Implement P0457R2: 'String Prefix and Suffix Checking' for c++2a

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@319687 91177308-0d34-0410-b5e6-96231b3b80d8

16 files changed, 928 insertions, 1 deletions

diff --git a/include/string b/include/string
index e7142b2b2..f5d548965 100644
--- a/include/string
+++ b/include/string
@@ -301,6 +301,13 @@ public:
     int compare(size_type pos1, size_type n1, const value_type* s) const;
     int compare(size_type pos1, size_type n1, const value_type* s, size_type n2) const;
 
+    bool starts_with(basic_string_view<charT, traits> sv) const noexcept; // C++2a
+    bool starts_with(charT c) const noexcept;                             // C++2a
+    bool starts_with(const charT* s) const;                               // C++2a
+    bool ends_with(basic_string_view<charT, traits> sv) const noexcept;   // C++2a
+    bool ends_with(charT c) const noexcept;                               // C++2a
+    bool ends_with(const charT* s) const;                                 // C++2a
+
     bool __invariants() const;
 };
 
@@ -1215,6 +1222,32 @@ public:
     int compare(size_type __pos1, size_type __n1, const value_type* __s) const;
     int compare(size_type __pos1, size_type __n1, const value_type* __s, size_type __n2) const;
 
+#if _LIBCPP_STD_VER > 17
+    _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
+    bool starts_with(__self_view __sv) const _NOEXCEPT
+    { return __self_view(data(), size()).starts_with(__sv); }
+
+    _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
+    bool starts_with(value_type __c) const _NOEXCEPT
+    { return !empty() && _Traits::eq(front(), __c); }
+
+    _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
+    bool starts_with(const value_type* __s) const _NOEXCEPT
+    { return starts_with(__self_view(__s)); }
+
+    _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
+    bool ends_with(__self_view __sv) const _NOEXCEPT
+    { return __self_view(data(), size()).ends_with( __sv); }
+
+    _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
+    bool ends_with(value_type __c) const _NOEXCEPT
+    { return !empty() && _Traits::eq(back(), __c); }
+
+    _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
+    bool ends_with(const value_type* __s) const _NOEXCEPT
+    { return ends_with(__self_view(__s)); }
+#endif
+
     _LIBCPP_INLINE_VISIBILITY bool __invariants() const;
 
     _LIBCPP_INLINE_VISIBILITY
diff --git a/include/string_view b/include/string_view
index 4d8e1a931..4d8358288 100644
--- a/include/string_view
+++ b/include/string_view
@@ -143,6 +143,13 @@ namespace std {
       constexpr size_type find_last_not_of(const charT* s, size_type pos, size_type n) const;
       constexpr size_type find_last_not_of(const charT* s, size_type pos = npos) const;
 
+      constexpr bool starts_with(basic_string_view s) const noexcept; // C++2a
+      constexpr bool starts_with(charT c) const noexcept;             // C++2a
+      constexpr bool starts_with(const charT* s) const;               // C++2a
+      constexpr bool ends_with(basic_string_view s) const noexcept;   // C++2a
+      constexpr bool ends_with(charT c) const noexcept;               // C++2a
+      constexpr bool ends_with(const charT* s) const;                 // C++2a
+
      private:
       const_pointer data_;  // exposition only
       size_type     size_;  // exposition only
@@ -565,6 +572,32 @@ public:
             (data(), size(), __s, __pos, traits_type::length(__s));
     }
 
+#if _LIBCPP_STD_VER > 17
+    _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
+    bool starts_with(basic_string_view __s) const _NOEXCEPT
+    { return size() >= __s.size() && compare(0, __s.size(), __s) == 0; }
+
+    _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
+    bool starts_with(value_type __c) const _NOEXCEPT
+    { return !empty() && _Traits::eq(front(), __c); }
+
+    _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
+    bool starts_with(const value_type* __s) const _NOEXCEPT
