re PR libstdc++/58358 (search_n has a Complexity violation for random access iterator)

2013-09-11  Mitsuru Kariya  <kariya_mitsuru@hotmail.com>
	    Chris Jefferson  <chris@bubblescope.net>

	PR libstdc++/58358
	* include/bits/stl_algo.h (search_n): Fix to guarantee a number
	of comparisons <= number of elements in the range.
	* testsuite/25_algorithms/search_n/58358.cc: New.
	* testsuite/25_algorithms/search_n/iterator.cc: Extend.

Co-Authored-By: Chris Jefferson <chris@bubblescope.net>

From-SVN: r202510

4 files changed, 80 insertions, 52 deletions

diff --git a/libstdc++-v3/ChangeLog b/libstdc++-v3/ChangeLog
index c6c8db1..6eab7c7 100644
--- a/libstdc++-v3/ChangeLog
+++ b/libstdc++-v3/ChangeLog
@@ -1,3 +1,12 @@
+2013-09-11  Mitsuru Kariya  <kariya_mitsuru@hotmail.com>
+	    Chris Jefferson  <chris@bubblescope.net>
+
+	PR libstdc++/58358
+	* include/bits/stl_algo.h (search_n): Fix to guarantee a number
+	of comparisons <= number of elements in the range.
+	* testsuite/25_algorithms/search_n/58358.cc: New.
+	* testsuite/25_algorithms/search_n/iterator.cc: Extend.
+
 2013-09-10  Ed Smith-Rowland  <3dw4rd@verizon.net>
 
 	* testsuite/28_regex/traits/wchar_t/value.cc: Change template args
diff --git a/libstdc++-v3/include/bits/stl_algo.h b/libstdc++-v3/include/bits/stl_algo.h
index 9d6b466..b06211e 100644
--- a/libstdc++-v3/include/bits/stl_algo.h
+++ b/libstdc++-v3/include/bits/stl_algo.h
@@ -385,38 +385,23 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 	_DistanceType;
 
       _DistanceType __tailSize = __last - __first;
-      const _DistanceType __pattSize = __count;
+      _DistanceType __remainder = __count;
 
-      if (__tailSize < __pattSize)
-        return __last;
-
-      const _DistanceType __skipOffset = __pattSize - 1;
-      _RandomAccessIter __lookAhead = __first + __skipOffset;
-      __tailSize -= __pattSize;
-
-      while (1) // the main loop...
+      while (__remainder <= __tailSize) // the main loop...
 	{
-	  // __lookAhead here is always pointing to the last element of next 
-	  // possible match.
-	  while (!(*__lookAhead == __val)) // the skip loop...
-	    {
-	      if (__tailSize < __pattSize)
-		return __last;  // Failure
-	      __lookAhead += __pattSize;
-	      __tailSize -= __pattSize;
-	    }
-	  _DistanceType __remainder = __skipOffset;
-	  for (_RandomAccessIter __backTrack = __lookAhead - 1; 
-	       *__backTrack == __val; --__backTrack)
+	  __first += __remainder;
+	  __tailSize -= __remainder;
+	  // __first here is always pointing to one past the last element of
+	  // next possible match.
+	  _RandomAccessIter __backTrack = __first; 
+	  while (*--__backTrack == __val)
 	    {
 	      if (--__remainder == 0)
-		return (__lookAhead - __skipOffset); // Success
+	        return (__first - __count); // Success
 	    }
-	  if (__remainder > __tailSize)
-	    return __last; // Failure
-	  __lookAhead += __remainder;
-	  __tailSize -= __remainder;
+	  __remainder = __count + 1 - (__first - __backTrack);
 	}
+      return __last; // Failure
     }
 
   // search_n
@@ -478,38 +463,23 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 	_DistanceType;
 
       _DistanceType __tailSize = __last - __first;
-      const _DistanceType __pattSize = __count;
+      _DistanceType __remainder = __count;
 
