Number Cruncher skrev:
The documentation for ptr_vector::transfer( iterator before, T** from, size_type size, bool delete_from = true ) implies that the operation "delete [] from" is executed, but having examined the source, I don't think it is. This is actually the behaviour I need.
The docs could be slightly clearer, but I think they are close to optimal.
I'm trying to convert a std::vector<T*> to a boost::ptr_vector<T*>, i.e. I have a vector of pointers which is solely responsible for "owning" the objects being pointed to, and I want to create a ptr_vector which will automatically clean up the objects when it goes out of scope. I need to do the transfer so that no memory leaks in the event of an exception.
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.
Can anyone clear up/confirm that this will work: std::vector<T*> v1; v1.push_back(new T);
boost::ptr_vector<T> v2; if (!v1.empty()) { v2.transfer(v2.end(), &v1[0], v1.size(), true); } // from this point, don't care about v1 and v2 will handle deletion of T objs
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 ... 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(); <remark> It would have been possible to do v1.swap(v2.base()) if it was not for the use of void* internally. Its on my agenda to change this in the future </remark> A question: why don't you just use ptr_vector where it's needed? Is it s legacy issue? HTH -Thorsten