Cargo Features

[dependencies]
zeromq = { version = "0.3.5", default-features = false, features = ["tokio-runtime", "async-std-runtime", "all-transport", "tcp-transport"] }
default = all-transport, tokio-runtime

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

tokio-runtime default = tokio, tokio-util
async-std-runtime = async-std
all-transport default = ipc-transport, tcp-transport
ipc-transport tcp-transport all-transport

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.

tokio tokio-runtime
tokio-util tokio-runtime
async-std async-std-runtime?