Hi,
note that the same issue affects the legacy __gnu_cxx::copy_n by HP/SGI
but certainly I'm not going to change it now after so many years of
people relying on that "broken" behavior.
Tested x86_64-linux, committed.
Paolo.
///////////////////////////////
2011-08-18 Paolo Carlini <paolo.carl...@oracle.com>
PR libstdc++/50119
* include/bits/stl_algo.h (__copy_n(_InputIterator, _Size,
_OutputIterator, input_iterator_tag)): Fix.
* testsuite/25_algorithms/copy_n/50119.cc: New.
Index: include/bits/stl_algo.h
===================================================================
--- include/bits/stl_algo.h (revision 177866)
+++ include/bits/stl_algo.h (working copy)
@@ -979,11 +979,17 @@
__copy_n(_InputIterator __first, _Size __n,
_OutputIterator __result, input_iterator_tag)
{
- for (; __n > 0; --__n)
+ if (__n > 0)
{
- *__result = *__first;
- ++__first;
- ++__result;
+ while (true)
+ {
+ *__result = *__first;
+ ++__result;
+ if (--__n > 0)
+ ++__first;
+ else
+ break;
+ }
}
return __result;
}
Index: testsuite/25_algorithms/copy_n/50119.cc
===================================================================
--- testsuite/25_algorithms/copy_n/50119.cc (revision 0)
+++ testsuite/25_algorithms/copy_n/50119.cc (revision 0)
@@ -0,0 +1,52 @@
+// { dg-options "-std=gnu++0x" }
+
+// Copyright (C) 2011 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 Pred 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/>.
+
+#include <algorithm>
+#include <vector>
+#include <sstream>
+#include <iterator>
+#include <testsuite_hooks.h>
+
+// libstdc++/50119
+void test01()
+{
+ using namespace std;
+ bool test __attribute__((unused)) = true;
+
+ vector<int> v;
+ istringstream s("1 2 3 4 5");
+
+ copy_n(istream_iterator<int>(s), 2, back_inserter(v));
+ VERIFY( v.size() == 2 );
+ VERIFY( v[0] == 1 );
+ VERIFY( v[1] == 2 );
+
+ copy_n(istream_iterator<int>(s), 2, back_inserter(v));
+ VERIFY( v.size() == 4 );
+ VERIFY( v[0] == 1 );
+ VERIFY( v[1] == 2 );
+ VERIFY( v[2] == 3 );
+ VERIFY( v[3] == 4 );
+}
+
+int main()
+{
+ test01();
+ return 0;
+}
