1/* Proposed SG14 status_code
2(C) 2018 - 2021 Niall Douglas <http://www.nedproductions.biz/> (5 commits)
3File Created: Feb 2018
4
5
6Licensed under the Apache License, Version 2.0 (the "License");
7you may not use this file except in compliance with the License.
8You may obtain a copy of the License in the accompanying file
9Licence.txt or at
10
11http://www.apache.org/licenses/LICENSE-2.0
12
13Unless required by applicable law or agreed to in writing, software
14distributed under the License is distributed on an "AS IS" BASIS,
15WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
16See the License for the specific language governing permissions and
17limitations under the License.
18
19
20Distributed under the Boost Software License, Version 1.0.
21(See accompanying file Licence.txt or copy at
22http://www.boost.org/LICENSE_1_0.txt)
23*/
24
25#ifndef BOOST_OUTCOME_SYSTEM_ERROR2_CONFIG_HPP
26#define BOOST_OUTCOME_SYSTEM_ERROR2_CONFIG_HPP
27
28// < 0.1 each
29#include <cassert>
30#include <cstddef> // for size_t
31#include <cstdlib> // for free
32
33// 0.22
34#include <type_traits>
35
36// 0.29
37#include <atomic>
38
39// 0.28 (0.15 of which is exception_ptr)
40#include <exception> // for std::exception
41// <new> includes <exception>, <exception> includes <new>
42#include <new>
43
44// 0.01
45#include <initializer_list>
46
47#ifndef BOOST_OUTCOME_SYSTEM_ERROR2_HAVE_BIT_CAST
48#ifdef __has_include
49#if __has_include(<bit>) && (__cplusplus >= 202002L || _HAS_CXX20)
50#define BOOST_OUTCOME_SYSTEM_ERROR2_HAVE_BIT_CAST 1
51#endif
52#elif __cplusplus >= 202002L
53#define BOOST_OUTCOME_SYSTEM_ERROR2_HAVE_BIT_CAST 1
54#endif
55#ifndef BOOST_OUTCOME_SYSTEM_ERROR2_HAVE_BIT_CAST
56#define BOOST_OUTCOME_SYSTEM_ERROR2_HAVE_BIT_CAST 0
57#endif
58#endif
59#if BOOST_OUTCOME_SYSTEM_ERROR2_HAVE_BIT_CAST
60#include <bit>
61#if __cpp_lib_bit_cast < 201806L
62#undef BOOST_OUTCOME_SYSTEM_ERROR2_HAVE_BIT_CAST
63#define BOOST_OUTCOME_SYSTEM_ERROR2_HAVE_BIT_CAST 0
64#endif
65#endif
66
67#if BOOST_OUTCOME_SYSTEM_ERROR2_USE_STD_ADDRESSOF
68#include <memory> // for std::addressof
69#define BOOST_OUTCOME_SYSTEM_ERROR2_ADDRESS_OF(...) std::addressof(__VA_ARGS__)
70#else
71#define BOOST_OUTCOME_SYSTEM_ERROR2_ADDRESS_OF(...) (&__VA_ARGS__)
72#endif
73
74#ifndef BOOST_OUTCOME_SYSTEM_ERROR2_CONSTEXPR14
75#if defined(BOOST_OUTCOME_STANDARDESE_IS_IN_THE_HOUSE) || __cplusplus >= 201400 || _MSC_VER >= 1910 /* VS2017 */
76//! Defined to be `constexpr` when on C++ 14 or better compilers. Usually automatic, can be overriden.
77#define BOOST_OUTCOME_SYSTEM_ERROR2_CONSTEXPR14 constexpr
78#else
79#define BOOST_OUTCOME_SYSTEM_ERROR2_CONSTEXPR14
80#endif
81#endif
82
83#ifndef BOOST_OUTCOME_SYSTEM_ERROR2_CONSTEXPR20
84#if defined(BOOST_OUTCOME_STANDARDESE_IS_IN_THE_HOUSE) || __cplusplus >= 202000 || _HAS_CXX20
85//! Defined to be `constexpr` when on C++ 20 or better compilers. Usually automatic, can be overriden.
