Extend usage of C++11 direct init in __debug::vector

[François Dumont]

On 10/15/2018 12:10 PM, Jonathan Wakely wrote:
> On 15/10/18 07:23 +0200, François Dumont wrote:
>> This patch extend usage of C++11 direct initialization in 
>> __debug::vector and makes some calls to operator - more consistent.
>>
>> Note that I also rewrote following expression in erase method:
>>
>> -Â Â Â  Â  return begin() + (__first.base() - cbegin().base());
>> +Â Â Â  Â  return { _Base::begin() + (__first.base() - _Base::cbegin()), 
>> this };
>>
>> The latter version was building 2 safe iterators and incrementing 1 
>> with the additional debug check inherent to such an operation whereas 
>> the new version just build 1 safe iterator with directly the expected 
>> offset.
>
> Makes sense.
>
>> 2018-10-15  François Dumont <fdumont@gcc.gnu.org>
>>
>> Â Â Â  * include/debug/vector (vector<>::cbegin()): Use C++11 direct
>> Â Â Â  initialization.
>> Â Â Â  (vector<>::cend()): Likewise.
>> Â Â Â  (vector<>::emplace(const_iterator, _Args&&...)): Likewise and use
>> Â Â Â  consistent iterator comparison.
>> Â Â Â  (vector<>::insert(const_iterator, size_type, const _Tp&)): Likewise.
>> Â Â Â  (vector<>::insert(const_iterator, _InputIterator, _InputIterator)):
>> Â Â Â  Likewise.
>> Â Â Â  (vector<>::erase(const_iterator)): Likewise.
>> Â Â Â  (vector<>::erase(const_iterator, const_iterator)): Likewise.
>>
>> Tested under Linux x86_64 Debug mode and committed.
>>
>> François
>>
>
>> @@ -542,7 +542,8 @@ namespace __debug
>> Â Â Â Â Â  {
>> Â Â Â Â __glibcxx_check_insert(__position);
>> Â Â Â Â bool __realloc = this->_M_requires_reallocation(this->size() + 1);
>> -Â Â Â  difference_type __offset = __position.base() - _Base::begin();
>> +Â Â Â  difference_type __offset
>> +Â Â Â Â Â  = __position.base() - 
>> __position._M_get_sequence()->_M_base().begin();
>
> What's the reason for this change?
>
> Doesn't __glibcxx_check_insert(__position) already ensure that
> __position is attached to *this, and so _Base::begin() returns the
> same thing as __position._M_get_sequence()->_M_base().begin() ?
>
> If they're equivalent, the original code seems more readable.
>
>
>
This is the consistent iterator comparison part. Depending on C++ mode 
__position can be iterator or const_iterator.

As _M_get_sequence() return type depends on iterator type we always have 
iterator - iterator or const_iterator - const_iterator so no conversion.