Cargo Features

[dependencies]
libcdio-sys = { version = "0.5.1", default-features = false, features = ["cdio", "iso9660", "udf"] }
default = cdio, iso9660, udf

These default features are set whenever libcdio-sys is added without default-features = false somewhere in the dependency tree.

cdio default
iso9660 default
udf default

libcdio-sys has 4 features without comments.