86#define BOOST_OUTCOME_SYSTEM_ERROR2_CONSTEXPR20 constexpr
87#else
88#define BOOST_OUTCOME_SYSTEM_ERROR2_CONSTEXPR20
89#endif
90#endif
91
92
93#ifndef BOOST_OUTCOME_SYSTEM_ERROR2_NORETURN
94#if defined(BOOST_OUTCOME_STANDARDESE_IS_IN_THE_HOUSE) || (_HAS_CXX17 && _MSC_VER >= 1911 /* VS2017.3 */)
95#define BOOST_OUTCOME_SYSTEM_ERROR2_NORETURN [[noreturn]]
96#endif
97#endif
98#if !defined(BOOST_OUTCOME_SYSTEM_ERROR2_NORETURN)
99#ifdef __has_cpp_attribute
100#if __has_cpp_attribute(noreturn)
101#define BOOST_OUTCOME_SYSTEM_ERROR2_NORETURN [[noreturn]]
102#endif
103#endif
104#endif
105#if !defined(BOOST_OUTCOME_SYSTEM_ERROR2_NORETURN)
106#if defined(_MSC_VER)
107#define BOOST_OUTCOME_SYSTEM_ERROR2_NORETURN __declspec(noreturn)
108#elif defined(__GNUC__)
109#define BOOST_OUTCOME_SYSTEM_ERROR2_NORETURN __attribute__((__noreturn__))
110#else
111#define BOOST_OUTCOME_SYSTEM_ERROR2_NORETURN
112#endif
113#endif
114// GCCs before 7 don't grok [[noreturn]] virtual functions, and warn annoyingly
115#if defined(__GNUC__) && !defined(__clang__) && __GNUC__ < 7
116#undef BOOST_OUTCOME_SYSTEM_ERROR2_NORETURN
117#define BOOST_OUTCOME_SYSTEM_ERROR2_NORETURN
118#endif
119
120#ifndef BOOST_OUTCOME_SYSTEM_ERROR2_NODISCARD
121#if defined(BOOST_OUTCOME_STANDARDESE_IS_IN_THE_HOUSE) || (_HAS_CXX17 && _MSC_VER >= 1911 /* VS2017.3 */)
122#define BOOST_OUTCOME_SYSTEM_ERROR2_NODISCARD [[nodiscard]]
123#endif
124#endif
125#ifndef BOOST_OUTCOME_SYSTEM_ERROR2_NODISCARD
126#ifdef __has_cpp_attribute
127#if __has_cpp_attribute(nodiscard)
128#define BOOST_OUTCOME_SYSTEM_ERROR2_NODISCARD [[nodiscard]]
129#endif
130#elif defined(__clang__)
131#define BOOST_OUTCOME_SYSTEM_ERROR2_NODISCARD __attribute__((warn_unused_result))
132#elif defined(_MSC_VER)
133// _Must_inspect_result_ expands into this
134#define BOOST_OUTCOME_SYSTEM_ERROR2_NODISCARD \
135 __declspec( \
136 "SAL_name" \
137 "(" \
138 "\"_Must_inspect_result_\"" \
139 "," \
140 "\"\"" \
141 "," \
142 "\"2\"" \
143 ")") __declspec("SAL_begin") __declspec("SAL_post") __declspec("SAL_mustInspect") __declspec("SAL_post") __declspec("SAL_checkReturn") __declspec("SAL_end")
144#endif
145#endif
146#ifndef BOOST_OUTCOME_SYSTEM_ERROR2_NODISCARD
147#define BOOST_OUTCOME_SYSTEM_ERROR2_NODISCARD
148#endif
149
150#ifndef BOOST_OUTCOME_SYSTEM_ERROR2_TRIVIAL_ABI
151#if defined(BOOST_OUTCOME_STANDARDESE_IS_IN_THE_HOUSE) || (__clang_major__ >= 7 && !defined(__APPLE__))
152//! Defined to be `[[clang::trivial_abi]]` when on a new enough clang compiler. Usually automatic, can be overriden.
