Change in V4:
* Rename tests to string_view.cc
* Adapt tests to cons/wchar_t directories
* Define symbol __cpp_lib_sstream_from_string_view as 202406
* Define symbol __glibcxx_want_sstream_from_string_view before version.h
* Include version.h after other includes
* No include type_traits
* Drive-by comment moved to commit message
* Each `explicit` on its own line
* Run tests even when using old COW string
Change in V3:
* Comment that p2495 specifies a drive-by constraint omitted as redundant
* Adjust whitespace to fit in 80 columns
Change in V2:
* Apply all review comments
* Remove redundant drive-by "requires" on ctor from string allocator arg
* Check allocators are plumbed through
-- >8 --
Implement PR libstdc++/119741 (P2495R3).
Add constructors to stringbuf, stringstream, istringstream, and ostringstream,
and a matching overload of str(sv) in each, that take anything convertible to
a string_view in places where the existing ctors and function take a string.
Note this change omits the constraint applied to the istringstream constructor
from string cited as a "drive-by" in P2495R3, as we have determined it is
redundant.
libstdc++-v3/ChangeLog:
PR libstdc++/119741
* include/std/sstream: full implementation, really just
decls, requires clause and plumbing.
* include/bits/version.def, include/bits/version.h:
new preprocessor symbol
__cpp_lib_sstream_from_string_view.
* testsuite/27_io/basic_stringbuf/cons/char/string_view.cc:
New tests.
* testsuite/27_io/basic_istringstream/cons/char/string_view.cc:
New tests.
* testsuite/27_io/basic_ostringstream/cons/char/string_view.cc:
New tests.
* testsuite/27_io/basic_stringstream/cons/char/string_view.cc:
New tests.
* testsuite/27_io/basic_stringbuf/cons/wchar_t/string_view.cc:
New tests.
* testsuite/27_io/basic_istringstream/cons/wchar_t/string_view.cc:
New tests.
* testsuite/27_io/basic_ostringstream/cons/wchar_t/string_view.cc:
New tests.
* testsuite/27_io/basic_stringstream/cons/wchar_t/string_view.cc:
New tests.
---
libstdc++-v3/include/bits/version.def | 11 +-
libstdc++-v3/include/bits/version.h | 10 +
libstdc++-v3/include/std/sstream | 198 +++++++++++++++--
.../cons/char/string_view.cc | 195 +++++++++++++++++
.../cons/wchar_t/string_view.cc | 3 +
.../cons/char/string_view.cc | 194 +++++++++++++++++
.../cons/wchar_t/string_view.cc | 3 +
.../basic_stringbuf/cons/char/string_view.cc | 205 ++++++++++++++++++
.../cons/wchar_t/string_view.cc | 3 +
.../cons/char/string_view.cc | 204 +++++++++++++++++
.../cons/wchar_t/string_view.cc | 3 +
11 files changed, 1010 insertions(+), 19 deletions(-)
create mode 100644
libstdc++-v3/testsuite/27_io/basic_istringstream/cons/char/string_view.cc
create mode 100644
libstdc++-v3/testsuite/27_io/basic_istringstream/cons/wchar_t/string_view.cc
create mode 100644
libstdc++-v3/testsuite/27_io/basic_ostringstream/cons/char/string_view.cc
create mode 100644
libstdc++-v3/testsuite/27_io/basic_ostringstream/cons/wchar_t/string_view.cc
create mode 100644
libstdc++-v3/testsuite/27_io/basic_stringbuf/cons/char/string_view.cc
create mode 100644
libstdc++-v3/testsuite/27_io/basic_stringbuf/cons/wchar_t/string_view.cc
create mode 100644
libstdc++-v3/testsuite/27_io/basic_stringstream/cons/char/string_view.cc
create mode 100644
libstdc++-v3/testsuite/27_io/basic_stringstream/cons/wchar_t/string_view.cc
diff --git a/libstdc++-v3/include/bits/version.def
b/libstdc++-v3/include/bits/version.def
index 282667eabda..53bf72d95c2 100644
--- a/libstdc++-v3/include/bits/version.def
+++ b/libstdc++-v3/include/bits/version.def
@@ -649,7 +649,7 @@ ftms = {
};
values = {
v = 1;
- /* For when there's no gthread. */
+ // For when there is no gthread.
cxxmin = 17;
hosted = yes;
gthread = no;
@@ -1945,6 +1945,15 @@ ftms = {
};
};
+ftms = {
+ name = sstream_from_string_view;
+ values = {
+ v = 202306;
+ cxxmin = 26;
+ hosted = yes;
+ };
+};
+
// Standard test specifications.
stds[97] = ">= 199711L";
stds[03] = ">= 199711L";
diff --git a/libstdc++-v3/include/bits/version.h
b/libstdc++-v3/include/bits/version.h
index bb7c0479c72..0b932183e5b 100644
--- a/libstdc++-v3/include/bits/version.h
+++ b/libstdc++-v3/include/bits/version.h
@@ -2174,4 +2174,14 @@
#endif /* !defined(__cpp_lib_modules) && defined(__glibcxx_want_modules) */
#undef __glibcxx_want_modules
+#if !defined(__cpp_lib_sstream_from_string_view)
+# if (__cplusplus >= 202306L) && _GLIBCXX_HOSTED
+# define __glibcxx_sstream_from_string_view 202306L
+# if defined(__glibcxx_want_all) ||
defined(__glibcxx_want_sstream_from_string_view)
+# define __cpp_lib_sstream_from_string_view 202306L
+# endif
+# endif
+#endif /* !defined(__cpp_lib_sstream_from_string_view) &&
defined(__glibcxx_want_sstream_from_string_view) */
+#undef __glibcxx_want_sstream_from_string_view
+
#undef __glibcxx_want_all
diff --git a/libstdc++-v3/include/std/sstream b/libstdc++-v3/include/std/sstream
index ad0c16a91e8..edef599bd6f 100644
--- a/libstdc++-v3/include/std/sstream
+++ b/libstdc++-v3/include/std/sstream
@@ -41,8 +41,12 @@
#include <istream>
#include <ostream>
+
#include <bits/alloc_traits.h> // allocator_traits, __allocator_like
+#define __glibcxx_want_sstream_from_string_view
+#include <bits/version.h>
+
#if __cplusplus > 201703L && _GLIBCXX_USE_CXX11_ABI
# define _GLIBCXX_LVAL_REF_QUAL &
# define _GLIBCXX_SSTREAM_ALWAYS_INLINE
@@ -52,8 +56,6 @@
# define _GLIBCXX_SSTREAM_ALWAYS_INLINE [[__gnu__::__always_inline__]]
#endif
-
-
namespace std _GLIBCXX_VISIBILITY(default)
{
_GLIBCXX_BEGIN_NAMESPACE_VERSION
@@ -159,6 +161,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
{ __rhs._M_sync(const_cast<char_type*>(__rhs._M_string.data()), 0, 0); }
#if __cplusplus > 201703L && _GLIBCXX_USE_CXX11_ABI
+ // P0408 Efficient access to basic_stringbuf buffer
explicit
basic_stringbuf(const allocator_type& __a)
: basic_stringbuf(ios_base::in | std::ios_base::out, __a)
@@ -197,7 +200,36 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
| ios_base::out)
: basic_stringbuf(__s, __mode, allocator_type{})
{ }
+#endif
+
+#ifdef __cpp_lib_sstream_from_string_view
+ template<typename _Tp>
