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 #[allow(unused_macros)]
10 macro_rules! cfg_if {
11     // match if/else chains with a final `else`
12     ($(
13         if #[cfg($($meta:meta),*)] { $($it:item)* }
14     ) else * else {
15         $($it2:item)*
16     }) => {
17         cfg_if! {
18             @__items
19             () ;
20             $( ( ($($meta),*) ($($it)*) ), )*
21             ( () ($($it2)*) ),
22         }
23     };
24 
25     // match if/else chains lacking a final `else`
26     (
27         if #[cfg($($i_met:meta),*)] { $($i_it:item)* }
28         $(
29             else if #[cfg($($e_met:meta),*)] { $($e_it:item)* }
30         )*
31     ) => {
32         cfg_if! {
33             @__items
34             () ;
35             ( ($($i_met),*) ($($i_it)*) ),
36             $( ( ($($e_met),*) ($($e_it)*) ), )*
37             ( () () ),
38         }
39     };
40 
41     // Internal and recursive macro to emit all the items
42     //
43     // Collects all the negated cfgs in a list at the beginning and after the
44     // semicolon is all the remaining items
45     (@__items ($($not:meta,)*) ; ) => {};
46     (@__items ($($not:meta,)*) ; ( ($($m:meta),*) ($($it:item)*) ),
47      $($rest:tt)*) => {
48         // Emit all items within one block, applying an approprate #[cfg]. The
49         // #[cfg] will require all `$m` matchers specified and must also negate
50         // all previous matchers.
51         cfg_if! { @__apply cfg(all($($m,)* not(any($($not),*)))), $($it)* }
52 
53         // Recurse to emit all other items in `$rest`, and when we do so add all
54         // our `$m` matchers to the list of `$not` matchers as future emissions
55         // will have to negate everything we just matched as well.
56         cfg_if! { @__items ($($not,)* $($m,)*) ; $($rest)* }
57     };
58 
59     // Internal macro to Apply a cfg attribute to a list of items
60     (@__apply $m:meta, $($it:item)*) => {
61         $(#[$m] $it)*
62     };
63 }
64 
65 #[allow(unused_macros)]
66 macro_rules! s {
67     ($($(#[$attr:meta])* pub $t:ident $i:ident { $($field:tt)* })*) => ($(
68         s!(it: $(#[$attr])* pub $t $i { $($field)* });
69     )*);
70     (it: $(#[$attr:meta])* pub union $i:ident { $($field:tt)* }) => (
71         compile_error!("unions cannot derive extra traits, use s_no_extra_traits instead");
72     );
73     (it: $(#[$attr:meta])* pub struct $i:ident { $($field:tt)* }) => (
74         __item! {
75             #[repr(C)]
76             #[cfg_attr(feature = "extra_traits", derive(Debug, Eq, Hash, PartialEq))]
77             #[allow(deprecated)]
78             $(#[$attr])*
79             pub struct $i { $($field)* }
80         }
81         #[allow(deprecated)]
82         impl ::Copy for $i {}
83         #[allow(deprecated)]
84         impl ::Clone for $i {
85             fn clone(&self) -> $i { *self }
86         }
87     );
88 }
89 
90 #[allow(unused_macros)]
91 macro_rules! s_no_extra_traits {
92     ($($(#[$attr:meta])* pub $t:ident $i:ident { $($field:tt)* })*) => ($(
93         s_no_extra_traits!(it: $(#[$attr])* pub $t $i { $($field)* });
94     )*);
95     (it: $(#[$attr:meta])* pub union $i:ident { $($field:tt)* }) => (
96         cfg_if! {
97             if #[cfg(libc_union)] {
98                 __item! {
99                     #[repr(C)]
100                     $(#[$attr])*
101                     pub union $i { $($field)* }
102                 }
103 
104                 impl ::Copy for $i {}
105                 impl ::Clone for $i {
106                     fn clone(&self) -> $i { *self }
107                 }
108             }
109         }
110     );
111     (it: $(#[$attr:meta])* pub struct $i:ident { $($field:tt)* }) => (
112         __item! {
113             #[repr(C)]
114             $(#[$attr])*
115             pub struct $i { $($field)* }
116         }
117         impl ::Copy for $i {}
118         impl ::Clone for $i {
119             fn clone(&self) -> $i { *self }
120         }
121     );
122 }
123 
124 // This is a pretty horrible hack to allow us to conditionally mark
125 // some functions as 'const', without requiring users of this macro
126 // to care about the "const-extern-fn" feature.
127 //
128 // When 'const-extern-fn' is enabled, we emit the captured 'const' keyword
129 // in the expanded function.
130 //
131 // When 'const-extern-fn' is disabled, we always emit a plain 'pub unsafe extern fn'.
