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Diffstat (limited to 'absl/base/config.h')
| -rw-r--r-- | absl/base/config.h | 367 |
1 files changed, 367 insertions, 0 deletions
diff --git a/absl/base/config.h b/absl/base/config.h new file mode 100644 index 000000000000..cf47f84c3356 --- /dev/null +++ b/absl/base/config.h @@ -0,0 +1,367 @@ +// +// Copyright 2017 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 +// +// http://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: config.h +// ----------------------------------------------------------------------------- +// +// This header file defines a set of macros for checking the presence of +// important compiler and platform features. Such macros can be used to +// produce portable code by parameterizing compilation based on the presence or +// lack of a given feature. +// +// We define a "feature" as some interface we wish to program to: for example, +// a library function or system call. A value of `1` indicates support for +// that feature; any other value indicates the feature support is undefined. +// +// Example: +// +// Suppose a programmer wants to write a program that uses the 'mmap()' system +// call. The Abseil macro for that feature (`ABSL_HAVE_MMAP`) allows you to +// selectively include the `mmap.h` header and bracket code using that feature +// in the macro: +// +// #include "absl/base/config.h" +// +// #ifdef ABSL_HAVE_MMAP +// #include "sys/mman.h" +// #endif //ABSL_HAVE_MMAP +// +// ... +// #ifdef ABSL_HAVE_MMAP +// void *ptr = mmap(...); +// ... +// #endif // ABSL_HAVE_MMAP + +#ifndef ABSL_BASE_CONFIG_H_ +#define ABSL_BASE_CONFIG_H_ + +// Included for the __GLIBC__ macro (or similar macros on other systems). +#include <limits.h> + +#ifdef __cplusplus +// Included for __GLIBCXX__, _LIBCPP_VERSION +#include <cstddef> +#endif // __cplusplus + +#include "absl/base/policy_checks.h" + +// ----------------------------------------------------------------------------- +// Compiler Feature Checks +// ----------------------------------------------------------------------------- + +// ABSL_HAVE_BUILTIN() +// +// Checks whether the compiler supports a Clang Feature Checking Macro, and if +// so, checks whether it supports the provided builtin function "x" where x +// is one of the functions noted in +// https://clang.llvm.org/docs/LanguageExtensions.html +// +// Note: Use this macro to avoid an extra level of #ifdef __has_builtin check. +// http://releases.llvm.org/3.3/tools/clang/docs/LanguageExtensions.html +#ifdef __has_builtin +#define ABSL_HAVE_BUILTIN(x) __has_builtin(x) +#else +#define ABSL_HAVE_BUILTIN(x) 0 +#endif + +// ABSL_HAVE_TLS is defined to 1 when __thread should be supported. +// We assume __thread is supported on Linux when compiled with Clang or compiled +// against libstdc++ with _GLIBCXX_HAVE_TLS defined. +#ifdef ABSL_HAVE_TLS +#error ABSL_HAVE_TLS cannot be directly set +#elif defined(__linux__) && (defined(__clang__) || defined(_GLIBCXX_HAVE_TLS)) +#define ABSL_HAVE_TLS 1 +#endif + +// There are platforms for which TLS should not be used even though the compiler +// makes it seem like it's supported (Android NDK < r12b for example). +// This is primarily because of linker problems and toolchain misconfiguration: +// Abseil does not intend to support this indefinitely. Currently, the newest +// toolchain that we intend to