zZzzZ. — /usr/include/c++/11

Editing: ostream

// Output streams -*- C++ -*-

// Copyright (C) 1997-2021 Free Software Foundation, Inc.
//
// This file is part of the GNU ISO C++ Library.  This library is free
// software; you can redistribute it and/or modify it under the
// terms of the GNU General Public License as published by the
// Free Software Foundation; either version 3, or (at your option)
// any later version.

// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.

// Under Section 7 of GPL version 3, you are granted additional
// permissions described in the GCC Runtime Library Exception, version
// 3.1, as published by the Free Software Foundation.

// You should have received a copy of the GNU General Public License and
// a copy of the GCC Runtime Library Exception along with this program;
// see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
// <http://www.gnu.org/licenses/>.

/** @file include/ostream
 *  This is a Standard C++ Library header.
 */

//
// ISO C++ 14882: 27.6.2  Output streams
//

#ifndef _GLIBCXX_OSTREAM
#define _GLIBCXX_OSTREAM 1

#pragma GCC system_header

#include <ios>
#include <bits/ostream_insert.h>

namespace std _GLIBCXX_VISIBILITY(default)
{
_GLIBCXX_BEGIN_NAMESPACE_VERSION

/**
 * @brief Template class basic_ostream.
 * @ingroup io
 *
 * @tparam _CharT Type of character stream.
 * @tparam _Traits Traits for character type, defaults to
 * char_traits<_CharT>.
 *
 * This is the base class for all output streams. It provides text
 * formatting of all builtin types, and communicates with any class
 * derived from basic_streambuf to do the actual output.
 */
 template<typename _CharT, typename _Traits>
 class basic_ostream : virtual public basic_ios<_CharT, _Traits>
 {
 public:
 // Types (inherited from basic_ios):
 typedef _CharT			 		char_type;
 typedef typename _Traits::int_type 		int_type;
 typedef typename _Traits::pos_type 		pos_type;
 typedef typename _Traits::off_type 		off_type;
 typedef _Traits			 		traits_type;

// Non-standard Types:
 typedef basic_streambuf<_CharT, _Traits> 		__streambuf_type;
 typedef basic_ios<_CharT, _Traits>		__ios_type;
 typedef basic_ostream<_CharT, _Traits>		__ostream_type;
 typedef num_put<_CharT, ostreambuf_iterator<_CharT, _Traits> >
 							__num_put_type;
 typedef ctype<_CharT>	 			__ctype_type;

/**
       *  @brief  Base constructor.
       *
       *  This ctor is almost never called by the user directly, rather from
       *  derived classes' initialization lists, which pass a pointer to
       *  their own stream buffer.
      */
      explicit
      basic_ostream(__streambuf_type* __sb)
      { this->init(__sb); }

/**
       *  @brief  Base destructor.
       *
       *  This does very little apart from providing a virtual base dtor.
      */
      virtual
      ~basic_ostream() { }

/// Safe prefix/suffix operations.
      class sentry;
      friend class sentry;

///@{
 /**
 * @brief Interface for manipulators.
 *
 * Manipulators such as @c std::endl and @c std::hex use these
 * functions in constructs like "std::cout << std::endl". For more
 * information, see the iomanip header.
 */
 __ostream_type&
 operator<<(__ostream_type& (*__pf)(__ostream_type&))
 {
	// _GLIBCXX_RESOLVE_LIB_DEFECTS
	// DR 60. What is a formatted input function?
	// The inserters for manipulators are *not* formatted output functions.
	return __pf(*this);
 }

__ostream_type&
 operator<<(__ios_type& (*__pf)(__ios_type&))
 {
	// _GLIBCXX_RESOLVE_LIB_DEFECTS
	// DR 60. What is a formatted input function?
	// The inserters for manipulators are *not* formatted output functions.
	__pf(*this);
	return *this;
 }

__ostream_type&
 operator<<(ios_base& (*__pf) (ios_base&))
 {
	// _GLIBCXX_RESOLVE_LIB_DEFECTS
	// DR 60. What is a formatted input function?
	// The inserters for manipulators are *not* formatted output functions.
	__pf(*this);
	return *this;
 }
 ///@}

