fc8dc48020
git-subtree-dir: third_party/abseil_cpp git-subtree-mainline:ffb2ae54begit-subtree-split:768eb2ca28
238 lines
11 KiB
C++
238 lines
11 KiB
C++
// Copyright 2019 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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// File: options.h
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// -----------------------------------------------------------------------------
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//
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// This file contains Abseil configuration options for setting specific
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// implementations instead of letting Abseil determine which implementation to
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// use at compile-time. Setting these options may be useful for package or build
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// managers who wish to guarantee ABI stability within binary builds (which are
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// otherwise difficult to enforce).
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//
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// *** IMPORTANT NOTICE FOR PACKAGE MANAGERS: It is important that
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// maintainers of package managers who wish to package Abseil read and
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// understand this file! ***
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//
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// Abseil contains a number of possible configuration endpoints, based on
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// parameters such as the detected platform, language version, or command-line
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// flags used to invoke the underlying binary. As is the case with all
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// libraries, binaries which contain Abseil code must ensure that separate
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// packages use the same compiled copy of Abseil to avoid a diamond dependency
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// problem, which can occur if two packages built with different Abseil
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// configuration settings are linked together. Diamond dependency problems in
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// C++ may manifest as violations to the One Definition Rule (ODR) (resulting in
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// linker errors), or undefined behavior (resulting in crashes).
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//
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// Diamond dependency problems can be avoided if all packages utilize the same
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// exact version of Abseil. Building from source code with the same compilation
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// parameters is the easiest way to avoid such dependency problems. However, for
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// package managers who cannot control such compilation parameters, we are
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// providing the file to allow you to inject ABI (Application Binary Interface)
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// stability across builds. Settings options in this file will neither change
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// API nor ABI, providing a stable copy of Abseil between packages.
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//
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// Care must be taken to keep options within these configurations isolated
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// from any other dynamic settings, such as command-line flags which could alter
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// these options. This file is provided specifically to help build and package
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// managers provide a stable copy of Abseil within their libraries and binaries;
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// other developers should not have need to alter the contents of this file.
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//
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// -----------------------------------------------------------------------------
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// Usage
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// -----------------------------------------------------------------------------
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//
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// For any particular package release, set the appropriate definitions within
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// this file to whatever value makes the most sense for your package(s). Note
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// that, by default, most of these options, at the moment, affect the
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// implementation of types; future options may affect other implementation
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// details.
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//
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// NOTE: the defaults within this file all assume that Abseil can select the
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// proper Abseil implementation at compile-time, which will not be sufficient
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// to guarantee ABI stability to package managers.
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#ifndef ABSL_BASE_OPTIONS_H_
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#define ABSL_BASE_OPTIONS_H_
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// Include a standard library header to allow configuration based on the
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// standard library in use.
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#ifdef __cplusplus
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#include <ciso646>
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#endif
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// -----------------------------------------------------------------------------
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// Type Compatibility Options
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// -----------------------------------------------------------------------------
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//
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// ABSL_OPTION_USE_STD_ANY
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//
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// This option controls whether absl::any is implemented as an alias to
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// std::any, or as an independent implementation.
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//
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// A value of 0 means to use Abseil's implementation. This requires only C++11
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// support, and is expected to work on every toolchain we support.
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//
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// A value of 1 means to use an alias to std::any. This requires that all code
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// using Abseil is built in C++17 mode or later.
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//
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// A value of 2 means to detect the C++ version being used to compile Abseil,
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// and use an alias only if a working std::any is available. This option is
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// useful when you are building your entire program, including all of its
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// dependencies, from source. It should not be used otherwise -- for example,
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// if you are distributing Abseil in a binary package manager -- since in
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// mode 2, absl::any will name a different type, with a different mangled name
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// and binary layout, depending on the compiler flags passed by the end user.
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// For more info, see https://abseil.io/about/design/dropin-types.
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//
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// User code should not inspect this macro. To check in the preprocessor if
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// absl::any is a typedef of std::any, use the feature macro ABSL_USES_STD_ANY.
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#define ABSL_OPTION_USE_STD_ANY 2
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// ABSL_OPTION_USE_STD_OPTIONAL
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//
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// This option controls whether absl::optional is implemented as an alias to
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// std::optional, or as an independent implementation.
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//
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// A value of 0 means to use Abseil's implementation. This requires only C++11
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// support, and is expected to work on every toolchain we support.
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//
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// A value of 1 means to use an alias to std::optional. This requires that all
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// code using Abseil is built in C++17 mode or later.
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//
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// A value of 2 means to detect the C++ version being used to compile Abseil,
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// and use an alias only if a working std::optional is available. This option
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// is useful when you are building your program from source. It should not be
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// used otherwise -- for example, if you are distributing Abseil in a binary
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// package manager -- since in mode 2, absl::optional will name a different
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// type, with a different mangled name and binary layout, depending on the
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// compiler flags passed by the end user. For more info, see
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// https://abseil.io/about/design/dropin-types.
