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352 lines
11 KiB
352 lines
11 KiB
//
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// Copyright 2019 The Abseil Authors.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// https://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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#include "absl/flags/internal/registry.h"
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#include <assert.h>
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#include <stdlib.h>
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#include <functional>
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#include <map>
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#include <memory>
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#include <string>
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#include <utility>
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#include <vector>
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#include "absl/base/config.h"
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#include "absl/base/internal/raw_logging.h"
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#include "absl/base/thread_annotations.h"
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#include "absl/flags/internal/commandlineflag.h"
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#include "absl/flags/usage_config.h"
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#include "absl/strings/str_cat.h"
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#include "absl/strings/string_view.h"
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#include "absl/synchronization/mutex.h"
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// --------------------------------------------------------------------
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// FlagRegistry implementation
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// A FlagRegistry holds all flag objects indexed
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// by their names so that if you know a flag's name you can access or
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// set it.
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namespace absl {
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ABSL_NAMESPACE_BEGIN
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namespace flags_internal {
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// --------------------------------------------------------------------
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// FlagRegistry
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// A FlagRegistry singleton object holds all flag objects indexed
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// by their names so that if you know a flag's name (as a C
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// string), you can access or set it. If the function is named
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// FooLocked(), you must own the registry lock before calling
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// the function; otherwise, you should *not* hold the lock, and
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// the function will acquire it itself if needed.
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// --------------------------------------------------------------------
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class FlagRegistry {
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public:
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FlagRegistry() = default;
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~FlagRegistry() = default;
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// Store a flag in this registry. Takes ownership of *flag.
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void RegisterFlag(CommandLineFlag* flag);
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void Lock() ABSL_EXCLUSIVE_LOCK_FUNCTION(lock_) { lock_.Lock(); }
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void Unlock() ABSL_UNLOCK_FUNCTION(lock_) { lock_.Unlock(); }
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// Returns the flag object for the specified name, or nullptr if not found.
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// Will emit a warning if a 'retired' flag is specified.
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CommandLineFlag* FindFlagLocked(absl::string_view name);
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// Returns the retired flag object for the specified name, or nullptr if not
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// found or not retired. Does not emit a warning.
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CommandLineFlag* FindRetiredFlagLocked(absl::string_view name);
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static FlagRegistry* GlobalRegistry(); // returns a singleton registry
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private:
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friend class FlagSaverImpl; // reads all the flags in order to copy them
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friend void ForEachFlagUnlocked(
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std::function<void(CommandLineFlag*)> visitor);
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// The map from name to flag, for FindFlagLocked().
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using FlagMap = std::map<absl::string_view, CommandLineFlag*>;
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using FlagIterator = FlagMap::iterator;
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using FlagConstIterator = FlagMap::const_iterator;
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FlagMap flags_;
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absl::Mutex lock_;
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// Disallow
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FlagRegistry(const FlagRegistry&);
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FlagRegistry& operator=(const FlagRegistry&);
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};
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FlagRegistry* FlagRegistry::GlobalRegistry() {
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static FlagRegistry* global_registry = new FlagRegistry;
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return global_registry;
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}
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namespace {
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class FlagRegistryLock {
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public:
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explicit FlagRegistryLock(FlagRegistry* fr) : fr_(fr) { fr_->Lock(); }
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~FlagRegistryLock() { fr_->Unlock(); }
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private:
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FlagRegistry* const fr_;
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};
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void DestroyRetiredFlag(CommandLineFlag* flag);
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} // namespace
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void FlagRegistry::RegisterFlag(CommandLineFlag* flag) {
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FlagRegistryLock registry_lock(this);
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std::pair<FlagIterator, bool> ins =
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flags_.insert(FlagMap::value_type(flag->Name(), flag));
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if (ins.second == false) { // means the name was already in the map
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CommandLineFlag* old_flag = ins.first->second;
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if (flag->IsRetired() != old_flag->IsRetired()) {
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// All registrations must agree on the 'retired' flag.
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flags_internal::ReportUsageError(
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absl::StrCat(
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"Retired flag '", flag->Name(),
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"' was defined normally in file '",
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(flag->IsRetired() ? old_flag->Filename() : flag->Filename()),
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"'."),
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true);
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} else if (flag->TypeId() != old_flag->TypeId()) {
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flags_internal::ReportUsageError(
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absl::StrCat("Flag '", flag->Name(),
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"' was defined more than once but with "
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"differing types. Defined in files '",
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old_flag->Filename(), "' and '", flag->Filename(),
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"' with types '", old_flag->Typename(), "' and '",
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flag->Typename(), "', respectively."),
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true);
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} else if (old_flag->IsRetired()) {
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// Retired flag can just be deleted.
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DestroyRetiredFlag(flag);
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return;
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} else if (old_flag->Filename() != flag->Filename()) {
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flags_internal::ReportUsageError(
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absl::StrCat("Flag '", flag->Name(),
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"' was defined more than once (in files '",
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old_flag->Filename(), "' and '", flag->Filename(),
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"')."),
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true);
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} else {
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flags_internal::ReportUsageError(
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absl::StrCat(
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"Something wrong with flag '", flag->Name(), "' in file '",
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flag->Filename(), "'. One possibility: file '", flag->Filename(),
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"' is being linked both statically and dynamically into this "
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"executable. e.g. some files listed as srcs to a test and also "
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"listed as srcs of some shared lib deps of the same test."),
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true);
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}
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// All cases above are fatal, except for the retired flags.