+ explicit
+ basic_stringbuf(const _Tp& __t,
+ ios_base::openmode __mode = ios_base::in | ios_base::out)
+ requires (is_convertible_v<const _Tp&,
+ basic_string_view<_CharT, _Traits>>)
+ : basic_stringbuf(__t, __mode, allocator_type{})
+ { }
+
+ template<typename _Tp>
+ basic_stringbuf(const _Tp& __t, const allocator_type& __a)
+ requires (is_convertible_v<const _Tp&,
+ basic_string_view<_CharT, _Traits>>)
+ : basic_stringbuf(__t, ios_base::in | ios_base::out, __a)
+ { }
+ template<typename _Tp>
+ basic_stringbuf(const _Tp& __t, ios_base::openmode __mode,
+ const allocator_type& __a)
+ requires (is_convertible_v<const _Tp&,
+ basic_string_view<_CharT, _Traits>>)
+ : _M_string(__t, __a)
+ { _M_stringbuf_init(__mode); }
+#endif // C++26
+
+#if __cplusplus > 201703L && _GLIBCXX_USE_CXX11_ABI
+ // P0408 Efficient access to basic_stringbuf buffer
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); }
@@ -262,6 +294,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
#if __cplusplus > 201703L
#if _GLIBCXX_USE_CXX11_ABI
#if __cpp_concepts
+ // P0407 Allocator-aware basic_streambuf
template<__allocator_like _SAlloc>
_GLIBCXX_NODISCARD
basic_string<_CharT, _Traits, _SAlloc>
@@ -317,6 +350,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
#if __cplusplus > 201703L && _GLIBCXX_USE_CXX11_ABI
#if __cpp_concepts
+ // P0407 Allocator-aware basic_streambuf
template<__allocator_like _SAlloc>
requires (!is_same_v<_SAlloc, _Alloc>)
void
@@ -335,6 +369,19 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
}
#endif
+#ifdef __cpp_lib_sstream_from_string_view
+ template <typename _Tp>
+ void
+ str(const _Tp& __t)
+ requires (is_convertible_v<const _Tp&,
+ basic_string_view<_CharT, _Traits>>)
+ {
+ basic_string_view<_CharT, _Traits> __sv{__t};
+ _M_string = __sv;
+ _M_stringbuf_init(_M_mode);
+ }
+#endif // C++26
+
protected:
// Common initialization code goes here.
void
@@ -521,6 +568,8 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
{ }
#if __cplusplus > 201703L && _GLIBCXX_USE_CXX11_ABI
+ // P0408 Efficient access to basic_stringbuf buffer
+
// 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,
@@ -584,7 +633,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
*/
basic_istringstream()
: __istream_type(), _M_stringbuf(ios_base::in)
- { this->init(&_M_stringbuf); }
+ { this->init(std::__addressof(_M_stringbuf)); }
/**
* @brief Starts with an empty string buffer.
@@ -601,7 +650,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
explicit
basic_istringstream(ios_base::openmode __mode)
: __istream_type(), _M_stringbuf(__mode | ios_base::in)
- { this->init(&_M_stringbuf); }
+ { this->init(std::__addressof(_M_stringbuf)); }
/**
* @brief Starts with an existing string buffer.
@@ -620,7 +669,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
basic_istringstream(const __string_type& __str,
ios_base::openmode __mode = ios_base::in)
: __istream_type(), _M_stringbuf(__str, __mode | ios_base::in)
- { this->init(&_M_stringbuf); }
+ { this->init(std::__addressof(_M_stringbuf)); }
/**
* @brief The destructor does nothing.
@@ -637,9 +686,10 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
basic_istringstream(basic_istringstream&& __rhs)
: __istream_type(std::move(__rhs)),
_M_stringbuf(std::move(__rhs._M_stringbuf))
- { __istream_type::set_rdbuf(&_M_stringbuf); }
+ { __istream_type::set_rdbuf(std::__addressof(_M_stringbuf)); }
#if __cplusplus > 201703L && _GLIBCXX_USE_CXX11_ABI
+ // P0408 Efficient access to basic_stringbuf buffer
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)); }
@@ -671,6 +721,32 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
{ }
#endif // C++20
+#ifdef __cpp_lib_sstream_from_string_view
+ template <typename _Tp>
+ explicit
+ basic_istringstream(const _Tp& __t,
+ ios_base::openmode __mode = ios_base::in)
+ requires (is_convertible_v<const _Tp&,
+ basic_string_view<_CharT, _Traits>>)
+ : basic_istringstream(__t, __mode, allocator_type{})
+ { }
+
+ template <typename _Tp>
+ basic_istringstream(const _Tp& __t, const allocator_type& __a)
+ requires (is_convertible_v<const _Tp&,
+ basic_string_view<_CharT, _Traits>>)
+ : basic_istringstream(__t, ios_base::in, __a)
+ { }
+
+ template <typename _Tp>
+ basic_istringstream(const _Tp& __t, ios_base::openmode __mode,
+ const allocator_type& __a)
+ requires (is_convertible_v<const _Tp&,
+ basic_string_view<_CharT, _Traits>>)
+ : __istream_type(), _M_stringbuf(__t, __mode | ios_base::in, __a)
+ { this->init(std::__addressof(_M_stringbuf)); }
+#endif // C++26
+
// 27.8.3.2 Assign and swap:
basic_istringstream&
@@ -702,7 +778,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
_GLIBCXX_NODISCARD
__stringbuf_type*
rdbuf() const
- { return const_cast<__stringbuf_type*>(&_M_stringbuf); }
+ { return const_cast<__stringbuf_type*>(std::__addressof(_M_stringbuf)); }
/**
* @brief Copying out the string buffer.
@@ -716,6 +792,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
#if __cplusplus > 201703L
#if _GLIBCXX_USE_CXX11_ABI
#if __cpp_concepts
+ // P0407 Allocator-aware basic_streambuf
template<__allocator_like _SAlloc>
_GLIBCXX_NODISCARD
basic_string<_CharT, _Traits, _SAlloc>
@@ -747,6 +824,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
#if __cplusplus > 201703L && _GLIBCXX_USE_CXX11_ABI
#if __cpp_concepts
+ // P0407 Allocator-aware basic_streambuf
template<__allocator_like _SAlloc>
requires (!is_same_v<_SAlloc, _Alloc>)
void
@@ -758,6 +836,15 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
str(__string_type&& __s)
{ _M_stringbuf.str(std::move(__s)); }
#endif
+
+#ifdef __cpp_lib_sstream_from_string_view
+ template<typename _Tp>
+ void
+ str(const _Tp& __t)
+ requires (is_convertible_v<const _Tp&,
+ basic_string_view<_CharT, _Traits>>)
+ { _M_stringbuf.str(__t); }
+#endif // C++26
};
@@ -812,7 +899,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
*/
basic_ostringstream()
: __ostream_type(), _M_stringbuf(ios_base::out)
- { this->init(&_M_stringbuf); }
+ { this->init(std::__addressof(_M_stringbuf)); }
/**
* @brief Starts with an empty string buffer.
