src/libunwind/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 }