Idiomatic use of auto_ptr to transfer ownership to a container
- by heycam
I'm refreshing my C++ knowledge after not having used it in anger for a number of years. In writing some code to implement some data structure for practice, I wanted to make sure that my code was exception safe. So I've tried to use std::auto_ptrs in what I think is an appropriate way. Simplifying somewhat, this is what I have:
class Tree
{
public:
~Tree() { /* delete all Node*s in the tree */ }
void insert(const string& to_insert);
...
private:
struct Node {
...
vector<Node*> m_children;
};
Node* m_root;
};
template<T>
void push_back(vector<T*>& v, auto_ptr<T> x)
{
v.push_back(x.get());
x.release();
}
void Tree::insert(const string& to_insert)
{
Node* n = ...; // find where to insert the new node
...
push_back(n->m_children, auto_ptr<Node>(new Node(to_insert));
...
}
So I'm wrapping the function that would put the pointer into the container, vector::push_back, and relying on the by-value auto_ptr argument to
ensure that the Node* is deleted if the vector resize fails.
Is this an idiomatic use of auto_ptr to save a bit of boilerplate in my
Tree::insert? Any improvements you can suggest? Otherwise I'd have to have
something like:
Node* n = ...; // find where to insert the new node
auto_ptr<Node> new_node(new Node(to_insert));
n->m_children.push_back(new_node.get());
new_node.release();
which kind of clutters up what would have been a single line of code if I wasn't
worrying about exception safety and a memory leak.
(Actually I was wondering if I could post my whole code sample (about 300 lines) and ask people to critique it for idiomatic C++ usage in general, but I'm not sure whether that kind of question is appropriate on stackoverflow.)
