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-rw-r--r--libc/src/macros.rs108
1 files changed, 108 insertions, 0 deletions
diff --git a/libc/src/macros.rs b/libc/src/macros.rs
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+/// A macro for defining #[cfg] if-else statements.
+///
+/// This is similar to the `if/elif` C preprocessor macro by allowing definition
+/// of a cascade of `#[cfg]` cases, emitting the implementation which matches
+/// first.
+///
+/// This allows you to conveniently provide a long list #[cfg]'d blocks of code
+/// without having to rewrite each clause multiple times.
+macro_rules! cfg_if {
+ ($(
+ if #[cfg($($meta:meta),*)] { $($it:item)* }
+ ) else * else {
+ $($it2:item)*
+ }) => {
+ __cfg_if_items! {
+ () ;
+ $( ( ($($meta),*) ($($it)*) ), )*
+ ( () ($($it2)*) ),
+ }
+ }
+}
+
+macro_rules! __cfg_if_items {
+ (($($not:meta,)*) ; ) => {};
+ (($($not:meta,)*) ; ( ($($m:meta),*) ($($it:item)*) ), $($rest:tt)*) => {
+ __cfg_if_apply! { cfg(all(not(any($($not),*)), $($m,)*)), $($it)* }
+ __cfg_if_items! { ($($not,)* $($m,)*) ; $($rest)* }
+ }
+}
+
+macro_rules! __cfg_if_apply {
+ ($m:meta, $($it:item)*) => {
+ $(#[$m] $it)*
+ }
+}
+
+macro_rules! s {
+ ($($(#[$attr:meta])* pub struct $i:ident { $($field:tt)* })*) => ($(
+ __item! {
+ #[repr(C)]
+ $(#[$attr])*
+ pub struct $i { $($field)* }
+ }
+ impl ::dox::Copy for $i {}
+ impl ::dox::Clone for $i {
+ fn clone(&self) -> $i { *self }
+ }
+ )*)
+}
+
+macro_rules! f {
+ ($(pub fn $i:ident($($arg:ident: $argty:ty),*) -> $ret:ty {
+ $($body:stmt);*
+ })*) => ($(
+ #[inline]
+ #[cfg(not(dox))]
+ pub unsafe extern fn $i($($arg: $argty),*) -> $ret {
+ $($body);*
+ }
+
+ #[cfg(dox)]
+ #[allow(dead_code)]
+ pub unsafe extern fn $i($($arg: $argty),*) -> $ret {
+ loop {}
+ }
+ )*)
+}
+
+macro_rules! __item {
+ ($i:item) => ($i)
+}
+
+#[cfg(test)]
+mod tests {
+ cfg_if! {
+ if #[cfg(test)] {
+ use std::option::Option as Option2;
+ fn works1() -> Option2<u32> { Some(1) }
+ } else {
+ fn works1() -> Option<u32> { None }
+ }
+ }
+
+ cfg_if! {
+ if #[cfg(foo)] {
+ fn works2() -> bool { false }
+ } else if #[cfg(test)] {
+ fn works2() -> bool { true }
+ } else {
+ fn works2() -> bool { false }
+ }
+ }
+
+ cfg_if! {
+ if #[cfg(foo)] {
+ fn works3() -> bool { false }
+ } else {
+ fn works3() -> bool { true }
+ }
+ }
+
+ #[test]
+ fn it_works() {
+ assert!(works1().is_some());
+ assert!(works2());
+ assert!(works3());
+ }
+}