libstdc++
ostream
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1 // Output streams -*- C++ -*-
2 
3 // Copyright (C) 1997-2021 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 
41 namespace 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 Core write functionality, without sentry.
320  * @param __s The array to insert.
321  * @param __n Maximum number of characters to insert.
322  */
323  void
324  _M_write(const char_type* __s, streamsize __n)
325  {
326  const streamsize __put = this->rdbuf()->sputn(__s, __n);
327  if (__put != __n)
328  this->setstate(ios_base::badbit);
329  }
330 
331  /**
332  * @brief Character string insertion.
333  * @param __s The array to insert.
334  * @param __n Maximum number of characters to insert.
335  * @return *this
336  *
337  * Characters are copied from @p __s and inserted into the stream until
338  * one of the following happens:
339  *
340  * - @p __n characters are inserted
341  * - inserting into the output sequence fails (in this case, badbit
342  * will be set in the stream's error state)
343  *
344  * @note This function is not overloaded on signed char and
345  * unsigned char.
346  */
347  __ostream_type&
348  write(const char_type* __s, streamsize __n);
349  ///@}
350 
351  /**
352  * @brief Synchronizing the stream buffer.
353  * @return *this
354  *
355  * If @c rdbuf() is a null pointer, changes nothing.
356  *
357  * Otherwise, calls @c rdbuf()->pubsync(), and if that returns -1,
358  * sets badbit.
359  */
360  __ostream_type&
361  flush();
362 
363  /**
364  * @brief Getting the current write position.
365  * @return A file position object.
366  *
367  * If @c fail() is not false, returns @c pos_type(-1) to indicate
368  * failure. Otherwise returns @c rdbuf()->pubseekoff(0,cur,out).
369  */
370  pos_type
371  tellp();
372 
373  /**
374  * @brief Changing the current write position.
375  * @param __pos A file position object.
376  * @return *this
377  *
378  * If @c fail() is not true, calls @c rdbuf()->pubseekpos(pos). If
379  * that function fails, sets failbit.
380  */
381  __ostream_type&
382  seekp(pos_type);
383 
384  /**
385  * @brief Changing the current write position.
386  * @param __off A file offset object.
387  * @param __dir The direction in which to seek.
388  * @return *this
389  *
390  * If @c fail() is not true, calls @c rdbuf()->pubseekoff(off,dir).
391  * If that function fails, sets failbit.
392  */
393  __ostream_type&
394  seekp(off_type, ios_base::seekdir);
395 
396  protected:
397  basic_ostream()
398  { this->init(0); }
399 
400 #if __cplusplus >= 201103L
401  // Non-standard constructor that does not call init()
402  basic_ostream(basic_iostream<_CharT, _Traits>&) { }
403 
404  basic_ostream(const basic_ostream&) = delete;
405 
406  basic_ostream(basic_ostream&& __rhs)
407  : __ios_type()
408  { __ios_type::move(__rhs); }
409 
410  // 27.7.3.3 Assign/swap
411 
412  basic_ostream& operator=(const basic_ostream&) = delete;
413 
414  basic_ostream&
415  operator=(basic_ostream&& __rhs)
416  {
417  swap(__rhs);
418  return *this;
419  }
420 
421  void
422  swap(basic_ostream& __rhs)
423  { __ios_type::swap(__rhs); }
424 #endif
425 
426  template<typename _ValueT>
427  __ostream_type&
428  _M_insert(_ValueT __v);
429  };
430 
431  /**
432  * @brief Performs setup work for output streams.
433  *
434  * Objects of this class are created before all of the standard
435  * inserters are run. It is responsible for <em>exception-safe prefix and
436  * suffix operations</em>.
437  */
438  template <typename _CharT, typename _Traits>
439  class basic_ostream<_CharT, _Traits>::sentry
440  {
441  // Data Members.
442  bool _M_ok;
443  basic_ostream<_CharT, _Traits>& _M_os;
444 
445  public:
446  /**
447  * @brief The constructor performs preparatory work.
448  * @param __os The output stream to guard.
449  *
450  * If the stream state is good (@a __os.good() is true), then if the
451  * stream is tied to another output stream, @c is.tie()->flush()
452  * is called to synchronize the output sequences.
453  *
454  * If the stream state is still good, then the sentry state becomes
455  * true (@a okay).
456  */
457  explicit
458  sentry(basic_ostream<_CharT, _Traits>& __os);
459 
460 #pragma GCC diagnostic push
461 #pragma GCC diagnostic ignored "-Wdeprecated-declarations"
462  /**
463  * @brief Possibly flushes the stream.
464  *
465  * If @c ios_base::unitbuf is set in @c os.flags(), and
466  * @c std::uncaught_exception() is true, the sentry destructor calls
467  * @c flush() on the output stream.
