Patchwork [v3] Fix libstdc++/50119

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Submitter Paolo Carlini
Date Aug. 18, 2011, 4:35 p.m.
Message ID <4E4D3F43.4020306@oracle.com>
Download mbox | patch
Permalink /patch/110534/
State New
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Comments

Paolo Carlini - Aug. 18, 2011, 4:35 p.m.
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.carlini@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.

Patch

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;
+}