libstdc++: Implement C++20 features for <sstream>

Message ID 20201026204733.3116400-1-rodgert@appliantology.com
State New
Headers show
Series
  • libstdc++: Implement C++20 features for <sstream>
Related show

Commit Message

Thomas Rodgers Oct. 26, 2020, 8:47 p.m.
From: Thomas Rodgers <trodgers@redhat.com>


New ctors and ::view() accessor for -
  * basic_stingbuf
  * basic_istringstream
  * basic_ostringstream
  * basic_stringstreamm

New ::get_allocator() accessor for basic_stringbuf.

libstdc++-v3/ChangeLog:
	* acinclude.m4 (glibcxx_SUBDIRS): Add src/c++20.
        * config/abi/pre/gnu.ver: Update GLIBCXX_3.4.29 for the addition of -
	basic_stringbuf::basic_stringbuf(allocator const&),
	basic_stringbuf::basic_stringbuf(openmode, allocator const&),
	basic_stringbuf::basic_stringbuf(basic_string&&, openmode),
	basic_stringbuf::basic_stringbuf(basic_stringbuf&&, allocator const&),
	basic_stringbuf::get_allocator(),
	basic_stringbuf::view(),
	basic_istringstream::basic_istringstream(basic_string&&, openmode),
	basic_istringstream::basic_istringstream(openmode, allocator const&),
	basic_istringstream::view(),
	basic_ostringstream::basic_ostringstream(basic_string&&, openmode),
	basic_ostringstream::basic_ostringstream(openmode, allocator const&),
	basic_ostringstream::view(),
	basic_stringstream::basic_stringstream(basic_string&&, openmode),
	basic_stringstream::basic_stringstream(openmode, allocator const&),
	basic_stringstream::view().
	* configure: Regenerate.
	* include/std/sstream:
	(basic_stringbuf::basic_stringbuf(allocator const&)): New constructor.
	(basic_stringbuf::basic_stringbuf(openmode, allocator const&)): Likewise.
	(basic_stringbuf::basic_stringbuf(basic_string&&, openmode)): Likewise.
	(basic_stringbuf::basic_stringbuf(basic_stringbuf&&, allocator const&)): Likewise.
	(basic_stringbuf::get_allocator()): New method.
	(basic_stringbuf::view()): Likewise.
	(basic_istringstream::basic_istringstream(basic_string&&, openmode)):
	New constructor.
	(basic_istringstream::basic_istringstream(openmode, allocator const&)):
	Likewise
	(basic_istringstream::view()): New method.
	(basic_ostringstream::basic_ostringstream(basic_string&&, openmode)):
	New constructor.
	(basic_ostringstream::basic_ostringstream(openmode, allocator const&)):
	Likewise
	(basic_ostringstream::view()): New method.
	(basic_stringstream::basic_stringstream(basic_string&&, openmode)):
	New constructor.
	(basic_stringstream::basic_stringstream(openmode, allocator const&)):
	Likewise
	(basic_stringstream::view()): New method.
	* src/Makefile.in: Add c++20 directory.
	* src/Makefile.am: Regenerate.
	* src/c++20/Makefile.am: Add makefile for new sub-directory.
	* src/c++20/Makefile.in: Generate.
	* src/c++20/sstream-inst.cc: New file defining explicit
	instantiations for basic_stringbuf, basic_istringstream,
	basic_ostringstream, and basic_stringstream member functions
	added in C++20.
	* testsuite/27_io/basic_stringbuf/cons/char/2.cc: New test.
	* testsuite/27_io/basic_stringbuf/cons/wchar_t/2.cc: Likewise.
	* testsuite/27_io/basic_stringbuf/view/char/2.cc: Likewise.
	* testsuite/27_io/basic_stringbuf/view/wchar_t/2.cc: Likewise.
	* testsuite/27_io/basic_istringstream/cons/char/2.cc: Likewise.
	* testsuite/27_io/basic_istringstream/cons/wchar_t/2.cc: Likewise.
	* testsuite/27_io/basic_istringstream/view/char/2.cc: Likewise.
	* testsuite/27_io/basic_istringstream/view/wchar_t/2.cc: Likewise.
	* testsuite/27_io/basic_ostringstream/cons/char/2.cc: Likewise.
	* testsuite/27_io/basic_ostringstream/cons/wchar_t/2.cc: Likewise.
	* testsuite/27_io/basic_ostringstream/view/char/2.cc: Likewise.
	* testsuite/27_io/basic_ostringstream/view/wchar_t/2.cc: Likewise.
	* testsuite/27_io/basic_stringstream/cons/char/2.cc: Likewise.
	* testsuite/27_io/basic_stringstream/cons/wchar_t/2.cc: Likewise.
	* testsuite/27_io/basic_stringstream/view/char/2.cc: Likewise.
	* testsuite/27_io/basic_stringstream/view/wchar_t/2.cc: Likewise.
---
 libstdc++-v3/acinclude.m4                     |   2 +-
 libstdc++-v3/config/abi/pre/gnu.ver           |  45 ++
 libstdc++-v3/configure                        |  16 +-
 libstdc++-v3/include/std/sstream              | 190 +++++
 libstdc++-v3/src/Makefile.am                  |  12 +-
 libstdc++-v3/src/Makefile.in                  |  14 +-
 libstdc++-v3/src/c++20/Makefile.am            | 105 +++
 libstdc++-v3/src/c++20/Makefile.in            | 735 ++++++++++++++++++
 libstdc++-v3/src/c++20/sstream-inst.cc        | 108 +++
 .../27_io/basic_istringstream/cons/char/1.cc  |  85 ++
 .../basic_istringstream/cons/wchar_t/1.cc     |  85 ++
 .../27_io/basic_istringstream/view/char/1.cc  |  35 +
 .../basic_istringstream/view/wchar_t/1.cc     |  35 +
 .../27_io/basic_ostringstream/cons/char/1.cc  |  85 ++
 .../basic_ostringstream/cons/wchar_t/1.cc     |  85 ++
 .../27_io/basic_ostringstream/view/char/1.cc  |  35 +
 .../basic_ostringstream/view/wchar_t/1.cc     |  35 +
 .../27_io/basic_stringbuf/cons/char/2.cc      | 121 +++
 .../27_io/basic_stringbuf/cons/wchar_t/2.cc   | 105 +++
 .../27_io/basic_stringbuf/view/char/1.cc      |  35 +
 .../27_io/basic_stringbuf/view/wchar_t/1.cc   |  35 +
 .../27_io/basic_stringstream/cons/char/1.cc   |  85 ++
 .../basic_stringstream/cons/wchar_t/1.cc      |  85 ++
 .../27_io/basic_stringstream/view/char/1.cc   |  35 +
 .../basic_stringstream/view/wchar_t/1.cc      |  35 +
 25 files changed, 2231 insertions(+), 12 deletions(-)
 create mode 100644 libstdc++-v3/src/c++20/Makefile.am
 create mode 100644 libstdc++-v3/src/c++20/Makefile.in
 create mode 100644 libstdc++-v3/src/c++20/sstream-inst.cc
 create mode 100644 libstdc++-v3/testsuite/27_io/basic_istringstream/cons/char/1.cc
 create mode 100644 libstdc++-v3/testsuite/27_io/basic_istringstream/cons/wchar_t/1.cc
 create mode 100644 libstdc++-v3/testsuite/27_io/basic_istringstream/view/char/1.cc
 create mode 100644 libstdc++-v3/testsuite/27_io/basic_istringstream/view/wchar_t/1.cc
 create mode 100644 libstdc++-v3/testsuite/27_io/basic_ostringstream/cons/char/1.cc
 create mode 100644 libstdc++-v3/testsuite/27_io/basic_ostringstream/cons/wchar_t/1.cc
 create mode 100644 libstdc++-v3/testsuite/27_io/basic_ostringstream/view/char/1.cc
 create mode 100644 libstdc++-v3/testsuite/27_io/basic_ostringstream/view/wchar_t/1.cc
 create mode 100644 libstdc++-v3/testsuite/27_io/basic_stringbuf/cons/char/2.cc
 create mode 100644 libstdc++-v3/testsuite/27_io/basic_stringbuf/cons/wchar_t/2.cc
 create mode 100644 libstdc++-v3/testsuite/27_io/basic_stringbuf/view/char/1.cc
 create mode 100644 libstdc++-v3/testsuite/27_io/basic_stringbuf/view/wchar_t/1.cc
 create mode 100644 libstdc++-v3/testsuite/27_io/basic_stringstream/cons/char/1.cc
 create mode 100644 libstdc++-v3/testsuite/27_io/basic_stringstream/cons/wchar_t/1.cc
 create mode 100644 libstdc++-v3/testsuite/27_io/basic_stringstream/view/char/1.cc
 create mode 100644 libstdc++-v3/testsuite/27_io/basic_stringstream/view/wchar_t/1.cc

-- 
2.26.2

Comments

H.J. Lu via Gcc-patches Oct. 26, 2020, 9:09 p.m. | #1
On 26/10/20 13:47 -0700, Thomas Rodgers wrote:
>From: Thomas Rodgers <trodgers@redhat.com>

>

>New ctors and ::view() accessor for -

>  * basic_stingbuf

>  * basic_istringstream

>  * basic_ostringstream

>  * basic_stringstreamm

>

>New ::get_allocator() accessor for basic_stringbuf.

>

>libstdc++-v3/ChangeLog:

>	* acinclude.m4 (glibcxx_SUBDIRS): Add src/c++20.

>        * config/abi/pre/gnu.ver: Update GLIBCXX_3.4.29 for the addition of -

>	basic_stringbuf::basic_stringbuf(allocator const&),

>	basic_stringbuf::basic_stringbuf(openmode, allocator const&),

>	basic_stringbuf::basic_stringbuf(basic_string&&, openmode),

>	basic_stringbuf::basic_stringbuf(basic_stringbuf&&, allocator const&),

>	basic_stringbuf::get_allocator(),

>	basic_stringbuf::view(),

>	basic_istringstream::basic_istringstream(basic_string&&, openmode),

>	basic_istringstream::basic_istringstream(openmode, allocator const&),

>	basic_istringstream::view(),

>	basic_ostringstream::basic_ostringstream(basic_string&&, openmode),

>	basic_ostringstream::basic_ostringstream(openmode, allocator const&),

>	basic_ostringstream::view(),

>	basic_stringstream::basic_stringstream(basic_string&&, openmode),

>	basic_stringstream::basic_stringstream(openmode, allocator const&),

>	basic_stringstream::view().


As discussed on IRC< please don't name every one of these functions
for the linker script changes, it's just redundant noise. They're
already listed below in the include/std/sstream changes.

Look at past changelog entries for the gnu.ver file.

>	* configure: Regenerate.

>	* include/std/sstream:

>	(basic_stringbuf::basic_stringbuf(allocator const&)): New constructor.

>	(basic_stringbuf::basic_stringbuf(openmode, allocator const&)): Likewise.

>	(basic_stringbuf::basic_stringbuf(basic_string&&, openmode)): Likewise.

>	(basic_stringbuf::basic_stringbuf(basic_stringbuf&&, allocator const&)): Likewise.


New line before the Likewise.


There are a few formatting changes mentioned below. OK for trunk with
those changes. Thanks. Go ahead and commit the <syncstream> patch
after this one too.


>	(basic_stringbuf::get_allocator()): New method.

>	(basic_stringbuf::view()): Likewise.

>	(basic_istringstream::basic_istringstream(basic_string&&, openmode)):

>	New constructor.

>	(basic_istringstream::basic_istringstream(openmode, allocator const&)):

>	Likewise

>	(basic_istringstream::view()): New method.

>	(basic_ostringstream::basic_ostringstream(basic_string&&, openmode)):

>	New constructor.

>	(basic_ostringstream::basic_ostringstream(openmode, allocator const&)):

>	Likewise

>	(basic_ostringstream::view()): New method.

>	(basic_stringstream::basic_stringstream(basic_string&&, openmode)):

>	New constructor.

>	(basic_stringstream::basic_stringstream(openmode, allocator const&)):

>	Likewise

>	(basic_stringstream::view()): New method.

>	* src/Makefile.in: Add c++20 directory.

>	* src/Makefile.am: Regenerate.

>	* src/c++20/Makefile.am: Add makefile for new sub-directory.

>	* src/c++20/Makefile.in: Generate.

>	* src/c++20/sstream-inst.cc: New file defining explicit

>	instantiations for basic_stringbuf, basic_istringstream,

>	basic_ostringstream, and basic_stringstream member functions

>	added in C++20.

>	* testsuite/27_io/basic_stringbuf/cons/char/2.cc: New test.

>	* testsuite/27_io/basic_stringbuf/cons/wchar_t/2.cc: Likewise.

>	* testsuite/27_io/basic_stringbuf/view/char/2.cc: Likewise.

>	* testsuite/27_io/basic_stringbuf/view/wchar_t/2.cc: Likewise.

>	* testsuite/27_io/basic_istringstream/cons/char/2.cc: Likewise.

>	* testsuite/27_io/basic_istringstream/cons/wchar_t/2.cc: Likewise.

>	* testsuite/27_io/basic_istringstream/view/char/2.cc: Likewise.

>	* testsuite/27_io/basic_istringstream/view/wchar_t/2.cc: Likewise.

>	* testsuite/27_io/basic_ostringstream/cons/char/2.cc: Likewise.

>	* testsuite/27_io/basic_ostringstream/cons/wchar_t/2.cc: Likewise.

>	* testsuite/27_io/basic_ostringstream/view/char/2.cc: Likewise.

>	* testsuite/27_io/basic_ostringstream/view/wchar_t/2.cc: Likewise.

>	* testsuite/27_io/basic_stringstream/cons/char/2.cc: Likewise.

>	* testsuite/27_io/basic_stringstream/cons/wchar_t/2.cc: Likewise.

>	* testsuite/27_io/basic_stringstream/view/char/2.cc: Likewise.

>	* testsuite/27_io/basic_stringstream/view/wchar_t/2.cc: Likewise.

>---

> libstdc++-v3/acinclude.m4                     |   2 +-

> libstdc++-v3/config/abi/pre/gnu.ver           |  45 ++

> libstdc++-v3/configure                        |  16 +-

> libstdc++-v3/include/std/sstream              | 190 +++++

> libstdc++-v3/src/Makefile.am                  |  12 +-

> libstdc++-v3/src/Makefile.in                  |  14 +-

> libstdc++-v3/src/c++20/Makefile.am            | 105 +++

> libstdc++-v3/src/c++20/Makefile.in            | 735 ++++++++++++++++++

> libstdc++-v3/src/c++20/sstream-inst.cc        | 108 +++

> .../27_io/basic_istringstream/cons/char/1.cc  |  85 ++

> .../basic_istringstream/cons/wchar_t/1.cc     |  85 ++

> .../27_io/basic_istringstream/view/char/1.cc  |  35 +

> .../basic_istringstream/view/wchar_t/1.cc     |  35 +

> .../27_io/basic_ostringstream/cons/char/1.cc  |  85 ++

> .../basic_ostringstream/cons/wchar_t/1.cc     |  85 ++

> .../27_io/basic_ostringstream/view/char/1.cc  |  35 +

> .../basic_ostringstream/view/wchar_t/1.cc     |  35 +

> .../27_io/basic_stringbuf/cons/char/2.cc      | 121 +++

> .../27_io/basic_stringbuf/cons/wchar_t/2.cc   | 105 +++

> .../27_io/basic_stringbuf/view/char/1.cc      |  35 +

> .../27_io/basic_stringbuf/view/wchar_t/1.cc   |  35 +

> .../27_io/basic_stringstream/cons/char/1.cc   |  85 ++

> .../basic_stringstream/cons/wchar_t/1.cc      |  85 ++

> .../27_io/basic_stringstream/view/char/1.cc   |  35 +

> .../basic_stringstream/view/wchar_t/1.cc      |  35 +

> 25 files changed, 2231 insertions(+), 12 deletions(-)

> create mode 100644 libstdc++-v3/src/c++20/Makefile.am

> create mode 100644 libstdc++-v3/src/c++20/Makefile.in

> create mode 100644 libstdc++-v3/src/c++20/sstream-inst.cc

> create mode 100644 libstdc++-v3/testsuite/27_io/basic_istringstream/cons/char/1.cc

> create mode 100644 libstdc++-v3/testsuite/27_io/basic_istringstream/cons/wchar_t/1.cc

> create mode 100644 libstdc++-v3/testsuite/27_io/basic_istringstream/view/char/1.cc

> create mode 100644 libstdc++-v3/testsuite/27_io/basic_istringstream/view/wchar_t/1.cc

> create mode 100644 libstdc++-v3/testsuite/27_io/basic_ostringstream/cons/char/1.cc

> create mode 100644 libstdc++-v3/testsuite/27_io/basic_ostringstream/cons/wchar_t/1.cc

> create mode 100644 libstdc++-v3/testsuite/27_io/basic_ostringstream/view/char/1.cc

> create mode 100644 libstdc++-v3/testsuite/27_io/basic_ostringstream/view/wchar_t/1.cc

> create mode 100644 libstdc++-v3/testsuite/27_io/basic_stringbuf/cons/char/2.cc

> create mode 100644 libstdc++-v3/testsuite/27_io/basic_stringbuf/cons/wchar_t/2.cc

> create mode 100644 libstdc++-v3/testsuite/27_io/basic_stringbuf/view/char/1.cc

> create mode 100644 libstdc++-v3/testsuite/27_io/basic_stringbuf/view/wchar_t/1.cc

> create mode 100644 libstdc++-v3/testsuite/27_io/basic_stringstream/cons/char/1.cc

> create mode 100644 libstdc++-v3/testsuite/27_io/basic_stringstream/cons/wchar_t/1.cc

> create mode 100644 libstdc++-v3/testsuite/27_io/basic_stringstream/view/char/1.cc

> create mode 100644 libstdc++-v3/testsuite/27_io/basic_stringstream/view/wchar_t/1.cc

>

>diff --git a/libstdc++-v3/acinclude.m4 b/libstdc++-v3/acinclude.m4

>index 133125ec4fa..b9452dd74cd 100644

>--- a/libstdc++-v3/acinclude.m4

>+++ b/libstdc++-v3/acinclude.m4

>@@ -49,7 +49,7 @@ AC_DEFUN([GLIBCXX_CONFIGURE], [

>   # Keep these sync'd with the list in Makefile.am.  The first provides an

>   # expandable list at autoconf time; the second provides an expandable list

>   # (i.e., shell variable) at configure time.

