https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113745
Bug ID: 113745
Summary: Poor diagnostics quality for resize() without a
default-constructible type
Product: gcc
Version: 14.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: janschultke at googlemail dot com
Target Milestone: ---
## Code to reproduce (https://godbolt.org/z/6ETnffr8c)
#include <vector>
struct non_default_constructible {
non_default_constructible(int) {}
};
int main() {
std::vector<non_default_constructible> v;
v.resize(0);
}
## Diagnostic
In file included from
/opt/compiler-explorer/gcc-trunk-20240203/include/c++/14.0.1/bits/stl_iterator.h:78,
from
/opt/compiler-explorer/gcc-trunk-20240203/include/c++/14.0.1/bits/stl_algobase.h:67,
from
/opt/compiler-explorer/gcc-trunk-20240203/include/c++/14.0.1/vector:62,
from <source>:1:
/opt/compiler-explorer/gcc-trunk-20240203/include/c++/14.0.1/bits/stl_construct.h:
In instantiation of 'constexpr void std::_Construct(_Tp*, _Args&& ...) [with
_Tp = non_default_constructible; _Args = {}]':
/opt/compiler-explorer/gcc-trunk-20240203/include/c++/14.0.1/bits/stl_uninitialized.h:643:18:
required from 'static constexpr _ForwardIterator
std::__uninitialized_default_n_1<_TrivialValueType>::__uninit_default_n(_ForwardIterator,
_Size) [with _ForwardIterator = non_default_constructible*; _Size = long
unsigned int; bool _TrivialValueType = false]'
643 | std::_Construct(std::__addressof(*__cur));
| ~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~
/opt/compiler-explorer/gcc-trunk-20240203/include/c++/14.0.1/bits/stl_uninitialized.h:701:22:
required from 'constexpr _ForwardIterator
std::__uninitialized_default_n(_ForwardIterator, _Size) [with _ForwardIterator
= non_default_constructible*; _Size = long unsigned int]'
700 | return __uninitialized_default_n_1<false>::
| ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
701 | __uninit_default_n(__first, __n);
| ~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~
/opt/compiler-explorer/gcc-trunk-20240203/include/c++/14.0.1/bits/stl_uninitialized.h:779:44:
required from 'constexpr _ForwardIterator
std::__uninitialized_default_n_a(_ForwardIterator, _Size, allocator<_Tp>&)
[with _ForwardIterator = non_default_constructible*; _Size = long unsigned int;
_Tp = non_default_constructible]'
779 | { return std::__uninitialized_default_n(__first, __n); }
| ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~
/opt/compiler-explorer/gcc-trunk-20240203/include/c++/14.0.1/bits/vector.tcc:821:35:
required from 'constexpr void std::vector<_Tp,
_Alloc>::_M_default_append(size_type) [with _Tp = non_default_constructible;
_Alloc = std::allocator<non_default_constructible>; size_type = long unsigned
int]'
821 |
std::__uninitialized_default_n_a(this->_M_impl._M_finish,
|
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~
822 | __n,
_M_get_Tp_allocator());
|
~~~~~~~~~~~~~~~~~~~~~~~~~~~
/opt/compiler-explorer/gcc-trunk-20240203/include/c++/14.0.1/bits/stl_vector.h:1013:4:
required from 'constexpr void std::vector<_Tp, _Alloc>::resize(size_type)
[with _Tp = non_default_constructible; _Alloc =
std::allocator<non_default_constructible>; size_type = long unsigned int]'
1013 | _M_default_append(__new_size - size());
| ^~~~~~~~~~~~~~~~~
<source>:9:13: required from here
9 | v.resize(0);
| ~~~~~~~~^~~
/opt/compiler-explorer/gcc-trunk-20240203/include/c++/14.0.1/bits/stl_construct.h:115:28:
error: no matching function for call to
'construct_at(non_default_constructible*&)'
115 | std::construct_at(__p, std::forward<_Args>(__args)...);
| ~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/opt/compiler-explorer/gcc-trunk-20240203/include/c++/14.0.1/bits/stl_construct.h:94:5:
note: candidate: 'template<class _Tp, class ... _Args> constexpr decltype
(::new(void*(0)) _Tp) std::construct_at(_Tp*, _Args&& ...)'