468  */
469  ~sentry()
470  {
471  // XXX MT
472  if (bool(_M_os.flags() & ios_base::unitbuf) && !uncaught_exception())
473  {
474  // Can't call flush directly or else will get into recursive lock.
475  if (_M_os.rdbuf() && _M_os.rdbuf()->pubsync() == -1)
476  _M_os.setstate(ios_base::badbit);
477  }
478  }
479 #pragma GCC diagnostic pop
480 
481  /**
482  * @brief Quick status checking.
483  * @return The sentry state.
484  *
485  * For ease of use, sentries may be converted to booleans. The
486  * return value is that of the sentry state (true == okay).
487  */
488 #if __cplusplus >= 201103L
489  explicit
490 #endif
491  operator bool() const
492  { return _M_ok; }
493  };
494 
495  ///@{
496  /**
497  * @brief Character inserters
498  * @param __out An output stream.
499  * @param __c A character.
500  * @return out
501  *
502  * Behaves like one of the formatted arithmetic inserters described in
503  * std::basic_ostream. After constructing a sentry object with good
504  * status, this function inserts a single character and any required
505  * padding (as determined by [22.2.2.2.2]). @c __out.width(0) is then
506  * called.
507  *
508  * If @p __c is of type @c char and the character type of the stream is not
509  * @c char, the character is widened before insertion.
510  */
511  template<typename _CharT, typename _Traits>
512  inline basic_ostream<_CharT, _Traits>&
513  operator<<(basic_ostream<_CharT, _Traits>& __out, _CharT __c)
514  { return __ostream_insert(__out, &__c, 1); }
515 
516  template<typename _CharT, typename _Traits>
517  inline basic_ostream<_CharT, _Traits>&
518  operator<<(basic_ostream<_CharT, _Traits>& __out, char __c)
519  { return (__out << __out.widen(__c)); }
520 
521  // Specialization
522  template<typename _Traits>
523  inline basic_ostream<char, _Traits>&
524  operator<<(basic_ostream<char, _Traits>& __out, char __c)
525  { return __ostream_insert(__out, &__c, 1); }
526 
527  // Signed and unsigned
528  template<typename _Traits>
529  inline basic_ostream<char, _Traits>&
530  operator<<(basic_ostream<char, _Traits>& __out, signed char __c)
531  { return (__out << static_cast<char>(__c)); }
532 
533  template<typename _Traits>
534  inline basic_ostream<char, _Traits>&
535  operator<<(basic_ostream<char, _Traits>& __out, unsigned char __c)
536  { return (__out << static_cast<char>(__c)); }
537 
538 #if __cplusplus > 201703L
539  // The following deleted overloads prevent formatting character values as
540  // numeric values.
541 
542  template<typename _Traits>
543  basic_ostream<char, _Traits>&
544  operator<<(basic_ostream<char, _Traits>&, wchar_t) = delete;
545 
546 #ifdef _GLIBCXX_USE_CHAR8_T
547  template<typename _Traits>
548  basic_ostream<char, _Traits>&
549  operator<<(basic_ostream<char, _Traits>&, char8_t) = delete;
550 #endif
551 
552  template<typename _Traits>
553  basic_ostream<char, _Traits>&
554  operator<<(basic_ostream<char, _Traits>&, char16_t) = delete;
555 
556  template<typename _Traits>
557  basic_ostream<char, _Traits>&
558  operator<<(basic_ostream<char, _Traits>&, char32_t) = delete;
559 
560 #ifdef _GLIBCXX_USE_WCHAR_T
561 #ifdef _GLIBCXX_USE_CHAR8_T
562  template<typename _Traits>
563  basic_ostream<wchar_t, _Traits>&
564  operator<<(basic_ostream<wchar_t, _Traits>&, char8_t) = delete;
565 #endif // _GLIBCXX_USE_CHAR8_T
566 
567  template<typename _Traits>
568  basic_ostream<wchar_t, _Traits>&
569  operator<<(basic_ostream<wchar_t, _Traits>&, char16_t) = delete;
570 
571  template<typename _Traits>
572  basic_ostream<wchar_t, _Traits>&
573  operator<<(basic_ostream<wchar_t, _Traits>&, char32_t) = delete;
574 #endif // _GLIBCXX_USE_WCHAR_T
575 #endif // C++20
576  ///@}
577 
578  ///@{
579  /**
580  * @brief String inserters
581  * @param __out An output stream.
582  * @param __s A character string.
583  * @return out
584  * @pre @p __s must be a non-NULL pointer
585  *
586  * Behaves like one of the formatted arithmetic inserters described in
587  * std::basic_ostream. After constructing a sentry object with good
588  * status, this function inserts @c traits::length(__s) characters starting
589  * at @p __s, widened if necessary, followed by any required padding (as
590  * determined by [22.2.2.2.2]). @c __out.width(0) is then called.