>-  m4_define([glibcxx_SUBDIRS],[include libsupc++ src src/c++98 src/c++11 src/c++17 src/filesystem doc po testsuite python])

>+  m4_define([glibcxx_SUBDIRS],[include libsupc++ src src/c++98 src/c++11 src/c++17 src/c++20 src/filesystem doc po testsuite python])

>   SUBDIRS='glibcxx_SUBDIRS'

>

>   # These need to be absolute paths, yet at the same time need to

>diff --git a/libstdc++-v3/config/abi/pre/gnu.ver b/libstdc++-v3/config/abi/pre/gnu.ver

>index 6a2b2da33f5..a782776bd5f 100644

>--- a/libstdc++-v3/config/abi/pre/gnu.ver

>+++ b/libstdc++-v3/config/abi/pre/gnu.ver

>@@ -2325,6 +2325,51 @@ GLIBCXX_3.4.29 {

>     # std::__throw_bad_array_new_length()

>     _ZSt28__throw_bad_array_new_lengthv;

>

>+    # basic_stringbuf::basic_stringbuf(allocator const&)

>+    _ZNSt7__cxx1115basic_stringbufI[cw]St11char_traitsI[cw]ESaI[cw]EEC1ERKS3_;

>+

>+    # basic_stringbuf::basic_stringbuf(ios_base::openmode, allocator const&)

>+    _ZNSt7__cxx1115basic_stringbufI[cw]St11char_traitsI[cw]ESaI[cw]EEC1ESt13_Ios_OpenmodeRKS3;

>+

>+    # basic_stringbuf::basic_stringbuf(basic_string&&, ios_base::openmode)

>+    _ZNSt7__cxx1115basic_stringbufI[cw]St11char_traitsI[cw]ESaI[cw]EEC1EONS_12basic_stringI[cw]S2_S3_EESt13_Ios_Openmode;

>+

>+    # basic_stringbuf::basic_stringbuf(basic_stringbuf&&, allocator const&)

>+    _ZNSt7__cxx1115basic_stringbufI[cw]St11char_traitsI[cw]ESaIcEEC1EOS4_RKS3_;

>+

>+    # basic_stringbuf::get_allocator()

>+    _ZNKSt7__cxx1115basic_stringbufI[cw]St11char_traitsI[cw]ESaI[cw]EE13get_allocatorEv;

>+

>+    # basic_stringbuf::view()

>+    _ZNKSt7__cxx1115basic_stringbufI[cw]St11char_traitsI[cw]ESaI[cw]EE4viewEv;

>+

>+    # basic_istringstream::basic_istringstream(basic_string&&, ios_base::openmode)

>+    _ZNSt7__cxx1119basic_istringstreamI[cw]St11char_traitsI[cw]ESaIcEEC1EONS_12basic_stringI[cw]S2_S3_EESt13_Ios_Openmode;

>+

>+    # basic_istringstream::basic_istringstream(ios_base::openmode, allocator const&)

>+    _ZNSt7__cxx1119basic_istringstreamI[cw]St11char_traitsI[cw]ESaI[cw]EEC1ESt13_Ios_OpenmodeRKS3_;

>+

>+    # basic_istringstream::view()

>+    _ZNKSt7__cxx1119basic_istringstreamI[cw]St11char_traitsI[cw]ESaI[cw]EE4viewEv;

>+

>+    # basic_ostringstream::basic_ostringstream(basic_string&&, ios_base::openmode)

>+    _ZNSt7__cxx1119basic_ostringstreamI[cw]St11char_traitsI[cw]ESaIcEEC1EONS_12basic_stringI[cw]S2_S3_EESt13_Ios_Openmode;

>+

>+    # basic_ostringstream::basic_ostringstream(ios_base::openmode, allocator const&)

>+    _ZNSt7__cxx1119basic_ostringstreamI[cw]St11char_traitsI[cw]ESaIcEEC1ESt13_Ios_OpenmodeRKS3_;

>+

>+    # basic_ostringstream::view()

>+    _ZNKSt7__cxx1119basic_ostringstreamI[cw]St11char_traitsI[cw]ESaI[cw]EE4viewEv;

>+

>+    # basic_stringstream::basic_stringstream(basic_string&&, ios_base::openmode)

>+    _ZNSt7__cxx1119basic_stringstreamI[cw]St11char_traitsI[cw]ESaIcEEC1EONS_12basic_stringI[cw]S2_S3_EESt13_Ios_Openmode;

>+

>+    # basic_stringstream::basic_stringstream(ios_base::openmode, allocator const&)

>+    _ZNSt7__cxx1119basic_stringstreamI[cw]St11char_traitsI[cw]ESaIcEEC1ESt13_Ios_OpenmodeRKS3_;

>+

>+    # basic_stringstream::view()

>+    _ZNKSt7__cxx1119basic_stringstreamI[cw]St11char_traitsI[cw]ESaI[cw]EE4viewEv;

>+

> } GLIBCXX_3.4.28;

>

> # Symbols in the support library (libsupc++) have their own tag.

>diff --git a/libstdc++-v3/include/std/sstream b/libstdc++-v3/include/std/sstream

>index 9cca54d17d1..b191c471b39 100644

>--- a/libstdc++-v3/include/std/sstream

>+++ b/libstdc++-v3/include/std/sstream

>@@ -165,6 +165,55 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11

>       }

> #endif

>

>+#if __cplusplus > 201703L && _GLIBCXX_USE_CXX11_ABI

>+      using __sv_type = basic_string_view<char_type, traits_type>;

>+

>+      basic_stringbuf(const allocator_type& __a)

>+      : basic_stringbuf(ios_base::in | std::ios_base::out, __a)

>+      { }

>+

>+      basic_stringbuf(ios_base::openmode __mode,

>+		      const allocator_type& __a)

>+      : __streambuf_type(), _M_mode(__mode), _M_string(__a)

>+      { }

>+

>+      explicit

>+      basic_stringbuf(__string_type&& __s,

>+	              ios_base::openmode __mode = ios_base::in

>+						  | ios_base::out )

>+      : __streambuf_type(), _M_mode(__mode), _M_string(move(__s))

>+      { }

>+

>+      template<typename _SAlloc>

>+      basic_stringbuf(const basic_string<_CharT, _Traits, _SAlloc>& __s,

>+		      const allocator_type& __a )

>+      : basic_stringbuf(__s, ios_base::in | std::ios_base::out, __a )

>+      { }

>+

>+      template<typename _SAlloc>

>+      basic_stringbuf(const basic_string<_CharT, _Traits, _SAlloc>& __s,

>+		      ios_base::openmode __mode,

>+		      const allocator_type& __a)

>+      : __streambuf_type(), _M_mode(__mode),

>+      _M_string(static_cast<__sv_type>(__s), __a)

>+      { }

>+

>+      template<typename _SAlloc>

>+	explicit

>+	basic_stringbuf(const basic_string<_CharT, _Traits, _SAlloc>& __s,

>+	                ios_base::openmode __mode = ios_base::in

>+						    | ios_base::out)

>+	: basic_stringbuf(__s, __mode, allocator_type{})

>+	{ }

>+

>+      basic_stringbuf(basic_stringbuf&& __rhs, const allocator_type& __a)

>+      : basic_stringbuf(std::move(__rhs), __a, __xfer_bufptrs(__rhs, this))

>+      { __rhs._M_sync(const_cast<char_type*>(__rhs._M_string.data()), 0, 0); }

>+

>+      allocator_type get_allocator() const noexcept

>+      { return _M_string.get_allocator(); }

>+#endif

>+

>       // Get and set:

>       /**

>        *  @brief  Copying out the string buffer.

>@@ -207,6 +256,23 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11

> 	_M_stringbuf_init(_M_mode);

>       }

>

>+#if __cplusplus > 201703L && _GLIBCXX_USE_CXX11_ABI

>+      __sv_type

>+      view() const noexcept

>+      {

>+	if (this->pptr())

>+	  {

>+	    // The current egptr() may not be the actual string end.

>+	    if (this->pptr() > this->egptr())

>+	      return __sv_type(this->pbase(), this->pptr());

>+	    else

>+	      return __sv_type(this->pbase(), this->egptr());

>+	  }

>+	else

>+	  return static_cast<__sv_type>(_M_string);

>+      }

>+#endif

>+

>     protected:

>       // Common initialization code goes here.

>       void

>@@ -369,6 +435,16 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11

>       : __streambuf_type(static_cast<const __streambuf_type&>(__rhs)),

>       _M_mode(__rhs._M_mode), _M_string(std::move(__rhs._M_string))

>       { }

>+

>+#if __cplusplus > 201703L && _GLIBCXX_USE_CXX11_ABI

>+      // The move constructor initializes an __xfer_bufptrs temporary then

>+      // delegates to this constructor to performs moves during its lifetime.

>+      basic_stringbuf(basic_stringbuf&& __rhs, const allocator_type& __a,

>+		      __xfer_bufptrs&&)

>+      : __streambuf_type(static_cast<const __streambuf_type&>(__rhs)),

>+      _M_mode(__rhs._M_mode), _M_string(std::move(__rhs._M_string), __a)

>+      { }

>+#endif

> #endif

>     };

>

>@@ -500,6 +576,38 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11

>       }

> #endif

>

>+#if __cplusplus > 201703L && _GLIBCXX_USE_CXX11_ABI

>+      basic_istringstream(ios_base::openmode __mode, const allocator_type& __a)

>+      : __istream_type(), _M_stringbuf(__mode | ios_base::in, __a)

>+      { this->init(std::__addressof(_M_stringbuf)); }

>+

>+      explicit basic_istringstream(__string_type&& __str,


Newline after explicit.

>+	                           ios_base::openmode __mode = ios_base::in )

>+      : __istream_type(), _M_stringbuf(std::move(__str), __mode | ios_base::in)

>+      { this->init(std::__addressof(_M_stringbuf)); }

>+

>+      template<typename _SAlloc>

>+	basic_istringstream(const basic_string<_CharT, _Traits, _SAlloc>& __str,

>+			    const allocator_type& __a)

>+	: basic_istringstream(__str, ios_base::in, __a)

>+	{ }

>+

>+      template<typename _SAlloc>

>+	basic_istringstream(const basic_string<_CharT, _Traits, _SAlloc>& __str,

>+			    ios_base::openmode __mode,

>+			    const allocator_type& __a)

>+	: __istream_type(),

>+	_M_stringbuf(__string_type(__str.data(), __str.size()),

>+		     __mode | ios_base::in, __a)

>+	{ this->init(std::__addressof(_M_stringbuf)); }

>+

>+      template<typename _SAlloc>

>+	explicit basic_istringstream(const basic_string<_CharT, _Traits, _SAlloc>& __str,


Newline after explicit.

>+	                             ios_base::openmode __mode = ios_base::in)

>+	: basic_istringstream(__str, __mode, allocator_type())

>+	{ }

>+#endif

>+

>       // Members:

>       /**

>        *  @brief  Accessing the underlying buffer.

>@@ -528,6 +636,12 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11

>       void

>       str(const __string_type& __s)

>       { _M_stringbuf.str(__s); }

>+

>+#if __cplusplus > 201703L && _GLIBCXX_USE_CXX11_ABI

>+      basic_string_view<char_type, traits_type>

>+      view() const noexcept

>+      { return _M_stringbuf.view(); }

>+#endif

>     };

>

>

>@@ -658,6 +772,38 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11

>       }

> #endif

>

>+#if __cplusplus > 201703L && _GLIBCXX_USE_CXX11_ABI

>+      basic_ostringstream(ios_base::openmode __mode, const allocator_type& __a)

>+      : __ostream_type(), _M_stringbuf(__mode | ios_base::out, __a)

>+      { this->init(std::__addressof(_M_stringbuf)); }

>+

>+      explicit basic_ostringstream(__string_type&& __str,


Newline after explicit.

>+	                           ios_base::openmode __mode = ios_base::out )

>+      : __ostream_type(), _M_stringbuf(std::move(__str), __mode | ios_base::out)

>+      { this->init(std::__addressof(_M_stringbuf)); }

>+

>+      template<typename _SAlloc>

>+	basic_ostringstream(const basic_string<_CharT, _Traits, _SAlloc>& __str,

>+			    const allocator_type& __a)

>+	: basic_ostringstream(__str, ios_base::out, __a)

>+	{ }

>+

>+      template<typename _SAlloc>

>+	basic_ostringstream(const basic_string<_CharT, _Traits, _SAlloc>& __str,

>+			    ios_base::openmode __mode,

>+			    const allocator_type& __a)

>+	: __ostream_type(),

>+	_M_stringbuf(__string_type(__str.data(), __str.size()),

>+		     __mode | ios_base::out, __a)

>+	{ this->init(std::__addressof(_M_stringbuf)); }

>+

>+      template<typename _SAlloc>

>+	explicit basic_ostringstream(const basic_string<_CharT, _Traits, _SAlloc>& __str,


Newline after explicit.

>+	                             ios_base::openmode __mode = ios_base::out)

>+	: basic_ostringstream(__str, __mode, allocator_type())

>+	{ }

>+#endif

>+

>       // Members:

>       /**

>        *  @brief  Accessing the underlying buffer.

>@@ -686,6 +832,12 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11

>       void

>       str(const __string_type& __s)

>       { _M_stringbuf.str(__s); }

>+

>+#if __cplusplus > 201703L && _GLIBCXX_USE_CXX11_ABI

>+      basic_string_view<char_type, traits_type>

>+      view() const noexcept

>+      { return _M_stringbuf.view(); }

>+#endif

>     };

>

>

>@@ -812,6 +964,38 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11

>       }

> #endif

>

>+#if __cplusplus > 201703L && _GLIBCXX_USE_CXX11_ABI

>+      basic_stringstream(ios_base::openmode __mode, const allocator_type& __a)

>+      : __iostream_type(), _M_stringbuf(__mode, __a)

>+      { this->init(&_M_stringbuf); }

>+

>+      explicit basic_stringstream(__string_type&& __str,


Newline after explicit.

>+	                          ios_base::openmode __mode = ios_base::out

>+							      | ios_base::out)

>+      : __iostream_type(), _M_stringbuf(std::move(__str), __mode)

>+      { this->init(std::__addressof(_M_stringbuf)); }

>+

>+      template<typename _SAlloc>

>+	basic_stringstream(const basic_string<_CharT, _Traits, _SAlloc>& __str,

>+			   const allocator_type& __a)

>+	: basic_stringstream(__str, ios_base::in | ios_base::out, __a)

>+	{ }

>+

>+      template<typename _SAlloc>

>+	basic_stringstream(const basic_string<_CharT, _Traits, _SAlloc>& __str,

>+			   ios_base::openmode __mode, const allocator_type& __a)

>+	: __iostream_type(),

>+	_M_stringbuf(__string_type(__str.data(), __str.size()), __mode, __a)

>+	{ this->init(std::__addressof(_M_stringbuf)); }

>+

>+      template<typename _SAlloc>

>+	explicit basic_stringstream(const basic_string<_CharT, _Traits, _SAlloc>& __str,


Newline after explicit.

>+	                            ios_base::openmode __mode = ios_base::in

>+								| ios_base::out)

>+	: basic_stringstream(__str, __mode, allocator_type())

>+	{ }

>+#endif

>+

>       // Members:

>       /**

>        *  @brief  Accessing the underlying buffer.

>@@ -840,6 +1024,12 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11

>       void

>       str(const __string_type& __s)

>       { _M_stringbuf.str(__s); }

>+

>+#if __cplusplus > 201703L && _GLIBCXX_USE_CXX11_ABI

>+      basic_string_view<char_type, traits_type>

>+      view() const noexcept

>+      { return _M_stringbuf.view(); }

>+#endif

>     };

>

> #if __cplusplus >= 201103L

>diff --git a/libstdc++-v3/src/Makefile.am b/libstdc++-v3/src/Makefile.am

>index a139adc81b3..9a6807ae8c6 100644

>--- a/libstdc++-v3/src/Makefile.am

>+++ b/libstdc++-v3/src/Makefile.am

>@@ -29,7 +29,7 @@ filesystem_dir =

> endif

>

> ## Keep this list sync'd with acinclude.m4:GLIBCXX_CONFIGURE.

>-SUBDIRS = c++98 c++11 c++17 $(filesystem_dir)

>+SUBDIRS = c++98 c++11 c++17 c++20 $(filesystem_dir)

>

> # Cross compiler support.

> if VTV_CYGMIN

>@@ -60,6 +60,7 @@ endif

> vpath % $(top_srcdir)/src/c++98

> vpath % $(top_srcdir)/src/c++11

> vpath % $(top_srcdir)/src/c++17

>+vpath % $(top_srcdir)/src/c++20

> if ENABLE_FILESYSTEM_TS

> vpath % $(top_srcdir)/src/filesystem

> endif

>@@ -95,14 +96,16 @@ libstdc___la_LIBADD = \

> 	$(top_builddir)/libsupc++/libsupc++convenience.la \

> 	$(top_builddir)/src/c++98/libc++98convenience.la \

> 	$(top_builddir)/src/c++11/libc++11convenience.la \

>-	$(top_builddir)/src/c++17/libc++17convenience.la

>+	$(top_builddir)/src/c++17/libc++17convenience.la \

>+	$(top_builddir)/src/c++20/libc++20convenience.la

>

> libstdc___la_DEPENDENCIES = \

> 	${version_dep} \

> 	$(top_builddir)/libsupc++/libsupc++convenience.la \

> 	$(top_builddir)/src/c++98/libc++98convenience.la \

> 	$(top_builddir)/src/c++11/libc++11convenience.la \

>-	$(top_builddir)/src/c++17/libc++17convenience.la

>+	$(top_builddir)/src/c++17/libc++17convenience.la \

>+	$(top_builddir)/src/c++20/libc++20convenience.la

>

> libstdc___la_LDFLAGS = \

> 	-version-info $(libtool_VERSION) ${version_arg} -lm

>@@ -153,7 +156,8 @@ compatibility-condvar.o: compatibility-condvar.cc

> # segregated in the sources with -D_GLIBCXX_SHARED.

> #

> # In the sub-directories of libsupc++, src/c++98, src/c++11, src/c++17,

>-# only -prefer-pic objects are generated for the convenience libraries.

>+# src/c++20, only -prefer-pic objects are generated for the convenience

>+# libraries.

> #

> # In the main src directory, make shared and static objects just for

> # the compat libraries. Shared objects are compiled with -prefer-pic

>diff --git a/libstdc++-v3/src/c++20/Makefile.am b/libstdc++-v3/src/c++20/Makefile.am

>new file mode 100644

>index 00000000000..423a79f3686

>--- /dev/null

>+++ b/libstdc++-v3/src/c++20/Makefile.am

>@@ -0,0 +1,105 @@

>+## Makefile for the C++20 sources of the GNU C++ Standard library.

>+##

>+## Copyright (C) 1997-2020 Free Software Foundation, Inc.

>+##

>+## This file is part of the libstdc++ version 3 distribution.

>+## Process this file with automake to produce Makefile.in.

>+

>+## 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/>.

>+

>+include $(top_srcdir)/fragment.am

>+

>+# Convenience library for C++17 runtime.

>+noinst_LTLIBRARIES = libc++20convenience.la

>+

>+headers =

>+

>+if ENABLE_EXTERN_TEMPLATE

>+# XTEMPLATE_FLAGS = -fno-implicit-templates

>+inst_sources = \

>+	sstream-inst.cc

>+else

>+# XTEMPLATE_FLAGS =

>+inst_sources =

>+endif

>+

>+sources =

>+

>+vpath % $(top_srcdir)/src/c++20

>+

>+libc__20convenience_la_SOURCES = $(sources)  $(inst_sources)

>+

>+# AM_CXXFLAGS needs to be in each subdirectory so that it can be

>+# modified in a per-library or per-sub-library way.  Need to manually

>+# set this option because CONFIG_CXXFLAGS has to be after

>+# OPTIMIZE_CXXFLAGS on the compile line so that -O2 can be overridden

>+# as the occasion calls for it.

>+AM_CXXFLAGS = \

>+	-std=gnu++20 \

>+	$(glibcxx_lt_pic_flag) $(glibcxx_compiler_shared_flag) \

>+	$(XTEMPLATE_FLAGS) $(VTV_CXXFLAGS) \

>+	$(WARN_CXXFLAGS) $(OPTIMIZE_CXXFLAGS) $(CONFIG_CXXFLAGS) \

>+	-fimplicit-templates

>+

>+AM_MAKEFLAGS = \

>+	"gxx_include_dir=$(gxx_include_dir)"

>+

>+# Libtool notes

>+

>+# 1) In general, libtool expects an argument such as `--tag=CXX' when

>+# using the C++ compiler, because that will enable the settings

>+# detected when C++ support was being configured.  However, when no

>+# such flag is given in the command line, libtool attempts to figure

>+# it out by matching the compiler name in each configuration section

>+# against a prefix of the command line.  The problem is that, if the

>+# compiler name and its initial flags stored in the libtool

>+# configuration file don't match those in the command line, libtool

>+# can't decide which configuration to use, and it gives up.  The

>+# correct solution is to add `--tag CXX' to LTCXXCOMPILE and maybe

>+# CXXLINK, just after $(LIBTOOL), so that libtool doesn't have to

>+# attempt to infer which configuration to use.

>+#

>+# The second tag argument, `--tag disable-shared` means that libtool

>+# only compiles each source once, for static objects. In actuality,

>+# glibcxx_lt_pic_flag and glibcxx_compiler_shared_flag are added to

>+# the libtool command that is used create the object, which is

>+# suitable for shared libraries.  The `--tag disable-shared` must be

>+# placed after --tag CXX lest things CXX undo the affect of

>+# disable-shared.

>+

>+# 2) Need to explicitly set LTCXXCOMPILE so that EXTRA_CXX_FLAGS is

>+# last. (That way, things like -O2 passed down from the toplevel can

>+# be overridden by --enable-debug.)

>+LTCXXCOMPILE = \

>+	$(LIBTOOL) --tag CXX --tag disable-shared \

>+	$(AM_LIBTOOLFLAGS) $(LIBTOOLFLAGS) \

>+	--mode=compile $(CXX) $(TOPLEVEL_INCLUDES) \

>+	$(AM_CPPFLAGS) $(CPPFLAGS) $(AM_CXXFLAGS) $(CXXFLAGS) $(EXTRA_CXX_FLAGS)

>+

>+LTLDFLAGS = $(shell $(SHELL) $(top_srcdir)/../libtool-ldflags $(LDFLAGS))

>+

>+# 3) We'd have a problem when building the shared libstdc++ object if

>+# the rules automake generates would be used.  We cannot allow g++ to

>+# be used since this would add -lstdc++ to the link line which of

>+# course is problematic at this point.  So, we get the top-level

>+# directory to configure libstdc++-v3 to use gcc as the C++

>+# compilation driver.

