I want to write a library, some modules need to support no_std
, and others need to support std
.
I tried to write it with reference to other libraries, but it still seems to be wrong.
Cargo.toml:
[features]
default = ["std"]
std = []
lib.rs:
#![cfg_attr(feature = "no_std", no_std)]
#[cfg(feature = "no_std")]
pub mod no_std;
#[cfg(feature = "std")]
pub mod std;
Rust Analyzer told me:
code is inactive due to #[cfg] directives: feature = "no_std" is disabled
How to control the feature
in lib.rs
correctly?
Moreover, I want to write a model dependent on rayon crate. How can I add it through feature
?
#![cfg_attr(not(feature = "std"), no_std)]
#[cfg(not(feature = "std"))]
pub mod no_std {
use std::collections::VecDeque;
}
#[cfg(feature = "std")]
pub mod with_std {
use std::collections::VecDeque;
}
[features]
default = ["std"]
std = []
$ cargo c
warning: unused import: `std::collections::VecDeque`
--> src\lib.rs:10:9
|
10 | use std::collections::VecDeque;
| ^^^^^^^^^^^^^^^^^^^^^^^^^^
|
= note: `#[warn(unused_imports)]` on by default
warning: `draft1` (lib) generated 1 warning
Finished dev [unoptimized + debuginfo] target(s) in 0.00s
$ cargo c --no-default-features
Checking draft1 v0.1.0 (draft1)
error[E0433]: failed to resolve: use of undeclared crate or module `std`
--> src\lib.rs:5:9
|
5 | use std::collections::VecDeque;
| ^^^ use of undeclared crate or module `std`
For more information about this error, try `rustc --explain E0433`.
error: could not compile `draft1` due to previous error