153#define BOOST_OUTCOME_SYSTEM_ERROR2_TRIVIAL_ABI [[clang::trivial_abi]]
154#else
155#define BOOST_OUTCOME_SYSTEM_ERROR2_TRIVIAL_ABI
156#endif
157#endif
158
159#if defined(__cpp_concepts) && !defined(BOOST_OUTCOME_SYSTEM_ERROR2_DISABLE_CONCEPTS_SUPPORT)
160#define BOOST_OUTCOME_SYSTEM_ERROR2_GLUE(x, y) x y
161
162#define BOOST_OUTCOME_SYSTEM_ERROR2_RETURN_ARG_COUNT(_1_, _2_, _3_, _4_, _5_, _6_, _7_, _8_, count, ...) count
163#define BOOST_OUTCOME_SYSTEM_ERROR2_EXPAND_ARGS(args) BOOST_OUTCOME_SYSTEM_ERROR2_RETURN_ARG_COUNT args
164#define BOOST_OUTCOME_SYSTEM_ERROR2_COUNT_ARGS_MAX8(...) BOOST_OUTCOME_SYSTEM_ERROR2_EXPAND_ARGS((__VA_ARGS__, 8, 7, 6, 5, 4, 3, 2, 1, 0))
165
166#define BOOST_OUTCOME_SYSTEM_ERROR2_OVERLOAD_MACRO2(name, count) name##count
167#define BOOST_OUTCOME_SYSTEM_ERROR2_OVERLOAD_MACRO1(name, count) BOOST_OUTCOME_SYSTEM_ERROR2_OVERLOAD_MACRO2(name, count)
168#define BOOST_OUTCOME_SYSTEM_ERROR2_OVERLOAD_MACRO(name, count) BOOST_OUTCOME_SYSTEM_ERROR2_OVERLOAD_MACRO1(name, count)
169
170#define BOOST_OUTCOME_SYSTEM_ERROR2_CALL_OVERLOAD(name, ...) BOOST_OUTCOME_SYSTEM_ERROR2_GLUE(BOOST_OUTCOME_SYSTEM_ERROR2_OVERLOAD_MACRO(name, BOOST_OUTCOME_SYSTEM_ERROR2_COUNT_ARGS_MAX8(__VA_ARGS__)), (__VA_ARGS__))
171
172#define BOOST_OUTCOME_SYSTEM_ERROR2_TREQUIRES_EXPAND8(a, b, c, d, e, f, g, h) a &&BOOST_OUTCOME_SYSTEM_ERROR2_TREQUIRES_EXPAND7(b, c, d, e, f, g, h)
173#define BOOST_OUTCOME_SYSTEM_ERROR2_TREQUIRES_EXPAND7(a, b, c, d, e, f, g) a &&BOOST_OUTCOME_SYSTEM_ERROR2_TREQUIRES_EXPAND6(b, c, d, e, f, g)
174#define BOOST_OUTCOME_SYSTEM_ERROR2_TREQUIRES_EXPAND6(a, b, c, d, e, f) a &&BOOST_OUTCOME_SYSTEM_ERROR2_TREQUIRES_EXPAND5(b, c, d, e, f)
175#define BOOST_OUTCOME_SYSTEM_ERROR2_TREQUIRES_EXPAND5(a, b, c, d, e) a &&BOOST_OUTCOME_SYSTEM_ERROR2_TREQUIRES_EXPAND4(b, c, d, e)
176#define BOOST_OUTCOME_SYSTEM_ERROR2_TREQUIRES_EXPAND4(a, b, c, d) a &&BOOST_OUTCOME_SYSTEM_ERROR2_TREQUIRES_EXPAND3(b, c, d)
177#define BOOST_OUTCOME_SYSTEM_ERROR2_TREQUIRES_EXPAND3(a, b, c) a &&BOOST_OUTCOME_SYSTEM_ERROR2_TREQUIRES_EXPAND2(b, c)
178#define BOOST_OUTCOME_SYSTEM_ERROR2_TREQUIRES_EXPAND2(a, b) a &&BOOST_OUTCOME_SYSTEM_ERROR2_TREQUIRES_EXPAND1(b)
179#define BOOST_OUTCOME_SYSTEM_ERROR2_TREQUIRES_EXPAND1(a) a
180
181//! Expands into a && b && c && ...
