Wireshark · Ethereal-dev: [Ethereal-dev] Simple C datatype query

["bunty " <bunty123_4@xxxxxxxxxxxxxx>]

hello,
      I have added new protocol to ethereal but it gives pointer warning as i dont know how to use unsigned characters in hf_register_info.
          Following is my one field description for unsigned char string in header of protocol. for that
static hf_register_info hf[] = {
                { &hf_myip_text, { "myip_text","myip.text", FT_STRING, BASE_HEX, NULL, 0x0,"", HFILL }},

for that i first added
static unsigned char* hf_myip_text = "NULL";
    but i got assertion error in ./ethereal execution.
what should i assgning then for string field of protocol?

regards.
bunty.