If this is an application written or ported by you, it means that the code has explicitly declared at least one of these (errno, h_errno, or _res), probably using an extern statement. Direct access to these library variables has been deprecated because they do not work properly in a multithreaded context.
This can be dealt with. The 'errno' should be accessed via "#include <errno.h>". The functions to do with h_errno and _res are obsolete; 'getaddrinfo' and 'getnameinfo' should be used instead.