+    { return starts_with(basic_string_view(__s)); }
+
+    _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
+    bool ends_with(basic_string_view __s) const _NOEXCEPT
+    { return size() >= __s.size() && compare(size() - __s.size(), npos, __s) == 0; }
+
+    _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
+    bool ends_with(value_type __c) const _NOEXCEPT
+    { return !empty() && _Traits::eq(back(), __c); }
+
+    _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
+    bool ends_with(const value_type* __s) const _NOEXCEPT
+    { return ends_with(basic_string_view(__s)); }
+#endif
+
 private:
     const   value_type* __data;
     size_type           __size;
diff --git a/test/std/strings/basic.string/string.ends_with/ends_with.char.pass.cpp b/test/std/strings/basic.string/string.ends_with/ends_with.char.pass.cpp
new file mode 100644
index 000000000..6091e0c06
--- /dev/null
+++ b/test/std/strings/basic.string/string.ends_with/ends_with.char.pass.cpp
@@ -0,0 +1,34 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++98, c++03, c++11, c++14, c++17
+
+// <string>
+
+//   bool ends_with(charT x) const noexcept;
+
+#include <string>
+#include <cassert>
+
+#include "test_macros.h"
+
+int main()
+{
+    {
+    typedef std::string S;
+    S  s1 {};
+    S  s2 { "abcde", 5 };
+
+    ASSERT_NOEXCEPT(s1.ends_with('e'));
+
+    assert (!s1.ends_with('e'));
+    assert (!s1.ends_with('x'));
+    assert ( s2.ends_with('e'));
+    assert (!s2.ends_with('x'));
+    }
+}
diff --git a/test/std/strings/basic.string/string.ends_with/ends_with.ptr.pass.cpp b/test/std/strings/basic.string/string.ends_with/ends_with.ptr.pass.cpp
new file mode 100644
index 000000000..fc28bcd30
--- /dev/null
+++ b/test/std/strings/basic.string/string.ends_with/ends_with.ptr.pass.cpp
@@ -0,0 +1,63 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++98, c++03, c++11, c++14, c++17
+
+// <string>
+
+//   bool ends_with(const CharT *x) const;
+
+#include <string>
+#include <cassert>
+
+#include "test_macros.h"
+
+int main()
+{
+    {
+    typedef std::string S;
+    const char *s = "abcde";
+
+    S   s0;
+    S   s1  { s + 4, 1 };
+    S   s2  { s + 3, 2 };
+//  S   s3  { s + 2, 3 };
+//  S   s4  { s + 1, 4 };
+//  S   s5  { s,     5 };
+    S  sNot { "def", 3 };
+    
+    LIBCPP_ASSERT_NOEXCEPT(s0.ends_with(""));
+
+    assert ( s0.ends_with(""));
+    assert (!s0.ends_with("e"));
+
+    assert ( s1.ends_with(""));
+    assert ( s1.ends_with("e"));
+    assert (!s1.ends_with("de"));
+    assert (!s1.ends_with("cde"));
+    assert (!s1.ends_with("bcde"));
+    assert (!s1.ends_with("abcde"));
+    assert (!s1.ends_with("def"));
+
+    assert ( s2.ends_with(""));
+    assert ( s2.ends_with("e"));
+    assert ( s2.ends_with("de"));
+    assert (!s2.ends_with("cde"));
+    assert (!s2.ends_with("bcde"));
+    assert (!s2.ends_with("abcde"));
+    assert (!s2.ends_with("def"));
+
+    assert ( sNot.ends_with(""));
+    assert (!sNot.ends_with("e"));
+    assert (!sNot.ends_with("de"));
+    assert (!sNot.ends_with("cde"));
+    assert (!sNot.ends_with("bcde"));
+    assert (!sNot.ends_with("abcde"));
+    assert ( sNot.ends_with("def"));
+    }
+}
diff --git a/test/std/strings/basic.string/string.ends_with/ends_with.string_view.pass.cpp b/test/std/strings/basic.string/string.ends_with/ends_with.string_view.pass.cpp
new file mode 100644
index 000000000..0708dffb4
--- /dev/null
+++ b/test/std/strings/basic.string/string.ends_with/ends_with.string_view.pass.cpp
@@ -0,0 +1,72 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++98, c++03, c++11, c++14, c++17
+
+// <string>
+
+//   bool ends_with(basic_string_view x) const noexcept;
+
+#include <string>
+#include <cassert>
+
+#include "test_macros.h"
+
+int main()
+{
+    {
+    typedef std::string S;
+    typedef std::string_view SV;
+    const char *s = "abcde";
+
+    S   s0;
+    S   s1  { s + 4, 1 };
+    S   s2  { s + 3, 2 };
+//  S   s3  { s + 2, 3 };
+//  S   s4  { s + 1, 4 };
