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.
[dependencies]
cfg-if = "1.0"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:
#[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 */ } This project is licensed under either of
- Apache License, Version 2.0, (LICENSE-APACHE or https://www.apache.org/licenses/LICENSE-2.0)
- MIT license (LICENSE-MIT or https://opensource.org/licenses/MIT)
at your option.
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.