Remove rtc::Flag.

WebRTC has been migrated to Abseil Flags.

Bug: webrtc:10616
Change-Id: Id4a363429ccd2dd55c0dff00c9490c15124fdccc
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/144631
Reviewed-by: Steve Anton <steveanton@webrtc.org>
Commit-Queue: Mirko Bonadei <mbonadei@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#28620}
diff --git a/rtc_base/BUILD.gn b/rtc_base/BUILD.gn
index 220e575..713fb34 100644
--- a/rtc_base/BUILD.gn
+++ b/rtc_base/BUILD.gn
@@ -80,8 +80,6 @@
     "copy_on_write_buffer.h",
     "event_tracer.cc",
     "event_tracer.h",
-    "flags.cc",
-    "flags.h",
     "function_view.h",
     "ignore_wundef.h",
     "location.cc",
diff --git a/rtc_base/flags.cc b/rtc_base/flags.cc
deleted file mode 100644
index ca32c73..0000000
--- a/rtc_base/flags.cc
+++ /dev/null
@@ -1,282 +0,0 @@
-/*
- *  Copyright 2006 The WebRTC Project Authors. All rights reserved.
- *
- *  Use of this source code is governed by a BSD-style license
- *  that can be found in the LICENSE file in the root of the source
- *  tree. An additional intellectual property rights grant can be found
- *  in the file PATENTS.  All contributing project authors may
- *  be found in the AUTHORS file in the root of the source tree.
- */
-
-#include "rtc_base/flags.h"
-
-#include <stdio.h>
-#include <stdlib.h>
-#include <string.h>
-
-#include "rtc_base/checks.h"
-
-namespace {
-bool FlagEq(const char* arg, const char* flag) {
-  // Compare two flags for equality.
-  // 'arg' is the name of a flag passed via the command line and 'flag' is the
-  // name of a flag defined with the DEFINE_* macros.
-  // We compare the flags for equality, considering hyphens (-) and
-  // underscores (_) to be equivalent, so that --flag-name and --flag_name both
-  // match with --flag_name.
-  while (*arg != '\0' && (*arg == *flag || (*arg == '-' && *flag == '_'))) {
-    ++arg;
-    ++flag;
-  }
-  return *arg == '\0' && *flag == '\0';
-}
-}  // namespace
-
-namespace rtc {
-// -----------------------------------------------------------------------------
-// Implementation of Flag
-
-Flag::Flag(const char* file,
-           const char* name,
-           const char* comment,
-           Type type,
-           void* variable,
-           FlagValue default__)
-    : file_(file),
-      name_(name),
-      comment_(comment),
-      type_(type),
-      variable_(reinterpret_cast<FlagValue*>(variable)),
-      default_(default__) {
-  FlagList::Register(this);
-}
-
-void Flag::SetToDefault() {
-  // Note that we cannot simply do '*variable_ = default_;' since
-  // flag variables are not really of type FlagValue and thus may
-  // be smaller! The FlagValue union is simply 'overlayed' on top
-  // of a flag variable for convenient access. Since union members
-  // are guarantee to be aligned at the beginning, this works.
-  switch (type_) {
-    case Flag::BOOL:
-      variable_->b = default_.b;
-      return;
-    case Flag::INT:
-      variable_->i = default_.i;
-      return;
-    case Flag::FLOAT:
-      variable_->f = default_.f;
-      return;
-    case Flag::STRING:
-      variable_->s = default_.s;
-      return;
-  }
-  FATAL() << "unreachable code";
-}
-
-static const char* Type2String(Flag::Type type) {
-  switch (type) {
-    case Flag::BOOL:
-      return "bool";
-    case Flag::INT:
-      return "int";
-    case Flag::FLOAT:
-      return "float";
-    case Flag::STRING:
-      return "string";
-  }
-  FATAL() << "unreachable code";
-}
-
-static void PrintFlagValue(Flag::Type type, FlagValue* p) {
-  switch (type) {
-    case Flag::BOOL:
-      printf("%s", (p->b ? "true" : "false"));
-      return;
-    case Flag::INT:
-      printf("%d", p->i);
-      return;
-    case Flag::FLOAT:
-      printf("%f", p->f);
-      return;
-    case Flag::STRING:
-      printf("%s", p->s);
-      return;
-  }
-  FATAL() << "unreachable code";
-}
-
-void Flag::Print(bool print_current_value) {
-  printf("  --%s (%s)  type: %s  default: ", name_, comment_,
-         Type2String(type_));
-  PrintFlagValue(type_, &default_);
-  if (print_current_value) {
-    printf("  current value: ");
-    PrintFlagValue(type_, variable_);
-  }
-  printf("\n");
-}
-
-// -----------------------------------------------------------------------------
-// Implementation of FlagList
-
-Flag* FlagList::list_ = nullptr;
-
-FlagList::FlagList() {
-  list_ = nullptr;
-}
-
-void FlagList::Print(const char* file, bool print_current_value) {
-  // Since flag registration is likely by file (= C++ file),
-  // we don't need to sort by file and still get grouped output.
