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1 | // Copyright 2013 The Rust Project Developers. See the COPYRIGHT |
2 | // file at the top-level directory of this distribution and at | |
3 | // http://rust-lang.org/COPYRIGHT. | |
4 | // | |
5 | // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or | |
6 | // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license | |
7 | // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your | |
8 | // option. This file may not be copied, modified, or distributed | |
9 | // except according to those terms. | |
10 | ||
11 | //! rustc compiler intrinsics. | |
12 | //! | |
3157f602 | 13 | //! The corresponding definitions are in librustc_trans/intrinsic.rs. |
1a4d82fc JJ |
14 | //! |
15 | //! # Volatiles | |
16 | //! | |
17 | //! The volatile intrinsics provide operations intended to act on I/O | |
18 | //! memory, which are guaranteed to not be reordered by the compiler | |
19 | //! across other volatile intrinsics. See the LLVM documentation on | |
20 | //! [[volatile]]. | |
21 | //! | |
22 | //! [volatile]: http://llvm.org/docs/LangRef.html#volatile-memory-accesses | |
23 | //! | |
24 | //! # Atomics | |
25 | //! | |
26 | //! The atomic intrinsics provide common atomic operations on machine | |
27 | //! words, with multiple possible memory orderings. They obey the same | |
28 | //! semantics as C++11. See the LLVM documentation on [[atomics]]. | |
29 | //! | |
30 | //! [atomics]: http://llvm.org/docs/Atomics.html | |
31 | //! | |
32 | //! A quick refresher on memory ordering: | |
33 | //! | |
34 | //! * Acquire - a barrier for acquiring a lock. Subsequent reads and writes | |
35 | //! take place after the barrier. | |
36 | //! * Release - a barrier for releasing a lock. Preceding reads and writes | |
37 | //! take place before the barrier. | |
38 | //! * Sequentially consistent - sequentially consistent operations are | |
39 | //! guaranteed to happen in order. This is the standard mode for working | |
40 | //! with atomic types and is equivalent to Java's `volatile`. | |
41 | ||
62682a34 SL |
42 | #![unstable(feature = "core_intrinsics", |
43 | reason = "intrinsics are unlikely to ever be stabilized, instead \ | |
44 | they should be used through stabilized interfaces \ | |
e9174d1e SL |
45 | in the rest of the standard library", |
46 | issue = "0")] | |
1a4d82fc JJ |
47 | #![allow(missing_docs)] |
48 | ||
1a4d82fc JJ |
49 | extern "rust-intrinsic" { |
50 | ||
62682a34 | 51 | // NB: These intrinsics take raw pointers because they mutate aliased |
1a4d82fc JJ |
52 | // memory, which is not valid for either `&` or `&mut`. |
53 | ||
54a0048b | 54 | pub fn atomic_cxchg<T>(dst: *mut T, old: T, src: T) -> (T, bool); |
54a0048b | 55 | pub fn atomic_cxchg_acq<T>(dst: *mut T, old: T, src: T) -> (T, bool); |
54a0048b | 56 | pub fn atomic_cxchg_rel<T>(dst: *mut T, old: T, src: T) -> (T, bool); |
54a0048b | 57 | pub fn atomic_cxchg_acqrel<T>(dst: *mut T, old: T, src: T) -> (T, bool); |
54a0048b | 58 | pub fn atomic_cxchg_relaxed<T>(dst: *mut T, old: T, src: T) -> (T, bool); |
54a0048b | 59 | pub fn atomic_cxchg_failrelaxed<T>(dst: *mut T, old: T, src: T) -> (T, bool); |
54a0048b | 60 | pub fn atomic_cxchg_failacq<T>(dst: *mut T, old: T, src: T) -> (T, bool); |
54a0048b | 61 | pub fn atomic_cxchg_acq_failrelaxed<T>(dst: *mut T, old: T, src: T) -> (T, bool); |
54a0048b SL |
62 | pub fn atomic_cxchg_acqrel_failrelaxed<T>(dst: *mut T, old: T, src: T) -> (T, bool); |
63 | ||
7453a54e | 64 | pub fn atomic_cxchgweak<T>(dst: *mut T, old: T, src: T) -> (T, bool); |
7453a54e | 65 | pub fn atomic_cxchgweak_acq<T>(dst: *mut T, old: T, src: T) -> (T, bool); |
7453a54e | 66 | pub fn atomic_cxchgweak_rel<T>(dst: *mut T, old: T, src: T) -> (T, bool); |