///@{
 /**
 * @name Inserters
 *
 * All the @c operator<< functions (aka formatted output
 * functions) have some common behavior. Each starts by
 * constructing a temporary object of type std::basic_ostream::sentry.
 * This can have several effects, concluding with the setting of a
 * status flag; see the sentry documentation for more.
 *
 * If the sentry status is good, the function tries to generate
 * whatever data is appropriate for the type of the argument.
 *
 * If an exception is thrown during insertion, ios_base::badbit
 * will be turned on in the stream's error state without causing an
 * ios_base::failure to be thrown. The original exception will then
 * be rethrown.
 */

///@{
 /**
 * @brief Integer arithmetic inserters
 * @param __n A variable of builtin integral type.
 * @return @c *this if successful
 *
 * These functions use the stream's current locale (specifically, the
 * @c num_get facet) to perform numeric formatting.
 */
 __ostream_type&
 operator<<(long __n)
 { return _M_insert(__n); }

__ostream_type&
 operator<<(unsigned long __n)
 { return _M_insert(__n); }

__ostream_type&
 operator<<(bool __n)
 { return _M_insert(__n); }

__ostream_type&
 operator<<(short __n);

__ostream_type&
 operator<<(unsigned short __n)
 {
	// _GLIBCXX_RESOLVE_LIB_DEFECTS
	// 117. basic_ostream uses nonexistent num_put member functions.
	return _M_insert(static_cast<unsigned long>(__n));
 }

__ostream_type&
 operator<<(int __n);

__ostream_type&
 operator<<(unsigned int __n)
 {
	// _GLIBCXX_RESOLVE_LIB_DEFECTS
	// 117. basic_ostream uses nonexistent num_put member functions.
	return _M_insert(static_cast<unsigned long>(__n));
 }

#ifdef _GLIBCXX_USE_LONG_LONG
 __ostream_type&
 operator<<(long long __n)
 { return _M_insert(__n); }

__ostream_type&
 operator<<(unsigned long long __n)
 { return _M_insert(__n); }
#endif
 ///@}

///@{
 /**
 * @brief Floating point arithmetic inserters
 * @param __f A variable of builtin floating point type.
 * @return @c *this if successful
 *
 * These functions use the stream's current locale (specifically, the
 * @c num_get facet) to perform numeric formatting.
 */
 __ostream_type&
 operator<<(double __f)
 { return _M_insert(__f); }

__ostream_type&
 operator<<(float __f)
 {
	// _GLIBCXX_RESOLVE_LIB_DEFECTS
	// 117. basic_ostream uses nonexistent num_put member functions.
	return _M_insert(static_cast<double>(__f));
 }

__ostream_type&
 operator<<(long double __f)
 { return _M_insert(__f); }
 ///@}

/**
 * @brief Pointer arithmetic inserters
 * @param __p A variable of pointer type.
 * @return @c *this if successful
 *
 * These functions use the stream's current locale (specifically, the
 * @c num_get facet) to perform numeric formatting.
 */
 __ostream_type&
 operator<<(const void* __p)
 { return _M_insert(__p); }

#if __cplusplus >= 201703L
 __ostream_type&
 operator<<(nullptr_t)
 { return *this << "nullptr"; }
#endif

#if __cplusplus > 202002L
 __attribute__((__always_inline__))
 __ostream_type&
 operator<<(const volatile void* __p)
 { return _M_insert(const_cast<const void*>(__p)); }
#endif

/**
 * @brief Extracting from another streambuf.
 * @param __sb A pointer to a streambuf
 *
 * This function behaves like one of the basic arithmetic extractors,
 * in that it also constructs a sentry object and has the same error
 * handling behavior.
 *
 * If @p __sb is NULL, the stream will set failbit in its error state.
 *
 * Characters are extracted from @p __sb and inserted into @c *this
 * until one of the following occurs:
 *
 * - the input stream reaches end-of-file,
 * - insertion into the output sequence fails (in this case, the
 * character that would have been inserted is not extracted), or
 * - an exception occurs while getting a character from @p __sb, which
 * sets failbit in the error state
 *
 * If the function inserts no characters, failbit is set.
 */
 __ostream_type&
 operator<<(__streambuf_type* __sb);
 ///@}

///@{
      /**
       *  @name Unformatted Output Functions
       *
       *  All the unformatted output functions have some common behavior.
       *  Each starts by constructing a temporary object of type
       *  std::basic_ostream::sentry.  This has several effects, concluding
       *  with the setting of a status flag; see the sentry documentation
       *  for more.
       *
       *  If the sentry status is good, the function tries to generate
       *  whatever data is appropriate for the type of the argument.
       *
       *  If an exception is thrown during insertion, ios_base::badbit
       *  will be turned on in the stream's error state.  If badbit is on in
       *  the stream's exceptions mask, the exception will be rethrown
       *  without completing its actions.
      */

