1// Output streams -*- C++ -*-
2
3// Copyright (C) 1997-2022 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/ostream
26 * This is a Standard C++ Library header.
27 */
28
29//
30// ISO C++ 14882: 27.6.2 Output streams
31//
32
33#ifndef _GLIBCXX_OSTREAM
34#define _GLIBCXX_OSTREAM 1
35
36#pragma GCC system_header
37
38#include <ios>
39#include <bits/ostream_insert.h>
40
41namespace std _GLIBCXX_VISIBILITY(default)
42{
43_GLIBCXX_BEGIN_NAMESPACE_VERSION
44
45 /**
46 * @brief Template class basic_ostream.
47 * @ingroup io
48 *
49 * @tparam _CharT Type of character stream.
50 * @tparam _Traits Traits for character type, defaults to
51 * char_traits<_CharT>.
52 *
53 * This is the base class for all output streams. It provides text
54 * formatting of all builtin types, and communicates with any class
55 * derived from basic_streambuf to do the actual output.
56 */
57 template<typename _CharT, typename _Traits>
58 class basic_ostream : virtual public basic_ios<_CharT, _Traits>
59 {
60 public:
61 // Types (inherited from basic_ios):
62 typedef _CharT char_type;
63 typedef typename _Traits::int_type int_type;
64 typedef typename _Traits::pos_type pos_type;
65 typedef typename _Traits::off_type off_type;
66 typedef _Traits traits_type;
67
68 // Non-standard Types:
69 typedef basic_streambuf<_CharT, _Traits> __streambuf_type;
70 typedef basic_ios<_CharT, _Traits> __ios_type;
71 typedef basic_ostream<_CharT, _Traits> __ostream_type;
72 typedef num_put<_CharT, ostreambuf_iterator<_CharT, _Traits> >
73 __num_put_type;
74 typedef ctype<_CharT> __ctype_type;
75
76 /**
77 * @brief Base constructor.
78 *
79 * This ctor is almost never called by the user directly, rather from
80 * derived classes' initialization lists, which pass a pointer to
81 * their own stream buffer.
82 */
83 explicit
84 basic_ostream(__streambuf_type* __sb)
85 { this->init(__sb); }
86
87 /**
88 * @brief Base destructor.
89 *
90 * This does very little apart from providing a virtual base dtor.
91 */
92 virtual
93 ~basic_ostream() { }
94
95 /// Safe prefix/suffix operations.
96 class sentry;
97 friend class sentry;
98
99 ///@{
100 /**
101 * @brief Interface for manipulators.
102 *
103 * Manipulators such as @c std::endl and @c std::hex use these
104 * functions in constructs like "std::cout << std::endl". For more
105 * information, see the iomanip header.
106 */
107 __ostream_type&
108 operator<<(__ostream_type& (*__pf)(__ostream_type&))
109 {
110 // _GLIBCXX_RESOLVE_LIB_DEFECTS
111 // DR 60. What is a formatted input function?
112 // The inserters for manipulators are *not* formatted output functions.
113 return __pf(*this);
114 }
115
116 __ostream_type&
117 operator<<(__ios_type& (*__pf)(__ios_type&))
118 {
119 // _GLIBCXX_RESOLVE_LIB_DEFECTS
120 // DR 60. What is a formatted input function?
121 // The inserters for manipulators are *not* formatted output functions.
122 __pf(*this);
123 return *this;
124 }
125
126 __ostream_type&
127 operator<<(ios_base& (*__pf) (ios_base&))
128 {
129 // _GLIBCXX_RESOLVE_LIB_DEFECTS
130 // DR 60. What is a formatted input function?
131 // The inserters for manipulators are *not* formatted output functions.
132 __pf(*this);
133 return *this;
134 }
135 ///@}
136
137 ///@{
138 /**
139 * @name Inserters
140 *
141 * All the @c operator<< functions (aka <em>formatted output
142 * functions</em>) have some common behavior. Each starts by
143 * constructing a temporary object of type std::basic_ostream::sentry.