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// User code should not inspect this macro. To check in the preprocessor if
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// absl::optional is a typedef of std::optional, use the feature macro
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// ABSL_USES_STD_OPTIONAL.
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#define ABSL_OPTION_USE_STD_OPTIONAL 2
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// ABSL_OPTION_USE_STD_STRING_VIEW
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//
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// This option controls whether absl::string_view is implemented as an alias to
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// std::string_view, or as an independent implementation.
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//
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// A value of 0 means to use Abseil's implementation. This requires only C++11
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// support, and is expected to work on every toolchain we support.
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//
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// A value of 1 means to use an alias to std::string_view. This requires that
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// all code using Abseil is built in C++17 mode or later.
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//
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// A value of 2 means to detect the C++ version being used to compile Abseil,
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// and use an alias only if a working std::string_view is available. This
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// option is useful when you are building your program from source. It should
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// not be used otherwise -- for example, if you are distributing Abseil in a
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// binary package manager -- since in mode 2, absl::string_view will name a
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// different type, with a different mangled name and binary layout, depending on
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// the compiler flags passed by the end user. For more info, see
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// https://abseil.io/about/design/dropin-types.
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//
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// User code should not inspect this macro. To check in the preprocessor if
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// absl::string_view is a typedef of std::string_view, use the feature macro
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// ABSL_USES_STD_STRING_VIEW.
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#define ABSL_OPTION_USE_STD_STRING_VIEW 2
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// ABSL_OPTION_USE_STD_VARIANT
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//
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// This option controls whether absl::variant is implemented as an alias to
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// std::variant, or as an independent implementation.
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//
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// A value of 0 means to use Abseil's implementation. This requires only C++11
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// support, and is expected to work on every toolchain we support.
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//
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// A value of 1 means to use an alias to std::variant. This requires that all
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// code using Abseil is built in C++17 mode or later.
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//
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// A value of 2 means to detect the C++ version being used to compile Abseil,
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// and use an alias only if a working std::variant is available. This option
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// is useful when you are building your program from source. It should not be
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// used otherwise -- for example, if you are distributing Abseil in a binary
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// package manager -- since in mode 2, absl::variant will name a different
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// type, with a different mangled name and binary layout, depending on the
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// compiler flags passed by the end user. For more info, see
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// https://abseil.io/about/design/dropin-types.
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//
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// User code should not inspect this macro. To check in the preprocessor if
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// absl::variant is a typedef of std::variant, use the feature macro
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// ABSL_USES_STD_VARIANT.
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#define ABSL_OPTION_USE_STD_VARIANT 2
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// ABSL_OPTION_USE_INLINE_NAMESPACE
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// ABSL_OPTION_INLINE_NAMESPACE_NAME
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//
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// These options controls whether all entities in the absl namespace are
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// contained within an inner inline namespace. This does not affect the
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// user-visible API of Abseil, but it changes the mangled names of all symbols.
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//
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// This can be useful as a version tag if you are distributing Abseil in
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// precompiled form. This will prevent a binary library build of Abseil with
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// one inline namespace being used with headers configured with a different
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// inline namespace name. Binary packagers are reminded that Abseil does not
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// guarantee any ABI stability in Abseil, so any update of Abseil or
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// configuration change in such a binary package should be combined with a
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// new, unique value for the inline namespace name.
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//
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// A value of 0 means not to use inline namespaces.
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//
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// A value of 1 means to use an inline namespace with the given name inside
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// namespace absl. If this is set, ABSL_OPTION_INLINE_NAMESPACE_NAME must also
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// be changed to a new, unique identifier name. In particular "head" is not
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// allowed.
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#define ABSL_OPTION_USE_INLINE_NAMESPACE 0
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#define ABSL_OPTION_INLINE_NAMESPACE_NAME head
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// ABSL_OPTION_HARDENED
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//
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// This option enables a "hardened" build in release mode (in this context,
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// release mode is defined as a build where the `NDEBUG` macro is defined).
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//
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// A value of 0 means that "hardened" mode is not enabled.
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//
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// A value of 1 means that "hardened" mode is enabled.
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//
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// Hardened builds have additional security checks enabled when `NDEBUG` is
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// defined. Defining `NDEBUG` is normally used to turn `assert()` macro into a
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// no-op, as well as disabling other bespoke program consistency checks. By
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// defining ABSL_OPTION_HARDENED to 1, a select set of checks remain enabled in
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// release mode. These checks guard against programming errors that may lead to
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// security vulnerabilities. In release mode, when one of these programming
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// errors is encountered, the program will immediately abort, possibly without
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// any attempt at logging.
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//
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// The checks enabled by this option are not free; they do incur runtime cost.
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//
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// The checks enabled by this option are always active when `NDEBUG` is not
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// defined, even in the case when ABSL_OPTION_HARDENED is defined to 0. The
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// checks enabled by this option may abort the program in a different way and
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// log additional information when `NDEBUG` is not defined.
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#define ABSL_OPTION_HARDENED 0
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#endif // ABSL_BASE_OPTIONS_H_
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