>+CXXLINK = \

>+	$(LIBTOOL) --tag CXX --tag disable-shared \

>+	$(AM_LIBTOOLFLAGS) $(LIBTOOLFLAGS) \

>+	--mode=link $(CXX) \

>+	$(VTV_CXXLINKFLAGS) \

>+	$(OPT_LDFLAGS) $(SECTION_LDFLAGS) $(AM_CXXFLAGS) $(LTLDFLAGS) -o $@

>diff --git a/libstdc++-v3/src/c++20/Makefile.in b/libstdc++-v3/src/c++20/Makefile.in

>new file mode 100644

>index 00000000000..0e2de19ae59

>diff --git a/libstdc++-v3/src/c++20/sstream-inst.cc b/libstdc++-v3/src/c++20/sstream-inst.cc

>new file mode 100644

>index 00000000000..e04560d28c8

>--- /dev/null

>+++ b/libstdc++-v3/src/c++20/sstream-inst.cc

>@@ -0,0 +1,108 @@

>+// Explicit instantiation file.

>+

>+// Copyright (C) 2020 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.

>+

>+// Under Section 7 of GPL version 3, you are granted additional

>+// permissions described in the GCC Runtime Library Exception, version

>+// 3.1, as published by the Free Software Foundation.

>+

>+// You should have received a copy of the GNU General Public License and

>+// a copy of the GCC Runtime Library Exception along with this program;

>+// see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see

>+// <http://www.gnu.org/licenses/>.

>+

>+//

>+// ISO C++ 14882:

>+//

>+

>+// Instantiations in this file are only for the new SSO std::string ABI

>+#include <sstream>

>+

>+namespace std _GLIBCXX_VISIBILITY(default)

>+{

>+_GLIBCXX_BEGIN_NAMESPACE_VERSION

>+

>+template basic_stringbuf<char>::basic_stringbuf(const allocator_type&);

>+template basic_stringbuf<char>::basic_stringbuf(ios_base::openmode,

>+						const allocator_type&);

>+template basic_stringbuf<char>::basic_stringbuf(__string_type&&,

>+						ios_base::openmode);

>+template basic_stringbuf<char>::basic_stringbuf(basic_stringbuf&&,

>+						const allocator_type&);

>+template basic_stringbuf<char>::allocator_type

>+basic_stringbuf<char>::get_allocator() const noexcept;

>+template basic_stringbuf<char>::__sv_type

>+basic_stringbuf<char>::view() const noexcept;

>+

>+template basic_istringstream<char>::basic_istringstream(ios_base::openmode,

>+							const allocator_type&);

>+template basic_istringstream<char>::basic_istringstream(__string_type&&,

>+							ios_base::openmode);

>+template string_view

>+basic_istringstream<char>::view() const noexcept;

>+

>+template basic_ostringstream<char>::basic_ostringstream(ios_base::openmode,

>+							const allocator_type&);

>+template basic_ostringstream<char>::basic_ostringstream(__string_type&&,

>+							ios_base::openmode);

>+template string_view

>+basic_ostringstream<char>::view() const noexcept;

>+

>+template basic_stringstream<char>::basic_stringstream(ios_base::openmode,

>+						      const allocator_type&);

>+template basic_stringstream<char>::basic_stringstream(__string_type&&,

>+						      ios_base::openmode);

>+template string_view

>+basic_stringstream<char>::view() const noexcept;

>+

>+#ifdef _GLIBCXX_USE_WCHAR_T

>+using wsv_type = basic_string_view<wchar_t>;

>+

>+template basic_stringbuf<wchar_t>::basic_stringbuf(const allocator_type&);

>+template basic_stringbuf<wchar_t>::basic_stringbuf(ios_base::openmode,

>+						   const allocator_type&);

>+template basic_stringbuf<wchar_t>::basic_stringbuf(__string_type&&,

>+						   ios_base::openmode);

>+template basic_stringbuf<wchar_t>::basic_stringbuf(basic_stringbuf&&,

>+						   const allocator_type&);

>+template basic_stringbuf<wchar_t>::allocator_type

>+basic_stringbuf<wchar_t>::get_allocator() const noexcept;

>+

>+template basic_istringstream<wchar_t>::__stringbuf_type::__sv_type

>+basic_stringbuf<wchar_t>::view() const noexcept;

>+

>+template basic_istringstream<wchar_t>::basic_istringstream(ios_base::openmode,

>+							   const allocator_type&);

>+template basic_istringstream<wchar_t>::basic_istringstream(__string_type&&,

>+							   ios_base::openmode);

>+template wstring_view

>+basic_istringstream<wchar_t>::view() const noexcept;

>+

>+template basic_ostringstream<wchar_t>::basic_ostringstream(ios_base::openmode,

>+							   const allocator_type&);

>+template basic_ostringstream<wchar_t>::basic_ostringstream(__string_type&&,

>+							   ios_base::openmode);

>+template wstring_view

>+basic_ostringstream<wchar_t>::view() const noexcept;

>+

>+template basic_stringstream<wchar_t>::basic_stringstream(ios_base::openmode,

>+							 const allocator_type&);

>+template basic_stringstream<wchar_t>::basic_stringstream(__string_type&&,

>+							 ios_base::openmode);

>+template wstring_view

>+basic_stringstream<wchar_t>::view() const noexcept;

>+#endif

>+

>+_GLIBCXX_END_NAMESPACE_VERSION

>+}

>diff --git a/libstdc++-v3/testsuite/27_io/basic_istringstream/cons/char/1.cc b/libstdc++-v3/testsuite/27_io/basic_istringstream/cons/char/1.cc

>new file mode 100644

>index 00000000000..496aa6963e0

>--- /dev/null

>+++ b/libstdc++-v3/testsuite/27_io/basic_istringstream/cons/char/1.cc

>@@ -0,0 +1,85 @@

>+// Copyright (C) 2020 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/>.

>+

>+// C++20 29.8.2.2  basic_stringbuf constructors  [stringbuf.cons

>+

>+// { dg-options "-std=gnu++2a" }

>+// { dg-do run { target c++2a } }

>+// { dg-require-effective-target cxx11-abi }

>+

>+#include <sstream>

>+#include <string>

>+#include <testsuite_allocator.h>

>+#include <testsuite_hooks.h>

>+

>+void

>+test01()

>+{

>+  std::istringstream::allocator_type a;

>+  std::istringstream stm(std::ios_base::in, a);

>+}

>+

>+auto const cstr = "This is a test";

>+

>+void

>+test02()

>+{

>+  std::string s1(cstr);

>+  std::istringstream stm(std::move(s1));

>+  VERIFY( s1.empty() );

>+

>+  std::string s2(cstr);

>+  VERIFY( stm.str() == s2 );

>+}

>+

>+void

>+test03()

>+{

>+  using alloc_type = __gnu_test::tracker_allocator<char>;

>+  using str_type = std::basic_string<char, std::char_traits<char>, alloc_type>;

>+

>+  auto const mode = std::ios_base::in;

>+  str_type s1(cstr);

>+

>+  {

>+    std::istringstream::allocator_type a;

>+    std::istringstream sbuf(s1, mode, a);

>+    std::string s2(cstr);

>+    VERIFY( sbuf.str() == s2 );

>+  }

>+

>+  {

>+    std::istringstream sbuf(s1, mode);

>+    std::string s2(cstr);

>+    VERIFY( sbuf.str() == s2 );

>+  }

>+

>+  {

>+    std::istringstream sbuf(s1);

>+    std::string s2(cstr);

>+    VERIFY( sbuf.str() == s2 );

>+  }

>+}

>+

>+int

>+main()

>+{

>+  test01();

>+  test02();

>+  test03();

>+  return 0;

>+}

>diff --git a/libstdc++-v3/testsuite/27_io/basic_istringstream/cons/wchar_t/1.cc b/libstdc++-v3/testsuite/27_io/basic_istringstream/cons/wchar_t/1.cc

>new file mode 100644

>index 00000000000..26a3a86c46e

>--- /dev/null

>+++ b/libstdc++-v3/testsuite/27_io/basic_istringstream/cons/wchar_t/1.cc

>@@ -0,0 +1,85 @@

>+// Copyright (C) 2020 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/>.

>+

>+// C++20 29.8.2.2  basic_stringbuf constructors  [stringbuf.cons

>+

>+// { dg-options "-std=gnu++2a" }

>+// { dg-do run { target c++2a } }

>+// { dg-require-effective-target cxx11-abi }

>+

>+#include <sstream>

>+#include <string>

>+#include <testsuite_allocator.h>

>+#include <testsuite_hooks.h>

>+

>+void

>+test01()

>+{

>+  std::wistringstream::allocator_type a;

>+  std::wistringstream stm(std::ios_base::in, a);

>+}

>+

>+auto const cstr = L"This is a test";

>+

>+void

>+test02()

>+{

>+  std::wstring s1(cstr);

>+  std::wistringstream stm(std::move(s1));

>+  VERIFY( s1.empty() );

>+

>+  std::wstring s2(cstr);

>+  VERIFY( stm.str() == s2 );

>+}

>+

>+void

>+test03()

>+{

>+  using alloc_type = __gnu_test::tracker_allocator<wchar_t>;

>+  using str_type = std::basic_string<wchar_t, std::char_traits<wchar_t>, alloc_type>;

>+

>+  auto const mode = std::ios_base::in;

>+  str_type s1(cstr);

>+

>+  {

>+    std::wistringstream::allocator_type a;

>+    std::wistringstream sbuf(s1, mode, a);

>+    std::wstring s2(cstr);

>+    VERIFY( sbuf.str() == s2 );

>+  }

>+

>+  {

>+    std::wistringstream sbuf(s1, mode);

>+    std::wstring s2(cstr);

>+    VERIFY( sbuf.str() == s2 );

>+  }

>+

>+  {

>+    std::wistringstream sbuf(s1);

>+    std::wstring s2(cstr);

>+    VERIFY( sbuf.str() == s2 );

>+  }

>+}

>+

>+int

>+main()

>+{

>+  test01();

>+  test02();

>+  test03();

>+  return 0;

>+}

>diff --git a/libstdc++-v3/testsuite/27_io/basic_istringstream/view/char/1.cc b/libstdc++-v3/testsuite/27_io/basic_istringstream/view/char/1.cc

>new file mode 100644

>index 00000000000..091de5f7a79

>--- /dev/null

>+++ b/libstdc++-v3/testsuite/27_io/basic_istringstream/view/char/1.cc

>@@ -0,0 +1,35 @@

>+// Copyright (C) 2020 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/>.

>+

>+// 27.7.1.1  basic_stringbuf constructors  [lib.stringbuf.cons]

>+

>+// { dg-options "-std=gnu++2a" }

>+// { dg-do run { target c++2a } }

>+// { dg-require-effective-target cxx11-abi }

>+

>+#include <sstream>

>+#include <string_view>

>+#include <testsuite_hooks.h>

>+

>+int

>+main()

>+{

>+  std::string s("This is a test");

>+  std::istringstream stm(s);

>+  VERIFY( stm.view() == s );

>+  return 0;

>+}

>diff --git a/libstdc++-v3/testsuite/27_io/basic_istringstream/view/wchar_t/1.cc b/libstdc++-v3/testsuite/27_io/basic_istringstream/view/wchar_t/1.cc

>new file mode 100644

>index 00000000000..f6599643bd9

>--- /dev/null

>+++ b/libstdc++-v3/testsuite/27_io/basic_istringstream/view/wchar_t/1.cc

>@@ -0,0 +1,35 @@

>+// Copyright (C) 2020 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/>.

>+

>+// 27.7.1.1  basic_stringbuf constructors  [lib.stringbuf.cons]

>+

>+// { dg-options "-std=gnu++2a" }

>+// { dg-do run { target c++2a } }

>+// { dg-require-effective-target cxx11-abi }

>+

>+#include <sstream>

>+#include <string_view>

>+#include <testsuite_hooks.h>

>+

>+int

>+main()

>+{

>+  std::wstring s(L"This is a test");

>+  std::wistringstream stm(s);

>+  VERIFY( stm.view() == s );

>+  return 0;

>+}

>diff --git a/libstdc++-v3/testsuite/27_io/basic_ostringstream/cons/char/1.cc b/libstdc++-v3/testsuite/27_io/basic_ostringstream/cons/char/1.cc

>new file mode 100644

>index 00000000000..cba69f80931

>--- /dev/null

>+++ b/libstdc++-v3/testsuite/27_io/basic_ostringstream/cons/char/1.cc

>@@ -0,0 +1,85 @@

>+// Copyright (C) 2020 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/>.

>+

>+// C++20 29.8.2.2  basic_stringbuf constructors  [stringbuf.cons

>+

>+// { dg-options "-std=gnu++2a" }

>+// { dg-do run { target c++2a } }

>+// { dg-require-effective-target cxx11-abi }

>+

>+#include <sstream>

>+#include <string>

>+#include <testsuite_allocator.h>

>+#include <testsuite_hooks.h>

>+

>+void

>+test01()

>+{

>+  std::ostringstream::allocator_type a;

>+  std::ostringstream stm(std::ios_base::in, a);

>+}

>+

>+auto const cstr = "This is a test";

>+

>+void

>+test02()

>+{

>+  std::string s1(cstr);

>+  std::ostringstream stm(std::move(s1));

>+  VERIFY( s1.empty() );

>+

>+  std::string s2(cstr);

>+  VERIFY( stm.str() == s2 );

>+}

>+

>+void

>+test03()

>+{

>+  using alloc_type = __gnu_test::tracker_allocator<char>;

>+  using str_type = std::basic_string<char, std::char_traits<char>, alloc_type>;

>+

>+  auto const mode = std::ios_base::out;

>+  str_type s1(cstr);

>+

>+  {

>+    std::ostringstream::allocator_type a;

>+    std::ostringstream sbuf(s1, mode, a);

>+    std::string s2(cstr);

>+    VERIFY( sbuf.str() == s2 );

>+  }

>+

>+  {

>+    std::ostringstream sbuf(s1, mode);

>+    std::string s2(cstr);

>+    VERIFY( sbuf.str() == s2 );

>+  }

>+

>+  {

>+    std::ostringstream sbuf(s1);

>+    std::string s2(cstr);

>+    VERIFY( sbuf.str() == s2 );

>+  }

>+}

>+

>+int

>+main()

>+{

>+  test01();

>+  test02();

>+  test03();

>+  return 0;

>+}

>diff --git a/libstdc++-v3/testsuite/27_io/basic_ostringstream/cons/wchar_t/1.cc b/libstdc++-v3/testsuite/27_io/basic_ostringstream/cons/wchar_t/1.cc

>new file mode 100644

>index 00000000000..9021186d2c8

>--- /dev/null

>+++ b/libstdc++-v3/testsuite/27_io/basic_ostringstream/cons/wchar_t/1.cc

>@@ -0,0 +1,85 @@

>+// Copyright (C) 2020 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/>.

>+

>+// C++20 29.8.2.2  basic_stringbuf constructors  [stringbuf.cons

>+

>+// { dg-options "-std=gnu++2a" }

>+// { dg-do run { target c++2a } }

>+// { dg-require-effective-target cxx11-abi }

>+

>+#include <sstream>

>+#include <string>

>+#include <testsuite_allocator.h>

>+#include <testsuite_hooks.h>

>+

>+void

>+test01()

>+{

>+  std::wostringstream::allocator_type a;

>+  std::wostringstream stm(std::ios_base::out, a);

>+}

>+

>+auto const cstr = L"This is a test";

>+

>+void

>+test02()

>+{

>+  std::wstring s1(cstr);

>+  std::wostringstream stm(std::move(s1));

>+  VERIFY( s1.empty() );

>+

>+  std::wstring s2(cstr);

>+  VERIFY( stm.str() == s2 );

>+}

>+

>+void

>+test03()

>+{

>+  using alloc_type = __gnu_test::tracker_allocator<wchar_t>;

>+  using str_type = std::basic_string<wchar_t, std::char_traits<wchar_t>, alloc_type>;

>+

>+  auto const mode = std::ios_base::out;

>+  str_type s1(cstr);

>+

>+  {

>+    std::wostringstream::allocator_type a;

>+    std::wostringstream sbuf(s1, mode, a);

>+    std::wstring s2(cstr);

>+    VERIFY( sbuf.str() == s2 );

>+  }

>+

>+  {

>+    std::wostringstream sbuf(s1, mode);

>+    std::wstring s2(cstr);

>+    VERIFY( sbuf.str() == s2 );

>+  }

>+

>+  {

>+    std::wostringstream sbuf(s1);

>+    std::wstring s2(cstr);

>+    VERIFY( sbuf.str() == s2 );

>+  }

>+}

>+

>+int

>+main()

>+{

>+  test01();

>+  test02();

>+  test03();

>+  return 0;

>+}

>diff --git a/libstdc++-v3/testsuite/27_io/basic_ostringstream/view/char/1.cc b/libstdc++-v3/testsuite/27_io/basic_ostringstream/view/char/1.cc

>new file mode 100644

>index 00000000000..a366363abb5

>--- /dev/null

>+++ b/libstdc++-v3/testsuite/27_io/basic_ostringstream/view/char/1.cc

>@@ -0,0 +1,35 @@

>+// Copyright (C) 2020 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/>.

>+

>+// 27.7.1.1  basic_stringbuf constructors  [lib.stringbuf.cons]

>+

>+// { dg-options "-std=gnu++2a" }

>+// { dg-do run { target c++2a } }

>+// { dg-require-effective-target cxx11-abi }

>+

>+#include <sstream>

>+#include <string_view>

>+#include <testsuite_hooks.h>

>+

>+int

>+main()

>+{

>+  std::string s("This is a test");

>+  std::ostringstream stm(s);

>+  VERIFY( stm.view() == s );

>+  return 0;

>+}

>diff --git a/libstdc++-v3/testsuite/27_io/basic_ostringstream/view/wchar_t/1.cc b/libstdc++-v3/testsuite/27_io/basic_ostringstream/view/wchar_t/1.cc

>new file mode 100644

>index 00000000000..1ebf7c505e3

>--- /dev/null

>+++ b/libstdc++-v3/testsuite/27_io/basic_ostringstream/view/wchar_t/1.cc

>@@ -0,0 +1,35 @@

>+// Copyright (C) 2020 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/>.

>+

>+// 27.7.1.1  basic_stringbuf constructors  [lib.stringbuf.cons]

>+

>+// { dg-options "-std=gnu++2a" }

>+// { dg-do run { target c++2a } }

>+// { dg-require-effective-target cxx11-abi }

>+

>+#include <sstream>

>+#include <string_view>

>+#include <testsuite_hooks.h>

>+

>+int

>+main()

>+{

>+  std::wstring s(L"This is a test");

>+  std::wostringstream stm(s);

>+  VERIFY( stm.view() == s );

>+  return 0;

>+}

>diff --git a/libstdc++-v3/testsuite/27_io/basic_stringbuf/cons/char/2.cc b/libstdc++-v3/testsuite/27_io/basic_stringbuf/cons/char/2.cc

>new file mode 100644

>index 00000000000..ce669358c85

>--- /dev/null

>+++ b/libstdc++-v3/testsuite/27_io/basic_stringbuf/cons/char/2.cc

>@@ -0,0 +1,121 @@

>+// Copyright (C) 2020 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/>.

>+

>+// 27.7.1.1  basic_stringbuf constructors  [lib.stringbuf.cons]

>+

>+// { dg-options "-std=gnu++2a" }

>+// { dg-do run { target c++2a } }

>+// { dg-require-effective-target cxx11-abi }

>+

>+#include <sstream>

>+#include <string>

>+#include <testsuite_allocator.h>

>+#include <testsuite_hooks.h>

>+

>+void

>+test01()

>+{

>+  {

>+    using alloc_type = __gnu_test::uneq_allocator<char>;

>+    using sbuf_t = std::basic_stringbuf<char, std::char_traits<char>,

>+						alloc_type>;

>+

>+    alloc_type aa;

>+    sbuf_t sbuf1(aa);

>+    VERIFY( aa == sbuf1.get_allocator() );

>+

>+    alloc_type aaa(42);

>+    sbuf_t sbuf2(aaa);

>+    VERIFY( aaa == sbuf2.get_allocator() );

>+

>+    VERIFY( sbuf1.get_allocator() != sbuf2.get_allocator() );

>+  }

>+

>+  std::stringbuf::allocator_type a;

>+  {

>+    std::stringbuf sbuf(std::ios_base::in, a);

>+  }

>+

>+  {

>+    std::stringbuf sbuf(a);

>+  }

>+}

>+

>+auto const cstr = "This is a test";

>+

>+void

>+test02()

>+{

>+  std::string s1(cstr);

>+  std::stringbuf sbuf(std::move(s1));

>+  VERIFY( s1.empty() );

>+

>+  std::string s2(cstr);

>+  VERIFY( sbuf.str() == s2 );

>+}

>+

>+void

>+test03()

>+{

>+  using alloc_type = __gnu_test::tracker_allocator<char>;

>+  using str_type = std::basic_string<char, std::char_traits<char>, alloc_type>;

>+

>+  auto const mode = std::ios_base::in | std::ios_base::out;

>+  str_type s1(cstr);

>+

>+  {

>+    std::stringbuf::allocator_type a;

>+    std::stringbuf sbuf(s1, mode, a);

>+    std::string s2(cstr);

>+    VERIFY( sbuf.str() == s2 );

>+  }

>+

>+  {

>+    std::stringbuf sbuf(s1, mode);

>+    std::string s2(cstr);

>+    VERIFY( sbuf.str() == s2 );

>+  }

>+

>+  {

>+    std::stringbuf sbuf(s1);

>+    std::string s2(cstr);

>+    VERIFY( sbuf.str() == s2 );

>+  }

>+}

>+

>+void

>+test04()

>+{

>+  std::stringbuf sbuf1(cstr);

>+

>+  std::stringbuf::allocator_type a;

>+  std::stringbuf sbuf2(std::move(sbuf1), a);

>+  VERIFY( sbuf1.str().empty() );

>+

>+  std::string s(cstr);

>+  VERIFY( sbuf2.str() == s );

>+}

>+

>+int

>+main()

>+{

>+  test01();

>+  test02();

>+  test03();

>+  test04();

>+  return 0;

>+}

>diff --git a/libstdc++-v3/testsuite/27_io/basic_stringbuf/cons/wchar_t/2.cc b/libstdc++-v3/testsuite/27_io/basic_stringbuf/cons/wchar_t/2.cc

>new file mode 100644

>index 00000000000..e05acc42165

>--- /dev/null

>+++ b/libstdc++-v3/testsuite/27_io/basic_stringbuf/cons/wchar_t/2.cc

>@@ -0,0 +1,105 @@

>+// Copyright (C) 2020 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/>.

>+

>+// 27.7.1.1  basic_stringbuf constructors  [lib.stringbuf.cons]

>+

>+// { dg-options "-std=gnu++2a" }

>+// { dg-do run { target c++2a } }

>+// { dg-require-effective-target cxx11-abi }

>+

>+#include <sstream>

>+#include <string>

>+#include <testsuite_allocator.h>

>+#include <testsuite_hooks.h>

>+

>+void

>+test01()

>+{

>+  std::wstringbuf::allocator_type a;

>+  {

>+    std::wstringbuf sbuf(std::ios_base::in, a);

>+  }

>+

>+  {

>+    std::wstringbuf sbuf(a);

>+  }

>+}

>+

>+auto const cstr = L"This is a test";

>+

>+void

>+test02()

>+{

>+  std::wstring s1(cstr);

>+  std::wstringbuf sbuf(std::move(s1));

>+  VERIFY( s1.empty() );

>+

>+  std::wstring s2(cstr);

>+  VERIFY( sbuf.str() == s2 );

>+}

>+

>+void

>+test03()

>+{

>+  using alloc_type = __gnu_test::tracker_allocator<wchar_t>;

>+  using str_type = std::basic_string<wchar_t, std::char_traits<wchar_t>, alloc_type>;

>+

>+  auto const mode = std::ios_base::in | std::ios_base::out;

>+  str_type s1(cstr);

>+

>+  {

>+    std::wstringbuf::allocator_type a;

>+    std::wstringbuf sbuf(s1, mode, a);

>+    std::wstring s2(cstr);

>+    VERIFY( sbuf.str() == s2 );

>+  }

>+

>+  {

>+    std::wstringbuf sbuf(s1, mode);

>+    std::wstring s2(cstr);

>+    VERIFY( sbuf.str() == s2 );

>+  }

>+

>+  {

>+    std::wstringbuf sbuf(s1);

>+    std::wstring s2(cstr);

>+    VERIFY( sbuf.str() == s2 );

>+  }

>+}

>+

>+void

>+test04()

>+{

>+  std::wstringbuf sbuf1(cstr);

>+

>+  std::wstringbuf::allocator_type a;

>+  std::wstringbuf sbuf2(std::move(sbuf1), a);

>+  VERIFY( sbuf1.str().empty() );

>+

>+  std::wstring s(cstr);

>+  VERIFY( sbuf2.str() == s );

>+}

>+

>+int

>+main()

>+{

>+  test01();

>+  test02();

>+  test03();

>+  test04();

>+  return 0;

>+}

>diff --git a/libstdc++-v3/testsuite/27_io/basic_stringbuf/view/char/1.cc b/libstdc++-v3/testsuite/27_io/basic_stringbuf/view/char/1.cc

>new file mode 100644

>index 00000000000..8f8c62daa21

>--- /dev/null

>+++ b/libstdc++-v3/testsuite/27_io/basic_stringbuf/view/char/1.cc

>@@ -0,0 +1,35 @@

>+// Copyright (C) 2020 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/>.

>+

>+// 27.7.1.1  basic_stringbuf constructors  [lib.stringbuf.cons]

>+

>+// { dg-options "-std=gnu++2a" }

>+// { dg-do run { target c++2a } }

>+// { dg-require-effective-target cxx11-abi }

>+

>+#include <sstream>

>+#include <string_view>

>+#include <testsuite_hooks.h>

>+

>+int

>+main()

>+{

>+  std::string s("This is a test");

>+  std::stringbuf sbuf(s);

>+  VERIFY( sbuf.view() == s );

>+  return 0;

>+}

>diff --git a/libstdc++-v3/testsuite/27_io/basic_stringbuf/view/wchar_t/1.cc b/libstdc++-v3/testsuite/27_io/basic_stringbuf/view/wchar_t/1.cc

>new file mode 100644

>index 00000000000..0d23d7d8e66

>--- /dev/null

>+++ b/libstdc++-v3/testsuite/27_io/basic_stringbuf/view/wchar_t/1.cc

>@@ -0,0 +1,35 @@

>+// Copyright (C) 2020 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/>.

>+

>+// 27.7.1.1  basic_stringbuf constructors  [lib.stringbuf.cons]

>+

>+// { dg-options "-std=gnu++2a" }

>+// { dg-do run { target c++2a } }

>+// { dg-require-effective-target cxx11-abi }

>+

>+#include <sstream>

>+#include <string_view>

>+#include <testsuite_hooks.h>

>+

>+int

>+main()

>+{

>+  std::wstring s(L"This is a test");

>+  std::wstringbuf sbuf(s);

>+  VERIFY( sbuf.view() == s );

>+  return 0;

>+}

>diff --git a/libstdc++-v3/testsuite/27_io/basic_stringstream/cons/char/1.cc b/libstdc++-v3/testsuite/27_io/basic_stringstream/cons/char/1.cc

>new file mode 100644

>index 00000000000..83a3374b3cd

>--- /dev/null

>+++ b/libstdc++-v3/testsuite/27_io/basic_stringstream/cons/char/1.cc

>@@ -0,0 +1,85 @@

>+// Copyright (C) 2020 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/>.

>+

>+// C++20 29.8.2.2  basic_stringbuf constructors  [stringbuf.cons

>+

>+// { dg-options "-std=gnu++2a" }

>+// { dg-do run { target c++2a } }

>+// { dg-require-effective-target cxx11-abi }

>+

>+#include <sstream>

>+#include <string>

>+#include <testsuite_allocator.h>

>+#include <testsuite_hooks.h>

>+

>+void

>+test01()

>+{

>+  std::stringstream::allocator_type a;

>+  std::stringstream stm(std::ios_base::in, a);

>+}

>+

>+auto const cstr = "This is a test";

>+

>+void

>+test02()

>+{

>+  std::string s1(cstr);

>+  std::stringstream stm(std::move(s1));

>+  VERIFY( s1.empty() );

>+

>+  std::string s2(cstr);

>+  VERIFY( stm.str() == s2 );

>+}

>+

>+void

>+test03()

>+{

>+  using alloc_type = __gnu_test::tracker_allocator<char>;

>+  using str_type = std::basic_string<char, std::char_traits<char>, alloc_type>;

>+

>+  auto const mode = std::ios_base::in | std::ios_base::out;

>+  str_type s1(cstr);

>+

>+  {

>+    std::stringstream::allocator_type a;

>+    std::stringstream sbuf(s1, mode, a);

>+    std::string s2(cstr);

>+    VERIFY( sbuf.str() == s2 );

>+  }

>+

>+  {

>+    std::stringstream sbuf(s1, mode);

>+    std::string s2(cstr);

>+    VERIFY( sbuf.str() == s2 );

>+  }

>+

>+  {

>+    std::stringstream sbuf(s1);

>+    std::string s2(cstr);

>+    VERIFY( sbuf.str() == s2 );

>+  }

>+}

>+

>+int

>+main()

>+{

>+  test01();

>+  test02();

>+  test03();

>+  return 0;

>+}

>diff --git a/libstdc++-v3/testsuite/27_io/basic_stringstream/cons/wchar_t/1.cc b/libstdc++-v3/testsuite/27_io/basic_stringstream/cons/wchar_t/1.cc

>new file mode 100644

>index 00000000000..26a3a86c46e

>--- /dev/null

>+++ b/libstdc++-v3/testsuite/27_io/basic_stringstream/cons/wchar_t/1.cc

>@@ -0,0 +1,85 @@

>+// Copyright (C) 2020 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/>.

>+

>+// C++20 29.8.2.2  basic_stringbuf constructors  [stringbuf.cons

>+

>+// { dg-options "-std=gnu++2a" }

>+// { dg-do run { target c++2a } }

>+// { dg-require-effective-target cxx11-abi }

>+

>+#include <sstream>

>+#include <string>

>+#include <testsuite_allocator.h>

>+#include <testsuite_hooks.h>

>+

>+void

>+test01()

>+{

>+  std::wistringstream::allocator_type a;

>+  std::wistringstream stm(std::ios_base::in, a);

>+}

>+

>+auto const cstr = L"This is a test";

>+

>+void

>+test02()

>+{

>+  std::wstring s1(cstr);

>+  std::wistringstream stm(std::move(s1));

>+  VERIFY( s1.empty() );

>+

>+  std::wstring s2(cstr);

>+  VERIFY( stm.str() == s2 );

>+}

>+

>+void

>+test03()

>+{

>+  using alloc_type = __gnu_test::tracker_allocator<wchar_t>;

>+  using str_type = std::basic_string<wchar_t, std::char_traits<wchar_t>, alloc_type>;

>+

>+  auto const mode = std::ios_base::in;

>+  str_type s1(cstr);

>+

>+  {

>+    std::wistringstream::allocator_type a;

>+    std::wistringstream sbuf(s1, mode, a);

>+    std::wstring s2(cstr);

>+    VERIFY( sbuf.str() == s2 );

>+  }

>+

>+  {

>+    std::wistringstream sbuf(s1, mode);

>+    std::wstring s2(cstr);

>+    VERIFY( sbuf.str() == s2 );

>+  }

>+

>+  {

>+    std::wistringstream sbuf(s1);

>+    std::wstring s2(cstr);

>+    VERIFY( sbuf.str() == s2 );

>+  }

>+}

>+

>+int

>+main()

>+{

>+  test01();

>+  test02();

>+  test03();

>+  return 0;

>+}

>diff --git a/libstdc++-v3/testsuite/27_io/basic_stringstream/view/char/1.cc b/libstdc++-v3/testsuite/27_io/basic_stringstream/view/char/1.cc

>new file mode 100644

>index 00000000000..f47035cf148

>--- /dev/null

>+++ b/libstdc++-v3/testsuite/27_io/basic_stringstream/view/char/1.cc

>@@ -0,0 +1,35 @@

>+// Copyright (C) 2020 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/>.

>+

>+// 27.7.1.1  basic_stringbuf constructors  [lib.stringbuf.cons]

>+

>+// { dg-options "-std=gnu++2a" }

>+// { dg-do run { target c++2a } }

>+// { dg-require-effective-target cxx11-abi }

>+

>+#include <sstream>

>+#include <string_view>

>+#include <testsuite_hooks.h>

>+

>+int

>+main()

>+{

>+  std::string s("This is a test");

>+  std::stringstream stm(s);

>+  VERIFY( stm.view() == s );

>+  return 0;

>+}

>diff --git a/libstdc++-v3/testsuite/27_io/basic_stringstream/view/wchar_t/1.cc b/libstdc++-v3/testsuite/27_io/basic_stringstream/view/wchar_t/1.cc

>new file mode 100644

>index 00000000000..d707cfed243

>--- /dev/null

>+++ b/libstdc++-v3/testsuite/27_io/basic_stringstream/view/wchar_t/1.cc

>@@ -0,0 +1,35 @@

>+// Copyright (C) 2020 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/>.

>+

>+// 27.7.1.1  basic_stringbuf constructors  [lib.stringbuf.cons]

>+

>+// { dg-options "-std=gnu++2a" }

>+// { dg-do run { target c++2a } }

>+// { dg-require-effective-target cxx11-abi }

>+

>+#include <sstream>

>+#include <string_view>

>+#include <testsuite_hooks.h>

>+

>+int

>+main()

>+{

>+  std::wstring s(L"This is a test");

>+  std::wstringstream stm(s);

>+  VERIFY( stm.view() == s );

>+  return 0;

>+}

>-- 

>2.26.2

>
H.J. Lu via Gcc-patches Oct. 28, 2020, 11:59 p.m. | #2
On 26/10/20 21:09 +0000, Jonathan Wakely wrote:
>On 26/10/20 13:47 -0700, Thomas Rodgers wrote:

>>From: Thomas Rodgers <trodgers@redhat.com>

>>

>>New ctors and ::view() accessor for -

>> * basic_stingbuf

>> * basic_istringstream

>> * basic_ostringstream

>> * basic_stringstreamm

>>

>>New ::get_allocator() accessor for basic_stringbuf.

>>

>>libstdc++-v3/ChangeLog:

>>	* acinclude.m4 (glibcxx_SUBDIRS): Add src/c++20.

>>       * config/abi/pre/gnu.ver: Update GLIBCXX_3.4.29 for the addition of -

>>	basic_stringbuf::basic_stringbuf(allocator const&),

>>	basic_stringbuf::basic_stringbuf(openmode, allocator const&),

>>	basic_stringbuf::basic_stringbuf(basic_string&&, openmode),

>>	basic_stringbuf::basic_stringbuf(basic_stringbuf&&, allocator const&),

>>	basic_stringbuf::get_allocator(),

>>	basic_stringbuf::view(),

>>	basic_istringstream::basic_istringstream(basic_string&&, openmode),

>>	basic_istringstream::basic_istringstream(openmode, allocator const&),

>>	basic_istringstream::view(),

>>	basic_ostringstream::basic_ostringstream(basic_string&&, openmode),

>>	basic_ostringstream::basic_ostringstream(openmode, allocator const&),

>>	basic_ostringstream::view(),

>>	basic_stringstream::basic_stringstream(basic_string&&, openmode),

>>	basic_stringstream::basic_stringstream(openmode, allocator const&),

>>	basic_stringstream::view().

>

>As discussed on IRC< please don't name every one of these functions

>for the linker script changes, it's just redundant noise. They're

>already listed below in the include/std/sstream changes.

>

>Look at past changelog entries for the gnu.ver file.

>

>>	* configure: Regenerate.

>>	* include/std/sstream:

>>	(basic_stringbuf::basic_stringbuf(allocator const&)): New constructor.

>>	(basic_stringbuf::basic_stringbuf(openmode, allocator const&)): Likewise.

>>	(basic_stringbuf::basic_stringbuf(basic_string&&, openmode)): Likewise.

>>	(basic_stringbuf::basic_stringbuf(basic_stringbuf&&, allocator const&)): Likewise.

>

>New line before the Likewise.

>

>

>There are a few formatting changes mentioned below. OK for trunk with

>those changes. Thanks. Go ahead and commit the <syncstream> patch

>after this one too.


The patch that was committed broke the linker script. The attached
patch restores the piece that got lost, and removes the duplicate
patterns added for the new symbols. Pushed to trunk.

This fixes all the failures related to exception_ptr. I'm still seeing
four new failures which weren't there before:

FAIL: 24_iterators/istream_iterator/sentinel.cc execution test
FAIL: 24_iterators/istreambuf_iterator/sentinel.cc execution test
FAIL: 27_io/basic_istream/extractors_character/char/lwg2499.cc execution test
FAIL: std/ranges/istream_view.cc execution test

I'm not sure what's happening there. It looks like some symbols I
added recently are not present now. I'm investigating.

Also, it looks like the get_allocator() members of the streams are not
exported (only basic_stringbuf::get_allocator() is).
commit f4f9364d2074e027490c1b08956ac1cbd9617575
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Wed Oct 28 23:10:21 2020

    libstdc++: Fix linker script
    
    libstdc++-v3/ChangeLog:
    
            * config/abi/pre/gnu.ver (GLIBCXX_3.4.29): Remove duplicate
            patterns.
            (CXXABI_1.3.13): Restore missing piece.

diff --git a/libstdc++-v3/config/abi/pre/gnu.ver b/libstdc++-v3/config/abi/pre/gnu.ver
index 2648c813616..80994b203df 100644
--- a/libstdc++-v3/config/abi/pre/gnu.ver
+++ b/libstdc++-v3/config/abi/pre/gnu.ver
@@ -2335,51 +2335,6 @@ GLIBCXX_3.4.29 {
     # std::__throw_bad_array_new_length()
     _ZSt28__throw_bad_array_new_lengthv;
 
-    # basic_stringbuf::basic_stringbuf(allocator const&)
-    _ZNSt7__cxx1115basic_stringbufI[cw]St11char_traitsI[cw]ESaI[cw]EEC1ERKS3_;
-
-    # basic_stringbuf::basic_stringbuf(ios_base::openmode, allocator const&)
-    _ZNSt7__cxx1115basic_stringbufI[cw]St11char_traitsI[cw]ESaI[cw]EEC1ESt13_Ios_OpenmodeRKS3;
-
-    # basic_stringbuf::basic_stringbuf(basic_string&&, ios_base::openmode)
-    _ZNSt7__cxx1115basic_stringbufI[cw]St11char_traitsI[cw]ESaI[cw]EEC1EONS_12basic_stringI[cw]S2_S3_EESt13_Ios_Openmode;
-
-    # basic_stringbuf::basic_stringbuf(basic_stringbuf&&, allocator const&)
-    _ZNSt7__cxx1115basic_stringbufI[cw]St11char_traitsI[cw]ESaIcEEC1EOS4_RKS3_;
-
-    # basic_stringbuf::get_allocator()
-    _ZNKSt7__cxx1115basic_stringbufI[cw]St11char_traitsI[cw]ESaI[cw]EE13get_allocatorEv;
-
-    # basic_stringbuf::view()
-    _ZNKSt7__cxx1115basic_stringbufI[cw]St11char_traitsI[cw]ESaI[cw]EE4viewEv;
-
-    # basic_istringstream::basic_istringstream(basic_string&&, ios_base::openmode)
-    _ZNSt7__cxx1119basic_istringstreamI[cw]St11char_traitsI[cw]ESaIcEEC1EONS_12basic_stringI[cw]S2_S3_EESt13_Ios_Openmode;
-
-    # basic_istringstream::basic_istringstream(ios_base::openmode, allocator const&)
-    _ZNSt7__cxx1119basic_istringstreamI[cw]St11char_traitsI[cw]ESaI[cw]EEC1ESt13_Ios_OpenmodeRKS3_;
-
-    # basic_istringstream::view()
-    _ZNKSt7__cxx1119basic_istringstreamI[cw]St11char_traitsI[cw]ESaI[cw]EE4viewEv;
-
-    # basic_ostringstream::basic_ostringstream(basic_string&&, ios_base::openmode)
-    _ZNSt7__cxx1119basic_ostringstreamI[cw]St11char_traitsI[cw]ESaIcEEC1EONS_12basic_stringI[cw]S2_S3_EESt13_Ios_Openmode;
-
-    # basic_ostringstream::basic_ostringstream(ios_base::openmode, allocator const&)
-    _ZNSt7__cxx1119basic_ostringstreamI[cw]St11char_traitsI[cw]ESaIcEEC1ESt13_Ios_OpenmodeRKS3_;
-
-    # basic_ostringstream::view()
-    _ZNKSt7__cxx1119basic_ostringstreamI[cw]St11char_traitsI[cw]ESaI[cw]EE4viewEv;
-
-    # basic_stringstream::basic_stringstream(basic_string&&, ios_base::openmode)
-    _ZNSt7__cxx1119basic_stringstreamI[cw]St11char_traitsI[cw]ESaIcEEC1EONS_12basic_stringI[cw]S2_S3_EESt13_Ios_Openmode;
-
-    # basic_stringstream::basic_stringstream(ios_base::openmode, allocator const&)
-    _ZNSt7__cxx1119basic_stringstreamI[cw]St11char_traitsI[cw]ESaIcEEC1ESt13_Ios_OpenmodeRKS3_;
-
-    # basic_stringstream::view()
-    _ZNKSt7__cxx1119basic_stringstreamI[cw]St11char_traitsI[cw]ESaI[cw]EE4viewEv;
-
     # basic_stringbuf::basic_stringbuf(allocator const&)
     _ZNSt7__cxx1115basic_stringbufI[cw]St11char_traitsI[cw]ESaI[cw]EEC[12]ERKS3_;
 
@@ -2398,13 +2353,13 @@ GLIBCXX_3.4.29 {
     # basic_stringbuf::view()
     _ZNKSt7__cxx1115basic_stringbufI[cw]St11char_traitsI[cw]ESaI[cw]EE4viewEv;
 
-    # basic_istringstream::basic_istringstream(basic_string&&, ios_base::openmode)
+    # basic_[io]stringstream::basic_[io]stringstream(basic_string&&, ios_base::openmode)
     _ZNSt7__cxx1119basic_[io]stringstreamI[cw]St11char_traitsI[cw]ESaI[cw]EEC[12]EONS_12basic_stringI[cw]S2_S3_EESt13_Ios_Openmode;
 
     # basic_[io]stringstream::basic_[io]stringstream(ios_base::openmode, allocator const&)
     _ZNSt7__cxx1119basic_[io]stringstreamI[cw]St11char_traitsI[cw]ESaI[cw]EEC[12]ESt13_Ios_OpenmodeRKS3_;
 
-    # basic_istringstream::view()
+    # basic_[io]stringstream::view()
     _ZNKSt7__cxx1119basic_[io]stringstreamI[cw]St11char_traitsI[cw]ESaI[cw]EE4viewEv;
 
     # basic_stringstream::basic_stringstream(basic_string&&, ios_base::openmode)
@@ -2716,6 +2671,15 @@ CXXABI_1.3.12 {
 
 } CXXABI_1.3.11;
 
+CXXABI_1.3.13 {
+
+    # std::exception_ptr::_M_addref()
+    _ZNSt15__exception_ptr13exception_ptr9_M_addrefEv;
+    # std::exception_ptr::_M_release()
+    _ZNSt15__exception_ptr13exception_ptr10_M_releaseEv;
+
+} CXXABI_1.3.12;
+
 # Symbols in the support library (libsupc++) supporting transactional memory.
 CXXABI_TM_1 {
H.J. Lu via Gcc-patches Oct. 29, 2020, 1:30 a.m. | #3
On 28/10/20 23:59 +0000, Jonathan Wakely wrote:
>On 26/10/20 21:09 +0000, Jonathan Wakely wrote:

>>On 26/10/20 13:47 -0700, Thomas Rodgers wrote:

>>>From: Thomas Rodgers <trodgers@redhat.com>

>>>

>>>New ctors and ::view() accessor for -

>>>* basic_stingbuf

>>>* basic_istringstream

>>>* basic_ostringstream

>>>* basic_stringstreamm

>>>

>>>New ::get_allocator() accessor for basic_stringbuf.

