Cargo Features

rand_core has no features set by default.

rand_core = { version = "0.6.4", features = ["std", "alloc", "serde1"] }
std = alloc, getrandom

use std library; should be default but for above bug

Enables std of getrandom

alloc std?

enables Vec and Box support without std

serde1 = serde

enables serde for BlockRng wrapper

Features from optional dependencies

In crates that don't use the dep: syntax, optional dependencies automatically become Cargo features.

serde serde1?

With derive and default (std)

getrandom std?

Affects rand_core::SeedableRng.from_entropy