+//  S   s5  { s,     5 };
+    S  sNot { "def", 3 };
+    
+    SV  sv0;
+    SV  sv1 { s + 4, 1 };
+    SV  sv2 { s + 3, 2 };
+    SV  sv3 { s + 2, 3 };
+    SV  sv4 { s + 1, 4 };
+    SV  sv5 { s    , 5 };
+    SV svNot {"def", 3 };
+
+    ASSERT_NOEXCEPT(s0.ends_with(sv0));
+
+    assert ( s0.ends_with(sv0));
+    assert (!s0.ends_with(sv1));
+
+    assert ( s1.ends_with(sv0));
+    assert ( s1.ends_with(sv1));
+    assert (!s1.ends_with(sv2));
+    assert (!s1.ends_with(sv3));
+    assert (!s1.ends_with(sv4));
+    assert (!s1.ends_with(sv5));
+    assert (!s1.ends_with(svNot));
+
+    assert ( s2.ends_with(sv0));
+    assert ( s2.ends_with(sv1));
+    assert ( s2.ends_with(sv2));
+    assert (!s2.ends_with(sv3));
+    assert (!s2.ends_with(sv4));
+    assert (!s2.ends_with(sv5));
+    assert (!s2.ends_with(svNot));
+
+    assert ( sNot.ends_with(sv0));
+    assert (!sNot.ends_with(sv1));
+    assert (!sNot.ends_with(sv2));
+    assert (!sNot.ends_with(sv3));
+    assert (!sNot.ends_with(sv4));
+    assert (!sNot.ends_with(sv5));
+    assert ( sNot.ends_with(svNot));
+    }
+}
diff --git a/test/std/strings/basic.string/string.modifiers/string_append/push_back.pass.cpp b/test/std/strings/basic.string/string.modifiers/string_append/push_back.pass.cpp
index f2fb8782a..de0a02392 100644
--- a/test/std/strings/basic.string/string.modifiers/string_append/push_back.pass.cpp
+++ b/test/std/strings/basic.string/string.modifiers/string_append/push_back.pass.cpp
@@ -17,6 +17,12 @@
 #include "test_macros.h"
 #include "min_allocator.h"
 
+struct veryLarge
+{
+  long long a;
+  char b;
+};
+
 template <class S>
 void
 test(S s, typename S::value_type c, S expected)
@@ -42,4 +48,12 @@ int main()
     test(S("12345678901234567890"), 'a', S("12345678901234567890a"));
     }
 #endif
+    {
+// https://bugs.llvm.org/show_bug.cgi?id=31454
+    std::basic_string<veryLarge> s;
+    veryLarge vl;
+    s.push_back(vl);
+    s.push_back(vl);
+    s.push_back(vl);
+    }
 }
diff --git a/test/std/strings/basic.string/string.starts_with/starts_with.char.pass.cpp b/test/std/strings/basic.string/string.starts_with/starts_with.char.pass.cpp
new file mode 100644
index 000000000..4be35a765
--- /dev/null
+++ b/test/std/strings/basic.string/string.starts_with/starts_with.char.pass.cpp
@@ -0,0 +1,34 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++98, c++03, c++11, c++14, c++17
+
+// <string>
+
+//   bool starts_with(charT x) const noexcept;
+
+#include <string>
+#include <cassert>
+
+#include "test_macros.h"
+
+int main()
+{
+    {
+    typedef std::string S;
+    S  s1 {};
+    S  s2 { "abcde", 5 };
+
+    ASSERT_NOEXCEPT(s1.starts_with('e'));
+
+    assert (!s1.starts_with('a'));
+    assert (!s1.starts_with('x'));
+    assert ( s2.starts_with('a'));
+    assert (!s2.starts_with('x'));
+    }
+}
diff --git a/test/std/strings/basic.string/string.starts_with/starts_with.ptr.pass.cpp b/test/std/strings/basic.string/string.starts_with/starts_with.ptr.pass.cpp
new file mode 100644
index 000000000..5dec2156e
--- /dev/null
+++ b/test/std/strings/basic.string/string.starts_with/starts_with.ptr.pass.cpp
@@ -0,0 +1,62 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++98, c++03, c++11, c++14, c++17
+
+// <string>
+
+//   bool starts_with(const CharT *x) const;
+
+#include <string>
+#include <cassert>
+
+#include "test_macros.h"
+
+int main()
+{
+    {
+    typedef std::string S;
+    const char *s = "abcde";
+    S  s0 {};
+    S  s1 { s, 1 };
+    S  s2 { s, 2 };
+//     S  s3 { s, 3 };
+//     S  s4 { s, 4 };
+//     S  s5 { s, 5 };
+    S  sNot {"def", 3 };
+
+    LIBCPP_ASSERT_NOEXCEPT(s0.starts_with(""));
+
+    assert ( s0.starts_with(""));
+    assert (!s0.starts_with("a"));
+
+    assert ( s1.starts_with(""));
+    assert ( s1.starts_with("a"));
+    assert (!s1.starts_with("ab"));
+    assert (!s1.starts_with("abc"));
+    assert (!s1.starts_with("abcd"));
+    assert (!s1.starts_with("abcde"));
+    assert (!s1.starts_with("def"));
+
+    assert ( s2.starts_with(""));