>>>

>>>libstdc++-v3/ChangeLog:

>>>	* acinclude.m4 (glibcxx_SUBDIRS): Add src/c++20.

>>>      * config/abi/pre/gnu.ver: Update GLIBCXX_3.4.29 for the addition of -

>>>	basic_stringbuf::basic_stringbuf(allocator const&),

>>>	basic_stringbuf::basic_stringbuf(openmode, allocator const&),

>>>	basic_stringbuf::basic_stringbuf(basic_string&&, openmode),

>>>	basic_stringbuf::basic_stringbuf(basic_stringbuf&&, allocator const&),

>>>	basic_stringbuf::get_allocator(),

>>>	basic_stringbuf::view(),

>>>	basic_istringstream::basic_istringstream(basic_string&&, openmode),

>>>	basic_istringstream::basic_istringstream(openmode, allocator const&),

>>>	basic_istringstream::view(),

>>>	basic_ostringstream::basic_ostringstream(basic_string&&, openmode),

>>>	basic_ostringstream::basic_ostringstream(openmode, allocator const&),

>>>	basic_ostringstream::view(),

>>>	basic_stringstream::basic_stringstream(basic_string&&, openmode),

>>>	basic_stringstream::basic_stringstream(openmode, allocator const&),

>>>	basic_stringstream::view().

>>

>>As discussed on IRC< please don't name every one of these functions

>>for the linker script changes, it's just redundant noise. They're

>>already listed below in the include/std/sstream changes.

>>

>>Look at past changelog entries for the gnu.ver file.

>>

>>>	* configure: Regenerate.

>>>	* include/std/sstream:

>>>	(basic_stringbuf::basic_stringbuf(allocator const&)): New constructor.

>>>	(basic_stringbuf::basic_stringbuf(openmode, allocator const&)): Likewise.

>>>	(basic_stringbuf::basic_stringbuf(basic_string&&, openmode)): Likewise.

>>>	(basic_stringbuf::basic_stringbuf(basic_stringbuf&&, allocator const&)): Likewise.

>>

>>New line before the Likewise.

>>

>>

>>There are a few formatting changes mentioned below. OK for trunk with

>>those changes. Thanks. Go ahead and commit the <syncstream> patch

>>after this one too.

>

>The patch that was committed broke the linker script. The attached

>patch restores the piece that got lost, and removes the duplicate

>patterns added for the new symbols. Pushed to trunk.

>

>This fixes all the failures related to exception_ptr. I'm still seeing

>four new failures which weren't there before:

>

>FAIL: 24_iterators/istream_iterator/sentinel.cc execution test

>FAIL: 24_iterators/istreambuf_iterator/sentinel.cc execution test

>FAIL: 27_io/basic_istream/extractors_character/char/lwg2499.cc execution test

>FAIL: std/ranges/istream_view.cc execution test

>

>I'm not sure what's happening there. It looks like some symbols I

>added recently are not present now. I'm investigating.


The attached patch fixes the failing tests. Not fully tested, but
pushed to trunk.





>Also, it looks like the get_allocator() members of the streams are not

>exported (only basic_stringbuf::get_allocator() is).

>

>


>commit f4f9364d2074e027490c1b08956ac1cbd9617575

>Author: Jonathan Wakely <jwakely@redhat.com>

>Date:   Wed Oct 28 23:10:21 2020

>

>    libstdc++: Fix linker script

>    

>    libstdc++-v3/ChangeLog:

>    

>            * config/abi/pre/gnu.ver (GLIBCXX_3.4.29): Remove duplicate

>            patterns.

>            (CXXABI_1.3.13): Restore missing piece.

>

>diff --git a/libstdc++-v3/config/abi/pre/gnu.ver b/libstdc++-v3/config/abi/pre/gnu.ver

>index 2648c813616..80994b203df 100644

>--- a/libstdc++-v3/config/abi/pre/gnu.ver

>+++ b/libstdc++-v3/config/abi/pre/gnu.ver

>@@ -2335,51 +2335,6 @@ GLIBCXX_3.4.29 {

>     # std::__throw_bad_array_new_length()

>     _ZSt28__throw_bad_array_new_lengthv;

> 

>-    # basic_stringbuf::basic_stringbuf(allocator const&)

>-    _ZNSt7__cxx1115basic_stringbufI[cw]St11char_traitsI[cw]ESaI[cw]EEC1ERKS3_;

>-

>-    # basic_stringbuf::basic_stringbuf(ios_base::openmode, allocator const&)

>-    _ZNSt7__cxx1115basic_stringbufI[cw]St11char_traitsI[cw]ESaI[cw]EEC1ESt13_Ios_OpenmodeRKS3;

>-

>-    # basic_stringbuf::basic_stringbuf(basic_string&&, ios_base::openmode)

>-    _ZNSt7__cxx1115basic_stringbufI[cw]St11char_traitsI[cw]ESaI[cw]EEC1EONS_12basic_stringI[cw]S2_S3_EESt13_Ios_Openmode;

>-

>-    # basic_stringbuf::basic_stringbuf(basic_stringbuf&&, allocator const&)

>-    _ZNSt7__cxx1115basic_stringbufI[cw]St11char_traitsI[cw]ESaIcEEC1EOS4_RKS3_;

>-

>-    # basic_stringbuf::get_allocator()

>-    _ZNKSt7__cxx1115basic_stringbufI[cw]St11char_traitsI[cw]ESaI[cw]EE13get_allocatorEv;

>-

>-    # basic_stringbuf::view()

>-    _ZNKSt7__cxx1115basic_stringbufI[cw]St11char_traitsI[cw]ESaI[cw]EE4viewEv;

>-

>-    # basic_istringstream::basic_istringstream(basic_string&&, ios_base::openmode)

>-    _ZNSt7__cxx1119basic_istringstreamI[cw]St11char_traitsI[cw]ESaIcEEC1EONS_12basic_stringI[cw]S2_S3_EESt13_Ios_Openmode;

>-

>-    # basic_istringstream::basic_istringstream(ios_base::openmode, allocator const&)

>-    _ZNSt7__cxx1119basic_istringstreamI[cw]St11char_traitsI[cw]ESaI[cw]EEC1ESt13_Ios_OpenmodeRKS3_;

>-

>-    # basic_istringstream::view()

>-    _ZNKSt7__cxx1119basic_istringstreamI[cw]St11char_traitsI[cw]ESaI[cw]EE4viewEv;

>-

>-    # basic_ostringstream::basic_ostringstream(basic_string&&, ios_base::openmode)

>-    _ZNSt7__cxx1119basic_ostringstreamI[cw]St11char_traitsI[cw]ESaIcEEC1EONS_12basic_stringI[cw]S2_S3_EESt13_Ios_Openmode;

>-

>-    # basic_ostringstream::basic_ostringstream(ios_base::openmode, allocator const&)

>-    _ZNSt7__cxx1119basic_ostringstreamI[cw]St11char_traitsI[cw]ESaIcEEC1ESt13_Ios_OpenmodeRKS3_;

>-

>-    # basic_ostringstream::view()

>-    _ZNKSt7__cxx1119basic_ostringstreamI[cw]St11char_traitsI[cw]ESaI[cw]EE4viewEv;

>-

>-    # basic_stringstream::basic_stringstream(basic_string&&, ios_base::openmode)

>-    _ZNSt7__cxx1119basic_stringstreamI[cw]St11char_traitsI[cw]ESaIcEEC1EONS_12basic_stringI[cw]S2_S3_EESt13_Ios_Openmode;

>-

>-    # basic_stringstream::basic_stringstream(ios_base::openmode, allocator const&)

>-    _ZNSt7__cxx1119basic_stringstreamI[cw]St11char_traitsI[cw]ESaIcEEC1ESt13_Ios_OpenmodeRKS3_;

>-

>-    # basic_stringstream::view()

>-    _ZNKSt7__cxx1119basic_stringstreamI[cw]St11char_traitsI[cw]ESaI[cw]EE4viewEv;

>-

>     # basic_stringbuf::basic_stringbuf(allocator const&)

>     _ZNSt7__cxx1115basic_stringbufI[cw]St11char_traitsI[cw]ESaI[cw]EEC[12]ERKS3_;

> 

>@@ -2398,13 +2353,13 @@ GLIBCXX_3.4.29 {

>     # basic_stringbuf::view()

>     _ZNKSt7__cxx1115basic_stringbufI[cw]St11char_traitsI[cw]ESaI[cw]EE4viewEv;

> 

>-    # basic_istringstream::basic_istringstream(basic_string&&, ios_base::openmode)

>+    # basic_[io]stringstream::basic_[io]stringstream(basic_string&&, ios_base::openmode)

>     _ZNSt7__cxx1119basic_[io]stringstreamI[cw]St11char_traitsI[cw]ESaI[cw]EEC[12]EONS_12basic_stringI[cw]S2_S3_EESt13_Ios_Openmode;

> 

>     # basic_[io]stringstream::basic_[io]stringstream(ios_base::openmode, allocator const&)

>     _ZNSt7__cxx1119basic_[io]stringstreamI[cw]St11char_traitsI[cw]ESaI[cw]EEC[12]ESt13_Ios_OpenmodeRKS3_;

> 

>-    # basic_istringstream::view()

>+    # basic_[io]stringstream::view()

>     _ZNKSt7__cxx1119basic_[io]stringstreamI[cw]St11char_traitsI[cw]ESaI[cw]EE4viewEv;

> 

>     # basic_stringstream::basic_stringstream(basic_string&&, ios_base::openmode)

>@@ -2716,6 +2671,15 @@ CXXABI_1.3.12 {

> 

> } CXXABI_1.3.11;

> 

>+CXXABI_1.3.13 {

>+

>+    # std::exception_ptr::_M_addref()

>+    _ZNSt15__exception_ptr13exception_ptr9_M_addrefEv;

>+    # std::exception_ptr::_M_release()

>+    _ZNSt15__exception_ptr13exception_ptr10_M_releaseEv;

>+

>+} CXXABI_1.3.12;

>+

> # Symbols in the support library (libsupc++) supporting transactional memory.

> CXXABI_TM_1 {

>
commit c6bfc4eb3c961181912647781d7dd38057db655b
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Thu Oct 29 01:05:03 2020

    libstdc++: Fix new basic_stringbuf constructor
    
    libstdc++-v3/ChangeLog:
    
            * include/std/sstream (basic_stringbuf(__string_type&&, openmode)):
            Call _M_init_syncbuf to set up get/put areas. Also qualify
            std::move.

diff --git a/libstdc++-v3/include/std/sstream b/libstdc++-v3/include/std/sstream
index f03f3abd6fc..33a00486606 100644
--- a/libstdc++-v3/include/std/sstream
+++ b/libstdc++-v3/include/std/sstream
@@ -181,8 +181,8 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
       basic_stringbuf(__string_type&& __s,
 	              ios_base::openmode __mode = ios_base::in
 						  | ios_base::out )
-      : __streambuf_type(), _M_mode(__mode), _M_string(move(__s))
-      { }
+      : __streambuf_type(), _M_mode(__mode), _M_string(std::move(__s))
+      { _M_stringbuf_init(__mode); }
 
       template<typename _SAlloc>
       basic_stringbuf(const basic_string<_CharT, _Traits, _SAlloc>& __s,
Rainer Orth Oct. 29, 2020, 8:06 p.m. | #4
Hi Jonathan,

> On > The patch that was committed broke the linker script. The attached

> patch restores the piece that got lost, and removes the duplicate

> patterns added for the new symbols. Pushed to trunk.


even this fixed version broke Solaris bootstrap:

ld: fatal: libstdc++-symbols.ver-sun: 7318: symbol '_ZNKSt7__cxx1115basic_stringbufIcSt11char_traitsIcESaIcEE13get_allocatorEv': symbol version conflict
ld: fatal: libstdc++-symbols.ver-sun: 7319: symbol '_ZNKSt7__cxx1115basic_stringbufIwSt11char_traitsIwESaIwEE13get_allocatorEv': symbol version conflict

  matched by

    ##_ZNKSt7__cxx1115basic_stringbufI[cw]St11char_traitsI[cw]ESaI[cw]EE13get_allocatorEv (glob)
    _ZNKSt7__cxx1115basic_stringbufIcSt11char_traitsIcESaIcEE13get_allocatorEv;
    _ZNKSt7__cxx1115basic_stringbufIwSt11char_traitsIwESaIwEE13get_allocatorEv;

  and

    ##_ZNKSt7__cxx1115basic_stringbufI[cw]St11char_traitsI[cw]ESaI[cw]EE[0-35-9]* (glob)

  which matches

    _ZNKSt7__cxx1115basic_stringbufIcSt11char_traitsIcESaIcEE13get_allocatorEv;
    _ZNKSt7__cxx1115basic_stringbufIcSt11char_traitsIcESaIcEE3strEv;
    _ZNKSt7__cxx1115basic_stringbufIwSt11char_traitsIwESaIwEE13get_allocatorEv;
    _ZNKSt7__cxx1115basic_stringbufIwSt11char_traitsIwESaIwEE3strEv;

ld: fatal: libstdc++-symbols.ver-sun: 7321: symbol '_ZNKSt7__cxx1115basic_stringbufIcSt11char_traitsIcESaIcEE4viewEv': symbol version conflict
ld: fatal: libstdc++-symbols.ver-sun: 7322: symbol '_ZNKSt7__cxx1115basic_stringbufIwSt11char_traitsIwESaIwEE4viewEv': symbol version conflict

  matched by

    ##_ZNKSt7__cxx1115basic_stringbufI[cw]St11char_traitsI[cw]ESaI[cw]EE4viewEv (glob)
    _ZNKSt7__cxx1115basic_stringbufIcSt11char_traitsIcESaIcEE4viewEv;
    _ZNKSt7__cxx1115basic_stringbufIwSt11char_traitsIwESaIwEE4viewEv;

  and

    ##_ZNKSt7__cxx1115basic_stringbuf* (glob)

  which matches

    _ZNKSt7__cxx1115basic_stringbufIcSt11char_traitsIcESaIcEE13get_allocatorEv;
    _ZNKSt7__cxx1115basic_stringbufIcSt11char_traitsIcESaIcEE3strEv;
    _ZNKSt7__cxx1115basic_stringbufIcSt11char_traitsIcESaIcEE4viewEv;
    _ZNKSt7__cxx1115basic_stringbufIwSt11char_traitsIwESaIwEE13get_allocatorEv;
    _ZNKSt7__cxx1115basic_stringbufIwSt11char_traitsIwESaIwEE3strEv;
    _ZNKSt7__cxx1115basic_stringbufIwSt11char_traitsIwESaIwEE4viewEv;

ld: fatal: libstdc++-symbols.ver-sun: 7342: symbol '_ZNKSt7__cxx1119basic_istringstreamIcSt11char_traitsIcESaIcEE4viewEv': symbol version conflict
ld: fatal: libstdc++-symbols.ver-sun: 7343: symbol '_ZNKSt7__cxx1119basic_istringstreamIwSt11char_traitsIwESaIwEE4viewEv': symbol version conflict

  matched by

    ##_ZNKSt7__cxx1119basic_[io]stringstreamI[cw]St11char_traitsI[cw]ESaI[cw]EE4viewEv (glob)
    _ZNKSt7__cxx1119basic_istringstreamIcSt11char_traitsIcESaIcEE4viewEv;
    _ZNKSt7__cxx1119basic_istringstreamIwSt11char_traitsIwESaIwEE4viewEv;
    _ZNKSt7__cxx1119basic_ostringstreamIcSt11char_traitsIcESaIcEE4viewEv;
    _ZNKSt7__cxx1119basic_ostringstreamIwSt11char_traitsIwESaIwEE4viewEv;

  and

    ##_ZNKSt7__cxx1119basic_istringstream* (glob)
    ##_ZNKSt7__cxx1119basic_ostringstream* (glob)

  which match

    _ZNKSt7__cxx1119basic_istringstreamIcSt11char_traitsIcESaIcEE3strEv;
    _ZNKSt7__cxx1119basic_istringstreamIcSt11char_traitsIcESaIcEE4viewEv;
    _ZNKSt7__cxx1119basic_istringstreamIcSt11char_traitsIcESaIcEE5rdbufEv;
    _ZNKSt7__cxx1119basic_istringstreamIwSt11char_traitsIwESaIwEE3strEv;
    _ZNKSt7__cxx1119basic_istringstreamIwSt11char_traitsIwESaIwEE4viewEv;
    _ZNKSt7__cxx1119basic_istringstreamIwSt11char_traitsIwESaIwEE5rdbufEv;
    _ZNKSt7__cxx1119basic_ostringstreamIcSt11char_traitsIcESaIcEE3strEv;
    _ZNKSt7__cxx1119basic_ostringstreamIcSt11char_traitsIcESaIcEE4viewEv;
    _ZNKSt7__cxx1119basic_ostringstreamIcSt11char_traitsIcESaIcEE5rdbufEv;
    _ZNKSt7__cxx1119basic_ostringstreamIwSt11char_traitsIwESaIwEE3strEv;
    _ZNKSt7__cxx1119basic_ostringstreamIwSt11char_traitsIwESaIwEE4viewEv;
    _ZNKSt7__cxx1119basic_ostringstreamIwSt11char_traitsIwESaIwEE5rdbufEv;

Tightening the patterns as in the attached patch at least allows
libstdc++.so.6 to link on i386-pc-solaris2.11; full bootstrap still
running.  However, I can't tell if this is really correct.