591  */
592  template<typename _CharT, typename _Traits>
593  inline basic_ostream<_CharT, _Traits>&
594  operator<<(basic_ostream<_CharT, _Traits>& __out, const _CharT* __s)
595  {
596  if (!__s)
597  __out.setstate(ios_base::badbit);
598  else
599  __ostream_insert(__out, __s,
600  static_cast<streamsize>(_Traits::length(__s)));
601  return __out;
602  }
603 
604  template<typename _CharT, typename _Traits>
605  basic_ostream<_CharT, _Traits> &
606  operator<<(basic_ostream<_CharT, _Traits>& __out, const char* __s);
607 
608  // Partial specializations
609  template<typename _Traits>
610  inline basic_ostream<char, _Traits>&
611  operator<<(basic_ostream<char, _Traits>& __out, const char* __s)
612  {
613  if (!__s)
614  __out.setstate(ios_base::badbit);
615  else
616  __ostream_insert(__out, __s,
617  static_cast<streamsize>(_Traits::length(__s)));
618  return __out;
619  }
620 
621  // Signed and unsigned
622  template<typename _Traits>
623  inline basic_ostream<char, _Traits>&
624  operator<<(basic_ostream<char, _Traits>& __out, const signed char* __s)
625  { return (__out << reinterpret_cast<const char*>(__s)); }
626 
627  template<typename _Traits>
628  inline basic_ostream<char, _Traits> &
629  operator<<(basic_ostream<char, _Traits>& __out, const unsigned char* __s)
630  { return (__out << reinterpret_cast<const char*>(__s)); }
631 
632 #if __cplusplus > 201703L
633  // The following deleted overloads prevent formatting strings as
634  // pointer values.
635 
636  template<typename _Traits>
637  basic_ostream<char, _Traits>&
638  operator<<(basic_ostream<char, _Traits>&, const wchar_t*) = delete;
639 
640 #ifdef _GLIBCXX_USE_CHAR8_T
641  template<typename _Traits>
642  basic_ostream<char, _Traits>&
643  operator<<(basic_ostream<char, _Traits>&, const char8_t*) = delete;
644 #endif // _GLIBCXX_USE_CHAR8_T
645 
646  template<typename _Traits>
647  basic_ostream<char, _Traits>&
648  operator<<(basic_ostream<char, _Traits>&, const char16_t*) = delete;
649 
650  template<typename _Traits>
651  basic_ostream<char, _Traits>&
652  operator<<(basic_ostream<char, _Traits>&, const char32_t*) = delete;
653 
654 #ifdef _GLIBCXX_USE_WCHAR_T
655 #ifdef _GLIBCXX_USE_CHAR8_T
656  template<typename _Traits>
657  basic_ostream<wchar_t, _Traits>&
658  operator<<(basic_ostream<wchar_t, _Traits>&, const char8_t*) = delete;
659 #endif
660 
661  template<typename _Traits>
662  basic_ostream<wchar_t, _Traits>&
663  operator<<(basic_ostream<wchar_t, _Traits>&, const char16_t*) = delete;
664 
665  template<typename _Traits>
666  basic_ostream<wchar_t, _Traits>&
667  operator<<(basic_ostream<wchar_t, _Traits>&, const char32_t*) = delete;
668 #endif // _GLIBCXX_USE_WCHAR_T
669 #endif // C++20
670  ///@}
671 
672  // Standard basic_ostream manipulators
673 
674  /**
675  * @brief Write a newline and flush the stream.
676  *
677  * This manipulator is often mistakenly used when a simple newline is
678  * desired, leading to poor buffering performance. See
679  * https://gcc.gnu.org/onlinedocs/libstdc++/manual/streambufs.html#io.streambuf.buffering
680  * for more on this subject.
681  */
682  template<typename _CharT, typename _Traits>
683  inline basic_ostream<_CharT, _Traits>&
684  endl(basic_ostream<_CharT, _Traits>& __os)
685  { return flush(__os.put(__os.widen('\n'))); }
686 
687  /**
688  * @brief Write a null character into the output sequence.
689  *
690  * <em>Null character</em> is @c CharT() by definition. For CharT
691  * of @c char, this correctly writes the ASCII @c NUL character
692  * string terminator.
693  */
694  template<typename _CharT, typename _Traits>
695  inline basic_ostream<_CharT, _Traits>&
696  ends(basic_ostream<_CharT, _Traits>& __os)
697  { return __os.put(_CharT()); }
698 
699  /**
700  * @brief Flushes the output stream.
701  *
702  * This manipulator simply calls the stream's @c flush() member function.
