Cargo Features

[dependencies]
libc = { version = "0.2.169", default-features = false, features = ["std", "rustc-dep-of-std", "extra_traits", "const-extern-fn", "align", "use_std"] }
default = std

The std feature is set by default whenever libc is added without default-features = false somewhere in the dependency tree.

std default use_std?
rustc-dep-of-std = align, rustc-std-workspace-core
extra_traits
const-extern-fn

const-extern-function is deprecated and no longer does anything

align rustc-dep-of-std?

align is deprecated and no longer does anything

use_std = std

use_std is deprecated, use std instead

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.

rustc-std-workspace-core rustc-dep-of-std?