Index: libcxx/include/sstream
===================================================================
--- libcxx/include/sstream
+++ libcxx/include/sstream
@@ -41,6 +41,7 @@
     // [stringbuf.members] Member functions:
     basic_string<char_type, traits_type, allocator_type> str() const;
     void str(const basic_string<char_type, traits_type, allocator_type>& s);
+    basic_string_view<char_type, traits_type> view() const noexcept; // C++20
 
 protected:
     // [stringbuf.virtuals] Overridden virtual functions:
@@ -92,6 +93,7 @@
     basic_stringbuf<char_type, traits_type, allocator_type>* rdbuf() const;
     basic_string<char_type, traits_type, allocator_type> str() const;
     void str(const basic_string<char_type, traits_type, allocator_type>& s);
+    basic_string_view<char_type, traits_type> view() const noexcept; // C++20
 };
 
 template <class charT, class traits, class Allocator>
@@ -132,6 +134,7 @@
     basic_stringbuf<char_type, traits_type, allocator_type>* rdbuf() const;
     basic_string<char_type, traits_type, allocator_type> str() const;
     void str(const basic_string<char_type, traits_type, allocator_type>& s);
+    basic_string_view<char_type, traits_type> view() const noexcept; // C++20
 };
 
 template <class charT, class traits, class Allocator>
@@ -172,6 +175,7 @@
     basic_stringbuf<char_type, traits_type, allocator_type>* rdbuf() const;
     basic_string<char_type, traits_type, allocator_type> str() const;
     void str(const basic_string<char_type, traits_type, allocator_type>& str);
+    basic_string_view<char_type, traits_type> view() const noexcept; // C++20
 };
 
 template <class charT, class traits, class Allocator>
@@ -252,6 +256,7 @@
     // [stringbuf.members] Member functions:
     string_type str() const;
     void str(const string_type& __s);
+    basic_string_view<char_type, traits_type> view() const noexcept; // C++20
 
 protected:
     // [stringbuf.virtuals] Overridden virtual functions:
@@ -446,15 +451,7 @@
 basic_string<_CharT, _Traits, _Allocator>
 basic_stringbuf<_CharT, _Traits, _Allocator>::str() const
 {
-    if (__mode_ & ios_base::out)
-    {
-        if (__hm_ < this->pptr())
-            __hm_ = this->pptr();
-        return string_type(this->pbase(), __hm_, __str_.get_allocator());
-    }
-    else if (__mode_ & ios_base::in)
-        return string_type(this->eback(), this->egptr(), __str_.get_allocator());
-    return string_type(__str_.get_allocator());
+    return string_type(this->view(), __str_.get_allocator());
 }
 
 template <class _CharT, class _Traits, class _Allocator>
@@ -490,6 +487,21 @@
     }
 }
 
+template <class _CharT, class _Traits, class _Allocator>
+basic_string_view<_CharT, _Traits>
+basic_stringbuf<_CharT, _Traits, _Allocator>::view() const noexcept
+{
+    if (__mode_ & ios_base::out)
+    {
+        if (__hm_ < this->pptr())
+            __hm_ = this->pptr();
+        return basic_string_view<_CharT, _Traits>(this->pbase(), __hm_);
+    }
+    else if (__mode_ & ios_base::in)
+        return basic_string_view<_CharT, _Traits>(this->eback(), this->egptr());
+    return basic_string_view<_CharT, _Traits>();
+}
+
 template <class _CharT, class _Traits, class _Allocator>
 typename basic_stringbuf<_CharT, _Traits, _Allocator>::int_type
 basic_stringbuf<_CharT, _Traits, _Allocator>::underflow()
@@ -693,6 +705,10 @@
     void str(const string_type& __s) {
         __sb_.str(__s);
     }
+    _LIBCPP_HIDE_FROM_ABI
+    basic_string_view<char_type, traits_type> view() const noexcept {
+        return __sb_.view();
+    }
 };
 
 template <class _CharT, class _Traits, class _Allocator>
@@ -774,6 +790,10 @@
     void str(const string_type& __s) {
         __sb_.str(__s);
     }
+    _LIBCPP_HIDE_FROM_ABI
+    basic_string_view<char_type, traits_type> view() const noexcept {
+        return __sb_.view();
+    }
 };
 
 template <class _CharT, class _Traits, class _Allocator>
@@ -854,6 +874,10 @@
     void str(const string_type& __s) {
         __sb_.str(__s);
     }
+    _LIBCPP_HIDE_FROM_ABI
+    basic_string_view<char_type, traits_type> view() const noexcept {
+        return __sb_.view();
+    }
 };
 
