[libcxx][test] ostream{,buf}_iterator::difference_type changes in C++20

[ldionne]

Summary

Although libc++ doesn't yet implement this change, these tests should expect the difference type of std::ostream_iterator and std::ostreambuf_iterator specializations to be std::ptrdiff_t instead of void when testing C++ versions greater than 17 if the library under test is not libc++.

[ldionne]

What paper is this? I searched but failed to find a paper this falls off from.

[CaseyCarter]

In D87459#2265864, @ldionne wrote:

What paper is this? I searched but failed to find a paper this falls off from.

P0896R4 "The One Ranges Proposal" - Ranges demands that all iterators have useful difference types.

[ldionne]

In D87459#2265871, @CaseyCarter wrote:

In D87459#2265864, @ldionne wrote:

What paper is this? I searched but failed to find a paper this falls off from.

P0896R4 "The One Ranges Proposal" - Ranges demands that all iterators have useful difference types.

Ah, I see it. I'll add that bit to libc++ so we don't need special casing in the tests.

[CaseyCarter]

Ah, I see it. I'll add that bit to libc++ so we don't need special casing in the tests.

Feel free to steal this for your test changes. Shall I close this differential then?

[ldionne]

In D87459#2265875, @CaseyCarter wrote:

Ah, I see it. I'll add that bit to libc++ so we don't need special casing in the tests.

Feel free to steal this for your test changes. Shall I close this differential then?

No need, I'll steal it by commandeering.

[ldionne]

Implement the changes for libc++.

[CaseyCarter]

LGTM! (You should say "Partially implements P0896R4" in the commit log =))

libcxx/include/iterator

1052

std::iterator has been deprecated since C++17. Should this inheritance be dependent on _LIBCPP_STD_VER < 17? It's unnecessary now that the member types are defined directly. (Also on line 1161.)

libcxx/include/iterator

 operator!=(const istream_iterator<_Tp, _CharT, _Traits, _Distance>& __x,
            const istream_iterator<_Tp, _CharT, _Traits, _Distance>& __y)
 {
     return !(__x == __y);
 }
 
 template <class _Tp, class _CharT = char, class _Traits = char_traits<_CharT> >
 class _LIBCPP_TEMPLATE_VIS ostream_iterator
     : public iterator<output_iterator_tag, void, void, void, void>
 {
 public:
-    typedef _CharT char_type;
-    typedef _Traits traits_type;
-    typedef basic_ostream<_CharT,_Traits> ostream_type;
+    typedef output_iterator_tag             iterator_category;
+    typedef void                            value_type;
+#if _LIBCPP_STD_VER > 17
+    typedef std::ptrdiff_t                  difference_type;
+#else
+    typedef void                            difference_type;
+#endif
+    typedef void                            pointer;
+    typedef void                            reference;
+    typedef _CharT                          char_type;
+    typedef _Traits                         traits_type;
+    typedef basic_ostream<_CharT, _Traits>  ostream_type;
+
 private:
     ostream_type* __out_stream_;
     const char_type* __delim_;
 public:
     _LIBCPP_INLINE_VISIBILITY ostream_iterator(ostream_type& __s) _NOEXCEPT
         : __out_stream_(_VSTD::addressof(__s)), __delim_(0) {}
     _LIBCPP_INLINE_VISIBILITY ostream_iterator(ostream_type& __s, const _CharT* __delimiter) _NOEXCEPT
         : __out_stream_(_VSTD::addressof(__s)), __delim_(__delimiter) {}
bool operator!=(const istreambuf_iterator<_CharT,_Traits>& __a,
                 const istreambuf_iterator<_CharT,_Traits>& __b)
                 {return !__a.equal(__b);}
 
 template <class _CharT, class _Traits>
 class _LIBCPP_TEMPLATE_VIS ostreambuf_iterator
     : public iterator<output_iterator_tag, void, void, void, void>
 {
 public:
-    typedef _CharT                          char_type;
-    typedef _Traits                         traits_type;
-    typedef basic_streambuf<_CharT,_Traits> streambuf_type;
-    typedef basic_ostream<_CharT,_Traits>   ostream_type;
+    typedef output_iterator_tag                 iterator_category;
+    typedef void                                value_type;
+#if _LIBCPP_STD_VER > 17
+    typedef std::ptrdiff_t                      difference_type;
+#else
+    typedef void                                difference_type;
+#endif
+    typedef void                                pointer;
+    typedef void                                reference;
+    typedef _CharT                              char_type;
+    typedef _Traits                             traits_type;
+    typedef basic_streambuf<_CharT, _Traits>    streambuf_type;
+    typedef basic_ostream<_CharT, _Traits>      ostream_type;
+
 private:
     streambuf_type* __sbuf_;
 public:
     _LIBCPP_INLINE_VISIBILITY ostreambuf_iterator(ostream_type& __s) _NOEXCEPT
         : __sbuf_(__s.rdbuf()) {}
     _LIBCPP_INLINE_VISIBILITY ostreambuf_iterator(streambuf_type* __s) _NOEXCEPT
         : __sbuf_(__s) {}
     _LIBCPP_INLINE_VISIBILITY ostreambuf_iterator& operator=(_CharT __c)

libcxx/test/std/iterators/stream.iterators/ostream.iterator/types.pass.cpp

 //     : public iterator<output_iterator_tag, void, void, void, void>
 // {
 // public:
 //     typedef charT char_type;
 //     typedef traits traits_type;
 //     typedef basic_istream<charT,traits> istream_type;
 //     ...
 