	Rainer

-- 
-----------------------------------------------------------------------------
Rainer Orth, Center for Biotechnology, Bielefeld University
diff --git a/libstdc++-v3/config/abi/pre/gnu.ver b/libstdc++-v3/config/abi/pre/gnu.ver
--- a/libstdc++-v3/config/abi/pre/gnu.ver
+++ b/libstdc++-v3/config/abi/pre/gnu.ver
@@ -1791,11 +1791,11 @@ GLIBCXX_3.4.21 {
     _ZNSt7__cxx1119basic_[io]stringstreamI[cw]St11char_traitsI[cw]ESaI[cw]EEC[12]ESt13_Ios_Openmode;
     _ZNSt7__cxx1119basic_[io]stringstreamI[cw]St11char_traitsI[cw]ESaI[cw]EED[012]Ev;
     _ZNSt7__cxx1119basic_[io]stringstreamI[cw]St11char_traitsI[cw]ESaI[cw]EE[a34]*;
-    _ZNKSt7__cxx1115basic_stringbuf*;
+    _ZNKSt7__cxx1115basic_stringbufI[cw]St11char_traitsI[cw]ESaI[cw]EE[0235-9]*;
     _ZNKSt7__cxx1118basic_stringstreamI[cw]St11char_traitsI[cw]ESaI[cw]EE3strEv;
     _ZNKSt7__cxx1118basic_stringstreamI[cw]St11char_traitsI[cw]ESaI[cw]EE5rdbufEv;
-    _ZNKSt7__cxx1119basic_istringstream*;
-    _ZNKSt7__cxx1119basic_ostringstream*;
+    _ZNKSt7__cxx1119basic_istringstreamI[cw]St11char_traitsI[cw]ESaI[cw]EE[0-35-9]*;
+    _ZNKSt7__cxx1119basic_ostringstreamI[cw]St11char_traitsI[cw]ESaI[cw]EE[0-35-9]*;
     _ZT[ISTV]NSt7__cxx1115basic_stringbuf*;
     _ZT[ISTV]NSt7__cxx1118basic_stringstream*;
     _ZT[ISTV]NSt7__cxx1119basic_istringstream*;
H.J. Lu via Gcc-patches Oct. 29, 2020, 9:41 p.m. | #5
On 29/10/20 21:06 +0100, Rainer Orth wrote:
>Tightening the patterns as in the attached patch at least allows

>libstdc++.so.6 to link on i386-pc-solaris2.11; full bootstrap still

>running.  However, I can't tell if this is really correct.


I think we want this attached patch instead. It tightens them up to
exactly the symbols we actually need to export and no more. This will
avoid needing to tighten them again in the near future when the new
overloads of str() are added.
diff --git a/libstdc++-v3/config/abi/pre/gnu.ver b/libstdc++-v3/config/abi/pre/gnu.ver
index 80994b203df..4dddfd3d263 100644
--- a/libstdc++-v3/config/abi/pre/gnu.ver
+++ b/libstdc++-v3/config/abi/pre/gnu.ver
@@ -1791,11 +1791,11 @@ GLIBCXX_3.4.21 {
     _ZNSt7__cxx1119basic_[io]stringstreamI[cw]St11char_traitsI[cw]ESaI[cw]EEC[12]ESt13_Ios_Openmode;
     _ZNSt7__cxx1119basic_[io]stringstreamI[cw]St11char_traitsI[cw]ESaI[cw]EED[012]Ev;
     _ZNSt7__cxx1119basic_[io]stringstreamI[cw]St11char_traitsI[cw]ESaI[cw]EE[a34]*;
-    _ZNKSt7__cxx1115basic_stringbuf*;
+    _ZNKSt7__cxx1115basic_stringbufI[cw]St11char_traitsI[cw]ESaI[cw]EE3strEv;
     _ZNKSt7__cxx1118basic_stringstreamI[cw]St11char_traitsI[cw]ESaI[cw]EE3strEv;
     _ZNKSt7__cxx1118basic_stringstreamI[cw]St11char_traitsI[cw]ESaI[cw]EE5rdbufEv;
-    _ZNKSt7__cxx1119basic_istringstream*;
-    _ZNKSt7__cxx1119basic_ostringstream*;
+    _ZNKSt7__cxx1119basic_[io]stringstreamI[cw]St11char_traitsI[cw]ESaI[cw]EE3strEv;
+    _ZNKSt7__cxx1119basic_[io]stringstreamI[cw]St11char_traitsI[cw]ESaI[cw]EE5rdbufEv;
     _ZT[ISTV]NSt7__cxx1115basic_stringbuf*;
     _ZT[ISTV]NSt7__cxx1118basic_stringstream*;
     _ZT[ISTV]NSt7__cxx1119basic_istringstream*;
H.J. Lu via Gcc-patches Oct. 29, 2020, 10:51 p.m. | #6
On 29/10/20 21:41 +0000, Jonathan Wakely wrote:
>On 29/10/20 21:06 +0100, Rainer Orth wrote:

>>Tightening the patterns as in the attached patch at least allows

>>libstdc++.so.6 to link on i386-pc-solaris2.11; full bootstrap still

>>running.  However, I can't tell if this is really correct.

>

>I think we want this attached patch instead. It tightens them up to

>exactly the symbols we actually need to export and no more. This will

>avoid needing to tighten them again in the near future when the new

>overloads of str() are added.

>

>


>diff --git a/libstdc++-v3/config/abi/pre/gnu.ver b/libstdc++-v3/config/abi/pre/gnu.ver

>index 80994b203df..4dddfd3d263 100644

>--- a/libstdc++-v3/config/abi/pre/gnu.ver

>+++ b/libstdc++-v3/config/abi/pre/gnu.ver

>@@ -1791,11 +1791,11 @@ GLIBCXX_3.4.21 {

>     _ZNSt7__cxx1119basic_[io]stringstreamI[cw]St11char_traitsI[cw]ESaI[cw]EEC[12]ESt13_Ios_Openmode;

>     _ZNSt7__cxx1119basic_[io]stringstreamI[cw]St11char_traitsI[cw]ESaI[cw]EED[012]Ev;

>     _ZNSt7__cxx1119basic_[io]stringstreamI[cw]St11char_traitsI[cw]ESaI[cw]EE[a34]*;

>-    _ZNKSt7__cxx1115basic_stringbuf*;

>+    _ZNKSt7__cxx1115basic_stringbufI[cw]St11char_traitsI[cw]ESaI[cw]EE3strEv;

>     _ZNKSt7__cxx1118basic_stringstreamI[cw]St11char_traitsI[cw]ESaI[cw]EE3strEv;

>     _ZNKSt7__cxx1118basic_stringstreamI[cw]St11char_traitsI[cw]ESaI[cw]EE5rdbufEv;

>-    _ZNKSt7__cxx1119basic_istringstream*;

>-    _ZNKSt7__cxx1119basic_ostringstream*;

>+    _ZNKSt7__cxx1119basic_[io]stringstreamI[cw]St11char_traitsI[cw]ESaI[cw]EE3strEv;

>+    _ZNKSt7__cxx1119basic_[io]stringstreamI[cw]St11char_traitsI[cw]ESaI[cw]EE5rdbufEv;

>     _ZT[ISTV]NSt7__cxx1115basic_stringbuf*;

>     _ZT[ISTV]NSt7__cxx1118basic_stringstream*;

>     _ZT[ISTV]NSt7__cxx1119basic_istringstream*;



Pushed to trunk now.
Rainer Orth Oct. 30, 2020, 12:39 p.m. | #7
Hi Jonathan,

> On 29/10/20 21:06 +0100, Rainer Orth wrote:

>>Tightening the patterns as in the attached patch at least allows

>>libstdc++.so.6 to link on i386-pc-solaris2.11; full bootstrap still

>>running.  However, I can't tell if this is really correct.

>

> I think we want this attached patch instead. It tightens them up to

> exactly the symbols we actually need to export and no more. This will

> avoid needing to tighten them again in the near future when the new

> overloads of str() are added.


that's even better of course.

Thanks.
        Rainer

-- 
-----------------------------------------------------------------------------
Rainer Orth, Center for Biotechnology, Bielefeld University

Patch

diff --git a/libstdc++-v3/acinclude.m4 b/libstdc++-v3/acinclude.m4
index 133125ec4fa..b9452dd74cd 100644
--- a/libstdc++-v3/acinclude.m4
+++ b/libstdc++-v3/acinclude.m4
@@ -49,7 +49,7 @@  AC_DEFUN([GLIBCXX_CONFIGURE], [
   # Keep these sync'd with the list in Makefile.am.  The first provides an
   # expandable list at autoconf time; the second provides an expandable list
   # (i.e., shell variable) at configure time.
-  m4_define([glibcxx_SUBDIRS],[include libsupc++ src src/c++98 src/c++11 src/c++17 src/filesystem doc po testsuite python])
+  m4_define([glibcxx_SUBDIRS],[include libsupc++ src src/c++98 src/c++11 src/c++17 src/c++20 src/filesystem doc po testsuite python])
   SUBDIRS='glibcxx_SUBDIRS'
 
   # These need to be absolute paths, yet at the same time need to
diff --git a/libstdc++-v3/config/abi/pre/gnu.ver b/libstdc++-v3/config/abi/pre/gnu.ver
index 6a2b2da33f5..a782776bd5f 100644
--- a/libstdc++-v3/config/abi/pre/gnu.ver
+++ b/libstdc++-v3/config/abi/pre/gnu.ver
@@ -2325,6 +2325,51 @@  GLIBCXX_3.4.29 {
     # std::__throw_bad_array_new_length()
     _ZSt28__throw_bad_array_new_lengthv;
 
+    # basic_stringbuf::basic_stringbuf(allocator const&)
+    _ZNSt7__cxx1115basic_stringbufI[cw]St11char_traitsI[cw]ESaI[cw]EEC1ERKS3_;
+
+    # basic_stringbuf::basic_stringbuf(ios_base::openmode, allocator const&)
+    _ZNSt7__cxx1115basic_stringbufI[cw]St11char_traitsI[cw]ESaI[cw]EEC1ESt13_Ios_OpenmodeRKS3;
+
+    # basic_stringbuf::basic_stringbuf(basic_string&&, ios_base::openmode)
+    _ZNSt7__cxx1115basic_stringbufI[cw]St11char_traitsI[cw]ESaI[cw]EEC1EONS_12basic_stringI[cw]S2_S3_EESt13_Ios_Openmode;
+
+    # basic_stringbuf::basic_stringbuf(basic_stringbuf&&, allocator const&)
+    _ZNSt7__cxx1115basic_stringbufI[cw]St11char_traitsI[cw]ESaIcEEC1EOS4_RKS3_;
+
+    # basic_stringbuf::get_allocator()
+    _ZNKSt7__cxx1115basic_stringbufI[cw]St11char_traitsI[cw]ESaI[cw]EE13get_allocatorEv;
+
+    # basic_stringbuf::view()
+    _ZNKSt7__cxx1115basic_stringbufI[cw]St11char_traitsI[cw]ESaI[cw]EE4viewEv;
+
+    # basic_istringstream::basic_istringstream(basic_string&&, ios_base::openmode)
+    _ZNSt7__cxx1119basic_istringstreamI[cw]St11char_traitsI[cw]ESaIcEEC1EONS_12basic_stringI[cw]S2_S3_EESt13_Ios_Openmode;
+
+    # basic_istringstream::basic_istringstream(ios_base::openmode, allocator const&)
+    _ZNSt7__cxx1119basic_istringstreamI[cw]St11char_traitsI[cw]ESaI[cw]EEC1ESt13_Ios_OpenmodeRKS3_;
+
+    # basic_istringstream::view()
+    _ZNKSt7__cxx1119basic_istringstreamI[cw]St11char_traitsI[cw]ESaI[cw]EE4viewEv;
+
+    # basic_ostringstream::basic_ostringstream(basic_string&&, ios_base::openmode)
+    _ZNSt7__cxx1119basic_ostringstreamI[cw]St11char_traitsI[cw]ESaIcEEC1EONS_12basic_stringI[cw]S2_S3_EESt13_Ios_Openmode;
+
+    # basic_ostringstream::basic_ostringstream(ios_base::openmode, allocator const&)
+    _ZNSt7__cxx1119basic_ostringstreamI[cw]St11char_traitsI[cw]ESaIcEEC1ESt13_Ios_OpenmodeRKS3_;
+
+    # basic_ostringstream::view()
+    _ZNKSt7__cxx1119basic_ostringstreamI[cw]St11char_traitsI[cw]ESaI[cw]EE4viewEv;
+
+    # basic_stringstream::basic_stringstream(basic_string&&, ios_base::openmode)
+    _ZNSt7__cxx1119basic_stringstreamI[cw]St11char_traitsI[cw]ESaIcEEC1EONS_12basic_stringI[cw]S2_S3_EESt13_Ios_Openmode;
+
+    # basic_stringstream::basic_stringstream(ios_base::openmode, allocator const&)
+    _ZNSt7__cxx1119basic_stringstreamI[cw]St11char_traitsI[cw]ESaIcEEC1ESt13_Ios_OpenmodeRKS3_;
+
+    # basic_stringstream::view()
+    _ZNKSt7__cxx1119basic_stringstreamI[cw]St11char_traitsI[cw]ESaI[cw]EE4viewEv;
+
 } GLIBCXX_3.4.28;
 
 # Symbols in the support library (libsupc++) have their own tag.
diff --git a/libstdc++-v3/include/std/sstream b/libstdc++-v3/include/std/sstream
index 9cca54d17d1..b191c471b39 100644
--- a/libstdc++-v3/include/std/sstream
+++ b/libstdc++-v3/include/std/sstream
@@ -165,6 +165,55 @@  _GLIBCXX_BEGIN_NAMESPACE_CXX11
       }
 #endif
 
+#if __cplusplus > 201703L && _GLIBCXX_USE_CXX11_ABI
+      using __sv_type = basic_string_view<char_type, traits_type>;
+
+      basic_stringbuf(const allocator_type& __a)
+      : basic_stringbuf(ios_base::in | std::ios_base::out, __a)
+      { }
+
+      basic_stringbuf(ios_base::openmode __mode,
+		      const allocator_type& __a)
+      : __streambuf_type(), _M_mode(__mode), _M_string(__a)
+      { }
+
+      explicit
+      basic_stringbuf(__string_type&& __s,
+	              ios_base::openmode __mode = ios_base::in
+						  | ios_base::out )
+      : __streambuf_type(), _M_mode(__mode), _M_string(move(__s))
+      { }
+
+      template<typename _SAlloc>
+      basic_stringbuf(const basic_string<_CharT, _Traits, _SAlloc>& __s,
+		      const allocator_type& __a )
+      : basic_stringbuf(__s, ios_base::in | std::ios_base::out, __a )
+      { }
+
+      template<typename _SAlloc>
+      basic_stringbuf(const basic_string<_CharT, _Traits, _SAlloc>& __s,
+		      ios_base::openmode __mode,
+		      const allocator_type& __a)
+      : __streambuf_type(), _M_mode(__mode),
+      _M_string(static_cast<__sv_type>(__s), __a)
+      { }
+
+      template<typename _SAlloc>
+	explicit
+	basic_stringbuf(const basic_string<_CharT, _Traits, _SAlloc>& __s,
+	                ios_base::openmode __mode = ios_base::in
+						    | ios_base::out)
+	: basic_stringbuf(__s, __mode, allocator_type{})
+	{ }
+
+      basic_stringbuf(basic_stringbuf&& __rhs, const allocator_type& __a)
+      : basic_stringbuf(std::move(__rhs), __a, __xfer_bufptrs(__rhs, this))
+      { __rhs._M_sync(const_cast<char_type*>(__rhs._M_string.data()), 0, 0); }
+
+      allocator_type get_allocator() const noexcept
+      { return _M_string.get_allocator(); }
+#endif
+
       // Get and set:
       /**
        *  @brief  Copying out the string buffer.
@@ -207,6 +256,23 @@  _GLIBCXX_BEGIN_NAMESPACE_CXX11
 	_M_stringbuf_init(_M_mode);
       }
 
+#if __cplusplus > 201703L && _GLIBCXX_USE_CXX11_ABI
+      __sv_type
+      view() const noexcept
+      {
+	if (this->pptr())
+	  {
+	    // The current egptr() may not be the actual string end.
+	    if (this->pptr() > this->egptr())
+	      return __sv_type(this->pbase(), this->pptr());
+	    else
+	      return __sv_type(this->pbase(), this->egptr());
+	  }
+	else
+	  return static_cast<__sv_type>(_M_string);
+      }
+#endif
+
     protected:
       // Common initialization code goes here.
       void
@@ -369,6 +435,16 @@  _GLIBCXX_BEGIN_NAMESPACE_CXX11
       : __streambuf_type(static_cast<const __streambuf_type&>(__rhs)),
       _M_mode(__rhs._M_mode), _M_string(std::move(__rhs._M_string))
       { }
+
+#if __cplusplus > 201703L && _GLIBCXX_USE_CXX11_ABI
+      // The move constructor initializes an __xfer_bufptrs temporary then
+      // delegates to this constructor to performs moves during its lifetime.
+      basic_stringbuf(basic_stringbuf&& __rhs, const allocator_type& __a,
+		      __xfer_bufptrs&&)
+      : __streambuf_type(static_cast<const __streambuf_type&>(__rhs)),
+      _M_mode(__rhs._M_mode), _M_string(std::move(__rhs._M_string), __a)
+      { }
+#endif
 #endif
     };
 
@@ -500,6 +576,38 @@  _GLIBCXX_BEGIN_NAMESPACE_CXX11
       }
 #endif
 
+#if __cplusplus > 201703L && _GLIBCXX_USE_CXX11_ABI
+      basic_istringstream(ios_base::openmode __mode, const allocator_type& __a)
+      : __istream_type(), _M_stringbuf(__mode | ios_base::in, __a)
+      { this->init(std::__addressof(_M_stringbuf)); }
+
+      explicit basic_istringstream(__string_type&& __str,
+	                           ios_base::openmode __mode = ios_base::in )
+      : __istream_type(), _M_stringbuf(std::move(__str), __mode | ios_base::in)
+      { this->init(std::__addressof(_M_stringbuf)); }
+
+      template<typename _SAlloc>
+	basic_istringstream(const basic_string<_CharT, _Traits, _SAlloc>& __str,
+			    const allocator_type& __a)
+	: basic_istringstream(__str, ios_base::in, __a)
+	{ }
+
+      template<typename _SAlloc>
+	basic_istringstream(const basic_string<_CharT, _Traits, _SAlloc>& __str,
+			    ios_base::openmode __mode,
+			    const allocator_type& __a)
+	: __istream_type(),
+	_M_stringbuf(__string_type(__str.data(), __str.size()),
+		     __mode | ios_base::in, __a)
+	{ this->init(std::__addressof(_M_stringbuf)); }
+
+      template<typename _SAlloc>
+	explicit basic_istringstream(const basic_string<_CharT, _Traits, _SAlloc>& __str,
+	                             ios_base::openmode __mode = ios_base::in)
+	: basic_istringstream(__str, __mode, allocator_type())
+	{ }
+#endif
+
       // Members:
       /**
        *  @brief  Accessing the underlying buffer.
@@ -528,6 +636,12 @@  _GLIBCXX_BEGIN_NAMESPACE_CXX11
       void
       str(const __string_type& __s)
       { _M_stringbuf.str(__s); }
+
+#if __cplusplus > 201703L && _GLIBCXX_USE_CXX11_ABI
+      basic_string_view<char_type, traits_type>
+      view() const noexcept
+      { return _M_stringbuf.view(); }
+#endif
     };
 
 
@@ -658,6 +772,38 @@  _GLIBCXX_BEGIN_NAMESPACE_CXX11
       }
 #endif
 
+#if __cplusplus > 201703L && _GLIBCXX_USE_CXX11_ABI
+      basic_ostringstream(ios_base::openmode __mode, const allocator_type& __a)
+      : __ostream_type(), _M_stringbuf(__mode | ios_base::out, __a)
+      { this->init(std::__addressof(_M_stringbuf)); }
+
+      explicit basic_ostringstream(__string_type&& __str,
+	                           ios_base::openmode __mode = ios_base::out )
+      : __ostream_type(), _M_stringbuf(std::move(__str), __mode | ios_base::out)
+      { this->init(std::__addressof(_M_stringbuf)); }
+
+      template<typename _SAlloc>
+	basic_ostringstream(const basic_string<_CharT, _Traits, _SAlloc>& __str,
+			    const allocator_type& __a)
+	: basic_ostringstream(__str, ios_base::out, __a)
+	{ }
+
+      template<typename _SAlloc>
+	basic_ostringstream(const basic_string<_CharT, _Traits, _SAlloc>& __str,
+			    ios_base::openmode __mode,
+			    const allocator_type& __a)
+	: __ostream_type(),
+	_M_stringbuf(__string_type(__str.data(), __str.size()),
+		     __mode | ios_base::out, __a)
+	{ this->init(std::__addressof(_M_stringbuf)); }
+
+      template<typename _SAlloc>
+	explicit basic_ostringstream(const basic_string<_CharT, _Traits, _SAlloc>& __str,
+	                             ios_base::openmode __mode = ios_base::out)
+	: basic_ostringstream(__str, __mode, allocator_type())
+	{ }
+#endif
+
       // Members:
       /**
        *  @brief  Accessing the underlying buffer.
@@ -686,6 +832,12 @@  _GLIBCXX_BEGIN_NAMESPACE_CXX11
       void
       str(const __string_type& __s)
       { _M_stringbuf.str(__s); }
+
+#if __cplusplus > 201703L && _GLIBCXX_USE_CXX11_ABI
+      basic_string_view<char_type, traits_type>
+      view() const noexcept
+      { return _M_stringbuf.view(); }
+#endif
     };
 
