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