7453a54e | 67 | pub fn atomic_cxchgweak_acqrel<T>(dst: *mut T, old: T, src: T) -> (T, bool); |
7453a54e | 68 | pub fn atomic_cxchgweak_relaxed<T>(dst: *mut T, old: T, src: T) -> (T, bool); |
7453a54e | 69 | pub fn atomic_cxchgweak_failrelaxed<T>(dst: *mut T, old: T, src: T) -> (T, bool); |
7453a54e | 70 | pub fn atomic_cxchgweak_failacq<T>(dst: *mut T, old: T, src: T) -> (T, bool); |
7453a54e | 71 | pub fn atomic_cxchgweak_acq_failrelaxed<T>(dst: *mut T, old: T, src: T) -> (T, bool); |
7453a54e | 72 | pub fn atomic_cxchgweak_acqrel_failrelaxed<T>(dst: *mut T, old: T, src: T) -> (T, bool); |
1a4d82fc JJ |
73 | |
74 | pub fn atomic_load<T>(src: *const T) -> T; | |
75 | pub fn atomic_load_acq<T>(src: *const T) -> T; | |
76 | pub fn atomic_load_relaxed<T>(src: *const T) -> T; | |
77 | pub fn atomic_load_unordered<T>(src: *const T) -> T; | |
78 | ||
79 | pub fn atomic_store<T>(dst: *mut T, val: T); | |
80 | pub fn atomic_store_rel<T>(dst: *mut T, val: T); | |
81 | pub fn atomic_store_relaxed<T>(dst: *mut T, val: T); | |
82 | pub fn atomic_store_unordered<T>(dst: *mut T, val: T); | |
83 | ||
84 | pub fn atomic_xchg<T>(dst: *mut T, src: T) -> T; | |
85 | pub fn atomic_xchg_acq<T>(dst: *mut T, src: T) -> T; | |
86 | pub fn atomic_xchg_rel<T>(dst: *mut T, src: T) -> T; | |
87 | pub fn atomic_xchg_acqrel<T>(dst: *mut T, src: T) -> T; | |
88 | pub fn atomic_xchg_relaxed<T>(dst: *mut T, src: T) -> T; | |
89 | ||
90 | pub fn atomic_xadd<T>(dst: *mut T, src: T) -> T; | |
91 | pub fn atomic_xadd_acq<T>(dst: *mut T, src: T) -> T; | |
92 | pub fn atomic_xadd_rel<T>(dst: *mut T, src: T) -> T; | |
93 | pub fn atomic_xadd_acqrel<T>(dst: *mut T, src: T) -> T; | |
94 | pub fn atomic_xadd_relaxed<T>(dst: *mut T, src: T) -> T; | |
95 | ||
96 | pub fn atomic_xsub<T>(dst: *mut T, src: T) -> T; | |
97 | pub fn atomic_xsub_acq<T>(dst: *mut T, src: T) -> T; | |
98 | pub fn atomic_xsub_rel<T>(dst: *mut T, src: T) -> T; | |
99 | pub fn atomic_xsub_acqrel<T>(dst: *mut T, src: T) -> T; | |
100 | pub fn atomic_xsub_relaxed<T>(dst: *mut T, src: T) -> T; | |
101 | ||
102 | pub fn atomic_and<T>(dst: *mut T, src: T) -> T; | |
103 | pub fn atomic_and_acq<T>(dst: *mut T, src: T) -> T; | |
104 | pub fn atomic_and_rel<T>(dst: *mut T, src: T) -> T; | |
105 | pub fn atomic_and_acqrel<T>(dst: *mut T, src: T) -> T; | |
106 | pub fn atomic_and_relaxed<T>(dst: *mut T, src: T) -> T; | |
107 | ||
108 | pub fn atomic_nand<T>(dst: *mut T, src: T) -> T; | |
109 | pub fn atomic_nand_acq<T>(dst: *mut T, src: T) -> T; | |
110 | pub fn atomic_nand_rel<T>(dst: *mut T, src: T) -> T; | |
111 | pub fn atomic_nand_acqrel<T>(dst: *mut T, src: T) -> T; | |
112 | pub fn atomic_nand_relaxed<T>(dst: *mut T, src: T) -> T; | |
113 | ||
114 | pub fn atomic_or<T>(dst: *mut T, src: T) -> T; | |
115 | pub fn atomic_or_acq<T>(dst: *mut T, src: T) -> T; | |
116 | pub fn atomic_or_rel<T>(dst: *mut T, src: T) -> T; | |
117 | pub fn atomic_or_acqrel<T>(dst: *mut T, src: T) -> T; | |
118 | pub fn atomic_or_relaxed<T>(dst: *mut T, src: T) -> T; | |
119 | ||
120 | pub fn atomic_xor<T>(dst: *mut T, src: T) -> T; | |
121 | pub fn atomic_xor_acq<T>(dst: *mut T, src: T) -> T; | |
122 | pub fn atomic_xor_rel<T>(dst: *mut T, src: T) -> T; | |
123 | pub fn atomic_xor_acqrel<T>(dst: *mut T, src: T) -> T; | |
124 | pub fn atomic_xor_relaxed<T>(dst: *mut T, src: T) -> T; | |
125 | ||
126 | pub fn atomic_max<T>(dst: *mut T, src: T) -> T; | |
127 | pub fn atomic_max_acq<T>(dst: *mut T, src: T) -> T; | |
128 | pub fn atomic_max_rel<T>(dst: *mut T, src: T) -> T; | |
129 | pub fn atomic_max_acqrel<T>(dst: *mut T, src: T) -> T; | |
130 | pub fn atomic_max_relaxed<T>(dst: *mut T, src: T) -> T; | |
