swadhin ,
what u have explained i know it already.
the problem is calling method m4 of subclass from super class instance (object) after narrow casting which is only defined in subclass not super class.
i should have commented that statement
create object o_super in my code while posting que . my mistake. 
but what i wanna know is:
i want to call m4 method of sub class using super class instance.
see this...
" below statement throw a syntax error becoz its not possible to access those
*method which are not defined in super class
*call method o_super->m4. "throws syntax error.
but when i change this to m4 in brackets:
call method o_super->('m4'). "works fine WHY!!!!!! (atleast no syntax error)
but the prog dumps.
another thing if i want to make prog not to dump how to change it into dynamic type from static type.
how to do that.
i hope u now understand what i want to know.