Config used inside Constraint block gets an error

UVM
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1

Hi,

I am writing a constraint, inside which I am using config variable (there are variables inside my config class), but there is runtime error that

Error-[CNST-NPE] Constraint null pointer error
Accessing null pointer config in constraint.
Please make sure config is allocated.

I want to understand that which UVM phase does constraint solver activity. (I am supposing it’s run phase & config class variable must be built in Build Phase)

If I am able to use config class variable inside task body of sequence, why I am not able to use it inside constraint block of sequence ?

It’s not compile time error, it’s run time error for me.

Please help with understanding and proper solution.

Regards,
Kavish

2

In reply to shahkavish77:

The constraint solver is governed by a call to randomize(), which is not tied to any phase. And a null reference can only be checked at run time.

You need to make sure you retrieve a handle to your config object before the call to randomize().

3

In reply to dave_59:


typedef class a_adma_col1;
typde_f class a_adma_col2;

class A_test uvm_test;
...
...
a_dma_col1 col1;
a_dma_col2 col2;

...
...
function void build (uvm_phase phase );
  super.build_phase(phase);
     col1 =  a_dma_col1::type_id::create("a_dma_col1");
     col1 =  a_dma_col1::type_id::create("a_dma_col1");
endfunction 


task run_phase (uvm_phase phase);
   phase.raise_objections (this, "", 1 );
   super.run_phase(phase);

      col1.start(env.vsqr);
     col2.start(env.vsqr);

phase.drop_objection(this, "", 1);
endtask

..
endclass

class a_dma_col1 extenda a_dma;
...
...
`uvm_declare_p_sequencer(`A_SEQUENCER);

constraint c1 {col > 2}
...
...
...

task body ();
    if (!this.randomize() begin 
           `uvm_fatal ("FATAL");
end
endtask 
endclass

class a_dma_col2 extenda a_dma;
...
...
`uvm_declare_p_sequencer(`A_SEQUENCER);

...
...
...
constraint c1 {col1 > 3};

task body ();
    if (!this.randomize() begin 
           `uvm_fatal ("FATAL");
end_
endtask 
endclass

Hi Dave,

Here is my pseudo code above looks like the body when i call start method of the sequence from the test i don’t see a_dma sequence body getting executed
any pointer on what could be the issue ?