1e39f8626a
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b842b7fd9b1289be31f0b7ee8e62e48e550747cf by Greg Falcon <gfalcon@google.com>:
Change the Cord str_format formatter to use iteration instead of CordReader.
When Cord is publicly released, CordReader is not going with it.
PiperOrigin-RevId: 284780736
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28e76c08ea7185a7ff9f4e0e02ae565fbbf7980f by Greg Falcon <gfalcon@google.com>:
Implementation detail change.
Introduce ABSL_NAMESPACE_BEGIN and _END annotation macros which indicate the beginning and end of a `namespace absl` scope. Currently these do nothing, but they will be used to inject an inline namespace for LTS builds (to avoid symbol collisions against other Abseil versions).
These macros should not be used by end users, because end users should never write `namespace absl {` in their own code.
This CL applies these annotations to all code under //absl/base/. The rest of Abseil will be annotated in this way in follow-up CLs.
PiperOrigin-RevId: 284776410
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e1711dc6d696dcca50d4e7d4b4d8f3076575b7ec by Abseil Team <absl-team@google.com>:
--help changed to report long flags.
PiperOrigin-RevId: 284757720
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78f66a68f428bbbd19d8d60e1125f43ba765fd35 by Tom Manshreck <shreck@google.com>:
Update comment on + or - in SimpleAToi()
PiperOrigin-RevId: 284231843
GitOrigin-RevId: b842b7fd9b1289be31f0b7ee8e62e48e550747cf
Change-Id: I3046b31391bd11c8bc4abab7785a863c377cd757
76 lines
3.4 KiB
C++
76 lines
3.4 KiB
C++
// Copyright 2017 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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//
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// -----------------------------------------------------------------------------
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// kConstInit
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// -----------------------------------------------------------------------------
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//
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// A constructor tag used to mark an object as safe for use as a global
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// variable, avoiding the usual lifetime issues that can affect globals.
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#ifndef ABSL_BASE_CONST_INIT_H_
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#define ABSL_BASE_CONST_INIT_H_
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#include "absl/base/config.h"
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// In general, objects with static storage duration (such as global variables)
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// can trigger tricky object lifetime situations. Attempting to access them
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// from the constructors or destructors of other global objects can result in
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// undefined behavior, unless their constructors and destructors are designed
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// with this issue in mind.
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//
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// The normal way to deal with this issue in C++11 is to use constant
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// initialization and trivial destructors.
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//
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// Constant initialization is guaranteed to occur before any other code
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// executes. Constructors that are declared 'constexpr' are eligible for
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// constant initialization. You can annotate a variable declaration with the
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// ABSL_CONST_INIT macro to express this intent. For compilers that support
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// it, this annotation will cause a compilation error for declarations that
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// aren't subject to constant initialization (perhaps because a runtime value
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// was passed as a constructor argument).
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//
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// On program shutdown, lifetime issues can be avoided on global objects by
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// ensuring that they contain trivial destructors. A class has a trivial
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// destructor unless it has a user-defined destructor, a virtual method or base
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// class, or a data member or base class with a non-trivial destructor of its
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// own. Objects with static storage duration and a trivial destructor are not
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// cleaned up on program shutdown, and are thus safe to access from other code
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// running during shutdown.
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//
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// For a few core Abseil classes, we make a best effort to allow for safe global
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// instances, even though these classes have non-trivial destructors. These
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// objects can be created with the absl::kConstInit tag. For example:
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// ABSL_CONST_INIT absl::Mutex global_mutex(absl::kConstInit);
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//
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// The line above declares a global variable of type absl::Mutex which can be
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// accessed at any point during startup or shutdown. global_mutex's destructor
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// will still run, but will not invalidate the object. Note that C++ specifies
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// that accessing an object after its destructor has run results in undefined
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// behavior, but this pattern works on the toolchains we support.
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//
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// The absl::kConstInit tag should only be used to define objects with static
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// or thread_local storage duration.
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namespace absl {
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ABSL_NAMESPACE_BEGIN
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enum ConstInitType {
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kConstInit,
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};
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ABSL_NAMESPACE_END
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} // namespace absl
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#endif // ABSL_BASE_CONST_INIT_H_
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