Since glibc 2.14:
_GNU_SOURCE
.TP 4
-.\" FIXME See http://sources.redhat.com/bugzilla/show_bug.cgi?id=4749
+.\" See http://sources.redhat.com/bugzilla/show_bug.cgi?id=4749
Before glibc 2.14:
_BSD_SOURCE || _SVID_SOURCE
/* _GNU_SOURCE also suffices */