diff options
Diffstat (limited to 'third_party/abseil-cpp/absl/flags/reflection.cc')
| -rw-r--r-- | third_party/abseil-cpp/absl/flags/reflection.cc | 354 |
1 files changed, 354 insertions, 0 deletions
diff --git a/third_party/abseil-cpp/absl/flags/reflection.cc b/third_party/abseil-cpp/absl/flags/reflection.cc new file mode 100644 index 0000000000..dbce4032ab --- /dev/null +++ b/third_party/abseil-cpp/absl/flags/reflection.cc @@ -0,0 +1,354 @@ +// +// Copyright 2020 The Abseil Authors. +// +// Licensed under the Apache License, Version 2.0 (the "License"); +// you may not use this file except in compliance with the License. +// You may obtain a copy of the License at +// +// https://www.apache.org/licenses/LICENSE-2.0 +// +// Unless required by applicable law or agreed to in writing, software +// distributed under the License is distributed on an "AS IS" BASIS, +// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. +// See the License for the specific language governing permissions and +// limitations under the License. + +#include "absl/flags/reflection.h" + +#include <assert.h> + +#include <atomic> +#include <string> + +#include "absl/base/config.h" +#include "absl/base/thread_annotations.h" +#include "absl/container/flat_hash_map.h" +#include "absl/flags/commandlineflag.h" +#include "absl/flags/internal/private_handle_accessor.h" +#include "absl/flags/internal/registry.h" +#include "absl/flags/usage_config.h" +#include "absl/strings/str_cat.h" +#include "absl/strings/string_view.h" +#include "absl/synchronization/mutex.h" + +namespace absl { +ABSL_NAMESPACE_BEGIN +namespace flags_internal { + +// -------------------------------------------------------------------- +// FlagRegistry +// A FlagRegistry singleton object holds all flag objects indexed by their +// names so that if you know a flag's name, 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. +// -------------------------------------------------------------------- + +class FlagRegistry { + public: + FlagRegistry() = default; + ~FlagRegistry() = default; + + // Store a flag in this registry. Takes ownership of *flag. + void RegisterFlag(CommandLineFlag& flag, const char* filename); + + void Lock() ABSL_EXCLUSIVE_LOCK_FUNCTION(lock_) { lock_.Lock(); } + void Unlock() ABSL_UNLOCK_FUNCTION(lock_) { lock_.Unlock(); } + + // Returns the flag object for the specified name, or nullptr if not found. + // Will emit a warning if a 'retired' flag is specified. + CommandLineFlag* FindFlag(absl::string_view name); + + static FlagRegistry& GlobalRegistry(); // returns a singleton registry + + private: + friend class flags_internal::FlagSaverImpl; // reads all the flags in order + // to copy them + friend void ForEachFlag(std::function<void(CommandLineFlag&)> visitor); + friend void FinalizeRegistry(); + + // The map from name to flag, for FindFlag(). + using FlagMap = absl::flat_hash_map<absl::string_view, CommandLineFlag*>; + using FlagIterator = FlagMap::iterator; + using FlagConstIterator = FlagMap::const_iterator; + FlagMap flags_; + std::vector<CommandLineFlag*> flat_flags_; + std::atomic<bool> finalized_flags_{false}; + + absl::Mutex lock_; + + // Disallow + FlagRegistry(const FlagRegistry&); + FlagRegistry& operator=(const FlagRegistry&); +}; + +namespace { + +class FlagRegistryLock { + public: + explicit FlagRegistryLock(FlagRegistry& fr) : fr_(fr) { fr_.Lock(); } + ~FlagRegistryLock() { fr_.Unlock(); } + + private: + FlagRegistry& fr_; +}; + +} // namespace + +CommandLineFlag* FlagRegistry::FindFlag(absl::string_view name) { + if (finalized_flags_.load(std::memory_order_acquire)) { + // We could save some gcus here if we make `Name()` be non-virtual. + // We could move the `const char*` name to the base class. + auto it = std::partition_point( + flat_flags_.begin(), flat_flags_.end(), + [=](CommandLineFlag* f) { return f->Name() < name; }); + if (it != flat_flags_.end() && (*it)->Name() == name) return *it; + } + + FlagRegistryLock frl(*this); + auto it = flags_.find(name); + return it != flags_.end() ? it->second : nullptr; +} + +void FlagRegistry::RegisterFlag(CommandLineFlag& flag, const char* filename) { + if (filename != nullptr && + flag.Filename() != GetUsageConfig().normalize_filename(filename)) { + flags_internal::ReportUsageError( + absl::StrCat( + "Inconsistency between flag object and registration for flag '", + flag.Name(), + "', likely due to duplicate flags or an ODR violation. Relevant " + "files: ", + flag.Filename(), " and ", filename), + true); + std::exit(1); + } + + FlagRegistryLock registry_lock(*this); + + std::pair<FlagIterator, bool> ins = + flags_.insert(FlagMap::value_type(flag.Name(), &flag)); + if (ins.second == false) { // means the name was already in the map + CommandLineFlag& old_flag = *ins.first->second; + if (flag.IsRetired() != old_flag.IsRetired()) { + // All registrations must agree on the 'retired' flag. + flags_internal::ReportUsageError( + absl::StrCat( + "Retired flag '", flag.Name(), "' was defined normally in file '", + (flag.IsRetired() ? old_flag.Filename() : flag.Filename()), "'."), + true); + } else if (flags_internal::PrivateHandleAccessor::TypeId(flag) != + flags_internal::PrivateHandleAccessor::TypeId(old_flag)) { + flags_internal::ReportUsageError( + absl::StrCat("Flag '", flag.Name(), + "' was defined more than once but with " + "differing types. Defined in files '", + old_flag.Filename(), "' and '", flag.Filename(), "'."), + true); + } else if (old_flag.IsRetired()) { + return; + } else if (old_flag.Filename() != flag.Filename()) { + flags_internal::ReportUsageError( + absl::StrCat("Flag '", flag.Name(), + "' was defined more than once (in files '", + old_flag.Filename(), "' and '", flag.Filename(), "')."), + true); + } else { + flags_internal::ReportUsageError( + absl::StrCat( + "Something is wrong with flag '", flag.Name(), "' in file '", + flag.Filename(), "'. One possibility: file '", flag.Filename(), + "' is being linked both statically and dynamically into this " + "executable. e.g. some files listed as srcs to a test and also " + "listed as srcs of some shared lib deps of the same test."), + true); + } + // All cases above are fatal, except for the retired flags. + std::exit(1); + } +} + +FlagRegistry& FlagRegistry::GlobalRegistry() { + static FlagRegistry* global_registry = new FlagRegistry; + return *global_registry; +} + +// -------------------------------------------------------------------- + +void ForEachFlag(std::function<void(CommandLineFlag&)> visitor) { + FlagRegistry& registry = FlagRegistry::GlobalRegistry(); + + if (registry.finalized_flags_.load(std::memory_order_acquire)) { + for (const auto& i : registry.flat_flags_) visitor(*i); + } + + FlagRegistryLock frl(registry); + for (const auto& i : registry.flags_) visitor(*i.second); +} + +// -------------------------------------------------------------------- + +bool RegisterCommandLineFlag(CommandLineFlag& flag, const char* filename) { + FlagRegistry::GlobalRegistry().RegisterFlag(flag, filename); + return true; +} + +void FinalizeRegistry() { + auto& registry = FlagRegistry::GlobalRegistry(); + FlagRegistryLock frl(registry); + if (registry.finalized_flags_.load(std::memory_order_relaxed)) { + // Was already finalized. Ignore the second time. + return; + } + registry.flat_flags_.reserve(registry.flags_.size()); + for (const auto& f : registry.flags_) { + registry.flat_flags_.push_back(f.second); + } + std::sort(std::begin(registry.flat_flags_), std::end(registry.flat_flags_), + [](const CommandLineFlag* lhs, const CommandLineFlag* rhs) { + return lhs->Name() < rhs->Name(); + }); + registry.flags_.clear(); + registry.finalized_flags_.store(true, std::memory_order_release); +} + +// -------------------------------------------------------------------- + +namespace { + +class RetiredFlagObj final : public CommandLineFlag { + public: + constexpr RetiredFlagObj(const char* name, FlagFastTypeId type_id) + : name_(name), type_id_(type_id) {} + + private: + absl::string_view Name() const override { return name_; } + std::string Filename() const override { + OnAccess(); + return "RETIRED"; + } + FlagFastTypeId TypeId() const override { return type_id_; } + std::string Help() const override { + OnAccess(); + return ""; + } + bool IsRetired() const override { return true; } + bool IsSpecifiedOnCommandLine() const override { + OnAccess(); + return false; + } + std::string DefaultValue() const override { + OnAccess(); + return ""; + } + std::string CurrentValue() const override { + OnAccess(); + return ""; + } + + // Any input is valid + bool ValidateInputValue(absl::string_view) const override { + OnAccess(); + return true; + } + + std::unique_ptr<flags_internal::FlagStateInterface> SaveState() override { + return nullptr; + } + + bool ParseFrom(absl::string_view, flags_internal::FlagSettingMode, + flags_internal::ValueSource, std::string&) override { + OnAccess(); + return false; + } + + void CheckDefaultValueParsingRoundtrip() const override { OnAccess(); } + + void Read(void*) const override { OnAccess(); } + + void OnAccess() const { + flags_internal::ReportUsageError( + absl::StrCat("Accessing retired flag '", name_, "'"), false); + } + + // Data members + const char* const name_; + const FlagFastTypeId type_id_; +}; + +} // namespace + +void Retire(const char* name, FlagFastTypeId type_id, char* buf) { + static_assert(sizeof(RetiredFlagObj) == kRetiredFlagObjSize, ""); + static_assert(alignof(RetiredFlagObj) == kRetiredFlagObjAlignment, ""); + auto* flag = ::new (static_cast<void*>(buf)) + flags_internal::RetiredFlagObj(name, type_id); + FlagRegistry::GlobalRegistry().RegisterFlag(*flag, nullptr); +} + +// -------------------------------------------------------------------- + +class FlagSaverImpl { + public: + FlagSaverImpl() = default; + FlagSaverImpl(const FlagSaverImpl&) = delete; + void operator=(const FlagSaverImpl&) = delete; + + // Saves the flag states from the flag registry into this object. + // It's an error to call this more than once. + void SaveFromRegistry() { + assert(backup_registry_.empty()); // call only once! + flags_internal::ForEachFlag([&](CommandLineFlag& flag) { + if (auto flag_state = + flags_internal::PrivateHandleAccessor::SaveState(flag)) { + backup_registry_.emplace_back(std::move(flag_state)); + } + }); + } + + // Restores the saved flag states into the flag registry. + void RestoreToRegistry() { + for (const auto& flag_state : backup_registry_) { + flag_state->Restore(); + } + } + + private: + std::vector<std::unique_ptr<flags_internal::FlagStateInterface>> + backup_registry_; +}; + +} // namespace flags_internal + +FlagSaver::FlagSaver() : impl_(new flags_internal::FlagSaverImpl) { + impl_->SaveFromRegistry(); +} + +FlagSaver::~FlagSaver() { + if (!impl_) return; + + impl_->RestoreToRegistry(); + delete impl_; +} + +// -------------------------------------------------------------------- + +CommandLineFlag* FindCommandLineFlag(absl::string_view name) { + if (name.empty()) return nullptr; + flags_internal::FlagRegistry& registry = + flags_internal::FlagRegistry::GlobalRegistry(); + return registry.FindFlag(name); +} + +// -------------------------------------------------------------------- + +absl::flat_hash_map<absl::string_view, absl::CommandLineFlag*> GetAllFlags() { + absl::flat_hash_map<absl::string_view, absl::CommandLineFlag*> res; + flags_internal::ForEachFlag([&](CommandLineFlag& flag) { + if (!flag.IsRetired()) res.insert({flag.Name(), &flag}); + }); + return res; +} + +ABSL_NAMESPACE_END +} // namespace absl |