1 | // Copyright 2019 The Abseil Authors. |
2 | // |
3 | // Licensed under the Apache License, Version 2.0 (the "License"); |
4 | // you may not use this file except in compliance with the License. |
5 | // You may obtain a copy of the License at |
6 | // |
7 | // https://www.apache.org/licenses/LICENSE-2.0 |
8 | // |
9 | // Unless required by applicable law or agreed to in writing, software |
10 | // distributed under the License is distributed on an "AS IS" BASIS, |
11 | // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
12 | // See the License for the specific language governing permissions and |
13 | // limitations under the License. |
14 | // |
15 | // ----------------------------------------------------------------------------- |
16 | // File: options.h |
17 | // ----------------------------------------------------------------------------- |
18 | // |
19 | // This file contains Abseil configuration options for setting specific |
20 | // implementations instead of letting Abseil determine which implementation to |
21 | // use at compile-time. Setting these options may be useful for package or build |
22 | // managers who wish to guarantee ABI stability within binary builds (which are |
23 | // otherwise difficult to enforce). |
24 | // |
25 | // *** IMPORTANT NOTICE FOR PACKAGE MANAGERS: It is important that |
26 | // maintainers of package managers who wish to package Abseil read and |
27 | // understand this file! *** |
28 | // |
29 | // Abseil contains a number of possible configuration endpoints, based on |
30 | // parameters such as the detected platform, language version, or command-line |
31 | // flags used to invoke the underlying binary. As is the case with all |
32 | // libraries, binaries which contain Abseil code must ensure that separate |
33 | // packages use the same compiled copy of Abseil to avoid a diamond dependency |
34 | // problem, which can occur if two packages built with different Abseil |
35 | // configuration settings are linked together. Diamond dependency problems in |
36 | // C++ may manifest as violations to the One Definition Rule (ODR) (resulting in |
37 | // linker errors), or undefined behavior (resulting in crashes). |
38 | // |
39 | // Diamond dependency problems can be avoided if all packages utilize the same |
40 | // exact version of Abseil. Building from source code with the same compilation |
41 | // parameters is the easiest way to avoid such dependency problems. However, for |
42 | // package managers who cannot control such compilation parameters, we are |
43 | // providing the file to allow you to inject ABI (Application Binary Interface) |
44 | // stability across builds. Settings options in this file will neither change |
45 | // API nor ABI, providing a stable copy of Abseil between packages. |
46 | // |
47 | // Care must be taken to keep options within these configurations isolated |
48 | // from any other dynamic settings, such as command-line flags which could alter |
49 | // these options. This file is provided specifically to help build and package |
50 | // managers provide a stable copy of Abseil within their libraries and binaries; |
51 | // other developers should not have need to alter the contents of this file. |
52 | // |
53 | // ----------------------------------------------------------------------------- |
54 | // Usage |
55 | // ----------------------------------------------------------------------------- |
56 | // |
57 | // For any particular package release, set the appropriate definitions within |
58 | // this file to whatever value makes the most sense for your package(s). Note |
59 | // that, by default, most of these options, at the moment, affect the |
60 | // implementation of types; future options may affect other implementation |
61 | // details. |
62 | // |
63 | // NOTE: the defaults within this file all assume that Abseil can select the |
64 | // proper Abseil implementation at compile-time, which will not be sufficient |
65 | // to guarantee ABI stability to package managers. |
66 | |
67 | #ifndef ABSL_BASE_OPTIONS_H_ |
68 | #define ABSL_BASE_OPTIONS_H_ |
69 | |
70 | // Include a standard library header to allow configuration based on the |
71 | // standard library in use. |
72 | #ifdef __cplusplus |
73 | #include <ciso646> |
74 | #endif |
75 | |
76 | // ----------------------------------------------------------------------------- |
77 | // Type Compatibility Options |
