A recent change to GNU libc changes the EAI_NODATA constant in netdb.h to only be defined when _GNU_SOURCE is defined. A google for "loudmouth EAI_NODATA" indicates that EAI_NODATA is also problematical on FreeBSD. I'm attaching a patch that protects the usage of EAI_NODATA with an ifdef ... I think this is preferable to the sledgehammer of _GNU_SOURCE; while GNU libc can apparently still return this error value, using the default message in this rare corner case should not be a problem.