libstdc++: generator Source File

libstdc++

generator
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1// <generator> -*- C++ -*-
2
3// Copyright (C) 2023-2026 Free Software Foundation, Inc.
4//
5// This file is part of the GNU ISO C++ Library. This library is free
6// software; you can redistribute it and/or modify it under the
7// terms of the GNU General Public License as published by the
8// Free Software Foundation; either version 3, or (at your option)
9// any later version.
10
11// This library is distributed in the hope that it will be useful,
12// but WITHOUT ANY WARRANTY; without even the implied warranty of
13// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14// GNU General Public License for more details.
15
16// Under Section 7 of GPL version 3, you are granted additional
17// permissions described in the GCC Runtime Library Exception, version
18// 3.1, as published by the Free Software Foundation.
19
20// You should have received a copy of the GNU General Public License and
21// a copy of the GCC Runtime Library Exception along with this program;
22// see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
23// <http://www.gnu.org/licenses/>.
24
25/** @file include/generator
26 * This is a Standard C++ Library header.
27 */
28
29#ifndef _GLIBCXX_GENERATOR
30#define _GLIBCXX_GENERATOR
31
32#include <ranges>
33#ifdef _GLIBCXX_SYSHDR
34#pragma GCC system_header
35#endif
36
37#include <bits/c++config.h>
38
39#define __glibcxx_want_generator
40#include <bits/version.h>
41
42#ifdef __cpp_lib_generator // C++ >= 23 && __glibcxx_coroutine
43#include <new>
44#include <bits/move.h>
45#include <bits/ranges_util.h>
46#include <bits/elements_of.h>
47#include <bits/uses_allocator.h>
48#include <bits/exception_ptr.h>
49#include <cstddef>
50#include <cstdint>
51#include <cstring>
52#include <coroutine>
53
54#include <type_traits>
55#include <variant>
56#include <concepts>
57
58#if _GLIBCXX_HOSTED
59# include <bits/memory_resource.h>
60#endif // HOSTED
61
62namespace std _GLIBCXX_VISIBILITY(default)
63{
64_GLIBCXX_BEGIN_NAMESPACE_VERSION
65
66 /**
67 * @defgroup generator_coros Range generator coroutines
68 * @addtogroup ranges
69 * @since C++23
70 * @{
71 */
72
73 /** @brief A range specified using a yielding coroutine.
74 *
75 * `std::generator` is a utility class for defining ranges using coroutines
76 * that yield elements as a range. Generator coroutines are synchronous.
77 *
78 * @headerfile generator
79 * @since C++23
80 */
81 template<typename _Ref, typename _Val = void, typename _Alloc = void>
82 class generator;
83
84 /// @cond undocumented
85 namespace __gen
86 {
87 /// _Reference type for a generator whose reference (first argument) and
88 /// value (second argument) types are _Ref and _Val.
89 template<typename _Ref, typename _Val>
90 using _Reference_t = __conditional_t<is_void_v<_Val>,
91 _Ref&&, _Ref>;
92
93 /// Type yielded by a generator whose _Reference type is _Reference.
94 template<typename _Reference>
95 using _Yield_t = __conditional_t<is_reference_v<_Reference>,
96 _Reference,
97 const _Reference&>;
98
99 /// _Yield_t * _Reference_t
100 template<typename _Ref, typename _Val>
101 using _Yield2_t = _Yield_t<_Reference_t<_Ref, _Val>>;
102
103 template<typename> constexpr bool __is_generator = false;
104 template<typename _Val, typename _Ref, typename _Alloc>
105 constexpr bool __is_generator<std::generator<_Val, _Ref, _Alloc>> = true;
106
107 /// Allocator and value type erased generator promise type.
108 /// \tparam _Yielded The corresponding generators yielded type.
