[patch] libstdc++/29988 Rb_Tree reuse allocated nodes

[François Dumont]

Hi

     Here is another proposal taking into account your remarks except 
the one below.

     In fact I had no problem with lambda, I just needed to store them 
in a variable, lambda do not need to be made mutable.

On 11/06/2014 14:02, Jonathan Wakely wrote:
>
>> @@ -514,11 +651,11 @@
>>       { return this->_M_impl._M_header._M_right; }
>>
>>       _Link_type
>> -      _M_begin() _GLIBCXX_NOEXCEPT
>> +      _M_begin() const _GLIBCXX_NOEXCEPT
>>       { return 
>> static_cast<_Link_type>(this->_M_impl._M_header._M_parent); }
>
> What's the purpose of this change?
> Although it can be 'const' it is consistent with the usual
> begin()/end() functions that the functions returning a mutable iterator
> are non-const and the functions returning a constant iterator are const.
>
>>       _Const_Link_type
>> -      _M_begin() const _GLIBCXX_NOEXCEPT
>> +      _M_cbegin() const _GLIBCXX_NOEXCEPT
>>       {
>>     return static_cast<_Const_Link_type>
>>       (this->_M_impl._M_header._M_parent);
>> @@ -529,7 +666,7 @@
>>       { return reinterpret_cast<_Link_type>(&this->_M_impl._M_header); }
>>
>>       _Const_Link_type
>> -      _M_end() const _GLIBCXX_NOEXCEPT
>> +      _M_cend() const _GLIBCXX_NOEXCEPT
>>       { return 
>> reinterpret_cast<_Const_Link_type>(&this->_M_impl._M_header); }
>>
>>       static const_reference
>
> I'm not very comfortable with this renaming.
>
> Having consistent _M_begin() functions allows using them in template
> code that doesn't care if it's using the const or non-const version.
>
>
I try to revert this part and so remember why I did it in the first place.

I needed to change _M_copy signature to:

       _Link_type
       _M_copy(_Link_type __x, _Link_type __p)

     because I now use this method to also move the elements of the data 
structure, I cannot move from a _Const_Like_type so I change first 
parameter to _Link_type. I see that there are some code duplications to 
deal with _Const_Link_type and _Link_type in 2 different part of the 
code but I didn't want to duplicate again here and simply made _M_copy 
more more flexible by taking a _Link_type rather than a _Const_Link_type.

     I don't really see interest of the existing code duplications so I 
prefer to not do the same and write the code only once.

François

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