94 | construct_at(_Tp* __location, _Args&&... __args)
| ^~~~~~~~~~~~
/opt/compiler-explorer/gcc-trunk-20240203/include/c++/14.0.1/bits/stl_construct.h:94:5:
note: template argument deduction/substitution failed:
/opt/compiler-explorer/gcc-trunk-20240203/include/c++/14.0.1/bits/stl_construct.h:
In substitution of 'template<class _Tp, class ... _Args> constexpr decltype
(::new(void*(0)) _Tp) std::construct_at(_Tp*, _Args&& ...) [with _Tp =
non_default_constructible; _Args = {}]':
/opt/compiler-explorer/gcc-trunk-20240203/include/c++/14.0.1/bits/stl_construct.h:115:21:
required from 'constexpr void std::_Construct(_Tp*, _Args&& ...) [with _Tp =
non_default_constructible; _Args = {}]'
/opt/compiler-explorer/gcc-trunk-20240203/include/c++/14.0.1/bits/stl_construct.h:94:5:
note: 115 | std::construct_at(__p, std::forward<_Args>(__args)...);
/opt/compiler-explorer/gcc-trunk-20240203/include/c++/14.0.1/bits/stl_construct.h:94:5:
note: | ~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/opt/compiler-explorer/gcc-trunk-20240203/include/c++/14.0.1/bits/stl_uninitialized.h:643:18:
required from 'static constexpr _ForwardIterator
std::__uninitialized_default_n_1<_TrivialValueType>::__uninit_default_n(_ForwardIterator,
_Size) [with _ForwardIterator = non_default_constructible*; _Size = long
unsigned int; bool _TrivialValueType = false]'
/opt/compiler-explorer/gcc-trunk-20240203/include/c++/14.0.1/bits/stl_construct.h:94:5:
note: 643 | std::_Construct(std::__addressof(*__cur));
/opt/compiler-explorer/gcc-trunk-20240203/include/c++/14.0.1/bits/stl_construct.h:94:5:
note: | ~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~
/opt/compiler-explorer/gcc-trunk-20240203/include/c++/14.0.1/bits/stl_uninitialized.h:701:22:
required from 'constexpr _ForwardIterator
std::__uninitialized_default_n(_ForwardIterator, _Size) [with _ForwardIterator
= non_default_constructible*; _Size = long unsigned int]'
/opt/compiler-explorer/gcc-trunk-20240203/include/c++/14.0.1/bits/stl_construct.h:94:5:
note: 700 | return __uninitialized_default_n_1<false>::
/opt/compiler-explorer/gcc-trunk-20240203/include/c++/14.0.1/bits/stl_construct.h:94:5:
note: | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
701 | __uninit_default_n(__first, __n);
/opt/compiler-explorer/gcc-trunk-20240203/include/c++/14.0.1/bits/stl_construct.h:94:5:
note: | ~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~
/opt/compiler-explorer/gcc-trunk-20240203/include/c++/14.0.1/bits/stl_uninitialized.h:779:44:
required from 'constexpr _ForwardIterator
std::__uninitialized_default_n_a(_ForwardIterator, _Size, allocator<_Tp>&)
[with _ForwardIterator = non_default_constructible*; _Size = long unsigned int;
_Tp = non_default_constructible]'
/opt/compiler-explorer/gcc-trunk-20240203/include/c++/14.0.1/bits/stl_construct.h:94:5:
note: 779 | { return std::__uninitialized_default_n(__first, __n); }
/opt/compiler-explorer/gcc-trunk-20240203/include/c++/14.0.1/bits/stl_construct.h:94:5:
note: | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~
/opt/compiler-explorer/gcc-trunk-20240203/include/c++/14.0.1/bits/vector.tcc:821:35:
required from 'constexpr void std::vector<_Tp,
_Alloc>::_M_default_append(size_type) [with _Tp = non_default_constructible;