182#define BOOST_OUTCOME_SYSTEM_ERROR2_TREQUIRES(...) requires BOOST_OUTCOME_SYSTEM_ERROR2_CALL_OVERLOAD(BOOST_OUTCOME_SYSTEM_ERROR2_TREQUIRES_EXPAND, __VA_ARGS__)
183
184#define BOOST_OUTCOME_SYSTEM_ERROR2_TEMPLATE(...) template <__VA_ARGS__>
185#define BOOST_OUTCOME_SYSTEM_ERROR2_TEXPR(...) \
186 requires { (__VA_ARGS__); }
187#define BOOST_OUTCOME_SYSTEM_ERROR2_TPRED(...) (__VA_ARGS__)
188#if !defined(_MSC_VER) || _MSC_FULL_VER >= 192400000 // VS 2019 16.3 is broken here
189#define BOOST_OUTCOME_SYSTEM_ERROR2_REQUIRES(...) requires(__VA_ARGS__)
190#else
191#define BOOST_OUTCOME_SYSTEM_ERROR2_REQUIRES(...)
192#endif
193#else
194#define BOOST_OUTCOME_SYSTEM_ERROR2_TEMPLATE(...) template <__VA_ARGS__
195#define BOOST_OUTCOME_SYSTEM_ERROR2_TREQUIRES(...) , __VA_ARGS__ >
196#define BOOST_OUTCOME_SYSTEM_ERROR2_TEXPR(...) typename = decltype(__VA_ARGS__)
197#ifdef _MSC_VER
198// MSVC gives an error if every specialisation of a template is always ill-formed, so
199// the more powerful SFINAE form below causes pukeage :(
200#define BOOST_OUTCOME_SYSTEM_ERROR2_TPRED(...) typename = typename std::enable_if<(__VA_ARGS__)>::type
201#else
202#define BOOST_OUTCOME_SYSTEM_ERROR2_TPRED(...) typename std::enable_if<(__VA_ARGS__), bool>::type = true
203#endif
204#define BOOST_OUTCOME_SYSTEM_ERROR2_REQUIRES(...)
205#endif
206
207#ifndef BOOST_OUTCOME_SYSTEM_ERROR2_NAMESPACE
208//! The system_error2 namespace name.
209#define BOOST_OUTCOME_SYSTEM_ERROR2_NAMESPACE system_error2
210//! Begins the system_error2 namespace.
211#define BOOST_OUTCOME_SYSTEM_ERROR2_NAMESPACE_BEGIN \
212 namespace system_error2 \
213 {
214//! Ends the system_error2 namespace.
215#define BOOST_OUTCOME_SYSTEM_ERROR2_NAMESPACE_END }
216#endif
217
218//! Namespace for the library
219BOOST_OUTCOME_SYSTEM_ERROR2_NAMESPACE_BEGIN
220
221//! Namespace for user specialised traits
222namespace traits
223{
224 /*! Specialise to true if you guarantee that a type is move bitcopying (i.e.
225 its move constructor equals copying bits from old to new, old is left in a
226 default constructed state, and calling the destructor on a default constructed
227 instance is trivial). All trivially copyable types are move bitcopying by
228 definition, and that is the unspecialised implementation.
229 */
230 template <class T> struct is_move_bitcopying
231 {
232 static constexpr bool value = std::is_trivially_copyable<T>::value;
233 };
234} // namespace traits
235
236namespace detail
237{
238#if __cplusplus >= 201400 || _MSC_VER >= 1910 /* VS2017 */
239 inline constexpr size_t cstrlen(const char *str)
240 {
241 const char *end = nullptr;
242 for(end = str; *end != 0; ++end) // NOLINT
243 ;
244 return end - str;
245 }
246#else
247 inline constexpr size_t cstrlen_(const char *str, size_t acc) { return (str[0] == 0) ? acc : cstrlen_(str + 1, acc + 1); }
248 inline constexpr size_t cstrlen(const char *str) { return cstrlen_(str, 0); }
249#endif
250
251#if(__cplusplus >= 202002L || _MSVC_LANG >= 202002L) && __cpp_lib_remove_cvref >= 201711L
252
253 template <class T> using remove_cvref = std::remove_cvref<T>;
254
255#else
256
257 template <class T> struct remove_cvref
258 {
259 using type = typename std::remove_cv<typename std::remove_reference<T>::type>::type;
260 };
261
262#endif
263
264 /* A partially compliant implementation of C++20's std::bit_cast function contributed
265 by Jesse Towner.