131 | ||
132 | pub fn atomic_min<T>(dst: *mut T, src: T) -> T; | |
133 | pub fn atomic_min_acq<T>(dst: *mut T, src: T) -> T; | |
134 | pub fn atomic_min_rel<T>(dst: *mut T, src: T) -> T; | |
135 | pub fn atomic_min_acqrel<T>(dst: *mut T, src: T) -> T; | |
136 | pub fn atomic_min_relaxed<T>(dst: *mut T, src: T) -> T; | |
137 | ||
138 | pub fn atomic_umin<T>(dst: *mut T, src: T) -> T; | |
139 | pub fn atomic_umin_acq<T>(dst: *mut T, src: T) -> T; | |
140 | pub fn atomic_umin_rel<T>(dst: *mut T, src: T) -> T; | |
141 | pub fn atomic_umin_acqrel<T>(dst: *mut T, src: T) -> T; | |
142 | pub fn atomic_umin_relaxed<T>(dst: *mut T, src: T) -> T; | |
143 | ||
144 | pub fn atomic_umax<T>(dst: *mut T, src: T) -> T; | |
145 | pub fn atomic_umax_acq<T>(dst: *mut T, src: T) -> T; | |
146 | pub fn atomic_umax_rel<T>(dst: *mut T, src: T) -> T; | |
147 | pub fn atomic_umax_acqrel<T>(dst: *mut T, src: T) -> T; | |
148 | pub fn atomic_umax_relaxed<T>(dst: *mut T, src: T) -> T; | |
149 | } | |
150 | ||
151 | extern "rust-intrinsic" { | |
152 | ||
153 | pub fn atomic_fence(); | |
154 | pub fn atomic_fence_acq(); | |
155 | pub fn atomic_fence_rel(); | |
156 | pub fn atomic_fence_acqrel(); | |
157 | ||
d9579d0f AL |
158 | /// A compiler-only memory barrier. |
159 | /// | |
62682a34 SL |
160 | /// Memory accesses will never be reordered across this barrier by the |
161 | /// compiler, but no instructions will be emitted for it. This is | |
162 | /// appropriate for operations on the same thread that may be preempted, | |
163 | /// such as when interacting with signal handlers. | |
d9579d0f | 164 | pub fn atomic_singlethreadfence(); |
d9579d0f | 165 | pub fn atomic_singlethreadfence_acq(); |
d9579d0f | 166 | pub fn atomic_singlethreadfence_rel(); |
d9579d0f AL |
167 | pub fn atomic_singlethreadfence_acqrel(); |
168 | ||
3157f602 XL |
169 | /// Magic intrinsic that derives its meaning from attributes |
170 | /// attached to the function. | |
171 | /// | |
172 | /// For example, dataflow uses this to inject static assertions so | |
173 | /// that `rustc_peek(potentially_uninitialized)` would actually | |
174 | /// double-check that dataflow did indeed compute that it is | |
175 | /// uninitialized at that point in the control flow. | |
3157f602 XL |
176 | pub fn rustc_peek<T>(_: T) -> T; |
177 | ||
9346a6ac | 178 | /// Aborts the execution of the process. |
1a4d82fc JJ |
179 | pub fn abort() -> !; |
180 | ||
9346a6ac | 181 | /// Tells LLVM that this point in the code is not reachable, |
1a4d82fc JJ |
182 | /// enabling further optimizations. |
183 | /// | |
184 | /// NB: This is very different from the `unreachable!()` macro! | |
185 | pub fn unreachable() -> !; | |
186 | ||
9346a6ac | 187 | /// Informs the optimizer that a condition is always true. |
1a4d82fc JJ |
188 | /// If the condition is false, the behavior is undefined. |
189 | /// | |
190 | /// No code is generated for this intrinsic, but the optimizer will try | |
191 | /// to preserve it (and its condition) between passes, which may interfere | |
192 | /// with optimization of surrounding code and reduce performance. It should | |
193 | /// not be used if the invariant can be discovered by the optimizer on its | |
194 | /// own, or if it does not enable any significant optimizations. | |
195 | pub fn assume(b: bool); | |
196 | ||
9e0c209e SL |
197 | #[cfg(not(stage0))] |
198 | /// Hints to the compiler that branch condition is likely to be true. | |
199 | /// Returns the value passed to it. | |
200 | /// | |
201 | /// Any use other than with `if` statements will probably not have an effect. | |
202 | pub fn likely(b: bool) -> bool; | |
203 | ||
204 | #[cfg(not(stage0))] | |
