On 04/06/21 21:44 +0100, Jonathan Wakely wrote:
On 04/06/21 18:03 +0100, Jonathan Wakely wrote:
The implementation of P2091R0 was incomplete, so that some range access
CPOs used perfect forwarding where they should not. This fixes it by
consistently operating on lvalues.
Some additional changes that are not necessary to fix the bug:
Modify the __as_const helper to simplify its usage. Instead of deducing
the value category from its argument, and requiring callers to forward
the argument as the correct category, add a non-deduced template
parameter which is used for the value category and accept the argument
as an lvalue. This means callers say __as_const<T>(t) instead of
__as_const(std::forward<T>(t)).
Always use an lvalue reference type as the template argument for the
_S_noexcept helpers, so that we only instantiate one specialization for
lvalues and rvalues of the same type.
Move some helper concepts and functions from namespace std::__detail
to ranges::__cust_access, to be consistent with the ranges::begin CPO.
This ensures that the __adl_begin concept and the _Begin::operator()
function are in the same namespace, so unqualified lookup is consistent
and the poison pills for begin are visible to both.
Simplified static assertions for arrays, because the expression a+0 is
already ill-formed for an array of incomplete type.
Signed-off-by: Jonathan Wakely <jwak...@redhat.com>
libstdc++-v3/ChangeLog:
PR libstdc++/100824
* include/bits/iterator_concepts.h (__detail::__decay_copy)
(__detail::__member_begin, __detail::__adl_begin): Move to
namespace ranges::__cust_access.
(__detail::__ranges_begin): Likewise, and rename to __begin.
Remove redundant static assertion.
* include/bits/ranges_base.h (_Begin, _End, _RBegin, _REnd):
Use lvalue in noexcept specifier.
(__as_const): Add non-deduced parameter for value category.
(_CBegin, _CEnd, _CRBegin, _CREnd, _CData): Adjust uses of
__as_const.
(__member_size, __adl_size, __member_empty, __size0_empty):
(__eq_iter_empty, __adl_data): Use lvalue objects in
requirements.
(__sentinel_size): Likewise. Add check for conversion to
unsigned-like.
(__member_data): Allow non-lvalue types to satisfy the concept,
but use lvalue object in requirements.
(_Size, _SSize): Remove forwarding to always use an lvalue.
(_Data): Likewise. Add static assertion for arrays.
* testsuite/std/ranges/access/cdata.cc: Adjust expected
behaviour for rvalues. Add negative tests for ill-formed
expressions.
* testsuite/std/ranges/access/data.cc: Likewise.
* testsuite/std/ranges/access/empty.cc: Adjust expected
behaviour for rvalues.
* testsuite/std/ranges/access/size.cc: Likewise.
An additional problem with ranges::data was pointed out in the PR,
fixed with this patch.
And this implements the rest of LWG 3403. The change to the
ranges::ssize constraints was already done by the first patch in this
thread, this fixes the return type.
Tested powerpc64le-linux. Committed to trunk.
This should also be backported to gcc-11 and gcc-10.
commit 621ea10ca060ba19ec693aa73b5e29d553cca849
Author: Jonathan Wakely <jwak...@redhat.com>
Date: Fri Jun 4 20:28:04 2021
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 <jwak...@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 --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 );
}
