On 28/07/10 16:36, Thorsten Ottosen wrote:
As far as I can see, this is exactly what ptr_vector::scoped_deleter is doing: it will delete any of the copied pointers, but it never actually deletes the "from" pointer; presumably because you don't know whether operator new[] was used when allocating it.
Actually it does call delete[] in any case as the destructor of scoped_deleter will call the destructor of the stored scoped_array member. scoped_deleter::release() only means that the T* objects are not deleted, but the internal array always is.
Thanks; I missed the scoped_array member storage.
Well, a vector<T*> cannot guarantee that the internal buffer is allocated with new T[], I would say its almost guaranteed that it is not. IOW, the function is meant for C-arrays allocated with new T[], not vectors. So no, it won't work. replacing true with false makes it work, but ...
Yes; I never wanted the ptr_vector to try and clear up the std::vector's internal array or pointers - just the pointees.
You can still get a leak if insertion fails, but how is that any worse than what your current code can do? Otherwise, use scoped_deleter manually as so:
v2.scoped_deleter sd( v2, v1.size() ); std::copy( v1.begin(), v1.end(), sd.begin() ); v2.transfer( v2.end(), sd.begin(), v1.size(), false ); sd.release();
I can see how that might work...
A question: why don't you just use ptr_vector where it's needed? Is it s legacy issue?
It all started when I needed to return a list of (shallow, non-owning) observer pointers from a class. Sometimes that class would create and own the pointees itself and sometimes it would just be another indirection to an external source. I see that I can use view_clone_allocator to remove ownership semantics, but I can't return "const ptr_vector<T, heap_clone_allocator> &" one moment and const ptr_vector<T, view_clone_allocator> &" the next. I ended up storing a (possibly empty) ptr_vector in the class, and returning "const std::vector<T *> &" with shallow pointer copies of the ptr_vector contents if owned, and the indirected pointers otherwise. If there were no legacy issues at all, I'd probably just return a std::vector<shared_ptr>. Regards, Simon.