/**
       *  @brief  Simple insertion.
       *  @param  __c  The character to insert.
       *  @return  *this
       *
       *  Tries to insert @p __c.
       *
       *  @note  This function is not overloaded on signed char and
       *         unsigned char.
      */
      __ostream_type&
      put(char_type __c);

/**
       *  @brief  Core write functionality, without sentry.
       *  @param  __s  The array to insert.
       *  @param  __n  Maximum number of characters to insert.
      */
      void
      _M_write(const char_type* __s, streamsize __n)
      {
	const streamsize __put = this->rdbuf()->sputn(__s, __n);
	if (__put != __n)
	  this->setstate(ios_base::badbit);
      }

/**
       *  @brief  Character string insertion.
       *  @param  __s  The array to insert.
       *  @param  __n  Maximum number of characters to insert.
       *  @return  *this
       *
       *  Characters are copied from @p __s and inserted into the stream until
       *  one of the following happens:
       *
       *  - @p __n characters are inserted
       *  - inserting into the output sequence fails (in this case, badbit
       *    will be set in the stream's error state)
       *
       *  @note  This function is not overloaded on signed char and
       *         unsigned char.
      */
      __ostream_type&
      write(const char_type* __s, streamsize __n);
      ///@}

/**
       *  @brief  Synchronizing the stream buffer.
       *  @return  *this
       *
       *  If @c rdbuf() is a null pointer, changes nothing.
       *
       *  Otherwise, calls @c rdbuf()->pubsync(), and if that returns -1,
       *  sets badbit.
      */
      __ostream_type&
      flush();

/**
       *  @brief  Getting the current write position.
       *  @return  A file position object.
       *
       *  If @c fail() is not false, returns @c pos_type(-1) to indicate
       *  failure.  Otherwise returns @c rdbuf()->pubseekoff(0,cur,out).
      */
      pos_type
      tellp();

/**
       *  @brief  Changing the current write position.
       *  @param  __pos  A file position object.
       *  @return  *this
       *
       *  If @c fail() is not true, calls @c rdbuf()->pubseekpos(pos).  If
       *  that function fails, sets failbit.
      */
      __ostream_type&
      seekp(pos_type);

/**
       *  @brief  Changing the current write position.
       *  @param  __off  A file offset object.
       *  @param  __dir  The direction in which to seek.
       *  @return  *this
       *
       *  If @c fail() is not true, calls @c rdbuf()->pubseekoff(off,dir).
       *  If that function fails, sets failbit.
      */
       __ostream_type&
      seekp(off_type, ios_base::seekdir);

protected:
      basic_ostream()
      { this->init(0); }

#if __cplusplus >= 201103L
 // Non-standard constructor that does not call init()
 basic_ostream(basic_iostream<_CharT, _Traits>&) { }

basic_ostream(const basic_ostream&) = delete;

basic_ostream(basic_ostream&& __rhs)
      : __ios_type()
      { __ios_type::move(__rhs); }

// 27.7.3.3 Assign/swap

basic_ostream& operator=(const basic_ostream&) = delete;

basic_ostream&
      operator=(basic_ostream&& __rhs)
      {
	swap(__rhs);
	return *this;
      }

void
      swap(basic_ostream& __rhs)
      { __ios_type::swap(__rhs); }
#endif

template<typename _ValueT>
	__ostream_type&
	_M_insert(_ValueT __v);
 };

/**
 * @brief Performs setup work for output streams.
 *
 * Objects of this class are created before all of the standard
 * inserters are run. It is responsible for exception-safe prefix and
 * suffix operations.
 */
 template <typename _CharT, typename _Traits>
 class basic_ostream<_CharT, _Traits>::sentry
 {
 // Data Members.
 bool 				_M_ok;
 basic_ostream<_CharT, _Traits>& 	_M_os;

public:
 /**
 * @brief The constructor performs preparatory work.
 * @param __os The output stream to guard.
 *
 * If the stream state is good (@a __os.good() is true), then if the
 * stream is tied to another output stream, @c is.tie()->flush()
 * is called to synchronize the output sequences.
 *
 * If the stream state is still good, then the sentry state becomes
 * true (@a okay).
 */
 explicit
 sentry(basic_ostream<_CharT, _Traits>& __os);