@@ -829,7 +916,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
explicit
basic_ostringstream(ios_base::openmode __mode)
: __ostream_type(), _M_stringbuf(__mode | ios_base::out)
- { this->init(&_M_stringbuf); }
+ { this->init(std::__addressof(_M_stringbuf)); }
/**
* @brief Starts with an existing string buffer.
@@ -848,7 +935,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
basic_ostringstream(const __string_type& __str,
ios_base::openmode __mode = ios_base::out)
: __ostream_type(), _M_stringbuf(__str, __mode | ios_base::out)
- { this->init(&_M_stringbuf); }
+ { this->init(std::__addressof(_M_stringbuf)); }
/**
* @brief The destructor does nothing.
@@ -865,9 +952,10 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
basic_ostringstream(basic_ostringstream&& __rhs)
: __ostream_type(std::move(__rhs)),
_M_stringbuf(std::move(__rhs._M_stringbuf))
- { __ostream_type::set_rdbuf(&_M_stringbuf); }
+ { __ostream_type::set_rdbuf(std::__addressof(_M_stringbuf)); }
#if __cplusplus > 201703L && _GLIBCXX_USE_CXX11_ABI
+ // P0408 Efficient access to basic_stringbuf buffer
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)); }
@@ -899,6 +987,32 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
{ }
#endif // C++20
+#ifdef __cpp_lib_sstream_from_string_view
+ template <typename _Tp>
+ explicit
+ basic_ostringstream(
+ const _Tp& __t, ios_base::openmode __mode = ios_base::out)
+ requires (is_convertible_v<const _Tp&,
+ basic_string_view<_CharT, _Traits>>)
+ : basic_ostringstream(__t, __mode, allocator_type{})
+ { }
+
+ template <typename _Tp>
+ basic_ostringstream(const _Tp& __t, const allocator_type& __a)
+ requires (is_convertible_v<const _Tp&,
+ basic_string_view<_CharT, _Traits>>)
+ : basic_ostringstream(__t, ios_base::out, __a)
+ { }
+
+ template <typename _Tp>
+ basic_ostringstream(const _Tp& __t, ios_base::openmode __mode,
+ const allocator_type& __a)
+ requires (is_convertible_v<const _Tp&,
+ basic_string_view<_CharT, _Traits>>)
+ : __ostream_type(), _M_stringbuf(__t, __mode | ios_base::out, __a)
+ { this->init(std::__addressof(_M_stringbuf)); }
+#endif // C++26
+
// 27.8.3.2 Assign and swap:
basic_ostringstream&
@@ -930,7 +1044,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
_GLIBCXX_NODISCARD
__stringbuf_type*
rdbuf() const
- { return const_cast<__stringbuf_type*>(&_M_stringbuf); }
+ { return const_cast<__stringbuf_type*>(std::__addressof(_M_stringbuf)); }
/**
* @brief Copying out the string buffer.
@@ -944,6 +1058,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
#if __cplusplus > 201703L
#if _GLIBCXX_USE_CXX11_ABI
#if __cpp_concepts
+ // P0407 Allocator-aware basic_streambuf
template<__allocator_like _SAlloc>
_GLIBCXX_NODISCARD
basic_string<_CharT, _Traits, _SAlloc>
@@ -975,6 +1090,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
#if __cplusplus > 201703L && _GLIBCXX_USE_CXX11_ABI
#if __cpp_concepts
+ // P0407 Allocator-aware basic_streambuf
template<__allocator_like _SAlloc>
requires (!is_same_v<_SAlloc, _Alloc>)
void
@@ -986,6 +1102,15 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
str(__string_type&& __s)
{ _M_stringbuf.str(std::move(__s)); }
#endif
+
+#ifdef __cpp_lib_sstream_from_string_view
+ template<typename _Tp>
+ void
+ str(const _Tp& __t)
+ requires (is_convertible_v<const _Tp&,
+ basic_string_view<_CharT, _Traits>>)
+ { _M_stringbuf.str(__t); }
+#endif // C++26
};
@@ -1040,7 +1165,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
*/
basic_stringstream()
: __iostream_type(), _M_stringbuf(ios_base::out | ios_base::in)
- { this->init(&_M_stringbuf); }
+ { this->init(std::__addressof(_M_stringbuf)); }
/**
* @brief Starts with an empty string buffer.
@@ -1055,7 +1180,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
explicit
basic_stringstream(ios_base::openmode __m)
: __iostream_type(), _M_stringbuf(__m)
- { this->init(&_M_stringbuf); }
+ { this->init(std::__addressof(_M_stringbuf)); }
/**
* @brief Starts with an existing string buffer.
@@ -1072,7 +1197,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
basic_stringstream(const __string_type& __str,
ios_base::openmode __m = ios_base::out | ios_base::in)
: __iostream_type(), _M_stringbuf(__str, __m)
- { this->init(&_M_stringbuf); }
+ { this->init(std::__addressof(_M_stringbuf)); }
/**
* @brief The destructor does nothing.
@@ -1089,12 +1214,13 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
basic_stringstream(basic_stringstream&& __rhs)
: __iostream_type(std::move(__rhs)),
_M_stringbuf(std::move(__rhs._M_stringbuf))
- { __iostream_type::set_rdbuf(&_M_stringbuf); }
+ { __iostream_type::set_rdbuf(std::__addressof(_M_stringbuf)); }
#if __cplusplus > 201703L && _GLIBCXX_USE_CXX11_ABI
+ // P0408 Efficient access to basic_stringbuf buffer
basic_stringstream(ios_base::openmode __mode, const allocator_type& __a)
: __iostream_type(), _M_stringbuf(__mode, __a)
- { this->init(&_M_stringbuf); }
+ { this->init(std::__addressof(_M_stringbuf)); }
explicit
basic_stringstream(__string_type&& __str,
@@ -1125,6 +1251,31 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
{ }
#endif // C++20
+#ifdef __cpp_lib_sstream_from_string_view
+ template <typename _Tp>
+ explicit
+ basic_stringstream(const _Tp& __t,
+ ios_base::openmode __mode = ios_base::in | ios_base::out)
+ requires (is_convertible_v<const _Tp&,
+ basic_string_view<_CharT, _Traits>>)
+ : basic_stringstream(__t, __mode, allocator_type{})
+ { }
+
+ template <typename _Tp>
+ basic_stringstream(const _Tp& __t, const allocator_type& __a)
+ requires (is_convertible_v<const _Tp&,
+ basic_string_view<_CharT, _Traits>>)
+ : basic_stringstream(__t, ios_base::in | ios_base::out, __a)
+ { }
+
+ template <typename _Tp>
+ basic_stringstream(const _Tp& __t, ios_base::openmode __mode,
+ const allocator_type& __a)
+ requires (is_convertible_v<const _Tp&, basic_string_view<_CharT,
_Traits>>)
+ : __iostream_type(), _M_stringbuf(__t, __mode, __a)
+ { this->init(std::__addressof(_M_stringbuf)); }
+#endif // C++26
+
// 27.8.3.2 Assign and swap:
basic_stringstream&
@@ -1156,7 +1307,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
_GLIBCXX_NODISCARD
__stringbuf_type*
rdbuf() const
- { return const_cast<__stringbuf_type*>(&_M_stringbuf); }
+ { return const_cast<__stringbuf_type*>(std::__addressof(_M_stringbuf)); }
/**
* @brief Copying out the string buffer.