109 template<typename _Yielded>
110 class _Promise_erased
111 {
112 static_assert(is_reference_v<_Yielded>);
113 using _Yielded_deref = remove_reference_t<_Yielded>;
114 using _Yielded_decvref = remove_cvref_t<_Yielded>;
115 using _ValuePtr = add_pointer_t<_Yielded>;
116 using _Coro_handle = std::coroutine_handle<_Promise_erased>;
117
118 template<typename, typename, typename>
119 friend class std::generator;
120
121 template<typename _Gen>
122 struct _Recursive_awaiter;
123 template<typename>
124 friend struct _Recursive_awaiter;
125 struct _Copy_awaiter;
126 struct _Subyield_state;
127 struct _Final_awaiter;
128 public:
129 suspend_always
130 initial_suspend() const noexcept
131 { return {}; }
132
133 suspend_always
134 yield_value(_Yielded __val) noexcept
135 {
136 _M_bottom_value() = ::std::addressof(__val);
137 return {};
138 }
139
140 auto
141 yield_value(const _Yielded_deref& __val)
142 noexcept (is_nothrow_constructible_v<_Yielded_decvref,
143 const _Yielded_deref&>)
144 requires (is_rvalue_reference_v<_Yielded>
145 && constructible_from<_Yielded_decvref,
146 const _Yielded_deref&>)
147 { return _Copy_awaiter(_Yielded_decvref(__val), _M_bottom_value()); }
148
149 template<typename _R2, typename _V2, typename _A2, typename _U2>
150 requires std::same_as<_Yield2_t<_R2, _V2>, _Yielded>
151 auto
152 yield_value(ranges::elements_of<generator<_R2, _V2, _A2>&&, _U2> __r)
153 noexcept
154 { return _Recursive_awaiter { std::move(__r.range) }; }
155
156 // _GLIBCXX_RESOLVE_LIB_DEFECTS
157 // 3899. co_yielding elements of an lvalue generator is
158 // unnecessarily inefficient
159 template<typename _R2, typename _V2, typename _A2, typename _U2>
160 requires std::same_as<_Yield2_t<_R2, _V2>, _Yielded>
161 auto
162 yield_value(ranges::elements_of<generator<_R2, _V2, _A2>&, _U2> __r)
163 noexcept
164 { return _Recursive_awaiter { std::move(__r.range) }; }
165
166 template<ranges::input_range _R, typename _Alloc>
167 requires convertible_to<ranges::range_reference_t<_R>, _Yielded>
168 auto
169 yield_value(ranges::elements_of<_R, _Alloc> __r)
170 {
171 auto __n = [] (allocator_arg_t, _Alloc,
172 ranges::iterator_t<_R> __i,
173 ranges::sentinel_t<_R> __s)
174 -> generator<_Yielded, ranges::range_value_t<_R>, _Alloc> {
175 for (; __i != __s; ++__i)
176 co_yield static_cast<_Yielded>(*__i);
177 };
178 return yield_value(ranges::elements_of(__n(allocator_arg,
179 __r.allocator,
180 ranges::begin(__r.range),
181 ranges::end(__r.range))));
182 }
183
184
185 _Final_awaiter
186 final_suspend() noexcept
187 { return {}; }
188
189 void
190 unhandled_exception()
191 {
192 // To get to this point, this coroutine must have been active. In that
193 // case, it must be the top of the stack. The current coroutine is
194 // the sole entry of the stack iff it is both the top and the bottom. As
195 // it is the top implicitly in this context it will be the sole entry iff
196 // it is the bottom.
