Here is an update to set _M_sbuf to null if the user advance too much.
Note that in this case the streambuf remains un-modified which is
different from the current implementation. I think it is another
enhancement.
I also change the Debug assertion message for something more dedicated
to std::advance algo.
François
On 10/14/19 10:12 PM, François Dumont wrote:
The same way I proposed to review std::copy overload for
istreambuf_iterator we can implement std::advance using pubseekoff.
It is both a cleaner implementation and avoids yet another friend
declaration.
* include/std/streambuf
(advance(istreambuf_iterator<>&, _Distance)): Remove friend
declaration.
* include/bits/streambuf_iterator.h (__copy_move_a2): Re-implement
using
streambuf pubseekoff.
Tested under Linux x86_64.
Ok to commit ?
François
diff --git a/libstdc++-v3/include/bits/streambuf_iterator.h b/libstdc++-v3/include/bits/streambuf_iterator.h
index 134b3486b9a..17dd3972d45 100644
--- a/libstdc++-v3/include/bits/streambuf_iterator.h
+++ b/libstdc++-v3/include/bits/streambuf_iterator.h
@@ -431,37 +431,26 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
__glibcxx_assert(__n > 0);
__glibcxx_requires_cond(!__i._M_at_eof(),
- _M_message(__gnu_debug::__msg_inc_istreambuf)
- ._M_iterator(__i));
-
- typedef istreambuf_iterator<_CharT> __is_iterator_type;
- typedef typename __is_iterator_type::traits_type traits_type;
- typedef typename __is_iterator_type::streambuf_type streambuf_type;
- typedef typename traits_type::int_type int_type;
- const int_type __eof = traits_type::eof();
-
- streambuf_type* __sb = __i._M_sbuf;
- while (__n > 0)
- {
- streamsize __size = __sb->egptr() - __sb->gptr();
- if (__size > __n)
+ _M_message(__gnu_debug::__msg_advance_oob)
+ ._M_iterator(__i)
+ ._M_integer(__n));
+
+ typedef basic_streambuf<_CharT> __streambuf_t;
+ typedef typename __streambuf_t::pos_type __pos_t;
+ __pos_t __cur_pos
+ = __i._M_sbuf->pubseekoff(0, ios_base::cur, ios_base::in);
+ __pos_t __new_pos
+ = __i._M_sbuf->pubseekoff(__n, ios_base::cur, ios_base::in);
+ __i._M_c = char_traits<_CharT>::eof();
+
+ if (__new_pos - __cur_pos != __n)
{
- __sb->__safe_gbump(__n);
- break;
- }
-
- __sb->__safe_gbump(__size);
- __n -= __size;
- if (traits_type::eq_int_type(__sb->underflow(), __eof))
- {
- __glibcxx_requires_cond(__n == 0,
- _M_message(__gnu_debug::__msg_inc_istreambuf)
- ._M_iterator(__i));
- break;
- }
+ __i._M_sbuf = 0;
+ __glibcxx_requires_cond(!__i._M_at_eof(),
+ _M_message(__gnu_debug::__msg_advance_oob)
+ ._M_iterator(__i)
+ ._M_integer(__n));
}
-
- __i._M_c = __eof;
}
// @} group iterators
diff --git a/libstdc++-v3/include/std/streambuf b/libstdc++-v3/include/std/streambuf
index 3442f19bd78..ef03da39bc2 100644
--- a/libstdc++-v3/include/std/streambuf
+++ b/libstdc++-v3/include/std/streambuf
@@ -155,11 +155,6 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
find(istreambuf_iterator<_CharT2>, istreambuf_iterator<_CharT2>,
const _CharT2&);
- template<typename _CharT2, typename _Distance>
- friend typename __gnu_cxx::__enable_if<__is_char<_CharT2>::__value,
- void>::__type
- advance(istreambuf_iterator<_CharT2>&, _Distance);
-
template<typename _CharT2, typename _Traits2>
friend basic_istream<_CharT2, _Traits2>&
operator>>(basic_istream<_CharT2, _Traits2>&, _CharT2*);
diff --git a/libstdc++-v3/testsuite/25_algorithms/advance/istreambuf_iterators/char/3.cc b/libstdc++-v3/testsuite/25_algorithms/advance/istreambuf_iterators/char/3.cc
new file mode 100644
index 00000000000..8763e7fa78e
--- /dev/null
+++ b/libstdc++-v3/testsuite/25_algorithms/advance/istreambuf_iterators/char/3.cc
@@ -0,0 +1,49 @@
+// Copyright (C) 2017-2019 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/>.
+
+// Debug mode would detect the invalid std::advance call.
+// { dg-require-normal-mode "" }
+
+#include <iterator>
+#include <sstream>
+#include <algorithm>
+
+#include <testsuite_hooks.h>
+
+void test01()
+{
+ using namespace std;
+
+ typedef istreambuf_iterator<char> in_iterator_type;
+
+ const char data1[] = "Drei Phantasien nach Friedrich Holderlin";
+ istringstream iss1(data1);
+ in_iterator_type beg1(iss1);
+ in_iterator_type end1;
+
+ VERIFY( beg1 != end1 );
+
+ advance(beg1, sizeof(data1));
+
+ VERIFY( beg1 == end1 );
+}
+
+int main()
+{
+ test01();
+ return 0;
+}
