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std::list custom allocator issues

 
 
ranin02
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      08-27-2007
Hi,

We have a list derived from std::list that has a custom allocator
derived from std::allocator. This was originally written using VC++
6.0 which required a workaround for the fact that 6.0 did not support
nested templates classes, so could not use the rebind struct.
Instead, a _Charalloc function was implemented.

Now that we are moving to VS 2005, this is no longer working so I need
to implement using the rebind struct. So I did this, and changed the
charalloc function to be a regular allocate function. But I am
running into problems, which I am thinking may be partly because the
allocator is taking two template parms. The template is declared as
follows:

template <class Ty, class _Node>
class CObjectPoolListAlloc : public std::allocator<Ty>

And I declared the rebind struct as follows:

template<class _Other>
struct rebind {
typedef CObjectPoolListAlloc<_Other, _Node> other;
};

And then I changed from using charalloc to an allocator declared as
follows:
_Node* allocate(size_type _N)

I am getting this error from the compiler:
error C2440: 'initializing' : cannot convert from
'std::_List_nod<_Ty,_Alloc>::_Node *' to
'std::_List_nod<_Ty,_Alloc>::_Node *'

Any thoughts?

Thanks,
Sherri

 
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ranin02
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      08-27-2007
I got past that part realizing I needed to return pointer, not
_Nodeptr, but now have a puzzling error. I am seeing the following
error

error C2664:
'CObjectPoolListAlloc<Ty,_Node>::CObjectPoolListAl loc(const
CObjectPoolListAlloc<Ty,_Node> &) throw()' : cannot convert parameter
1 from 'CObjectPoolListAlloc<Ty,_Node>' to 'const
CObjectPoolListAlloc<Ty,_Node> &'

And the error is actually being given within the STL list code here:
_List_ptr(_Alloc _Al)
: _List_nod<_Ty, _Alloc>(_Al), _Alptr(_Al)

Why on earth would it not be able to convert to a const ref? Note
that CObjectPoolListAlloc does not in fact define a copy constructor,
but defaults to the base class. This code compiled fine before the
upgrade and my attemp to implement Rebind. Please forgive me if this
is a stupid question.

 
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ranin02
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      08-27-2007
Problem is solved, seems copy constructor is now required where it was
sufficient to use base class implementation in 6.0

So nevermind!

 
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