+    assert ( s2.starts_with("a"));
+    assert ( s2.starts_with("ab"));
+    assert (!s2.starts_with("abc"));
+    assert (!s2.starts_with("abcd"));
+    assert (!s2.starts_with("abcde"));
+    assert (!s2.starts_with("def"));
+
+    assert ( sNot.starts_with(""));
+    assert (!sNot.starts_with("a"));
+    assert (!sNot.starts_with("ab"));
+    assert (!sNot.starts_with("abc"));
+    assert (!sNot.starts_with("abcd"));
+    assert (!sNot.starts_with("abcde"));
+    assert ( sNot.starts_with("def"));
+    }
+}
diff --git a/test/std/strings/basic.string/string.starts_with/starts_with.string_view.pass.cpp b/test/std/strings/basic.string/string.starts_with/starts_with.string_view.pass.cpp
new file mode 100644
index 000000000..2dccd73df
--- /dev/null
+++ b/test/std/strings/basic.string/string.starts_with/starts_with.string_view.pass.cpp
@@ -0,0 +1,72 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++98, c++03, c++11, c++14, c++17
+
+// <string>
+
+//   bool starts_with(string_view x) const noexcept;
+
+#include <string>
+#include <cassert>
+
+#include "test_macros.h"
+
+int main()
+{
+    {
+    typedef std::string S;
+    typedef std::string_view SV;
+    const char *s = "abcde";
+
+    S   s0;
+    S   s1  { s, 1 };
+    S   s2  { s, 2 };
+//  S   s3  { s, 3 };
+//  S   s4  { s, 4 };
+//  S   s5  { s, 5 };
+    S  sNot { "def", 3 };
+    
+    SV  sv0;
+    SV  sv1 { s, 1 };
+    SV  sv2 { s, 2 };
+    SV  sv3 { s, 3 };
+    SV  sv4 { s, 4 };
+    SV  sv5 { s, 5 };
+    SV svNot {"def", 3 };
+
+    ASSERT_NOEXCEPT(s0.starts_with(sv0));
+
+    assert ( s0.starts_with(sv0));
+    assert (!s0.starts_with(sv1));
+
+    assert ( s1.starts_with(sv0));
+    assert ( s1.starts_with(sv1));
+    assert (!s1.starts_with(sv2));
+    assert (!s1.starts_with(sv3));
+    assert (!s1.starts_with(sv4));
+    assert (!s1.starts_with(sv5));
+    assert (!s1.starts_with(svNot));
+
+    assert ( s2.starts_with(sv0));
+    assert ( s2.starts_with(sv1));
+    assert ( s2.starts_with(sv2));
+    assert (!s2.starts_with(sv3));
+    assert (!s2.starts_with(sv4));
+    assert (!s2.starts_with(sv5));
+    assert (!s2.starts_with(svNot));
+
+    assert ( sNot.starts_with(sv0));
+    assert (!sNot.starts_with(sv1));
+    assert (!sNot.starts_with(sv2));
+    assert (!sNot.starts_with(sv3));
+    assert (!sNot.starts_with(sv4));
+    assert (!sNot.starts_with(sv5));
+    assert ( sNot.starts_with(svNot));
+    }
+}
diff --git a/test/std/strings/string.view/string.view.template/ends_with.char.pass.cpp b/test/std/strings/string.view/string.view.template/ends_with.char.pass.cpp
new file mode 100644
index 000000000..1511f014b
--- /dev/null
+++ b/test/std/strings/string.view/string.view.template/ends_with.char.pass.cpp
@@ -0,0 +1,47 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++98, c++03, c++11, c++14, c++17
+
+// <string_view>
+
+//   constexpr bool ends_with(charT x) const noexcept;
+
+#include <string_view>
+#include <cassert>
+
+#include "test_macros.h"
+#include "constexpr_char_traits.hpp"
+
+int main()
+{
+    {
+    typedef std::string_view SV;
+    SV  sv1 {};
+    SV  sv2 { "abcde", 5 };
+
+    ASSERT_NOEXCEPT(sv1.ends_with('e'));
+
+    assert (!sv1.ends_with('e'));
+    assert (!sv1.ends_with('x'));
+    assert ( sv2.ends_with('e'));
+    assert (!sv2.ends_with('x'));
+    }
+
+#if TEST_STD_VER > 11
+    {
+    typedef std::basic_string_view<char, constexpr_char_traits<char>> SV;
+    constexpr SV  sv1 {};
+    constexpr SV  sv2 { "abcde", 5 };
+    static_assert (!sv1.ends_with('e'), "" );
+    static_assert (!sv1.ends_with('x'), "" );
+    static_assert ( sv2.ends_with('e'), "" );
+    static_assert (!sv2.ends_with('x'), "" );
+    }
+#endif
+}
diff --git a/test/std/strings/string.view/string.view.template/ends_with.ptr.pass.cpp b/test/std/strings/string.view/string.view.template/ends_with.ptr.pass.cpp
new file mode 100644
index 000000000..544cddd84
--- /dev/null
+++ b/test/std/strings/string.view/string.view.template/ends_with.ptr.pass.cpp