 
@@ -812,6 +964,38 @@  _GLIBCXX_BEGIN_NAMESPACE_CXX11
       }
 #endif
 
+#if __cplusplus > 201703L && _GLIBCXX_USE_CXX11_ABI
+      basic_stringstream(ios_base::openmode __mode, const allocator_type& __a)
+      : __iostream_type(), _M_stringbuf(__mode, __a)
+      { this->init(&_M_stringbuf); }
+
+      explicit basic_stringstream(__string_type&& __str,
+	                          ios_base::openmode __mode = ios_base::out
+							      | ios_base::out)
+      : __iostream_type(), _M_stringbuf(std::move(__str), __mode)
+      { this->init(std::__addressof(_M_stringbuf)); }
+
+      template<typename _SAlloc>
+	basic_stringstream(const basic_string<_CharT, _Traits, _SAlloc>& __str,
+			   const allocator_type& __a)
+	: basic_stringstream(__str, ios_base::in | ios_base::out, __a)
+	{ }
+
+      template<typename _SAlloc>
+	basic_stringstream(const basic_string<_CharT, _Traits, _SAlloc>& __str,
+			   ios_base::openmode __mode, const allocator_type& __a)
+	: __iostream_type(),
+	_M_stringbuf(__string_type(__str.data(), __str.size()), __mode, __a)
+	{ this->init(std::__addressof(_M_stringbuf)); }
+
+      template<typename _SAlloc>
+	explicit basic_stringstream(const basic_string<_CharT, _Traits, _SAlloc>& __str,
+	                            ios_base::openmode __mode = ios_base::in
+								| ios_base::out)
+	: basic_stringstream(__str, __mode, allocator_type())
+	{ }
+#endif
+
       // Members:
       /**
        *  @brief  Accessing the underlying buffer.
@@ -840,6 +1024,12 @@  _GLIBCXX_BEGIN_NAMESPACE_CXX11
       void
       str(const __string_type& __s)
       { _M_stringbuf.str(__s); }
+
+#if __cplusplus > 201703L && _GLIBCXX_USE_CXX11_ABI
+      basic_string_view<char_type, traits_type>
+      view() const noexcept
+      { return _M_stringbuf.view(); }
+#endif
     };
 
 #if __cplusplus >= 201103L
diff --git a/libstdc++-v3/src/Makefile.am b/libstdc++-v3/src/Makefile.am
index a139adc81b3..9a6807ae8c6 100644
--- a/libstdc++-v3/src/Makefile.am
+++ b/libstdc++-v3/src/Makefile.am
@@ -29,7 +29,7 @@  filesystem_dir =
 endif
 
 ## Keep this list sync'd with acinclude.m4:GLIBCXX_CONFIGURE.
-SUBDIRS = c++98 c++11 c++17 $(filesystem_dir)
+SUBDIRS = c++98 c++11 c++17 c++20 $(filesystem_dir)
 
 # Cross compiler support.
 if VTV_CYGMIN
@@ -60,6 +60,7 @@  endif
 vpath % $(top_srcdir)/src/c++98
 vpath % $(top_srcdir)/src/c++11
 vpath % $(top_srcdir)/src/c++17
+vpath % $(top_srcdir)/src/c++20
 if ENABLE_FILESYSTEM_TS
 vpath % $(top_srcdir)/src/filesystem
 endif
@@ -95,14 +96,16 @@  libstdc___la_LIBADD = \
 	$(top_builddir)/libsupc++/libsupc++convenience.la \
 	$(top_builddir)/src/c++98/libc++98convenience.la \
 	$(top_builddir)/src/c++11/libc++11convenience.la \
-	$(top_builddir)/src/c++17/libc++17convenience.la
+	$(top_builddir)/src/c++17/libc++17convenience.la \
+	$(top_builddir)/src/c++20/libc++20convenience.la
 
 libstdc___la_DEPENDENCIES = \
 	${version_dep} \
 	$(top_builddir)/libsupc++/libsupc++convenience.la \
 	$(top_builddir)/src/c++98/libc++98convenience.la \
 	$(top_builddir)/src/c++11/libc++11convenience.la \
-	$(top_builddir)/src/c++17/libc++17convenience.la
+	$(top_builddir)/src/c++17/libc++17convenience.la \
+	$(top_builddir)/src/c++20/libc++20convenience.la
 
