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// 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.
// ---
// 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.
#include <gflags/gflags.h>
#include <assert.h>
#include <ctype.h>
#include <errno.h>
# include <fnmatch.h>
#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"
#define PATH_SEPARATOR '/'
// 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");
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
const char kStrippedFlagHelp[] = "\001\002\003\004 (unknown) \004\003\002\001";
namespace {
// There are also 'reporting' flags, in
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);
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 {
FlagValue(void* valbuf, const char* type, bool transfer_ownership_of_value);
bool ParseFrom(const char* spec);
string ToString() const;
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,
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())) {
assert(type_ <= FV_MAX_INDEX); // Unknown typename
FlagValue::~FlagValue() {
if (!owns_value_) {
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;
snprintf(intbuf, sizeof(intbuf), "%.17g", VALUE_AS(double));
return intbuf;
return VALUE_AS(string);
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));
return reinterpret_cast<bool (*)(const char*, double)>(
validate_fn_proto)(flagname, VALUE_AS(double));
return reinterpret_cast<bool (*)(const char*, const string&)>(
validate_fn_proto)(flagname, VALUE_AS(string));
assert(false); // unknown type
return false;
const char* FlagValue::TypeName() const {
static const char types[] =
if (type_ > FV_MAX_INDEX) {
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[] = {
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 {
// 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);
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_); }
// 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
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();
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;
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 {
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
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 {
explicit FlagRegistryLock(FlagRegistry* fr) : fr_(fr) { fr_->Lock(); }
~FlagRegistryLock() { fr_->Unlock(); }
FlagRegistry *const fr_;
void FlagRegistry::RegisterFlag(CommandLineFlag* flag) {
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",
} 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->filename(), flag->filename());
// Also add to the flags_by_ptr_ map.
flags_by_ptr_[flag->current_->value_buffer_] = flag;
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) {
*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) {
"%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) {
"%sfailed validation of new value '%s' for flag '%s'\n",
kError, tentative_value->ToString().c_str(),
delete tentative_value;
return false;
} else {
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) {
switch (set_mode) {
// set or modify the flag's value
if (!TryParseLocked(flag, flag->current_, value, msg))
return false;
flag->modified_ = true;
// 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());
// 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);
default: {
// unknown set_mode
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
// 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 {
// 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
// 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);
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;
} 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)
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);
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
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
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;
// Find the flag object for this option
string key;
const char* value;
string error_message;
CommandLineFlag* flag = registry_->SplitArgumentLocked(arg, &key, &value,
if (flag == NULL) {
undefined_names_[key] = ""; // value isn't actually used
error_flags_[key] = error_message;
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
// Heuristic to detect the case where someone treats a string arg
// like a bool:
// --my_string_var --foo=bar
// We look for a flag of string type, whose value begins with a
// dash, and where the flag-name and value are separated by a
// space rather than an '='.
// To avoid false positives, we also require the word "true"
// or "false" in the help string. Without this, a valid usage
// "-lat -30.5" would trigger the warning. The common cases we
// want to solve talk about true and false as values.
if (value[0] == '-'
&& strcmp(flag->type_name(), "string") == 0
&& (strstr(flag->help(), "true")
|| strstr(flag->help(), "false"))) {
LOG(WARNING) << "Did you really mean to set flag '"
<< flag->name() << "' to the value '"
<< value << "'?";
// TODO(csilvers): only set a flag if we hadn't set it before here
ProcessSingleOptionLocked(flag, value, SET_FLAGS_VALUE);
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] =
StringPrintf("%sunknown command line flag '%s' "
"(via --fromenv or --tryfromenv)\n",
kError, flagname);
undefined_names_[flagname] = "";
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");
// Avoid infinite recursion.