144 * This can have several effects, concluding with the setting of a
145 * status flag; see the sentry documentation for more.
146 *
147 * If the sentry status is good, the function tries to generate
148 * whatever data is appropriate for the type of the argument.
149 *
150 * If an exception is thrown during insertion, ios_base::badbit
151 * will be turned on in the stream's error state without causing an
152 * ios_base::failure to be thrown. The original exception will then
153 * be rethrown.
154 */
155
156 ///@{
157 /**
158 * @brief Integer arithmetic inserters
159 * @param __n A variable of builtin integral type.
160 * @return @c *this if successful
161 *
162 * These functions use the stream's current locale (specifically, the
163 * @c num_get facet) to perform numeric formatting.
164 */
165 __ostream_type&
166 operator<<(long __n)
167 { return _M_insert(__n); }
168
169 __ostream_type&
170 operator<<(unsigned long __n)
171 { return _M_insert(__n); }
172
173 __ostream_type&
174 operator<<(bool __n)
175 { return _M_insert(__n); }
176
177 __ostream_type&
178 operator<<(short __n);
179
180 __ostream_type&
181 operator<<(unsigned short __n)
182 {
183 // _GLIBCXX_RESOLVE_LIB_DEFECTS
184 // 117. basic_ostream uses nonexistent num_put member functions.
185 return _M_insert(static_cast<unsigned long>(__n));
186 }
187
188 __ostream_type&
189 operator<<(int __n);
190
191 __ostream_type&
192 operator<<(unsigned int __n)
193 {
194 // _GLIBCXX_RESOLVE_LIB_DEFECTS
195 // 117. basic_ostream uses nonexistent num_put member functions.
196 return _M_insert(static_cast<unsigned long>(__n));
197 }
198
199#ifdef _GLIBCXX_USE_LONG_LONG
200 __ostream_type&
201 operator<<(long long __n)
202 { return _M_insert(__n); }
203
204 __ostream_type&
205 operator<<(unsigned long long __n)
206 { return _M_insert(__n); }
207#endif
208 ///@}
209
210 ///@{
211 /**
212 * @brief Floating point arithmetic inserters
213 * @param __f A variable of builtin floating point type.
214 * @return @c *this if successful
215 *
216 * These functions use the stream's current locale (specifically, the
217 * @c num_get facet) to perform numeric formatting.
218 */
219 __ostream_type&
220 operator<<(double __f)
221 { return _M_insert(__f); }
222
223 __ostream_type&
224 operator<<(float __f)
225 {
226 // _GLIBCXX_RESOLVE_LIB_DEFECTS
227 // 117. basic_ostream uses nonexistent num_put member functions.
228 return _M_insert(static_cast<double>(__f));
229 }
230
231 __ostream_type&
232 operator<<(long double __f)
233 { return _M_insert(__f); }
234 ///@}
235
236 /**
237 * @brief Pointer arithmetic inserters
238 * @param __p A variable of pointer type.
239 * @return @c *this if successful
240 *
241 * These functions use the stream's current locale (specifically, the
242 * @c num_get facet) to perform numeric formatting.
243 */
244 __ostream_type&
245 operator<<(const void* __p)
246 { return _M_insert(__p); }
247
248#if __cplusplus >= 201703L
249 __ostream_type&
250 operator<<(nullptr_t)
251 { return *this << "nullptr"; }
252#endif
253
254#if __cplusplus > 202002L
255 __attribute__((__always_inline__))
256 __ostream_type&
257 operator<<(const volatile void* __p)
258 { return _M_insert(const_cast<const void*>(__p)); }
259#endif
260
261 /**
262 * @brief Extracting from another streambuf.
263 * @param __sb A pointer to a streambuf
264 *
265 * This function behaves like one of the basic arithmetic extractors,
266 * in that it also constructs a sentry object and has the same error
267 * handling behavior.
268 *
269 * If @p __sb is NULL, the stream will set failbit in its error state.
