Here's a short snippet which showcases two memory leaks :

public class Holder : Object {

  Value? val;

  public Holder(Value? val) {
    this.val = val;
  }

  //In the absence of this explicit destructor
  //the value doesn't get unset, and leads to memory being leaked
  ~Holder() {
    if(val != null) {
      val.unset();
    }
  }
  
}

public class Test : Object {
  
  public static void main(string[] args) {

    Holder val;
    while(true) {
      StringBuilder sb = new StringBuilder();
      sb.append_unichar(' ');
      //In the absence of this temporary variable the GValue doesn't get freed,
      // and leads to a memory leak
      //eg : val = new Holder(sb.str); would leak.
      GLib.Value gval = sb.str;
      val = new Holder(gval);
    }
  }
}