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std::exit(1);
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}
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}
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CommandLineFlag* FlagRegistry::FindFlagLocked(absl::string_view name) {
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FlagConstIterator i = flags_.find(name);
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if (i == flags_.end()) {
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return nullptr;
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}
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if (i->second->IsRetired()) {
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flags_internal::ReportUsageError(
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absl::StrCat("Accessing retired flag '", name, "'"), false);
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}
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return i->second;
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}
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CommandLineFlag* FlagRegistry::FindRetiredFlagLocked(absl::string_view name) {
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FlagConstIterator i = flags_.find(name);
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if (i == flags_.end() || !i->second->IsRetired()) {
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return nullptr;
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}
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return i->second;
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}
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// --------------------------------------------------------------------
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// FlagSaver
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// FlagSaverImpl
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// This class stores the states of all flags at construct time,
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// and restores all flags to that state at destruct time.
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// Its major implementation challenge is that it never modifies
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// pointers in the 'main' registry, so global FLAG_* vars always
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// point to the right place.
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// --------------------------------------------------------------------
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class FlagSaverImpl {
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public:
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FlagSaverImpl() = default;
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FlagSaverImpl(const FlagSaverImpl&) = delete;
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void operator=(const FlagSaverImpl&) = delete;
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// Saves the flag states from the flag registry into this object.
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// It's an error to call this more than once.
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void SaveFromRegistry() {
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assert(backup_registry_.empty()); // call only once!
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flags_internal::ForEachFlag([&](flags_internal::CommandLineFlag* flag) {
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if (auto flag_state = flag->SaveState()) {
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backup_registry_.emplace_back(std::move(flag_state));
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}
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});
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}
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// Restores the saved flag states into the flag registry.
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void RestoreToRegistry() {
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for (const auto& flag_state : backup_registry_) {
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flag_state->Restore();
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}
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}
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private:
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std::vector<std::unique_ptr<flags_internal::FlagStateInterface>>
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backup_registry_;
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};
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FlagSaver::FlagSaver() : impl_(new FlagSaverImpl) { impl_->SaveFromRegistry(); }
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void FlagSaver::Ignore() {
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delete impl_;
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impl_ = nullptr;
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}
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FlagSaver::~FlagSaver() {
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if (!impl_) return;
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impl_->RestoreToRegistry();
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delete impl_;
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}
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// --------------------------------------------------------------------
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CommandLineFlag* FindCommandLineFlag(absl::string_view name) {
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if (name.empty()) return nullptr;
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FlagRegistry* const registry = FlagRegistry::GlobalRegistry();
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FlagRegistryLock frl(registry);
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return registry->FindFlagLocked(name);
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}
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CommandLineFlag* FindRetiredFlag(absl::string_view name) {
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FlagRegistry* const registry = FlagRegistry::GlobalRegistry();
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FlagRegistryLock frl(registry);
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return registry->FindRetiredFlagLocked(name);
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}
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// --------------------------------------------------------------------
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void ForEachFlagUnlocked(std::function<void(CommandLineFlag*)> visitor) {
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FlagRegistry* const registry = FlagRegistry::GlobalRegistry();
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for (FlagRegistry::FlagConstIterator i = registry->flags_.begin();
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i != registry->flags_.end(); ++i) {
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visitor(i->second);
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}
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}
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void ForEachFlag(std::function<void(CommandLineFlag*)> visitor) {
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FlagRegistry* const registry = FlagRegistry::GlobalRegistry();
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FlagRegistryLock frl(registry);
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ForEachFlagUnlocked(visitor);
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}
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// --------------------------------------------------------------------
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bool RegisterCommandLineFlag(CommandLineFlag* flag) {
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FlagRegistry::GlobalRegistry()->RegisterFlag(flag);
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return true;
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}
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// --------------------------------------------------------------------
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namespace {
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class RetiredFlagObj final : public flags_internal::CommandLineFlag {
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public:
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constexpr RetiredFlagObj(const char* name, FlagStaticTypeId type_id)
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: name_(name), type_id_(type_id) {}
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private:
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absl::string_view Name() const override { return name_; }
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std::string Filename() const override { return "RETIRED"; }
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absl::string_view Typename() const override { return ""; }
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FlagStaticTypeId TypeId() const override { return type_id_; }
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std::string Help() const override { return ""; }
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bool IsRetired() const override { return true; }
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bool IsModified() const override { return false; }
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bool IsSpecifiedOnCommandLine() const override { return false; }
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std::string DefaultValue() const override { return ""; }
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std::string CurrentValue() const override { return ""; }
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// Any input is valid
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bool ValidateInputValue(absl::string_view) const override { return true; }
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std::unique_ptr<flags_internal::FlagStateInterface> SaveState() override {
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return nullptr;
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}
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bool SetFromString(absl::string_view, flags_internal::FlagSettingMode,
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flags_internal::ValueSource, std::string*) override {
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return false;
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}
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void CheckDefaultValueParsingRoundtrip() const override {}
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void Read(void*) const override {}
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// Data members
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const char* const name_;
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const FlagStaticTypeId type_id_;
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};
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void DestroyRetiredFlag(flags_internal::CommandLineFlag* flag) {
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assert(flag->IsRetired());
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delete static_cast<RetiredFlagObj*>(flag);
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}
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} // namespace
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bool Retire(const char* name, FlagStaticTypeId type_id) {
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auto* flag = new flags_internal::RetiredFlagObj(name, type_id);
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FlagRegistry::GlobalRegistry()->RegisterFlag(flag);
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return true;
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}
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// --------------------------------------------------------------------
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bool IsRetiredFlag(absl::string_view name, bool* type_is_bool) {
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assert(!name.empty());
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CommandLineFlag* flag = flags_internal::FindRetiredFlag(name);
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if (flag == nullptr) {
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return false;
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}
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assert(type_is_bool);
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*type_is_bool = flag->IsOfType<bool>();
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return true;
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}
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} // namespace flags_internal
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ABSL_NAMESPACE_END
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} // namespace absl
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