https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94562
Bug ID: 94562 Summary: C++20: std::shared_ptr<int>{} <=> nullptr ill-formed Product: gcc Version: unknown Status: UNCONFIRMED Severity: normal Priority: P3 Component: libstdc++ Assignee: unassigned at gcc dot gnu.org Reporter: daniel.kruegler at googlemail dot com Target Milestone: --- The following program (using -Wall -Wextra -std=c++2a -pedantic) is rejected: #include <memory> bool ok = std::shared_ptr<int>{} <=> nullptr; int main() { } with the following diagnostics: >>>>>>>>>>>>>>>>>>>>>> prog.cc:3:34: error: no match for 'operator<=>' (operand types are 'std::shared_ptr<int>' and 'std::nullptr_t') 3 | bool ok = std::shared_ptr<int>{} <=> nullptr; | ~~~~~~~~~~~~~~~~~~^~~~~~~~~~~ In file included from /opt/wandbox/gcc-head/include/c++/10.0.1/bits/stl_algobase.h:67, from /opt/wandbox/gcc-head/include/c++/10.0.1/memory:63, from prog.cc:1: /opt/wandbox/gcc-head/include/c++/10.0.1/bits/stl_iterator.h:474:5: note: candidate: 'template<class _IteratorL, class _IteratorR> requires three_way_comparable_with<_IteratorR, _IteratorL, std::partial_ordering> constexpr std::compare_three_way_result_t<_IteratorL, _IteratorR> std::operator<=>(const std::reverse_iterator<_IteratorL>&, const std::reverse_iterator<_IteratorR>&)' (reversed) 474 | operator<=>(const reverse_iterator<_IteratorL>& __x, | ^~~~~~~~ /opt/wandbox/gcc-head/include/c++/10.0.1/bits/stl_iterator.h:474:5: note: template argument deduction/substitution failed: prog.cc:3:38: note: mismatched types 'const std::reverse_iterator<_IteratorL>' and 'std::nullptr_t' 3 | bool ok = std::shared_ptr<int>{} <=> nullptr; | ^~~~~~~ In file included from /opt/wandbox/gcc-head/include/c++/10.0.1/bits/stl_algobase.h:67, from /opt/wandbox/gcc-head/include/c++/10.0.1/memory:63, from prog.cc:1: /opt/wandbox/gcc-head/include/c++/10.0.1/bits/stl_iterator.h:1433:5: note: candidate: 'template<class _IteratorL, class _IteratorR> requires three_way_comparable_with<_IteratorR, _IteratorL, std::partial_ordering> constexpr std::compare_three_way_result_t<_IteratorL, _IteratorR> std::operator<=>(const std::move_iterator<_IteratorL>&, const std::move_iterator<_IteratorR>&)' (reversed) 1433 | operator<=>(const move_iterator<_IteratorL>& __x, | ^~~~~~~~ /opt/wandbox/gcc-head/include/c++/10.0.1/bits/stl_iterator.h:1433:5: note: template argument deduction/substitution failed: prog.cc:3:38: note: mismatched types 'const std::move_iterator<_IteratorL>' and 'std::nullptr_t' 3 | bool ok = std::shared_ptr<int>{} <=> nullptr; | ^~~~~~~ In file included from /opt/wandbox/gcc-head/include/c++/10.0.1/ranges:45, from /opt/wandbox/gcc-head/include/c++/10.0.1/bits/ranges_algobase.h:38, from /opt/wandbox/gcc-head/include/c++/10.0.1/bits/ranges_uninitialized.h:36, from /opt/wandbox/gcc-head/include/c++/10.0.1/memory:69, from prog.cc:1: /opt/wandbox/gcc-head/include/c++/10.0.1/optional:1036:5: note: candidate: 'template<class _Tp, class _Up> requires three_way_comparable_with<_Up, _Tp, std::partial_ordering> constexpr std::compare_three_way_result_t<_IteratorL, _IteratorR> std::operator<=>(const std::optional<_Tp>&, const std::optional<_Up>&)' (reversed) 1036 | operator<=>(const optional<_Tp>& __x, const optional<_Up>& __y) | ^~~~~~~~ /opt/wandbox/gcc-head/include/c++/10.0.1/optional:1036:5: note: template argument deduction/substitution failed: prog.cc:3:38: note: mismatched types 'const std::optional<_Tp>' and 'std::nullptr_t' 3 | bool ok = std::shared_ptr<int>{} <=> nullptr; | ^~~~~~~ In file included from /opt/wandbox/gcc-head/include/c++/10.0.1/ranges:45, from /opt/wandbox/gcc-head/include/c++/10.0.1/bits/ranges_algobase.h:38, from /opt/wandbox/gcc-head/include/c++/10.0.1/bits/ranges_uninitialized.h:36, from /opt/wandbox/gcc-head/include/c++/10.0.1/memory:69, from