support that requires this behavior is the +// r11 NDK - allowing for a 5 year support window on that means this option +// is likely to be removed around June of 2021. +#if defined(__ANDROID__) && defined(__clang__) +#if __has_include(<android/ndk-version.h>) +#include <android/ndk-version.h> +#endif +// TLS isn't supported until NDK r12b per +// https://developer.android.com/ndk/downloads/revision_history.html +// Since NDK r16, `__NDK_MAJOR__` and `__NDK_MINOR__` are defined in +// <android/ndk-version.h>. For NDK < r16, users should define these macros, +// e.g. `-D__NDK_MAJOR__=11 -D__NKD_MINOR__=0` for NDK r11. +#if defined(__NDK_MAJOR__) && defined(__NDK_MINOR__) && \ + ((__NDK_MAJOR__ < 12) || ((__NDK_MAJOR__ == 12) && (__NDK_MINOR__ < 1))) +#undef ABSL_HAVE_TLS +#endif +#endif // defined(__ANDROID__) && defined(__clang__) + +// ABSL_HAVE_STD_IS_TRIVIALLY_DESTRUCTIBLE +// +// Checks whether `std::is_trivially_destructible<T>` is supported. +// +// Notes: All supported compilers using libc++ support this feature, as does +// gcc >= 4.8.1 using libstdc++, and Visual Studio. +#ifdef ABSL_HAVE_STD_IS_TRIVIALLY_DESTRUCTIBLE +#error ABSL_HAVE_STD_IS_TRIVIALLY_DESTRUCTIBLE cannot be directly set +#elif defined(_LIBCPP_VERSION) || \ + (!defined(__clang__) && defined(__GNUC__) && defined(__GLIBCXX__) && \ + (__GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 8))) || \ + defined(_MSC_VER) +#define ABSL_HAVE_STD_IS_TRIVIALLY_DESTRUCTIBLE 1 +#endif + +// ABSL_HAVE_STD_IS_TRIVIALLY_CONSTRUCTIBLE +// +// Checks whether `std::is_trivially_default_constructible<T>` and +// `std::is_trivially_copy_constructible<T>` are supported. + +// ABSL_HAVE_STD_IS_TRIVIALLY_ASSIGNABLE +// +// Checks whether `std::is_trivially_copy_assignable<T>` is supported. + +// Notes: Clang with libc++ supports these features, as does gcc >= 5.1 with +// either libc++ or libstdc++, and Visual Studio. +#if defined(ABSL_HAVE_STD_IS_TRIVIALLY_CONSTRUCTIBLE) +#error ABSL_HAVE_STD_IS_TRIVIALLY_CONSTRUCTIBLE cannot be directly set +#elif defined(ABSL_HAVE_STD_IS_TRIVIALLY_ASSIGNABLE) +#error ABSL_HAVE_STD_IS_TRIVIALLY_ASSIGNABLE cannot directly set +#elif (defined(__clang__) && defined(_LIBCPP_VERSION)) || \ + (!defined(__clang__) && defined(__GNUC__) && \ + (__GNUC__ > 5 || (__GNUC__ == 5 && __GNUC_MINOR__ >= 1)) && \ + (defined(_LIBCPP_VERSION) || defined(__GLIBCXX__))) || \ + defined(_MSC_VER) +#define ABSL_HAVE_STD_IS_TRIVIALLY_CONSTRUCTIBLE 1 +#define ABSL_HAVE_STD_IS_TRIVIALLY_ASSIGNABLE 1 +#endif + +// ABSL_HAVE_THREAD_LOCAL +// +// Checks whether C++11's `thread_local` storage duration specifier is +// supported. +// +// Notes: Clang implements the `thread_local` keyword but Xcode did not support +// the implementation until Xcode 8. +#ifdef ABSL_HAVE_THREAD_LOCAL +#error ABSL_HAVE_THREAD_LOCAL cannot be directly set +#elif !defined(__apple_build_version__) || __apple_build_version__ >= 8000042 +#define ABSL_HAVE_THREAD_LOCAL 1 +#endif + +// ABSL_HAVE_INTRINSIC_INT128 +// +// Checks whether the __int128 compiler extension for a 128-bit integral type is +// supported. +// +// Notes: __SIZEOF_INT128__ is defined by Clang and GCC when __int128 is +// supported, except on ppc64 and aarch64 where __int128 exists but has exhibits +// a sporadic compiler crashing bug. Nvidia's nvcc also defines __GNUC__ and +// __SIZEOF_INT128__ but not all versions