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* [gcc r12-1228] libstdc++: Implement LWG 3403 for std::ranges::ssize
@ 2021-06-04 20:43 Jonathan Wakely
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From: Jonathan Wakely @ 2021-06-04 20:43 UTC (permalink / raw)
To: gcc-cvs, libstdc++-cvs
https://gcc.gnu.org/g:621ea10ca060ba19ec693aa73b5e29d553cca849
commit r12-1228-g621ea10ca060ba19ec693aa73b5e29d553cca849
Author: Jonathan Wakely <jwakely@redhat.com>
Date: Fri Jun 4 20:28:04 2021 +0100
libstdc++: Implement LWG 3403 for std::ranges::ssize
I already changed the constraints for ranges::ssize to use ranges::size,
this implements the rest of LWG 3403, so that the returned type is the
signed type corresponding to the result of ranges::size.
Signed-off-by: Jonathan Wakely <jwakely@redhat.com>
libstdc++-v3/ChangeLog:
* include/bits/ranges_base.h (_SSize): Return the result of
ranges::size converted to the wider of make-signed-like-t<S> and
ptrdiff_t, rather than the ranges different type.
* testsuite/std/ranges/access/ssize.cc: Adjust expected result
for an iota_view that uses an integer class type for its
difference_type.
Diff:
---
libstdc++-v3/include/bits/ranges_base.h | 22 ++++++++++++++++------
libstdc++-v3/testsuite/std/ranges/access/ssize.cc | 9 ++++++---
2 files changed, 22 insertions(+), 9 deletions(-)
diff --git a/libstdc++-v3/include/bits/ranges_base.h b/libstdc++-v3/include/bits/ranges_base.h
index 61d91eb8389..e3c3962bcd9 100644
--- a/libstdc++-v3/include/bits/ranges_base.h
+++ b/libstdc++-v3/include/bits/ranges_base.h
@@ -425,22 +425,32 @@ namespace ranges
struct _SSize
{
+ // _GLIBCXX_RESOLVE_LIB_DEFECTS
+ // 3403. Domain of ranges::ssize(E) doesn't match ranges::size(E)
template<typename _Tp>
requires requires (_Tp& __t) { _Size{}(__t); }
constexpr auto
operator()(_Tp&& __t) const noexcept(noexcept(_Size{}(__t)))
{
- using __iter_type = decltype(_Begin{}(__t));
- using __diff_type = iter_difference_t<__iter_type>;
- using __gnu_cxx::__int_traits;
auto __size = _Size{}(__t);
- if constexpr (integral<__diff_type>)
+ using __size_type = decltype(__size);
+ // Return the wider of ptrdiff_t and make-signed-like-t<__size_type>.
+ if constexpr (integral<__size_type>)
{
- if constexpr (__int_traits<__diff_type>::__digits
+ using __gnu_cxx::__int_traits;
+ if constexpr (__int_traits<__size_type>::__digits
< __int_traits<ptrdiff_t>::__digits)
return static_cast<ptrdiff_t>(__size);
+ else
+ return static_cast<make_signed_t<__size_type>>(__size);
}
- return static_cast<__diff_type>(__size);
+#if defined __STRICT_ANSI__ && defined __SIZEOF_INT128__
+ // For strict-ansi modes integral<__int128> is false
+ else if constexpr (__detail::__is_int128<__size_type>)
+ return static_cast<unsigned __int128>(__size);
+#endif
+ else // Must be one of __max_diff_type or __max_size_type.
+ return __detail::__max_diff_type(__size);
}
};
diff --git a/libstdc++-v3/testsuite/std/ranges/access/ssize.cc b/libstdc++-v3/testsuite/std/ranges/access/ssize.cc
index b00ec5db1f8..f53f462580c 100644
--- a/libstdc++-v3/testsuite/std/ranges/access/ssize.cc
+++ b/libstdc++-v3/testsuite/std/ranges/access/ssize.cc
@@ -76,9 +76,12 @@ void
test06()
{
auto i = std::views::iota(1ull, 5u);
- auto s = std::ranges::ssize(i);
- using R = std::ranges::range_difference_t<decltype(i)>;
- static_assert( std::same_as<decltype(s), R> );
+ auto s = std::ranges::size(i);
+ auto ss = std::ranges::ssize(i);
+ // std::ranges::range_difference_t<decltype(i)> is larger than long long,
+ // but LWG 3403 says ranges::ssize(i) returns the signed version of the
+ // type that ranges::size(i) returns, not the range's difference_type.
+ static_assert( std::same_as<decltype(ss), std::make_signed_t<decltype(s)>> );
VERIFY( s == 4 );
}
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