270 *
271 * Characters are extracted from @p __sb and inserted into @c *this
272 * until one of the following occurs:
273 *
274 * - the input stream reaches end-of-file,
275 * - insertion into the output sequence fails (in this case, the
276 * character that would have been inserted is not extracted), or
277 * - an exception occurs while getting a character from @p __sb, which
278 * sets failbit in the error state
279 *
280 * If the function inserts no characters, failbit is set.
281 */
282 __ostream_type&
283 operator<<(__streambuf_type* __sb);
284 ///@}
285
286 ///@{
287 /**
288 * @name Unformatted Output Functions
289 *
290 * All the unformatted output functions have some common behavior.
291 * Each starts by constructing a temporary object of type
292 * std::basic_ostream::sentry. This has several effects, concluding
293 * with the setting of a status flag; see the sentry documentation
294 * for more.
295 *
296 * If the sentry status is good, the function tries to generate
297 * whatever data is appropriate for the type of the argument.
298 *
299 * If an exception is thrown during insertion, ios_base::badbit
300 * will be turned on in the stream's error state. If badbit is on in
301 * the stream's exceptions mask, the exception will be rethrown
302 * without completing its actions.
303 */
304
305 /**
306 * @brief Simple insertion.
307 * @param __c The character to insert.
308 * @return *this
309 *
310 * Tries to insert @p __c.
311 *
312 * @note This function is not overloaded on signed char and
313 * unsigned char.
314 */
315 __ostream_type&
316 put(char_type __c);
317
318 /**
319 * @brief Character string insertion.
320 * @param __s The array to insert.
321 * @param __n Maximum number of characters to insert.
322 * @return *this
323 *
324 * Characters are copied from @p __s and inserted into the stream until
325 * one of the following happens:
326 *
327 * - @p __n characters are inserted
328 * - inserting into the output sequence fails (in this case, badbit
329 * will be set in the stream's error state)
330 *
331 * @note This function is not overloaded on signed char and
332 * unsigned char.
333 */
334 __ostream_type&
335 write(const char_type* __s, streamsize __n);
336 ///@}
337
338 /**
339 * @brief Synchronizing the stream buffer.
340 * @return *this
341 *
342 * If @c rdbuf() is a null pointer, changes nothing.
343 *
344 * Otherwise, calls @c rdbuf()->pubsync(), and if that returns -1,
345 * sets badbit.
346 */
347 __ostream_type&
348 flush();
349
350 /**
351 * @brief Getting the current write position.
352 * @return A file position object.
353 *
354 * If @c fail() is not false, returns @c pos_type(-1) to indicate
355 * failure. Otherwise returns @c rdbuf()->pubseekoff(0,cur,out).
356 */
357 pos_type
358 tellp();
359
360 /**
361 * @brief Changing the current write position.
362 * @param __pos A file position object.
363 * @return *this
364 *
365 * If @c fail() is not true, calls @c rdbuf()->pubseekpos(pos). If
366 * that function fails, sets failbit.
367 */
368 __ostream_type&
369 seekp(pos_type);
370
371 /**
372 * @brief Changing the current write position.
373 * @param __off A file offset object.
374 * @param __dir The direction in which to seek.
375 * @return *this
376 *
377 * If @c fail() is not true, calls @c rdbuf()->pubseekoff(off,dir).
378 * If that function fails, sets failbit.
379 */
380 __ostream_type&
381 seekp(off_type, ios_base::seekdir);
382
383 protected:
384 basic_ostream()
385 { this->init(0); }
386
387#if __cplusplus >= 201103L
388 // Non-standard constructor that does not call init()
389 basic_ostream(basic_iostream<_CharT, _Traits>&) { }
390
391 basic_ostream(const basic_ostream&) = delete;
392
393 basic_ostream(basic_ostream&& __rhs)
394 : __ios_type()
395 { __ios_type::move(__rhs); }
396
397 // 27.7.3.3 Assign/swap
398
399 basic_ostream& operator=(const basic_ostream&) = delete;
400
401 basic_ostream&
402 operator=(basic_ostream&& __rhs)
403 {
404 swap(__rhs);
405 return *this;
406 }
407
408 void
409 swap(basic_ostream& __rhs)
410 { __ios_type::swap(__rhs); }
411#endif
412
413 template<typename _ValueT>
414 __ostream_type&
415 _M_insert(_ValueT __v);
416
417 private:
418#if !_GLIBCXX_INLINE_VERSION
419 void
420 _M_write(const char_type* __s, streamsize __n)
421 { std::__ostream_insert(*this, __s, __n); }
422#endif
423 };
424
425 /**
426 * @brief Performs setup work for output streams.