#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wdeprecated-declarations"
      /**
       *  @brief  Possibly flushes the stream.
       *
       *  If @c ios_base::unitbuf is set in @c os.flags(), and
       *  @c std::uncaught_exception() is true, the sentry destructor calls
       *  @c flush() on the output stream.
      */
      ~sentry()
      {
	// XXX MT
	if (bool(_M_os.flags() & ios_base::unitbuf) && !uncaught_exception())
	  {
	    // Can't call flush directly or else will get into recursive lock.
	    if (_M_os.rdbuf() && _M_os.rdbuf()->pubsync() == -1)
	      _M_os.setstate(ios_base::badbit);
	  }
      }
#pragma GCC diagnostic pop

/**
       *  @brief  Quick status checking.
       *  @return  The sentry state.
       *
       *  For ease of use, sentries may be converted to booleans.  The
       *  return value is that of the sentry state (true == okay).
      */
#if __cplusplus >= 201103L
      explicit
#endif
      operator bool() const
      { return _M_ok; }
    };

///@{
 /**
 * @brief Character inserters
 * @param __out An output stream.
 * @param __c A character.
 * @return out
 *
 * Behaves like one of the formatted arithmetic inserters described in
 * std::basic_ostream. After constructing a sentry object with good
 * status, this function inserts a single character and any required
 * padding (as determined by [22.2.2.2.2]). @c __out.width(0) is then
 * called.
 *
 * If @p __c is of type @c char and the character type of the stream is not
 * @c char, the character is widened before insertion.
 */
 template<typename _CharT, typename _Traits>
 inline basic_ostream<_CharT, _Traits>&
 operator<<(basic_ostream<_CharT, _Traits>& __out, _CharT __c)
 { return __ostream_insert(__out, &__c, 1); }

template<typename _CharT, typename _Traits>
 inline basic_ostream<_CharT, _Traits>&
 operator<<(basic_ostream<_CharT, _Traits>& __out, char __c)
 { return (__out << __out.widen(__c)); }

// Specialization
 template<typename _Traits>
 inline basic_ostream<char, _Traits>&
 operator<<(basic_ostream<char, _Traits>& __out, char __c)
 { return __ostream_insert(__out, &__c, 1); }

// Signed and unsigned
 template<typename _Traits>
 inline basic_ostream<char, _Traits>&
 operator<<(basic_ostream<char, _Traits>& __out, signed char __c)
 { return (__out << static_cast<char>(__c)); }

template<typename _Traits>
 inline basic_ostream<char, _Traits>&
 operator<<(basic_ostream<char, _Traits>& __out, unsigned char __c)
 { return (__out << static_cast<char>(__c)); }

#if __cplusplus > 201703L
  // The following deleted overloads prevent formatting character values as
  // numeric values.

template<typename _Traits>
 basic_ostream<char, _Traits>&
 operator<<(basic_ostream<char, _Traits>&, wchar_t) = delete;

#ifdef _GLIBCXX_USE_CHAR8_T
 template<typename _Traits>
 basic_ostream<char, _Traits>&
 operator<<(basic_ostream<char, _Traits>&, char8_t) = delete;
#endif

template<typename _Traits>
 basic_ostream<char, _Traits>&
 operator<<(basic_ostream<char, _Traits>&, char16_t) = delete;

template<typename _Traits>
 basic_ostream<char, _Traits>&
 operator<<(basic_ostream<char, _Traits>&, char32_t) = delete;

#ifdef _GLIBCXX_USE_WCHAR_T
#ifdef _GLIBCXX_USE_CHAR8_T
 template<typename _Traits>
 basic_ostream<wchar_t, _Traits>&
 operator<<(basic_ostream<wchar_t, _Traits>&, char8_t) = delete;
#endif // _GLIBCXX_USE_CHAR8_T

template<typename _Traits>
 basic_ostream<wchar_t, _Traits>&
 operator<<(basic_ostream<wchar_t, _Traits>&, char16_t) = delete;

template<typename _Traits>
 basic_ostream<wchar_t, _Traits>&
 operator<<(basic_ostream<wchar_t, _Traits>&, char32_t) = delete;
#endif // _GLIBCXX_USE_WCHAR_T
#endif // C++20
 ///@}

