Re: [PATCH][_GLIBCXX_DEBUG] Remove useless checks

[Jonathan Wakely <jwakely@redhat.com>]

On Mon, 23 Jan 2023 at 06:02, François Dumont via Libstdc++
<libstdc++@gcc.gnu.org> wrote:
>
>      libstdc++: [_GLIBCXX_DEBUG] Remove useless constructor checks
>
>      Creating a safe iterator from a normal iterator is done within the
> library where we
>      already know that it is done correctly. The rare situation where a
> user would use safe
>      iterators for his own purpose is non-Standard code so outside
> _GLIBCXX_DEBUG scope. For
>      those reasons the __msg_init_singular is useless and can be removed.
>
>      Additionally in the copy constructor used for post-increment and
> post-decrement operators
>      the __msg_init_copy_singular check can also be ommitted because of
> the preliminary
>      __msg_bad_inc and __msg_bad_dec checks.
>
>      libstdc++-v3/ChangeLog:
>
>              * include/debug/safe_iterator.h
> (_Safe_iterator<>::_Unsafe_call): New.

I don't like the name "unsafe call". Why is it unsafe? As you say
above, we don't need to check because we know that it's only called in
a context where it's safe. Can we call it _Unchecked instead of
_Unsafe_call? That seems like a more accurate description of the
behaviour.


>              (_Safe_iterator(const _Safe_iterator&, _Unsafe_call): New.
>              (_Safe_iterator::operator++(int)): Use latter.
>              (_Safe_iterator::operator--(int)): Likewise.
>              (_Safe_iterator(_Iterator, const _Safe_sequence_base*)):
> Remove !_M_insular()
>              check.
>              * include/debug/safe_local_iterator.h
> (_Safe_local_iterator<>::_Unsafe_call):
>              New.
>              (_Safe_local_iterator(const _Safe_local_iterator&,
> _Unsafe_call): New.
>              (_Safe_local_iterator::operator++(int)): Use latter.
>              * src/c++11/debug.cc (_S_debug_messages): Add as comment
> the _Debug_msg_id
>              entry associated to the array entry.

These comments are a great idea, thanks.

If you agree with the _Unchecked name, OK to commit with that change.