获取：空对象访问

Question

我收到此错误，以下错误，据我所知，根据此错误消息，我将访问一个空对象。

Error-[NOA] Null object access
generator.sv, 23
  The object at dereference depth 1 is being used before it was 
  constructed/allocated.
  Please make sure that the object is allocated before using it. 

class generator;
  
  transaction trans;
  
  mailbox gen2driv;
  
 // event ended;
  
  function new(mailbox gen2driv);
    this.gen2driv = gen2driv;
  endfunction
  
  task main();
    repeat(4) begin
    trans = new();
      trans.randomize();
      if(!trans.randomize()) $display("generator ransomize failed");
    
     trans.display("[generator]");
   
    gen2driv.put(trans);
   
  //  -> ended;
    end
  endtask 
  
endclass

代码链接

Answer 1

您正在向生成器的构造函数传递一个来自环境的空对象：

class environment;
  
 // transaction trans;
  generator gen;
  driver driv;
  monitor mon;
  scoreboard scb;
  
  mailbox gen2driv;
  mailbox mon2scb;
  
  virtual intf vif;
  
  function new(virtual intf vif);
    this.vif = vif;
    
    gen = new(gen2driv);
    driv = new(vif,gen2driv);
    mon = new(vif,mon2scb);
    scb = new(mon2scb);
    
  endfunction

^^^ 来自您的代码：https://www.edaplayground.com/x/Qv9e