@@ -1170,6 +1321,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
#if __cplusplus > 201703L
#if _GLIBCXX_USE_CXX11_ABI
#if __cpp_concepts
+ // P0407 Allocator-aware basic_streambuf
template<__allocator_like _SAlloc>
_GLIBCXX_NODISCARD
basic_string<_CharT, _Traits, _SAlloc>
@@ -1201,6 +1353,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
#if __cplusplus > 201703L && _GLIBCXX_USE_CXX11_ABI
#if __cpp_concepts
+ // P0407 Allocator-aware basic_streambuf
template<__allocator_like _SAlloc>
requires (!is_same_v<_SAlloc, _Alloc>)
void
@@ -1212,6 +1365,15 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
str(__string_type&& __s)
{ _M_stringbuf.str(std::move(__s)); }
#endif
+
+#ifdef __cpp_lib_sstream_from_string_view
+ template<typename _Tp>
+ void
+ str(const _Tp& __t)
+ requires (is_convertible_v<const _Tp&,
+ basic_string_view<_CharT, _Traits>>)
+ { _M_stringbuf.str(__t); }
+#endif // C++26
};
#if __cplusplus >= 201103L
diff --git
a/libstdc++-v3/testsuite/27_io/basic_istringstream/cons/char/string_view.cc
b/libstdc++-v3/testsuite/27_io/basic_istringstream/cons/char/string_view.cc
new file mode 100644
index 00000000000..27f65aa9437
--- /dev/null
+++ b/libstdc++-v3/testsuite/27_io/basic_istringstream/cons/char/string_view.cc
@@ -0,0 +1,195 @@
+// C++26 [istringstream.general]
+
+// { dg-do run { target c++26 } }
+
+#include <sstream>
+#include <string>
+#include <string_view>
+#include <testsuite_allocator.h>
+#include <testsuite_hooks.h>
+
+// Check C++26 P2495 istringstream ctors and members str(s) that accept a
+// string_view, or anything convertible to a string_view, in place of a
+// string object. Mostly just verify plumbing.
+
+#ifndef C
+# define C char
+# define L(a) a
+#endif
+
+using string = std::basic_string<C>;
+using string_view = std::basic_string_view<C>;
+using istringstream = std::basic_istringstream<C>;
+
+struct convertible_to_string_view {
+ string s;
+ operator string_view() const { return s; }
+};
+
+const string str(L("This is a test string"));
+convertible_to_string_view cstr{str}; // a copy
+const convertible_to_string_view ccstr{str}; // another copy
+
+template <typename istringstream = std::basic_istringstream<C>>
+void
+test01()
+{
+ // Test C++26 constructor and str(s) taking a generalized string_view
+
+ static_assert(! requires { istringstream(1); },
+ "istringstream ctor should reject what cannot be converted to a
string_view");
+ static_assert(! requires { istringstream().str(1); },
+ "istringstream::str(s) should reject what cannot be converted to a
string_view");
+
+ static_assert(!std::is_convertible_v<string_view, istringstream>,
+ "istringstream(string_view, ios::openmode) is explicit");
+ static_assert(!std::is_convertible_v<const string_view, istringstream>,
+ "istringstream(string_view, ios::openmode) is explicit");
+ static_assert(!std::is_convertible_v<convertible_to_string_view,
istringstream>,
+ "istringstream(convertible_to_string_view, ios::openmode) is explicit");
+ static_assert(!std::is_convertible_v<const convertible_to_string_view,
istringstream>,
+ "istringstream(convertible_to_string_view, ios::openmode) is explicit");
+
+ {
+ istringstream istr(cstr);
+ VERIFY( istr.str() == cstr.s );
+ VERIFY( istr.get() == cstr.s[0] );
+ }
+ {
+ istringstream istr(ccstr);
+ VERIFY( istr.str() == ccstr.s );
+ VERIFY( istr.get() == ccstr.s[0] );
+ }
+ {
+ istringstream istr(cstr, std::ios_base::in);
+ VERIFY( istr.str() == cstr.s );
+ VERIFY( istr.get() == cstr.s[0] );
+ VERIFY( istr.rdbuf()->sputc('X') != 'X' );
+ }
+ {
+ istringstream istr(cstr, std::ios_base::out);
+ VERIFY( istr.str() == cstr.s );
+ VERIFY( istr.get() == cstr.s[0] );
+ VERIFY( istr.rdbuf()->sputc('X') == 'X' );
+ }
+}
+
+void
+test02()
+{
+ // Test various C++26 constructors taking string views
+ // and mix of other arguments
+
+ auto const mode = std::ios_base::in | std::ios_base::out;
+
+ {
+ // template <typename T>
+ // basic_istringstream(const T&, ios_base::openmode, const allocator_type&)
+
+ istringstream::allocator_type a;
+ {
+ istringstream istr(cstr, mode, a); // ={} checks for non-explicit ctor
+ VERIFY( istr.str() == cstr.s );
+ }
+ {
+ istringstream istr(cstr, std::ios::in, a);
+ VERIFY( istr.str() == cstr.s );
+ VERIFY( istr.get() == cstr.s[0] );
+ VERIFY( istr.rdbuf()->sputc('X') != 'X' );
+ }
+ {
+ istringstream istr(cstr, std::ios::out, a);
+ VERIFY( istr.str() == cstr.s );
+ VERIFY( istr.get() == cstr.s[0] );
+ VERIFY( istr.rdbuf()->sputc('X') == 'X' );
+ }
+ }
+
+ {
+ // template <typename T>
+ // basic_istringstream(const T&, ios_base::openmode)
+ {
+ istringstream istr(cstr, mode);
+ VERIFY( istr.str() == cstr.s );
+ VERIFY( istr.get() == cstr.s[0] );
+ VERIFY( istr.rdbuf()->sputc('X') == 'X' );
+ }
+ {
