
}
bool RegisterFlagValidator(const int32* flag,
                           bool (*validate_fn)(const char*, int32)) {
  return AddFlagValidator(flag, reinterpret_cast<ValidateFnProto>(validate_fn));
}
bool RegisterFlagValidator(const int64* flag,
                           bool (*validate_fn)(const char*, int64)) {
  return AddFlagValidator(flag, reinterpret_cast<ValidateFnProto>(validate_fn));
}
bool RegisterFlagValidator(const uint64* flag,
                           bool (*validate_fn)(const char*, uint64)) {
  return AddFlagValidator(flag, reinterpret_cast<ValidateFnProto>(validate_fn));
}
bool RegisterFlagValidator(const double* flag,
                           bool (*validate_fn)(const char*, double)) {
  return AddFlagValidator(flag, reinterpret_cast<ValidateFnProto>(validate_fn));
}
bool RegisterFlagValidator(const string* flag,
                           bool (*validate_fn)(const char*, const string&)) {
  return AddFlagValidator(flag, reinterpret_cast<ValidateFnProto>(validate_fn));
}


// --------------------------------------------------------------------
// ParseCommandLineFlags()
// ParseCommandLineNonHelpFlags()
// HandleCommandLineHelpFlags()
//    This is the main function called from main(), to actually
//    parse the commandline.  It modifies argc and argv as described
//    at the top of gflags.h.  You can also divide this
//    function into two parts, if you want to do work between
//    the parsing of the flags and the printing of any help output.
// --------------------------------------------------------------------

static uint32 ParseCommandLineFlagsInternal(int* argc, char*** argv,
                                            bool remove_flags, bool do_report) {
  SetArgv(*argc, const_cast<const char**>(*argv));    // save it for later

  FlagRegistry* const registry = FlagRegistry::GlobalRegistry();
  CommandLineFlagParser parser(registry);

  // When we parse the commandline flags, we'll handle --flagfile,
  // --tryfromenv, etc. as we see them (since flag-evaluation order
  // may be important).  But sometimes apps set FLAGS_tryfromenv/etc.
  // manually before calling ParseCommandLineFlags.  We want to evaluate
  // those too, as if they were the first flags on the commandline.
  registry->Lock();
  parser.ProcessFlagfileLocked(FLAGS_flagfile, SET_FLAGS_VALUE);
  // Last arg here indicates whether flag-not-found is a fatal error or not
  parser.ProcessFromenvLocked(FLAGS_fromenv, SET_FLAGS_VALUE, true);
  parser.ProcessFromenvLocked(FLAGS_tryfromenv, SET_FLAGS_VALUE, false);
  registry->Unlock();

  // Now get the flags specified on the commandline
  const int r = parser.ParseNewCommandLineFlags(argc, argv, remove_flags);

  if (do_report)
    HandleCommandLineHelpFlags();   // may cause us to exit on --help, etc.

  // See if any of the unset flags fail their validation checks
  parser.ValidateAllFlags();

  if (parser.ReportErrors())        // may cause us to exit on illegal flags
    commandlineflags_exitfunc(1);   // almost certainly exit()
  return r;
}

uint32 ParseCommandLineFlags(int* argc, char*** argv, bool remove_flags) {
  return ParseCommandLineFlagsInternal(argc, argv, remove_flags, true);
}

uint32 ParseCommandLineNonHelpFlags(int* argc, char*** argv,
                                    bool remove_flags) {
  return ParseCommandLineFlagsInternal(argc, argv, remove_flags, false);
}

// --------------------------------------------------------------------
// AllowCommandLineReparsing()
// ReparseCommandLineNonHelpFlags()
//    This is most useful for shared libraries.  The idea is if
//    a flag is defined in a shared library that is dlopen'ed
//    sometime after main(), you can ParseCommandLineFlags before
//    the dlopen, then ReparseCommandLineNonHelpFlags() after the
//    dlopen, to get the new flags.  But you have to explicitly
//    Allow() it; otherwise, you get the normal default behavior
//    of unrecognized flags calling a fatal error.
// TODO(csilvers): this isn't used.  Just delete it?
// --------------------------------------------------------------------

void AllowCommandLineReparsing() {
  allow_command_line_reparsing = true;
}

uint32 ReparseCommandLineNonHelpFlags() {
  // We make a copy of argc and argv to pass in
  const vector<string>& argvs = GetArgvs();
  int tmp_argc = static_cast<int>(argvs.size());
  char** tmp_argv = new char* [tmp_argc + 1];
  for (int i = 0; i < tmp_argc; ++i)
    tmp_argv[i] = strdup(argvs[i].c_str());   // TODO(csilvers): don't dup

  const int retval = ParseCommandLineNonHelpFlags(&tmp_argc, &tmp_argv, false);

  for (int i = 0; i < tmp_argc; ++i)
    free(tmp_argv[i]);
  delete[] tmp_argv;

  return retval;
}

_END_GOOGLE_NAMESPACE_