https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94164
Bug ID: 94164
Summary: [Regression 10] std::unintialized_fill_n fails to
compile
Product: gcc
Version: 10.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: libstdc++
Assignee: unassigned at gcc dot gnu.org
Reporter: laurent.stacul at gmail dot com
Target Milestone: ---
Hello,
I have this piece of code:
#include <memory>
template<typename T>
struct ref {
typedef T value_type;
typedef T* pointer;
typedef T& reference;
typedef ptrdiff_t difference_type;
typedef std::random_access_iterator_tag iterator_category;
int d;
explicit ref(int =0): d(-1) {}
operator pointer() {
if (d == -1) {
return 0;
}
else
{
return reinterpret_cast<pointer>(this + d);
}
}
ref& operator++() {
d += sizeof(value_type);
return *this;
}
};
int main(int, const char *[])
{
ref<char> r;
std::uninitialized_fill_n(r, 10, 'a');
return 0;
}
I compile it with the following command (the -std option is not important):
$ g++ -Wall -Wextra -std=gnu++2a -c -o main.o main.cpp
When I compile it with gcc (GCC) 10.0.1 20200305, if fails with the following
error:
/x86_64-v20.0.13/include/c++/10.0.1/bits/stl_algobase.h: In instantiation of
'constexpr _OutputIterator std::__fill_n_a(_OutputIterator, _Size, const _Tp&,
std::random_access_iterator_tag) [with _OutputIterator = ref<char>; _Size =
int; _Tp = char]':
/x86_64-v20.0.13/include/c++/10.0.1/bits/stl_algobase.h:1085:29: required
from 'constexpr _OI std::fill_n(_OI, _Size, const _Tp&) [with _OI = ref<char>;
_Size = int; _Tp = char]'
/x86_64-v20.0.13/include/c++/10.0.1/bits/stl_uninitialized.h:254:29: required
from 'static _ForwardIterator
std::__uninitialized_fill_n<true>::__uninit_fill_n(_ForwardIterator, _Size,
const _Tp&) [with _ForwardIterator = ref<char>; _Size = int; _Tp = c
har]'
/x86_64-v20.0.13/include/c++/10.0.1/bits/stl_uninitialized.h:289:17: required
from '_ForwardIterator std::uninitialized_fill_n(_ForwardIterator, _Size, const
_Tp&) [with _ForwardIterator = ref<char>; _Size = int; _Tp = char]'
main.cpp:32:41: required from here
/x86_64-v20.0.13/include/c++/10.0.1/bits/stl_algobase.h:1056:20: error: no
matching function for call to '__fill_a(ref<char>&, ref<char>::pointer, const
char&)'
1056 | std::__fill_a(__first, __first + __n, __value);
| ~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/x86_64-v20.0.13/include/c++/10.0.1/bits/stl_algobase.h:904:5: note: candidate:
'template<class _FIte, class _Tp> constexpr void std::__fill_a(_FIte, _FIte,
const _Tp&)'
904 | __fill_a(_FIte __first, _FIte __last, const _Tp& __value)
| ^~~~~~~~
/x86_64-v20.0.13/include/c++/10.0.1/bits/stl_algobase.h:904:5: note: template
argument deduction/substitution failed:
/x86_64-v20.0.13/include/c++/10.0.1/bits/stl_algobase.h:1056:20: note:
deduced conflicting types for parameter '_FIte' ('ref<char>' and 'char*')
1056 | std::__fill_a(__first, __first + __n, __value);
| ~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/x86_64-v20.0.13/include/c++/10.0.1/bits/stl_algobase.h:909:5: note: candidate:
'template<class _Ite, class _Seq, class _Cat, class _Tp> void
std::__fill_a(const __gnu_debug::_Safe_iterator<_Ite, _Seq, _Cat>&, const
__gnu_debug::_Safe_iterator<_Ite, _Seq
, _Cat>&, const _Tp&)'
909 | __fill_a(const ::__gnu_debug::_Safe_iterator<_Ite, _Seq, _Cat>&,
| ^~~~~~~~
/x86_64-v20.0.13/include/c++/10.0.1/bits/stl_algobase.h:909:5: note: template
argument deduction/substitution failed:
/x86_64-v20.0.13/include/c++/10.0.1/bits/stl_algobase.h:1056:20: note:
'ref<char>' is not derived from 'const __gnu_debug::_Safe_iterator<_Ite, _Seq,
_Cat>'
1056 | std::__fill_a(__first, __first + __n, __value);
| ~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/x86_64-v20.0.13/include/c++/10.0.1/bits/stl_algobase.h:1057:22: error: could
not convert '(__first.ref<char>::operator ref<char>::pointer() +
((sizetype)__n))' from 'ref<char>::pointer' {aka 'char*'} to 'ref<char>'
1057 | return __first + __n;
| ~~~~~~~~^~~~~
| |
| ref<char>::pointer {aka char*}
make: *** [Makefile:6: main.o] Error 1
Conversely, this code compiles with gcc (GCC) 9.2.1.
Maybe is it related to
https://gcc.gnu.org/git/?p=gcc.git;a=commit;h=6004c17b4d1a2dd1e1936b2e705a5ccfb6e48ab2
but I don' t know if the current bahviour is expected.
Stac