+ istringstream istr(cstr, std::ios::in);
+ VERIFY( istr.str() == cstr.s );
+ VERIFY( istr.get() == cstr.s[0] );
+ VERIFY( istr.rdbuf()->sputc('X') != 'X' );
+ }
+ {
+ istringstream istr(cstr, std::ios::out);
+ VERIFY( istr.str() == cstr.s );
+ VERIFY( istr.get() == cstr.s[0] );
+ VERIFY( istr.rdbuf()->sputc('X') == 'X' );
+ }
+ }
+
+ {
+ // template <typename T>
+ // explicit
+ // basic_istringstream(const T&, ios_base::openmode = ios_base::in)
+
+ istringstream istr(cstr);
+ VERIFY( istr.str() == cstr.s );
+ VERIFY( istr.get() == cstr.s[0] );
+ VERIFY( istr.rdbuf()->sputc('X') != 'X' );
+ }
+}
+
+using alloc_type = __gnu_test::uneq_allocator<C>;
+
+template<typename Alloc, typename CC = typename Alloc::value_type>
+ using istringstream_with_alloc
+ = std::basic_istringstream<CC, std::char_traits<CC>, Alloc>;
+
+void test03()
+{
+ alloc_type a{1};
+ {
+ istringstream_with_alloc<alloc_type> istr(cstr, a);
+ VERIFY( istr.rdbuf()->get_allocator() == a );
+ VERIFY( string_view{istr.str()} == cstr );
+ VERIFY( istr.get() == cstr.s[0] );
+ }
+ {
+ istringstream_with_alloc<alloc_type> istr(cstr, std::ios::in, a);
+ VERIFY( istr.rdbuf()->get_allocator() == a );
+ VERIFY( string_view{istr.str()} == cstr );
+ VERIFY( istr.get() == cstr.s[0] );
+ VERIFY( istr.rdbuf()->sputc('X') != 'X' );
+ }
+ {
+ istringstream_with_alloc<alloc_type> istr(cstr, std::ios::out, a);
+ VERIFY( istr.rdbuf()->get_allocator() == a );
+ VERIFY( string_view{istr.str()} == cstr );
+ VERIFY( istr.get() == cstr.s[0] );
+ VERIFY( istr.rdbuf()->sputc('X') == 'X' );
+ }
+}
+
+void test04()
+{
+ {
+ istringstream istr;
+ istr.str( cstr );
+ VERIFY( istr.str() == cstr.s );
+ }
+ {
+ istringstream istr;
+ istr.str( ccstr );
+ VERIFY( istr.str() == ccstr.s );
+ }
+}
+
+int
+main()
+{
+ test01();
+ test02();
+ test03();
+ test04();
+}
diff --git
a/libstdc++-v3/testsuite/27_io/basic_istringstream/cons/wchar_t/string_view.cc
b/libstdc++-v3/testsuite/27_io/basic_istringstream/cons/wchar_t/string_view.cc
new file mode 100644
index 00000000000..cfb73c4c510
--- /dev/null
+++
b/libstdc++-v3/testsuite/27_io/basic_istringstream/cons/wchar_t/string_view.cc
@@ -0,0 +1,3 @@
+#define C wchar_t
+#define L(a) L##a
+#include "../char/string_view.cc"
diff --git
a/libstdc++-v3/testsuite/27_io/basic_ostringstream/cons/char/string_view.cc
b/libstdc++-v3/testsuite/27_io/basic_ostringstream/cons/char/string_view.cc
new file mode 100644
index 00000000000..731e97e4aa2
--- /dev/null
+++ b/libstdc++-v3/testsuite/27_io/basic_ostringstream/cons/char/string_view.cc
@@ -0,0 +1,194 @@
+// C++26 [ostringstream.general]
+
+// { dg-do run { target c++26 } }
+
+#include <sstream>
+#include <string>
+#include <string_view>
+#include <testsuite_allocator.h>
+#include <testsuite_hooks.h>
+
+// Check C++26 P2495 ostringstream ctors and members str(s) that accept a
+// string_view, or anything convertible to a string_view, in place of a
+// string object. Mostly just verify plumbing.
+
+#ifndef C
+# define C char
+# define L(a) a
+#endif
+
+using string = std::basic_string<C>;
+using string_view = std::basic_string_view<C>;
+using ostringstream = std::basic_ostringstream<C>;
+
+struct convertible_to_string_view {
+ string s;
+ operator string_view() const { return s; }
+};
+
+const string str(L("This is a test string"));
+convertible_to_string_view cstr{str}; // a copy
+const convertible_to_string_view ccstr{str}; // another copy
+
+template <typename ostringstream = std::basic_ostringstream<C>>
+void
+test01()
+{
+ // Test C++26 constructor and str(s) taking a generalized string_view
+
+ static_assert(! requires { ostringstream(1); },
+ "ostringstream ctor should reject what cannot be converted to a
string_view");
+ static_assert(! requires { ostringstream().str(1); },
+ "ostringstream::str(s) should reject what cannot be converted to a
string_view");
+
+ static_assert(!std::is_convertible_v<string_view, ostringstream>,
+ "ostringstream(string_view, ios::openmode) is explicit");
+ static_assert(!std::is_convertible_v<const string_view, ostringstream>,
+ "ostringstream(string_view, ios::openmode) is explicit");
+ static_assert(!std::is_convertible_v<convertible_to_string_view,
ostringstream>,
+ "ostringstream(convertible_to_string_view, ios::openmode) is explicit");
+ static_assert(!std::is_convertible_v<const convertible_to_string_view,
ostringstream>,
+ "ostringstream(convertible_to_string_view, ios::openmode) is explicit");
+
+ {
+ ostringstream ostrstr(cstr);
+ VERIFY( ostrstr.str() == cstr.s );
+ VERIFY( ostrstr.rdbuf()->sgetc() == ostringstream::traits_type::eof() );
+ }
+ {
+ ostringstream ostrstr(ccstr);
+ VERIFY( ostrstr.str() == ccstr.s );
+ VERIFY( ostrstr.rdbuf()->sgetc() == ostringstream::traits_type::eof() );
+ }
+ {