132 // Note that the expression matched by the macro is exactly the same - this allows
133 // users of this macro to work whether or not 'const-extern-fn' is enabled
134 //
135 // Unfortunately, we need to duplicate most of this macro between the 'cfg_if' blocks.
136 // This is because 'const unsafe extern fn' won't even parse on older compilers,
137 // so we need to avoid emitting it at all of 'const-extern-fn'.
138 //
139 // Specifically, moving the 'cfg_if' into the macro body will *not* work.
140 // Doing so would cause the '#[cfg(feature = "const-extern-fn")]' to be emiited
141 // into user code. The 'cfg' gate will not stop Rust from trying to parse the
142 // 'pub const unsafe extern fn', so users would get a compiler error even when
143 // the 'const-extern-fn' feature is disabled
144 //
145 // Note that users of this macro need to place 'const' in a weird position
146 // (after the closing ')' for the arguments, but before the return type).
147 // This was the only way I could satisfy the following two requirements:
148 // 1. Avoid ambuguity errors from 'macro_rules!' (which happen when writing '$foo:ident fn'
149 // 2. Allow users of this macro to mix 'pub fn foo' and 'pub const fn bar' within the same
150 // 'f!' block
151 cfg_if! {
152     if #[cfg(libc_const_extern_fn)] {
153         #[allow(unused_macros)]
154         macro_rules! f {
155             ($(pub $({$constness:ident})* fn $i:ident(
156                         $($arg:ident: $argty:ty),*
157             ) -> $ret:ty {
158                 $($body:stmt);*
159             })*) => ($(
160                 #[inline]
161                 pub $($constness)* unsafe extern fn $i($($arg: $argty),*
162                 ) -> $ret {
163                     $($body);*
164                 }
165             )*)
166         }
167 
168         #[allow(unused_macros)]
169         macro_rules! const_fn {
170             ($($({$constness:ident})* fn $i:ident(
171                         $($arg:ident: $argty:ty),*
172             ) -> $ret:ty {
173                 $($body:stmt);*
174             })*) => ($(
175                 #[inline]
176                 $($constness)* fn $i($($arg: $argty),*
177                 ) -> $ret {
178                     $($body);*
179                 }
180             )*)
181         }
182 
183     } else {
184         #[allow(unused_macros)]
185         macro_rules! f {
186             ($(pub $({$constness:ident})* fn $i:ident(
187                         $($arg:ident: $argty:ty),*
188             ) -> $ret:ty {
189                 $($body:stmt);*
190             })*) => ($(
191                 #[inline]
192                 pub unsafe extern fn $i($($arg: $argty),*
193                 ) -> $ret {
194                     $($body);*
195                 }
196             )*)
197         }
198 
199         #[allow(unused_macros)]
200         macro_rules! const_fn {
201             ($($({$constness:ident})* fn $i:ident(
202                         $($arg:ident: $argty:ty),*
203             ) -> $ret:ty {
204                 $($body:stmt);*
205             })*) => ($(
206                 #[inline]
207                 fn $i($($arg: $argty),*
208                 ) -> $ret {
209                     $($body);*
210                 }
211             )*)
212         }
213     }
214 }
215 
216 #[allow(unused_macros)]
217 macro_rules! __item {
218     ($i:item) => {
219         $i
220     };
221 }
222 
223 #[allow(unused_macros)]
224 macro_rules! align_const {
225     ($($(#[$attr:meta])*
226        pub const $name:ident : $t1:ty
227        = $t2:ident { $($field:tt)* };)*) => ($(
228         #[cfg(libc_align)]
229         $(#[$attr])*
230         pub const $name : $t1 = $t2 {
231             $($field)*
232         };
233         #[cfg(not(libc_align))]
234         $(#[$attr])*
235         pub const $name : $t1 = $t2 {
236             $($field)*
237             __align: [],
238         };
239     )*)
240 }
241 
242 // This macro is used to deprecate items that should be accessed via the mach crate
243 #[allow(unused_macros)]
244 macro_rules! deprecated_mach {
245     (pub const $id:ident: $ty:ty = $expr:expr;) => {
246         #[deprecated(
247             since = "0.2.55",
248             note = "Use the `mach` crate instead",
249         )]
250         #[allow(deprecated)]
251         pub const $id: $ty = $expr;
252     };
253     ($(pub const $id:ident: $ty:ty = $expr:expr;)*) => {
254         $(
255             deprecated_mach!(
256                 pub const $id: $ty = $expr;
257             );
258         )*
259     };
260     (pub type $id:ident = $ty:ty;) => {
261         #[deprecated(
262             since = "0.2.55",
263             note = "Use the `mach` crate instead",
264         )]
265         #[allow(deprecated)]
266         pub type $id = $ty;
267     };
268     ($(pub type $id:ident = $ty:ty;)*) => {
269         $(
270             deprecated_mach!(
271                 pub type $id = $ty;
272             );
273         )*
274     }
275 }
276