src/liblibc/src/macros.rs

   1 /// A macro for defining #[cfg] if-else statements.
   2 ///
   3 /// This is similar to the `if/elif` C preprocessor macro by allowing definition
   4 /// of a cascade of `#[cfg]` cases, emitting the implementation which matches
   5 /// first.
   6 ///
   7 /// This allows you to conveniently provide a long list #[cfg]'d blocks of code
   8 /// without having to rewrite each clause multiple times.
   9 macro_rules! cfg_if {
  10     ($(
  11         if #[cfg($($meta:meta),*)] { $($it:item)* }
  12     ) else * else {
  13         $($it2:item)*
  14     }) => {
  15         __cfg_if_items! {
  16             () ;
  17             $( ( ($($meta),*) ($($it)*) ), )*
  18             ( () ($($it2)*) ),
  19         }
  20     }
  21 }
  22
  23 macro_rules! __cfg_if_items {
  24     (($($not:meta,)*) ; ) => {};
  25     (($($not:meta,)*) ; ( ($($m:meta),*) ($($it:item)*) ), $($rest:tt)*) => {
  26         __cfg_if_apply! { cfg(all(not(any($($not),*)), $($m,)*)), $($it)* }
  27         __cfg_if_items! { ($($not,)* $($m,)*) ; $($rest)* }
  28     }
  29 }
  30
  31 macro_rules! __cfg_if_apply {
  32     ($m:meta, $($it:item)*) => {
  33         $(#[$m] $it)*
  34     }
  35 }
  36
  37 macro_rules! s {
  38     ($($(#[$attr:meta])* pub struct $i:ident { $($field:tt)* })*) => ($(
  39         __item! {
  40             #[repr(C)]
  41             $(#[$attr])*
  42             pub struct $i { $($field)* }
  43         }
  44         impl ::dox::Copy for $i {}
  45         impl ::dox::Clone for $i {
  46             fn clone(&self) -> $i { *self }
  47         }
  48     )*)
  49 }
  50
  51 macro_rules! f {
  52     ($(pub fn $i:ident($($arg:ident: $argty:ty),*) -> $ret:ty {
  53         $($body:stmt);*
  54     })*) => ($(
  55         #[inline]
  56         #[cfg(not(dox))]
  57         pub unsafe extern fn $i($($arg: $argty),*) -> $ret {
  58             $($body);*
  59         }
  60
  61         #[cfg(dox)]
  62         #[allow(dead_code)]
  63         pub unsafe extern fn $i($($arg: $argty),*) -> $ret {
  64             loop {}
  65         }
  66     )*)
  67 }
  68
  69 macro_rules! __item {
  70     ($i:item) => ($i)
  71 }
  72
  73 #[cfg(test)]
  74 mod tests {
  75     cfg_if! {
  76         if #[cfg(test)] {
  77             use std::option::Option as Option2;
  78             fn works1() -> Option2<u32> { Some(1) }
  79         } else {
  80             fn works1() -> Option<u32> { None }
  81         }
  82     }
  83
  84     cfg_if! {
  85         if #[cfg(foo)] {
  86             fn works2() -> bool { false }
  87         } else if #[cfg(test)] {
  88             fn works2() -> bool { true }
  89         } else {
  90             fn works2() -> bool { false }
  91         }
  92     }
  93
  94     cfg_if! {
  95         if #[cfg(foo)] {
  96             fn works3() -> bool { false }
  97         } else {
  98             fn works3() -> bool { true }
  99         }
 100     }
 101
 102     #[test]
 103     fn it_works() {
 104         assert!(works1().is_some());
 105         assert!(works2());
 106         assert!(works3());
 107     }
 108 }