duplicate lang item in crate `std` (which `my_crate` depends on): `panic_impl`

Question

I have this hierarchy in my substrate parachain project:

my_parachain/
├── ...
├── runtime folder
└── runtime-common folder
Cargo.lock
Cargo.toml

The above runtime-common has some constants and types that are used in my pallet-bridge's mock.rs and tests.rs, and also in my runtime/src/lib.rs

inside the runtime-common folder:

src/
└── lib.rs
Cargo.toml

inside the runtime-common/src/lib.rs:

pub mod constants {
  //use node_primitives::Balance;
  pub type Balance = u128;//from substrate/bin/node/primitives
  pub const MICRO_CFG: Balance = 1_000_000_000_000; // 10−6     0.000001
  pub const MILLI_CFG: Balance = 1_000 * MICRO_CFG; // 10−3     0.001
  pub const CENTI_CFG: Balance = 10 * MILLI_CFG; // 10−2    0.01
  pub const CFG: Balance = 100 * CENTI_CFG;

  pub const NATIVE_TOKEN_TRANSFER_FEE: Balance = 2000 * CFG;

  pub const NFT_TOKEN_TRANSFER_FEE: Balance = 20 * CFG;
}

inside the runtime-common/Cargo.toml

[package]
name = "runtime-common"
version = "1.0.0"
authors = ["Centrifuge"]
edition = "2021"
license = "LGPL-3.0"
homepage = ""
repository = ""

[dependencies]

[features]
default = ["std"]
std = [
]
runtime-benchmarks = [
]

I can add my bridge-pallet, chainbridge, and runtime-common in runtime/Cargo.toml as dependencies:

pallet-bridge =           { path = "../pallets/bridge", default-features = false }
chainbridge = { git = "https://github.com/centrifuge/chainbridge-substrate.git", default-features = false, branch = "polkadot-v0.9.23" }
runtime-common = { path = "../runtime-common", default-features = false }

then cargo check and cargo build can run fine.

But after adding these code inside the runtime/src/lib.rs:

pub use runtime_common::{
  constants::{
    CFG, NATIVE_TOKEN_TRANSFER_FEE, NFT_TOKEN_TRANSFER_FEE, Balance,
  }
};

then I got these errors:

   Compiling h-runtime v0.0.1 (/mnt/sda3/polkadot/1pchain-chainbridge/runtime)
error: failed to run custom build command for `h-runtime v0.0.1 (/mnt/sda3/polkadot/1pchain-chainbridge/runtime)`

Caused by:
  process didn't exit successfully: `/mnt/sda3/polkadot/1pchain-chainbridge/target/debug/build/h-runtime-1e48817ae1228872/build-script-build` (exit status: 1)
  --- stdout
  Information that should be included in a bug report.
  Executing build command: "rustup" "run" "nightly" "cargo" "rustc" "--target=wasm32-unknown-unknown" "--manifest-path=/mnt/sda3/polkadot/1pchain-chainbridge/target/debug/wbuild/h-runtime/Cargo.toml" "--color=always" "--profile" "release"
  Using rustc version: rustc 1.63.0-nightly (dc80ca78b 2022-06-21)


  --- stderr
  warning: Patch `fc-db v2.0.0-dev (https://github.com/PNetwork/frontier?branch=patch-polkadot-v0.9.23#d7b30f9c)` was not used in the crate graph.
  Patch `fc-mapping-sync v2.0.0-dev (https://github.com/PNetwork/frontier?branch=patch-polkadot-v0.9.23#d7b30f9c)` was not used in the crate graph.
  Patch `fc-rpc v2.0.0-dev (https://github.com/PNetwork/frontier?branch=patch-polkadot-v0.9.23#d7b30f9c)` was not used in the crate graph.
  Patch `fc-rpc-core v1.1.0-dev (https://github.com/PNetwork/frontier?branch=patch-polkadot-v0.9.23#d7b30f9c)` was not used in the crate graph.
  Check that the patched package version and available features are compatible
  with the dependency requirements. If the patch has a different version from
  what is locked in the Cargo.lock file, run `cargo update` to use the new
  version. This may also occur with an optional dependency that is not enabled.
  warning: associated function is never used: `initialize`
     --> /mnt/sda3/polkadot/1pchain-chainbridge/pallets/bridge/src/lib.rs:470:5
      |
  470 |     fn initialize(
      |        ^^^^^^^^^^
      |
      = note: `#[warn(dead_code)]` on by default

  warning: `pallet-bridge` (lib) generated 1 warning
     Compiling h-runtime v0.0.1 (/mnt/sda3/polkadot/1pchain-chainbridge/runtime)
  error: duplicate lang item in crate `std` (which `runtime_common` depends on): `panic_impl`.
    |
    = note: the lang item is first defined in crate `sp_io` (which `frame_support` depends on)
    = note: first definition in `sp_io` loaded from /mnt/sda3/polkadot/1pchain-chainbridge/target/debug/wbuild/h-runtime/target/wasm32-unknown-unknown/release/deps/libsp_io-8c2aafc76099389a.rmeta
    = note: second definition in `std` loaded from /home/user2038/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/wasm32-unknown-unknown/lib/libstd-4faf99cd6c5513da.rlib

  error: duplicate lang item in crate `std` (which `runtime_common` depends on): `oom`.
    |
    = note: the lang item is first defined in crate `sp_io` (which `frame_support` depends on)
    = note: first definition in `sp_io` loaded from /mnt/sda3/polkadot/1pchain-chainbridge/target/debug/wbuild/h-runtime/target/wasm32-unknown-unknown/release/deps/libsp_io-8c2aafc76099389a.rmeta
    = note: second definition in `std` loaded from /home/user2038/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/wasm32-unknown-unknown/lib/libstd-4faf99cd6c5513da.rlib

  error: could not compile `h-runtime` due to 2 previous errors

I am aware of this post How to resolve duplicate lang item error?

I have default-features = false in my other Cargo.toml.

but for this runtime-common, I have no dependencies.

how can I make std not enabled by default in my runtime-common ?

Answer 1

add this line in the local crate at runtime-common/src/lib.rs:

#![cfg_attr(not(feature = "std"), no_std)]

If you use remote crates, add default-features = false, in your Cargo.toml. For example:

imported_crate = { git = "...", default-features = false, branch = "..." }

see more details about no_std: How to resolve duplicate lang item error?