197 if (_M_nest._M_is_bottom())
198 throw;
199 else
200 this->_M_except = std::current_exception();
201 }
202
203 void await_transform() = delete;
204 void return_void() const noexcept {}
205
206 private:
207 _ValuePtr&
208 _M_bottom_value() noexcept
209 { return _M_nest._M_bottom_value(*this); }
210
211 _ValuePtr&
212 _M_value() noexcept
213 { return _M_nest._M_value(*this); }
214
215 _Subyield_state _M_nest;
216 std::exception_ptr _M_except;
217 };
218
219 template<typename _Yielded>
220 struct _Promise_erased<_Yielded>::_Subyield_state
221 {
222 struct _Frame
223 {
224 _Coro_handle _M_bottom;
225 _Coro_handle _M_parent;
226 };
227
228 struct _Bottom_frame
229 {
230 _Coro_handle _M_top;
231 _ValuePtr _M_value = nullptr;
232 };
233
234 std::variant<
235 _Bottom_frame,
236 _Frame
237 > _M_stack;
238
239 bool
240 _M_is_bottom() const noexcept
241 { return !std::holds_alternative<_Frame>(this->_M_stack); }
242
243 _Coro_handle&
244 _M_top() noexcept
245 {
246 if (auto __f = std::get_if<_Frame>(&this->_M_stack))
247 return __f->_M_bottom.promise()._M_nest._M_top();
248
249 auto __bf = std::get_if<_Bottom_frame>(&this->_M_stack);
250 __glibcxx_assert(__bf);
251 return __bf->_M_top;
252 }
253
254 void
255 _M_push(_Coro_handle __current, _Coro_handle __subyield) noexcept
256 {
257 __glibcxx_assert(&__current.promise()._M_nest == this);
258 __glibcxx_assert(this->_M_top() == __current);
259
260 __subyield.promise()._M_nest._M_jump_in(__current, __subyield);
261 }
262
263 std::coroutine_handle<>
264 _M_pop() noexcept
265 {
266 if (auto __f = std::get_if<_Frame>(&this->_M_stack))
267 {
268 // We aren't a bottom coroutine. Restore the parent to the top
269 // and resume.
270 auto __p = this->_M_top() = __f->_M_parent;
271 return __p;
272 }
273 else
274 // Otherwise, there's nothing to resume.
275 return std::noop_coroutine();
276 }
277
278 void
279 _M_jump_in(_Coro_handle __rest, _Coro_handle __new) noexcept
280 {
281 __glibcxx_assert(&__new.promise()._M_nest == this);
282 __glibcxx_assert(this->_M_is_bottom());
283 // We're bottom. We're also top if top is unset (note that this is
284 // not true if something was added to the coro stack and then popped,
285 // but in that case we can't possibly be yielded from, as it would
286 // require rerunning begin()).
287 __glibcxx_assert(!this->_M_top());
288
289 auto& __rn = __rest.promise()._M_nest;
290 __rn._M_top() = __new;
291
292 // Presume we're the second frame...
293 auto __bott = __rest;
294 if (auto __f = std::get_if<_Frame>(&__rn._M_stack))
295 // But, if we aren't, get the actual bottom. We're only the second
296 // frame if our parent is the bottom frame, i.e. it doesn't have a
297 // _Frame member.
