re PR libstdc++/64140 (match_results.prefix() returns an incorrect result if…

re PR libstdc++/64140 (match_results.prefix() returns an incorrect result if regex_iterator holds a zero-length match)

	PR libstdc++/64140
	* include/bits/regex.tcc (regex_iterator<>::operator++): Update
	prefix.matched after modifying prefix.first.
	* testsuite/28_regex/iterators/regex_iterator/char/64140.cc: New
	testcase.

From-SVN: r218340

libstdc++-v3/ChangeLog

+2014-12-04  Tim Shen  <timshen@google.com>
+
+	PR libstdc++/64140
+	* include/bits/regex.tcc (regex_iterator<>::operator++): Update
+	prefix.matched after modifying prefix.first.
+	* testsuite/28_regex/iterators/regex_iterator/char/64140.cc: New
+	testcase.
+
 2014-12-03  François Dumont  <fdumont@gcc.gnu.org>
 
 	PR libstdc++/13631

libstdc++-v3/include/bits/regex.tcc

@@ -569,7 +569,9 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 				   | regex_constants::match_continuous))
 		    {
 		      _GLIBCXX_DEBUG_ASSERT(_M_match[0].matched);
-		      _M_match.at(_M_match.size()).first = __prefix_first;
+		      auto& __prefix = _M_match.at(_M_match.size());
+		      __prefix.first = __prefix_first;
+		      __prefix.matched = __prefix.first != __prefix.second;
 		      _M_match._M_in_iterator = true;
 		      _M_match._M_begin = _M_begin;
 		      return *this;
@@ -582,7 +584,9 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 	  if (regex_search(__start, _M_end, _M_match, *_M_pregex, _M_flags))
 	    {
 	      _GLIBCXX_DEBUG_ASSERT(_M_match[0].matched);
-	      _M_match.at(_M_match.size()).first = __prefix_first;
+	      auto& __prefix = _M_match.at(_M_match.size());
+	      __prefix.first = __prefix_first;
+	      __prefix.matched = __prefix.first != __prefix.second;
 	      _M_match._M_in_iterator = true;
 	      _M_match._M_begin = _M_begin;
 	    }

libstdc++-v3/testsuite/28_regex/iterators/regex_iterator/char/64140.cc

+// { dg-options "-std=gnu++11" }
+
+//
+// Copyright (C) 2014 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/>.
+
+// libstdc++/64140
+
+#include <regex>
+#include <testsuite_hooks.h>
+
+void
+test01()
+{
+  bool test __attribute__((unused)) = true;
+
+  const std::regex e("z*");
+  const std::string s("ab");
+
+  auto it = std::sregex_iterator(s.begin(), s.end(), e);
+  auto end = std::sregex_iterator();
+  VERIFY(it != end);
+  VERIFY(!it->prefix().matched);
+  ++it;
+  VERIFY(it != end);
+  VERIFY(it->prefix().matched);
+  ++it;
+  VERIFY(it != end);
+  VERIFY(it->prefix().matched);
+  ++it;
+  VERIFY(it == end);
+}
+
+int
+main()
+{
+  test01();
+  return 0;
+}