On 25/06/14 21:56 +0100, Jonathan Wakely wrote:
The other adds an RAII type to help manage pointers obtained from
allocators. The new type means I can remove several ugly try-catch
blocks that are all very similar in structure and have been bothering
me for some time. The new type also makes it trivial to support
allocators with fancy pointers, fixing long-standing (but not very
important) bugs in std::promise and std::shared_ptr.
This patch applies the __allocated_ptr type to hashtable_policy.h to
remove most explicit deallocation (yay!) The buckets are still
allocated and deallocated manually, because __allocated_ptr only works
for allocations of single objects, not arrays.
As well as __allocated_ptr this change relies on two things:
1) the node type has a trivial destructor, so we don't actually need
to call it, we can just reuse or release its storage.
(See 3.8 [basic.life] p1)
2) allocator_traits::construct and allocator_traits::destroy can be
used with an allocator that has a different value_type, so we don't
need to create a rebound copy to destroy every element, we can just
use the node-allocator.
(See http://cplusplus.github.io/LWG/lwg-active.html#2218 which is
Open, but I've discussed the issue with Howard, Pablo and others,
and I think libc++ already relies on this assumption).
François, could you check it, and let me know if you see anything
wrong or have any comments?