298 __bott = __f->_M_bottom;
299
300 this->_M_stack = _Frame {
301 ._M_bottom = __bott,
302 ._M_parent = __rest
303 };
304 }
305
306 _ValuePtr&
307 _M_bottom_value(_Promise_erased& __current) noexcept
308 {
309 __glibcxx_assert(&__current._M_nest == this);
310 if (auto __bf = std::get_if<_Bottom_frame>(&this->_M_stack))
311 return __bf->_M_value;
312 auto __f = std::get_if<_Frame>(&this->_M_stack);
313 __glibcxx_assert(__f);
314 auto& __p = __f->_M_bottom.promise();
315 return __p._M_nest._M_value(__p);
316 }
317
318 _ValuePtr&
319 _M_value(_Promise_erased& __current) noexcept
320 {
321 __glibcxx_assert(&__current._M_nest == this);
322 auto __bf = std::get_if<_Bottom_frame>(&this->_M_stack);
323 __glibcxx_assert(__bf);
324 return __bf->_M_value;
325 }
326 };
327
328 template<typename _Yielded>
329 struct _Promise_erased<_Yielded>::_Final_awaiter
330 {
331 bool await_ready() noexcept
332 { return false; }
333
334 template<typename _Promise>
335 auto await_suspend(std::coroutine_handle<_Promise> __c) noexcept
336 {
337#ifdef __glibcxx_is_pointer_interconvertible
338 static_assert(is_pointer_interconvertible_base_of_v<
339 _Promise_erased, _Promise>);
340#endif
341
342 auto& __n = __c.promise()._M_nest;
343 return __n._M_pop();
344 }
345
346 void await_resume() noexcept {}
347 };
348
349 template<typename _Yielded>
350 struct _Promise_erased<_Yielded>::_Copy_awaiter
351 {
352 _Yielded_decvref _M_value;
353 _ValuePtr& _M_bottom_value;
354
355 constexpr bool await_ready() noexcept
356 { return false; }
357
358 template<typename _Promise>
359 void await_suspend(std::coroutine_handle<_Promise>) noexcept
360 {
361#ifdef __glibcxx_is_pointer_interconvertible
362 static_assert(is_pointer_interconvertible_base_of_v<
363 _Promise_erased, _Promise>);
364#endif
365 _M_bottom_value = ::std::addressof(_M_value);
366 }
367
368 constexpr void
369 await_resume() const noexcept
370 {}
371 };
372
373 template<typename _Yielded>
374 template<typename _Gen>
375 struct _Promise_erased<_Yielded>::_Recursive_awaiter
376 {
377 _Gen _M_gen;
378 static_assert(__is_generator<_Gen>);
379 static_assert(std::same_as<typename _Gen::yielded, _Yielded>);
380
381 _Recursive_awaiter(_Gen __gen) noexcept
382 : _M_gen(std::move(__gen))
383 { this->_M_gen._M_mark_as_started(); }
384
385 constexpr bool
386 await_ready() const noexcept
387 { return false; }
388
389
390 template<typename _Promise>
391 std::coroutine_handle<>
392 await_suspend(std::coroutine_handle<_Promise> __p) noexcept
393 {
394#ifdef __glibcxx_is_pointer_interconvertible
395 static_assert(is_pointer_interconvertible_base_of_v<
396 _Promise_erased, _Promise>);
397#endif
398
399 auto __c = _Coro_handle::from_address(__p.address());
400 auto __t = _Coro_handle::from_address(this->_M_gen._M_coro.address());
401 __p.promise()._M_nest._M_push(__c, __t);
402 return __t;
403 }
404
405 void await_resume()
406 {
407 if (auto __e = _M_gen._M_coro.promise()._M_except)
408 std::rethrow_exception(__e);
409 }
410 };
411
412 struct _Alloc_block
413 {
414 alignas(__STDCPP_DEFAULT_NEW_ALIGNMENT__)
415 char _M_data[__STDCPP_DEFAULT_NEW_ALIGNMENT__];
416
417 static auto
418 _M_cnt(std::size_t __sz) noexcept
419 {
420 auto __blksz = sizeof(_Alloc_block);
421 return (__sz + __blksz - 1) / __blksz;
422 }
423 };
424
425 template<typename _All>
426 concept _Stateless_alloc
427 = default_initializable<_All>
428 && allocator_traits<_All>::is_always_equal::value;
429
430 template<typename _Allocator>
431 class _Promise_alloc
432 {
433 using _Rebound = __alloc_rebind<_Allocator, _Alloc_block>;
434 using _Rebound_ATr = allocator_traits<_Rebound>;
435 static_assert(is_pointer_v<typename _Rebound_ATr::pointer>,
436 "Must use allocators for true pointers with generators");
437
438 static auto
439 _M_alloc_address(std::uintptr_t __fn, std::uintptr_t __fsz) noexcept
440 {
441 auto __an = __fn + __fsz;
442 auto __ba = alignof(_Rebound);
443 return reinterpret_cast<_Rebound*>(((__an + __ba - 1) / __ba) * __ba);
444 }
445
446 static auto
447 _M_alloc_size(std::size_t __csz) noexcept
448 {
449 auto __ba = alignof(_Rebound);
450 // Our desired layout is placing the coroutine frame, then pad out to
451 // align, then place the allocator. The total size of that is the
452 // size of the coroutine frame, plus up to __ba bytes, plus the size
453 // of the allocator.
