Passing struct as an argument

Hi,
I am trying my hand on DPI, and have an example in which i want to pass a struct as an argument to 'C'. however i am not getting any results.

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The code is:

// Program to pass struct data-type as an argument.
// Author: Vivek C. Prasad
// Date  : 20 september 2006

#include
#include "svdpi.h"

  typedef struct {
    char a;
    int b;
    } AB;

  AB sc;
  int str(const AB sc) {
       printf("the byte is: %c\n",sc.a);
       printf("the int is: %d\n",sc.b);
       return(-1);
       }

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// Program to pass struct data-type as an argument.
// Author: Vivek C. Prasad
// Date  : 20 september 2006

module structPass();
 
  int res;
  typedef struct packed {
    byte a;
    shortint b;
    } AB;

  AB dt_struct;
 
  import "DPI-C" context str = function int structFunction(input dt_struct);

  initial begin
    dt_struct.a = "V";
    dt_struct.b = 10;
    res = structFunction(dt_struct);
    $display("The struct is passed as an argument.\n");
    $display("Byte: %0d\n",dt_struct.a);
    $display("Int : %0d\n",dt_struct.b);
    $display("Return : %0d\n",res);
  end
endmodule

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The Result is:

the byte is:
the int is: 0
The struct is passed as an argument.

Byte: 86

Int : 10

Return : -1

**********************************

Vivek.