_Alloc = std::allocator<non_default_constructible>; size_type = long unsigned
int]'
/opt/compiler-explorer/gcc-trunk-20240203/include/c++/14.0.1/bits/stl_construct.h:94:5:
note: 821 |
std::__uninitialized_default_n_a(this->_M_impl._M_finish,
/opt/compiler-explorer/gcc-trunk-20240203/include/c++/14.0.1/bits/stl_construct.h:94:5:
note: |
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~
822 | __n,
_M_get_Tp_allocator());
/opt/compiler-explorer/gcc-trunk-20240203/include/c++/14.0.1/bits/stl_construct.h:94:5:
note: |
~~~~~~~~~~~~~~~~~~~~~~~~~~~
/opt/compiler-explorer/gcc-trunk-20240203/include/c++/14.0.1/bits/stl_vector.h:1013:4:
required from 'constexpr void std::vector<_Tp, _Alloc>::resize(size_type)
[with _Tp = non_default_constructible; _Alloc =
std::allocator<non_default_constructible>; size_type = long unsigned int]'
/opt/compiler-explorer/gcc-trunk-20240203/include/c++/14.0.1/bits/stl_construct.h:94:5:
note: 1013 | _M_default_append(__new_size - size());
/opt/compiler-explorer/gcc-trunk-20240203/include/c++/14.0.1/bits/stl_construct.h:94:5:
note: | ^~~~~~~~~~~~~~~~~
<source>:9:13: required from here
/opt/compiler-explorer/gcc-trunk-20240203/include/c++/14.0.1/bits/stl_construct.h:94:5:
note: 9 | v.resize(0);
/opt/compiler-explorer/gcc-trunk-20240203/include/c++/14.0.1/bits/stl_construct.h:94:5:
note: | ~~~~~~~~^~~
/opt/compiler-explorer/gcc-trunk-20240203/include/c++/14.0.1/bits/stl_construct.h:96:17:
error: no matching function for call to
'non_default_constructible::non_default_constructible()'
96 | -> decltype(::new((void*)0) _Tp(std::declval<_Args>()...))
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
<source>:4:5: note: candidate:
'non_default_constructible::non_default_constructible(int)'
4 | non_default_constructible(int) {}
| ^~~~~~~~~~~~~~~~~~~~~~~~~
<source>:4:5: note: candidate expects 1 argument, 0 provided
<source>:3:8: note: candidate: 'constexpr
non_default_constructible::non_default_constructible(const
non_default_constructible&)'
3 | struct non_default_constructible {
| ^~~~~~~~~~~~~~~~~~~~~~~~~
<source>:3:8: note: candidate expects 1 argument, 0 provided
<source>:3:8: note: candidate: 'constexpr
non_default_constructible::non_default_constructible(non_default_constructible&&)'
<source>:3:8: note: candidate expects 1 argument, 0 provided
/opt/compiler-explorer/gcc-trunk-20240203/include/c++/14.0.1/bits/stl_construct.h:
In instantiation of 'constexpr void std::_Construct(_Tp*, _Args&& ...) [with
_Tp = non_default_constructible; _Args = {}]':
/opt/compiler-explorer/gcc-trunk-20240203/include/c++/14.0.1/bits/stl_uninitialized.h:643:18:
required from 'static constexpr _ForwardIterator
std::__uninitialized_default_n_1<_TrivialValueType>::__uninit_default_n(_ForwardIterator,
_Size) [with _ForwardIterator = non_default_constructible*; _Size = long
unsigned int; bool _TrivialValueType = false]'
<source>:3:8: note: 643 |
std::_Construct(std::__addressof(*__cur));
<source>:3:8: note: |
~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~
/opt/compiler-explorer/gcc-trunk-20240203/include/c++/14.0.1/bits/stl_uninitialized.h:701:22:
required from 'constexpr _ForwardIterator