454 return __csz + __ba + sizeof(_Rebound);
455 }
456
457 static void*
458 _M_allocate(_Rebound __b, std::size_t __csz)
459 {
460 if constexpr (_Stateless_alloc<_Rebound>)
461 // Only need room for the coroutine.
462 return __b.allocate(_Alloc_block::_M_cnt(__csz));
463 else
464 {
465 auto __nsz = _Alloc_block::_M_cnt(_M_alloc_size(__csz));
466 auto __f = __b.allocate(__nsz);
467 auto __fn = reinterpret_cast<std::uintptr_t>(__f);
468 auto __an = _M_alloc_address(__fn, __csz);
469 ::new (__an) _Rebound(std::move(__b));
470 return __f;
471 }
472 }
473
474 public:
475 void*
476 operator new(std::size_t __sz)
477 requires default_initializable<_Rebound> // _Allocator is non-void
478 { return _M_allocate({}, __sz); }
479
480 // _GLIBCXX_RESOLVE_LIB_DEFECTS
481 // 3900. The allocator_arg_t overloads of promise_type::operator new
482 // should not be constrained
483 template<typename _Alloc, typename... _Args>
484 void*
485 operator new(std::size_t __sz,
486 allocator_arg_t, const _Alloc& __a,
487 const _Args&...)
488 {
489 static_assert(convertible_to<const _Alloc&, _Allocator>,
490 "the allocator argument to the coroutine must be "
491 "convertible to the generator's allocator type");
492 return _M_allocate(_Rebound(_Allocator(__a)), __sz);
493 }
494
495 template<typename _This, typename _Alloc, typename... _Args>
496 void*
497 operator new(std::size_t __sz,
498 const _This&,
499 allocator_arg_t, const _Alloc& __a,
500 const _Args&...)
501 {
502 static_assert(convertible_to<const _Alloc&, _Allocator>,
503 "the allocator argument to the coroutine must be "
504 "convertible to the generator's allocator type");
505 return _M_allocate(_Rebound(_Allocator(__a)), __sz);
506 }
507
508 void
509 operator delete(void* __ptr, std::size_t __csz) noexcept
510 {
511 if constexpr (_Stateless_alloc<_Rebound>)
512 {
513 _Rebound __b;
514 return __b.deallocate(reinterpret_cast<_Alloc_block*>(__ptr),
515 _Alloc_block::_M_cnt(__csz));
516 }
517 else
518 {
519 auto __nsz = _Alloc_block::_M_cnt(_M_alloc_size(__csz));
520 auto __fn = reinterpret_cast<std::uintptr_t>(__ptr);
521 auto __an = _M_alloc_address(__fn, __csz);
522 _Rebound __b(std::move(*__an));
523 __an->~_Rebound();
524 __b.deallocate(reinterpret_cast<_Alloc_block*>(__ptr), __nsz);
525 }
526 }
527 };
528
529 template<>
530 class _Promise_alloc<void>
531 {
532 using _Dealloc_fn = void (*)(void*, std::size_t);
533
534 static auto
535 _M_dealloc_address(std::uintptr_t __fn, std::uintptr_t __fsz) noexcept
536 {
537 auto __an = __fn + __fsz;
538 auto __ba = alignof(_Dealloc_fn);
539 auto __aligned = ((__an + __ba - 1) / __ba) * __ba;
540 return reinterpret_cast<_Dealloc_fn*>(__aligned);
541 }
542
543 template<typename _Rebound>
544 static auto
545 _M_alloc_address(std::uintptr_t __fn, std::uintptr_t __fsz) noexcept
546 requires (!_Stateless_alloc<_Rebound>)
547 {
548 auto __ba = alignof(_Rebound);
549 auto __da = _M_dealloc_address(__fn, __fsz);
550 auto __aan = reinterpret_cast<std::uintptr_t>(__da);
551 __aan += sizeof(_Dealloc_fn);
552 auto __aligned = ((__aan + __ba - 1) / __ba) * __ba;
553 return reinterpret_cast<_Rebound*>(__aligned);
554 }
555
556 template<typename _Rebound>
557 static auto
558 _M_alloc_size(std::size_t __csz) noexcept
559 {
560 // This time, we want the coroutine frame, then the deallocator
561 // pointer, then the allocator itself, if any.
