Implement P0457R2 String Prefix and Suffix Checking.

2018-11-30  Edward Smith-Rowland  <3dw4rd@verizon.net>

	Implement P0457R2 String Prefix and Suffix Checking.
	* include/bits/basic_string.h: Add starts_with, ends_with members.
	* include/std/string_view: Ditto.
	* testsuite/21_strings/basic_string/operations/starts_with/
	char/1.cc: New test.
	* testsuite/21_strings/basic_string/operations/starts_with/
	wchar_t/1.cc: New test.
	* testsuite/21_strings/basic_string/operations/ends_with/
	char/1.cc: New test.
	* testsuite/21_strings/basic_string/operations/ends_with/
	wchar_t/1.cc: New test.
	* testsuite/21_strings/basic_string_view/operations/starts_with/
	char/1.cc: New test.
	* testsuite/21_strings/basic_string_view/operations/starts_with/
	wchar_t/1.cc: New test.
	* testsuite/21_strings/basic_string_view/operations/ends_with/
	char/1.cc: New test.
	* testsuite/21_strings/basic_string_view/operations/ends_with/
	wchar_t/1.cc: New test.

From-SVN: r266674

11 files changed, 523 insertions, 1 deletions

diff --git a/libstdc++-v3/ChangeLog b/libstdc++-v3/ChangeLog
index 7b75b10..73d5b1c 100644
--- a/libstdc++-v3/ChangeLog
+++ b/libstdc++-v3/ChangeLog
@@ -1,5 +1,27 @@
 2018-11-30  Edward Smith-Rowland  <3dw4rd@verizon.net>
 
+	Implement P0457R2 String Prefix and Suffix Checking.
+	* include/bits/basic_string.h: Add starts_with, ends_with members.
+	* include/std/string_view: Ditto.
+	* testsuite/21_strings/basic_string/operations/starts_with/
+	char/1.cc: New test.
+	* testsuite/21_strings/basic_string/operations/starts_with/
+	wchar_t/1.cc: New test.
+	* testsuite/21_strings/basic_string/operations/ends_with/
+	char/1.cc: New test.
+	* testsuite/21_strings/basic_string/operations/ends_with/
+	wchar_t/1.cc: New test.
+	* testsuite/21_strings/basic_string_view/operations/starts_with/
+	char/1.cc: New test.
+	* testsuite/21_strings/basic_string_view/operations/starts_with/
+	wchar_t/1.cc: New test.
+	* testsuite/21_strings/basic_string_view/operations/ends_with/
+	char/1.cc: New test.
+	* testsuite/21_strings/basic_string_view/operations/ends_with/
+	wchar_t/1.cc: New test.
+
+2018-11-30  Edward Smith-Rowland  <3dw4rd@verizon.net>
+
 	Pre-emptively support P0646R1 for std container erasure.
 	* include/bits/erase_if.h: Accumulate and return number of erased nodes.
 	* include/std/forward_list (): Return number of erased items.
@@ -10,6 +32,7 @@
 	* include/std/unordered_map (): Ditto.
 	* include/std/unordered_set (): Ditto.
 	* include/std/vector (): Ditto.
+	* include/std/deque (): Ditto.
 	* testsuite/21_strings/basic_string/erasure.cc: Test number of erasures.
 	* testsuite/23_containers/deque/erasure.cc: Ditto.
 	* testsuite/23_containers/forward_list/erasure.cc: Ditto.
diff --git a/libstdc++-v3/include/bits/basic_string.h b/libstdc++-v3/include/bits/basic_string.h
index ae6530f..a2573d3 100644
--- a/libstdc++-v3/include/bits/basic_string.h
+++ b/libstdc++-v3/include/bits/basic_string.h
@@ -3038,6 +3038,32 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
       compare(size_type __pos, size_type __n1, const _CharT* __s,
 	      size_type __n2) const;
 
