[Patch, libstdc++/68863] Let lookahead regex use captured contents

[Tim Shen]

This is a one-line quick fix for correctness.

I bootstrapped trunk and tested on x86_64-pc-linux-gnu, but I wish I
can backport it at least to gcc-5-branch.

Thanks!


-- 
Regards,
Tim Shen
-------------- next part --------------
commit 46b13f280fcbec6293ad614fb8f30f5882c7106d
Author: Tim Shen <timshen@google.com>
Date:   Fri Dec 11 21:34:38 2015 -0800

    2015-12-12  Tim Shen  <timshen@google.com>
    
    	PR libstdc++/68863
    	* include/bits/regex_executor.tcc
    	* testsuite/28_regex/algorithms/regex_match/ecma/char/68863.cc

diff --git a/libstdc++-v3/include/bits/regex_executor.tcc b/libstdc++-v3/include/bits/regex_executor.tcc
index a13f0d5..f5be4d7 100644
--- a/libstdc++-v3/include/bits/regex_executor.tcc
+++ b/libstdc++-v3/include/bits/regex_executor.tcc
@@ -147,7 +147,10 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     bool _Executor<_BiIter, _Alloc, _TraitsT, __dfs_mode>::
     _M_lookahead(_StateIdT __next)
     {
-      _ResultsVec __what(_M_cur_results.size());
+      // Backreferences may refer to captured content.
+      // We may want to make this faster by not copying,
+      // but let's not be clever prematurely.
+      _ResultsVec __what(_M_cur_results);
       _Executor __sub(_M_current, _M_end, __what, _M_re, _M_flags);
       __sub._M_states._M_start = __next;
       if (__sub._M_search_from_first())
diff --git a/libstdc++-v3/testsuite/28_regex/algorithms/regex_match/ecma/char/68863.cc b/libstdc++-v3/testsuite/28_regex/algorithms/regex_match/ecma/char/68863.cc
new file mode 100644
index 0000000..9e7a9a7
--- /dev/null
+++ b/libstdc++-v3/testsuite/28_regex/algorithms/regex_match/ecma/char/68863.cc
@@ -0,0 +1,43 @@
+// { dg-options "-std=gnu++11" }
+
+// Copyright (C) 2015 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/>.
+
+// 28.11.2 regex_match
+
+#include <regex>
+#include <testsuite_hooks.h>
+#include <testsuite_regex.h>
+
+using namespace __gnu_test;
+using namespace std;
+
+// libstdc++/68863
+void
+test01()
+{
+  bool test __attribute__((unused)) = true;
+
+  VERIFY(!std::regex_match("aa", std::regex("(.)(?!\\1).")));
+}
+
+int
+main()
+{
+  test01();
+  return 0;
+}