passing "this" as an argument to a function

[phil]

Hi:

is there a way to pass "this" (or other means that represent the calling object handle) as an argument to a function, in SystemVerilog?

Here is this unexpected situation:

There is a function: func(class1 obj1, class2 obj2);

inside class1, there is a function foo(), calling func().

Class1::foo();

void' func(this, obj2);

endfunction

But surprisingly to me, it is illegal, because "this" is not a variable, as told by the compiler.

So is there a way to pass the handle of the calling object as an argument to a function? if not, is there a work around?

Thanks

phil

[dave_59]

Can you show the complete definition of foo? Where is the 'function' keyword. Is it a static method? You can only use 'this' inside a non-static method of a class.

If it is not static, can you show the actual error message you are seeing?

[phil]

interesting. it is an error only when func() uses "ref" of obj1.

below is the complete code. please note that function pa() uses "ref A".

Without "ref", the code works. With "ref", the error message is:

pa(this): invalid ref argument usage because actual argument is not a variable. [systemVerilog].

Why "this" can't be used as an argument of a object reference?

package my_pkg;

class A;

parameter bit base_a = 1;

endclass // A

function automatic void pa(ref A tr);

$display("pkg tr.base_a %h", tr.base_a);

endfunction // pa

endpackage // my_pkg

`include "my_pkg.svh"

import my_pkg::*;

class sub_a extends A;

function new(string name="sub_a");

pa(this);

endfunction // new

endclass // aub_a

module try;

sub_a sa;

initial begin

sa = new;

end

endmodule

[dave_59]

First, there is no need to declare tr as a ref argument. tr is already a class variable that references a class object. Use 'input A tr' or simply 'A tr' instead.

What you put as the actual argument to a ref, output, or inout argument must all be "writable". 'this' is not a variable and cannot be written to. The keyword 'this' is a special reference to the object used to invoke the method that 'this' is used from within.

See this link about when you should use ref arguments: https://forum.verificationacademy.com/forum/verification-methodology-discussion-forum/systemverilog-and-other-languages-forum/29572-passing-arguments-reference#comment-29573

[phil]

Hi Daave:

Thanks for the explanation. It makes sense now.

--Phil