266
267 Our bit_cast is only guaranteed to be constexpr when both the input and output
268 arguments are either integrals or enums. However, this covers most use cases
269 since the vast majority of status_codes have an underlying type that is either
270 an integral or enum. We still attempt a constexpr union-based type pun for non-array
271 input types, which some compilers accept. For array inputs, we fall back to
272 non-constexpr memmove.
273 */
274
275 template <class T> using is_integral_or_enum = std::integral_constant<bool, std::is_integral<T>::value || std::is_enum<T>::value>;
276
277 template <class To, class From> using is_static_castable = std::integral_constant<bool, is_integral_or_enum<To>::value && is_integral_or_enum<From>::value>;
278
279 template <class To, class From>
280 using is_union_castable = std::integral_constant<bool, !is_static_castable<To, From>::value && !std::is_array<To>::value && !std::is_array<From>::value>;
281
282 template <class To, class From>
283 using is_bit_castable =
284 std::integral_constant<bool, sizeof(To) == sizeof(From) && traits::is_move_bitcopying<To>::value && traits::is_move_bitcopying<From>::value>;
285
286 template <class To, class From> union bit_cast_union
287 {
288 From source;
289 To target;
290 };
291
292#if BOOST_OUTCOME_SYSTEM_ERROR2_HAVE_BIT_CAST
293 using std::bit_cast; // available for all trivially copyable types
294
295 // For move bit copying types
296 template <class To, class From>
297 requires(is_bit_castable<To, From>::value //
298 &&is_union_castable<To, From>::value //
299 && (!std::is_trivially_copyable_v<From> //
300 || !std::is_trivially_copyable_v<To>) ) //
301 constexpr To bit_cast(const From &from) noexcept
302 {
303 return bit_cast_union<To, From>{from}.target;
304 }
305 template <class To, class From>
306 requires(is_bit_castable<To, From>::value //
307 && !is_union_castable<To, From>::value //
308 && (!std::is_trivially_copyable_v<From> //
309 || !std::is_trivially_copyable_v<To>) ) //
310 To bit_cast(const From &from)
311 noexcept
312 {
313 bit_cast_union<To, From> ret;
314 memmove(&ret.source, &from, sizeof(ret.source));
315 return ret.target;
316 }
317#else
318 BOOST_OUTCOME_SYSTEM_ERROR2_TEMPLATE(class To, class From, int = 5)
319 BOOST_OUTCOME_SYSTEM_ERROR2_TREQUIRES(BOOST_OUTCOME_SYSTEM_ERROR2_TPRED(is_bit_castable<To, From>::value //
320 &&is_static_castable<To, From>::value //
321 && !is_union_castable<To, From>::value))
322 constexpr To bit_cast(const From &from) noexcept { return static_cast<To>(from); }
323
324#if defined(__GNUC__) && !defined(__clang__)
325#pragma GCC diagnostic push
326#pragma GCC diagnostic ignored "-Wmaybe-uninitialized"
327#endif
328 BOOST_OUTCOME_SYSTEM_ERROR2_TEMPLATE(class To, class From, long = 5)
329 BOOST_OUTCOME_SYSTEM_ERROR2_TREQUIRES(BOOST_OUTCOME_SYSTEM_ERROR2_TPRED(is_bit_castable<To, From>::value //
330 && !is_static_castable<To, From>::value //
331 && is_union_castable<To, From>::value))
332 constexpr To bit_cast(const From &from) noexcept { return bit_cast_union<To, From>{from}.target; }
333#if defined(__GNUC__) && !defined(__clang__)
334#pragma GCC diagnostic pop
335#endif
336
337 BOOST_OUTCOME_SYSTEM_ERROR2_TEMPLATE(class To, class From, short = 5)
338 BOOST_OUTCOME_SYSTEM_ERROR2_TREQUIRES(BOOST_OUTCOME_SYSTEM_ERROR2_TPRED(is_bit_castable<To, From>::value //
339 && !is_static_castable<To, From>::value //