205 | /// Hints to the compiler that branch condition is likely to be false. | |
206 | /// Returns the value passed to it. | |
207 | /// | |
208 | /// Any use other than with `if` statements will probably not have an effect. | |
209 | pub fn unlikely(b: bool) -> bool; | |
210 | ||
9346a6ac | 211 | /// Executes a breakpoint trap, for inspection by a debugger. |
1a4d82fc JJ |
212 | pub fn breakpoint(); |
213 | ||
214 | /// The size of a type in bytes. | |
215 | /// | |
a7813a04 XL |
216 | /// More specifically, this is the offset in bytes between successive |
217 | /// items of the same type, including alignment padding. | |
85aaf69f | 218 | pub fn size_of<T>() -> usize; |
1a4d82fc | 219 | |
9346a6ac | 220 | /// Moves a value to an uninitialized memory location. |
1a4d82fc JJ |
221 | /// |
222 | /// Drop glue is not run on the destination. | |
c1a9b12d | 223 | pub fn move_val_init<T>(dst: *mut T, src: T); |
1a4d82fc | 224 | |
85aaf69f SL |
225 | pub fn min_align_of<T>() -> usize; |
226 | pub fn pref_align_of<T>() -> usize; | |
1a4d82fc | 227 | |
d9579d0f | 228 | pub fn size_of_val<T: ?Sized>(_: &T) -> usize; |
d9579d0f | 229 | pub fn min_align_of_val<T: ?Sized>(_: &T) -> usize; |
92a42be0 SL |
230 | |
231 | /// Executes the destructor (if any) of the pointed-to value. | |
232 | /// | |
233 | /// This has two use cases: | |
234 | /// | |
235 | /// * It is *required* to use `drop_in_place` to drop unsized types like | |
236 | /// trait objects, because they can't be read out onto the stack and | |
237 | /// dropped normally. | |
238 | /// | |
239 | /// * It is friendlier to the optimizer to do this over `ptr::read` when | |
240 | /// dropping manually allocated memory (e.g. when writing Box/Rc/Vec), | |
241 | /// as the compiler doesn't need to prove that it's sound to elide the | |
242 | /// copy. | |
243 | /// | |
244 | /// # Undefined Behavior | |
245 | /// | |
246 | /// This has all the same safety problems as `ptr::read` with respect to | |
247 | /// invalid pointers, types, and double drops. | |
7453a54e | 248 | #[stable(feature = "drop_in_place", since = "1.8.0")] |
92a42be0 | 249 | pub fn drop_in_place<T: ?Sized>(to_drop: *mut T); |
d9579d0f | 250 | |
c34b1796 AL |
251 | /// Gets a static string slice containing the name of a type. |
252 | pub fn type_name<T: ?Sized>() -> &'static str; | |
1a4d82fc JJ |
253 | |
254 | /// Gets an identifier which is globally unique to the specified type. This | |
255 | /// function will return the same value for a type regardless of whichever | |
256 | /// crate it is invoked in. | |
85aaf69f | 257 | pub fn type_id<T: ?Sized + 'static>() -> u64; |
1a4d82fc | 258 | |
9346a6ac | 259 | /// Creates a value initialized to zero. |
1a4d82fc JJ |
260 | /// |
261 | /// `init` is unsafe because it returns a zeroed-out datum, | |
c34b1796 AL |
262 | /// which is unsafe unless T is `Copy`. Also, even if T is |
263 | /// `Copy`, an all-zero value may not correspond to any legitimate | |
264 | /// state for the type in question. | |
1a4d82fc JJ |
265 | pub fn init<T>() -> T; |
266 | ||
9346a6ac | 267 | /// Creates an uninitialized value. |
c34b1796 AL |
268 | /// |
269 | /// `uninit` is unsafe because there is no guarantee of what its | |
270 | /// contents are. In particular its drop-flag may be set to any | |
271 | /// state, which means it may claim either dropped or | |
272 | /// undropped. In the general case one must use `ptr::write` to | |
273 | /// initialize memory previous set to the result of `uninit`. | |
1a4d82fc JJ |
274 | pub fn uninit<T>() -> T; |
275 | ||
9346a6ac | 276 | /// Moves a value out of scope without running drop glue. |
1a4d82fc JJ |
277 | pub fn forget<T>(_: T) -> (); |
278 | ||
9e0c209e SL |