+#if __cplusplus > 201703L
+      bool
+      starts_with(basic_string_view<_CharT, _Traits> __x) const noexcept
+      { return __sv_type(this->data(), this->size()).starts_with(__x); }
+
+      bool
+      starts_with(_CharT __x) const noexcept
+      { return __sv_type(this->data(), this->size()).starts_with(__x); }
+
+      bool
+      starts_with(const _CharT* __x) const noexcept
+      { return __sv_type(this->data(), this->size()).starts_with(__x); }
+
+      bool
+      ends_with(basic_string_view<_CharT, _Traits> __x) const noexcept
+      { return __sv_type(this->data(), this->size()).ends_with(__x); }
+
+      bool
+      ends_with(_CharT __x) const noexcept
+      { return __sv_type(this->data(), this->size()).ends_with(__x); }
+
+      bool
+      ends_with(const _CharT* __x) const noexcept
+      { return __sv_type(this->data(), this->size()).ends_with(__x); }
+#endif // C++20
+
       // Allow basic_stringbuf::__xfer_bufptrs to call _M_length:
       template<typename, typename, typename> friend class basic_stringbuf;
     };
@@ -5884,6 +5910,32 @@ _GLIBCXX_END_NAMESPACE_CXX11
       compare(size_type __pos, size_type __n1, const _CharT* __s,
 	      size_type __n2) const;
 
+#if __cplusplus > 201703L
+      bool
+      starts_with(basic_string_view<_CharT, _Traits> __x) const noexcept
+      { return __sv_type(this->data(), this->size()).starts_with(__x); }
+
+      bool
+      starts_with(_CharT __x) const noexcept
+      { return __sv_type(this->data(), this->size()).starts_with(__x); }
+
+      bool
+      starts_with(const _CharT* __x) const noexcept
+      { return __sv_type(this->data(), this->size()).starts_with(__x); }
+
+      bool
+      ends_with(basic_string_view<_CharT, _Traits> __x) const noexcept
+      { return __sv_type(this->data(), this->size()).ends_with(__x); }
+
+      bool
+      ends_with(_CharT __x) const noexcept
+      { return __sv_type(this->data(), this->size()).ends_with(__x); }
+
+      bool
+      ends_with(const _CharT* __x) const noexcept
+      { return __sv_type(this->data(), this->size()).ends_with(__x); }
+#endif // C++20
+
 # ifdef _GLIBCXX_TM_TS_INTERNAL
       friend void
       ::_txnal_cow_string_C1_for_exceptions(void* that, const char* s,
diff --git a/libstdc++-v3/include/std/string_view b/libstdc++-v3/include/std/string_view
index b4d9cf5..28d3fa4 100644
--- a/libstdc++-v3/include/std/string_view
+++ b/libstdc++-v3/include/std/string_view
@@ -227,7 +227,6 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 	__sv = __tmp;
       }
 
-
       // [string.view.ops], string operations:
 
       size_type
@@ -387,6 +386,38 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 				      traits_type::length(__str));
       }
 
