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PR libstdc++/81395 fix crash when write follows large read

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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: r250328
This commit is contained in:
Jonathan Wakely 2017-07-19 00:39:34 +01:00 • committed by Jonathan Wakely
parent 6033b55bd9
commit fddcd19abf
3 changed files with 54 additions and 1 deletions
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7
libstdc++-v3/ChangeLog
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@ -1,3 +1,10 @@
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

2
libstdc++-v3/include/bits/fstream.tcc
View file

@ -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)

46
libstdc++-v3/testsuite/27_io/basic_filebuf/sgetn/char/81395.cc Normal file
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@ -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
// <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();
}