340 && !is_union_castable<To, From>::value))
341 To bit_cast(const From &from) noexcept
342 {
343 bit_cast_union<To, From> ret;
344 memmove(&ret.source, &from, sizeof(ret.source));
345 return ret.target;
346 }
347#endif
348
349 /* erasure_cast performs a bit_cast with additional rules to handle types
350 of differing sizes. For integral & enum types, it may perform a narrowing
351 or widing conversion with static_cast if necessary, before doing the final
352 conversion with bit_cast. When casting to or from non-integral, non-enum
353 types it may insert the value into another object with extra padding bytes
354 to satisfy bit_cast's preconditions that both types have the same size. */
355
356 template <class To, class From>
357 using is_erasure_castable = std::integral_constant<bool, traits::is_move_bitcopying<To>::value && traits::is_move_bitcopying<From>::value>;
358
359 template <class T, bool = std::is_enum<T>::value> struct identity_or_underlying_type
360 {
361 using type = T;
362 };
363 template <class T> struct identity_or_underlying_type<T, true>
364 {
365 using type = typename std::underlying_type<T>::type;
366 };
367
368 template <class OfSize, class OfSign>
369 using erasure_integer_type = typename std::conditional<std::is_signed<typename identity_or_underlying_type<OfSign>::type>::value,
370 typename std::make_signed<typename identity_or_underlying_type<OfSize>::type>::type,
371 typename std::make_unsigned<typename identity_or_underlying_type<OfSize>::type>::type>::type;
372
373 template <class ErasedType, std::size_t N> struct padded_erasure_object
374 {
375 static_assert(traits::is_move_bitcopying<ErasedType>::value, "ErasedType must be TriviallyCopyable or MoveBitcopying");
376 static_assert(alignof(ErasedType) <= sizeof(ErasedType), "ErasedType must not be over-aligned");
377 ErasedType value;
378 char padding[N];
379 constexpr explicit padded_erasure_object(const ErasedType &v) noexcept
380 : value(v)
381 , padding{}
382 {
383 }
384 };
385
386 BOOST_OUTCOME_SYSTEM_ERROR2_TEMPLATE(class To, class From)
387 BOOST_OUTCOME_SYSTEM_ERROR2_TREQUIRES(BOOST_OUTCOME_SYSTEM_ERROR2_TPRED(is_erasure_castable<To, From>::value && (sizeof(To) == sizeof(From))))
388 constexpr To erasure_cast(const From &from) noexcept { return bit_cast<To>(from); }
389
390#if defined(_WIN32) || defined(__APPLE__) || __LITTLE_ENDIAN__ || (defined(__BYTE_ORDER) && defined(__LITTLE_ENDIAN) && __BYTE_ORDER == __LITTLE_ENDIAN)
391 // We can avoid the type pun on little endian architectures which can aid optimisation
392 BOOST_OUTCOME_SYSTEM_ERROR2_TEMPLATE(class To, class From, long = 5)
393 BOOST_OUTCOME_SYSTEM_ERROR2_TREQUIRES(BOOST_OUTCOME_SYSTEM_ERROR2_TPRED(is_erasure_castable<To, From>::value &&is_static_castable<To, From>::value && (sizeof(To) < sizeof(From))))
394 constexpr To erasure_cast(const From &from) noexcept { return static_cast<To>(bit_cast<erasure_integer_type<From, To>>(from)); }
395
396 BOOST_OUTCOME_SYSTEM_ERROR2_TEMPLATE(class To, class From, int = 5)
397 BOOST_OUTCOME_SYSTEM_ERROR2_TREQUIRES(BOOST_OUTCOME_SYSTEM_ERROR2_TPRED(is_erasure_castable<To, From>::value &&is_static_castable<To, From>::value && (sizeof(To) > sizeof(From))))
398 constexpr To erasure_cast(const From &from) noexcept { return bit_cast<To>(static_cast<erasure_integer_type<To, From>>(from)); }
399
