1// -*- C++ -*- 2//===----------------------------------------------------------------------===// 3// 4// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 5// See https://llvm.org/LICENSE.txt for license information. 6// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 7// 8//===----------------------------------------------------------------------===// 9 10#ifndef _LIBCPP___AVAILABILITY 11#define _LIBCPP___AVAILABILITY 12 13#include <__config> 14 15#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER) 16# pragma GCC system_header 17#endif 18 19// Libc++ is shipped by various vendors. In particular, it is used as a system 20// library on macOS, iOS and other Apple platforms. In order for users to be 21// able to compile a binary that is intended to be deployed to an older version 22// of a platform, Clang provides availability attributes [1]. These attributes 23// can be placed on declarations and are used to describe the life cycle of a 24// symbol in the library. 25// 26// The main goal is to ensure a compile-time error if a symbol that hasn't been 27// introduced in a previously released library is used in a program that targets 28// that previously released library. Normally, this would be a load-time error 29// when one tries to launch the program against the older library. 30// 31// For example, the filesystem library was introduced in the dylib in macOS 10.15. 32// If a user compiles on a macOS 10.15 host but targets macOS 10.13 with their 33// program, the compiler would normally not complain (because the required 34// declarations are in the headers), but the dynamic loader would fail to find 35// the symbols when actually trying to launch the program on macOS 10.13. To 36// turn this into a compile-time issue instead, declarations are annotated with 37// when they were introduced, and the compiler can produce a diagnostic if the 38// program references something that isn't available on the deployment target. 39// 40// This mechanism is general in nature, and any vendor can add their markup to 41// the library (see below). Whenever a new feature is added that requires support 42// in the shared library, a macro should be added below to mark this feature 43// as unavailable. When vendors decide to ship the feature as part of their 44// shared library, they can update the markup appropriately. 45// 46// Note that this mechanism is disabled by default in the "upstream" libc++. 47// Availability annotations are only meaningful when shipping libc++ inside 48// a platform (i.e. as a system library), and so vendors that want them should 49// turn those annotations on at CMake configuration time. 50// 51// [1]: https://clang.llvm.org/docs/AttributeReference.html#availability 52 53 54// For backwards compatibility, allow users to define _LIBCPP_DISABLE_AVAILABILITY 55// for a while. 56#if defined(_LIBCPP_DISABLE_AVAILABILITY) 57# if !defined(_LIBCPP_HAS_NO_VENDOR_AVAILABILITY_ANNOTATIONS) 58# define _LIBCPP_HAS_NO_VENDOR_AVAILABILITY_ANNOTATIONS 59# endif 60#endif 61 62// Availability markup is disabled when building the library, or when the compiler 63// doesn't support the proper attributes. 64#if defined(_LIBCPP_BUILDING_LIBRARY) || \ 65 defined(_LIBCXXABI_BUILDING_LIBRARY) || \ 66 !__has_feature(attribute_availability_with_strict) || \ 67 !__has_feature(attribute_availability_in_templates) || \ 68 !