279 | /// Reinterprets the bits of a value of one type as another type. |
280 | /// | |
281 | /// Both types must have the same size. Neither the original, nor the result, | |
282 | /// may be an [invalid value](../../nomicon/meet-safe-and-unsafe.html). | |
1a4d82fc | 283 | /// |
5bcae85e | 284 | /// `transmute` is semantically equivalent to a bitwise move of one type |
9e0c209e SL |
285 | /// into another. It copies the bits from the source value into the |
286 | /// destination value, then forgets the original. It's equivalent to C's | |
287 | /// `memcpy` under the hood, just like `transmute_copy`. | |
5bcae85e | 288 | /// |
9e0c209e SL |
289 | /// `transmute` is **incredibly** unsafe. There are a vast number of ways to |
290 | /// cause [undefined behavior][ub] with this function. `transmute` should be | |
5bcae85e SL |
291 | /// the absolute last resort. |
292 | /// | |
293 | /// The [nomicon](../../nomicon/transmutes.html) has additional | |
294 | /// documentation. | |
1a4d82fc | 295 | /// |
9e0c209e SL |
296 | /// [ub]: ../../reference.html#behavior-considered-undefined |
297 | /// | |
1a4d82fc JJ |
298 | /// # Examples |
299 | /// | |
5bcae85e SL |
300 | /// There are a few things that `transmute` is really useful for. |
301 | /// | |
302 | /// Getting the bitpattern of a floating point type (or, more generally, | |
303 | /// type punning, when `T` and `U` aren't pointers): | |
304 | /// | |
305 | /// ``` | |
306 | /// let bitpattern = unsafe { | |
307 | /// std::mem::transmute::<f32, u32>(1.0) | |
308 | /// }; | |
309 | /// assert_eq!(bitpattern, 0x3F800000); | |
310 | /// ``` | |
311 | /// | |
9e0c209e SL |
312 | /// Turning a pointer into a function pointer. This is *not* portable to |
313 | /// machines where function pointers and data pointers have different sizes. | |
5bcae85e SL |
314 | /// |
315 | /// ``` | |
316 | /// fn foo() -> i32 { | |
317 | /// 0 | |
318 | /// } | |
319 | /// let pointer = foo as *const (); | |
320 | /// let function = unsafe { | |
321 | /// std::mem::transmute::<*const (), fn() -> i32>(pointer) | |
322 | /// }; | |
323 | /// assert_eq!(function(), 0); | |
324 | /// ``` | |
325 | /// | |
9e0c209e SL |
326 | /// Extending a lifetime, or shortening an invariant lifetime. This is |
327 | /// advanced, very unsafe Rust! | |
5bcae85e SL |
328 | /// |
329 | /// ``` | |
330 | /// struct R<'a>(&'a i32); | |
331 | /// unsafe fn extend_lifetime<'b>(r: R<'b>) -> R<'static> { | |
332 | /// std::mem::transmute::<R<'b>, R<'static>>(r) | |
333 | /// } | |
334 | /// | |
335 | /// unsafe fn shorten_invariant_lifetime<'b, 'c>(r: &'b mut R<'static>) | |
336 | /// -> &'b mut R<'c> { | |
337 | /// std::mem::transmute::<&'b mut R<'static>, &'b mut R<'c>>(r) | |
338 | /// } | |
339 | /// ``` | |
340 | /// | |
341 | /// # Alternatives | |
342 | /// | |
9e0c209e SL |
343 | /// Don't despair: many uses of `transmute` can be achieved through other means. |
344 | /// Below are common applications of `transmute` which can be replaced with safer | |
345 | /// constructs. | |
5bcae85e SL |
346 | /// |
347 | /// Turning a pointer into a `usize`: | |
348 | /// | |
349 | /// ``` | |
350 | /// let ptr = &0; | |
351 | /// let ptr_num_transmute = unsafe { | |
352 | /// std::mem::transmute::<&i32, usize>(ptr) | |
353 | /// }; | |
9e0c209e | 354 | /// |
5bcae85e SL |
355 | /// // Use an `as` cast instead |
356 | /// let ptr_num_cast = ptr as *const i32 as usize; | |
357 | /// ``` | |
358 | /// | |
359 | /// Turning a `*mut T` into an `&mut T`: | |
360 | /// | |
361 | /// ``` | |
362 | /// let ptr: *mut i32 = &mut 0; | |
363 | /// let ref_transmuted = unsafe { | |
364 | /// std::mem::transmute::<*mut i32, &mut i32>(ptr) | |
365 | /// }; | |
9e0c209e | 366 | /// |
5bcae85e SL |