-  const char* current = nullptr;
-  for (Flag* f = list_; f != nullptr; f = f->next()) {
-    if (file == nullptr || file == f->file()) {
-      if (current != f->file()) {
-        printf("Flags from %s:\n", f->file());
-        current = f->file();
-      }
-      f->Print(print_current_value);
-    }
-  }
-}
-
-Flag* FlagList::Lookup(const char* name) {
-  Flag* f = list_;
-  while (f != nullptr && !FlagEq(name, f->name()))
-    f = f->next();
-  return f;
-}
-
-void FlagList::SplitArgument(const char* arg,
-                             char* buffer,
-                             int buffer_size,
-                             const char** name,
-                             const char** value,
-                             bool* is_bool) {
-  *name = nullptr;
-  *value = nullptr;
-  *is_bool = false;
-
-  if (*arg == '-') {
-    // find the begin of the flag name
-    arg++;  // remove 1st '-'
-    if (*arg == '-')
-      arg++;  // remove 2nd '-'
-    if (arg[0] == 'n' && arg[1] == 'o' && Lookup(arg + 2)) {
-      arg += 2;  // remove "no"
-      *is_bool = true;
-    }
-    *name = arg;
-
-    // find the end of the flag name
-    while (*arg != '\0' && *arg != '=')
-      arg++;
-
-    // get the value if any
-    if (*arg == '=') {
-      // make a copy so we can NUL-terminate flag name
-      int n = static_cast<int>(arg - *name);
-      RTC_CHECK_LT(n, buffer_size);
-      memcpy(buffer, *name, n * sizeof(char));
-      buffer[n] = '\0';
-      *name = buffer;
-      // get the value
-      *value = arg + 1;
-    }
-  }
-}
-
-int FlagList::SetFlagsFromCommandLine(int* argc,
-                                      const char** argv,
-                                      bool remove_flags) {
-  // parse arguments
-  for (int i = 1; i < *argc; /* see below */) {
-    int j = i;  // j > 0
-    const char* arg = argv[i++];
-
-    // split arg into flag components
-    char buffer[1024];
-    const char* name;
-    const char* value;
-    bool is_bool;
-    SplitArgument(arg, buffer, sizeof buffer, &name, &value, &is_bool);
-
-    if (name != nullptr) {
-      // lookup the flag
-      Flag* flag = Lookup(name);
-      if (flag == nullptr) {
-        fprintf(stderr, "Error: unrecognized flag %s\n", arg);
-        return j;
-      }
-
-      // if we still need a flag value, use the next argument if available
-      if (flag->type() != Flag::BOOL && value == nullptr) {
-        if (i < *argc) {
-          value = argv[i++];
-        } else {
-          fprintf(stderr, "Error: missing value for flag %s of type %s\n", arg,
-                  Type2String(flag->type()));
-          return j;
-        }
-      }
-
-      // set the flag
-      char empty[] = {'\0'};
-      char* endp = empty;
-      switch (flag->type()) {
-        case Flag::BOOL:
-          *flag->bool_variable() = !is_bool;
-          break;
-        case Flag::INT:
-          *flag->int_variable() = strtol(value, &endp, 10);
-          break;
-        case Flag::FLOAT:
-          *flag->float_variable() = strtod(value, &endp);
-          break;
-        case Flag::STRING:
-          *flag->string_variable() = value;
-          break;
-      }
-
-      // handle errors
-      if ((flag->type() == Flag::BOOL && value != nullptr) ||
-          (flag->type() != Flag::BOOL && is_bool) || *endp != '\0') {
-        fprintf(stderr, "Error: illegal value for flag %s of type %s\n", arg,
-                Type2String(flag->type()));
-        return j;
-      }
-
-      // remove the flag & value from the command
-      if (remove_flags)
-        while (j < i)
-          argv[j++] = nullptr;
-    }
-  }
-
-  // shrink the argument list
-  if (remove_flags) {
-    int j = 1;
-    for (int i = 1; i < *argc; i++) {
-      if (argv[i] != nullptr)
-        argv[j++] = argv[i];
-    }
-    *argc = j;
-  }
-
-  // parsed all flags successfully
-  return 0;
-}
-
-void FlagList::Register(Flag* flag) {
-  RTC_DCHECK(flag);
-  RTC_DCHECK_GT(strlen(flag->name()), 0);
-  // NOTE: Don't call Lookup() within Register because it accesses the name_
-  // of other flags in list_, and if the flags are coming from two different
-  // compilation units, the initialization order between them is undefined, and
-  // this will trigger an asan initialization-order-fiasco error.