prog.cc:1: /opt/wandbox/gcc-head/include/c++/10.0.1/optional:1051:5: note: candidate: 'template<class _Tp> constexpr std::strong_ordering std::operator<=>(const std::optional<_Tp>&, std::nullopt_t)' (reversed) 1051 | operator<=>(const optional<_Tp>& __x, nullopt_t) noexcept | ^~~~~~~~ /opt/wandbox/gcc-head/include/c++/10.0.1/optional:1051:5: note: template argument deduction/substitution failed: prog.cc:3:38: note: mismatched types 'const std::optional<_Tp>' and 'std::nullptr_t' 3 | bool ok = std::shared_ptr<int>{} <=> nullptr; | ^~~~~~~ In file included from /opt/wandbox/gcc-head/include/c++/10.0.1/ranges:45, from /opt/wandbox/gcc-head/include/c++/10.0.1/bits/ranges_algobase.h:38, from /opt/wandbox/gcc-head/include/c++/10.0.1/bits/ranges_uninitialized.h:36, from /opt/wandbox/gcc-head/include/c++/10.0.1/memory:69, from prog.cc:1: /opt/wandbox/gcc-head/include/c++/10.0.1/optional:1186:5: note: candidate: 'template<class _Tp, class _Up> constexpr std::compare_three_way_result_t<_IteratorL, _IteratorR> std::operator<=>(const std::optional<_Tp>&, const _Up&)' (reversed) 1186 | operator<=>(const optional<_Tp>& __x, const _Up& __v) | ^~~~~~~~ /opt/wandbox/gcc-head/include/c++/10.0.1/optional:1186:5: note: template argument deduction/substitution failed: prog.cc:3:38: note: mismatched types 'const std::optional<_Tp>' and 'std::nullptr_t' 3 | bool ok = std::shared_ptr<int>{} <=> nullptr; | ^~~~~~~ In file included from /opt/wandbox/gcc-head/include/c++/10.0.1/ranges:46, from /opt/wandbox/gcc-head/include/c++/10.0.1/bits/ranges_algobase.h:38, from /opt/wandbox/gcc-head/include/c++/10.0.1/bits/ranges_uninitialized.h:36, from /opt/wandbox/gcc-head/include/c++/10.0.1/memory:69, from prog.cc:1: /opt/wandbox/gcc-head/include/c++/10.0.1/tuple:1425:5: note: candidate: 'template<class ... _Tps, class ... _Ups> constexpr std::common_comparison_category_t<std::__detail::__synth3way_t<_Tps, _Ups>...> std::operator<=>(const std::tuple<_Tps ...>&, const std::tuple<_UTypes ...>&)' (reversed) 1425 | operator<=>(const tuple<_Tps...>& __t, const tuple<_Ups...>& __u) | ^~~~~~~~ /opt/wandbox/gcc-head/include/c++/10.0.1/tuple:1425:5: note: template argument deduction/substitution failed: prog.cc:3:38: note: mismatched types 'const std::tuple<_Tps ...>' and 'std::nullptr_t' 3 | bool ok = std::shared_ptr<int>{} <=> nullptr; | ^~~~~~~ In file included from /opt/wandbox/gcc-head/include/c++/10.0.1/memory:83, from prog.cc:1: /opt/wandbox/gcc-head/include/c++/10.0.1/bits/unique_ptr.h:893:5: note: candidate: 'template<class _Tp, class _Dp, class _Up, class _Ep> requires three_way_comparable_with<typename std::unique_ptr<_Tp, _Dp>::pointer, typename std::unique_ptr<_Up, _Ep>::pointer, std::partial_ordering> std::compare_three_way_result_t<typename std::unique_ptr<_Tp, _Dp>::pointer, typename std::unique_ptr<_Up, _Ep>::pointer> std::operator<=>(const std::unique_ptr<_Tp, _Dp>&, const std::unique_ptr<_Up, _Ep>&)' (reversed) 893 | operator<=>(const unique_ptr<_Tp, _Dp>& __x, | ^~~~~~~~ /opt/wandbox/gcc-head/include/c++/10.0.1/bits/unique_ptr.h:893:5: note: template argument deduction/substitution failed: prog.cc:3:38: note: mismatched types 'const std::unique_ptr<_Tp, _Dp>' and 'std::nullptr_t' 3 | bool ok = std::shared_ptr<int>{} <=> nullptr; | ^~~~~~~ In file included from /opt/wandbox/gcc-head/include/c++/10.0.1/memory:83, from prog.cc:1: /opt/wandbox/gcc-head/include/c++/10.0.1/bits/unique_ptr.h:900:5: note: candidate: 'template<class _Tp, class _Dp> requires three_way_comparable<typename std::unique_ptr<_Tp, _Dp>::pointer, std::partial_ordering> std::compare_three_way_result_t<typename std::unique_ptr<_Tp, _Dp>::pointer> std::operator<=>(const std::unique_ptr<_Tp, _Dp>&, std::nullptr_t)' (reversed) 900 | operator<=>(const