///@{
 /**
 * @brief String inserters
 * @param __out An output stream.
 * @param __s A character string.
 * @return out
 * @pre @p __s must be a non-NULL pointer
 *
 * Behaves like one of the formatted arithmetic inserters described in
 * std::basic_ostream. After constructing a sentry object with good
 * status, this function inserts @c traits::length(__s) characters starting
 * at @p __s, widened if necessary, followed by any required padding (as
 * determined by [22.2.2.2.2]). @c __out.width(0) is then called.
 */
 template<typename _CharT, typename _Traits>
 inline basic_ostream<_CharT, _Traits>&
 operator<<(basic_ostream<_CharT, _Traits>& __out, const _CharT* __s)
 {
 if (!__s)
	__out.setstate(ios_base::badbit);
 else
	__ostream_insert(__out, __s,
			 static_cast<streamsize>(_Traits::length(__s)));
 return __out;
 }

template<typename _CharT, typename _Traits>
 basic_ostream<_CharT, _Traits> &
 operator<<(basic_ostream<_CharT, _Traits>& __out, const char* __s);

// Partial specializations
 template<typename _Traits>
 inline basic_ostream<char, _Traits>&
 operator<<(basic_ostream<char, _Traits>& __out, const char* __s)
 {
 if (!__s)
	__out.setstate(ios_base::badbit);
 else
	__ostream_insert(__out, __s,
			 static_cast<streamsize>(_Traits::length(__s)));
 return __out;
 }

// Signed and unsigned
 template<typename _Traits>
 inline basic_ostream<char, _Traits>&
 operator<<(basic_ostream<char, _Traits>& __out, const signed char* __s)
 { return (__out << reinterpret_cast<const char*>(__s)); }

template<typename _Traits>
 inline basic_ostream<char, _Traits> &
 operator<<(basic_ostream<char, _Traits>& __out, const unsigned char* __s)
 { return (__out << reinterpret_cast<const char*>(__s)); }

#if __cplusplus > 201703L
   // The following deleted overloads prevent formatting strings as
   // pointer values.

template<typename _Traits>
 basic_ostream<char, _Traits>&
 operator<<(basic_ostream<char, _Traits>&, const wchar_t*) = delete;

#ifdef _GLIBCXX_USE_CHAR8_T
 template<typename _Traits>
 basic_ostream<char, _Traits>&
 operator<<(basic_ostream<char, _Traits>&, const char8_t*) = delete;
#endif // _GLIBCXX_USE_CHAR8_T

template<typename _Traits>
 basic_ostream<char, _Traits>&
 operator<<(basic_ostream<char, _Traits>&, const char16_t*) = delete;

template<typename _Traits>
 basic_ostream<char, _Traits>&
 operator<<(basic_ostream<char, _Traits>&, const char32_t*) = delete;

template<typename _Traits>
 basic_ostream<wchar_t, _Traits>&
 operator<<(basic_ostream<wchar_t, _Traits>&, const char16_t*) = delete;

template<typename _Traits>
 basic_ostream<wchar_t, _Traits>&
 operator<<(basic_ostream<wchar_t, _Traits>&, const char32_t*) = delete;
#endif // _GLIBCXX_USE_WCHAR_T
#endif // C++20
 ///@}

// Standard basic_ostream manipulators

/**
 * @brief Write a newline and flush the stream.
 *
 * This manipulator is often mistakenly used when a simple newline is
 * desired, leading to poor buffering performance. See
 * https://gcc.gnu.org/onlinedocs/libstdc++/manual/streambufs.html#io.streambuf.buffering
 * for more on this subject.
 */
 template<typename _CharT, typename _Traits>
 inline basic_ostream<_CharT, _Traits>&
 endl(basic_ostream<_CharT, _Traits>& __os)
 { return flush(__os.put(__os.widen('\n'))); }

/**
 * @brief Write a null character into the output sequence.
 *
 * Null character is @c CharT() by definition. For CharT
 * of @c char, this correctly writes the ASCII @c NUL character
 * string terminator.
 */
 template<typename _CharT, typename _Traits>
 inline basic_ostream<_CharT, _Traits>&
 ends(basic_ostream<_CharT, _Traits>& __os)
 { return __os.put(_CharT()); }

/**
 * @brief Flushes the output stream.
 *
 * This manipulator simply calls the stream's @c flush() member function.
 */
 template<typename _CharT, typename _Traits>
 inline basic_ostream<_CharT, _Traits>&
 flush(basic_ostream<_CharT, _Traits>& __os)
 { return __os.flush(); }

