From: Jonathan Wakely <jwakely@redhat.com>
To: "Daniel Krügler" <daniel.kruegler@gmail.com>
Cc: "François Dumont" <frs.dumont@gmail.com>,
"libstdc++@gcc.gnu.org" <libstdc++@gcc.gnu.org>,
gcc-patches <gcc-patches@gcc.gnu.org>
Subject: Re: PR 90409 Deque fiil/copy/move/copy_backward/move_backward/equal overloads
Date: Thu, 01 Aug 2019 11:01:00 -0000 [thread overview]
Message-ID: <20190801110102.GP9487@redhat.com> (raw)
In-Reply-To: <CAGNvRgBsRonOWSwYFibyj7Dq-QCf+6EfC7sm5OcfU_AzbkUzLw@mail.gmail.com>
On 01/08/19 12:36 +0200, Daniel Krügler wrote:
>Am Do., 1. Aug. 2019 um 11:57 Uhr schrieb Jonathan Wakely <jwakely@redhat.com>:
>>
>> More comments inline below ...
>[..]
>>
>> >François
>> >
>> >On 6/19/19 7:32 PM, François Dumont wrote:
>> >>I wanted to implement Debug overloads for those already existing
>> >>overloads but then realized that those algos could be generalized.
>> >>This way we will benefit from the memmove replacement when operating
>> >>with C array or std::array or std::vector iterators.
>> >>
>> >>I might do the same for lexicographical_compare one day.
>> >>
>> >>The ChangeLog below is quite huge so I attached it. I wonder if I
>> >>could use deque::iterator and deque::const_iterator in place of the
>> >>_Deque_iterator<> to reduce it ?
>> >>
>> >>Tested under Linux x86_64 normal and debug modes, ok to commit ?
>> >>
>> >>François
>> >>
>> >
>>
>> >diff --git a/libstdc++-v3/include/bits/deque.tcc b/libstdc++-v3/include/bits/deque.tcc
>> >index 3f77b4f079c..9db869fb666 100644
>> >--- a/libstdc++-v3/include/bits/deque.tcc
>> >+++ b/libstdc++-v3/include/bits/deque.tcc
>> >@@ -967,155 +967,507 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>> > this->_M_impl._M_finish._M_set_node(__new_nstart + __old_num_nodes - 1);
>> > }
>> >
>[..]
>>
>> And anyway, isn't _Deque_iterator<T, T&, T*>::_Self just the same type as
>> _Deque_iterator<T, T&, T*> ? It should be something like:
>>
>> typedef typename _GLIBCXX_STD_C::_Deque_iterator<_Tp, _Tp&, _Tp*> _Iter;
>>
>> >+ template<typename _II, typename _Tp>
>> >+ typename enable_if<
>> >+ is_same<typename std::iterator_traits<_II>::iterator_category,
>> >+ std::random_access_iterator_tag>::value,
>>
>> Use is_base_of<random_access_iterator_tag, ...::iterator_category> so
>> it works for types derived from random_access_iterator_tag too.
>
>Interesting. Traditional type tag dispatching approaches (as function
>parameters) do have more in a manner that would be equivalent to an
>implicit conversion (Being used as "by-value-parameters"), so I'm
>wondering whether this should not instead refer to is_convertible? I
>also found examples where this trait is currently used in <stl_algo.h>
>such as
>
> static_assert(
> __or_<is_convertible<__pop_cat, forward_iterator_tag>,
> is_convertible<__samp_cat, random_access_iterator_tag>>::value,
> "output range must use a RandomAccessIterator when input range"
> " does not meet the ForwardIterator requirements");
>
>Should possibly this trait be preferred?
Hmm, I don't know why I did it that way in sample.
The standard requires derivation in a couple of places today, see
[reverse.iterator] bullet 2.1 and [move.iterator] bullet 1.1 which use
DerivedFrom<random_access_iterator_tag> to check whether the base
iterator is random access or not.
next prev parent reply other threads:[~2019-08-01 11:01 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-06-19 17:32 François Dumont
2019-06-20 8:38 ` Morwenn Ed
2019-06-21 4:43 ` François Dumont
2019-07-16 17:20 ` François Dumont
2019-07-26 9:13 ` PR 90409 " François Dumont
2019-08-01 9:57 ` Jonathan Wakely
2019-08-01 10:36 ` Daniel Krügler
2019-08-01 11:01 ` Jonathan Wakely [this message]
2019-08-01 11:31 ` Daniel Krügler
2019-08-01 12:52 ` Jonathan Wakely
2019-08-01 12:53 ` Jonathan Wakely
2019-08-21 21:18 ` François Dumont
2019-08-26 20:31 ` François Dumont
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