Notice that it is a really bad idea to use an empty enum as FFI type. The compiler relies on empty enums being uninhabited, so handling values of type &Empty is a huge footgun and can lead to buggy program behavior (by triggering undefined behavior).
pcap_t
andpcap_dumper_t
seem to be represented by empty enums on the Rust side. According to the Rustonomicon this is a bad idea.From https://doc.rust-lang.org/nomicon/ffi.html#representing-opaque-structs: