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Diffstat (limited to 'third_party/abseil_cpp/absl/flags/internal/registry.h')
-rw-r--r-- | third_party/abseil_cpp/absl/flags/internal/registry.h | 97 |
1 files changed, 97 insertions, 0 deletions
diff --git a/third_party/abseil_cpp/absl/flags/internal/registry.h b/third_party/abseil_cpp/absl/flags/internal/registry.h new file mode 100644 index 000000000000..a8d9eb9cb0bb --- /dev/null +++ b/third_party/abseil_cpp/absl/flags/internal/registry.h @@ -0,0 +1,97 @@ +// +// Copyright 2019 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. + +#ifndef ABSL_FLAGS_INTERNAL_REGISTRY_H_ +#define ABSL_FLAGS_INTERNAL_REGISTRY_H_ + +#include <functional> + +#include "absl/base/config.h" +#include "absl/flags/commandlineflag.h" +#include "absl/flags/internal/commandlineflag.h" +#include "absl/strings/string_view.h" + +// -------------------------------------------------------------------- +// Global flags registry API. + +namespace absl { +ABSL_NAMESPACE_BEGIN +namespace flags_internal { + +// Executes specified visitor for each non-retired flag in the registry. While +// callback are executed, the registry is locked and can't be changed. +void ForEachFlag(std::function<void(CommandLineFlag&)> visitor); + +//----------------------------------------------------------------------------- + +bool RegisterCommandLineFlag(CommandLineFlag&); + +void FinalizeRegistry(); + +//----------------------------------------------------------------------------- +// Retired registrations: +// +// Retired flag registrations are treated specially. A 'retired' flag is +// provided only for compatibility with automated invocations that still +// name it. A 'retired' flag: +// - is not bound to a C++ FLAGS_ reference. +// - has a type and a value, but that value is intentionally inaccessible. +// - does not appear in --help messages. +// - is fully supported by _all_ flag parsing routines. +// - consumes args normally, and complains about type mismatches in its +// argument. +// - emits a complaint but does not die (e.g. LOG(ERROR)) if it is +// accessed by name through the flags API for parsing or otherwise. +// +// The registrations for a flag happen in an unspecified order as the +// initializers for the namespace-scope objects of a program are run. +// Any number of weak registrations for a flag can weakly define the flag. +// One non-weak registration will upgrade the flag from weak to non-weak. +// Further weak registrations of a non-weak flag are ignored. +// +// This mechanism is designed to support moving dead flags into a +// 'graveyard' library. An example migration: +// +// 0: Remove references to this FLAGS_flagname in the C++ codebase. +// 1: Register as 'retired' in old_lib. +// 2: Make old_lib depend on graveyard. +// 3: Add a redundant 'retired' registration to graveyard. +// 4: Remove the old_lib 'retired' registration. +// 5: Eventually delete the graveyard registration entirely. +// + +// Retire flag with name "name" and type indicated by ops. +void Retire(const char* name, FlagFastTypeId type_id, char* buf); + +constexpr size_t kRetiredFlagObjSize = 3 * sizeof(void*); +constexpr size_t kRetiredFlagObjAlignment = alignof(void*); + +// Registered a retired flag with name 'flag_name' and type 'T'. +template <typename T> +class RetiredFlag { + public: + void Retire(const char* flag_name) { + flags_internal::Retire(flag_name, base_internal::FastTypeId<T>(), buf_); + } + + private: + alignas(kRetiredFlagObjAlignment) char buf_[kRetiredFlagObjSize]; +}; + +} // namespace flags_internal +ABSL_NAMESPACE_END +} // namespace absl + +#endif // ABSL_FLAGS_INTERNAL_REGISTRY_H_ |