Cargo Features

duk-sys has no features set by default.

[dependencies]
duk-sys = { version = "0.3.0", features = ["debug", "trace", "spam"] }
debug = log
trace = log
spam = log

Features from optional dependencies

In crates that don't use the dep: syntax, optional dependencies automatically become Cargo features. These features may have been created by mistake, and this functionality may be removed in the future.

log debug? spam? trace?