+2017-07-18 Jonathan Wakely <jwakely@redhat.com>
+
+ PR libstdc++/81395
+ * include/bits/fstream.tcc (basic_filebuf::xsgetn): Don't set buffer
+ pointers for write mode after reading.
+ * testsuite/27_io/basic_filebuf/sgetn/char/81395.cc: New.
+
2017-07-18 François Dumont <fdumont@gcc.gnu.org>
* include/bits/stl_list.h
--- /dev/null
+// Copyright (C) 2017 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.
+
+// You should have received a copy of the GNU General Public License along
+// with this library; see the file COPYING3. If not see
+// <http://www.gnu.org/licenses/>.
+
+// { dg-do run }
+
+// PR libstdc++/81395
+
+#include <fstream>
+#include <cstring> // for std::memset
+#include <cstdio> // For BUFSIZ
+
+using std::memset;
+
+int main()
+{
+ {
+ std::filebuf fb;
+ fb.open("test.txt", std::ios::out);
+ char data[BUFSIZ];
+ memset(data, 'A', sizeof(data));
+ fb.sputn(data, sizeof(data));
+ }
+
+ std::filebuf fb;
+ fb.open("test.txt", std::ios::in|std::ios::out);
+ char buf[BUFSIZ];
+ memset(buf, 0, sizeof(buf));
+ fb.sgetn(buf, sizeof(buf));
+ // Switch from reading to writing without seeking first:
+ fb.sputn("B", 1);
+ fb.pubsync();
+}