Instance of class

SystemVerilog
1

In below code, I am not sure why it is not necessary to create an instance of f in line 10.



class foo;
  function void build();
    $display(" i am build");
  endfunction
endclass

class cmd;
   foo f;
   function void setF(foo f);
      this.f = f;
   endfunction
   function void run();
      f.build();
   endfunction
endclass

module top;
   cmd d;
   foo f ;             --> line 10.  Do we need  f = new() ? 
   initial begin
     d = new();
     d.setF(f);
     d.run();
   end
endmodule
2

In reply to VE:
Have you tried it?

What to you expect f.build() to do?

3

In reply to dave_59:

In reply to VE:
Have you tried it?
What to you expect f.build() to do?

Thanks Dave.
" Have you tried it ?"
– Yes, i did run 3 simulators. i got the message “i am build” from the function f.build() without creating an object of foo ( f = new()) from all 3.

" What to you expect f.build() to do "
– My code is just a small test case to demo my question, basically i want to use the command pattern in my TB. It seems to me there is unnecessary to have f = new(); i am not sure it is related to C++ style? “static” ? or …?
Thanks

4

In reply to VE:

See Why is my code not failing when accessing non static method from not static class? | Verification Academy

5

In reply to dave_59:

From that thread, the 2017 LRM quote at play here is section 8.4:

Accessing non-static members (see 8.9) or virtual methods (see 8.20) via a null object handle is illegal. The result of an illegal access via a null object is indeterminate, and implementations may issue an error.

I might guess the second part is in there for performance reasons, as the simulator doesn’t want to constantly perform a null-check every time a non-static member is accessed?