Solution
--------

	 In this assignment we would understand the call graph (cgraph_node and cgraph_edge) structure in GCC. 

	 1. The code to print the callers is explained below.

	       /* Check if the node i.e. a function has callers */
               if(node->callers)
                {
			/* Print the first caller */
                        fprintf (dump_file,"%s",cgraph_node_name(node->callers->caller));

			/* Extract the next caller */
                        edge = node->callers->next_caller;
			
			/* Iterate over all the remaining callers */
                        while(edge)
                        {
                                fprintf (dump_file,"%s",cgraph_node_name(edge->caller));
                                edge = edge->next_caller;
                        }
                }

	 2. Code to identify the `main' function is explained below.

                if (MAIN_NAME_P(DECL_NAME (node->decl)))
                {
			/* Main function is found */
   		}