400 BOOST_OUTCOME_SYSTEM_ERROR2_TEMPLATE(class To, class From, short = 5)
401 BOOST_OUTCOME_SYSTEM_ERROR2_TREQUIRES(BOOST_OUTCOME_SYSTEM_ERROR2_TPRED(is_erasure_castable<To, From>::value && !is_static_castable<To, From>::value && (sizeof(To) < sizeof(From))))
402 constexpr To erasure_cast(const From &from) noexcept { return bit_cast<padded_erasure_object<To, sizeof(From) - sizeof(To)>>(from).value; }
403
404 BOOST_OUTCOME_SYSTEM_ERROR2_TEMPLATE(class To, class From, char = 5)
405 BOOST_OUTCOME_SYSTEM_ERROR2_TREQUIRES(BOOST_OUTCOME_SYSTEM_ERROR2_TPRED(is_erasure_castable<To, From>::value && !is_static_castable<To, From>::value && (sizeof(To) > sizeof(From))))
406 constexpr To erasure_cast(const From &from) noexcept { return bit_cast<To>(padded_erasure_object<From, sizeof(To) - sizeof(From)>{from}); }
407#else
408 BOOST_OUTCOME_SYSTEM_ERROR2_TEMPLATE(class To, class From, short = 5)
409 BOOST_OUTCOME_SYSTEM_ERROR2_TREQUIRES(BOOST_OUTCOME_SYSTEM_ERROR2_TPRED(is_erasure_castable<To, From>::value && (sizeof(To) < sizeof(From))))
410 constexpr To erasure_cast(const From &from) noexcept { return bit_cast<padded_erasure_object<To, sizeof(From) - sizeof(To)>>(from).value; }
411
412 BOOST_OUTCOME_SYSTEM_ERROR2_TEMPLATE(class To, class From, char = 5)
413 BOOST_OUTCOME_SYSTEM_ERROR2_TREQUIRES(BOOST_OUTCOME_SYSTEM_ERROR2_TPRED(is_erasure_castable<To, From>::value && (sizeof(To) > sizeof(From))))
414 constexpr To erasure_cast(const From &from) noexcept { return bit_cast<To>(padded_erasure_object<From, sizeof(To) - sizeof(From)>{from}); }
415#endif
416} // namespace detail
417BOOST_OUTCOME_SYSTEM_ERROR2_NAMESPACE_END
418
419#ifndef BOOST_OUTCOME_SYSTEM_ERROR2_FATAL
420#ifdef BOOST_OUTCOME_SYSTEM_ERROR2_NOT_POSIX
421#error If BOOST_OUTCOME_SYSTEM_ERROR2_NOT_POSIX is defined, you must define your own BOOST_OUTCOME_SYSTEM_ERROR2_FATAL implementation!
422#endif
423#include <cstdlib> // for abort
424#ifdef __APPLE__
425#include <unistd.h> // for write
426#endif
427
428BOOST_OUTCOME_SYSTEM_ERROR2_NAMESPACE_BEGIN
429namespace detail
430{
431 namespace avoid_stdio_include
432 {
433#if !defined(__APPLE__) && !defined(_MSC_VER)
434 extern "C" ptrdiff_t write(int, const void *, size_t);
435#elif defined(_MSC_VER)
436 extern ptrdiff_t write(int, const void *, size_t);
437#if(defined(__x86_64__) || defined(_M_X64)) || (defined(__aarch64__) || defined(_M_ARM64)) || (defined(__arm__) || defined(_M_ARM))
438#pragma comment(linker, "/alternatename:?write@avoid_stdio_include@detail@system_error2@@YA_JHPEBX_K@Z=write")
439#elif defined(__x86__) || defined(_M_IX86) || defined(__i386__)
440#pragma comment(linker, "/alternatename:?write@avoid_stdio_include@detail@system_error2@@YAHHPBXI@Z=_write")
441#else
442#error Unknown architecture
443#endif
444#endif
445 } // namespace avoid_stdio_include
446 inline void do_fatal_exit(const char *msg)
447 {
448 using namespace avoid_stdio_include;
449 write(2 /*stderr*/, msg, cstrlen(str: msg));
450 write(2 /*stderr*/, "\n", 1);
451 abort();
452 }
453} // namespace detail
454BOOST_OUTCOME_SYSTEM_ERROR2_NAMESPACE_END
455//! Prints msg to stderr, and calls `std::terminate()`. Can be overriden via predefinition.
456#define BOOST_OUTCOME_SYSTEM_ERROR2_FATAL(msg) ::BOOST_OUTCOME_SYSTEM_ERROR2_NAMESPACE::detail::do_fatal_exit(msg)
457#endif
458
459#endif
460

source code of boost/libs/outcome/include/boost/outcome/experimental/status-code/config.hpp