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Diffstat (limited to 'third_party/abseil_cpp/absl/base/const_init.h')
| -rw-r--r-- | third_party/abseil_cpp/absl/base/const_init.h | 76 |
1 files changed, 0 insertions, 76 deletions
diff --git a/third_party/abseil_cpp/absl/base/const_init.h b/third_party/abseil_cpp/absl/base/const_init.h deleted file mode 100644 index 16520b61d9..0000000000 --- a/third_party/abseil_cpp/absl/base/const_init.h +++ /dev/null @@ -1,76 +0,0 @@ -// Copyright 2017 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. -// -// ----------------------------------------------------------------------------- -// kConstInit -// ----------------------------------------------------------------------------- -// -// A constructor tag used to mark an object as safe for use as a global -// variable, avoiding the usual lifetime issues that can affect globals. - -#ifndef ABSL_BASE_CONST_INIT_H_ -#define ABSL_BASE_CONST_INIT_H_ - -#include "absl/base/config.h" - -// In general, objects with static storage duration (such as global variables) -// can trigger tricky object lifetime situations. Attempting to access them -// from the constructors or destructors of other global objects can result in -// undefined behavior, unless their constructors and destructors are designed -// with this issue in mind. -// -// The normal way to deal with this issue in C++11 is to use constant -// initialization and trivial destructors. -// -// Constant initialization is guaranteed to occur before any other code -// executes. Constructors that are declared 'constexpr' are eligible for -// constant initialization. You can annotate a variable declaration with the -// ABSL_CONST_INIT macro to express this intent. For compilers that support -// it, this annotation will cause a compilation error for declarations that -// aren't subject to constant initialization (perhaps because a runtime value -// was passed as a constructor argument). -// -// On program shutdown, lifetime issues can be avoided on global objects by -// ensuring that they contain trivial destructors. A class has a trivial -// destructor unless it has a user-defined destructor, a virtual method or base -// class, or a data member or base class with a non-trivial destructor of its -// own. Objects with static storage duration and a trivial destructor are not -// cleaned up on program shutdown, and are thus safe to access from other code -// running during shutdown. -// -// For a few core Abseil classes, we make a best effort to allow for safe global -// instances, even though these classes have non-trivial destructors. These -// objects can be created with the absl::kConstInit tag. For example: -// ABSL_CONST_INIT absl::Mutex global_mutex(absl::kConstInit); -// -// The line above declares a global variable of type absl::Mutex which can be -// accessed at any point during startup or shutdown. global_mutex's destructor -// will still run, but will not invalidate the object. Note that C++ specifies -// that accessing an object after its destructor has run results in undefined -// behavior, but this pattern works on the toolchains we support. -// -// The absl::kConstInit tag should only be used to define objects with static -// or thread_local storage duration. - -namespace absl { -ABSL_NAMESPACE_BEGIN - -enum ConstInitType { - kConstInit, -}; - -ABSL_NAMESPACE_END -} // namespace absl - -#endif // ABSL_BASE_CONST_INIT_H_ |