if ((strcmp(envval, "fromenv") == 0) ||
(strcmp(envval, "tryfromenv") == 0)) {
error_flags_[flagname] =
StringPrintf("%sinfinite recursion on environment flag '%s'\n",
kError, envval);
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)\n";
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) {
// We also deal with --no<flag>, in case the flagname was boolean
const string no_version = string("no") + flaglist[i];
if (undefined_names_.find(flaglist[i]) != undefined_names_.end()) {
error_flags_[flaglist[i]] = ""; // clear the error message
} else if (undefined_names_.find(no_version) != undefined_names_.end()) {
error_flags_[no_version] = "";
// 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;
string error_message;
for (map<string, string>::const_iterator it = error_flags_.begin();
it != error_flags_.end(); ++it) {
if (!it->second.empty()) {
error_message.append(it->, it->second.size());
found_error = true;
if (found_error)
ReportError(DO_NOT_DIE, "%s", error_message.c_str());
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))
line_end = strchr(flagfile_contents, '\n');
size_t len = line_end ? 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
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,
// 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
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)
if (glob == ProgramInvocationName() // small optimization
|| glob == ProgramInvocationShortName()
|| fnmatch(glob.c_str(),
|| fnmatch(glob.c_str(),
) {
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, true);
if (!ifv.ParseFrom(valstr))
ReportError(DIE, "ERROR: error parsing env variable '%s' with value '%s'\n",
varname, valstr);
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) {
LOG(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) {
LOG(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.
// --------------------------------------------------------------------
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, false);
FlagValue* defvalue = new FlagValue(defvalue_storage, type, false);
// 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(,; // secondary sort key
return cmp < 0;
void GetAllFlags(vector<CommandLineFlagInfo>* OUTPUT) {
FlagRegistry* const registry = FlagRegistry::GlobalRegistry();
for (FlagRegistry::FlagConstIterator i = registry->flags_.begin();
i != registry->flags_.end(); ++i) {
CommandLineFlagInfo fi;
// 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
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
string cmdline_string; // easier than doing strcats
for (int i = 0; i < argc; i++) {
if (i != 0) {
cmdline_string += " ";
cmdline_string += argv[i];
cmdline = strdup(cmdline_string.c_str()); // another small memory leak
// 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, '/');
if (!slash) slash = strrchr(argv0, '\\');
return slash ? slash + 1 : argv0;
void SetUsageMessage(const string& usage) {
if (program_usage != NULL)
ReportError(DIE, "ERROR: SetUsageMessage() called twice\n");
program_usage = strdup(usage.c_str()); // small memory leak
const char* ProgramUsage() {
if (program_usage) {
return program_usage;
return "Warning: SetUsageMessage() never called";
// --------------------------------------------------------------------
// SetVersionString()
// VersionString()
// --------------------------------------------------------------------
static const char* version_string = NULL;
void SetVersionString(const string& version) {
if (version_string != NULL)
ReportError(DIE, "ERROR: SetVersionString() called twice\n");
version_string = strdup(version.c_str()); // small memory leak
const char* VersionString() {
return version_string ? version_string : "";
// --------------------------------------------------------------------
// 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;
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 {
return true;
CommandLineFlagInfo GetCommandLineFlagInfoOrDie(const char* name) {
CommandLineFlagInfo info;
if (!GetCommandLineFlagInfo(name, &info)) {
fprintf(stderr, "FATAL ERROR: flag name '%s' doesn't exist\n", name);
gflags_exitfunc(1); // almost certainly gflags_exitfunc()
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
// Could consider logging this change
// 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 {
// 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_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(!)
FlagRegistry* const main_registry_;
vector<CommandLineFlag*> backup_registry_;
FlagSaverImpl(const FlagSaverImpl&); // no copying!
void operator=(const FlagSaverImpl&);
: impl_(new FlagSaverImpl(FlagRegistry::GlobalRegistry())) {
FlagSaver::~FlagSaver() {
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;
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;
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);
CommandLineFlagParser parser(registry);
parser.ProcessOptionsFromStringLocked(flagfilecontents, SET_FLAGS_VALUE);
// Should we handle --help and such when reading flags from a string? Sure.
if (parser.ReportErrors()) {
// Error. Restore all global flags to their previous values.
if (errors_are_fatal)
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;
// 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) {
fprintf(fp, "%s", TheseCommandlineFlagsIntoString(flags).c_str());
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.
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);
// 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
if (parser.ReportErrors()) // may cause us to exit on illegal flags
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;
void 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
ParseCommandLineNonHelpFlags(&tmp_argc, &tmp_argv, false);
for (int i = 0; i < tmp_argc; ++i)
delete[] tmp_argv;
void ShutDownCommandLineFlags() {