https://github.com/rust-lang/cfg-if

A if/elif-like macro for Rust #[cfg] statements
https://github.com/rust-lang/cfg-if

Last synced: 1 day ago
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A if/elif-like macro for Rust #[cfg] statements

• Host: GitHub
• URL: https://github.com/rust-lang/cfg-if
• Owner: rust-lang
• License: apache-2.0
• Created: 2015-07-08T01:07:40.000Z (over 9 years ago)
• Default Branch: main
• Last Pushed: 2024-10-28T21:07:47.000Z (about 2 months ago)
• Last Synced: 2024-12-13T15:27:23.780Z (8 days ago)
• Language: Rust
• Size: 803 KB
• Stars: 574
• Watchers: 14
• Forks: 41
• Open Issues: 6
• Metadata Files:
  • Readme: README.md
  • License: LICENSE-APACHE

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README

        
# cfg-if

[Documentation](https://docs.rs/cfg-if)

A macro to ergonomically define an item depending on a large number of #[cfg]

parameters. Structured like an if-else chain, the first matching branch is the

item that gets emitted.

```toml

[dependencies]

cfg-if = "1.0"

```

## Example

```rust

cfg_if::cfg_if! {

    if #[cfg(unix)] {

        fn foo() { /* unix specific functionality */ }

    } else if #[cfg(target_pointer_width = "32")] {

        fn foo() { /* non-unix, 32-bit functionality */ }

    } else {

        fn foo() { /* fallback implementation */ }

    }

}

fn main() {

    foo();

}

```

The `cfg_if!` block above is expanded to:

```rust

#[cfg(unix)]

fn foo() { /* unix specific functionality */ }

#[cfg(all(target_pointer_width = "32", not(unix)))]

fn foo() { /* non-unix, 32-bit functionality */ }

#[cfg(not(any(unix, target_pointer_width = "32")))]

fn foo() { /* fallback implementation */ }        

```

# License

This project is licensed under either of

 * Apache License, Version 2.0, ([LICENSE-APACHE](LICENSE-APACHE) or

   https://www.apache.org/licenses/LICENSE-2.0)

 * MIT license ([LICENSE-MIT](LICENSE-MIT) or

   https://opensource.org/licenses/MIT)

at your option.

### Contribution

Unless you explicitly state otherwise, any contribution intentionally submitted

for inclusion in `cfg-if` by you, as defined in the Apache-2.0 license, shall be

dual licensed as above, without any additional terms or conditions.