Re: [libstdc++] Problems with deques (patch included)

[Peter Schmid <schmid at snake dot iap dot physik dot tu-darmstadt dot de>]

|This unncessarily breaks ABI.  It is better to reorder the
|base-initialiser-list insteads of the data member declaration.


I deliberately reordered the data member declarations in such a way
to remove an abi breaking change with respect to the deque class
that is shipped with gcc 3.1. I believe abi changes with respect to
different libstdc++ version should be minimized, therefore I suggested
the patch.

The template <class _Tp, class _Alloc, bool __is_static>
class _Deque_alloc_base class from libstdc++ 3.1 has the layout:
(cf. lines 240ff from stl_deque.h)

  allocator_type      _M_node_allocator;
  _Map_allocator_type _M_map_allocator;

  _Tp* _M_allocate_node() {
    return _M_node_allocator.allocate(__deque_buf_size(sizeof(_Tp)));
  }
  void _M_deallocate_node(_Tp* __p) {
    _M_node_allocator.deallocate(__p, __deque_buf_size(sizeof(_Tp)));
  }
  _Tp** _M_allocate_map(size_t __n)
    { return _M_map_allocator.allocate(__n); }
  void _M_deallocate_map(_Tp** __p, size_t __n)
    { _M_map_allocator.deallocate(__p, __n); }

  _Tp** _M_map;
  size_t _M_map_size;


in contrast to the 3.2 version (lines 385ff from stl_deque.h)

      _Tp**                _M_map;
     size_t               _M_map_size;
     allocator_type       _M_node_allocator;
     _Map_allocator_type  _M_map_allocator;

The code for the _Deque_alloc_base constructor is the same, though.

Hope this helps,

Peter Schmid