@@ -0,0 +1,104 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++98, c++03, c++11, c++14, c++17
+
+// <string_view>
+
+//   constexpr bool starts_with(const CharT *x) const;
+
+#include <string_view>
+#include <cassert>
+
+#include "test_macros.h"
+#include "constexpr_char_traits.hpp"
+
+int main()
+{
+    {
+    typedef std::string_view SV;
+    const char *s = "abcde";
+    SV  sv0 {};
+    SV  sv1 { s + 4, 1 };
+    SV  sv2 { s + 3, 2 };
+//     SV  sv3 { s + 2, 3 };
+//     SV  sv4 { s + 1, 4 };
+//     SV  sv5 { s    , 5 };
+    SV  svNot {"def", 3 };
+
+    LIBCPP_ASSERT_NOEXCEPT(sv0.ends_with(""));
+
+    assert ( sv0.ends_with(""));
+    assert (!sv0.ends_with("e"));
+
+    assert ( sv1.ends_with(""));
+    assert ( sv1.ends_with("e"));
+    assert (!sv1.ends_with("de"));
+    assert (!sv1.ends_with("cde"));
+    assert (!sv1.ends_with("bcde"));
+    assert (!sv1.ends_with("abcde"));
+    assert (!sv1.ends_with("def"));
+
+    assert ( sv2.ends_with(""));
+    assert ( sv2.ends_with("e"));
+    assert ( sv2.ends_with("de"));
+    assert (!sv2.ends_with("cde"));
+    assert (!sv2.ends_with("bcde"));
+    assert (!sv2.ends_with("abcde"));
+    assert (!sv2.ends_with("def"));
+
+    assert ( svNot.ends_with(""));
+    assert (!svNot.ends_with("e"));
+    assert (!svNot.ends_with("de"));
+    assert (!svNot.ends_with("cde"));
+    assert (!svNot.ends_with("bcde"));
+    assert (!svNot.ends_with("abcde"));
+    assert ( svNot.ends_with("def"));
+    }
+
+#if TEST_STD_VER > 11
+    {
+    typedef std::basic_string_view<char, constexpr_char_traits<char>> SV;
+    constexpr const char *s = "abcde";
+    constexpr SV  sv0 {};
+    constexpr SV  sv1 { s + 4, 1 };
+    constexpr SV  sv2 { s + 3, 2 };
+//     constexpr SV  sv3 { s + 2, 3 };
+//     constexpr SV  sv4 { s + 1, 4 };
+//     constexpr SV  sv5 { s,     5 };
+    constexpr SV  svNot {"def", 3 };
+
+    static_assert ( sv0.ends_with(""), "" );
+    static_assert (!sv0.ends_with("e"), "" );
+
+    static_assert ( sv1.ends_with(""), "" );
+    static_assert ( sv1.ends_with("e"), "" );
+    static_assert (!sv1.ends_with("de"), "" );
+    static_assert (!sv1.ends_with("cde"), "" );
+    static_assert (!sv1.ends_with("bcde"), "" );
+    static_assert (!sv1.ends_with("abcde"), "" );
+    static_assert (!sv1.ends_with("def"), "" );
+
+    static_assert ( sv2.ends_with(""), "" );
+    static_assert ( sv2.ends_with("e"), "" );
+    static_assert ( sv2.ends_with("de"), "" );
+    static_assert (!sv2.ends_with("cde"), "" );
+    static_assert (!sv2.ends_with("bcde"), "" );
+    static_assert (!sv2.ends_with("abcde"), "" );
+    static_assert (!sv2.ends_with("def"), "" );
+
+    static_assert ( svNot.ends_with(""), "" );
+    static_assert (!svNot.ends_with("e"), "" );
+    static_assert (!svNot.ends_with("de"), "" );
+    static_assert (!svNot.ends_with("cde"), "" );
+    static_assert (!svNot.ends_with("bcde"), "" );
+    static_assert (!svNot.ends_with("abcde"), "" );
+    static_assert ( svNot.ends_with("def"), "" );
+    }
+#endif
+}
diff --git a/test/std/strings/string.view/string.view.template/ends_with.string_view.pass.cpp b/test/std/strings/string.view/string.view.template/ends_with.string_view.pass.cpp
new file mode 100644
index 000000000..61ea807ba
--- /dev/null
+++ b/test/std/strings/string.view/string.view.template/ends_with.string_view.pass.cpp
@@ -0,0 +1,104 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++98, c++03, c++11, c++14, c++17
+
+// <string_view>
+
+//   constexpr bool ends_with(string_view x) const noexcept;
+
+#include <string_view>
+#include <cassert>
+
+#include "test_macros.h"
+#include "constexpr_char_traits.hpp"
+
+int main()
+{
+    {
+    typedef std::string_view SV;
+    const char *s = "abcde";
+    SV  sv0;
+    SV  sv1 { s + 4, 1 };
+    SV  sv2 { s + 3, 2 };
+    SV  sv3 { s + 2, 3 };
+    SV  sv4 { s + 1, 4 };
+    SV  sv5 { s    , 5 };
+    SV  svNot {"def", 3 };
+
+    ASSERT_NOEXCEPT(sv0.ends_with(sv0));
+