__has_extension(pragma_clang_attribute_external_declaration) 69# if !defined(_LIBCPP_HAS_NO_VENDOR_AVAILABILITY_ANNOTATIONS) 70# define _LIBCPP_HAS_NO_VENDOR_AVAILABILITY_ANNOTATIONS 71# endif 72#endif 73 74#if defined(_LIBCPP_HAS_NO_VENDOR_AVAILABILITY_ANNOTATIONS) 75 76 // This controls the availability of std::shared_mutex and std::shared_timed_mutex, 77 // which were added to the dylib later. 78# define _LIBCPP_AVAILABILITY_SHARED_MUTEX 79 80 // These macros control the availability of std::bad_optional_access and 81 // other exception types. These were put in the shared library to prevent 82 // code bloat from every user program defining the vtable for these exception 83 // types. 84# define _LIBCPP_AVAILABILITY_BAD_OPTIONAL_ACCESS 85# define _LIBCPP_AVAILABILITY_BAD_VARIANT_ACCESS 86# define _LIBCPP_AVAILABILITY_BAD_ANY_CAST 87 88 // This controls the availability of std::uncaught_exceptions(). 89# define _LIBCPP_AVAILABILITY_UNCAUGHT_EXCEPTIONS 90 91 // This controls the availability of the sized version of ::operator delete, 92 // which was added to the dylib later. 93# define _LIBCPP_AVAILABILITY_SIZED_NEW_DELETE 94 95 // This controls the availability of the std::future_error exception. 96# define _LIBCPP_AVAILABILITY_FUTURE_ERROR 97 98 // This controls the availability of std::type_info's vtable. 99 // I can't imagine how using std::type_info can work at all if 100 // this isn't supported. 101# define _LIBCPP_AVAILABILITY_TYPEINFO_VTABLE 102 103 // This controls the availability of std::locale::category members 104 // (e.g. std::locale::collate), which are defined in the dylib. 105# define _LIBCPP_AVAILABILITY_LOCALE_CATEGORY 106 107 // This controls the availability of atomic operations on std::shared_ptr 108 // (e.g. `std::atomic_store(std::shared_ptr)`), which require a shared 109 // lock table located in the dylib. 110# define _LIBCPP_AVAILABILITY_ATOMIC_SHARED_PTR 111 112 // These macros control the availability of all parts of <filesystem> that 113 // depend on something in the dylib. 114# define _LIBCPP_AVAILABILITY_FILESYSTEM 115# define _LIBCPP_AVAILABILITY_FILESYSTEM_PUSH 116# define _LIBCPP_AVAILABILITY_FILESYSTEM_POP 117 118 // This controls the availability of std::to_chars. 119# define _LIBCPP_AVAILABILITY_TO_CHARS 120 121 // This controls the availability of the C++20 synchronization library, 122 // which requires shared library support for various operations 123 // (see libcxx/src/atomic.cpp). 124# define _LIBCPP_AVAILABILITY_SYNC 125 126#elif defined(__APPLE__) 127 128# define _LIBCPP_AVAILABILITY_SHARED_MUTEX \ 129 __attribute__((availability(macosx,strict,introduced=10.12))) \ 130 __attribute__((availability(ios,strict,introduced=10.0))) \ 131 __attribute__((availability(tvos,strict,introduced=10.0))) \ 132 __attribute__((availability(watchos,strict,introduced=3.0))) 133# define _LIBCPP_AVAILABILITY_BAD_OPTIONAL_ACCESS \ 134 __attribute__((availability(macosx,strict,introduced=10.13))) \ 135 __attribute__((availability(ios,strict,introduced=11.0))) \ 136 __attribute__((availability(tvos,strict,introduced=11.0))) \ 137 __attribute__((availability(watchos,strict,introduced=4.0))) 138# define _LIBCPP_AVAILABILITY_BAD_VARIANT_ACCESS \ 139 _LIBCPP_AVAILABILITY_BAD_OPTIONAL_ACCESS 140# define _LIBCPP_AVAILABILITY_BAD_ANY_CAST \ 141 _LIBCPP_AVAILABILITY_BAD_OPTIONAL_ACCESS 142# define _LIBCPP_AVAILABILITY_UNCAUGHT_EXCEPTIONS \ 143 __attribute__((availability(macosx,strict,introduced=10.12))) \ 144 __attribute__((availability(ios,strict,introduced=10.0))) \ 145 __attribute__((availability(tvos,strict,introduced=10.0))) \ 146 __attribute__((availability(watchos,strict,introduced=3.0))) 147# define _LIBCPP_AVAILABILITY_SIZED_NEW_DELETE \ 148 __attribute__((availability(macosx,strict,introduced=10.12))) \ 149 __attribute__((availability(ios,strict,introduced=10.0))) \ 150 __attribute__((availability(tvos,strict,introduced=10.0))) \ 151 __attribute__((availability(watchos,strict,introduced=3.0))) 152# define _LIBCPP_AVAILABILITY_FUTURE_ERROR \ 153 __attribute__((availability(ios,strict,introduced=6.0))) 154# define _LIBCPP_AVAILABILITY_TYPEINFO_VTABLE \ 155 __attribute__((availability(macosx,strict,introduced=10.9))) \ 156 __attribute__((availability(ios,strict,introduced=7.0))) 157# define _LIBCPP_AVAILABILITY_LOCALE_CATEGORY \ 158 __attribute__((availability(macosx,strict,introduced=10.9))) \ 159 __attribute__((availability(ios,strict,introduced=7.0))) 160# define _LIBCPP_AVAILABILITY_ATOMIC_SHARED_PTR \ 161 __attribute__((availability(macosx,strict,introduced=10.9))) \ 162 __attribute__((availability(ios,strict,introduced=7.0))) 163# define _LIBCPP_AVAILABILITY_FILESYSTEM \ 164 __attribute__((availability(macosx,strict,introduced=10.15))) \ 165 __attribute__((availability(ios,strict,introduced=13.0))) \ 166 __attribute__((availability(tvos,strict,introduced=13.0))) \ 167 __attribute__((availability(watchos,strict,introduced=6.0))) 168# define _LIBCPP_AVAILABILITY_FILESYSTEM_PUSH \ 169 _Pragma("clang attribute push(__attribute__((availability(macosx,strict,introduced=10.15))), apply_to=any(function,record))") \ 170 _Pragma("clang attribute push(__attribute__((availability(ios,strict,introduced=13.0))), apply_to=any(function,record))") \ 171 _Pragma("clang attribute push(__attribute__((availability(tvos,strict,introduced=13.0))), apply_to=any(function,record))") \ 172 _Pragma("clang attribute push(__attribute__((availability(watchos,strict,introduced=6.0))), apply_to=any(function,record))") 173# define _LIBCPP_AVAILABILITY_FILESYSTEM_POP \ 174 _Pragma("clang attribute pop") \ 175 _Pragma("clang attribute pop") \ 176 _Pragma("clang attribute pop") \ 177 _Pragma("clang attribute pop") 178# define _LIBCPP_AVAILABILITY_TO_CHARS \ 179 _LIBCPP_AVAILABILITY_FILESYSTEM 180# define _LIBCPP_AVAILABILITY_SYNC \ 181 __attribute__((unavailable)) 182 183#else 184 185// ...New vendors can add availability markup here... 186 187# error "It looks like you're trying to enable vendor availability markup, but you haven't defined the corresponding macros yet!" 188 189#endif 190 191// Define availability attributes that depend on _LIBCPP_NO_EXCEPTIONS. 192// Those are defined in terms of the availability attributes above, and 193// should not be vendor-specific. 194#if defined(_LIBCPP_NO_EXCEPTIONS) 195# define _LIBCPP_AVAILABILITY_FUTURE 196# define _LIBCPP_AVAILABILITY_THROW_BAD_ANY_CAST 197# define _LIBCPP_AVAILABILITY_THROW_BAD_OPTIONAL_ACCESS 198# define _LIBCPP_AVAILABILITY_THROW_BAD_VARIANT_ACCESS 199#else 200# define _LIBCPP_AVAILABILITY_FUTURE _LIBCPP_AVAILABILITY_FUTURE_ERROR 201# define _LIBCPP_AVAILABILITY_THROW_BAD_ANY_CAST _LIBCPP_AVAILABILITY_BAD_ANY_CAST 202# define _LIBCPP_AVAILABILITY_THROW_BAD_OPTIONAL_ACCESS _LIBCPP_AVAILABILITY_BAD_OPTIONAL_ACCESS 203# define _LIBCPP_AVAILABILITY_THROW_BAD_VARIANT_ACCESS _LIBCPP_AVAILABILITY_BAD_VARIANT_ACCESS 204#endif 205 206#endif // _LIBCPP___AVAILABILITY 207