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tvl-depot/absl/base/config.h
Abseil Team d732f2014b Changes imported from Abseil "staging" branch: 
- d5a5960a133967e4af02836d304884cd6cbd6e46 Adjusting time tests for flakiness by Gennadiy Civil <misterg@google.com>
  - ccb8535fdc92c3c99bfa2795e75d3fbdcb134571 Internal-only tweak. by Jorg Brown <jorg@google.com>
  - 4c03dd9e54bd4645e7e7a8dfb3c590f5b0654884 Fix comment on some C++11 type traits backport. by Xiaoyi Zhang <zhangxy@google.com>
  - 43cd12d2304464163e33ae932fbb842a869213dd Allow intrinsic int128 to be set for __ppc64__ targets. by Abseil Team <absl-team@google.com>
  - 789e9c13de67ef3c7ba09c765c3484621897b6bb Update README.md description of 'types' library to be con... by Abseil Team <absl-team@google.com>
  - 8be10d7683c90b85244ddc67360a7ca2dfffdf01 Update comment on move constructors' noexcept specificati... by Xiaoyi Zhang <zhangxy@google.com>

GitOrigin-RevId: d5a5960a133967e4af02836d304884cd6cbd6e46
Change-Id: I743efee47b9e65f46a44d9ab80ccd62cfd0c1301
2017-10-05 16:55:26 -04:00

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//
// 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
#if defined(__APPLE__)
// Included for TARGET_OS_IPHONE, __IPHONE_OS_VERSION_MIN_REQUIRED,
// __IPHONE_8_0.
#include <Availability.h>
#include <TargetConditionals.h>
#endif
#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.
#ifdef ABSL_HAVE_THREAD_LOCAL
#error ABSL_HAVE_THREAD_LOCAL cannot be directly set
#elif !defined(__apple_build_version__) || \
((__apple_build_version__ >= 8000042) && \
!(TARGET_OS_IPHONE && __IPHONE_OS_VERSION_MIN_REQUIRED < __IPHONE_9_0))
// Notes: Xcode's clang did not support `thread_local` until version
// 8, and even then not for all iOS < 9.0.
#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(__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 available 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_
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