From 132cbde24aac4ccb0d2a5c4581b32828ebea41a2 Mon Sep 17 00:00:00 2001 From: Jonathan Wakely Date: Mon, 23 Oct 2017 18:47:10 +0100 Subject: [PATCH] PR libstdc++/81395 fix crash when write follows large read Backport from mainline 2017-07-18 Jonathan Wakely 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. From-SVN: r254018 --- libstdc++-v3/ChangeLog | 8 ++++ libstdc++-v3/include/bits/fstream.tcc | 2 +- .../27_io/basic_filebuf/sgetn/char/81395.cc | 46 +++++++++++++++++++ 3 files changed, 55 insertions(+), 1 deletion(-) create mode 100644 libstdc++-v3/testsuite/27_io/basic_filebuf/sgetn/char/81395.cc diff --git a/libstdc++-v3/ChangeLog b/libstdc++-v3/ChangeLog index 12f5fb9de017..7426781e11c2 100644 --- a/libstdc++-v3/ChangeLog +++ b/libstdc++-v3/ChangeLog @@ -1,5 +1,13 @@ 2017-10-23 Jonathan Wakely + Backport from mainline + 2017-07-18 Jonathan Wakely + + 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. + Backport from mainline 2017-10-19 Jonathan Wakely diff --git a/libstdc++-v3/include/bits/fstream.tcc b/libstdc++-v3/include/bits/fstream.tcc index a6e83f7ed901..3a5246f655a5 100644 --- a/libstdc++-v3/include/bits/fstream.tcc +++ b/libstdc++-v3/include/bits/fstream.tcc @@ -699,7 +699,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION if (__n == 0) { - _M_set_buffer(0); + // Set _M_reading. Buffer is already in initial 'read' mode. _M_reading = true; } else if (__len == 0) diff --git a/libstdc++-v3/testsuite/27_io/basic_filebuf/sgetn/char/81395.cc b/libstdc++-v3/testsuite/27_io/basic_filebuf/sgetn/char/81395.cc new file mode 100644 index 000000000000..ea8dbc1259b5 --- /dev/null +++ b/libstdc++-v3/testsuite/27_io/basic_filebuf/sgetn/char/81395.cc @@ -0,0 +1,46 @@ +// 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 +// . + +// { dg-require-fileio "" } + +// PR libstdc++/81395 + +#include +#include // for std::memset +#include // 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(); +} -- 2.47.2