[SOLVED] System verilog extended class and constrained random question

[vlsiexpert]

Need help on a simple system verilog code

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1. class packet has dynamic array data[] and it's size is constrained between 1 to 250
2. Extending the packet class to small_packet and constraining size to be less than 10
3. casting small_packet to packet class's object

I would expect the size should be always less than 10, but it is not obeying the constraint in extended class

Any help?code link

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// Code your testbench here
// or browse Examples
class packet;
  rand byte data[];
  rand bit [7:0] length;
  
  constraint payload_size_c { data.size inside { [1 : 250]};}
  
endclass
 
class gen;
  rand packet pkt;
  function exec();
  pkt = new();
  if ( !pkt.randomize()) $fatal("Gen: trans randomization failed");
  endfunction: exec
endclass
 
class small_packet extends packet;
 
  constraint small_c { data.size < 10 ; }
endclass
program test;
  small_packet spkt;
  gen sgen;
  
  initial begin
   spkt = new();
    sgen = new();
    sgen.pkt = spkt;
    sgen.exec();
        
    $display("Size = %d, length = %d",sgen.pkt.data.size,sgen.pkt.length);
    
  end
endprogram

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[dave_59]

Your function exec constructs a new pkt, replacing the small_packet spkt you set before calling exec.

 

[vlsiexpert]

Your function exec constructs a new pkt, replacing the small_packet spkt you set before calling exec.

thanks dave, i commented line #14 it works