+ ostringstream ostrstr(cstr, std::ios_base::in);
+ VERIFY( ostrstr.str() == cstr.s );
+ VERIFY( ostrstr.rdbuf()->sgetc() == cstr.s[0]);
+ VERIFY( ostrstr.put('Y').rdstate() == ostrstr.goodbit );
+ }
+ {
+ ostringstream ostrstr(cstr, std::ios_base::out);
+ VERIFY( ostrstr.str() == cstr.s );
+ VERIFY( ostrstr.rdbuf()->sgetc() == ostringstream::traits_type::eof() );
+ VERIFY( ostrstr.put('Y').rdstate() == ostrstr.goodbit );
+ }
+}
+
+void
+test02()
+{
+ // Test plumbing of C++26 various constructors taking string views
+
+ auto const mode = std::ios_base::in | std::ios_base::out;
+
+ {
+ ostringstream::allocator_type a;
+ // template <typename T>
+ // basic_ostringstream(const T&, ios_base::openmode, const allocator_type&)
+ {
+ ostringstream ostrstr(cstr, mode, a); // ={} checks for non-explicit ctor
+ VERIFY( ostrstr.str() == cstr.s );
+ }
+ {
+ ostringstream ostrstr(cstr, std::ios::in, a);
+ VERIFY( ostrstr.str() == cstr.s );
+ VERIFY( ostrstr.rdbuf()->sgetc() == cstr.s[0]);
+ VERIFY( ostrstr.put('Y').rdstate() == ostrstr.goodbit );
+ }
+ {
+ ostringstream ostrstr(cstr, std::ios::out, a);
+ VERIFY( ostrstr.str() == cstr.s );
+ VERIFY( ostrstr.rdbuf()->sgetc() == ostringstream::traits_type::eof() );
+ VERIFY( ostrstr.put('Y').rdstate() == ostrstr.goodbit );
+ }
+ }
+
+ {
+ // template <typename T>
+ // basic_ostringstream(const T&, ios_base::openmode)
+ {
+ ostringstream ostrstr(cstr, mode);
+ VERIFY( ostrstr.str() == cstr.s );
+ VERIFY( ostrstr.rdbuf()->sgetc() == cstr.s[0]);
+ VERIFY( ostrstr.put('Y').good() );
+ }
+ {
+ ostringstream ostrstr(cstr, std::ios::in);
+ VERIFY( ostrstr.str() == cstr.s );
+ VERIFY( ostrstr.rdbuf()->sgetc() == cstr.s[0]);
+ VERIFY( ostrstr.put('X').good() );
+ }
+ {
+ ostringstream ostrstr(cstr, std::ios::out);
+ VERIFY( ostrstr.str() == cstr.s );
+ VERIFY( ostrstr.rdbuf()->sgetc() == ostringstream::traits_type::eof() );
+ VERIFY( ostrstr.put('Y').rdstate() == ostrstr.goodbit );
+ }
+ }
+
+ {
+ // template <typename T>
+ // explicit
+ // basic_ostringstream(const T&, ios_base::openmode = ios_base::out)
+
+ ostringstream ostrstr(cstr);
+ VERIFY( ostrstr.str() == cstr.s );
+ VERIFY( ostrstr.rdbuf()->sgetc() == ostringstream::traits_type::eof() );
+ VERIFY( ostrstr.put('Y').good() );
+ }
+}
+
+using alloc_type = __gnu_test::uneq_allocator<C>;
+
+template<typename Alloc, typename CC = typename Alloc::value_type>
+ using ostringstream_with_alloc
+ = std::basic_ostringstream<CC, std::char_traits<CC>, Alloc>;
+
+void test03()
+{
+ alloc_type a{1};
+ {
+ ostringstream_with_alloc<alloc_type> ostrstr(cstr, a);
+ VERIFY( ostrstr.rdbuf()->get_allocator() == a );
+ VERIFY( string_view{ostrstr.str()} == cstr );
+ VERIFY( ostrstr.rdbuf()->sgetc() == ostringstream::traits_type::eof() );
+ VERIFY( ostrstr.put('X').good() );
+ }
+ {
+ ostringstream_with_alloc<alloc_type> ostrstr(cstr, std::ios::in, a);
+ VERIFY( ostrstr.rdbuf()->get_allocator() == a );
+ VERIFY( string_view{ostrstr.str()} == cstr );
+ VERIFY( ostrstr.rdbuf()->sgetc() == cstr.s[0]);
+ VERIFY( ostrstr.put('X').good() );
+ }
+ {
+ ostringstream_with_alloc<alloc_type> ostrstr(cstr, std::ios::out, a);
+ VERIFY( ostrstr.rdbuf()->get_allocator() == a );
+ VERIFY( string_view{ostrstr.str()} == cstr );
+ VERIFY( ostrstr.rdbuf()->sgetc() == ostringstream::traits_type::eof() );
+ VERIFY( ostrstr.put('Y').rdstate() == ostrstr.goodbit );
+ }
+}
+
+void test04()
+{
+ {
+ ostringstream ostrstr;
+ ostrstr.str(cstr);
+ VERIFY( ostrstr.str() == cstr.s );
+ }
+ {
+ ostringstream ostrstr;
+ ostrstr.str(ccstr);
+ VERIFY( ostrstr.str() == ccstr.s );
+ }
+}
+
+int
+main()
+{
+ test01();
+ test02();
+ test03();
+ test04();
+}
diff --git
a/libstdc++-v3/testsuite/27_io/basic_ostringstream/cons/wchar_t/string_view.cc
b/libstdc++-v3/testsuite/27_io/basic_ostringstream/cons/wchar_t/string_view.cc
new file mode 100644
index 00000000000..cfb73c4c510
--- /dev/null
+++
b/libstdc++-v3/testsuite/27_io/basic_ostringstream/cons/wchar_t/string_view.cc
@@ -0,0 +1,3 @@
+#define C wchar_t
+#define L(a) L##a
+#include "../char/string_view.cc"
diff --git
a/libstdc++-v3/testsuite/27_io/basic_stringbuf/cons/char/string_view.cc
b/libstdc++-v3/testsuite/27_io/basic_stringbuf/cons/char/string_view.cc
new file mode 100644
index 00000000000..7843269c48f
--- /dev/null
+++ b/libstdc++-v3/testsuite/27_io/basic_stringbuf/cons/char/string_view.cc
@@ -0,0 +1,205 @@
+// C++26 31.8.2.1 [stringbuf.general]
+
+// { dg-do run { target c++26 } }
+
+#include <sstream>
+#include <string>
+#include <string_view>
+#include <testsuite_allocator.h>
+#include <testsuite_hooks.h>
+
+// Check C++26 P2495 stringbuf ctors and members str(s) that accept a
+// string_view, or anything convertible to a string_view, in place of a
+// string object.