unique_ptr<_Tp, _Dp>& __x, nullptr_t) | ^~~~~~~~ /opt/wandbox/gcc-head/include/c++/10.0.1/bits/unique_ptr.h:900:5: note: template argument deduction/substitution failed: prog.cc:3:38: note: mismatched types 'const std::unique_ptr<_Tp, _Dp>' and 'std::nullptr_t' 3 | bool ok = std::shared_ptr<int>{} <=> nullptr; | ^~~~~~~ In file included from /opt/wandbox/gcc-head/include/c++/10.0.1/bits/stl_algobase.h:64, from /opt/wandbox/gcc-head/include/c++/10.0.1/memory:63, from prog.cc:1: /opt/wandbox/gcc-head/include/c++/10.0.1/bits/stl_pair.h:472:5: note: candidate: 'template<class _T1, class _T2> constexpr std::common_comparison_category_t<decltype (std::__detail::__synth3way(declval<_T1&>(), declval<_T1&>())), decltype (std::__detail::__synth3way(declval<_T2&>(), declval<_T2&>()))> std::operator<=>(const std::pair<_T1, _T2>&, const std::pair<_T1, _T2>&)' 472 | operator<=>(const pair<_T1, _T2>& __x, const pair<_T1, _T2>& __y) | ^~~~~~~~ /opt/wandbox/gcc-head/include/c++/10.0.1/bits/stl_pair.h:472:5: note: template argument deduction/substitution failed: prog.cc:3:38: note: 'std::shared_ptr<int>' is not derived from 'const std::pair<_T1, _T2>' 3 | bool ok = std::shared_ptr<int>{} <=> nullptr; | ^~~~~~~ In file included from /opt/wandbox/gcc-head/include/c++/10.0.1/bits/ios_base.h:46, from /opt/wandbox/gcc-head/include/c++/10.0.1/streambuf:41, from /opt/wandbox/gcc-head/include/c++/10.0.1/bits/streambuf_iterator.h:35, from /opt/wandbox/gcc-head/include/c++/10.0.1/iterator:66, from /opt/wandbox/gcc-head/include/c++/10.0.1/bits/ranges_algobase.h:36, from /opt/wandbox/gcc-head/include/c++/10.0.1/bits/ranges_uninitialized.h:36, from /opt/wandbox/gcc-head/include/c++/10.0.1/memory:69, from prog.cc:1: /opt/wandbox/gcc-head/include/c++/10.0.1/system_error:244:3: note: candidate: 'std::strong_ordering std::operator<=>(const std::error_code&, const std::error_code&)' 244 | operator<=>(const error_code& __lhs, const error_code& __rhs) noexcept | ^~~~~~~~ /opt/wandbox/gcc-head/include/c++/10.0.1/system_error:244:33: note: no known conversion for argument 1 from 'std::shared_ptr<int>' to 'const std::error_code&' 244 | operator<=>(const error_code& __lhs, const error_code& __rhs) noexcept | ~~~~~~~~~~~~~~~~~~^~~~~ /opt/wandbox/gcc-head/include/c++/10.0.1/system_error:368:3: note: candidate: 'std::strong_ordering std::operator<=>(const std::error_condition&, const std::error_condition&)' 368 | operator<=>(const error_condition& __lhs, | ^~~~~~~~ /opt/wandbox/gcc-head/include/c++/10.0.1/system_error:368:38: note: no known conversion for argument 1 from 'std::shared_ptr<int>' to 'const std::error_condition&' 368 | operator<=>(const error_condition& __lhs, | ~~~~~~~~~~~~~~~~~~~~~~~^~~~~ In file included from /opt/wandbox/gcc-head/include/c++/10.0.1/tuple:39, from /opt/wandbox/gcc-head/include/c++/10.0.1/ranges:46, from /opt/wandbox/gcc-head/include/c++/10.0.1/bits/ranges_algobase.h:38, from /opt/wandbox/gcc-head/include/c++/10.0.1/bits/ranges_uninitialized.h:36, from /opt/wandbox/gcc-head/include/c++/10.0.1/memory:69, from prog.cc:1: /opt/wandbox/gcc-head/include/c++/10.0.1/array:259:5: note: candidate: 'template<class _Tp, long unsigned int _Nm> constexpr std::__detail::__synth3way_t<_T1> std::operator<=>(const std::array<_Tp, _Nm>&, const std::array<_Tp, _Nm>&)' 259 | operator<=>(const array<_Tp, _Nm>& __a, const array<_Tp, _Nm>& __b) | ^~~~~~~~ /opt/wandbox/gcc-head/include/c++/10.0.1/array:259:5: note: template argument deduction/substitution failed: prog.cc:3:38: note: 'std::shared_ptr<int>' is not derived from 'const std::array<_Tp, _Nm>' 3 | bool ok = std::shared_ptr<int>{} <=> nullptr; | ^~~~~~~ 1 >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> The problem is due to a Standard library specification problem, see https://cplusplus.github.io/LWG/issue3427