427 *
428 * Objects of this class are created before all of the standard
429 * inserters are run. It is responsible for <em>exception-safe prefix and
430 * suffix operations</em>.
431 */
432 template <typename _CharT, typename _Traits>
433 class basic_ostream<_CharT, _Traits>::sentry
434 {
435 // Data Members.
436 bool _M_ok;
437 basic_ostream<_CharT, _Traits>& _M_os;
438
439 public:
440 /**
441 * @brief The constructor performs preparatory work.
442 * @param __os The output stream to guard.
443 *
444 * If the stream state is good (@a __os.good() is true), then if the
445 * stream is tied to another output stream, @c is.tie()->flush()
446 * is called to synchronize the output sequences.
447 *
448 * If the stream state is still good, then the sentry state becomes
449 * true (@a okay).
450 */
451 explicit
452 sentry(basic_ostream<_CharT, _Traits>& __os);
453
454#pragma GCC diagnostic push
455#pragma GCC diagnostic ignored "-Wdeprecated-declarations"
456 /**
457 * @brief Possibly flushes the stream.
458 *
459 * If @c ios_base::unitbuf is set in @c os.flags(), and
460 * @c std::uncaught_exception() is true, the sentry destructor calls
461 * @c flush() on the output stream.
462 */
463 ~sentry()
464 {
465 // XXX MT
466 if (bool(_M_os.flags() & ios_base::unitbuf) && !uncaught_exception())
467 {
468 // Can't call flush directly or else will get into recursive lock.
469 if (_M_os.rdbuf() && _M_os.rdbuf()->pubsync() == -1)
470 _M_os.setstate(ios_base::badbit);
471 }
472 }
473#pragma GCC diagnostic pop
474
475 /**
476 * @brief Quick status checking.
477 * @return The sentry state.
478 *
479 * For ease of use, sentries may be converted to booleans. The
480 * return value is that of the sentry state (true == okay).
481 */
482#if __cplusplus >= 201103L
483 explicit
484#endif
485 operator bool() const
486 { return _M_ok; }
487 };
488
489 ///@{
490 /**
491 * @brief Character inserters
492 * @param __out An output stream.
493 * @param __c A character.
494 * @return out
495 *
496 * Behaves like one of the formatted arithmetic inserters described in
497 * std::basic_ostream. After constructing a sentry object with good
498 * status, this function inserts a single character and any required
499 * padding (as determined by [22.2.2.2.2]). @c __out.width(0) is then
500 * called.
501 *
502 * If @p __c is of type @c char and the character type of the stream is not
503 * @c char, the character is widened before insertion.
504 */
505 template<typename _CharT, typename _Traits>
506 inline basic_ostream<_CharT, _Traits>&
507 operator<<(basic_ostream<_CharT, _Traits>& __out, _CharT __c)
508 {
509 if (__out.width() != 0)
510 return __ostream_insert(__out, &__c, 1);
511 __out.put(__c);
512 return __out;
513 }
514
515 template<typename _CharT, typename _Traits>
516 inline basic_ostream<_CharT, _Traits>&
517 operator<<(basic_ostream<_CharT, _Traits>& __out, char __c)
518 { return (__out << __out.widen(__c)); }
519
520 // Specialization
521 template<typename _Traits>
522 inline basic_ostream<char, _Traits>&
523 operator<<(basic_ostream<char, _Traits>& __out, char __c)
524 {
525 if (__out.width() != 0)
526 return __ostream_insert(__out, &__c, 1);
527 __out.put(__c);
528 return __out;
529 }
530
531 // Signed and unsigned
532 template<typename _Traits>
533 inline basic_ostream<char, _Traits>&
534 operator<<(basic_ostream<char, _Traits>& __out, signed char __c)
535 { return (__out << static_cast<char>(__c)); }
536
537 template<typename _Traits>
538 inline basic_ostream<char, _Traits>&
539 operator<<(basic_ostream<char, _Traits>& __out, unsigned char __c)
540 { return (__out << static_cast<char>(__c)); }
541
542#if __cplusplus > 201703L
543 // The following deleted overloads prevent formatting character values as
544 // numeric values.