+
+#ifndef C
+# define C char
+# define L(a) a
+#endif
+
+using string = std::basic_string<C>;
+using string_view = std::basic_string_view<C>;
+using stringbuf = std::basic_stringbuf<C>;
+
+struct convertible_to_string_view {
+ string s;
+ operator string_view() const { return s; }
+};
+
+const string str(L("This is a test string"));
+convertible_to_string_view cstr{str}; // a copy
+const convertible_to_string_view ccstr{str}; // another copy
+
+template <typename stringbuf = std::basic_stringbuf<C>>
+void
+test01()
+{
+ // Test C++26 constructor and str(s) taking a generalized string_view
+
+ static_assert(! requires { stringbuf(1); },
+ "stringbuf ctor should reject what cannot be converted to a
string_view");
+ static_assert(! requires { stringbuf().str(1); },
+ "stringbuf::str(s) should reject what cannot be converted to a
string_view");
+
+ static_assert(!std::is_convertible_v<string_view, stringbuf>,
+ "stringbuf(string_view, ios::openmode) is explicit");
+ static_assert(!std::is_convertible_v<const string_view, stringbuf>,
+ "stringbuf(string_view, ios::openmode) is explicit");
+ static_assert(!std::is_convertible_v<convertible_to_string_view, stringbuf>,
+ "stringbuf(convertible_to_string_view, ios::openmode) is explicit");
+ static_assert(
+ !std::is_convertible_v<const convertible_to_string_view, stringbuf>,
+ "stringbuf(convertible_to_string_view, ios::openmode) is explicit");
+
+ {
+ stringbuf sbuf(cstr);
+ VERIFY( sbuf.str() == cstr.s );
+ VERIFY( sbuf.sgetc() == cstr.s[0] );
+ }
+ {
+ stringbuf sbuf(ccstr);
+ VERIFY( sbuf.str() == ccstr.s );
+ VERIFY( sbuf.sgetc() == ccstr.s[0] );
+ }
+ {
+ stringbuf sbuf(cstr, std::ios_base::in);
+ VERIFY( sbuf.str() == cstr.s );
+ VERIFY( sbuf.sgetc() == cstr.s[0] );
+ VERIFY( sbuf.sputc('X') == stringbuf::traits_type::eof() );
+ }
+ {
+ stringbuf sbuf(ccstr, std::ios_base::in);
+ VERIFY( sbuf.str() == ccstr.s );
+ VERIFY( sbuf.sgetc() == ccstr.s[0] );
+ VERIFY( sbuf.sputc('X') == stringbuf::traits_type::eof() );
+ }
+ {
+ stringbuf sbuf(cstr, std::ios_base::out);
+ VERIFY( sbuf.str() == cstr.s );
+ VERIFY( sbuf.sputc('Y') == 'Y' );
+ VERIFY( sbuf.sgetc() == stringbuf::traits_type::eof() );
+ }
+ {
+ stringbuf sbuf(ccstr, std::ios_base::out);
+ VERIFY( sbuf.str() == ccstr.s );
+ VERIFY( sbuf.sputc('Y') == 'Y' );
+ VERIFY( sbuf.sgetc() == stringbuf::traits_type::eof() );
+ }
+}
+
+void
+test02()
+{
+ // Test C++26 constructors taking string views using different allocators
+
+ auto const mode = std::ios_base::in | std::ios_base::out;
+
+ {
+ // template <typename T>
+ // basic_stringbuf(const T&, ios_base::openmode, const allocator_type&)
+
+ stringbuf::allocator_type a;
+ {
+ stringbuf sbuf(cstr, mode, a); // ={} checks for non-explicit ctor
+ VERIFY( sbuf.str() == cstr.s );
+ }
+ {
+ stringbuf sbuf(cstr, std::ios::in, a);
+ VERIFY( sbuf.str() == cstr.s );
+ VERIFY( sbuf.sgetc() == cstr.s[0] );
+ VERIFY( sbuf.sputc('X') == stringbuf::traits_type::eof() );
+ }
+
+ {
+ stringbuf sbuf(cstr, std::ios::out, a);
+ VERIFY( sbuf.str() == cstr.s );
+ VERIFY( sbuf.sputc('X') == 'X' );
+ VERIFY( sbuf.sgetc() == stringbuf::traits_type::eof() );
+ }
+ }
+
+ {
+ // template <typename T>
+ // basic_stringbuf(const T&, ios_base::openmode)
+ {
+ stringbuf sbuf(cstr, mode);
+ VERIFY( sbuf.str() == cstr.s );
+ }
+ {
+ stringbuf sbuf(cstr, std::ios::in);
+ VERIFY( sbuf.str() == cstr.s );
+ VERIFY( sbuf.sgetc() == cstr.s[0] );
+ VERIFY( sbuf.sputc('X') == stringbuf::traits_type::eof() );
+ }
+ {
+ stringbuf sbuf(cstr, std::ios::out);
+ VERIFY( sbuf.str() == cstr.s );
+ VERIFY( sbuf.sputc('X') == 'X' );
+ VERIFY( sbuf.sgetc() == stringbuf::traits_type::eof() );
+ }
+ }
+
+ {
+ // template <typename T>
+ // explicit
+ // basic_stringbuf(const T&, ios_base::openmode =
ios_base::in|ios_base::out)
+
+ stringbuf sbuf(cstr);
+ VERIFY( sbuf.str() == cstr.s );
+ VERIFY( sbuf.sgetc() == cstr.s[0] );
+ }
+}
+
+using alloc_type = __gnu_test::uneq_allocator<C>;
+
+template<typename Alloc, typename CC = typename Alloc::value_type>
+ using stringbuf_with_alloc
+ = std::basic_stringbuf<CC, std::char_traits<CC>, Alloc>;
+
+void test03()
+{
+ alloc_type a{1};
+ {
+ stringbuf_with_alloc<alloc_type> sbuf(cstr, a);
+ VERIFY( sbuf.get_allocator() == a );
+ VERIFY( string_view{sbuf.str()} == cstr );
+ VERIFY( sbuf.sgetc() == cstr.s[0] );
+ }
+ {
+ stringbuf_with_alloc<alloc_type> sbuf(cstr, std::ios::in, a);
+ VERIFY( sbuf.get_allocator() == a );
+ VERIFY( string_view{sbuf.str()} == cstr );
+ VERIFY( sbuf.sgetc() == cstr.s[0] );
+ VERIFY( sbuf.sputc('X') == stringbuf::traits_type::eof() );
+ }
+ {
+ stringbuf_with_alloc<alloc_type> sbuf(cstr, std::ios::out, a);
+ VERIFY( sbuf.get_allocator() == a );
+ VERIFY( string_view{sbuf.str()} == cstr );
+ VERIFY( sbuf.sputc('X') == 'X' );
+ VERIFY( sbuf.sgetc() == stringbuf::traits_type::eof() );
+ }
+}
+
+void test04()
+{
+ {
+ stringbuf sbuf;
+ sbuf.str(cstr);
+ VERIFY( sbuf.str() == cstr.s );
+ }
+ {
+ stringbuf sbuf;
+ sbuf.str(ccstr);
+ VERIFY( sbuf.str() == ccstr.s );
+ }
+}
+
+int
+main()
+{
+ test01();
+ test02();
+ test03();
+ test04();
+}
diff --git
a/libstdc++-v3/testsuite/27_io/basic_stringbuf/cons/wchar_t/string_view.cc
b/libstdc++-v3/testsuite/27_io/basic_stringbuf/cons/wchar_t/string_view.cc
new file mode 100644
index 00000000000..cfb73c4c510
--- /dev/null
+++ b/libstdc++-v3/testsuite/27_io/basic_stringbuf/cons/wchar_t/string_view.cc
@@ -0,0 +1,3 @@
+#define C wchar_t
+#define L(a) L##a
+#include "../char/string_view.cc"
diff --git
a/libstdc++-v3/testsuite/27_io/basic_stringstream/cons/char/string_view.cc
b/libstdc++-v3/testsuite/27_io/basic_stringstream/cons/char/string_view.cc
new file mode 100644
index 00000000000..72085230442
--- /dev/null
+++ b/libstdc++-v3/testsuite/27_io/basic_stringstream/cons/char/string_view.cc
@@ -0,0 +1,204 @@
+// C++26 31.8.2.1 [stringstream.general]
+
+// { dg-do run { target c++26 } }
+
+#include <sstream>
+#include <string>
+#include <string_view>
+#include <testsuite_allocator.h>
+#include <testsuite_hooks.h>
+
+// Check C++26 P2495 stringstream ctors and members str(s) that accept a
+// string_view, or anything convertible to a string_view, in place of a
+// string object. Mostly just verify plumbing.