actually support __int128. +#ifdef ABSL_HAVE_INTRINSIC_INT128 +#error ABSL_HAVE_INTRINSIC_INT128 cannot be directly set +#elif (defined(__clang__) && defined(__SIZEOF_INT128__) && \ + !defined(__ppc64__) && !defined(__aarch64__)) || \ + (defined(__CUDACC__) && defined(__SIZEOF_INT128__) && \ + __CUDACC_VER__ >= 70000) || \ + (!defined(__clang__) && !defined(__CUDACC__) && defined(__GNUC__) && \ + defined(__SIZEOF_INT128__)) +#define ABSL_HAVE_INTRINSIC_INT128 1 +#endif + +// ABSL_HAVE_EXCEPTIONS +// +// Checks whether the compiler both supports and enables exceptions. Many +// compilers support a "no exceptions" mode that disables exceptions. +// +// Generally, when ABSL_HAVE_EXCEPTIONS is not defined: +// +// * Code using `throw` and `try` may not compile. +// * The `noexcept` specifier will still compile and behave as normal. +// * The `noexcept` operator may still return `false`. +// +// For further details, consult the compiler's documentation. +#ifdef ABSL_HAVE_EXCEPTIONS +#error ABSL_HAVE_EXCEPTIONS cannot be directly set. + +#elif defined(__clang__) +// TODO(calabrese) +// Switch to using __cpp_exceptions when we no longer support versions < 3.6. +// For details on this check, see: +// http://releases.llvm.org/3.6.0/tools/clang/docs/ReleaseNotes.html#the-exceptions-macro +#if defined(__EXCEPTIONS) && __has_feature(cxx_exceptions) +#define ABSL_HAVE_EXCEPTIONS 1 +#endif // defined(__EXCEPTIONS) && __has_feature(cxx_exceptions) + +// Handle remaining special cases and default to exceptions being supported. +#elif !(defined(__GNUC__) && (__GNUC__ < 5) && !defined(__EXCEPTIONS)) && \ + !(defined(__GNUC__) && (__GNUC__ >= 5) && !defined(__cpp_exceptions)) && \ + !(defined(_MSC_VER) && !defined(_CPPUNWIND)) +#define ABSL_HAVE_EXCEPTIONS 1 +#endif + +// ----------------------------------------------------------------------------- +// Platform Feature Checks +// ----------------------------------------------------------------------------- + +// Currently supported operating systems and associated preprocessor +// symbols: +// +// Linux and Linux-derived __linux__ +// Android __ANDROID__ (implies __linux__) +// Linux (non-Android) __linux__ && !__ANDROID__ +// Darwin (Mac OS X and iOS) __APPLE__ +// Akaros (http://akaros.org) __ros__ +// Windows _WIN32 +// NaCL __native_client__ +// AsmJS __asmjs__ +// Fuschia __Fuchsia__ +// +// Note that since Android defines both __ANDROID__ and __linux__, one +// may probe for either Linux or Android by simply testing for __linux__. + +// ABSL_HAVE_MMAP +// +// Checks whether the platform has an mmap(2) implementation as defined in +// POSIX.1-2001. +#ifdef ABSL_HAVE_MMAP +#error ABSL_HAVE_MMAP cannot be directly set +#elif defined(__linux__) || defined(__APPLE__) || defined(__ros__) || \ + defined(__native_client__) || defined(__asmjs__) || defined(__Fuchsia__) +#define ABSL_HAVE_MMAP 1 +#endif + +// ABSL_HAVE_PTHREAD_GETSCHEDPARAM +// +// Checks whether the platform implements the pthread_(get|set)schedparam(3) +// functions as defined in POSIX.1-2001. +#ifdef ABSL_HAVE_PTHREAD_GETSCHEDPARAM +#error ABSL_HAVE_PTHREAD_GETSCHEDPARAM cannot be directly set +#elif defined(__linux__) || defined(__APPLE__) || defined(__ros__) +#define ABSL_HAVE_PTHREAD_GETSCHEDPARAM 1 +#endif + +// ABSL_HAVE_SCHED_YIELD +// +// Checks whether the platform implements sched_yield(2) as defined in +// POSIX.1-2001. +#ifdef ABSL_HAVE_SCHED_YIELD +#error ABSL_HAVE_SCHED_YIELD cannot be directly set +#elif defined(__linux__) || defined(__ros__) || defined(__native_client__) +#define ABSL_HAVE_SCHED_YIELD 1 +#endif + +// ABSL_HAVE_SEMAPHORE_H +// +// Checks whether the platform supports the <semaphore.h> header and sem_open(3) +// family of functions as standardized in POSIX.1-2001. +// +// Note: While Apple provides <semaphore.h> for both iOS and macOS, it is +// explicity deprecated and will cause build failures if enabled for those +// platforms. We side-step the issue by not defining it here for Apple +// platforms. +#ifdef ABSL_HAVE_SEMAPHORE_H +#error ABSL_HAVE_SEMAPHORE_H cannot be directly set +#elif defined(__linux__) || defined(__ros__) +#define ABSL_HAVE_SEMAPHORE_H 1 +#endif + +// ABSL_HAVE_ALARM +// +// Checks whether the platform supports the <signal.h> header and alarm(2) +// function as standardized in POSIX.1-2001. +#ifdef ABSL_HAVE_ALARM +#error ABSL_HAVE_ALARM cannot be directly set +#elif defined(__GOOGLE_GRTE_VERSION__) +// feature tests for Google's GRTE +#define ABSL_HAVE_ALARM 1 +#elif defined(__GLIBC__) +// feature test for glibc +#define ABSL_HAVE_ALARM 1 +#elif defined(_MSC_VER) +// feature tests for Microsoft's library +#elif defined(__native_client__) +#else +// other standard libraries +#define ABSL_HAVE_ALARM 1 +#endif + +// ABSL_IS_LITTLE_ENDIAN +// ABSL_IS_BIG_ENDIAN +// +// Checks the endianness of the platform. +// +// Notes: uses the built in endian macros provided by GCC (since 4.6) and +// Clang (since 3.2); see +// https://gcc.gnu.org/onlinedocs/cpp/Common-Predefined-Macros.html. +// Otherwise, if _WIN32, assume little endian. Otherwise, bail with an error. +#if defined(ABSL_IS_BIG_ENDIAN) +#error "ABSL_IS_BIG_ENDIAN cannot be directly set." +#endif +#if defined(ABSL_IS_LITTLE_ENDIAN) +#error "ABSL_IS_LITTLE_ENDIAN cannot be directly set." +#endif + +#if (defined(__BYTE_ORDER__) && defined(__ORDER_LITTLE_ENDIAN__) && \ + __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__) +#define ABSL_IS_LITTLE_ENDIAN 1 +#elif defined(__BYTE_ORDER__) && defined(__ORDER_BIG_ENDIAN__) && \ + __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__ +#define ABSL_IS_BIG_ENDIAN 1 +#elif defined(_WIN32) +#define ABSL_IS_LITTLE_ENDIAN 1 +#else +#error "absl endian detection needs to be set up for your compiler" +#endif + +// ABSL_HAVE_STD_ANY +// +// Checks whether C++17 std::any is availble by checking whether <any> exists. +#ifdef ABSL_HAVE_STD_ANY +#error "ABSL_HAVE_STD_ANY cannot be directly set." +#endif + +#ifdef __has_include +#if __has_include(<any>) && __cplusplus >= 201703L +#define ABSL_HAVE_STD_ANY 1 +#endif +#endif + +// ABSL_HAVE_STD_OPTIONAL +// +// Checks whether C++17 std::optional is available. +#ifdef ABSL_HAVE_STD_OPTIONAL +#error "ABSL_HAVE_STD_OPTIONAL cannot be directly set." +#endif + +#ifdef __has_include +#if __has_include(<optional>) && __cplusplus >= 201703L +#define ABSL_HAVE_STD_OPTIONAL 1 +#endif +#endif + +// ABSL_HAVE_STD_STRING_VIEW +// +// Checks whether C++17 std::string_view is available. +#ifdef ABSL_HAVE_STD_STRING_VIEW +#error "ABSL_HAVE_STD_STRING_VIEW cannot be directly set." +#endif + +#ifdef __has_include +#if __has_include(<string_view>) && __cplusplus >= 201703L +#define ABSL_HAVE_STD_STRING_VIEW 1 +#endif +#endif + +#endif // ABSL_BASE_CONFIG_H_ |