+#if __cplusplus > 201703L
+      constexpr bool
+      starts_with(basic_string_view __x) const noexcept
+      {
+	return this->size() >= __x.size()
+	    && this->compare(0, __x.size(), __x) == 0;
+      }
+
+      constexpr bool
+      starts_with(_CharT __x) const noexcept
+      { return this->starts_with(basic_string_view(&__x, 1)); }
+
+      constexpr bool
+      starts_with(const _CharT* __x) const noexcept
+      { return this->starts_with(basic_string_view(__x)); }
+
+      constexpr bool
+      ends_with(basic_string_view __x) const noexcept
+      {
+	return this->size() >= __x.size()
+	    && this->compare(this->size() - __x.size(), npos, __x) == 0;
+      }
+
+      constexpr bool
+      ends_with(_CharT __x) const noexcept
+      { return this->ends_with(basic_string_view(&__x, 1)); }
+
+      constexpr bool
+      ends_with(const _CharT* __x) const noexcept
+      { return this->ends_with(basic_string_view(__x)); }
+#endif // C++20
+
       constexpr size_type
       _M_check(size_type __pos, const char* __s) const noexcept(false)
       {
diff --git a/libstdc++-v3/testsuite/21_strings/basic_string/operations/ends_with/char/1.cc b/libstdc++-v3/testsuite/21_strings/basic_string/operations/ends_with/char/1.cc
new file mode 100644
index 0000000..1b0bdae
--- /dev/null
+++ b/libstdc++-v3/testsuite/21_strings/basic_string/operations/ends_with/char/1.cc
@@ -0,0 +1,56 @@
+// { dg-options "-std=gnu++2a" }
+// { dg-do run { target c++2a } }
+
+// 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/>.
+
+// basic_string ends_with
+
+#include <string>
+#include <testsuite_hooks.h>
+
+void
+test01()
+{
+  const char cstr_suf[] = ".jpg";
+  const std::string_view sv_suf(".jpg");
+  const char cstr_suf2[] = ".rgb";
+  const std::string_view sv_suf2(".rgb");
+
+  const std::string s_test("slugs/slimy.jpg");
+
+  const auto cstr_in_slugs = s_test.ends_with(cstr_suf);
+  VERIFY( cstr_in_slugs );
+  const auto sv_in_slugs = s_test.ends_with(sv_suf);
+  VERIFY( sv_in_slugs );
+  const auto char_g = s_test.ends_with('g');
+  VERIFY( char_g );
+
+  const auto cstr_in_worms = s_test.ends_with(cstr_suf2);
+  VERIFY( !cstr_in_worms );
+  const auto sv_in_worms = s_test.ends_with(sv_suf2);
+  VERIFY( !sv_in_worms );
+  const auto char_b = s_test.ends_with('b');
+  VERIFY( !char_b );
+}
+
+int
+main()
+{ 
+  test01();
+  return 0;
+}
diff --git a/libstdc++-v3/testsuite/21_strings/basic_string/operations/ends_with/wchar_t/1.cc b/libstdc++-v3/testsuite/21_strings/basic_string/operations/ends_with/wchar_t/1.cc
new file mode 100644
index 0000000..0e95da3
--- /dev/null
+++ b/libstdc++-v3/testsuite/21_strings/basic_string/operations/ends_with/wchar_t/1.cc
@@ -0,0 +1,56 @@
+// { dg-options "-std=gnu++2a" }
+// { dg-do run { target c++2a } }
+
+// 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/>.
+
+// basic_string ends_with
+
+#include <string>
+#include <testsuite_hooks.h>
+
+void
+test01()
+{
+  const wchar_t cstr_suf[] = L".jpg";
+  const std::wstring_view sv_suf(L".jpg");
+  const wchar_t cstr_suf2[] = L".rgb";
+  const std::wstring_view sv_suf2(L".rgb");
+
+  const std::wstring s_test(L"slugs/slimy.jpg");
+
+  const auto cstr_in_slugs = s_test.ends_with(cstr_suf);
+  VERIFY( cstr_in_slugs );
+  const auto sv_in_slugs = s_test.ends_with(sv_suf);
+  VERIFY( sv_in_slugs );
+  const auto char_g = s_test.ends_with(L'g');
+  VERIFY( char_g );
+
+  const auto cstr_in_worms = s_test.ends_with(cstr_suf2);
+  VERIFY( !cstr_in_worms );
+  const auto sv_in_worms = s_test.ends_with(sv_suf2);
+  VERIFY( !sv_in_worms );
+  const auto char_b = s_test.ends_with(L'b');
+  VERIFY( !char_b );
+}
+
+int
+main()
+{ 
+  test01();
+  return 0;
+}
diff --git a/libstdc++-v3/testsuite/21_strings/basic_string/operations/starts_with/char/1.cc b/libstdc++-v3/testsuite/21_strings/basic_string/operations/starts_with/char/1.cc
new file mode 100644
index 0000000..233bf94
--- /dev/null
