[Patch, libstdc++/64140] Fix unmatched prefix in regex

[Tim Shen]

Bootstrapped and tested.

Thanks!


-- 
Regards,
Tim Shen

commit 942a5f8e5f4fc4af4f1a18f15b529166e9bdd3ac
Author: timshen <tims...@google.com>
Date:   Wed Dec 3 09:36:04 2014 -0800

        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.

diff --git a/libstdc++-v3/include/bits/regex.tcc 
b/libstdc++-v3/include/bits/regex.tcc
index 94cbbfa..9692402 100644
--- a/libstdc++-v3/include/bits/regex.tcc
+++ b/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;
            }
diff --git 
a/libstdc++-v3/testsuite/28_regex/iterators/regex_iterator/char/64140.cc 
b/libstdc++-v3/testsuite/28_regex/iterators/regex_iterator/char/64140.cc
new file mode 100644
index 0000000..32b7e24
--- /dev/null
+++ b/libstdc++-v3/testsuite/28_regex/iterators/regex_iterator/char/64140.cc
@@ -0,0 +1,53 @@
+// { 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;
+}