https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104546
Bug ID: 104546
Summary: std::reference_wrapper doesn't compile with clang in
some circumstances
Product: gcc
Version: 11.2.1
Status: UNCONFIRMED
Keywords: rejects-valid
Severity: normal
Priority: P3
Component: libstdc++
Assignee: unassigned at gcc dot gnu.org
Reporter: redi at gcc dot gnu.org
Target Milestone: ---
#include <functional>
#include <vector>
#include <algorithm>
int main() {
std::function<bool(const int&, const int&)> comp
= [](const int& a, const int& b) { return a < b; };
std::vector<int> vec;
std::sort(vec.begin(), vec.end(), std::ref(comp)); // Doesn't compile
}
This fails with clang due to https://github.com/llvm/llvm-project/issues/53049
In file included from repro.cc:1:
In file included from
/usr/lib/gcc/x86_64-redhat-linux/11/../../../../include/c++/11/functional:58:
/usr/lib/gcc/x86_64-redhat-linux/11/../../../../include/c++/11/bits/refwrap.h:319:40:
error: exception specification of
'function<__gnu_cxx::__ops::_Iter_comp_iter<std::reference_wrapper<std::function<bool
(const int &, const int &)>>>, void>' uses itself
= decltype(reference_wrapper::_S_fun(std::declval<_Up>()))>
^
/usr/lib/gcc/x86_64-redhat-linux/11/../../../../include/c++/11/bits/refwrap.h:319:40:
note: in instantiation of exception specification for
'function<__gnu_cxx::__ops::_Iter_comp_iter<std::reference_wrapper<std::function<bool
(const int &, const int &)>>>, void>' requested here
/usr/lib/gcc/x86_64-redhat-linux/11/../../../../include/c++/11/bits/refwrap.h:321:2:
note: in instantiation of default argument for
'reference_wrapper<__gnu_cxx::__ops::_Iter_comp_iter<std::reference_wrapper<std::function<bool
(const int &, const int &)>>>, void>' required here
reference_wrapper(_Up&& __uref)
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/usr/lib/gcc/x86_64-redhat-linux/11/../../../../include/c++/11/type_traits:1017:57:
note: while substituting deduced template arguments into function template
'reference_wrapper' [with _Up =
__gnu_cxx::__ops::_Iter_comp_iter<std::reference_wrapper<std::function<bool
(const int &, const int &)>>>, $1 = (no value), $2 = (no value)]
= __bool_constant<__is_nothrow_constructible(_Tp, _Args...)>;
^
/usr/lib/gcc/x86_64-redhat-linux/11/../../../../include/c++/11/type_traits:1023:14:
note: in instantiation of template type alias '__is_nothrow_constructible_impl'
requested here
: public __is_nothrow_constructible_impl<_Tp, _Args...>::type
^
/usr/lib/gcc/x86_64-redhat-linux/11/../../../../include/c++/11/type_traits:153:14:
note: in instantiation of template class
'std::is_nothrow_constructible<__gnu_cxx::__ops::_Iter_comp_iter<std::reference_wrapper<std::function<bool
(const int &, const int &)>>>,
__gnu_cxx::__ops::_Iter_comp_iter<std::reference_wrapper<std::function<bool
(const int &, const int &)>>>>' requested here
: public conditional<_B1::value, _B2, _B1>::type
^
/usr/lib/gcc/x86_64-redhat-linux/11/../../../../include/c++/11/bits/std_function.h:298:11:
note: (skipping 7 contexts in backtrace; use -ftemplate-backtrace-limit=0 to
see all)
return __and_<typename _Base::_Local_storage,
^
/usr/lib/gcc/x86_64-redhat-linux/11/../../../../include/c++/11/bits/stl_algo.h:1917:12:
note: in instantiation of function template specialization
'std::__heap_select<__gnu_cxx::__normal_iterator<int *, std::vector<int>>,
__gnu_cxx::__ops::_Iter_comp_iter<std::reference_wrapper<std::function<bool
(const int &, const int &)>>>>' requested here
std::__heap_select(__first, __middle, __last, __comp);
^
/usr/lib/gcc/x86_64-redhat-linux/11/../../../../include/c++/11/bits/stl_algo.h:1933:13:
note: in instantiation of function template specialization
'std::__partial_sort<__gnu_cxx::__normal_iterator<int *, std::vector<int>>,
__gnu_cxx::__ops::_Iter_comp_iter<std::reference_wrapper<std::function<bool
(const int &, const int &)>>>>' requested here
std::__partial_sort(__first, __last, __last, __comp);
^
/usr/lib/gcc/x86_64-redhat-linux/11/../../../../include/c++/11/bits/stl_algo.h:1954:9:
note: in instantiation of function template specialization
'std::__introsort_loop<__gnu_cxx::__normal_iterator<int *, std::vector<int>>,
long,
__gnu_cxx::__ops::_Iter_comp_iter<std::reference_wrapper<std::function<bool
(const int &, const int &)>>>>' requested here
std::__introsort_loop(__first, __last,
^
/usr/lib/gcc/x86_64-redhat-linux/11/../../../../include/c++/11/bits/stl_algo.h:4875:12:
note: in instantiation of function template specialization
'std::__sort<__gnu_cxx::__normal_iterator<int *, std::vector<int>>,
__gnu_cxx::__ops::_Iter_comp_iter<std::reference_wrapper<std::function<bool
(const int &, const int &)>>>>' requested here
std::__sort(__first, __last, __gnu_cxx::__ops::__iter_comp_iter(__comp));
^
repro.cc:10:10: note: in instantiation of function template specialization
'std::sort<__gnu_cxx::__normal_iterator<int *, std::vector<int>>,
std::reference_wrapper<std::function<bool (const int &, const int &)>>>'
requested here
std::sort(vec.begin(), vec.end(), std::ref(comp)); // Doesn't compile
^
1 error generated.
If possible we should try to workaround this.
