1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
|
# 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.
|
