super.new


Last week I was asked a couple of questions about called base class constructors, to which I didn't know the answers. So, I did some digging. Firstly,

Can you call super.new when there is no explicit constructor in the base class?
To which the answer is: yes. I can't think why you'd want to, though.

module M;
 
  class C;
    bit b;
  endclass
 
  class P extends C;
    bit b;
    function new;
      super.new;
    endfunction
  endclass
 
  C c = new;
 
endmodule

https://www.edaplayground.com/x/3BB9


Can you call super.super.new?
To which the answer is: no. Section 8.15 of IEEE 1800-2107 says "There is no way to reach higher (for example, super.super.count is not allowed)."

module M;
 
  class C;
    bit b;
  endclass
 
  class P extends C;
    bit b;
  endclass;
 
  class GP extends P;
    bit b;
    function new;
      super.super.new;    // this line is illegal
      super.new;
    endfunction
  endclass;
 
  initial begin
    GP gp;
    gp = new;
  end
 
endmodule

https://www.edaplayground.com/x/3TUu

A customer asked me about this. I didn't know the answer, so I wrote a few lines of code on EDA Playground. EDA Playground is great for that, because it's always on. You don't have to queue for licences, wait for EDA tools to start, create new files, fire up editors...

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