ostream
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// Output streams -*- C++ -*-
// Copyright (C) 1997-2025 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
#ifdef _GLIBCXX_SYSHDR
#pragma GCC system_header
#endif
#include <bits/requires_hosted.h> // iostreams
#include <bits/ostream.h>
#if __cplusplus > 202002L
# include <format>
#endif
# define __glibcxx_want_print
#include <bits/version.h> // __glibcxx_syncbuf
namespace std _GLIBCXX_VISIBILITY(default)
{
_GLIBCXX_BEGIN_NAMESPACE_VERSION
// 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.
*
* <em>Null character</em> 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(); }
#ifdef __glibcxx_syncbuf // C++ >= 20 && HOSTED && CXX11ABI
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 // __glibcxx_syncbuf
#if __cpp_lib_print // C++ >= 23
inline void
vprint_nonunicode(ostream& __os, string_view __fmt, format_args __args)
{
ostream::sentry __cerb(__os);
if (__cerb)
{
__format::_Str_sink<char> __buf;
std::vformat_to(__buf.out(), __os.getloc(), __fmt, __args);
auto __out = __buf.view();
__try
{
std::__ostream_write(__os, __out.data(), __out.size());
}
__catch(const __cxxabiv1::__forced_unwind&)
{
__os._M_setstate(ios_base::badbit);
__throw_exception_again;
}
__catch(...)
{ __os._M_setstate(ios_base::badbit); }
}
}
inline void
vprint_unicode(ostream& __os, string_view __fmt, format_args __args)
{
#if !defined(_WIN32) || defined(__CYGWIN__)
// For most targets we don't need to do anything special to write
// Unicode to a terminal.
std::vprint_nonunicode(__os, __fmt, __args);
#else
ostream::sentry __cerb(__os);
if (__cerb)
{
__format::_Str_sink<char> __buf;
std::vformat_to(__buf.out(), __os.getloc(), __fmt, __args);
auto __out = __buf.view();
void* __open_terminal(streambuf*);
error_code __write_to_terminal(void*, span<char>);
// If stream refers to a terminal, write a Unicode string to it.
if (auto __term = __open_terminal(__os.rdbuf()))
{
#if !defined(_WIN32) || defined(__CYGWIN__)
// For POSIX, __open_terminal(streambuf*) uses fdopen to open a
// new file, so we would need to close it here. This code is not
// actually compiled because it's inside an #ifdef _WIN32 group,
// but just in case that changes in future ...
struct _Guard
{
_Guard(void* __p) : _M_f((FILE*)__p) { }
~_Guard() { std::fclose(_M_f); }
_Guard(_Guard&&) = delete;
_Guard& operator=(_Guard&&) = delete;
FILE* _M_f;
};
_Guard __g(__term);
#endif
ios_base::iostate __err = ios_base::goodbit;
__try
{
if (__os.rdbuf()->pubsync() == -1)
__err = ios::badbit;
else if (auto __e = __write_to_terminal(__term, __out))
if (__e != std::make_error_code(errc::illegal_byte_sequence))
__err = ios::badbit;
}
__catch(const __cxxabiv1::__forced_unwind&)
{
__os._M_setstate(ios_base::badbit);
__throw_exception_again;
}
__catch(...)
{ __os._M_setstate(ios_base::badbit); }
if (__err)
__os.setstate(__err);
return;
}
// Otherwise just insert the string as vprint_nonunicode does.
__try
{
std::__ostream_write(__os, __out.data(), __out.size());
}
__catch(const __cxxabiv1::__forced_unwind&)
{
__os._M_setstate(ios_base::badbit);
__throw_exception_again;
}
__catch(...)
{ __os._M_setstate(ios_base::badbit); }
}
#endif // _WIN32
}
template<typename... _Args>
inline void
print(ostream& __os, format_string<_Args...> __fmt, _Args&&... __args)
{
auto __fmtargs = std::make_format_args(__args...);
if constexpr (__unicode::__literal_encoding_is_utf8())
std::vprint_unicode(__os, __fmt.get(), __fmtargs);
else
std::vprint_nonunicode(__os, __fmt.get(), __fmtargs);
}
template<typename... _Args>
inline void
println(ostream& __os, format_string<_Args...> __fmt, _Args&&... __args)
{
// _GLIBCXX_RESOLVE_LIB_DEFECTS
// 4088. println ignores the locale imbued in std::ostream
std::print(__os, "{}\n", std::format(__os.getloc(), __fmt,
std::forward<_Args>(__args)...));
}
// Defined for C++26, supported as an extension to C++23.
inline void println(ostream& __os)
{
#if defined(_WIN32) && !defined(__CYGWIN__)
if constexpr (__unicode::__literal_encoding_is_utf8())
std::vprint_unicode(__os, "\n", std::make_format_args());
else
#endif
__os.put('\n');
}
#endif // __cpp_lib_print
_GLIBCXX_END_NAMESPACE_VERSION
} // namespace std
#include <bits/ostream.tcc>
#endif /* _GLIBCXX_OSTREAM */
format
ostream.h
ostream.tcc
version.h
requires_hosted.h
std::make_error_code
error_code make_error_code(future_errc __errc) noexcept
Overload of make_error_code for future_errc.
Definition future:96
std::streambuf
basic_streambuf< char > streambuf
Base class for char buffers.
Definition iosfwd:139
std::ostream
basic_ostream< char > ostream
Base class for char output streams.
Definition iosfwd:145
std::forward
constexpr _Tp && forward(typename std::remove_reference< _Tp >::type &__t) noexcept
Forward an lvalue.
Definition move.h:72
std
ISO C++ entities toplevel namespace is std.
std::ends
basic_ostream< _CharT, _Traits > & ends(basic_ostream< _CharT, _Traits > &__os)
Write a null character into the output sequence.
Definition ostream:78
std::endl
basic_ostream< _CharT, _Traits > & endl(basic_ostream< _CharT, _Traits > &__os)
Write a newline and flush the stream.
Definition ostream:66
std::flush
basic_ostream< _CharT, _Traits > & flush(basic_ostream< _CharT, _Traits > &__os)
Flushes the output stream.
Definition ostream:88
std::basic_ios::widen
char_type widen(char __c) const
Widens characters.
Definition basic_ios.h:464
std::basic_ostream
Template class basic_ostream.
Definition ostream.h:67
std::basic_ostream::put
__ostream_type & put(char_type __c)
Simple insertion.
Definition ostream.tcc:158
std::basic_ostream::flush
__ostream_type & flush()
Synchronizing the stream buffer.
Definition ostream.tcc:226
std::error_code
Definition system_error:226
std::ios_base::iostate
_Ios_Iostate iostate
This is a bitmask type.
Definition ios_base.h:453
std::ios_base::goodbit
static const iostate goodbit
Indicates all is well.
Definition ios_base.h:468
std::ios_base::badbit
static const iostate badbit
Indicates a loss of integrity in an input or output sequence (such as an irrecoverable read error fro...
Definition ios_base.h:457