macro_rules! cfg_table { () => { ... }; (_ => $expr:expr,) => { ... }; ([$cfg:meta] => $expr:expr, $($tail:tt)*) => { ... }; (32 => $expr:expr, $($tail:tt)*) => { ... }; (64 => $expr:expr, $($tail:tt)*) => { ... }; ("32" => $expr:expr, $($tail:tt)*) => { ... }; ("64" => $expr:expr, $($tail:tt)*) => { ... }; (macos => $expr:expr, $($tail:tt)*) => { ... }; (linux => $expr:expr, $($tail:tt)*) => { ... }; (windows => $expr:expr, $($tail:tt)*) => { ... }; (macos32 => $expr:expr, $($tail:tt)*) => { ... }; (macos64 => $expr:expr, $($tail:tt)*) => { ... }; (linux32 => $expr:expr, $($tail:tt)*) => { ... }; (linux64 => $expr:expr, $($tail:tt)*) => { ... }; (win32 => $expr:expr, $($tail:tt)*) => { ... }; (win64 => $expr:expr, $($tail:tt)*) => { ... }; }
Expand description
A simple macro that expands to different values across compilation targets.
Note, that you must have a leading ,
in the macro invocation.
Panics
This macro will panic at runtime if no matching value is found.
Example
let var = cfg_table! {
[all(target_os = "freebsd", target_pointer_width = "64", feature = "my-feature")] => 1337, // custom
// common platforms
win32 => 32,
win64 => 64,
linux32 => 32,
linux64 => 64,
macos32 => 32,
macos64 => 64,
// pointer widths
32 => 1985,
"32" => 1985,
64 => 2003,
"64" => 2003,
_ => 123, // default value if nothing matches, this must be at the bottom
};
cfg_table! {
win32 => {
println!("You're on Windows 32-bit!");
},
win64 => {
println!("You're on Windows 64-bit!");
},
_ => {
panic!("What the heck is a \"Linux\"?");
},
};