703  */
704  template<typename _CharT, typename _Traits>
705  inline basic_ostream<_CharT, _Traits>&
706  flush(basic_ostream<_CharT, _Traits>& __os)
707  { return __os.flush(); }
708 
709 #if __cplusplus >= 201103L
710  // C++11 27.7.3.9 Rvalue stream insertion [ostream.rvalue]
711  // _GLIBCXX_RESOLVE_LIB_DEFECTS
712  // 1203. More useful rvalue stream insertion
713 
714 #if __cpp_lib_concepts
715  // Use concepts if possible because they're cheaper to evaluate.
716  template<typename _Tp>
717  concept __derived_from_ios_base = is_class_v<_Tp>
718  && (!is_same_v<_Tp, ios_base>)
719  && requires (_Tp* __t, ios_base* __b) { __b = __t; };
720 
721  template<typename _Os, typename _Tp>
722  requires __derived_from_ios_base<_Os>
723  && requires (_Os& __os, const _Tp& __t) { __os << __t; }
724  using __rvalue_stream_insertion_t = _Os&&;
725 #else
726  template<typename _Tp>
727  using _Require_derived_from_ios_base
728  = _Require<is_class<_Tp>, __not_<is_same<_Tp, ios_base>>,
729  is_convertible<typename add_pointer<_Tp>::type, ios_base*>>;
730 
731  template<typename _Os, typename _Tp,
732  typename = _Require_derived_from_ios_base<_Os>,
733  typename
734  = decltype(std::declval<_Os&>() << std::declval<const _Tp&>())>
735  using __rvalue_stream_insertion_t = _Os&&;
736 #endif
737 
738  /**
739  * @brief Generic inserter for rvalue stream
740  * @param __os An input stream.
741  * @param __x A reference to the object being inserted.
742  * @return __os
743  *
744  * This is just a forwarding function to allow insertion to
745  * rvalue streams since they won't bind to the inserter functions
746  * that take an lvalue reference.
747  */
748  template<typename _Ostream, typename _Tp>
749  inline __rvalue_stream_insertion_t<_Ostream, _Tp>
750  operator<<(_Ostream&& __os, const _Tp& __x)
751  {
752  __os << __x;
753  return std::move(__os);
754  }
755 
756 #if __cplusplus > 201703L && _GLIBCXX_USE_CXX11_ABI
757  template<typename _CharT, typename _Traits>
758  class __syncbuf_base : public basic_streambuf<_CharT, _Traits>
759  {
760  public:
761  static bool*
762  _S_get(basic_streambuf<_CharT, _Traits>* __buf [[maybe_unused]]) noexcept
763  {
764 #if __cpp_rtti
765  if (auto __p = dynamic_cast<__syncbuf_base*>(__buf))
766  return &__p->_M_emit_on_sync;
767 #endif
768  return nullptr;
769  }
770 
771  protected:
772  __syncbuf_base(basic_streambuf<_CharT, _Traits>* __w = nullptr)
773  : _M_wrapped(__w)
774  { }
775 
776  basic_streambuf<_CharT, _Traits>* _M_wrapped = nullptr;
777  bool _M_emit_on_sync = false;
778  bool _M_needs_sync = false;
779  };
780 
781  template<typename _CharT, typename _Traits>
782  inline basic_ostream<_CharT, _Traits>&
783  emit_on_flush(basic_ostream<_CharT, _Traits>& __os)
784  {
785  if (bool* __flag = __syncbuf_base<_CharT, _Traits>::_S_get(__os.rdbuf()))
786  *__flag = true;
787  return __os;
788  }
789 
790  template<typename _CharT, typename _Traits>
791  inline basic_ostream<_CharT, _Traits>&
792  noemit_on_flush(basic_ostream<_CharT, _Traits>& __os)
793  {
794  if (bool* __flag = __syncbuf_base<_CharT, _Traits>::_S_get(__os.rdbuf()))
795  *__flag = false;
796  return __os;
797  }
798 
799  template<typename _CharT, typename _Traits>
800  inline basic_ostream<_CharT, _Traits>&
801  flush_emit(basic_ostream<_CharT, _Traits>& __os)
802  {
803  struct _Restore
804  {
805  ~_Restore() { *_M_flag = _M_prev; }
806 
807  bool _M_prev = false;
808  bool* _M_flag = &_M_prev;
809  } __restore;
810 
811  if (bool* __flag = __syncbuf_base<_CharT, _Traits>::_S_get(__os.rdbuf()))
812  {
813  __restore._M_prev = *__flag;
814  __restore._M_flag = __flag;
815  *__flag = true;
816  }
817 
818  __os.flush();
819  return __os;
820  }
821 
822 #endif // C++20
823 
824 #endif // C++11
825 
826 _GLIBCXX_END_NAMESPACE_VERSION
827 } // namespace std
828 
829 #include <bits/ostream.tcc>
830 
831 #endif /* _GLIBCXX_OSTREAM */