PR libstdc++/83598 don't modify flags passed to std::basic_regex constructors

	PR libstdc++/83598
	* include/bits/regex.h (basic_regex): Don't modify flags passed to
	constructors.
	* testsuite/28_regex/basic_regex/ctors/83598.cc: New test.

From-SVN: r256013

libstdc++-v3/ChangeLog

 2017-12-27  Jonathan Wakely  <jwakely@redhat.com>
 
+	PR libstdc++/83598
+	* include/bits/regex.h (basic_regex): Don't modify flags passed to
+	constructors.
+	* testsuite/28_regex/basic_regex/ctors/83598.cc: New test.
+
 	PR libstdc++/83538
 	* doc/xml/manual/intro.xml: Document LWG 2306 change.
 	* include/bits/regex.h (match_results::reference): Change to

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

@@ -756,9 +756,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
       template<typename _FwdIter>
 	basic_regex(_FwdIter __first, _FwdIter __last, locale_type __loc,
 		    flag_type __f)
-	: _M_flags((__f & (ECMAScript | basic | extended | awk | grep | egrep))
-		   ? __f : (__f | ECMAScript)),
-	_M_loc(std::move(__loc)),
+	: _M_flags(__f), _M_loc(std::move(__loc)),
 	_M_automaton(__detail::__compile_nfa<_Rx_traits>(
 	  std::move(__first), std::move(__last), _M_loc, _M_flags))
 	{ }

libstdc++-v3/testsuite/28_regex/basic_regex/ctors/83598.cc

+// Copyright (C) 2017 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-do run { target c++11 } }
+
+#include <regex>
+#include <testsuite_hooks.h>
+
+void
+test01()
+{
+  // PR libstdc++83598
+  std::regex r1(".", std::regex_constants::syntax_option_type{});
+  VERIFY(r1.flags() == std::regex_constants::syntax_option_type{});
+  std::regex r2(".", std::regex_constants::icase);
+  VERIFY(r2.flags() == std::regex_constants::icase);
+}
+
+int
+main()
+{
+  test01();
+}