[Bug c++/91777] No warning for iterator going out of scope

[egallager at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=91777

--- Comment #8 from Eric Gallager <egallager at gcc dot gnu.org> ---
(In reply to Jonathan Wakely from comment #7)
> It's also diagnosed by libstdc++ Debug Mode:
> 
> /home/jwakely/gcc/10/include/c++/10.0.0/debug/safe_iterator.h:294:
> In function:
>     __gnu_debug::_Safe_iterator<_Iterator, _Sequence, _Category>::reference 
>     __gnu_debug::_Safe_iterator<_Iterator, _Sequence, 
>     _Category>::operator*() const [with _Iterator = 
>     std::__cxx1998::_List_const_iterator<int>; _Sequence = 
>     std::__debug::list<int>; _Category = std::forward_iterator_tag; 
>     __gnu_debug::_Safe_iterator<_Iterator, _Sequence, _Category>::reference 
>     = const int&]
> 
> Error: attempt to dereference a singular iterator.
> 
> Objects involved in the operation:
>     iterator "this" @ 0x0x7ffffb1db7f0 {
>       type = std::__cxx1998::_List_const_iterator<int> (constant iterator);
>       state = singular;
>     }
> Aborted (core dumped)
> 
> 
> I don't think it's feasible to warn about this. As far as the compiler
> knows, the iterator is just a value type. It's not practical to expect the
> compiler to track that it contains a pointer to a node that is about to be
> destroyed by a container going out of scope.

Maybe not in the compiler proper; could be material for someone to write a
plugin for...