562 std::size_t __aa = 0;
563 std::size_t __as = 0;
564 if constexpr (!std::same_as<_Rebound, void>)
565 {
566 __aa = alignof(_Rebound);
567 __as = sizeof(_Rebound);
568 }
569 auto __ba = __aa + alignof(_Dealloc_fn);
570 return __csz + __ba + __as + sizeof(_Dealloc_fn);
571 }
572
573 template<typename _Rebound>
574 static void
575 _M_deallocator(void* __ptr, std::size_t __csz) noexcept
576 {
577 auto __asz = _M_alloc_size<_Rebound>(__csz);
578 auto __nblk = _Alloc_block::_M_cnt(__asz);
579
580 if constexpr (_Stateless_alloc<_Rebound>)
581 {
582 _Rebound __b;
583 __b.deallocate(reinterpret_cast<_Alloc_block*>(__ptr), __nblk);
584 }
585 else
586 {
587 auto __fn = reinterpret_cast<std::uintptr_t>(__ptr);
588 auto __an = _M_alloc_address<_Rebound>(__fn, __csz);
589 _Rebound __b(std::move(*__an));
590 __an->~_Rebound();
591 __b.deallocate(reinterpret_cast<_Alloc_block*>(__ptr), __nblk);
592 }
593 }
594
595 template<typename _Alloc>
596 static void*
597 _M_allocate(const _Alloc& __a, std::size_t __csz)
598 {
599 using _Rebound = __alloc_rebind<_Alloc, _Alloc_block>;
600 using _Rebound_ATr = allocator_traits<_Rebound>;
601
602 static_assert(is_pointer_v<typename _Rebound_ATr::pointer>,
603 "Must use allocators for true pointers with generators");
604
605 _Dealloc_fn __d = &_M_deallocator<_Rebound>;
606 auto __b = static_cast<_Rebound>(__a);
607 auto __asz = _M_alloc_size<_Rebound>(__csz);
608 auto __nblk = _Alloc_block::_M_cnt(__asz);
609 void* __p = __b.allocate(__nblk);
610 auto __pn = reinterpret_cast<std::uintptr_t>(__p);
611 *_M_dealloc_address(__pn, __csz) = __d;
612 if constexpr (!_Stateless_alloc<_Rebound>)
613 {
614 auto __an = _M_alloc_address<_Rebound>(__pn, __csz);
615 ::new (__an) _Rebound(std::move(__b));
616 }
617 return __p;
618 }
619 public:
620 void*
621 operator new(std::size_t __sz)
622 {
623 auto __nsz = _M_alloc_size<void>(__sz);
624 _Dealloc_fn __d = [] (void* __ptr, std::size_t __sz)
625 {
626 ::operator delete(__ptr, _M_alloc_size<void>(__sz));
627 };
628 auto __p = ::operator new(__nsz);
629 auto __pn = reinterpret_cast<uintptr_t>(__p);
630 *_M_dealloc_address(__pn, __sz) = __d;
631 return __p;
632 }
633
634 template<typename _Alloc, typename... _Args>
635 void*
636 operator new(std::size_t __sz,
637 allocator_arg_t, const _Alloc& __a,
638 const _Args&...)
