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cloning question

mwhite

I am trying to utilize "clone" so that the cloned data retain the value even after the original data gets updated.  So far it does not work as I expected.

forever begin
  @(posedge clk);
    if (getItemRdy) begin
      myitem_expected.get(myitem_item);
      myitem_expected_cloned.put(myitem_item);
    end
  end

myitem_expected and myitem_expected_cloned are analysis_fifo.
myitem_expected will receive new items asynchronous to this process above.  With this code, my understanding is that myitem_expected_cloned data will change when myitem_expected data changes because the fifos are holding handles.  And that is not what I want.  I want myitem_expected_cloned to change only when getItemRdy is asserted.

forever begin
  @(posedge clk);
    if (getItemRdy) begin
      myitem_expected.get(myitem_item);
      $cast(cloned_item, myitem_item.clone());     
      myitem_expected_cloned.put(cloned_item);
    end
  end

So, I added "$cast" code as above.  I thought myitem_expected_cloned will be updated only when this clone copy gets executed.  But I see new value in myitem_expected_cloned before executing $cast for the 2nd time.

Could anyone help me?  Thank you!

  • Based on your examples, I think you may be confused about what the clone() function does. It returns a handle to a new class instance that's a clone of the original. You need to store the cloned class into your long-term storage:

    myitem_expected_cloned.put(cloned_item);

     

  • Sorry, I had a typo, I was storing the cloned_item instance in my original code.

    It turns out that do_copy method of the sequence_item class had a problem.  The sequence_item class has data members of another class.

    Inside do_copy method:

    instance_of_another_class = rhs.instance_of_another_class;  // This does not work

    instance_of_another_class.data_member = rhs.instance_of_another_class.data_member;  // This works

     

    But this class has to know all the data members below this class member.  This seems to go against OOP way.  It is not clear to me how to implement deep copy of class objects.  I was not able to find any example.

    Thanks.

     

     

     

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