#if __cplusplus >= 201103L
  // C++11 27.7.3.9 Rvalue stream insertion [ostream.rvalue]
  // _GLIBCXX_RESOLVE_LIB_DEFECTS
  // 1203. More useful rvalue stream insertion

#if __cpp_lib_concepts
 // Use concepts if possible because they're cheaper to evaluate.
 template<typename _Tp>
 concept __derived_from_ios_base = is_class_v<_Tp>
 && (!is_same_v<_Tp, ios_base>)
 && requires (_Tp* __t, ios_base* __b) { __b = __t; };

template<typename _Os, typename _Tp>
 requires __derived_from_ios_base<_Os>
 && requires (_Os& __os, const _Tp& __t) { __os << __t; }
 using __rvalue_stream_insertion_t = _Os&&;
#else
 template<typename _Tp>
 using _Require_derived_from_ios_base
 = _Require<is_class<_Tp>, __not_<is_same<_Tp, ios_base>>,
		 is_convertible<typename add_pointer<_Tp>::type, ios_base*>>;

template<typename _Os, typename _Tp,
	 typename = _Require_derived_from_ios_base<_Os>,
	 typename
	 = decltype(std::declval<_Os&>() << std::declval<const _Tp&>())>
 using __rvalue_stream_insertion_t = _Os&&;
#endif

/**
 * @brief Generic inserter for rvalue stream
 * @param __os An input stream.
 * @param __x A reference to the object being inserted.
 * @return __os
 *
 * This is just a forwarding function to allow insertion to
 * rvalue streams since they won't bind to the inserter functions
 * that take an lvalue reference.
 */
 template<typename _Ostream, typename _Tp>
 inline __rvalue_stream_insertion_t<_Ostream, _Tp>
 operator<<(_Ostream&& __os, const _Tp& __x)
 {
 __os << __x;
 return std::move(__os);
 }

#if __cplusplus > 201703L && _GLIBCXX_USE_CXX11_ABI
 template<typename _CharT, typename _Traits>
 class __syncbuf_base : public basic_streambuf<_CharT, _Traits>
 {
 public:
 static bool*
 _S_get(basic_streambuf<_CharT, _Traits>* __buf [[maybe_unused]]) noexcept
 {
#if __cpp_rtti
	if (auto __p = dynamic_cast<__syncbuf_base*>(__buf))
	 return &__p->_M_emit_on_sync;
#endif
	return nullptr;
 }

protected:
 __syncbuf_base(basic_streambuf<_CharT, _Traits>* __w = nullptr)
 : _M_wrapped(__w)
 { }

basic_streambuf<_CharT, _Traits>* _M_wrapped = nullptr;
 bool _M_emit_on_sync = false;
 bool _M_needs_sync = false;
 };

template<typename _CharT, typename _Traits>
 inline basic_ostream<_CharT, _Traits>&
 emit_on_flush(basic_ostream<_CharT, _Traits>& __os)
 {
 if (bool* __flag = __syncbuf_base<_CharT, _Traits>::_S_get(__os.rdbuf()))
	*__flag = true;
 return __os;
 }

template<typename _CharT, typename _Traits>
 inline basic_ostream<_CharT, _Traits>&
 noemit_on_flush(basic_ostream<_CharT, _Traits>& __os)
 {
 if (bool* __flag = __syncbuf_base<_CharT, _Traits>::_S_get(__os.rdbuf()))
	*__flag = false;
 return __os;
 }

template<typename _CharT, typename _Traits>
 inline basic_ostream<_CharT, _Traits>&
 flush_emit(basic_ostream<_CharT, _Traits>& __os)
 {
 struct _Restore
 {
	~_Restore() { *_M_flag = _M_prev; }

bool _M_prev = false;
	bool* _M_flag = &_M_prev;
      } __restore;

if (bool* __flag = __syncbuf_base<_CharT, _Traits>::_S_get(__os.rdbuf()))
	{
	 __restore._M_prev = *__flag;
	 __restore._M_flag = __flag;
	 *__flag = true;
	}

__os.flush();
      return __os;
    }

#endif // C++20

#endif // C++11

_GLIBCXX_END_NAMESPACE_VERSION
} // namespace std

#include <bits/ostream.tcc>

#endif	/* _GLIBCXX_OSTREAM */