[PATCH] PR libstdc++/88084 - Implement LWG 2777

[Jonathan Wakely]

	* include/std/string_view (basic_string_view::copy): Use traits to
	copy.
	* testsuite/21_strings/basic_string_view/operations/copy/char/2.cc:
	New test.
	* testsuite/21_strings/basic_string_view/operations/copy/wchar_t/2.cc:
	New test.

Tested x86_64-linux, committed to trunk.


-------------- next part --------------
commit 4fd4c4c6ad0d6cfa6d07402dab9705917fc9e101
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Mon Nov 19 10:11:23 2018 +0000

    PR libstdc++/88084 - Implement LWG 2777
    
            * include/std/string_view (basic_string_view::copy): Use traits to
            copy.
            * testsuite/21_strings/basic_string_view/operations/copy/char/2.cc:
            New test.
            * testsuite/21_strings/basic_string_view/operations/copy/wchar_t/2.cc:
            New test.

diff --git a/libstdc++-v3/include/std/string_view b/libstdc++-v3/include/std/string_view
index 9e0f6a723e4..dc2478d8d0e 100644
--- a/libstdc++-v3/include/std/string_view
+++ b/libstdc++-v3/include/std/string_view
@@ -236,9 +236,9 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 	__glibcxx_requires_string_len(__str, __n);
 	__pos = _M_check(__pos, "basic_string_view::copy");
 	const size_type __rlen = std::min(__n, _M_len - __pos);
-	for (auto __begin = this->_M_str + __pos,
-	     __end = __begin + __rlen; __begin != __end;)
-	  *__str++ = *__begin++;
+	// _GLIBCXX_RESOLVE_LIB_DEFECTS
+	// 2777. basic_string_view::copy should use char_traits::copy
+	traits_type::copy(__str, data() + __pos, __rlen);
 	return __rlen;
       }
 
diff --git a/libstdc++-v3/testsuite/21_strings/basic_string_view/operations/copy/char/2.cc b/libstdc++-v3/testsuite/21_strings/basic_string_view/operations/copy/char/2.cc
new file mode 100644
index 00000000000..b03edf77a4f
--- /dev/null
+++ b/libstdc++-v3/testsuite/21_strings/basic_string_view/operations/copy/char/2.cc
@@ -0,0 +1,56 @@
+// Copyright (C) 2018 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-options "-std=gnu++17" }
+// { dg-do run { target c++17 } }
+
+#include <string_view>
+#include <testsuite_hooks.h>
+
+using char_type = char;
+
+// PR libstdc++/88084
+// LWG 2777. basic_string_view::copy should use char_traits::copy
+
+struct traits : std::char_traits<char_type>
+{
+  static char_type*
+  copy(char_type* s, const char_type* p, std::size_t n)
+  {
+    while (n--)
+      *s++ = 'X';
+    return s;
+  }
+};
+
+void
+test01()
+{
+  std::basic_string_view<char_type, traits> s = "abc";
+  char_type buf[3] = { '1', '2', '3' };
+  auto len = s.copy(buf, 3, 1);
+  VERIFY( len == 2 );
+  VERIFY( buf[0] == 'X' );
+  VERIFY( buf[1] == 'X' );
+  VERIFY( buf[2] == '3' );
+}
+
+int
+main()
+{
+  test01();
+}
diff --git a/libstdc++-v3/testsuite/21_strings/basic_string_view/operations/copy/wchar_t/2.cc b/libstdc++-v3/testsuite/21_strings/basic_string_view/operations/copy/wchar_t/2.cc
new file mode 100644
index 00000000000..bf192aa8870
--- /dev/null
+++ b/libstdc++-v3/testsuite/21_strings/basic_string_view/operations/copy/wchar_t/2.cc
@@ -0,0 +1,56 @@
+// Copyright (C) 2018 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-options "-std=gnu++17" }
+// { dg-do run { target c++17 } }
+
+#include <string_view>
+#include <testsuite_hooks.h>
+
+using char_type = wchar_t;
+
+// PR libstdc++/88084
+// LWG 2777. basic_string_view::copy should use char_traits::copy
+
+struct traits : std::char_traits<char_type>
+{
+  static char_type*
+  copy(char_type* s, const char_type* p, std::size_t n)
+  {
+    while (n--)
+      *s++ = 'X';
+    return s;
+  }
+};
+
+void
+test01()
+{
+  std::basic_string_view<char_type, traits> s = L"abc";
+  char_type buf[3] = { L'1', L'2', L'3' };
+  auto len = s.copy(buf, 3, 1);
+  VERIFY( len == 2 );
+  VERIFY( buf[0] == L'X' );
+  VERIFY( buf[1] == L'X' );
+  VERIFY( buf[2] == L'3' );
+}
+
+int
+main()
+{
+  test01();
+}