Undefined reference errors in gcc

gcc link results with e开发者_如何学Crrors:

dns.cpp: undefined reference to '__res_querydomain'
dns.cpp: undefined reference to '__dn_skipname'    
dns.cpp: undefined reference to '__dn_expand'
dns.cpp: undefined reference to '__res_query'

Is there another library that I need to link to?

Adding -lresolv solved this for me.