-  flag->next_ = list_;
-  list_ = flag;
-}
-
-}  // namespace rtc
diff --git a/rtc_base/flags.h b/rtc_base/flags.h
deleted file mode 100644
index 61a95ff..0000000
--- a/rtc_base/flags.h
+++ /dev/null
@@ -1,244 +0,0 @@
-/*
- *  Copyright 2006 The WebRTC Project Authors. All rights reserved.
- *
- *  Use of this source code is governed by a BSD-style license
- *  that can be found in the LICENSE file in the root of the source
- *  tree. An additional intellectual property rights grant can be found
- *  in the file PATENTS.  All contributing project authors may
- *  be found in the AUTHORS file in the root of the source tree.
- */
-
-// Originally comes from shared/commandlineflags/flags.h
-
-// Flags are defined and declared using DEFINE_xxx and DECLARE_xxx macros,
-// where xxx is the flag type. Flags are referred to via FLAG_yyy,
-// where yyy is the flag name. For intialization and iteration of flags,
-// see the FlagList class. For full programmatic access to any
-// flag, see the Flag class.
-//
-// The implementation only relies and basic C++ functionality
-// and needs no special library or STL support.
-
-#ifndef RTC_BASE_FLAGS_H_
-#define RTC_BASE_FLAGS_H_
-
-#include "rtc_base/checks.h"
-
-namespace rtc {
-
-// Internal use only.
-union FlagValue {
-  // Note: Because in C++ non-bool values are silently converted into
-  // bool values ('bool b = "false";' results in b == true!), we pass
-  // and int argument to New_BOOL as this appears to be safer - sigh.
-  // In particular, it prevents the (not uncommon!) bug where a bool
-  // flag is defined via: WEBRTC_DEFINE_bool(flag, "false", "some comment");.
-  static FlagValue New_BOOL(int b) {
-    FlagValue v;
-    v.b = (b != 0);
-    return v;
-  }
-
-  static FlagValue New_INT(int i) {
-    FlagValue v;
-    v.i = i;
-    return v;
-  }
-
-  static FlagValue New_FLOAT(float f) {
-    FlagValue v;
-    v.f = f;
-    return v;
-  }
-
-  static FlagValue New_STRING(const char* s) {
-    FlagValue v;
-    v.s = s;
-    return v;
-  }
-
-  bool b;
-  int i;
-  double f;
-  const char* s;
-};
-
-// Each flag can be accessed programmatically via a Flag object.
-class Flag {
- public:
-  enum Type { BOOL, INT, FLOAT, STRING };
-
-  // Internal use only.
-  Flag(const char* file,
-       const char* name,
-       const char* comment,
-       Type type,
-       void* variable,
-       FlagValue default_);
-
-  // General flag information
-  const char* file() const { return file_; }
-  const char* name() const { return name_; }
-  const char* comment() const { return comment_; }
-
-  // Flag type
-  Type type() const { return type_; }
-
-  // Flag variables
-  bool* bool_variable() const {
-    RTC_DCHECK_EQ(BOOL, type_);
-    return &variable_->b;
-  }
-
-  int* int_variable() const {
-    RTC_DCHECK_EQ(INT, type_);
-    return &variable_->i;
-  }
-
-  double* float_variable() const {
-    RTC_DCHECK_EQ(FLOAT, type_);
-    return &variable_->f;
-  }
-
-  const char** string_variable() const {
-    RTC_DCHECK_EQ(STRING, type_);
-    return &variable_->s;
-  }
-
-  // Default values
-  bool bool_default() const {
-    RTC_DCHECK_EQ(BOOL, type_);
-    return default_.b;
-  }
-
-  int int_default() const {
-    RTC_DCHECK_EQ(INT, type_);
-    return default_.i;
-  }
-
-  double float_default() const {
-    RTC_DCHECK_EQ(FLOAT, type_);
-    return default_.f;
-  }
-
-  const char* string_default() const {
-    RTC_DCHECK_EQ(STRING, type_);
-    return default_.s;
-  }
-
-  // Resets a flag to its default value
-  void SetToDefault();
-
-  // Iteration support
-  Flag* next() const { return next_; }
-
-  // Prints flag information. The current flag value is only printed
-  // if print_current_value is set.