-      if (__tailSize < __pattSize)
-        return __last;
-
-      const _DistanceType __skipOffset = __pattSize - 1;
-      _RandomAccessIter __lookAhead = __first + __skipOffset;
-      __tailSize -= __pattSize;
-
-      while (1) // the main loop...
+      while (__remainder <= __tailSize) // the main loop...
 	{
-	  // __lookAhead here is always pointing to the last element of next 
-	  // possible match.
-	  while (!bool(__binary_pred(*__lookAhead, __val))) // the skip loop...
-	    {
-	      if (__tailSize < __pattSize)
-		return __last;  // Failure
-	      __lookAhead += __pattSize;
-	      __tailSize -= __pattSize;
-	    }
-	  _DistanceType __remainder = __skipOffset;
-	  for (_RandomAccessIter __backTrack = __lookAhead - 1; 
-	       __binary_pred(*__backTrack, __val); --__backTrack)
+	  __first += __remainder;
+	  __tailSize -= __remainder;
+	  // __first here is always pointing to one past the last element of
+	  // next possible match.
+	  _RandomAccessIter __backTrack = __first; 
+	  while (__binary_pred(*--__backTrack, __val))
 	    {
 	      if (--__remainder == 0)
-		return (__lookAhead - __skipOffset); // Success
+	        return (__first - __count); // Success
 	    }
-	  if (__remainder > __tailSize)
-	    return __last; // Failure
-	  __lookAhead += __remainder;
-	  __tailSize -= __remainder;
+	  __remainder = __count + 1 - (__first - __backTrack);
 	}
+      return __last; // Failure
     }
 
   // find_end for forward iterators.
diff --git a/libstdc++-v3/testsuite/25_algorithms/search_n/58358.cc b/libstdc++-v3/testsuite/25_algorithms/search_n/58358.cc
new file mode 100644
index 0000000..b5ae346
--- /dev/null
+++ b/libstdc++-v3/testsuite/25_algorithms/search_n/58358.cc
@@ -0,0 +1,41 @@
+// Copyright (C) 2013 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-options "-std=gnu++11" }
+
+// 25.1.9 [lib.alg.search]
+
+#include <algorithm>
+#include <vector>
+#include <testsuite_hooks.h>
+
+void test01()
+{
+  bool test __attribute__((unused)) = true;
+
+  std::vector<int> a{2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1};
+  int count = 0;
+  std::search_n(a.begin(), a.end(), 10, 1,
+		[&count](int t, int u) { ++count; return t == u; });
+  VERIFY( count <= 11 );
+}
+
+int main()
+{
+  test01();
+  return 0;
+}
diff --git a/libstdc++-v3/testsuite/25_algorithms/search_n/iterator.cc b/libstdc++-v3/testsuite/25_algorithms/search_n/iterator.cc
index 27cffe7..1061696 100644
--- a/libstdc++-v3/testsuite/25_algorithms/search_n/iterator.cc
+++ b/libstdc++-v3/testsuite/25_algorithms/search_n/iterator.cc
@@ -31,9 +31,11 @@
 int array1[11] = {0, 1, 0, 0, 1, 1, 0, 1, 1, 1, 0};
 int array2[TEST_DEPTH];
 
+int pred_count;
 bool 
 pred(int i, int j)
 {
+  ++pred_count;
   return i == j;
 }
 
@@ -90,16 +92,22 @@ int main()
 
 	    int* t1 = search_n(forwardcon.begin(),
 			       forwardcon.end(), j, 1).ptr;
+	    pred_count = 0;
 	    int* t2 = search_n(forwardcon.begin(),
 			       forwardcon.end(), j, 1, pred).ptr;
+	    VERIFY(pred_count <= i);
 	    int* t3 = search_n(bidircon.begin(),
 			       bidircon.end(), j, 1).ptr;
+	    pred_count = 0;
 	    int* t4 = search_n(bidircon.begin(),
 			       bidircon.end(), j, 1, pred).ptr;
+	    VERIFY(pred_count <= i);
 	    int* t5 = search_n(randomcon.begin(),
 			       randomcon.end(), j, 1).ptr;
+	    pred_count = 0;
 	    int* t6 = search_n(randomcon.begin(),
 			       randomcon.end(), j, 1, pred).ptr;
+	    VERIFY(pred_count <= i);
 	    VERIFY((t1 == t2) && (t2 == t3) && (t3 == t4) &&
 		   (t4 == t5) && (t5 == t6));
 	  }