545
546 template<typename _Traits>
547 basic_ostream<char, _Traits>&
548 operator<<(basic_ostream<char, _Traits>&, wchar_t) = delete;
549
550#ifdef _GLIBCXX_USE_CHAR8_T
551 template<typename _Traits>
552 basic_ostream<char, _Traits>&
553 operator<<(basic_ostream<char, _Traits>&, char8_t) = delete;
554#endif
555
556 template<typename _Traits>
557 basic_ostream<char, _Traits>&
558 operator<<(basic_ostream<char, _Traits>&, char16_t) = delete;
559
560 template<typename _Traits>
561 basic_ostream<char, _Traits>&
562 operator<<(basic_ostream<char, _Traits>&, char32_t) = delete;
563
564#ifdef _GLIBCXX_USE_WCHAR_T
565#ifdef _GLIBCXX_USE_CHAR8_T
566 template<typename _Traits>
567 basic_ostream<wchar_t, _Traits>&
568 operator<<(basic_ostream<wchar_t, _Traits>&, char8_t) = delete;
569#endif // _GLIBCXX_USE_CHAR8_T
570
571 template<typename _Traits>
572 basic_ostream<wchar_t, _Traits>&
573 operator<<(basic_ostream<wchar_t, _Traits>&, char16_t) = delete;
574
575 template<typename _Traits>
576 basic_ostream<wchar_t, _Traits>&
577 operator<<(basic_ostream<wchar_t, _Traits>&, char32_t) = delete;
578#endif // _GLIBCXX_USE_WCHAR_T
579#endif // C++20
580 ///@}
581
582 ///@{
583 /**
584 * @brief String inserters
585 * @param __out An output stream.
586 * @param __s A character string.
587 * @return out
588 * @pre @p __s must be a non-NULL pointer
589 *
590 * Behaves like one of the formatted arithmetic inserters described in
591 * std::basic_ostream. After constructing a sentry object with good
592 * status, this function inserts @c traits::length(__s) characters starting
593 * at @p __s, widened if necessary, followed by any required padding (as
594 * determined by [22.2.2.2.2]). @c __out.width(0) is then called.
595 */
596 template<typename _CharT, typename _Traits>
597 inline basic_ostream<_CharT, _Traits>&
598 operator<<(basic_ostream<_CharT, _Traits>& __out, const _CharT* __s)
599 {
600 if (!__s)
601 __out.setstate(ios_base::badbit);
602 else
603 __ostream_insert(__out, __s,
604 static_cast<streamsize>(_Traits::length(__s)));
605 return __out;
606 }
607
608 template<typename _CharT, typename _Traits>
609 basic_ostream<_CharT, _Traits> &
610 operator<<(basic_ostream<_CharT, _Traits>& __out, const char* __s);
611
612 // Partial specializations
613 template<typename _Traits>
614 inline basic_ostream<char, _Traits>&
615 operator<<(basic_ostream<char, _Traits>& __out, const char* __s)
616 {
617 if (!__s)
618 __out.setstate(ios_base::badbit);
619 else
620 __ostream_insert(__out, __s,
621 static_cast<streamsize>(_Traits::length(__s)));
622 return __out;
623 }
624
625 // Signed and unsigned
626 template<typename _Traits>
627 inline basic_ostream<char, _Traits>&
628 operator<<(basic_ostream<char, _Traits>& __out, const signed char* __s)
629 { return (__out << reinterpret_cast<const char*>(__s)); }
630
631 template<typename _Traits>
632 inline basic_ostream<char, _Traits> &
633 operator<<(basic_ostream<char, _Traits>& __out, const unsigned char* __s)
634 { return (__out << reinterpret_cast<const char*>(__s)); }
635
636#if __cplusplus > 201703L
637 // The following deleted overloads prevent formatting strings as
638 // pointer values.