78 | // ----------------------------------------------------------------------------- |
79 | // |
80 | // ABSL_OPTION_USE_STD_ANY |
81 | // |
82 | // This option controls whether absl::any is implemented as an alias to |
83 | // std::any, or as an independent implementation. |
84 | // |
85 | // A value of 0 means to use Abseil's implementation. This requires only C++11 |
86 | // support, and is expected to work on every toolchain we support. |
87 | // |
88 | // A value of 1 means to use an alias to std::any. This requires that all code |
89 | // using Abseil is built in C++17 mode or later. |
90 | // |
91 | // A value of 2 means to detect the C++ version being used to compile Abseil, |
92 | // and use an alias only if a working std::any is available. This option is |
93 | // useful when you are building your entire program, including all of its |
94 | // dependencies, from source. It should not be used otherwise -- for example, |
95 | // if you are distributing Abseil in a binary package manager -- since in |
96 | // mode 2, absl::any will name a different type, with a different mangled name |
97 | // and binary layout, depending on the compiler flags passed by the end user. |
98 | // For more info, see https://abseil.io/about/design/dropin-types. |
99 | // |
100 | // User code should not inspect this macro. To check in the preprocessor if |
101 | // absl::any is a typedef of std::any, use the feature macro ABSL_USES_STD_ANY. |
102 | |
103 | #define ABSL_OPTION_USE_STD_ANY 0 |
104 | |
105 | |
106 | // ABSL_OPTION_USE_STD_OPTIONAL |
107 | // |
108 | // This option controls whether absl::optional is implemented as an alias to |
109 | // std::optional, or as an independent implementation. |
110 | // |
111 | // A value of 0 means to use Abseil's implementation. This requires only C++11 |
112 | // support, and is expected to work on every toolchain we support. |
113 | // |
114 | // A value of 1 means to use an alias to std::optional. This requires that all |
115 | // code using Abseil is built in C++17 mode or later. |
116 | // |
117 | // A value of 2 means to detect the C++ version being used to compile Abseil, |
118 | // and use an alias only if a working std::optional is available. This option |
119 | // is useful when you are building your program from source. It should not be |
120 | // used otherwise -- for example, if you are distributing Abseil in a binary |
121 | // package manager -- since in mode 2, absl::optional will name a different |
122 | // type, with a different mangled name and binary layout, depending on the |
123 | // compiler flags passed by the end user. For more info, see |
124 | // https://abseil.io/about/design/dropin-types. |
125 | |
126 | // User code should not inspect this macro. To check in the preprocessor if |
127 | // absl::optional is a typedef of std::optional, use the feature macro |
128 | // ABSL_USES_STD_OPTIONAL. |
129 | |
130 | #define ABSL_OPTION_USE_STD_OPTIONAL 0 |
131 | |
132 | |
133 | // ABSL_OPTION_USE_STD_STRING_VIEW |
134 | // |
135 | // This option controls whether absl::string_view is implemented as an alias to |
136 | // std::string_view, or as an independent implementation. |
137 | // |
138 | // A value of 0 means to use Abseil's implementation. This requires only C++11 |
139 | // support, and is expected to work on every toolchain we support. |
140 | // |
141 | // A value of 1 means to use an alias to std::string_view. This requires that |
142 | // all code using Abseil is built in C++17 mode or later. |
143 | // |
144 | // A value of 2 means to detect the C++ version being used to compile Abseil, |
145 | // and use an alias only if a working std::string_view is available. This |
146 | // option is useful when you are building your program from source. It should |
147 | // not be used otherwise -- for example, if you are distributing Abseil in a |
148 | // binary package manager -- since in mode 2, absl::string_view will name a |
149 | // different type, with a different mangled name and binary layout, depending on |
150 | // the compiler flags passed by the end user. For more info, see |
151 | // https://abseil.io/about/design/dropin-types. |
152 | // |
153 | // User code should not inspect this macro. To check in the preprocessor if |
154 | // absl::string_view is a typedef of std::string_view, use the feature macro |
155 | // ABSL_USES_STD_STRING_VIEW. |
156 | |
