https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113841
Bug ID: 113841
Summary: Can't swap two std::hash<T*>
Product: gcc
Version: 12.1.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: libstdc++
Assignee: unassigned at gcc dot gnu.org
Reporter: ostash at ostash dot kiev.ua
Target Milestone: ---
For the following code snippet:
---
#include <array>
#include <vector>
class Storage;
template <typename T>
class MyAllocator
{
public:
using value_type = T;
using pointer = T*;
MyAllocator(Storage* s);
template <typename U>
MyAllocator(MyAllocator<U> const& other) noexcept;
T* allocate( std::size_t n );
void deallocate(T* p, std::size_t n );
private:
Storage* s_;
};
class Foo{
public:
Foo(int, int);
};
void x() {
using std::swap;
using MyVec = std::vector<int, MyAllocator<int>>;
using MyArrVec = std::array<MyVec, 1>;
using MyHash = std::hash<std::pair<const int, MyArrVec>*>;
MyHash h1, h2;
swap(h1, h2);
}
---
GCC 12 reports:
In file included from
/opt/compiler-explorer/gcc-12.1.0/include/c++/12.1.0/vector:64,
from <source>:2:
/opt/compiler-explorer/gcc-12.1.0/include/c++/12.1.0/bits/stl_vector.h: In
instantiation of 'constexpr std::_Vector_base<_Tp,
_Alloc>::_Vector_impl::_Vector_impl() [with _Tp = int; _Alloc =
MyAllocator<int>]':
/opt/compiler-explorer/gcc-12.1.0/include/c++/12.1.0/bits/stl_vector.h:312:7:
required by substitution of 'template<class _Tp> static std::true_type
std::__do_is_implicitly_default_constructible_impl::__test(const _Tp&, decltype
(__helper<const _Tp&>(<brace-enclosed initializer list>()))*) [with _Tp =
std::array<std::vector<int, MyAllocator<int> >, 1>]'
/opt/compiler-explorer/gcc-12.1.0/include/c++/12.1.0/type_traits:1249:30:
required from 'struct
std::__is_implicitly_default_constructible_impl<std::array<std::vector<int,
MyAllocator<int> >, 1> >'
/opt/compiler-explorer/gcc-12.1.0/include/c++/12.1.0/type_traits:1253:12:
required from 'struct
std::__is_implicitly_default_constructible_safe<std::array<std::vector<int,
MyAllocator<int> >, 1> >'
/opt/compiler-explorer/gcc-12.1.0/include/c++/12.1.0/type_traits:167:12:
required from 'struct
std::__and_<std::__is_constructible_impl<std::array<std::vector<int,
MyAllocator<int> >, 1> >,
std::__is_implicitly_default_constructible_safe<std::array<std::vector<int,
MyAllocator<int> >, 1> > >'
/opt/compiler-explorer/gcc-12.1.0/include/c++/12.1.0/type_traits:1258:12:
required from 'struct
std::__is_implicitly_default_constructible<std::array<std::vector<int,
MyAllocator<int> >, 1> >'
/opt/compiler-explorer/gcc-12.1.0/include/c++/12.1.0/type_traits:167:12:
required from 'struct
std::__and_<std::__is_implicitly_default_constructible<const int>,
std::__is_implicitly_default_constructible<std::array<std::vector<int,
MyAllocator<int> >, 1> > >'
/opt/compiler-explorer/gcc-12.1.0/include/c++/12.1.0/type_traits:178:41:
required from 'struct
std::__not_<std::__and_<std::__is_implicitly_default_constructible<const int>,
std::__is_implicitly_default_constructible<std::array<std::vector<int,
MyAllocator<int> >, 1> > > >'
/opt/compiler-explorer/gcc-12.1.0/include/c++/12.1.0/bits/stl_pair.h:226:16:
required from 'struct std::pair<const int, std::array<std::vector<int,
MyAllocator<int> >, 1> >'
<source>:38:14: required from here
/opt/compiler-explorer/gcc-12.1.0/include/c++/12.1.0/type_traits:1240:58: in
'constexpr' expansion of 'std::vector<int, MyAllocator<int> >()'
/opt/compiler-explorer/gcc-12.1.0/include/c++/12.1.0/bits/stl_vector.h:526:7:
in 'constexpr' expansion of '((std::vector<int, MyAllocator<int>
>*)this)->std::vector<int, MyAllocator<int>
>::<anonymous>.std::_Vector_base<int, MyAllocator<int> >::_Vector_base()'
/opt/compiler-explorer/gcc-12.1.0/include/c++/12.1.0/bits/stl_vector.h:139:26:
error: no matching function for call to 'MyAllocator<int>::MyAllocator()'
139 | : _Tp_alloc_type()
| ^
<source>:16:3: note: candidate: 'template<class U>
MyAllocator<T>::MyAllocator(const MyAllocator<U>&) [with T = int]'
16 | MyAllocator(MyAllocator<U> const& other) noexcept;
| ^~~~~~~~~~~
<source>:16:3: note: template argument deduction/substitution failed:
/opt/compiler-explorer/gcc-12.1.0/include/c++/12.1.0/bits/stl_vector.h:139:26:
note: candidate expects 1 argument, 0 provided
139 | : _Tp_alloc_type()
| ^
<source>:13:3: note: candidate: 'MyAllocator<T>::MyAllocator(Storage*) [with T
= int]'
13 | MyAllocator(Storage* s);
| ^~~~~~~~~~~
<source>:13:3: note: candidate expects 1 argument, 0 provided
<source>:7:7: note: candidate: 'constexpr MyAllocator<int>::MyAllocator(const
MyAllocator<int>&)'
7 | class MyAllocator
| ^~~~~~~~~~~
<source>:7:7: note: candidate expects 1 argument, 0 provided
<source>:7:7: note: candidate: 'constexpr
MyAllocator<int>::MyAllocator(MyAllocator<int>&&)'
<source>:7:7: note: candidate expects 1 argument, 0 provided
Compiler returned: 1
Clang 15, 16, 17 also fail to compile with similar error about missing default
constructor for custom allocator when they are using libstdc++ >=12
GCC 13 is able to compile this, same as Clang with libc++.