639
640 template<typename _Traits>
641 basic_ostream<char, _Traits>&
642 operator<<(basic_ostream<char, _Traits>&, const wchar_t*) = delete;
643
644#ifdef _GLIBCXX_USE_CHAR8_T
645 template<typename _Traits>
646 basic_ostream<char, _Traits>&
647 operator<<(basic_ostream<char, _Traits>&, const char8_t*) = delete;
648#endif // _GLIBCXX_USE_CHAR8_T
649
650 template<typename _Traits>
651 basic_ostream<char, _Traits>&
652 operator<<(basic_ostream<char, _Traits>&, const char16_t*) = delete;
653
654 template<typename _Traits>
655 basic_ostream<char, _Traits>&
656 operator<<(basic_ostream<char, _Traits>&, const char32_t*) = delete;
657
658#ifdef _GLIBCXX_USE_WCHAR_T
659#ifdef _GLIBCXX_USE_CHAR8_T
660 template<typename _Traits>
661 basic_ostream<wchar_t, _Traits>&
662 operator<<(basic_ostream<wchar_t, _Traits>&, const char8_t*) = delete;
663#endif
664
665 template<typename _Traits>
666 basic_ostream<wchar_t, _Traits>&
667 operator<<(basic_ostream<wchar_t, _Traits>&, const char16_t*) = delete;
668
669 template<typename _Traits>
670 basic_ostream<wchar_t, _Traits>&
671 operator<<(basic_ostream<wchar_t, _Traits>&, const char32_t*) = delete;
672#endif // _GLIBCXX_USE_WCHAR_T
673#endif // C++20
674 ///@}
675
676 // Standard basic_ostream manipulators
677
678 /**
679 * @brief Write a newline and flush the stream.
680 *
681 * This manipulator is often mistakenly used when a simple newline is
682 * desired, leading to poor buffering performance. See
683 * https://gcc.gnu.org/onlinedocs/libstdc++/manual/streambufs.html#io.streambuf.buffering
684 * for more on this subject.
685 */
686 template<typename _CharT, typename _Traits>
687 inline basic_ostream<_CharT, _Traits>&
688 endl(basic_ostream<_CharT, _Traits>& __os)
689 { return flush(__os.put(__os.widen('\n'))); }
690
691 /**
692 * @brief Write a null character into the output sequence.
693 *
694 * <em>Null character</em> is @c CharT() by definition. For CharT
695 * of @c char, this correctly writes the ASCII @c NUL character
696 * string terminator.
697 */
698 template<typename _CharT, typename _Traits>
699 inline basic_ostream<_CharT, _Traits>&
700 ends(basic_ostream<_CharT, _Traits>& __os)
701 { return __os.put(_CharT()); }
702
703 /**
704 * @brief Flushes the output stream.
705 *
706 * This manipulator simply calls the stream's @c flush() member function.
707 */
708 template<typename _CharT, typename _Traits>
709 inline basic_ostream<_CharT, _Traits>&
710 flush(basic_ostream<_CharT, _Traits>& __os)
711 { return __os.flush(); }
712
713#if __cplusplus >= 201103L
714 // C++11 27.7.3.9 Rvalue stream insertion [ostream.rvalue]
715 // _GLIBCXX_RESOLVE_LIB_DEFECTS
716 // 1203. More useful rvalue stream insertion
717
718#if __cpp_lib_concepts
719 // Use concepts if possible because they're cheaper to evaluate.
