On Thu, 14 May 2020 at 03:50, Ray Lischner <r...@klipp-lischner.net> wrote:
> On 5/13/20 10:09 PM, Richard Smith wrote: > > On Wed, 6 May 2020 at 09:24, Ray Lischner via cfe-users > > <cfe-users@lists.llvm.org <mailto:cfe-users@lists.llvm.org>> wrote: > > > > I am using clang++ 10 with GCC libstdc++ 10 prerelease. I tried > > compiling the example from section 24.6.4.1 > > [range.istream.overview]. It > > works with g++ 10 but with clang++ 10 -std=c++20, I get > > constraint-failure errors. > > > > program: > > #include <algorithm> > > #include <iostream> > > #include <iterator> > > #include <ranges> > > #include <sstream> > > > > int main() > > { > > using namespace std; > > using namespace ranges; > > auto ints = istringstream{"0 1 2 3 4"}; > > ranges::copy(istream_view<int>(ints), > > ostream_iterator<int>{cout, "-"}); > > // prints0-1-2-3-4- > > } > > > > $ clang++ -std=c++20 -o range_istream_overview \ > > range_istream_overview.cpp > > > > Gist of the errors is that the istream_view fails the constraints > for a > > range because ranges::begin() fails its constraint for the > > basic_istream_view::begin() member function: > > > > { __detail::__decay_copy(__t.begin()) } -> input_or_output_iterator; > > > > Any ideas what's wrong or how to proceed? > > > > > > Please could you provide the complete set of diagnostics from the > > compilation? > > In file included from range_istream_overview.cpp:1: > In file included from > > /usr/bin/../lib64/gcc/x86_64-suse-linux/10/../../../../include/c++/10/algorithm:61: > In file included from > > /usr/bin/../lib64/gcc/x86_64-suse-linux/10/../../../../include/c++/10/bits/stl_algobase.h:65: > In file included from > > /usr/bin/../lib64/gcc/x86_64-suse-linux/10/../../../../include/c++/10/bits/stl_iterator_base_types.h:71: > /usr/bin/../lib64/gcc/x86_64-suse-linux/10/../../../../include/c++/10/bits/iterator_concepts.h:884:13: > > error: no matching function for call to '__ranges_begin' > = decltype(__detail::__ranges_begin(std::declval<_Tp&>())); > ^~~~~~~~~~~~~~~~~~~~~~~~ > /usr/bin/../lib64/gcc/x86_64-suse-linux/10/../../../../include/c++/10/bits/range_access.h:874:5: > > note: in instantiation of template type alias '__range_iter_t' requested > here > using iterator_t = std::__detail::__range_iter_t<_Tp>; > ^ > /usr/bin/../lib64/gcc/x86_64-suse-linux/10/../../../../include/c++/10/ranges:134:43: > > note: in instantiation of template type alias 'iterator_t' requested here > data() requires contiguous_iterator<iterator_t<_Derived>> > ^ > /usr/bin/../lib64/gcc/x86_64-suse-linux/10/../../../../include/c++/10/ranges:956:14: > > note: in instantiation of template class > 'std::ranges::view_interface<std::ranges::basic_istream_view<int, char, > std::char_traits<char> > >' requested here > : public view_interface<basic_istream_view<_Val, _CharT, _Traits>> > ^ > range_istream_overview.cpp:12:16: note: in instantiation of template > class 'std::ranges::basic_istream_view<int, char, std::char_traits<char> > >' requested here > ranges::copy(istream_view<int>(ints), ostream_iterator<int>{cout, "-"}); > ^ > OK, so the relevant part is this: > /usr/bin/../lib64/gcc/x86_64-suse-linux/10/../../../../include/c++/10/bits/iterator_concepts.h:867:7: > > note: candidate template ignored: constraints not satisfied [with _Tp = > std::ranges::basic_istream_view<int, char, std::char_traits<char> >] > __ranges_begin(_Tp& __t) > ^ > /usr/bin/../lib64/gcc/x86_64-suse-linux/10/../../../../include/c++/10/bits/iterator_concepts.h:865:16: > > note: because 'is_array_v<std::ranges::basic_istream_view<int, char, > std::char_traits<char> > >' evaluated to false > requires is_array_v<_Tp> || __member_begin<_Tp&> || > __adl_begin<_Tp&> > ^ > /usr/bin/../lib64/gcc/x86_64-suse-linux/10/../../../../include/c++/10/bits/iterator_concepts.h:865:35: > > note: and 'std::ranges::basic_istream_view<int, char, > std::char_traits<char> > &' does not satisfy '__member_begin' > requires is_array_v<_Tp> || __member_begin<_Tp&> || > __adl_begin<_Tp&> > ^ > /usr/bin/../lib64/gcc/x86_64-suse-linux/10/../../../../include/c++/10/bits/iterator_concepts.h:849:33: > > note: because '__detail::__decay_copy(__t.begin())' would be invalid: no > member named 'begin' in 