 libstdc___la_LDFLAGS = \
 	-version-info $(libtool_VERSION) ${version_arg} -lm
@@ -153,7 +156,8 @@  compatibility-condvar.o: compatibility-condvar.cc
 # segregated in the sources with -D_GLIBCXX_SHARED.
 #
 # In the sub-directories of libsupc++, src/c++98, src/c++11, src/c++17,
-# only -prefer-pic objects are generated for the convenience libraries.
+# src/c++20, only -prefer-pic objects are generated for the convenience
+# libraries.
 #
 # In the main src directory, make shared and static objects just for
 # the compat libraries. Shared objects are compiled with -prefer-pic
diff --git a/libstdc++-v3/src/c++20/Makefile.am b/libstdc++-v3/src/c++20/Makefile.am
new file mode 100644
index 00000000000..423a79f3686
--- /dev/null
+++ b/libstdc++-v3/src/c++20/Makefile.am
@@ -0,0 +1,105 @@ 
+## Makefile for the C++20 sources of the GNU C++ Standard library.
+##
+## Copyright (C) 1997-2020 Free Software Foundation, Inc.
+##
+## This file is part of the libstdc++ version 3 distribution.
+## Process this file with automake to produce Makefile.in.
+
+## 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/>.
+
+include $(top_srcdir)/fragment.am
+
+# Convenience library for C++17 runtime.
+noinst_LTLIBRARIES = libc++20convenience.la
+
+headers =
+
+if ENABLE_EXTERN_TEMPLATE
+# XTEMPLATE_FLAGS = -fno-implicit-templates
+inst_sources = \
+	sstream-inst.cc
+else
+# XTEMPLATE_FLAGS =
+inst_sources =
+endif
+
+sources =
+
+vpath % $(top_srcdir)/src/c++20
+
+libc__20convenience_la_SOURCES = $(sources)  $(inst_sources)
+
+# AM_CXXFLAGS needs to be in each subdirectory so that it can be
+# modified in a per-library or per-sub-library way.  Need to manually
+# set this option because CONFIG_CXXFLAGS has to be after
+# OPTIMIZE_CXXFLAGS on the compile line so that -O2 can be overridden
+# as the occasion calls for it.
+AM_CXXFLAGS = \
+	-std=gnu++20 \
+	$(glibcxx_lt_pic_flag) $(glibcxx_compiler_shared_flag) \
+	$(XTEMPLATE_FLAGS) $(VTV_CXXFLAGS) \
+	$(WARN_CXXFLAGS) $(OPTIMIZE_CXXFLAGS) $(CONFIG_CXXFLAGS) \
+	-fimplicit-templates
+
+AM_MAKEFLAGS = \
+	"gxx_include_dir=$(gxx_include_dir)"
+
+# Libtool notes
+
+# 1) In general, libtool expects an argument such as `--tag=CXX' when
+# using the C++ compiler, because that will enable the settings
+# detected when C++ support was being configured.  However, when no
+# such flag is given in the command line, libtool attempts to figure
+# it out by matching the compiler name in each configuration section
+# against a prefix of the command line.  The problem is that, if the
+# compiler name and its initial flags stored in the libtool
+# configuration file don't match those in the command line, libtool
+# can't decide which configuration to use, and it gives up.  The
+# correct solution is to add `--tag CXX' to LTCXXCOMPILE and maybe
+# CXXLINK, just after $(LIBTOOL), so that libtool doesn't have to
+# attempt to infer which configuration to use.
+#
+# The second tag argument, `--tag disable-shared` means that libtool
+# only compiles each source once, for static objects. In actuality,
+# glibcxx_lt_pic_flag and glibcxx_compiler_shared_flag are added to
+# the libtool command that is used create the object, which is
+# suitable for shared libraries.  The `--tag disable-shared` must be
+# placed after --tag CXX lest things CXX undo the affect of
+# disable-shared.
+
+# 2) Need to explicitly set LTCXXCOMPILE so that EXTRA_CXX_FLAGS is
+# last. (That way, things like -O2 passed down from the toplevel can
+# be overridden by --enable-debug.)
+LTCXXCOMPILE = \
+	$(LIBTOOL) --tag CXX --tag disable-shared \
+	$(AM_LIBTOOLFLAGS) $(LIBTOOLFLAGS) \
+	--mode=compile $(CXX) $(TOPLEVEL_INCLUDES) \
+	$(AM_CPPFLAGS) $(CPPFLAGS) $(AM_CXXFLAGS) $(CXXFLAGS) $(EXTRA_CXX_FLAGS)
+
+LTLDFLAGS = $(shell $(SHELL) $(top_srcdir)/../libtool-ldflags $(LDFLAGS))
+
+# 3) We'd have a problem when building the shared libstdc++ object if
+# the rules automake generates would be used.  We cannot allow g++ to
+# be used since this would add -lstdc++ to the link line which of
+# course is problematic at this point.  So, we get the top-level
+# directory to configure libstdc++-v3 to use gcc as the C++
+# compilation driver.
+CXXLINK = \
+	$(LIBTOOL) --tag CXX --tag disable-shared \
+	$(AM_LIBTOOLFLAGS) $(LIBTOOLFLAGS) \
+	--mode=link $(CXX) \
+	$(VTV_CXXLINKFLAGS) \
+	$(OPT_LDFLAGS) $(SECTION_LDFLAGS) $(AM_CXXFLAGS) $(LTLDFLAGS) -o $@
diff --git a/libstdc++-v3/src/c++20/Makefile.in b/libstdc++-v3/src/c++20/Makefile.in
new file mode 100644
index 00000000000..0e2de19ae59
diff --git a/libstdc++-v3/src/c++20/sstream-inst.cc b/libstdc++-v3/src/c++20/sstream-inst.cc
new file mode 100644
index 00000000000..e04560d28c8
--- /dev/null
+++ b/libstdc++-v3/src/c++20/sstream-inst.cc
@@ -0,0 +1,108 @@ 
+// Explicit instantiation file.
+
+// Copyright (C) 2020 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.
+
+// Under Section 7 of GPL version 3, you are granted additional
+// permissions described in the GCC Runtime Library Exception, version
+// 3.1, as published by the Free Software Foundation.
+
+// You should have received a copy of the GNU General Public License and
+// a copy of the GCC Runtime Library Exception along with this program;
+// see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
+// <http://www.gnu.org/licenses/>.
+
+//
+// ISO C++ 14882:
+//
+
+// Instantiations in this file are only for the new SSO std::string ABI
+#include <sstream>
+
+namespace std _GLIBCXX_VISIBILITY(default)
+{
+_GLIBCXX_BEGIN_NAMESPACE_VERSION
+
+template basic_stringbuf<char>::basic_stringbuf(const allocator_type&);
+template basic_stringbuf<char>::basic_stringbuf(ios_base::openmode,
+						const allocator_type&);
+template basic_stringbuf<char>::basic_stringbuf(__string_type&&,
+						ios_base::openmode);
+template basic_stringbuf<char>::basic_stringbuf(basic_stringbuf&&,
+						const allocator_type&);
+template basic_stringbuf<char>::allocator_type
+basic_stringbuf<char>::get_allocator() const noexcept;
+template basic_stringbuf<char>::__sv_type
+basic_stringbuf<char>::view() const noexcept;
+
+template basic_istringstream<char>::basic_istringstream(ios_base::openmode,
+							const allocator_type&);
+template basic_istringstream<char>::basic_istringstream(__string_type&&,
+							ios_base::openmode);
+template string_view
+basic_istringstream<char>::view() const noexcept;
+
+template basic_ostringstream<char>::basic_ostringstream(ios_base::openmode,
+							const allocator_type&);
+template basic_ostringstream<char>::basic_ostringstream(__string_type&&,
+							ios_base::openmode);
+template string_view
+basic_ostringstream<char>::view() const noexcept;
+
+template basic_stringstream<char>::basic_stringstream(ios_base::openmode,
+						      const allocator_type&);
+template basic_stringstream<char>::basic_stringstream(__string_type&&,
+						      ios_base::openmode);
+template string_view
+basic_stringstream<char>::view() const noexcept;
+
+#ifdef _GLIBCXX_USE_WCHAR_T
+using wsv_type = basic_string_view<wchar_t>;
+
+template basic_stringbuf<wchar_t>::basic_stringbuf(const allocator_type&);
+template basic_stringbuf<wchar_t>::basic_stringbuf(ios_base::openmode,
+						   const allocator_type&);
+template basic_stringbuf<wchar_t>::basic_stringbuf(__string_type&&,
+						   ios_base::openmode);
+template basic_stringbuf<wchar_t>::basic_stringbuf(basic_stringbuf&&,
+						   const allocator_type&);
+template basic_stringbuf<wchar_t>::allocator_type
+basic_stringbuf<wchar_t>::get_allocator() const noexcept;
+
+template basic_istringstream<wchar_t>::__stringbuf_type::__sv_type
+basic_stringbuf<wchar_t>::view() const noexcept;
+
+template basic_istringstream<wchar_t>::basic_istringstream(ios_base::openmode,
+							   const allocator_type&);
+template basic_istringstream<wchar_t>::basic_istringstream(__string_type&&,
+							   ios_base::openmode);
+template wstring_view
+basic_istringstream<wchar_t>::view() const noexcept;
+
+template basic_ostringstream<wchar_t>::basic_ostringstream(ios_base::openmode,
+							   const allocator_type&);
+template basic_ostringstream<wchar_t>::basic_ostringstream(__string_type&&,
+							   ios_base::openmode);
+template wstring_view
+basic_ostringstream<wchar_t>::view() const noexcept;
+
+template basic_stringstream<wchar_t>::basic_stringstream(ios_base::openmode,
+							 const allocator_type&);
+template basic_stringstream<wchar_t>::basic_stringstream(__string_type&&,
+							 ios_base::openmode);
+template wstring_view
+basic_stringstream<wchar_t>::view() const noexcept;
+#endif
+
+_GLIBCXX_END_NAMESPACE_VERSION
+}
diff --git a/libstdc++-v3/testsuite/27_io/basic_istringstream/cons/char/1.cc b/libstdc++-v3/testsuite/27_io/basic_istringstream/cons/char/1.cc
new file mode 100644
index 00000000000..496aa6963e0
--- /dev/null
+++ b/libstdc++-v3/testsuite/27_io/basic_istringstream/cons/char/1.cc
@@ -0,0 +1,85 @@ 
+// Copyright (C) 2020 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/>.
+
+// C++20 29.8.2.2  basic_stringbuf constructors  [stringbuf.cons
+
+// { dg-options "-std=gnu++2a" }
+// { dg-do run { target c++2a } }
+// { dg-require-effective-target cxx11-abi }
+
+#include <sstream>
+#include <string>
+#include <testsuite_allocator.h>
+#include <testsuite_hooks.h>
+
+void
+test01()
+{
+  std::istringstream::allocator_type a;
+  std::istringstream stm(std::ios_base::in, a);
+}
+
+auto const cstr = "This is a test";
+
+void
+test02()
+{
+  std::string s1(cstr);
+  std::istringstream stm(std::move(s1));
+  VERIFY( s1.empty() );
+
+  std::string s2(cstr);
+  VERIFY( stm.str() == s2 );
+}
+
+void
+test03()
+{
+  using alloc_type = __gnu_test::tracker_allocator<char>;
+  using str_type = std::basic_string<char, std::char_traits<char>, alloc_type>;
+
+  auto const mode = std::ios_base::in;
+  str_type s1(cstr);
+
+  {
+    std::istringstream::allocator_type a;
+    std::istringstream sbuf(s1, mode, a);
+    std::string s2(cstr);
+    VERIFY( sbuf.str() == s2 );
+  }
+
+  {
+    std::istringstream sbuf(s1, mode);
+    std::string s2(cstr);
+    VERIFY( sbuf.str() == s2 );
+  }
+
+  {
+    std::istringstream sbuf(s1);
+    std::string s2(cstr);
+    VERIFY( sbuf.str() == s2 );
+  }
+}
+
+int
+main()
+{
+  test01();
+  test02();
+  test03();
+  return 0;
+}
diff --git a/libstdc++-v3/testsuite/27_io/basic_istringstream/cons/wchar_t/1.cc b/libstdc++-v3/testsuite/27_io/basic_istringstream/cons/wchar_t/1.cc
new file mode 100644
index 00000000000..26a3a86c46e
--- /dev/null
+++ b/libstdc++-v3/testsuite/27_io/basic_istringstream/cons/wchar_t/1.cc
@@ -0,0 +1,85 @@ 
+// Copyright (C) 2020 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/>.
+
+// C++20 29.8.2.2  basic_stringbuf constructors  [stringbuf.cons
+
+// { dg-options "-std=gnu++2a" }
+// { dg-do run { target c++2a } }
+// { dg-require-effective-target cxx11-abi }
+
+#include <sstream>
+#include <string>
+#include <testsuite_allocator.h>
+#include <testsuite_hooks.h>
+
+void
+test01()
+{
+  std::wistringstream::allocator_type a;
+  std::wistringstream stm(std::ios_base::in, a);
+}
+
+auto const cstr = L"This is a test";
+
+void
+test02()
+{
+  std::wstring s1(cstr);
+  std::wistringstream stm(std::move(s1));
+  VERIFY( s1.empty() );
+
+  std::wstring s2(cstr);
+  VERIFY( stm.str() == s2 );
+}
+
+void
+test03()
+{
+  using alloc_type = __gnu_test::tracker_allocator<wchar_t>;
+  using str_type = std::basic_string<wchar_t, std::char_traits<wchar_t>, alloc_type>;
+
+  auto const mode = std::ios_base::in;
+  str_type s1(cstr);
+
+  {
+    std::wistringstream::allocator_type a;
+    std::wistringstream sbuf(s1, mode, a);
+    std::wstring s2(cstr);
+    VERIFY( sbuf.str() == s2 );
+  }
+
+  {
+    std::wistringstream sbuf(s1, mode);
+    std::wstring s2(cstr);
+    VERIFY( sbuf.str() == s2 );
+  }
+
+  {
+    std::wistringstream sbuf(s1);
+    std::wstring s2(cstr);
+    VERIFY( sbuf.str() == s2 );
+  }
+}
+
+int
+main()
+{
+  test01();
+  test02();
+  test03();
+  return 0;
+}
diff --git a/libstdc++-v3/testsuite/27_io/basic_istringstream/view/char/1.cc b/libstdc++-v3/testsuite/27_io/basic_istringstream/view/char/1.cc
new file mode 100644
index 00000000000..091de5f7a79
--- /dev/null
+++ b/libstdc++-v3/testsuite/27_io/basic_istringstream/view/char/1.cc
@@ -0,0 +1,35 @@ 
+// Copyright (C) 2020 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/>.
+
+// 27.7.1.1  basic_stringbuf constructors  [lib.stringbuf.cons]
+
+// { dg-options "-std=gnu++2a" }
+// { dg-do run { target c++2a } }
+// { dg-require-effective-target cxx11-abi }
+
+#include <sstream>
+#include <string_view>
+#include <testsuite_hooks.h>
+
+int
+main()
+{
+  std::string s("This is a test");
+  std::istringstream stm(s);
+  VERIFY( stm.view() == s );
+  return 0;
+}
diff --git a/libstdc++-v3/testsuite/27_io/basic_istringstream/view/wchar_t/1.cc b/libstdc++-v3/testsuite/27_io/basic_istringstream/view/wchar_t/1.cc
new file mode 100644
index 00000000000..f6599643bd9
--- /dev/null
+++ b/libstdc++-v3/testsuite/27_io/basic_istringstream/view/wchar_t/1.cc
@@ -0,0 +1,35 @@ 
+// Copyright (C) 2020 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/>.
+
+// 27.7.1.1  basic_stringbuf constructors  [lib.stringbuf.cons]
+
+// { dg-options "-std=gnu++2a" }
+// { dg-do run { target c++2a } }
+// { dg-require-effective-target cxx11-abi }
+
+#include <sstream>
+#include <string_view>
+#include <testsuite_hooks.h>
+
+int
+main()
+{
+  std::wstring s(L"This is a test");
+  std::wistringstream stm(s);
+  VERIFY( stm.view() == s );
+  return 0;
+}
diff --git a/libstdc++-v3/testsuite/27_io/basic_ostringstream/cons/char/1.cc b/libstdc++-v3/testsuite/27_io/basic_ostringstream/cons/char/1.cc
new file mode 100644
index 00000000000..cba69f80931
--- /dev/null
+++ b/libstdc++-v3/testsuite/27_io/basic_ostringstream/cons/char/1.cc
@@ -0,0 +1,85 @@ 
+// Copyright (C) 2020 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/>.
+
+// C++20 29.8.2.2  basic_stringbuf constructors  [stringbuf.cons
+
+// { dg-options "-std=gnu++2a" }
+// { dg-do run { target c++2a } }
+// { dg-require-effective-target cxx11-abi }
+
+#include <sstream>
+#include <string>
+#include <testsuite_allocator.h>
+#include <testsuite_hooks.h>
+
+void
+test01()
+{
+  std::ostringstream::allocator_type a;
+  std::ostringstream stm(std::ios_base::in, a);
+}
+
+auto const cstr = "This is a test";
+
+void
+test02()
+{
+  std::string s1(cstr);
+  std::ostringstream stm(std::move(s1));
+  VERIFY( s1.empty() );
+
+  std::string s2(cstr);
+  VERIFY( stm.str() == s2 );
+}
+
+void
+test03()
+{
+  using alloc_type = __gnu_test::tracker_allocator<char>;
+  using str_type = std::basic_string<char, std::char_traits<char>, alloc_type>;
+
+  auto const mode = std::ios_base::out;
+  str_type s1(cstr);
+
+  {
+    std::ostringstream::allocator_type a;
+    std::ostringstream sbuf(s1, mode, a);
+    std::string s2(cstr);
+    VERIFY( sbuf.str() == s2 );
+  }
+
+  {
+    std::ostringstream sbuf(s1, mode);
+    std::string s2(cstr);
+    VERIFY( sbuf.str() == s2 );
+  }
+
+  {
+    std::ostringstream sbuf(s1);
+    std::string s2(cstr);
+    VERIFY( sbuf.str() == s2 );
+  }
+}
+
+int
+main()
+{
+  test01();
+  test02();
+  test03();
+  return 0;
+}
diff --git a/libstdc++-v3/testsuite/27_io/basic_ostringstream/cons/wchar_t/1.cc b/libstdc++-v3/testsuite/27_io/basic_ostringstream/cons/wchar_t/1.cc
new file mode 100644
index 00000000000..9021186d2c8
--- /dev/null
+++ b/libstdc++-v3/testsuite/27_io/basic_ostringstream/cons/wchar_t/1.cc
@@ -0,0 +1,85 @@ 
+// Copyright (C) 2020 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/>.
+
+// C++20 29.8.2.2  basic_stringbuf constructors  [stringbuf.cons
+
+// { dg-options "-std=gnu++2a" }
+// { dg-do run { target c++2a } }
+// { dg-require-effective-target cxx11-abi }
+
+#include <sstream>
+#include <string>
+#include <testsuite_allocator.h>
+#include <testsuite_hooks.h>
+
+void
+test01()
+{
+  std::wostringstream::allocator_type a;
+  std::wostringstream stm(std::ios_base::out, a);
+}
+
+auto const cstr = L"This is a test";
+
+void
+test02()
+{
+  std::wstring s1(cstr);
+  std::wostringstream stm(std::move(s1));
+  VERIFY( s1.empty() );
+
+  std::wstring s2(cstr);
+  VERIFY( stm.str() == s2 );
+}
+
+void
+test03()
+{
+  using alloc_type = __gnu_test::tracker_allocator<wchar_t>;
+  using str_type = std::basic_string<wchar_t, std::char_traits<wchar_t>, alloc_type>;
+
+  auto const mode = std::ios_base::out;
+  str_type s1(cstr);
+
+  {
+    std::wostringstream::allocator_type a;
+    std::wostringstream sbuf(s1, mode, a);
+    std::wstring s2(cstr);
+    VERIFY( sbuf.str() == s2 );
+  }
+
+  {
+    std::wostringstream sbuf(s1, mode);
+    std::wstring s2(cstr);
+    VERIFY( sbuf.str() == s2 );
+  }
+
+  {
+    std::wostringstream sbuf(s1);
+    std::wstring s2(cstr);
+    VERIFY( sbuf.str() == s2 );
+  }
+}
+
+int
+main()
+{
+  test01();
+  test02();
+  test03();
+  return 0;
+}
diff --git a/libstdc++-v3/testsuite/27_io/basic_ostringstream/view/char/1.cc b/libstdc++-v3/testsuite/27_io/basic_ostringstream/view/char/1.cc
new file mode 100644
index 00000000000..a366363abb5
--- /dev/null
+++ b/libstdc++-v3/testsuite/27_io/basic_ostringstream/view/char/1.cc
@@ -0,0 +1,35 @@ 
+// Copyright (C) 2020 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/>.
+
+// 27.7.1.1  basic_stringbuf constructors  [lib.stringbuf.cons]
+
+// { dg-options "-std=gnu++2a" }
+// { dg-do run { target c++2a } }
+// { dg-require-effective-target cxx11-abi }
+
+#include <sstream>
+#include <string_view>
+#include <testsuite_hooks.h>
+
+int
+main()
+{
+  std::string s("This is a test");
+  std::ostringstream stm(s);
+  VERIFY( stm.view() == s );
+  return 0;
+}
diff --git a/libstdc++-v3/testsuite/27_io/basic_ostringstream/view/wchar_t/1.cc b/libstdc++-v3/testsuite/27_io/basic_ostringstream/view/wchar_t/1.cc
new file mode 100644
index 00000000000..1ebf7c505e3
--- /dev/null
+++ b/libstdc++-v3/testsuite/27_io/basic_ostringstream/view/wchar_t/1.cc
@@ -0,0 +1,35 @@ 
+// Copyright (C) 2020 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/>.
+
+// 27.7.1.1  basic_stringbuf constructors  [lib.stringbuf.cons]
+
+// { dg-options "-std=gnu++2a" }
+// { dg-do run { target c++2a } }
+// { dg-require-effective-target cxx11-abi }
+
+#include <sstream>
+#include <string_view>
+#include <testsuite_hooks.h>
+
+int
+main()
+{
+  std::wstring s(L"This is a test");
+  std::wostringstream stm(s);
+  VERIFY( stm.view() == s );
+  return 0;
+}
diff --git a/libstdc++-v3/testsuite/27_io/basic_stringbuf/cons/char/2.cc b/libstdc++-v3/testsuite/27_io/basic_stringbuf/cons/char/2.cc
new file mode 100644
index 00000000000..ce669358c85
--- /dev/null
+++ b/libstdc++-v3/testsuite/27_io/basic_stringbuf/cons/char/2.cc
@@ -0,0 +1,121 @@ 
+// Copyright (C) 2020 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/>.
+
+// 27.7.1.1  basic_stringbuf constructors  [lib.stringbuf.cons]
+
+// { dg-options "-std=gnu++2a" }
+// { dg-do run { target c++2a } }
+// { dg-require-effective-target cxx11-abi }
+
+#include <sstream>
+#include <string>
+#include <testsuite_allocator.h>
+#include <testsuite_hooks.h>
+
+void
+test01()
+{
+  {
+    using alloc_type = __gnu_test::uneq_allocator<char>;
+    using sbuf_t = std::basic_stringbuf<char, std::char_traits<char>,
+						alloc_type>;
+
+    alloc_type aa;
+    sbuf_t sbuf1(aa);
+    VERIFY( aa == sbuf1.get_allocator() );
+
+    alloc_type aaa(42);
+    sbuf_t sbuf2(aaa);
+    VERIFY( aaa == sbuf2.get_allocator() );
+
+    VERIFY( sbuf1.get_allocator() != sbuf2.get_allocator() );
+  }
+
+  std::stringbuf::allocator_type a;
+  {
+    std::stringbuf sbuf(std::ios_base::in, a);
+  }
+
+  {
+    std::stringbuf sbuf(a);
+  }
+}
+
+auto const cstr = "This is a test";
+
+void
+test02()
+{
+  std::string s1(cstr);
+  std::stringbuf sbuf(std::move(s1));
+  VERIFY( s1.empty() );
+
+  std::string s2(cstr);
+  VERIFY( sbuf.str() == s2 );
+}
+
+void
+test03()
+{
+  using alloc_type = __gnu_test::tracker_allocator<char>;
+  using str_type = std::basic_string<char, std::char_traits<char>, alloc_type>;
+
+  auto const mode = std::ios_base::in | std::ios_base::out;
+  str_type s1(cstr);
+
+  {
+    std::stringbuf::allocator_type a;
+    std::stringbuf sbuf(s1, mode, a);
+    std::string s2(cstr);
+    VERIFY( sbuf.str() == s2 );
+  }
+
+  {
+    std::stringbuf sbuf(s1, mode);
+    std::string s2(cstr);
+    VERIFY( sbuf.str() == s2 );
+  }
+
+  {
+    std::stringbuf sbuf(s1);
+    std::string s2(cstr);
+    VERIFY( sbuf.str() == s2 );
+  }
+}
+
+void
+test04()
+{
+  std::stringbuf sbuf1(cstr);
+
+  std::stringbuf::allocator_type a;
+  std::stringbuf sbuf2(std::move(sbuf1), a);
+  VERIFY( sbuf1.str().empty() );
+
+  std::string s(cstr);
+  VERIFY( sbuf2.str() == s );
+}
+
+int
+main()
+{
+  test01();
+  test02();
+  test03();
+  test04();
+  return 0;
+}
diff --git a/libstdc++-v3/testsuite/27_io/basic_stringbuf/cons/wchar_t/2.cc b/libstdc++-v3/testsuite/27_io/basic_stringbuf/cons/wchar_t/2.cc
new file mode 100644
index 00000000000..e05acc42165
--- /dev/null
+++ b/libstdc++-v3/testsuite/27_io/basic_stringbuf/cons/wchar_t/2.cc
@@ -0,0 +1,105 @@ 
+// Copyright (C) 2020 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/>.
+
+// 27.7.1.1  basic_stringbuf constructors  [lib.stringbuf.cons]
+
+// { dg-options "-std=gnu++2a" }
+// { dg-do run { target c++2a } }
+// { dg-require-effective-target cxx11-abi }
+
+#include <sstream>
+#include <string>
+#include <testsuite_allocator.h>
+#include <testsuite_hooks.h>
+
+void
+test01()
+{
+  std::wstringbuf::allocator_type a;
+  {
+    std::wstringbuf sbuf(std::ios_base::in, a);
+  }
+
+  {
+    std::wstringbuf sbuf(a);
+  }
+}
+
+auto const cstr = L"This is a test";
+
+void
+test02()
+{
+  std::wstring s1(cstr);
+  std::wstringbuf sbuf(std::move(s1));
+  VERIFY( s1.empty() );
+
+  std::wstring s2(cstr);
+  VERIFY( sbuf.str() == s2 );
+}
+
+void
+test03()
+{
+  using alloc_type = __gnu_test::tracker_allocator<wchar_t>;
+  using str_type = std::basic_string<wchar_t, std::char_traits<wchar_t>, alloc_type>;
+
+  auto const mode = std::ios_base::in | std::ios_base::out;
+  str_type s1(cstr);
+
+  {
+    std::wstringbuf::allocator_type a;
+    std::wstringbuf sbuf(s1, mode, a);
+    std::wstring s2(cstr);
+    VERIFY( sbuf.str() == s2 );
+  }
+
+  {
+    std::wstringbuf sbuf(s1, mode);
+    std::wstring s2(cstr);
+    VERIFY( sbuf.str() == s2 );
+  }
+
+  {
+    std::wstringbuf sbuf(s1);
+    std::wstring s2(cstr);
+    VERIFY( sbuf.str() == s2 );
+  }
+}
+
+void
+test04()
+{
+  std::wstringbuf sbuf1(cstr);
+
+  std::wstringbuf::allocator_type a;
+  std::wstringbuf sbuf2(std::move(sbuf1), a);
+  VERIFY( sbuf1.str().empty() );
+
+  std::wstring s(cstr);
+  VERIFY( sbuf2.str() == s );
+}
+
+int
+main()
+{
+  test01();
+  test02();
+  test03();
+  test04();
+  return 0;
+}
diff --git a/libstdc++-v3/testsuite/27_io/basic_stringbuf/view/char/1.cc b/libstdc++-v3/testsuite/27_io/basic_stringbuf/view/char/1.cc
new file mode 100644
index 00000000000..8f8c62daa21
--- /dev/null
+++ b/libstdc++-v3/testsuite/27_io/basic_stringbuf/view/char/1.cc
@@ -0,0 +1,35 @@ 
+// Copyright (C) 2020 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/>.
+
+// 27.7.1.1  basic_stringbuf constructors  [lib.stringbuf.cons]
+
+// { dg-options "-std=gnu++2a" }
+// { dg-do run { target c++2a } }
+// { dg-require-effective-target cxx11-abi }
+
+#include <sstream>
+#include <string_view>
+#include <testsuite_hooks.h>
+
+int
+main()
+{
+  std::string s("This is a test");
+  std::stringbuf sbuf(s);
+  VERIFY( sbuf.view() == s );
+  return 0;
+}
diff --git a/libstdc++-v3/testsuite/27_io/basic_stringbuf/view/wchar_t/1.cc b/libstdc++-v3/testsuite/27_io/basic_stringbuf/view/wchar_t/1.cc
new file mode 100644
index 00000000000..0d23d7d8e66
--- /dev/null
+++ b/libstdc++-v3/testsuite/27_io/basic_stringbuf/view/wchar_t/1.cc
@@ -0,0 +1,35 @@ 
+// Copyright (C) 2020 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/>.
+
+// 27.7.1.1  basic_stringbuf constructors  [lib.stringbuf.cons]
+
+// { dg-options "-std=gnu++2a" }
+// { dg-do run { target c++2a } }
+// { dg-require-effective-target cxx11-abi }
+
+#include <sstream>
+#include <string_view>
+#include <testsuite_hooks.h>
+
+int
+main()
+{
+  std::wstring s(L"This is a test");
+  std::wstringbuf sbuf(s);
+  VERIFY( sbuf.view() == s );
+  return 0;
+}
diff --git a/libstdc++-v3/testsuite/27_io/basic_stringstream/cons/char/1.cc b/libstdc++-v3/testsuite/27_io/basic_stringstream/cons/char/1.cc
new file mode 100644
index 00000000000..83a3374b3cd
--- /dev/null
+++ b/libstdc++-v3/testsuite/27_io/basic_stringstream/cons/char/1.cc
@@ -0,0 +1,85 @@ 
+// Copyright (C) 2020 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/>.
+
+// C++20 29.8.2.2  basic_stringbuf constructors  [stringbuf.cons
+
+// { dg-options "-std=gnu++2a" }
+// { dg-do run { target c++2a } }
+// { dg-require-effective-target cxx11-abi }
+
+#include <sstream>
+#include <string>
+#include <testsuite_allocator.h>
+#include <testsuite_hooks.h>
+
+void
+test01()
+{
+  std::stringstream::allocator_type a;
+  std::stringstream stm(std::ios_base::in, a);
+}
+
+auto const cstr = "This is a test";
+
+void
+test02()
+{
+  std::string s1(cstr);
+  std::stringstream stm(std::move(s1));
+  VERIFY( s1.empty() );
+
+  std::string s2(cstr);
+  VERIFY( stm.str() == s2 );
+}
+
+void
+test03()
+{
+  using alloc_type = __gnu_test::tracker_allocator<char>;
+  using str_type = std::basic_string<char, std::char_traits<char>, alloc_type>;
+
+  auto const mode = std::ios_base::in | std::ios_base::out;
+  str_type s1(cstr);
+
+  {
+    std::stringstream::allocator_type a;
+    std::stringstream sbuf(s1, mode, a);
+    std::string s2(cstr);
+    VERIFY( sbuf.str() == s2 );
+  }
+
+  {
+    std::stringstream sbuf(s1, mode);
+    std::string s2(cstr);
+    VERIFY( sbuf.str() == s2 );
+  }
+
+  {
+    std::stringstream sbuf(s1);
+    std::string s2(cstr);
+    VERIFY( sbuf.str() == s2 );
+  }
+}
+
+int
+main()
+{
+  test01();
+  test02();
+  test03();
+  return 0;
+}
diff --git a/libstdc++-v3/testsuite/27_io/basic_stringstream/cons/wchar_t/1.cc b/libstdc++-v3/testsuite/27_io/basic_stringstream/cons/wchar_t/1.cc
new file mode 100644
index 00000000000..26a3a86c46e
--- /dev/null
+++ b/libstdc++-v3/testsuite/27_io/basic_stringstream/cons/wchar_t/1.cc
@@ -0,0 +1,85 @@ 
+// Copyright (C) 2020 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/>.
+
+// C++20 29.8.2.2  basic_stringbuf constructors  [stringbuf.cons
+
+// { dg-options "-std=gnu++2a" }
+// { dg-do run { target c++2a } }
+// { dg-require-effective-target cxx11-abi }
+
+#include <sstream>
+#include <string>
+#include <testsuite_allocator.h>
+#include <testsuite_hooks.h>
+
+void
+test01()
+{
+  std::wistringstream::allocator_type a;
+  std::wistringstream stm(std::ios_base::in, a);
+}
+
+auto const cstr = L"This is a test";
+
+void
+test02()
+{
+  std::wstring s1(cstr);
+  std::wistringstream stm(std::move(s1));
+  VERIFY( s1.empty() );
+
+  std::wstring s2(cstr);
+  VERIFY( stm.str() == s2 );
+}
+
+void
+test03()
+{
+  using alloc_type = __gnu_test::tracker_allocator<wchar_t>;
+  using str_type = std::basic_string<wchar_t, std::char_traits<wchar_t>, alloc_type>;
+
+  auto const mode = std::ios_base::in;
+  str_type s1(cstr);
+
+  {
+    std::wistringstream::allocator_type a;
+    std::wistringstream sbuf(s1, mode, a);
+    std::wstring s2(cstr);
+    VERIFY( sbuf.str() == s2 );
+  }
+
+  {
+    std::wistringstream sbuf(s1, mode);
+    std::wstring s2(cstr);
+    VERIFY( sbuf.str() == s2 );
+  }
+
+  {
+    std::wistringstream sbuf(s1);
+    std::wstring s2(cstr);
+    VERIFY( sbuf.str() == s2 );
+  }
+}
+
+int
+main()
+{
+  test01();
+  test02();
+  test03();
+  return 0;
+}
diff --git a/libstdc++-v3/testsuite/27_io/basic_stringstream/view/char/1.cc b/libstdc++-v3/testsuite/27_io/basic_stringstream/view/char/1.cc
new file mode 100644
index 00000000000..f47035cf148
--- /dev/null
+++ b/libstdc++-v3/testsuite/27_io/basic_stringstream/view/char/1.cc
@@ -0,0 +1,35 @@ 
+// Copyright (C) 2020 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/>.
+
+// 27.7.1.1  basic_stringbuf constructors  [lib.stringbuf.cons]
+
+// { dg-options "-std=gnu++2a" }
+// { dg-do run { target c++2a } }
+// { dg-require-effective-target cxx11-abi }
+
+#include <sstream>
+#include <string_view>
+#include <testsuite_hooks.h>
+
+int
+main()
+{
+  std::string s("This is a test");
+  std::stringstream stm(s);
+  VERIFY( stm.view() == s );
+  return 0;
+}
diff --git a/libstdc++-v3/testsuite/27_io/basic_stringstream/view/wchar_t/1.cc b/libstdc++-v3/testsuite/27_io/basic_stringstream/view/wchar_t/1.cc
new file mode 100644
index 00000000000..d707cfed243
--- /dev/null
+++ b/libstdc++-v3/testsuite/27_io/basic_stringstream/view/wchar_t/1.cc
@@ -0,0 +1,35 @@ 
+// Copyright (C) 2020 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/>.
+
+// 27.7.1.1  basic_stringbuf constructors  [lib.stringbuf.cons]
+
+// { dg-options "-std=gnu++2a" }
+// { dg-do run { target c++2a } }
+// { dg-require-effective-target cxx11-abi }
+
+#include <sstream>
+#include <string_view>
+#include <testsuite_hooks.h>
+
+int
+main()
+{
+  std::wstring s(L"This is a test");
+  std::wstringstream stm(s);
+  VERIFY( stm.view() == s );
+  return 0;
+}