+    assert ( sv0.ends_with(sv0));
+    assert (!sv0.ends_with(sv1));
+
+    assert ( sv1.ends_with(sv0));
+    assert ( sv1.ends_with(sv1));
+    assert (!sv1.ends_with(sv2));
+    assert (!sv1.ends_with(sv3));
+    assert (!sv1.ends_with(sv4));
+    assert (!sv1.ends_with(sv5));
+    assert (!sv1.ends_with(svNot));
+
+    assert ( sv2.ends_with(sv0));
+    assert ( sv2.ends_with(sv1));
+    assert ( sv2.ends_with(sv2));
+    assert (!sv2.ends_with(sv3));
+    assert (!sv2.ends_with(sv4));
+    assert (!sv2.ends_with(sv5));
+    assert (!sv2.ends_with(svNot));
+
+    assert ( svNot.ends_with(sv0));
+    assert (!svNot.ends_with(sv1));
+    assert (!svNot.ends_with(sv2));
+    assert (!svNot.ends_with(sv3));
+    assert (!svNot.ends_with(sv4));
+    assert (!svNot.ends_with(sv5));
+    assert ( svNot.ends_with(svNot));
+    }
+
+#if TEST_STD_VER > 11
+    {
+    typedef std::basic_string_view<char, constexpr_char_traits<char>> SV;
+    constexpr const char *s = "abcde";
+    constexpr SV  sv0 {};
+    constexpr SV  sv1 { s + 4, 1 };
+    constexpr SV  sv2 { s + 3, 2 };
+    constexpr SV  sv3 { s + 2, 3 };
+    constexpr SV  sv4 { s + 1, 4 };
+    constexpr SV  sv5 { s,     5 };
+    constexpr SV  svNot {"def", 3 };
+
+    static_assert ( sv0.ends_with(sv0), "" );
+    static_assert (!sv0.ends_with(sv1), "" );
+
+    static_assert ( sv1.ends_with(sv0), "" );
+    static_assert ( sv1.ends_with(sv1), "" );
+    static_assert (!sv1.ends_with(sv2), "" );
+    static_assert (!sv1.ends_with(sv3), "" );
+    static_assert (!sv1.ends_with(sv4), "" );
+    static_assert (!sv1.ends_with(sv5), "" );
+    static_assert (!sv1.ends_with(svNot), "" );
+
+    static_assert ( sv2.ends_with(sv0), "" );
+    static_assert ( sv2.ends_with(sv1), "" );
+    static_assert ( sv2.ends_with(sv2), "" );
+    static_assert (!sv2.ends_with(sv3), "" );
+    static_assert (!sv2.ends_with(sv4), "" );
+    static_assert (!sv2.ends_with(sv5), "" );
+    static_assert (!sv2.ends_with(svNot), "" );
+
+    static_assert ( svNot.ends_with(sv0), "" );
+    static_assert (!svNot.ends_with(sv1), "" );
+    static_assert (!svNot.ends_with(sv2), "" );
+    static_assert (!svNot.ends_with(sv3), "" );
+    static_assert (!svNot.ends_with(sv4), "" );
+    static_assert (!svNot.ends_with(sv5), "" );
+    static_assert ( svNot.ends_with(svNot), "" );
+    }
+#endif
+}
diff --git a/test/std/strings/string.view/string.view.template/starts_with.char.pass.cpp b/test/std/strings/string.view/string.view.template/starts_with.char.pass.cpp
new file mode 100644
index 000000000..042aea601
--- /dev/null
+++ b/test/std/strings/string.view/string.view.template/starts_with.char.pass.cpp
@@ -0,0 +1,47 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++98, c++03, c++11, c++14, c++17
+
+// <string_view>
+
+//   constexpr bool starts_with(charT x) const noexcept;
+
+#include <string_view>
+#include <cassert>
+
+#include "test_macros.h"
+#include "constexpr_char_traits.hpp"
+
+int main()
+{
+    {
+    typedef std::string_view SV;
+    SV  sv1 {};
+    SV  sv2 { "abcde", 5 };
+
+    ASSERT_NOEXCEPT(sv1.starts_with('e'));
+
+    assert (!sv1.starts_with('a'));
+    assert (!sv1.starts_with('x'));
+    assert ( sv2.starts_with('a'));
+    assert (!sv2.starts_with('x'));
+    }
+
+#if TEST_STD_VER > 11
+    {
+    typedef std::basic_string_view<char, constexpr_char_traits<char>> SV;
+    constexpr SV  sv1 {};
+    constexpr SV  sv2 { "abcde", 5 };
+    static_assert (!sv1.starts_with('a'), "" );
+    static_assert (!sv1.starts_with('x'), "" );
+    static_assert ( sv2.starts_with('a'), "" );
+    static_assert (!sv2.starts_with('x'), "" );
+    }
+#endif
+}
diff --git a/test/std/strings/string.view/string.view.template/starts_with.ptr.pass.cpp b/test/std/strings/string.view/string.view.template/starts_with.ptr.pass.cpp
new file mode 100644
index 000000000..baaa4c973
--- /dev/null
+++ b/test/std/strings/string.view/string.view.template/starts_with.ptr.pass.cpp