'std::ranges::basic_istream_view<int, char, > std::char_traits<char> >' > { __detail::__decay_copy(__t.begin()) } -> > input_or_output_iterator; > ^ > /usr/bin/../lib64/gcc/x86_64-suse-linux/10/../../../../include/c++/10/bits/iterator_concepts.h:865:59: > > note: and 'std::ranges::basic_istream_view<int, char, > std::char_traits<char> > &' does not satisfy '__adl_begin' > requires is_array_v<_Tp> || __member_begin<_Tp&> || > __adl_begin<_Tp&> > ^ > /usr/bin/../lib64/gcc/x86_64-suse-linux/10/../../../../include/c++/10/bits/iterator_concepts.h:859:29: > > note: because '__detail::__decay_copy(begin(__t))' would be invalid: > call to deleted function 'begin' > { __detail::__decay_copy(begin(__t)) } -> > input_or_output_iterator; > ^ > Just as you said, it looks like the problem is that __member_begin<istream_view<int>&> is evaluating to 'false', whereas it presumably should evaluate to 'true'. Can you try calling begin() on an istream_view<int>& directly, and see if you get the same error? A heavily-reduced testcase doesn't demonstrate the problem -- https://godbolt.org/z/Np4EMg -- so I imagine there's something else required to trigger this behavior. A more-reduced testcase should make the problem easier to understand. > /usr/bin/../lib64/gcc/x86_64-suse-linux/10/../../../../include/c++/10/bits/iterator_concepts.h:884:13: > > error: no matching function for call to '__ranges_begin' > = decltype(__detail::__ranges_begin(std::declval<_Tp&>())); > ^~~~~~~~~~~~~~~~~~~~~~~~ > /usr/bin/../lib64/gcc/x86_64-suse-linux/10/../../../../include/c++/10/bits/range_access.h:874:5: > > note: in instantiation of template type alias '__range_iter_t' requested > here > using iterator_t = std::__detail::__range_iter_t<_Tp>; > ^ > /usr/bin/../lib64/gcc/x86_64-suse-linux/10/../../../../include/c++/10/ranges:140:25: > > note: in instantiation of template type alias 'iterator_t' requested here > && contiguous_iterator<iterator_t<const _Derived>> > ^ > /usr/bin/../lib64/gcc/x86_64-suse-linux/10/../../../../include/c++/10/ranges:956:14: > > note: in instantiation of template class > 'std::ranges::view_interface<std::ranges::basic_istream_view<int, char, > std::char_traits<char> > >' requested here > : public view_interface<basic_istream_view<_Val, _CharT, _Traits>> > ^ > range_istream_overview.cpp:12:16: note: in instantiation of template > class 'std::ranges::basic_istream_view<int, char, std::char_traits<char> > >' requested here > ranges::copy(istream_view<int>(ints), ostream_iterator<int>{cout, "-"}); > ^ > /usr/bin/../lib64/gcc/x86_64-suse-linux/10/../../../../include/c++/10/bits/iterator_concepts.h:867:7: > > note: candidate template ignored: constraints not satisfied [with _Tp = > const std::ranges::basic_istream_view<int, char, std::char_traits<char> >] > __ranges_begin(_Tp& __t) > ^ > /usr/bin/../lib64/gcc/x86_64-suse-linux/10/../../../../include/c++/10/bits/iterator_concepts.h:865:16: > > note: because 'is_array_v<const std::ranges::basic_istream_view<int, > char, std::char_traits<char> > >' evaluated to false > requires is_array_v<_Tp> || __member_begin<_Tp&> || > __adl_begin<_Tp&> > ^ > /usr/bin/../lib64/gcc/x86_64-suse-linux/10/../../../../include/c++/10/bits/iterator_concepts.h:865:35: > > note: and 'const std::ranges::basic_istream_view<int, char, > std::char_traits<char> > &' does not satisfy '__member_begin' > requires is_array_v<_Tp> || __member_begin<_Tp&> || > __adl_begin<_Tp&> > ^ > /usr/bin/../lib64/gcc/x86_64-suse-linux/10/../../../../include/c++/10/bits/iterator_concepts.h:849:33: > > note: because '__detail::__decay_copy(__t.begin())' would be invalid: no > member named 'begin' in 'std::ranges::basic_istream_view<int, char, > std::char_traits<char> >' > { __detail::__decay_copy(__t.begin()) } -> > input_or_output_iterator; > ^ > /usr/bin/../lib64/gcc/x86_64-suse-linux/10/../../../../include/c++/10/bits/iterator_concepts.h:865:59: > > note: and 'const std::ranges::basic_istream_view<int, char, > std::char_traits<char> > &' does not satisfy '__adl_begin' > requires is_array_v<_Tp> || __member_begin<_Tp&> || > __adl_begin<_Tp&> > ^ > /usr/bin/../lib64/gcc/x86_64-suse-linux/10/../../../../include/c++/10/bits/iterator_concepts.h:859:29: > > note: because '__detail::__decay_copy(begin(__t))' would be invalid: > call to deleted function 