NULL pointer dereference error in OVM

Spent long time cracking your head how to get rid of this error?


The first thing to notice when we see "pointer" is that this is related to memory allocation. There are two conditions on which we get this error.

• When memory is not yet available for this particular object (the name of the object will be available in the error description).
• Memory is available (object already created), but the handle which we declared may not have a connection(reference) to it.

OVM is highly typed becasue of OOP. It creates a chain of objects in OVM object hierarchy and the configuration mechanism gives the links to them all. If we want to use out of reference object's handle, we need to refer the object first.  This is done by configuration, which is generally done inside build() task, but can be done also in initial blocks inside module/program block.

Use the following code initially once:
      set_config_object("*","object_name", object_name_handle, .clone(0));

Use the following check whenever you want to use this object out side the scope:
    object_class_name object_name_handle;
    ovm_object              ovm_object_handle;
    if (!this.get_config_object("object_name_handle",ovm_object_handle,.clone(0)))
    begin
        `ovm_info(report_id,"object_name_handle is not instantiated",OVM_MEDIUM);
        return;
    end
    if (!$cast(object_name_handle, ovm_object_handle))
    begin
        `ovm_error(report_id, "object_name_handle cast failed");
    end