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PR libstdc++/87784 fix dynamic_bitset::push_back 

Previously the _M_Nb member was incremented before calling
_M_unchecked_set which meant that the bit being set was out of bounds.
It either set the wrong bit in an allocated word, or accessed beyond the
end of the allocated memory in the _M_w vector. The fix for the bug is
to update the _M_Nb member after using it as an index.

As an optimisation, when a new block needs to be appended the call to
_M_unchecked_set can be avoided by appending a block with the least
significant bit already set to the desired value.

	PR libstdc++/87784
	* include/tr2/dynamic_bitset (dynamic_bitset::push_back): When there
	are no unused bits in the last block, append a new block with the
	right value so the bit doesn't need to be set. Only increment size
	after setting the new bit, not before.
	* testsuite/tr2/dynamic_bitset/pr87784.cc: New test.

From-SVN: r265625
This commit is contained in:
Jonathan Wakely 2018-10-30 14:49:32 +00:00 committed by Jonathan Wakely
parent 47abbc3196
commit c397f267f1
3 changed files with 89 additions and 3 deletions
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9
libstdc++-v3/ChangeLog
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@ -1,3 +1,12 @@
2018-10-30 Jonathan Wakely <jwakely@redhat.com>
PR libstdc++/87784
* include/tr2/dynamic_bitset (dynamic_bitset::push_back): When there
are no unused bits in the last block, append a new block with the
right value so the bit doesn't need to be set. Only increment size
after setting the new bit, not before.
* testsuite/tr2/dynamic_bitset/pr87784.cc: New test.
2018-10-29 David Malcolm <dmalcolm@redhat.com>
* testsuite/17_intro/using_namespace_std_exp_neg.cc: Remove

7
libstdc++-v3/include/tr2/dynamic_bitset
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@ -727,10 +727,11 @@ namespace tr2
void
push_back(bool __bit)
{
if (size_t __offset = this->size() % bits_per_block == 0)
this->_M_do_append_block(block_type(0), this->_M_Nb);
if (this->size() % bits_per_block == 0)
this->_M_do_append_block(block_type(__bit), this->_M_Nb);
else
this->_M_unchecked_set(this->_M_Nb, __bit);
++this->_M_Nb;
this->_M_unchecked_set(this->_M_Nb, __bit);
}
/**

76
libstdc++-v3/testsuite/tr2/dynamic_bitset/pr87784.cc Normal file
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@ -0,0 +1,76 @@
// Copyright (C) 2018 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 { target c++11 } }
#include <tr2/dynamic_bitset>
#include <testsuite_hooks.h>
void
test01()
{
std::tr2::dynamic_bitset<unsigned> b;
VERIFY( b.size() == 0 );
VERIFY( b.find_first() == b.size() );
b.push_back(0);
VERIFY( b.size() == 1 );
VERIFY( b.find_first() == b.size() );
b.push_back(0);
VERIFY( b.size() == 2 );
VERIFY( b.find_first() == b.size() );
b.push_back(1);
VERIFY( b.size() == 3 );
VERIFY( b.find_first() == b.size() - 1 );
b.push_back(1);
VERIFY( b.size() == 4 );
VERIFY( b.find_first() == b.size() - 2 );
b.push_back(0);
VERIFY( b.size() == 5 );
VERIFY( b.find_first() == b.size() - 3 );
b.clear();
VERIFY( b.size() == 0 );
VERIFY( b.find_first() == b.size() );
b.push_back(1);
VERIFY( b.size() == 1 );
VERIFY( b.find_first() == 0 );
b.push_back(1);
VERIFY( b.size() == 2 );
VERIFY( b.find_first() == 0 );
b.push_back(1);
VERIFY( b.size() == 3 );
VERIFY( b.find_first() == 0 );
b.clear();
b.append(2u);
VERIFY( b.size() == b.bits_per_block );
VERIFY( b.find_first() == 1 );
b <<= 1;
VERIFY( b.find_first() == 2 );
b <<= 3;
VERIFY( b.find_first() == 5 );
b <<= 6;
VERIFY( b.find_first() == 11 );
VERIFY( b.size() == b.bits_per_block );
}
int
main()
{
test01();
}