std::__uninitialized_default_n(_ForwardIterator, _Size) [with _ForwardIterator
= non_default_constructible*; _Size = long unsigned int]'
<source>:3:8: note: 700 | return __uninitialized_default_n_1<false>::
<source>:3:8: note: | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
701 | __uninit_default_n(__first, __n);
<source>:3:8: note: | ~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~
/opt/compiler-explorer/gcc-trunk-20240203/include/c++/14.0.1/bits/stl_uninitialized.h:779:44:
required from 'constexpr _ForwardIterator
std::__uninitialized_default_n_a(_ForwardIterator, _Size, allocator<_Tp>&)
[with _ForwardIterator = non_default_constructible*; _Size = long unsigned int;
_Tp = non_default_constructible]'
<source>:3:8: note: 779 | { return
std::__uninitialized_default_n(__first, __n); }
<source>:3:8: note: |
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~
/opt/compiler-explorer/gcc-trunk-20240203/include/c++/14.0.1/bits/vector.tcc:821:35:
required from 'constexpr void std::vector<_Tp,
_Alloc>::_M_default_append(size_type) [with _Tp = non_default_constructible;
_Alloc = std::allocator<non_default_constructible>; size_type = long unsigned
int]'
<source>:3:8: note: 821 |
std::__uninitialized_default_n_a(this->_M_impl._M_finish,
<source>:3:8: note: |
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~
822 | __n,
_M_get_Tp_allocator());
<source>:3:8: note: |
~~~~~~~~~~~~~~~~~~~~~~~~~~~
/opt/compiler-explorer/gcc-trunk-20240203/include/c++/14.0.1/bits/stl_vector.h:1013:4:
required from 'constexpr void std::vector<_Tp, _Alloc>::resize(size_type)
[with _Tp = non_default_constructible; _Alloc =
std::allocator<non_default_constructible>; size_type = long unsigned int]'
<source>:3:8: note: 1013 | _M_default_append(__new_size - size());
<source>:3:8: note: | ^~~~~~~~~~~~~~~~~
<source>:9:13: required from here
<source>:3:8: note: 9 | v.resize(0);
<source>:3:8: note: | ~~~~~~~~^~~
/opt/compiler-explorer/gcc-trunk-20240203/include/c++/14.0.1/bits/stl_construct.h:119:7:
error: no matching function for call to
'non_default_constructible::non_default_constructible()'
119 | ::new((void*)__p) _Tp(std::forward<_Args>(__args)...);
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
<source>:4:5: note: candidate:
'non_default_constructible::non_default_constructible(int)'
4 | non_default_constructible(int) {}
| ^~~~~~~~~~~~~~~~~~~~~~~~~
<source>:4:5: note: candidate expects 1 argument, 0 provided
<source>:3:8: note: candidate: 'constexpr
non_default_constructible::non_default_constructible(const
non_default_constructible&)'
3 | struct non_default_constructible {
| ^~~~~~~~~~~~~~~~~~~~~~~~~
<source>:3:8: note: candidate expects 1 argument, 0 provided
<source>:3:8: note: candidate: 'constexpr
non_default_constructible::non_default_constructible(non_default_constructible&&)'
<source>:3:8: note: candidate expects 1 argument, 0 provided
Compiler returned: 1
## Explanation
I find that this diagnostic is extremely confusing and verbose for what it is.
The issue is that non_default_construtible is not Cpp17DefaultInsertable, which
is required by resize() (https://eel.is/c++draft/vector.capacity#14).
Maybe we could add a static_assert to resize() which informs the user about the
issue more concisely.