367 | /// // Use a reborrow instead |
368 | /// let ref_casted = unsafe { &mut *ptr }; | |
369 | /// ``` | |
370 | /// | |
371 | /// Turning an `&mut T` into an `&mut U`: | |
372 | /// | |
373 | /// ``` | |
374 | /// let ptr = &mut 0; | |
375 | /// let val_transmuted = unsafe { | |
376 | /// std::mem::transmute::<&mut i32, &mut u32>(ptr) | |
377 | /// }; | |
9e0c209e | 378 | /// |
5bcae85e SL |
379 | /// // Now, put together `as` and reborrowing - note the chaining of `as` |
380 | /// // `as` is not transitive | |
381 | /// let val_casts = unsafe { &mut *(ptr as *mut i32 as *mut u32) }; | |
382 | /// ``` | |
383 | /// | |
384 | /// Turning an `&str` into an `&[u8]`: | |
385 | /// | |
386 | /// ``` | |
387 | /// // this is not a good way to do this. | |
388 | /// let slice = unsafe { std::mem::transmute::<&str, &[u8]>("Rust") }; | |
389 | /// assert_eq!(slice, &[82, 117, 115, 116]); | |
9e0c209e | 390 | /// |
5bcae85e SL |
391 | /// // You could use `str::as_bytes` |
392 | /// let slice = "Rust".as_bytes(); | |
393 | /// assert_eq!(slice, &[82, 117, 115, 116]); | |
9e0c209e | 394 | /// |
5bcae85e SL |
395 | /// // Or, just use a byte string, if you have control over the string |
396 | /// // literal | |
397 | /// assert_eq!(b"Rust", &[82, 117, 115, 116]); | |
398 | /// ``` | |
399 | /// | |
400 | /// Turning a `Vec<&T>` into a `Vec<Option<&T>>`: | |
401 | /// | |
85aaf69f | 402 | /// ``` |
5bcae85e SL |
403 | /// let store = [0, 1, 2, 3]; |
404 | /// let mut v_orig = store.iter().collect::<Vec<&i32>>(); | |
9e0c209e | 405 | /// |
5bcae85e SL |
406 | /// // Using transmute: this is Undefined Behavior, and a bad idea. |
407 | /// // However, it is no-copy. | |
408 | /// let v_transmuted = unsafe { | |
409 | /// std::mem::transmute::<Vec<&i32>, Vec<Option<&i32>>>( | |
410 | /// v_orig.clone()) | |
411 | /// }; | |
9e0c209e | 412 | /// |
5bcae85e | 413 | /// // This is the suggested, safe way. |
9e0c209e | 414 | /// // It does copy the entire vector, though, into a new array. |
5bcae85e SL |
415 | /// let v_collected = v_orig.clone() |
416 | /// .into_iter() | |
417 | /// .map(|r| Some(r)) | |
418 | /// .collect::<Vec<Option<&i32>>>(); | |
9e0c209e | 419 | /// |
5bcae85e SL |
420 | /// // The no-copy, unsafe way, still using transmute, but not UB. |
421 | /// // This is equivalent to the original, but safer, and reuses the | |
422 | /// // same Vec internals. Therefore the new inner type must have the | |
423 | /// // exact same size, and the same or lesser alignment, as the old | |
424 | /// // type. The same caveats exist for this method as transmute, for | |
425 | /// // the original inner type (`&i32`) to the converted inner type | |
426 | /// // (`Option<&i32>`), so read the nomicon pages linked above. | |
427 | /// let v_from_raw = unsafe { | |
428 | /// Vec::from_raw_parts(v_orig.as_mut_ptr(), | |
429 | /// v_orig.len(), | |
430 | /// v_orig.capacity()) | |
431 | /// }; | |
432 | /// std::mem::forget(v_orig); | |
433 | /// ``` | |
434 | /// | |
435 | /// Implementing `split_at_mut`: | |
1a4d82fc | 436 | /// |
5bcae85e SL |
437 | /// ``` |
438 | /// use std::{slice, mem}; | |
9e0c209e | 439 | /// |
5bcae85e SL |
440 | /// // There are multiple ways to do this; and there are multiple problems |
441 | /// // with the following, transmute, way. | |
442 | /// fn split_at_mut_transmute<T>(slice: &mut [T], mid: usize) | |
443 | /// -> (&mut [T], &mut [T]) { | |
444 | /// let len = slice.len(); | |
445 | /// assert!(mid <= len); | |
446 | /// unsafe { | |
447 | /// let slice2 = mem::transmute::<&mut [T], &mut [T]>(slice); | |
448 | /// // first: transmute is not typesafe; all it checks is that T and | |
449 | /// // U are of the same size. Second, right here, you have two | |