639 { return _M_allocate(__a, __sz); }
640
641 template<typename _This, typename _Alloc, typename... _Args>
642 void*
643 operator new(std::size_t __sz,
644 const _This&,
645 allocator_arg_t, const _Alloc& __a,
646 const _Args&...)
647 { return _M_allocate(__a, __sz); }
648
649 void
650 operator delete(void* __ptr, std::size_t __sz) noexcept
651 {
652 _Dealloc_fn __d;
653 auto __pn = reinterpret_cast<uintptr_t>(__ptr);
654 __d = *_M_dealloc_address(__pn, __sz);
655 __d(__ptr, __sz);
656 }
657 };
658
659 template<typename _Tp>
660 concept _Cv_unqualified_object = is_object_v<_Tp>
661 && same_as<_Tp, remove_cv_t<_Tp>>;
662 } // namespace __gen
663 /// @endcond
664
665 template<typename _Ref, typename _Val, typename _Alloc>
666 class generator
667 : public ranges::view_interface<generator<_Ref, _Val, _Alloc>>
668 {
669 using _Value = __conditional_t<is_void_v<_Val>,
670 remove_cvref_t<_Ref>,
671 _Val>;
672 static_assert(__gen::_Cv_unqualified_object<_Value>,
673 "Generator value must be a cv-unqualified object type");
674 using _Reference = __gen::_Reference_t<_Ref, _Val>;
675 static_assert(is_reference_v<_Reference>
676 || (__gen::_Cv_unqualified_object<_Reference>
677 && copy_constructible<_Reference>),
678 "Generator reference type must be either a cv-unqualified "
679 "object type that is trivially constructible or a "
680 "reference type");
681
682 using _RRef = __conditional_t<
683 is_reference_v<_Reference>,
684 remove_reference_t<_Reference>&&,
685 _Reference>;
686
687 /* Required to model indirectly_readable, and input_iterator. */
688 static_assert(common_reference_with<_Reference&&, _Value&&>);
689 static_assert(common_reference_with<_Reference&&, _RRef&&>);
690 static_assert(common_reference_with<_RRef&&, const _Value&>);
691
692 using _Yielded = __gen::_Yield_t<_Reference>;
693 using _Erased_promise = __gen::_Promise_erased<_Yielded>;
694
695 struct _Iterator;
696
697 friend _Erased_promise;
698 friend struct _Erased_promise::_Subyield_state;
699 public:
700 using yielded = _Yielded;
701
702 struct promise_type : _Erased_promise, __gen::_Promise_alloc<_Alloc>
703 {
704 generator get_return_object() noexcept
705 { return { coroutine_handle<promise_type>::from_promise(*this) }; }
706 };
707
708#ifdef __glibcxx_is_pointer_interconvertible
709 static_assert(is_pointer_interconvertible_base_of_v<_Erased_promise,
710 promise_type>);
711#endif
712
713 generator(const generator&) = delete;
714
715 generator(generator&& __other) noexcept
716 : _M_coro(std::__exchange(__other._M_coro, nullptr)),
717 _M_began(std::__exchange(__other._M_began, false))
718 {}
719
720 ~generator()
721 {
722 if (auto& __c = this->_M_coro)
723 __c.destroy();
724 }
725
726 generator&
727 operator=(generator __other) noexcept
728 {
729 swap(__other._M_coro, this->_M_coro);
730 swap(__other._M_began, this->_M_began);
731 return *this;
732 }
733
734 _Iterator
735 begin()
736 {
737 this->_M_mark_as_started();
738 auto __h = _Coro_handle::from_promise(_M_coro.promise());
739 __h.promise()._M_nest._M_top() = __h;
740 return { __h };
741 }
742
743 default_sentinel_t
744 end() const noexcept
745 { return default_sentinel; }