'begin' > { __detail::__decay_copy(begin(__t)) } -> > input_or_output_iterator; > ^ > In file included from range_istream_overview.cpp:1: > In file included from > > /usr/bin/../lib64/gcc/x86_64-suse-linux/10/../../../../include/c++/10/algorithm:64: > In file included from > > /usr/bin/../lib64/gcc/x86_64-suse-linux/10/../../../../include/c++/10/bits/ranges_algo.h:35: > In file included from > > /usr/bin/../lib64/gcc/x86_64-suse-linux/10/../../../../include/c++/10/bits/ranges_algobase.h:38: > /usr/bin/../lib64/gcc/x86_64-suse-linux/10/../../../../include/c++/10/ranges:146:24: > > error: constraints not satisfied for alias template 'sentinel_t' [with > _Range = std::ranges::basic_istream_view<int, char, > std::char_traits<char> >] > && sized_sentinel_for<sentinel_t<_Derived>, iterator_t<_Derived>> > ^~~~~~~~~~~~~~~~~~~~ > /usr/bin/../lib64/gcc/x86_64-suse-linux/10/../../../../include/c++/10/ranges:956:14: > > note: in instantiation of template class > 'std::ranges::view_interface<std::ranges::basic_istream_view<int, char, > std::char_traits<char> > >' requested here > : public view_interface<basic_istream_view<_Val, _CharT, _Traits>> > ^ > range_istream_overview.cpp:12:16: note: in instantiation of template > class 'std::ranges::basic_istream_view<int, char, std::char_traits<char> > >' requested here > ranges::copy(istream_view<int>(ints), ostream_iterator<int>{cout, "-"}); > ^ > /usr/bin/../lib64/gcc/x86_64-suse-linux/10/../../../../include/c++/10/bits/range_access.h:876:12: > > note: because 'std::ranges::basic_istream_view<int, char, > std::char_traits<char> >' does not satisfy 'range' > template<range _Range> > ^ > /usr/bin/../lib64/gcc/x86_64-suse-linux/10/../../../../include/c++/10/bits/range_access.h:864:2: > > note: because 'ranges::begin(__t)' would be invalid: no matching > function for call to object of type 'const __cust_access::_Begin' > ranges::begin(__t); > ^ > In file included from range_istream_overview.cpp:1: > In file included from > > /usr/bin/../lib64/gcc/x86_64-suse-linux/10/../../../../include/c++/10/algorithm:64: > In file included from > > /usr/bin/../lib64/gcc/x86_64-suse-linux/10/../../../../include/c++/10/bits/ranges_algo.h:35: > In file included from > > /usr/bin/../lib64/gcc/x86_64-suse-linux/10/../../../../include/c++/10/bits/ranges_algobase.h:38: > /usr/bin/../lib64/gcc/x86_64-suse-linux/10/../../../../include/c++/10/ranges:152:24: > > error: constraints not satisfied for alias template 'sentinel_t' [with > _Range = const std::ranges::basic_istream_view<int, char, > std::char_traits<char> >] > && sized_sentinel_for<sentinel_t<const _Derived>, > ^~~~~~~~~~~~~~~~~~~~~~~~~~ > /usr/bin/../lib64/gcc/x86_64-suse-linux/10/../../../../include/c++/10/bits/range_access.h:876:12: > > note: because 'const std::ranges::basic_istream_view<int, char, > std::char_traits<char> >' does not satisfy 'range' > template<range _Range> > ^ > /usr/bin/../lib64/gcc/x86_64-suse-linux/10/../../../../include/c++/10/bits/range_access.h:864:2: > > note: because 'ranges::begin(__t)' would be invalid: no matching > function for call to object of type 'const __cust_access::_Begin' > ranges::begin(__t); > ^ > range_istream_overview.cpp:12:3: error: no matching function for call to > object of type 'const std::ranges::__copy_fn' > ranges::copy(istream_view<int>(ints), ostream_iterator<int>{cout, "-"}); > ^~~~~~~~~~~~ > /usr/bin/../lib64/gcc/x86_64-suse-linux/10/../../../../include/c++/10/bits/ranges_algobase.h:309:7: > > note: candidate template ignored: substitution failure [with _Range = > std::ranges::basic_istream_view<int, char, std::char_traits<char> >, > _Out = std::ostream_iterator<int, char, std::char_traits<char> >]: > constraints not satisfied for alias template 'borrowed_iterator_t' [with > _Range = std::ranges::basic_istream_view<int, char, > std::char_traits<char> >] > operator()(_Range&& __r, _Out __result) const > ^ > /usr/bin/../lib64/gcc/x86_64-suse-linux/10/../../../../include/c++/10/bits/ranges_algobase.h:299:7: > > note: candidate function template not viable: requires 3 arguments, but > 2 were provided > operator()(_Iter __first, _Sent __last, _Out __result) const > ^ > 5 errors generated. > > -- > Ray Lischner >
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