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