746
747 private:
748 using _Coro_handle = std::coroutine_handle<_Erased_promise>;
749
750 generator(coroutine_handle<promise_type> __coro) noexcept
751 : _M_coro { move(__coro) }
752 {}
753
754 void
755 _M_mark_as_started() noexcept
756 {
757 __glibcxx_assert(!this->_M_began);
758 this->_M_began = true;
759 }
760
761 coroutine_handle<promise_type> _M_coro;
762 bool _M_began = false;
763 };
764
765 template<class _Ref, class _Val, class _Alloc>
766 struct generator<_Ref, _Val, _Alloc>::_Iterator
767 {
768 using value_type = _Value;
769 using difference_type = ptrdiff_t;
770
771 friend bool
772 operator==(const _Iterator& __i, default_sentinel_t) noexcept
773 { return __i._M_coro.done(); }
774
775 friend class generator;
776
777 _Iterator(_Iterator&& __o) noexcept
778 : _M_coro(std::__exchange(__o._M_coro, {}))
779 {}
780
781 _Iterator&
782 operator=(_Iterator&& __o) noexcept
783 {
784 this->_M_coro = std::__exchange(__o._M_coro, {});
785 return *this;
786 }
787
788 _Iterator&
789 operator++()
790 {
791 _M_next();
792 return *this;
793 }
794
795 void
796 operator++(int)
797 { this->operator++(); }
798
799 _Reference
800 operator*()
801 const noexcept(is_nothrow_move_constructible_v<_Reference>)
802 {
803 auto& __p = this->_M_coro.promise();
804 return static_cast<_Reference>(*__p._M_value());
805 }
806
807 private:
808 friend class generator;
809
810 _Iterator(_Coro_handle __g)
811 : _M_coro { __g }
812 { this->_M_next(); }
813
814 void _M_next()
815 {
816 auto& __t = this->_M_coro.promise()._M_nest._M_top();
817 __t.resume();
818 }
819
820 _Coro_handle _M_coro;
821 };
822
823 /// @}
824
825#if _GLIBCXX_HOSTED
826 namespace pmr {
827 template<typename _Ref, typename _Val = void>
828 using generator = std::generator<_Ref, _Val, polymorphic_allocator<std::byte>>;
829 }
830#endif // HOSTED
831
832_GLIBCXX_END_NAMESPACE_VERSION
833} // namespace std
834#endif // __cpp_lib_generator
835
836#endif // _GLIBCXX_GENERATOR
new
concepts
ranges
type_traits
variant
cstddef
cstdint
cstring
move.h
ranges_util.h
version.h
memory_resource.h
exception_ptr.h
c++config.h
std::operator*
constexpr complex< _Tp > operator*(const complex< _Tp > &__x, const complex< _Tp > &__y)
Return new complex value x times y.
Definition complex:434
std::is_pointer_interconvertible_base_of_v
constexpr bool is_pointer_interconvertible_base_of_v
Definition type_traits:4080
std::addressof
constexpr _Tp * addressof(_Tp &__r) noexcept
Returns the actual address of the object or function referenced by r, even in the presence of an over...
Definition move.h:176
std::move
constexpr std::remove_reference< _Tp >::type && move(_Tp &&__t) noexcept
Convert a value to an rvalue.
Definition move.h:138
std::current_exception
exception_ptr current_exception() noexcept
std::rethrow_exception
void rethrow_exception(exception_ptr)
Throw the object pointed to by the exception_ptr.
std
ISO C++ entities toplevel namespace is std.
std::default_sentinel
constexpr default_sentinel_t default_sentinel
A default sentinel value.
Definition iterator_concepts.h:63
std::ranges::view_interface
The ranges::view_interface class template.
Definition ranges_util.h:71