Question

Let’s say I have a class which will be used to create either tree or list structure. Let’s call it

template <typename K, typename V>
class Node{
  // some data
  Node<K,V>* next;
  Node() {
    next = static_cast<Node<K,V>*>( malloc( sizeof(Node<K,V>) ));
  }
};

By doing this I get a following compiler error:

there are no arguments to ‘malloc’ that depend on a template
parameter, so a declaration of ‘malloc’ must be available (if you use
‘-fpermissive’, G++ will accept your code, but allowing the use of an
undeclared name is deprecated)

Is there any way to use malloc in such a way without having to use deprecated code? I want to use malloc instead of new because I’d like to do some more advanced memory management up there.

Answer 1

The compiler error is telling you that it does not have a declaration of what malloc is. You are missing the include that declares that function.

Other than that, the approach is broken. You are writing a generic tree, but because of the use of malloc you are limiting the use to POD types (I am assuming that K and V are stored in the Node). You should use new instead that will call the constructor for the type, not just allocate memory.