GLib-2.0 ▶ GLib ▶ hostname_is_non_asciiSince 2.22

Tests if hostname contains Unicode characters. If this returns true, you need to encode the hostname with g_hostname_to_ascii() before using it in non-IDN-aware contexts.

Note that a hostname might contain a mix of encoded and unencoded segments, and so it is possible for g_hostname_is_non_ascii() and g_hostname_is_ascii_encoded() to both return true for a name.