Merge 2018-03 LWG Motion 14

Author: zygoloid

source/iostreams.tex

@@ -4105,6 +4105,13 @@
   template<class charT, class traits>
     basic_ostream<charT, traits>& flush(basic_ostream<charT, traits>& os);
 
+  template<class charT, class traits>
+    basic_ostream<charT, traits>& emit_on_flush(basic_ostream<charT, traits>& os);
+  template<class charT, class traits>
+    basic_ostream<charT, traits>& noemit_on_flush(basic_ostream<charT, traits>& os);
+  template<class charT, class traits>
+    basic_ostream<charT, traits>& flush_emit(basic_ostream<charT, traits>& os);
+
   template<class charT, class traits, class T>
     basic_ostream<charT, traits>& operator<<(basic_ostream<charT, traits>&& os, const T& x);
 }
@@ -6677,6 +6684,72 @@
 \tcode{os}.
 \end{itemdescr}
 
+\indexlibrary{\idxcode{emit_on_flush}}%
+\begin{itemdecl}
+template<class charT, class traits>
+  basic_ostream<charT, traits>& emit_on_flush(basic_ostream<charT, traits>& os);
+\end{itemdecl}
+
+\begin{itemdescr}
+\pnum
+\effects
+If \tcode{os.rdbuf()} is a
+\tcode{basic_osyncbuf<charT, traits, Allocator>*},
+called \tcode{buf} for the purpose of exposition,
+calls \tcode{buf->set_emit_on_sync(true)}.
+Otherwise this manipulator has no effect.
+\begin{note}
+To work around the issue that the
+\tcode{Allocator} template argument can not be deduced,
+implementations can introduce an intermediate base class
+to \tcode{basic_osyncbuf} that manages its \tcode{emit_on_sync} flag.
+\end{note}
+
+\pnum
+\returns
+\tcode{os}.
+\end{itemdescr}
+
+\indexlibrary{\idxcode{noemit_on_flush}}%
+\begin{itemdecl}
+template<class charT, class traits>
+  basic_ostream<charT, traits>& noemit_on_flush(basic_ostream<charT, traits>& os);
+\end{itemdecl}
+
+\begin{itemdescr}
+\pnum
+\effects
+If \tcode{os.rdbuf()} is a
+\tcode{basic_osyncbuf<charT, traits, Allocator>*},
+called \tcode{buf} for the purpose of exposition,
+calls \tcode{buf->set_emit_on_sync(false)}.
+Otherwise this manipulator has no effect.
+
+\pnum
+\returns
+\tcode{os}.
+\end{itemdescr}
+
+\indexlibrary{\idxcode{flush_emit}}%
+\begin{itemdecl}
+template<class charT, class traits>
+  basic_ostream<charT, traits>& flush_emit(basic_ostream<charT, traits>& os);
+\end{itemdecl}
+
+\begin{itemdescr}
+\pnum
+\effects
+Calls \tcode{os.flush()}.
+Then, if \tcode{os.rdbuf()} is a
+\tcode{basic_osyncbuf<charT, traits, Allocator>*},
+called \tcode{buf} for the purpose of exposition,
+calls \tcode{buf->emit()}.
+
+\pnum
+\returns
+\tcode{os}.
+\end{itemdescr}
+
 \rSec3[ostream.rvalue]{Rvalue stream insertion}
 
 \indexlibrarymember{operator<<}{basic_ostream}%
@@ -9967,6 +10040,8 @@
 \indexlibrary{\idxcode{osyncstream}}%
 \indexlibrary{\idxcode{wosyncstream}}%
 \begin{codeblock}
+#include <ostream>  // see \ref{ostream.syn}
+
 namespace std {
   template<class charT, class traits, class Allocator>
     class basic_syncbuf;