Implement LWG 3296 for basic_regex::assign

	* include/bits/regex.h
	(basic_regex::assign(const C*, size_t, flag_type)): Add default
	argument (LWG 3296).
	* testsuite/28_regex/basic_regex/assign/char/lwg3296.cc: New test.
	* testsuite/28_regex/basic_regex/assign/wchar_t/lwg3296.cc: New test.

From-SVN: r276121

libstdc++-v3/ChangeLog

+2019-09-25  Jonathan Wakely  <jwakely@redhat.com>
+
+	* include/bits/regex.h
+	(basic_regex::assign(const C*, size_t, flag_type)): Add default
+	argument (LWG 3296).
+	* testsuite/28_regex/basic_regex/assign/char/lwg3296.cc: New test.
+	* testsuite/28_regex/basic_regex/assign/wchar_t/lwg3296.cc: New test.
+
 2019-09-24  Jonathan Wakely  <jwakely@redhat.com>
 
 	* include/std/variant (variant::index()): Remove impossible case.

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

@@ -628,8 +628,10 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
        * expression pattern interpreted according to @p __flags.  If
        * regex_error is thrown, *this remains unchanged.
        */
+      // _GLIBCXX_RESOLVE_LIB_DEFECTS
+      // 3296. Inconsistent default argument for basic_regex<>::assign
       basic_regex&
-      assign(const _Ch_type* __p, std::size_t __len, flag_type __flags)
+      assign(const _Ch_type* __p, size_t __len, flag_type __flags = ECMAScript)
       { return this->assign(string_type(__p, __len), __flags); }
 
       /**

libstdc++-v3/testsuite/28_regex/basic_regex/assign/char/lwg3296.cc

+// Copyright (C) 2019 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()
+{
+  std::regex r("", std::regex_constants::grep);
+  r.assign("(.)[", 3);  // LWG 3296
+  VERIFY( r.flags() == std::regex_constants::ECMAScript );
+  VERIFY( r.mark_count() == 1 );
+}
+
+int
+main()
+{
+  test01();
+}

libstdc++-v3/testsuite/28_regex/basic_regex/assign/wchar_t/lwg3296.cc

+// Copyright (C) 2019 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()
+{
+  std::wregex r(L"", std::regex_constants::grep);
+  r.assign(L"(.)[", 3);  // LWG 3296
+  VERIFY( r.flags() == std::regex_constants::ECMAScript );
+  VERIFY( r.mark_count() == 1 );
+}
+
+int
+main()
+{
+  test01();
+}