450 | /// // mutable references pointing to the same memory. | |
451 | /// (&mut slice[0..mid], &mut slice2[mid..len]) | |
452 | /// } | |
453 | /// } | |
9e0c209e | 454 | /// |
5bcae85e SL |
455 | /// // This gets rid of the typesafety problems; `&mut *` will *only* give |
456 | /// // you an `&mut T` from an `&mut T` or `*mut T`. | |
457 | /// fn split_at_mut_casts<T>(slice: &mut [T], mid: usize) | |
458 | /// -> (&mut [T], &mut [T]) { | |
459 | /// let len = slice.len(); | |
460 | /// assert!(mid <= len); | |
461 | /// unsafe { | |
462 | /// let slice2 = &mut *(slice as *mut [T]); | |
463 | /// // however, you still have two mutable references pointing to | |
464 | /// // the same memory. | |
465 | /// (&mut slice[0..mid], &mut slice2[mid..len]) | |
466 | /// } | |
467 | /// } | |
9e0c209e | 468 | /// |
5bcae85e SL |
469 | /// // This is how the standard library does it. This is the best method, if |
470 | /// // you need to do something like this | |
471 | /// fn split_at_stdlib<T>(slice: &mut [T], mid: usize) | |
472 | /// -> (&mut [T], &mut [T]) { | |
473 | /// let len = slice.len(); | |
474 | /// assert!(mid <= len); | |
475 | /// unsafe { | |
476 | /// let ptr = slice.as_mut_ptr(); | |
477 | /// // This now has three mutable references pointing at the same | |
478 | /// // memory. `slice`, the rvalue ret.0, and the rvalue ret.1. | |
479 | /// // `slice` is never used after `let ptr = ...`, and so one can | |
480 | /// // treat it as "dead", and therefore, you only have two real | |
481 | /// // mutable slices. | |
482 | /// (slice::from_raw_parts_mut(ptr, mid), | |
483 | /// slice::from_raw_parts_mut(ptr.offset(mid as isize), len - mid)) | |
484 | /// } | |
485 | /// } | |
1a4d82fc | 486 | /// ``` |
85aaf69f | 487 | #[stable(feature = "rust1", since = "1.0.0")] |
e9174d1e | 488 | pub fn transmute<T, U>(e: T) -> U; |
1a4d82fc | 489 | |
c34b1796 AL |
490 | /// Returns `true` if the actual type given as `T` requires drop |
491 | /// glue; returns `false` if the actual type provided for `T` | |
492 | /// implements `Copy`. | |
493 | /// | |
494 | /// If the actual type neither requires drop glue nor implements | |
495 | /// `Copy`, then may return `true` or `false`. | |
1a4d82fc JJ |
496 | pub fn needs_drop<T>() -> bool; |
497 | ||
d9579d0f | 498 | /// Calculates the offset from a pointer. |
1a4d82fc JJ |
499 | /// |
500 | /// This is implemented as an intrinsic to avoid converting to and from an | |
501 | /// integer, since the conversion would throw away aliasing information. | |
d9579d0f AL |
502 | /// |
503 | /// # Safety | |
504 | /// | |
505 | /// Both the starting and resulting pointer must be either in bounds or one | |
506 | /// byte past the end of an allocated object. If either pointer is out of | |
507 | /// bounds or arithmetic overflow occurs then any further use of the | |
508 | /// returned value will result in undefined behavior. | |
85aaf69f | 509 | pub fn offset<T>(dst: *const T, offset: isize) -> *const T; |
1a4d82fc | 510 | |
62682a34 SL |
511 | /// Calculates the offset from a pointer, potentially wrapping. |
512 | /// | |
513 | /// This is implemented as an intrinsic to avoid converting to and from an | |
514 | /// integer, since the conversion inhibits certain optimizations. | |
515 | /// | |
516 | /// # Safety | |
517 | /// | |
518 | /// Unlike the `offset` intrinsic, this intrinsic does not restrict the | |
519 | /// resulting pointer to point into or one byte past the end of an allocated | |
520 | /// object, and it wraps with two's complement arithmetic. The resulting | |
521 | /// value is not necessarily valid to be used to actually access memory. | |