+#include <cstddef>
 #include <iterator>
 #include <type_traits>
 
 #include "test_macros.h"
 
 int main(int, char**)
 {
     typedef std::ostream_iterator<double> I1;
 #if TEST_STD_VER <= 14
     static_assert((std::is_convertible<I1,
         std::iterator<std::output_iterator_tag, void, void, void, void> >::value), "");
 #else
     static_assert((std::is_same<I1::iterator_category, std::output_iterator_tag>::value), "");
     static_assert((std::is_same<I1::value_type, void>::value), "");
+#if TEST_STD_VER <= 17
     static_assert((std::is_same<I1::difference_type, void>::value), "");
+#else
+    static_assert((std::is_same<I1::difference_type, std::ptrdiff_t>::value), "");
+#endif
     static_assert((std::is_same<I1::pointer, void>::value), "");
     static_assert((std::is_same<I1::reference, void>::value), "");
 #endif
     static_assert((std::is_same<I1::char_type, char>::value), "");
     static_assert((std::is_same<I1::traits_type, std::char_traits<char> >::value), "");
     static_assert((std::is_same<I1::ostream_type, std::ostream>::value), "");
     typedef std::ostream_iterator<unsigned, wchar_t> I2;
 #if TEST_STD_VER <= 14
     static_assert((std::is_convertible<I2,
         std::iterator<std::output_iterator_tag, void, void, void, void> >::value), "");
 #else
     static_assert((std::is_same<I2::iterator_category, std::output_iterator_tag>::value), "");
     static_assert((std::is_same<I2::value_type, void>::value), "");
+#if TEST_STD_VER <= 17
     static_assert((std::is_same<I2::difference_type, void>::value), "");
+#else
+    static_assert((std::is_same<I2::difference_type, std::ptrdiff_t>::value), "");
+#endif
     static_assert((std::is_same<I2::pointer, void>::value), "");
     static_assert((std::is_same<I2::reference, void>::value), "");
 #endif
     static_assert((std::is_same<I2::char_type, wchar_t>::value), "");
     static_assert((std::is_same<I2::traits_type, std::char_traits<wchar_t> >::value), "");
     static_assert((std::is_same<I2::ostream_type, std::wostream>::value), "");
 
   return 0;
 }

libcxx/test/std/iterators/stream.iterators/ostreambuf.iterator/types.pass.cpp

 // {
 // public:
 //   typedef charT                          char_type;
 //   typedef traits                         traits_type;
 //   typedef basic_streambuf<charT, traits> streambuf_type;
 //   typedef basic_ostream<charT, traits>   ostream_type;
 //   ...
 
+#include <cstddef>
 #include <iterator>
 #include <string>
 #include <type_traits>
 
 #include "test_macros.h"
 
 int main(int, char**)
 {
     typedef std::ostreambuf_iterator<char> I1;
 #if TEST_STD_VER <= 14
     static_assert((std::is_convertible<I1,
         std::iterator<std::output_iterator_tag, void, void, void, void> >::value), "");
 #else
     static_assert((std::is_same<I1::iterator_category, std::output_iterator_tag>::value), "");
     static_assert((std::is_same<I1::value_type, void>::value), "");
+#if TEST_STD_VER <= 17
     static_assert((std::is_same<I1::difference_type, void>::value), "");
+#else
+    static_assert((std::is_same<I1::difference_type, std::ptrdiff_t>::value), "");
+#endif
     static_assert((std::is_same<I1::pointer, void>::value), "");
     static_assert((std::is_same<I1::reference, void>::value), "");
 #endif
     static_assert((std::is_same<I1::char_type, char>::value), "");
     static_assert((std::is_same<I1::traits_type, std::char_traits<char> >::value), "");
     static_assert((std::is_same<I1::streambuf_type, std::streambuf>::value), "");
     static_assert((std::is_same<I1::ostream_type, std::ostream>::value), "");
 
     typedef std::ostreambuf_iterator<wchar_t> I2;
 #if TEST_STD_VER <= 14
     static_assert((std::is_convertible<I2,
         std::iterator<std::output_iterator_tag, void, void, void, void> >::value), "");
 #else
     static_assert((std::is_same<I2::iterator_category, std::output_iterator_tag>::value), "");
     static_assert((std::is_same<I2::value_type, void>::value), "");
+#if TEST_STD_VER <= 17
     static_assert((std::is_same<I2::difference_type, void>::value), "");
+#else
+    static_assert((std::is_same<I2::difference_type, std::ptrdiff_t>::value), "");
+#endif
     static_assert((std::is_same<I2::pointer, void>::value), "");
     static_assert((std::is_same<I2::reference, void>::value), "");
 #endif
     static_assert((std::is_same<I2::char_type, wchar_t>::value), "");
     static_assert((std::is_same<I2::traits_type, std::char_traits<wchar_t> >::value), "");
     static_assert((std::is_same<I2::streambuf_type, std::wstreambuf>::value), "");
     static_assert((std::is_same<I2::ostream_type, std::wostream>::value), "");
 
   return 0;
 }