receiving null pointer error when accessing config object from uvm_do_with

[assafgedalia]

Hi,

 

i have an agent (uvm_agent) which has a config object (uvm_object) which holds the agent's configurations.

i am setting this config from the environment and getting it inside the agent.

in the agent i am setting this config for everyone to see (*).

 

i have a sequence for this object that get's this config object.

everything works ok so far and i am able to access all the configurations from the config object inside the sequence.

the problem starts when i try to create constrained transactions (`uvm_do_with) with the constraints taken from this config object.

then i get a null pointer error.

 

the error:

 

Error-[CNST-NPE] Constraint null pointer error

/space/users/assafg/nu4000/verification/iae/ciif_agent/ciif_sequence.sv, 194

  Accessing null pointer cfg.frame_width in constraints.

  Please make sure variable cfg.frame_width is allocated.

 

so i can access a certain field from the sequence but when i try to set it as a constraint i get an error.

 

some code from the sequence (this is only part of the code):

 

    virtual task pre_start();

        // Get the configuration

        if (!uvm_config_db #(ciif_cfg)::get(get_sequencer(), "", "cfg", cfg)) begin

            `uvm_fatal("CFGERR", "%m cfg not set")

        end

    endtask: pre_start

 

 

    virtual task body();

        `uvm_info("DEBUG_DEBUG", $sformatf("cfg.frame_width = %0d\n", cfg.frame_width), UVM_NONE);                 // print occurs and proves that i can access this field

       

        `uvm_do_with(req, {

                                            fwidth  == cfg.frame_width;             // error here

                                       }

                               );

    endtask: body

 

 

any idea would be much appreciated.

 

Thanks,

Assaf

 

 

 

 

[apfitch]

One possible problem is that there is a member in instance req which is also called cfg.

If that's the case, then using local:: should help

`uvm_do_with(req, { fwidth  == local::cfg.frame_width;   } );

Another possibility is that the cfg object is being cloned for some reason and you haven't implemented do_copy() correctly. In that case you'd just have to implement do_copy in the config object.

 

regards

Alan

[assafgedalia]

Alan you are the man!

 

there was a rogue cfg in the transaction i created,

and now i understand that the scope of the constraint is the scope of the new transaction

and in the scope of the newly created transaction the cfg has not been declared yet.

 

many thanks,

Assaf