| // 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 0 |
| |
| #endif // ABSL_BASE_OPTIONS_H_ |
