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, "-"});
^
/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;
^
/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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