libc/
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#[allow(unused_macros)]
10macro_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] $it)*
62    };
63}
64
65#[allow(unused_macros)]
66macro_rules! s {
67    ($($(#[$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) -> $i { *self }
86        }
87    );
88}
89
90#[allow(unused_macros)]
91macro_rules! s_no_extra_traits {
92    ($($(#[$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
151cfg_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)]
217macro_rules! __item {
218    ($i:item) => {
219        $i
220    };
221}
222
223#[allow(unused_macros)]
224macro_rules! align_const {
225    ($($(#[$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)]
244macro_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}