 template <class _CharT, class _Traits, class _Allocator>
Index: libcxx/test/std/input.output/string.streams/istringstream/istringstream.members/str.pass.cpp
===================================================================
--- libcxx/test/std/input.output/string.streams/istringstream/istringstream.members/str.pass.cpp
+++ libcxx/test/std/input.output/string.streams/istringstream/istringstream.members/str.pass.cpp
@@ -25,6 +25,7 @@
         assert(ss.rdbuf() != 0);
         assert(ss.good());
         assert(ss.str() == " 123 456");
+        assert(ss.view() == " 123 456");
         int i = 0;
         ss >> i;
         assert(i == 123);
@@ -34,6 +35,7 @@
         ss.clear();
         assert(ss.good());
         assert(ss.str() == " 789");
+        assert(ss.view() == " 789");
         ss >> i;
         assert(i == 789);
     }
@@ -43,6 +45,7 @@
         assert(ss.rdbuf() != 0);
         assert(ss.good());
         assert(ss.str() == L" 123 456");
+        assert(ss.view() == L" 123 456");
         int i = 0;
         ss >> i;
         assert(i == 123);
@@ -52,6 +55,7 @@
         ss.clear();
         assert(ss.good());
         assert(ss.str() == L" 789");
+        assert(ss.view() == L" 789");
         ss >> i;
         assert(i == 789);
     }
Index: libcxx/test/std/input.output/string.streams/ostringstream/ostringstream.members/str.pass.cpp
===================================================================
--- libcxx/test/std/input.output/string.streams/ostringstream/ostringstream.members/str.pass.cpp
+++ libcxx/test/std/input.output/string.streams/ostringstream/ostringstream.members/str.pass.cpp
@@ -25,15 +25,20 @@
         assert(ss.rdbuf() != 0);
         assert(ss.good());
         assert(ss.str() == " 123 456");
+        assert(ss.view() == " 123 456");
         int i = 0;
         ss << i;
         assert(ss.str() == "0123 456");
+        assert(ss.view() == "0123 456");
         ss << 456;
         assert(ss.str() == "0456 456");
+        assert(ss.view() == "0456 456");
         ss.str(" 789");
         assert(ss.str() == " 789");
+        assert(ss.view() == " 789");
         ss << "abc";
         assert(ss.str() == "abc9");
+        assert(ss.view() == "abc9");
     }
 #ifndef TEST_HAS_NO_WIDE_CHARACTERS
     {
@@ -41,15 +46,20 @@
         assert(ss.rdbuf() != 0);
         assert(ss.good());
         assert(ss.str() == L" 123 456");
+        assert(ss.view() == L" 123 456");
         int i = 0;
         ss << i;
         assert(ss.str() == L"0123 456");
+        assert(ss.view() == L"0123 456");
         ss << 456;
         assert(ss.str() == L"0456 456");
+        assert(ss.view() == L"0456 456");
         ss.str(L" 789");
         assert(ss.str() == L" 789");
+        assert(ss.view() == L" 789");
         ss << L"abc";
         assert(ss.str() == L"abc9");
+        assert(ss.view() == L"abc9");
     }
 #endif
 
Index: libcxx/test/std/input.output/string.streams/stringbuf/stringbuf.members/str.pass.cpp
===================================================================
--- libcxx/test/std/input.output/string.streams/stringbuf/stringbuf.members/str.pass.cpp
+++ libcxx/test/std/input.output/string.streams/stringbuf/stringbuf.members/str.pass.cpp
@@ -23,15 +23,19 @@
     {
         std::stringbuf buf("testing");
         assert(buf.str() == "testing");
+        assert(buf.view() == "testing");
         buf.str("another test");
         assert(buf.str() == "another test");
+        assert(buf.view() == "another test");
     }
 #ifndef TEST_HAS_NO_WIDE_CHARACTERS
     {
         std::wstringbuf buf(L"testing");
         assert(buf.str() == L"testing");
+        assert(buf.view() == L"testing");
         buf.str(L"another test");
         assert(buf.str() == L"another test");
+        assert(buf.view() == L"another test");
     }
 #endif
 
Index: libcxx/test/std/input.output/string.streams/stringstream.members/str.pass.cpp
===================================================================
--- libcxx/test/std/input.output/string.streams/stringstream.members/str.pass.cpp
+++ libcxx/test/std/input.output/string.streams/stringstream.members/str.pass.cpp
@@ -25,6 +25,7 @@
         assert(ss.rdbuf() != 0);
         assert(ss.good());
         assert(ss.str() == " 123 456 ");
+        assert(ss.view() == " 123 456 ");
         int i = 0;
         ss >> i;
         assert(i == 123);
@@ -32,6 +33,7 @@
         assert(i == 456);
         ss << i << ' ' << 123;
         assert(ss.str() == "456 1236 ");
+        assert(ss.view() == "456 1236 ");
         ss.str("5466 89 ");
         ss >> i;
         assert(i == 5466);
@@ -39,6 +41,7 @@
         assert(i == 89);
         ss << i << ' ' << 321;
         assert(ss.str() == "89 3219 ");
+        assert(ss.view() == "89 3219 ");
     }
 #ifndef TEST_HAS_NO_WIDE_CHARACTERS
     {
@@ -46,6 +49,7 @@
         assert(ss.rdbuf() != 0);
         assert(ss.good());
         assert(ss.str() == L" 123 456 ");
+        assert(ss.view() == L" 123 456 ");
         int i = 0;
         ss >> i;
         assert(i == 123);
@@ -53,6 +57,7 @@
         assert(i == 456);
         ss << i << ' ' << 123;
         assert(ss.str() == L"456 1236 ");
+        assert(ss.view() == L"456 1236 ");
         ss.str(L"5466 89 ");
         ss >> i;
         assert(i == 5466);
@@ -60,12 +65,14 @@
         assert(i == 89);
         ss << i << ' ' << 321;
         assert(ss.str() == L"89 3219 ");
+        assert(ss.view() == L"89 3219 ");
     }
 #endif
     {
         std::stringstream ss;
         ss.write("\xd1", 1);
         assert(ss.str().length() == 1);
+        assert(ss.view().length() == 1);
     }
 
   return 0;