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Subject: NULL pointer dereference
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jaally
Posts: 32
Online: User is Offline
3/27/2008 11:17 PM  
Hello Friends,

     I'm building a class based SV UVC using URM methodology. As usual, I've master agent & slave agent with independent monitors in it.
   Now, in my master bfm I've used build operation and casted a new unit(say "X") inside it which is needed for my protocol. So, i've binded my monitor to this unit also as shown below:

class master_bfm extends urm_bfm;
   master_monitor mon_ref;
  
  `urm_unit_utils_begin(master_bfm)
       `urm_field_object(mon_ref, REFERENCE + PRINT)
  `urm_unit_utils_end


  function new(input string name, input urm_unit parent);
       super.new(name,parent);
  endfunction: new

  virtual function build();
     super.build();
     $cast(X, create_unit("X_unit", X));
     X.build();

     X.mon = mon_ref; // Here I'm binding the monitor in X_unit to the monitor in master_bfm
  endfunction: build

 ........my code..................

endclass: master_bfm
 


If you observe the code, I've created a "mon" reference in the X_unit with same master_monitor unit.
 And I tried accessing the variables of monitor like "reset_asserted" in X_unit. It gives "NULL pointer dereference" during the "ncsim" run. I tried all ways of connecting it properly through references but could not succeed. In fact, I could access those monitor variables inside the master_bfm but not in X_unit.

Can anyone lemme know the solution of it or where I went wrong?

Thanks in advance,
Jalli
prasad_vc
Posts: 12
Online: User is Offline
3/27/2008 11:28 PM  
Jalli,

Try doing new() of mon_ref in your bfm code. This should solve your problem.

function new(input string name, input urm_unit parent);
super.new(name,parent);
mon_ref = new;
endfunction: new

-Vivek
-Vivek C. Prasad
jaally
Posts: 32
Online: User is Offline
3/27/2008 11:53 PM  
Vivek,

Your suggestion didn't help! :(


CORRECTION in my above code
`urm_unit_utils_begin(master_bfm)
`urm_field_object(X, REFERENCE + PRINT) // This was missing in my above code
`urm_field_object(mon_ref, REFERENCE + PRINT)
`urm_unit_utils_end

Regards,
Jalli
arjuny
Posts: 7
Online: User is Offline
3/28/2008 12:03 AM  
Hi Vivek,

Continuing your post,
If "new" is used an object of monitor will be created in bfm.(as per methodology the monitor will not have object created in the bfm, monitor reference should be there in bfm).

-Arjun.
prasad_vc
Posts: 12
Online: User is Offline
3/28/2008 12:33 AM  
Arjun,

What you say is correct, i haven't used any methodologies with SV, however i knew one thing that you get an "Null pointer Deference" when a "new" of your object or variable is not done.

I don't knew exactly where it will be done, as per the uRM.

-Vivek.
-Vivek C. Prasad
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Forums > Functional Verification > SystemVerilog > NULL pointer dereference


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