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cargo nono - Detect (possible) no_std compatibility of your crate and dependencies


From embedded programming, over smart contracts in Rust, to general cross-platform portable crates, #![no_std] crates are becoming more and more widespread. However it is currently a very cumbersome process to find out if and why (not) a crate is compatible with no_std usage, and often requires a lengthy trial and error process, and digging through the source of all your dependencies.

cargo nono tries to aid you in navigating the current minefield that is no_std usage, and it's biggest "no no"s.


Prebuilt binaries

cargo-nono also comes as prebuilt binaries (useful for CI):

curl -LSfs | \
    sh -s -- --git hobofan/cargo-nono


cargo install cargo-nono
# For warnings with more informative messages install like this
RUSTFLAGS="--cfg procmacro2_semver_exempt" cargo install cargo-nono




Run in the crate directory you want to check:

cargo nono check

The cargo nono check subcommand also understands the --no-default-features and --features <FEATURES> flags to help in conditional no_std setups.


  • Tries to infer no_std compatibility in dependencies by looking for a #![no_std] attribute or the often used conditional #![cfg_attr(not(feature = "std"), no_std)]
  • Helps in pinpointing which dependencies and feature flags activate std feature flags
  • Warn of use std:: statements in code

Planned features

  • Warn of [build-dependencies] features bleeding over: cargo#5730


Licensed under either of

at your option.