157 | #define ABSL_OPTION_USE_STD_STRING_VIEW 0 |
158 | |
159 | // ABSL_OPTION_USE_STD_VARIANT |
160 | // |
161 | // This option controls whether absl::variant is implemented as an alias to |
162 | // std::variant, or as an independent implementation. |
163 | // |
164 | // A value of 0 means to use Abseil's implementation. This requires only C++11 |
165 | // support, and is expected to work on every toolchain we support. |
166 | // |
167 | // A value of 1 means to use an alias to std::variant. This requires that all |
168 | // code using Abseil is built in C++17 mode or later. |
169 | // |
170 | // A value of 2 means to detect the C++ version being used to compile Abseil, |
171 | // and use an alias only if a working std::variant is available. This option |
172 | // is useful when you are building your program from source. It should not be |
173 | // used otherwise -- for example, if you are distributing Abseil in a binary |
174 | // package manager -- since in mode 2, absl::variant will name a different |
175 | // type, with a different mangled name and binary layout, depending on the |
176 | // compiler flags passed by the end user. For more info, see |
177 | // https://abseil.io/about/design/dropin-types. |
178 | // |
179 | // User code should not inspect this macro. To check in the preprocessor if |
180 | // absl::variant is a typedef of std::variant, use the feature macro |
181 | // ABSL_USES_STD_VARIANT. |
182 | |
183 | #define ABSL_OPTION_USE_STD_VARIANT 0 |
184 | |
185 | |
186 | // ABSL_OPTION_USE_INLINE_NAMESPACE |
187 | // ABSL_OPTION_INLINE_NAMESPACE_NAME |
188 | // |
189 | // These options controls whether all entities in the absl namespace are |
190 | // contained within an inner inline namespace. This does not affect the |
191 | // user-visible API of Abseil, but it changes the mangled names of all symbols. |
192 | // |
193 | // This can be useful as a version tag if you are distributing Abseil in |
194 | // precompiled form. This will prevent a binary library build of Abseil with |
195 | // one inline namespace being used with headers configured with a different |
196 | // inline namespace name. Binary packagers are reminded that Abseil does not |
197 | // guarantee any ABI stability in Abseil, so any update of Abseil or |
198 | // configuration change in such a binary package should be combined with a |
199 | // new, unique value for the inline namespace name. |
200 | // |
201 | // A value of 0 means not to use inline namespaces. |
202 | // |
203 | // A value of 1 means to use an inline namespace with the given name inside |
204 | // namespace absl. If this is set, ABSL_OPTION_INLINE_NAMESPACE_NAME must also |
205 | // be changed to a new, unique identifier name. In particular "head" is not |
206 | // allowed. |
207 | |
208 | #define ABSL_OPTION_USE_INLINE_NAMESPACE 0 |
209 | #define ABSL_OPTION_INLINE_NAMESPACE_NAME head |
210 | |
211 | // ABSL_OPTION_HARDENED |
212 | // |
213 | // This option enables a "hardened" build in release mode (in this context, |
214 | // release mode is defined as a build where the `NDEBUG` macro is defined). |
215 | // |
216 | // A value of 0 means that "hardened" mode is not enabled. |
217 | // |
218 | // A value of 1 means that "hardened" mode is enabled. |
219 | // |
220 | // Hardened builds have additional security checks enabled when `NDEBUG` is |
221 | // defined. Defining `NDEBUG` is normally used to turn `assert()` macro into a |
222 | // no-op, as well as disabling other bespoke program consistency checks. By |
223 | // defining ABSL_OPTION_HARDENED to 1, a select set of checks remain enabled in |
224 | // release mode. These checks guard against programming errors that may lead to |
225 | // security vulnerabilities. In release mode, when one of these programming |
226 | // errors is encountered, the program will immediately abort, possibly without |
227 | // any attempt at logging. |
228 | // |
229 | // The checks enabled by this option are not free; they do incur runtime cost. |
230 | // |
231 | // The checks enabled by this option are always active when `NDEBUG` is not |
232 | // defined, even in the case when ABSL_OPTION_HARDENED is defined to 0. The |
233 | // checks enabled by this option may abort the program in a different way and |
234 | // log additional information when `NDEBUG` is not defined. |
235 | |
236 | #define ABSL_OPTION_HARDENED 1 |
237 | |
238 | #endif // ABSL_BASE_OPTIONS_H_ |
239 | |