+
+#ifndef C
+# define C char
+# define L(a) a
+#endif
+
+using string = std::basic_string<C>;
+using string_view = std::basic_string_view<C>;
+using stringstream = std::basic_stringstream<C>;
+
+struct convertible_to_string_view {
+ string s;
+ operator string_view() const { return s; }
+};
+
+const string str(L("This is a test string"));
+convertible_to_string_view cstr{str}; // a copy
+const convertible_to_string_view ccstr{str}; // another copy
+
+template <typename stringstream = std::basic_stringstream<C>>
+void
+test01()
+{
+ // Test C++26 constructor and str(s) taking a generalized string_view
+
+ static_assert(! requires { stringstream(1); },
+ "stringstream ctor should reject what cannot be converted to a
string_view");
+ static_assert(! requires { stringstream().str(1); },
+ "stringstream::str(s) should reject what cannot be converted to a
string_view");
+
+ static_assert(!std::is_convertible_v<string_view, stringstream>,
+ "stringstream(string_view, ios::openmode) is explicit");
+ static_assert(!std::is_convertible_v<const string_view, stringstream>,
+ "stringstream(string_view, ios::openmode) is explicit");
+ static_assert(!std::is_convertible_v<convertible_to_string_view,
stringstream>,
+ "stringstream(convertible_to_string_view, ios::openmode) is explicit");
+ static_assert(!std::is_convertible_v<const convertible_to_string_view,
stringstream>,
+ "stringstream(convertible_to_string_view, ios::openmode) is explicit");
+
+ {
+ stringstream strstr(cstr);
+ VERIFY( strstr.str() == cstr.s );
+ VERIFY( strstr.get() == cstr.s[0] );
+ }
+ {
+ stringstream strstr(ccstr);
+ VERIFY( strstr.str() == ccstr.s );
+ VERIFY( strstr.get() == ccstr.s[0] );
+ }
+ {
+ stringstream strstr(cstr, std::ios_base::in);
+ VERIFY( strstr.str() == cstr.s );
+ VERIFY( strstr.get() == cstr.s[0] );
+ VERIFY( strstr.put('X').rdstate() == strstr.badbit );
+ }
+ {
+ stringstream strstr(cstr, std::ios_base::out);
+ VERIFY( strstr.str() == cstr.s );
+ VERIFY( strstr.put('Y').good() );
+ VERIFY( strstr.get() == stringstream::traits_type::eof());
+ }
+}
+
+void
+test02()
+{
+ // Test C++26 various constructors taking string views
+
+ auto const mode = std::ios_base::in | std::ios_base::out;
+
+ {
+ // template <typename T>
+ // basic_stringstream(const T&, ios_base::openmode, const allocator_type&)
+
+ stringstream::allocator_type a;
+ {
+ stringstream strstr(cstr, mode, a); // ={} checks for non-explicit ctor
+ VERIFY( strstr.str() == cstr.s );
+ }
+ {
+ stringstream strstr(cstr, std::ios::in, a);
+ VERIFY( strstr.str() == cstr.s );
+ VERIFY( strstr.get() == cstr.s[0] );
+ VERIFY( strstr.put('X').rdstate() == strstr.badbit );
+ }
+ {
+ stringstream strstr(cstr, std::ios::out, a);
+ VERIFY( strstr.str() == cstr.s );
+ VERIFY( strstr.put('X').good() );
+ VERIFY( strstr.get() == stringstream::traits_type::eof());
+ }
+ }
+
+ {
+ // template <typename T>
+ // basic_stringstream(const T&, ios_base::openmode)
+
+ {
+ stringstream strstr(cstr, mode);
+ VERIFY( strstr.str() == cstr.s );
+ VERIFY( strstr.get() == cstr.s[0] );
+ VERIFY( strstr.put('X').good() );
+ }
+ {
+ stringstream strstr(cstr, std::ios::in);
+ VERIFY( strstr.str() == cstr.s );
+ VERIFY( strstr.get() == cstr.s[0] );
+ VERIFY( strstr.put('X').rdstate() == strstr.badbit );
+ }
+ {
+ stringstream strstr(cstr, std::ios::out);
+ VERIFY( strstr.str() == cstr.s );
+ VERIFY( strstr.put('X').good() );
+ VERIFY( strstr.get() == stringstream::traits_type::eof());
+ }
+ }
+
+ {
+ // template <typename T>
+ // explicit
+ // basic_stringstream(const T&, ios_base::openmode =
ios_base::in|ios_base::out)
+
+ stringstream strstr(cstr);
+ VERIFY( strstr.str() == cstr.s );
+ VERIFY( strstr.get() == cstr.s[0] );
+ VERIFY( strstr.put('X').good() );
+ }
+}
+
+// A minimal allocator with no default constructor
+template<typename T>
+ struct NoDefaultCons : __gnu_test::SimpleAllocator<T>
+ {
+ using __gnu_test::SimpleAllocator<T>::SimpleAllocator;
+ NoDefaultCons() = delete;
+ NoDefaultCons(int) { }
+ };
+
+using alloc_type = __gnu_test::uneq_allocator<C>;
+
+template<typename Alloc, typename CC = typename Alloc::value_type>
+ using stringstream_with_alloc
+ = std::basic_stringstream<CC, std::char_traits<CC>, Alloc>;
+
+void test03()
+{
+ alloc_type a{1};
+ {
+ stringstream_with_alloc<alloc_type> strstr(cstr, a);
+ VERIFY( strstr.rdbuf()->get_allocator() == a );
+ VERIFY( string_view{strstr.str()} == cstr );
+ VERIFY( strstr.get() == cstr.s[0] );
+ }
+ {
+ stringstream_with_alloc<alloc_type> strstr(cstr, std::ios::in, a);
+ VERIFY( strstr.rdbuf()->get_allocator() == a );
+ VERIFY( string_view{strstr.str()} == cstr );
+ VERIFY( strstr.get() == cstr.s[0] );
+ VERIFY( strstr.put('X').rdstate() == strstr.badbit );
+ }
+ {
+ stringstream_with_alloc<alloc_type> strstr(cstr, std::ios::out, a);
+ VERIFY( strstr.rdbuf()->get_allocator() == a );
+ VERIFY( string_view{strstr.str()} == cstr );
+ VERIFY( strstr.put('X').good() );
+ VERIFY( strstr.get() == stringstream::traits_type::eof());
+ }
+}
+
+void test04()
+{
+ {
+ stringstream strstr;
+ strstr.str( cstr );
+ VERIFY( strstr.str() == cstr.s );
+ }
+ {
+ stringstream strstr;
+ strstr.str( ccstr );
+ VERIFY( strstr.str() == ccstr.s );
+ }
+}
+
+int
+main()
+{
+ test01();
+ test02();
+ test03();
+ test04();
+}
diff --git
a/libstdc++-v3/testsuite/27_io/basic_stringstream/cons/wchar_t/string_view.cc
b/libstdc++-v3/testsuite/27_io/basic_stringstream/cons/wchar_t/string_view.cc
new file mode 100644
index 00000000000..cfb73c4c510
--- /dev/null
+++
b/libstdc++-v3/testsuite/27_io/basic_stringstream/cons/wchar_t/string_view.cc
@@ -0,0 +1,3 @@
+#define C wchar_t
+#define L(a) L##a
+#include "../char/string_view.cc"
--
2.49.0