+++ b/libstdc++-v3/testsuite/21_strings/basic_string/operations/starts_with/char/1.cc
@@ -0,0 +1,56 @@
+// { dg-options "-std=gnu++2a" }
+// { dg-do run { target c++2a } }
+
+// 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/>.
+
+// basic_string begins_with
+
+#include <string>
+#include <testsuite_hooks.h>
+
+void
+test01()
+{
+  const char cstr_dir[] = "slugs/";
+  const std::string_view sv_dir("slugs/");
+  const char cstr_dir2[] = "worms/";
+  const std::string_view sv_dir2("worms/");
+
+  const std::string s_test("slugs/slimy.jpg");
+
+  const auto cstr_in_slugs = s_test.starts_with(cstr_dir);
+  VERIFY( cstr_in_slugs );
+  const auto sv_in_slugs = s_test.starts_with(sv_dir);
+  VERIFY( sv_in_slugs );
+  const auto char_s = s_test.starts_with('s');
+  VERIFY( char_s );
+
+  const auto cstr_in_worms = s_test.starts_with(cstr_dir2);
+  VERIFY( !cstr_in_worms );
+  const auto sv_in_worms = s_test.starts_with(sv_dir2);
+  VERIFY( !sv_in_worms );
+  const auto char_w = s_test.starts_with('w');
+  VERIFY( !char_w );
+}
+
+int
+main()
+{ 
+  test01();
+  return 0;
+}
diff --git a/libstdc++-v3/testsuite/21_strings/basic_string/operations/starts_with/wchar_t/1.cc b/libstdc++-v3/testsuite/21_strings/basic_string/operations/starts_with/wchar_t/1.cc
new file mode 100644
index 0000000..92f269a
--- /dev/null
+++ b/libstdc++-v3/testsuite/21_strings/basic_string/operations/starts_with/wchar_t/1.cc
@@ -0,0 +1,56 @@
+// { dg-options "-std=gnu++2a" }
+// { dg-do run { target c++2a } }
+
+// 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/>.
+
+// basic_string begins_with
+
+#include <string>
+#include <testsuite_hooks.h>
+
+void
+test01()
+{
+  const wchar_t cstr_dir[] = L"slugs/";
+  const std::wstring_view sv_dir(L"slugs/");
+  const wchar_t cstr_dir2[] = L"worms/";
+  const std::wstring_view sv_dir2(L"worms/");
+
+  const std::wstring s_test(L"slugs/slimy.jpg");
+
+  const auto cstr_in_slugs = s_test.starts_with(cstr_dir);
+  VERIFY( cstr_in_slugs );
+  const auto sv_in_slugs = s_test.starts_with(sv_dir);
+  VERIFY( sv_in_slugs );
+  const auto char_s = s_test.starts_with(L's');
+  VERIFY( char_s );
+
+  const auto cstr_in_worms = s_test.starts_with(cstr_dir2);
+  VERIFY( !cstr_in_worms );
+  const auto sv_in_worms = s_test.starts_with(sv_dir2);
+  VERIFY( !sv_in_worms );
+  const auto char_w = s_test.starts_with(L'w');
+  VERIFY( !char_w );
+}
+
+int
+main()
+{ 
+  test01();
+  return 0;
+}
diff --git a/libstdc++-v3/testsuite/21_strings/basic_string_view/operations/ends_with/char/1.cc b/libstdc++-v3/testsuite/21_strings/basic_string_view/operations/ends_with/char/1.cc
new file mode 100644
index 0000000..90d5d6c
--- /dev/null
+++ b/libstdc++-v3/testsuite/21_strings/basic_string_view/operations/ends_with/char/1.cc
@@ -0,0 +1,48 @@
+// { dg-options "-std=gnu++2a" }
+// { dg-do compile { target c++2a } }
+
+// 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/>.
+
+// basic_string_view ends_with
+
+#include <string_view>
+
+void
+test01()
+{
+  constexpr char cstr_suf[] = ".jpg";
+  constexpr std::string_view sv_suf(".jpg");
+  constexpr char cstr_suf2[] = ".rgb";
+  constexpr std::string_view sv_suf2(".rgb");
+
+  constexpr std::string_view sv_test("slugs/slimy.jpg");
+
+  constexpr auto cstr_in_slugs = sv_test.ends_with(cstr_suf);
+  static_assert(cstr_in_slugs);
+  constexpr auto sv_in_slugs = sv_test.ends_with(sv_suf);
+  static_assert(sv_in_slugs);
+  constexpr auto char_g = sv_test.ends_with('g');
+  static_assert(char_g);
+
+  constexpr auto cstr_in_worms = sv_test.ends_with(cstr_suf2);
+  static_assert(!cstr_in_worms);
+  constexpr auto sv_in_worms = sv_test.ends_with(sv_suf2);
+  static_assert(!sv_in_worms);
+  constexpr auto char_b = sv_test.ends_with('b');
+  static_assert(!char_b);
+}
diff --git a/libstdc++-v3/testsuite/21_strings/basic_string_view/operations/ends_with/wchar_t/1.cc b/libstdc++-v3/testsuite/21_strings/basic_string_view/operations/ends_with/wchar_t/1.cc