@@ -0,0 +1,104 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++98, c++03, c++11, c++14, c++17
+
+// <string_view>
+
+//   constexpr bool starts_with(string_view x) const noexcept;
+
+#include <string_view>
+#include <cassert>
+
+#include "test_macros.h"
+#include "constexpr_char_traits.hpp"
+
+int main()
+{
+    {
+    typedef std::string_view SV;
+    const char *s = "abcde";
+    SV  sv0 {};
+    SV  sv1 { s, 1 };
+    SV  sv2 { s, 2 };
+//     SV  sv3 { s, 3 };
+//     SV  sv4 { s, 4 };
+//     SV  sv5 { s, 5 };
+    SV  svNot {"def", 3 };
+
+    LIBCPP_ASSERT_NOEXCEPT(sv0.starts_with(""));
+
+    assert ( sv0.starts_with(""));
+    assert (!sv0.starts_with("a"));
+
+    assert ( sv1.starts_with(""));
+    assert ( sv1.starts_with("a"));
+    assert (!sv1.starts_with("ab"));
+    assert (!sv1.starts_with("abc"));
+    assert (!sv1.starts_with("abcd"));
+    assert (!sv1.starts_with("abcde"));
+    assert (!sv1.starts_with("def"));
+
+    assert ( sv2.starts_with(s + 5));
+    assert ( sv2.starts_with("a"));
+    assert ( sv2.starts_with("ab"));
+    assert (!sv2.starts_with("abc"));
+    assert (!sv2.starts_with("abcd"));
+    assert (!sv2.starts_with("abcde"));
+    assert (!sv2.starts_with("def"));
+
+    assert ( svNot.starts_with(""));
+    assert (!svNot.starts_with("a"));
+    assert (!svNot.starts_with("ab"));
+    assert (!svNot.starts_with("abc"));
+    assert (!svNot.starts_with("abcd"));
+    assert (!svNot.starts_with("abcde"));
+    assert ( svNot.starts_with("def"));
+    }
+
+#if TEST_STD_VER > 11
+    {
+    typedef std::basic_string_view<char, constexpr_char_traits<char>> SV;
+    constexpr const char *s = "abcde";
+    constexpr SV  sv0 {};
+    constexpr SV  sv1 { s, 1 };
+    constexpr SV  sv2 { s, 2 };
+//     constexpr SV  sv3 { s, 3 };
+//     constexpr SV  sv4 { s, 4 };
+//     constexpr SV  sv5 { s, 5 };
+    constexpr SV  svNot {"def", 3 };
+
+    static_assert ( sv0.starts_with(""), "" );
+    static_assert (!sv0.starts_with("a"), "" );
+
+    static_assert ( sv1.starts_with(""), "" );
+    static_assert ( sv1.starts_with("a"), "" );
+    static_assert (!sv1.starts_with("ab"), "" );
+    static_assert (!sv1.starts_with("abc"), "" );
+    static_assert (!sv1.starts_with("abcd"), "" );
+    static_assert (!sv1.starts_with("abcde"), "" );
+    static_assert (!sv1.starts_with("def"), "" );
+
+    static_assert ( sv2.starts_with(s + 5), "" );
+    static_assert ( sv2.starts_with("a"), "" );
+    static_assert ( sv2.starts_with("ab"), "" );
+    static_assert (!sv2.starts_with("abc"), "" );
+    static_assert (!sv2.starts_with("abcd"), "" );
+    static_assert (!sv2.starts_with("abcde"), "" );
+    static_assert (!sv2.starts_with("def"), "" );
+
+    static_assert ( svNot.starts_with(""), "" );
+    static_assert (!svNot.starts_with("a"), "" );
+    static_assert (!svNot.starts_with("ab"), "" );
+    static_assert (!svNot.starts_with("abc"), "" );
+    static_assert (!svNot.starts_with("abcd"), "" );
+    static_assert (!svNot.starts_with("abcde"), "" );
+    static_assert ( svNot.starts_with("def"), "" );
+    }
+#endif
+}
diff --git a/test/std/strings/string.view/string.view.template/starts_with.string_view.pass.cpp b/test/std/strings/string.view/string.view.template/starts_with.string_view.pass.cpp
new file mode 100644
index 000000000..7501926af
--- /dev/null
+++ b/test/std/strings/string.view/string.view.template/starts_with.string_view.pass.cpp
@@ -0,0 +1,104 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++98, c++03, c++11, c++14, c++17
+
+// <string_view>
+
+//   constexpr bool starts_with(string_view x) const noexcept;
+
+#include <string_view>
+#include <cassert>
+
+#include "test_macros.h"
+#include "constexpr_char_traits.hpp"
+
+int main()
+{
+    {
+    typedef std::string_view SV;
+    const char *s = "abcde";
+    SV  sv0 {};
+    SV  sv1 { s, 1 };
+    SV  sv2 { s, 2 };
+    SV  sv3 { s, 3 };
+    SV  sv4 { s, 4 };
+    SV  sv5 { s, 5 };
+    SV  svNot {"def", 3 };
+
+    ASSERT_NOEXCEPT(sv0.starts_with(sv0));
+