720 template<typename _Tp>
721 concept __derived_from_ios_base = is_class_v<_Tp>
722 && (!is_same_v<_Tp, ios_base>)
723 && requires (_Tp* __t, ios_base* __b) { __b = __t; };
724
725 template<typename _Os, typename _Tp>
726 requires __derived_from_ios_base<_Os>
727 && requires (_Os& __os, const _Tp& __t) { __os << __t; }
728 using __rvalue_stream_insertion_t = _Os&&;
729#else
730 template<typename _Tp>
731 using _Require_derived_from_ios_base
732 = _Require<is_class<_Tp>, __not_<is_same<_Tp, ios_base>>,
733 is_convertible<typename add_pointer<_Tp>::type, ios_base*>>;
734
735 template<typename _Os, typename _Tp,
736 typename = _Require_derived_from_ios_base<_Os>,
737 typename
738 = decltype(std::declval<_Os&>() << std::declval<const _Tp&>())>
739 using __rvalue_stream_insertion_t = _Os&&;
740#endif
741
742 /**
743 * @brief Generic inserter for rvalue stream
744 * @param __os An input stream.
745 * @param __x A reference to the object being inserted.
746 * @return __os
747 *
748 * This is just a forwarding function to allow insertion to
749 * rvalue streams since they won't bind to the inserter functions
750 * that take an lvalue reference.
751 */
752 template<typename _Ostream, typename _Tp>
753 inline __rvalue_stream_insertion_t<_Ostream, _Tp>
754 operator<<(_Ostream&& __os, const _Tp& __x)
755 {
756 __os << __x;
757 return std::move(__os);
758 }
759
760#if __cplusplus > 201703L && _GLIBCXX_USE_CXX11_ABI
761 template<typename _CharT, typename _Traits>
762 class __syncbuf_base : public basic_streambuf<_CharT, _Traits>
763 {
764 public:
765 static bool*
766 _S_get(basic_streambuf<_CharT, _Traits>* __buf [[maybe_unused]]) noexcept
767 {
768#if __cpp_rtti
769 if (auto __p = dynamic_cast<__syncbuf_base*>(__buf))
770 return &__p->_M_emit_on_sync;
771#endif
772 return nullptr;
773 }
774
775 protected:
776 __syncbuf_base(basic_streambuf<_CharT, _Traits>* __w = nullptr)
777 : _M_wrapped(__w)
778 { }
779
780 basic_streambuf<_CharT, _Traits>* _M_wrapped = nullptr;
781 bool _M_emit_on_sync = false;
782 bool _M_needs_sync = false;
783 };
784
785 template<typename _CharT, typename _Traits>
786 inline basic_ostream<_CharT, _Traits>&
787 emit_on_flush(basic_ostream<_CharT, _Traits>& __os)
788 {
789 if (bool* __flag = __syncbuf_base<_CharT, _Traits>::_S_get(__os.rdbuf()))
790 *__flag = true;
791 return __os;
792 }
793
794 template<typename _CharT, typename _Traits>
795 inline basic_ostream<_CharT, _Traits>&
796 noemit_on_flush(basic_ostream<_CharT, _Traits>& __os)
797 {
798 if (bool* __flag = __syncbuf_base<_CharT, _Traits>::_S_get(__os.rdbuf()))
799 *__flag = false;
800 return __os;
801 }
802
803 template<typename _CharT, typename _Traits>
804 inline basic_ostream<_CharT, _Traits>&
805 flush_emit(basic_ostream<_CharT, _Traits>& __os)
806 {
807 struct _Restore
808 {
809 ~_Restore() { *_M_flag = _M_prev; }
810
811 bool _M_prev = false;
812 bool* _M_flag = &_M_prev;
813 } __restore;
814
815 if (bool* __flag = __syncbuf_base<_CharT, _Traits>::_S_get(__os.rdbuf()))
816 {
817 __restore._M_prev = *__flag;
818 __restore._M_flag = __flag;
819 *__flag = true;
820 }
821
822 __os.flush();
823 return __os;
824 }
825
826#endif // C++20
827
828#endif // C++11
829
830_GLIBCXX_END_NAMESPACE_VERSION
831} // namespace std
832
833#include <bits/ostream.tcc>
834
835#endif /* _GLIBCXX_OSTREAM */
836