new file mode 100644
index 0000000..c23ac60
--- /dev/null
+++ b/libstdc++-v3/testsuite/21_strings/basic_string_view/operations/ends_with/wchar_t/1.cc
@@ -0,0 +1,48 @@
+// { dg-options "-std=gnu++2a" }
+// { dg-do compile { target c++2a } }
+
+// 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/>.
+
+// basic_string_view ends_with
+
+#include <string_view>
+
+void
+test01()
+{
+  constexpr wchar_t cstr_suf[] = L".jpg";
+  constexpr std::wstring_view sv_suf(L".jpg");
+  constexpr wchar_t cstr_suf2[] = L".rgb";
+  constexpr std::wstring_view sv_suf2(L".rgb");
+
+  constexpr std::wstring_view sv_test(L"slugs/slimy.jpg");
+
+  constexpr auto cstr_in_slugs = sv_test.ends_with(cstr_suf);
+  static_assert(cstr_in_slugs);
+  constexpr auto sv_in_slugs = sv_test.ends_with(sv_suf);
+  static_assert(sv_in_slugs);
+  constexpr auto char_g = sv_test.ends_with(L'g');
+  static_assert(char_g);
+
+  constexpr auto cstr_in_worms = sv_test.ends_with(cstr_suf2);
+  static_assert(!cstr_in_worms);
+  constexpr auto sv_in_worms = sv_test.ends_with(sv_suf2);
+  static_assert(!sv_in_worms);
+  constexpr auto char_b = sv_test.ends_with(L'b');
+  static_assert(!char_b);
+}
diff --git a/libstdc++-v3/testsuite/21_strings/basic_string_view/operations/starts_with/char/1.cc b/libstdc++-v3/testsuite/21_strings/basic_string_view/operations/starts_with/char/1.cc
new file mode 100644
index 0000000..3d77276
--- /dev/null
+++ b/libstdc++-v3/testsuite/21_strings/basic_string_view/operations/starts_with/char/1.cc
@@ -0,0 +1,48 @@
+// { dg-options "-std=gnu++2a" }
+// { dg-do compile { target c++2a } }
+
+// 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/>.
+
+// basic_string_view begins_with
+
+#include <string_view>
+
+void
+test01()
+{
+  constexpr char cstr_dir[] = "slugs/";
+  constexpr std::string_view sv_dir("slugs/");
+  constexpr char cstr_dir2[] = "worms/";
+  constexpr std::string_view sv_dir2("worms/");
+
+  constexpr std::string_view sv_test("slugs/slimy.jpg");
+
+  constexpr auto cstr_in_slugs = sv_test.starts_with(cstr_dir);
+  static_assert(cstr_in_slugs);
+  constexpr auto sv_in_slugs = sv_test.starts_with(sv_dir);
+  static_assert(sv_in_slugs);
+  constexpr auto char_s = sv_test.starts_with('s');
+  static_assert(char_s);
+
+  constexpr auto cstr_in_worms = sv_test.starts_with(cstr_dir2);
+  static_assert(!cstr_in_worms);
+  constexpr auto sv_in_worms = sv_test.starts_with(sv_dir2);
+  static_assert(!sv_in_worms);
+  constexpr auto char_w = sv_test.starts_with('w');
+  static_assert(!char_w);
+}
diff --git a/libstdc++-v3/testsuite/21_strings/basic_string_view/operations/starts_with/wchar_t/1.cc b/libstdc++-v3/testsuite/21_strings/basic_string_view/operations/starts_with/wchar_t/1.cc
new file mode 100644
index 0000000..854efb8
--- /dev/null
+++ b/libstdc++-v3/testsuite/21_strings/basic_string_view/operations/starts_with/wchar_t/1.cc
@@ -0,0 +1,48 @@
+// { dg-options "-std=gnu++2a" }
+// { dg-do compile { target c++2a } }
+
+// 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/>.
+
+// basic_string_view begins_with
+
+#include <string_view>
+
+void
+test01()
+{
+  constexpr wchar_t cstr_dir[] = L"slugs/";
+  constexpr std::wstring_view sv_dir(L"slugs/");
+  constexpr wchar_t cstr_dir2[] = L"worms/";
+  constexpr std::wstring_view sv_dir2(L"worms/");
+
+  constexpr std::wstring_view sv_test(L"slugs/slimy.jpg");
+
+  constexpr auto cstr_in_slugs = sv_test.starts_with(cstr_dir);
+  static_assert(cstr_in_slugs);
+  constexpr auto sv_in_slugs = sv_test.starts_with(sv_dir);
+  static_assert(sv_in_slugs);
+  constexpr auto char_s = sv_test.starts_with(L's');
+  static_assert(char_s);
+
+  constexpr auto cstr_in_worms = sv_test.starts_with(cstr_dir2);
+  static_assert(!cstr_in_worms);
+  constexpr auto sv_in_worms = sv_test.starts_with(sv_dir2);
+  static_assert(!sv_in_worms);
+  constexpr auto char_w = sv_test.starts_with(L'w');
+  static_assert(!char_w);
+}