+    assert ( sv0.starts_with(sv0));
+    assert (!sv0.starts_with(sv1));
+
+    assert ( sv1.starts_with(sv0));
+    assert ( sv1.starts_with(sv1));
+    assert (!sv1.starts_with(sv2));
+    assert (!sv1.starts_with(sv3));
+    assert (!sv1.starts_with(sv4));
+    assert (!sv1.starts_with(sv5));
+    assert (!sv1.starts_with(svNot));
+
+    assert ( sv2.starts_with(sv0));
+    assert ( sv2.starts_with(sv1));
+    assert ( sv2.starts_with(sv2));
+    assert (!sv2.starts_with(sv3));
+    assert (!sv2.starts_with(sv4));
+    assert (!sv2.starts_with(sv5));
+    assert (!sv2.starts_with(svNot));
+
+    assert ( svNot.starts_with(sv0));
+    assert (!svNot.starts_with(sv1));
+    assert (!svNot.starts_with(sv2));
+    assert (!svNot.starts_with(sv3));
+    assert (!svNot.starts_with(sv4));
+    assert (!svNot.starts_with(sv5));
+    assert ( svNot.starts_with(svNot));
+    }
+
+#if TEST_STD_VER > 11
+    {
+    typedef std::basic_string_view<char, constexpr_char_traits<char>> SV;
+    constexpr const char *s = "abcde";
+    constexpr SV  sv0 {};
+    constexpr SV  sv1 { s, 1 };
+    constexpr SV  sv2 { s, 2 };
+    constexpr SV  sv3 { s, 3 };
+    constexpr SV  sv4 { s, 4 };
+    constexpr SV  sv5 { s, 5 };
+    constexpr SV  svNot {"def", 3 };
+
+    static_assert ( sv0.starts_with(sv0), "" );
+    static_assert (!sv0.starts_with(sv1), "" );
+
+    static_assert ( sv1.starts_with(sv0), "" );
+    static_assert ( sv1.starts_with(sv1), "" );
+    static_assert (!sv1.starts_with(sv2), "" );
+    static_assert (!sv1.starts_with(sv3), "" );
+    static_assert (!sv1.starts_with(sv4), "" );
+    static_assert (!sv1.starts_with(sv5), "" );
+    static_assert (!sv1.starts_with(svNot), "" );
+
+    static_assert ( sv2.starts_with(sv0), "" );
+    static_assert ( sv2.starts_with(sv1), "" );
+    static_assert ( sv2.starts_with(sv2), "" );
+    static_assert (!sv2.starts_with(sv3), "" );
+    static_assert (!sv2.starts_with(sv4), "" );
+    static_assert (!sv2.starts_with(sv5), "" );
+    static_assert (!sv2.starts_with(svNot), "" );
+
+    static_assert ( svNot.starts_with(sv0), "" );
+    static_assert (!svNot.starts_with(sv1), "" );
+    static_assert (!svNot.starts_with(sv2), "" );
+    static_assert (!svNot.starts_with(sv3), "" );
+    static_assert (!svNot.starts_with(sv4), "" );
+    static_assert (!svNot.starts_with(sv5), "" );
+    static_assert ( svNot.starts_with(svNot), "" );
+    }
+#endif
+}
diff --git a/www/cxx2a_status.html b/www/cxx2a_status.html
index 92ed9a5d9..9e45c3de1 100644
--- a/www/cxx2a_status.html
+++ b/www/cxx2a_status.html
@@ -63,7 +63,7 @@
 	<tr><td><a href="https://wg21.link/P0202R3">P0202R3</a></td><td>LWG</td><td>Add constexpr modifiers to functions in &lt;algorithm&gt; and &lt;utility&gt; Headers</td><td>Albuquerque</td><td></td><td></td></tr>
 	<tr><td><a href="https://wg21.link/P0415R1">P0415R1</a></td><td>LWG</td><td>Constexpr for <tt>std::complex</tt></td><td>Albuquerque</td><td></td><td></td></tr>
 	<tr><td><a href="https://wg21.link/P0439R0">P0439R0</a></td><td>LWG</td><td>Make <tt>std::memory_order</tt> a scoped enumeration</td><td>Albuquerque</td><td></td><td></td></tr>
-	<tr><td><a href="https://wg21.link/P0457R2">P0457R2</a></td><td>LWG</td><td>String Prefix and Suffix Checking</td><td>Albuquerque</td><td></td><td></td></tr>
+	<tr><td><a href="https://wg21.link/P0457R2">P0457R2</a></td><td>LWG</td><td>String Prefix and Suffix Checking</td><td>Albuquerque</td><td>Complete</td><td>6.0</td></tr>
 	<tr><td><a href="https://wg21.link/P0550R2">P0550R2</a></td><td>LWG</td><td>Transformation Trait <tt>remove_cvref</tt></td><td>Albuquerque</td><td>Complete</td><td>6.0</td></tr>
 	<tr><td><a href="https://wg21.link/P0600R1">P0600R1</a></td><td>LWG</td><td>nodiscard in the Library</td><td>Albuquerque</td><td><I>In Progress</I></td><td></td></tr>
 	<tr><td><a href="https://wg21.link/P0616R0">P0616R0</a></td><td>LWG</td><td>de-pessimize legacy <numeric> algorithms with std::move</td><td>Albuquerque</td><td></td><td></td></tr>