Re: [PATCH][_GLIBCXX_DEBUG] Fix std::__niter_base behavior

[Stephan Bergmann <sberg.fun@gmail.com>]

On 2/17/24 15:14, François Dumont wrote:
> Thanks for the link, tested and committed.

I assume this is the cause for the below failure now,

> $ cat test.cc
> #include <algorithm>
> #include <vector>
> void f(std::vector<void const *> &v, void const * p) {
>     std::erase(v, p);
> }

> $ ~/gcc/inst/bin/g++ -std=c++20 -D_GLIBCXX_DEBUG -fsyntax-only test.cc
> In file included from ~/gcc/inst/include/c++/14.0.1/algorithm:60,
>                  from test.cc:1:
> ~/gcc/inst/include/c++/14.0.1/bits/stl_algobase.h: In instantiation of ‘constexpr _From std::__niter_wrap(_From, _To) [with _From = __gnu_debug::_Safe_iterator<__gnu_cxx::__normal_iterator<const void**, __cxx1998::vector<const void*, allocator<const void*> > >, __debug::vector<const void*>, random_access_iterator_tag>; _To = __gnu_cxx::__normal_iterator<const void**, __cxx1998::vector<const void*, allocator<const void*> > >]’:
> ~/gcc/inst/include/c++/14.0.1/vector:144:29:   required from ‘constexpr typename std::__debug::vector<_Tp, _Allocator>::size_type std::erase(__debug::vector<_Tp, _Alloc>&, const _Up&) [with _Tp = const void*; _Alloc = allocator<const void*>; _Up = const void*; typename __debug::vector<_Tp, _Allocator>::size_type = long unsigned int]’
>   144 |           __cont.erase(__niter_wrap(__cont.begin(), __removed),
>       |                        ~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~
> test.cc:4:15:   required from here
>     4 |     std::erase(v, p);
>       |     ~~~~~~~~~~^~~~~~
> ~/gcc/inst/include/c++/14.0.1/bits/stl_algobase.h:347:30: error: no match for ‘operator-’ (operand types are ‘__gnu_cxx::__normal_iterator<const void**, std::__cxx1998::vector<const void*, std::allocator<const void*> > >’ and ‘const void**’)
>   347 |     { return __from + (__res - std::__niter_base(__from)); }
>       |                       ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~
> In file included from ~/gcc/inst/include/c++/14.0.1/bits/stl_algobase.h:67:
> ~/gcc/inst/include/c++/14.0.1/bits/stl_iterator.h:1148:7: note: candidate: ‘constexpr __gnu_cxx::__normal_iterator<_Iterator, _Container> __gnu_cxx::__normal_iterator<_Iterator, _Container>::operator-(difference_type) const [with _Iterator = const void**; _Container = std::__cxx1998::vector<const void*, std::allocator<const void*> >; difference_type = long int]’ (near match)
>  1148 |       operator-(difference_type __n) const _GLIBCXX_NOEXCEPT
>       |       ^~~~~~~~
> ~/gcc/inst/include/c++/14.0.1/bits/stl_iterator.h:1148:7: note:   conversion of argument 1 would be ill-formed:
> ~/gcc/inst/include/c++/14.0.1/bits/stl_algobase.h:347:49: error: invalid conversion from ‘const void**’ to ‘__gnu_cxx::__normal_iterator<const void**, std::__cxx1998::vector<const void*, std::allocator<const void*> > >::difference_type’ {aka ‘long int’} [-fpermissive]
>   347 |     { return __from + (__res - std::__niter_base(__from)); }
>       |                                ~~~~~~~~~~~~~~~~~^~~~~~~~
>       |                                                 |
>       |                                                 const void**
> ~/gcc/inst/include/c++/14.0.1/bits/stl_iterator.h:618:5: note: candidate: ‘template<class _IteratorL, class _IteratorR> constexpr decltype ((__y.base() - __x.base())) std::operator-(const reverse_iterator<_IteratorL>&, const reverse_iterator<_IteratorR>&)’
>   618 |     operator-(const reverse_iterator<_IteratorL>& __x,
>       |     ^~~~~~~~
> ~/gcc/inst/include/c++/14.0.1/bits/stl_iterator.h:618:5: note:   template argument deduction/substitution failed:
> ~/gcc/inst/include/c++/14.0.1/bits/stl_algobase.h:347:30: note:   ‘__gnu_cxx::__normal_iterator<const void**, std::__cxx1998::vector<const void*, std::allocator<const void*> > >’ is not derived from ‘const std::reverse_iterator<_IteratorL>’
>   347 |     { return __from + (__res - std::__niter_base(__from)); }
>       |                       ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~
> ~/gcc/inst/include/c++/14.0.1/bits/stl_iterator.h:1789:5: note: candidate: ‘template<class _IteratorL, class _IteratorR> constexpr decltype ((__x.base() - __y.base())) std::operator-(const move_iterator<_IteratorL>&, const move_iterator<_IteratorR>&)’
>  1789 |     operator-(const move_iterator<_IteratorL>& __x,
>       |     ^~~~~~~~
> ~/gcc/inst/include/c++/14.0.1/bits/stl_iterator.h:1789:5: note:   template argument deduction/substitution failed:
> ~/gcc/inst/include/c++/14.0.1/bits/stl_algobase.h:347:30: note:   ‘__gnu_cxx::__normal_iterator<const void**, std::__cxx1998::vector<const void*, std::allocator<const void*> > >’ is not derived from ‘const std::move_iterator<_IteratorL>’
>   347 |     { return __from + (__res - std::__niter_base(__from)); }
>       |                       ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~
> ~/gcc/inst/include/c++/14.0.1/bits/stl_iterator.h:1312:5: note: candidate: ‘template<class _IteratorL, class _IteratorR, class _Container> constexpr decltype ((__lhs.base() - __rhs.base())) __gnu_cxx::operator-(const __normal_iterator<_IteratorL, _Container>&, const __normal_iterator<_IteratorR, _Container>&)’
>  1312 |     operator-(const __normal_iterator<_IteratorL, _Container>& __lhs,
>       |     ^~~~~~~~
> ~/gcc/inst/include/c++/14.0.1/bits/stl_iterator.h:1312:5: note:   template argument deduction/substitution failed:
> ~/gcc/inst/include/c++/14.0.1/bits/stl_algobase.h:347:30: note:   mismatched types ‘const __gnu_cxx::__normal_iterator<_IteratorR, _Container>’ and ‘const void**’
>   347 |     { return __from + (__res - std::__niter_base(__from)); }
>       |                       ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~
> ~/gcc/inst/include/c++/14.0.1/bits/stl_iterator.h:1325:5: note: candidate: ‘template<class _Iterator, class _Container> constexpr typename __gnu_cxx::__normal_iterator<_Iterator, _Container>::difference_type __gnu_cxx::operator-(const __normal_iterator<_Iterator, _Container>&, const __normal_iterator<_Iterator, _Container>&)’
>  1325 |     operator-(const __normal_iterator<_Iterator, _Container>& __lhs,
>       |     ^~~~~~~~
> ~/gcc/inst/include/c++/14.0.1/bits/stl_iterator.h:1325:5: note:   template argument deduction/substitution failed:
> ~/gcc/inst/include/c++/14.0.1/bits/stl_algobase.h:347:30: note:   mismatched types ‘const __gnu_cxx::__normal_iterator<_Iterator, _Container>’ and ‘const void**’
>   347 |     { return __from + (__res - std::__niter_base(__from)); }
>       |                       ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~