EIC code displayed by LXR master/​include/​absl/​base/​const_init.h	Source navigation Diff markup Identifier search General search
	Version: master test Revert   Change

File indexing completed on 2025-12-16 09:40:42

 // 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_

This page was automatically generated by the 2.3.7 LXR engine. The LXR team