Re: Implementation of forward_list (and compressed_pair)

[Paolo Carlini <paolo dot carlini at oracle dot com>]

Paolo Carlini wrote:
> Ah! I think this is right! And, I must say, I'm "guilty" of having
> sidetracked Ed to the issue of having a pair of allocators stored for
> efficiency. Now I see that indeed thanks to the new variadic
> allocator::construct one can construct in place using the same node
> allocator (provided one adds an appropriate constructor for the node as
> you are doing above).
>   
To wit, this kind of patch appear to work well for std::list.

Paolo.

///////////////

Index: include/bits/stl_list.h
===================================================================
*** include/bits/stl_list.h	(revision 141104)
--- include/bits/stl_list.h	(working copy)
*************** _GLIBCXX_BEGIN_NESTED_NAMESPACE(std, _GL
*** 101,106 ****
--- 101,112 ----
      {
        ///< User's data.
        _Tp _M_data;
+ 
+ #ifdef __GXX_EXPERIMENTAL_CXX0X__
+       template<typename... _Args>
+         _List_node(_Args&&... __args)
+ 	: _List_node_base(), _M_data(std::forward<_Args>(__args)...) { }
+ #endif
      };
  
    /**
*************** _GLIBCXX_BEGIN_NESTED_NAMESPACE(std, _GL
*** 478,485 ****
  	  _Node* __p = this->_M_get_node();
  	  try
  	    {
! 	      _M_get_Tp_allocator().construct(&__p->_M_data,
! 					      std::forward<_Args>(__args)...);
  	    }
  	  catch(...)
  	    {
--- 484,491 ----
  	  _Node* __p = this->_M_get_node();
  	  try
  	    {
! 	      _M_get_Node_allocator().construct(__p,
! 						std::forward<_Args>(__args)...);
  	    }
  	  catch(...)
  	    {
*************** _GLIBCXX_BEGIN_NESTED_NAMESPACE(std, _GL
*** 1423,1429 ****
        {
          __position._M_node->unhook();
          _Node* __n = static_cast<_Node*>(__position._M_node);
!         _M_get_Tp_allocator().destroy(&__n->_M_data);
          _M_put_node(__n);
        }
  
--- 1429,1439 ----
        {
          __position._M_node->unhook();
          _Node* __n = static_cast<_Node*>(__position._M_node);
! #ifdef __GXX_EXPERIMENTAL_CXX0X__
!         _M_get_Node_allocator().destroy(__n);
! #else
! 	_M_get_Tp_allocator().destroy(&__n->_M_data);
! #endif
          _M_put_node(__n);
        }
  
Index: include/bits/list.tcc
===================================================================
*** include/bits/list.tcc	(revision 141104)
--- include/bits/list.tcc	(working copy)
*************** _GLIBCXX_BEGIN_NESTED_NAMESPACE(std, _GL
*** 75,81 ****
--- 75,85 ----
  	{
  	  _Node* __tmp = __cur;
  	  __cur = static_cast<_Node*>(__cur->_M_next);
+ #ifdef __GXX_EXPERIMENTAL_CXX0X__
+ 	  _M_get_Node_allocator().destroy(__tmp);
+ #else
  	  _M_get_Tp_allocator().destroy(&__tmp->_M_data);
+ #endif
  	  _M_put_node(__tmp);
  	}
      }