xref: /rust-libc-0.2.174/src/macros.rs (revision fc1f81dc) 
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         #[allow(deprecated)]
118         impl ::Copy for $i {}
119         #[allow(deprecated)]
120         impl ::Clone for $i {
121             fn clone(&self) -> $i { *self }
122         }
123     );
124 }
125 
126 #[allow(unused_macros)]
127 macro_rules! e {
128     ($($(#[$attr:meta])* pub enum $i:ident { $($field:tt)* })*) => ($(
129         __item! {
130             #[cfg_attr(feature = "extra_traits", derive(Debug, Eq, Hash, PartialEq))]
131             $(#[$attr])*
132             pub enum $i { $($field)* }
133         }
134         impl ::Copy for $i {}
135         impl ::Clone for $i {
136             fn clone(&self) -> $i { *self }
137         }
138     )*);
139 }
140 
141 #[allow(unused_macros)]
142 macro_rules! s_paren {
143     ($($(#[$attr:meta])* pub struct $i:ident ( $($field:tt)* ); )* ) => ($(
144         __item! {
145             #[cfg_attr(feature = "extra_traits", derive(Debug, Eq, Hash, PartialEq))]
146             $(#[$attr])*
147             pub struct $i ( $($field)* );
148         }
149         impl ::Copy for $i {}
150         impl ::Clone for $i {
151             fn clone(&self) -> $i { *self }
152         }
153     )*);
154 }
155 
156 // This is a pretty horrible hack to allow us to conditionally mark
157 // some functions as 'const', without requiring users of this macro
158 // to care about the "const-extern-fn" feature.
159 //
160 // When 'const-extern-fn' is enabled, we emit the captured 'const' keyword
161 // in the expanded function.
162 //
163 // When 'const-extern-fn' is disabled, we always emit a plain 'pub unsafe extern fn'.
164 // Note that the expression matched by the macro is exactly the same - this allows
165 // users of this macro to work whether or not 'const-extern-fn' is enabled
166 //
167 // Unfortunately, we need to duplicate most of this macro between the 'cfg_if' blocks.
168 // This is because 'const unsafe extern fn' won't even parse on older compilers,
169 // so we need to avoid emitting it at all of 'const-extern-fn'.
170 //
171 // Specifically, moving the 'cfg_if' into the macro body will *not* work.
172 // Doing so would cause the '#[cfg(feature = "const-extern-fn")]' to be emiited
173 // into user code. The 'cfg' gate will not stop Rust from trying to parse the
174 // 'pub const unsafe extern fn', so users would get a compiler error even when
175 // the 'const-extern-fn' feature is disabled
176 //
177 // Note that users of this macro need to place 'const' in a weird position
178 // (after the closing ')' for the arguments, but before the return type).
179 // This was the only way I could satisfy the following two requirements:
180 // 1. Avoid ambuguity errors from 'macro_rules!' (which happen when writing '$foo:ident fn'
181 // 2. Allow users of this macro to mix 'pub fn foo' and 'pub const fn bar' within the same
182 // 'f!' block
183 cfg_if! {
184     if #[cfg(libc_const_extern_fn)] {
185         #[allow(unused_macros)]
186         macro_rules! f {
187             ($(pub $({$constness:ident})* fn $i:ident(
188                         $($arg:ident: $argty:ty),*
189             ) -> $ret:ty {
190                 $($body:stmt);*
191             })*) => ($(
192                 #[inline]
193                 pub $($constness)* unsafe extern fn $i($($arg: $argty),*
194                 ) -> $ret {
195                     $($body);*
196                 }
197             )*)
198         }
199 
200         #[allow(unused_macros)]
201         macro_rules! safe_f {
202             ($(pub $({$constness:ident})* fn $i:ident(
203                         $($arg:ident: $argty:ty),*
204             ) -> $ret:ty {
205                 $($body:stmt);*
206             })*) => ($(
207                 #[inline]
208                 pub $($constness)* extern fn $i($($arg: $argty),*
209                 ) -> $ret {
210                     $($body);*
211                 }
212             )*)
213         }
214 
215         #[allow(unused_macros)]
216         macro_rules! const_fn {
217             ($($({$constness:ident})* fn $i:ident(
218                         $($arg:ident: $argty:ty),*
219             ) -> $ret:ty {
220                 $($body:stmt);*
221             })*) => ($(
222                 #[inline]
223                 $($constness)* fn $i($($arg: $argty),*
224                 ) -> $ret {
225                     $($body);*
226                 }
227             )*)
228         }
229 
230     } else {
231         #[allow(unused_macros)]
232         macro_rules! f {
233             ($(pub $({$constness:ident})* fn $i:ident(
234                         $($arg:ident: $argty:ty),*
235             ) -> $ret:ty {
236                 $($body:stmt);*
237             })*) => ($(
238                 #[inline]
239                 pub unsafe extern fn $i($($arg: $argty),*
240                 ) -> $ret {
241                     $($body);*
242                 }
243             )*)
244         }
245 
246         #[allow(unused_macros)]
247         macro_rules! safe_f {
248             ($(pub $({$constness:ident})* fn $i:ident(
249                         $($arg:ident: $argty:ty),*
250             ) -> $ret:ty {
251                 $($body:stmt);*
252             })*) => ($(
253                 #[inline]
254                 pub extern fn $i($($arg: $argty),*
255                 ) -> $ret {
256                     $($body);*
257                 }
258             )*)
259         }
260 
261         #[allow(unused_macros)]
262         macro_rules! const_fn {
263             ($($({$constness:ident})* fn $i:ident(
264                         $($arg:ident: $argty:ty),*
265             ) -> $ret:ty {
266                 $($body:stmt);*
267             })*) => ($(
268                 #[inline]
269                 fn $i($($arg: $argty),*
270                 ) -> $ret {
271                     $($body);*
272                 }
273             )*)
274         }
275     }
276 }
277 
278 #[allow(unused_macros)]
279 macro_rules! __item {
280     ($i:item) => {
281         $i
282     };
283 }
284 
285 #[allow(unused_macros)]
286 macro_rules! align_const {
287     ($($(#[$attr:meta])*
288        pub const $name:ident : $t1:ty
289        = $t2:ident { $($field:tt)* };)*) => ($(
290         #[cfg(libc_align)]
291         $(#[$attr])*
292         pub const $name : $t1 = $t2 {
293             $($field)*
294         };
295         #[cfg(not(libc_align))]
296         $(#[$attr])*
297         pub const $name : $t1 = $t2 {
298             $($field)*
299             __align: [],
300         };
301     )*)
302 }
303 
304 // This macro is used to deprecate items that should be accessed via the mach crate
305 #[allow(unused_macros)]
306 macro_rules! deprecated_mach {
307     (pub const $id:ident: $ty:ty = $expr:expr;) => {
308         #[deprecated(
309             since = "0.2.55",
310             note = "Use the `mach` crate instead",
311         )]
312         #[allow(deprecated)]
313         pub const $id: $ty = $expr;
314     };
315     ($(pub const $id:ident: $ty:ty = $expr:expr;)*) => {
316         $(
317             deprecated_mach!(
318                 pub const $id: $ty = $expr;
319             );
320         )*
321     };
322     (pub type $id:ident = $ty:ty;) => {
323         #[deprecated(
324             since = "0.2.55",
325             note = "Use the `mach` crate instead",
326         )]
327         #[allow(deprecated)]
328         pub type $id = $ty;
329     };
330     ($(pub type $id:ident = $ty:ty;)*) => {
331         $(
332             deprecated_mach!(
333                 pub type $id = $ty;
334             );
335         )*
336     }
337 }
338