-  void Print(bool print_current_value);
-
- private:
-  const char* file_;
-  const char* name_;
-  const char* comment_;
-
-  Type type_;
-  FlagValue* variable_;
-  FlagValue default_;
-
-  Flag* next_;
-
-  friend class FlagList;  // accesses next_
-};
-
-// Internal use only.
-#define WEBRTC_DEFINE_FLAG(type, c_type, name, default, comment)            \
-  /* define and initialize the flag */                                      \
-  c_type FLAG_##name = (default);                                           \
-  /* register the flag */                                                   \
-  static rtc::Flag Flag_##name(__FILE__, #name, (comment), rtc::Flag::type, \
-                               &FLAG_##name,                                \
-                               rtc::FlagValue::New_##type(default))
-
-// Internal use only.
-#define WEBRTC_DECLARE_FLAG(c_type, name) \
-  /* declare the external flag */         \
-  extern c_type FLAG_##name
-
-// Use the following macros to define a new flag:
-#define WEBRTC_DEFINE_bool(name, default, comment) \
-  WEBRTC_DEFINE_FLAG(BOOL, bool, name, default, comment)
-#define WEBRTC_DEFINE_int(name, default, comment) \
-  WEBRTC_DEFINE_FLAG(INT, int, name, default, comment)
-#define WEBRTC_DEFINE_float(name, default, comment) \
-  WEBRTC_DEFINE_FLAG(FLOAT, double, name, default, comment)
-#define WEBRTC_DEFINE_string(name, default, comment) \
-  WEBRTC_DEFINE_FLAG(STRING, const char*, name, default, comment)
-
-// Use the following macros to declare a flag defined elsewhere:
-#define WEBRTC_DECLARE_bool(name) WEBRTC_DECLARE_FLAG(bool, name)
-#define WEBRTC_DECLARE_int(name) WEBRTC_DECLARE_FLAG(int, name)
-#define WEBRTC_DECLARE_float(name) WEBRTC_DECLARE_FLAG(double, name)
-#define WEBRTC_DECLARE_string(name) WEBRTC_DECLARE_FLAG(const char*, name)
-
-// The global list of all flags.
-class FlagList {
- public:
-  FlagList();
-
-  // The null-terminated list of all flags. Traverse with Flag::next().
-  static Flag* list() { return list_; }
-
-  // If file != nullptr, prints information for all flags defined in file;
-  // otherwise prints information for all flags in all files. The current flag
-  // value is only printed if print_current_value is set.
-  static void Print(const char* file, bool print_current_value);
-
-  // Lookup a flag by name. Returns the matching flag or null.
-  static Flag* Lookup(const char* name);
-
-  // Helper function to parse flags: Takes an argument arg and splits it into
-  // a flag name and flag value (or null if they are missing). is_bool is set
-  // if the arg started with "-no" or "--no". The buffer may be used to NUL-
-  // terminate the name, it must be large enough to hold any possible name.
-  static void SplitArgument(const char* arg,
-                            char* buffer,
-                            int buffer_size,
-                            const char** name,
-                            const char** value,
-                            bool* is_bool);
-
-  // Set the flag values by parsing the command line. If remove_flags
-  // is set, the flags and associated values are removed from (argc,
-  // argv). Returns 0 if no error occurred. Otherwise, returns the
-  // argv index > 0 for the argument where an error occurred. In that
-  // case, (argc, argv) will remain unchanged indepdendent of the
-  // remove_flags value, and no assumptions about flag settings should
-  // be made.
-  //
-  // The following syntax for flags is accepted (both '-' and '--' are ok):
-  //
-  //   --flag        (bool flags only)
-  //   --noflag      (bool flags only)
-  //   --flag=value  (non-bool flags only, no spaces around '=')
-  //   --flag value  (non-bool flags only)
-  static int SetFlagsFromCommandLine(int* argc,
-                                     const char** argv,
-                                     bool remove_flags);
-  static inline int SetFlagsFromCommandLine(int* argc,
-                                            char** argv,
-                                            bool remove_flags) {
-    return SetFlagsFromCommandLine(argc, const_cast<const char**>(argv),
-                                   remove_flags);
-  }
-
-  // Registers a new flag. Called during program initialization. Not
-  // thread-safe.
-  static void Register(Flag* flag);
-
- private:
-  static Flag* list_;
-};
-
-}  // namespace rtc
-
-#endif  // SHARED_COMMANDLINEFLAGS_FLAGS_H_