Static variable in parametric class

SystemVerilog
,
1

class A #(int a = 10);
static int b = a;
static int c ;
endclass
module main;
A #(30) a1;
A #(50) a2;
initial begin
a1 = new();
a2 = new();
$display (“a1.b =%0d,\t a2.b=%0d,\t a1.c= %0d,\t a2.c = %0d”,a1.b,a2.b,a1.c,a2.c);
a1.b = 111;
a1.c = 121;
$display (“a1.b =%0d,\t a2.b=%0d,\t a1.c= %0d,\t a2.c = %0d”,a1.b,a2.b,a1.c,a2.c);
end
endmodule

the value of b and c are different in both the objects, even they are defined as static?

2 
class A #(int a = 10);
static int b = a;
static int c ;
endclass
module main;
A #(30) a1;
A #(50) a2;
initial begin
a1 = new();
a2 = new();
if(!$cast(a1,a2))
  $display("Error");
$display ("a1.b =%0d,\t a2.b=%0d,\t a1.c= %0d,\t a2.c = %0d",a1.b,a2.b,a1.c,a2.c);
a1.b = 111;
a1.c = 121;
$display ("a1.b =%0d,\t a2.b=%0d,\t a1.c= %0d,\t a2.c = %0d",a1.b,a2.b,a1.c,a2.c);
end
endmodule

Output:

Error

a1.b =30, a2.b=50, a1.c= 0, a2.c = 0

a1.b =111, a2.b=50, a1.c= 121, a2.c = 0

It means assignment to object of class A #( 30) from object of class A #( 50) is illegal which says both are different classes. And Static works for objects of single(same) class.

Thanks,
Rajashekhar.

3

In reply to kothaluri rajashekhar:

since parameters are different values, it means classes are of different type.is it ??

4

In reply to VPS:

Yes,

If we have

A #(30) a1;
A #(30) a2;            //A #(50) a2;

Then both classes are treated as one and the static keyword works.

Thanks,
Rajashekhar.

5

If you want parametrized classes with different specializations to share common static variables, they the class should be extended from a common unparametrized base class. See my DVCon paper Using Parameterized Classes and Factories: The Yin and Yang of Object-Oriented Verification which has a good explanation of how static variables work with classes.