522 | pub fn arith_offset<T>(dst: *const T, offset: isize) -> *const T; | |
523 | ||
1a4d82fc JJ |
524 | /// Copies `count * size_of<T>` bytes from `src` to `dst`. The source |
525 | /// and destination may *not* overlap. | |
526 | /// | |
c34b1796 | 527 | /// `copy_nonoverlapping` is semantically equivalent to C's `memcpy`. |
1a4d82fc JJ |
528 | /// |
529 | /// # Safety | |
530 | /// | |
85aaf69f | 531 | /// Beyond requiring that the program must be allowed to access both regions |
b039eaaf | 532 | /// of memory, it is Undefined Behavior for source and destination to |
85aaf69f SL |
533 | /// overlap. Care must also be taken with the ownership of `src` and |
534 | /// `dst`. This method semantically moves the values of `src` into `dst`. | |
535 | /// However it does not drop the contents of `dst`, or prevent the contents | |
536 | /// of `src` from being dropped or used. | |
1a4d82fc JJ |
537 | /// |
538 | /// # Examples | |
539 | /// | |
540 | /// A safe swap function: | |
541 | /// | |
542 | /// ``` | |
543 | /// use std::mem; | |
544 | /// use std::ptr; | |
545 | /// | |
92a42be0 | 546 | /// # #[allow(dead_code)] |
1a4d82fc JJ |
547 | /// fn swap<T>(x: &mut T, y: &mut T) { |
548 | /// unsafe { | |
549 | /// // Give ourselves some scratch space to work with | |
550 | /// let mut t: T = mem::uninitialized(); | |
551 | /// | |
552 | /// // Perform the swap, `&mut` pointers never alias | |
c34b1796 AL |
553 | /// ptr::copy_nonoverlapping(x, &mut t, 1); |
554 | /// ptr::copy_nonoverlapping(y, x, 1); | |
555 | /// ptr::copy_nonoverlapping(&t, y, 1); | |
1a4d82fc JJ |
556 | /// |
557 | /// // y and t now point to the same thing, but we need to completely forget `tmp` | |
558 | /// // because it's no longer relevant. | |
559 | /// mem::forget(t); | |
560 | /// } | |
561 | /// } | |
562 | /// ``` | |
c34b1796 | 563 | #[stable(feature = "rust1", since = "1.0.0")] |
c34b1796 AL |
564 | pub fn copy_nonoverlapping<T>(src: *const T, dst: *mut T, count: usize); |
565 | ||
1a4d82fc JJ |
566 | /// Copies `count * size_of<T>` bytes from `src` to `dst`. The source |
567 | /// and destination may overlap. | |
568 | /// | |
c34b1796 | 569 | /// `copy` is semantically equivalent to C's `memmove`. |
1a4d82fc JJ |
570 | /// |
571 | /// # Safety | |
572 | /// | |
573 | /// Care must be taken with the ownership of `src` and `dst`. | |
574 | /// This method semantically moves the values of `src` into `dst`. | |
575 | /// However it does not drop the contents of `dst`, or prevent the contents of `src` | |
576 | /// from being dropped or used. | |
577 | /// | |
578 | /// # Examples | |
579 | /// | |
580 | /// Efficiently create a Rust vector from an unsafe buffer: | |
581 | /// | |
582 | /// ``` | |
583 | /// use std::ptr; | |
584 | /// | |
92a42be0 | 585 | /// # #[allow(dead_code)] |
c34b1796 | 586 | /// unsafe fn from_buf_raw<T>(ptr: *const T, elts: usize) -> Vec<T> { |
1a4d82fc JJ |
587 | /// let mut dst = Vec::with_capacity(elts); |
588 | /// dst.set_len(elts); | |
c34b1796 | 589 | /// ptr::copy(ptr, dst.as_mut_ptr(), elts); |
1a4d82fc JJ |
590 | /// dst |
591 | /// } | |
592 | /// ``` | |
593 | /// | |
c34b1796 | 594 | #[stable(feature = "rust1", since = "1.0.0")] |
c34b1796 AL |
595 | pub fn copy<T>(src: *const T, dst: *mut T, count: usize); |
596 | ||
1a4d82fc | 597 | /// Invokes memset on the specified pointer, setting `count * size_of::<T>()` |
92a42be0 | 598 | /// bytes of memory starting at `dst` to `val`. |
c34b1796 AL |
599 | #[stable(feature = "rust1", since = "1.0.0")] |
600 | pub fn write_bytes<T>(dst: *mut T, val: u8, count: usize); | |
1a4d82fc JJ |
601 | |
602 | /// Equivalent to the appropriate `llvm.memcpy.p0i8.0i8.*` intrinsic, with | |
603 | /// a size of `count` * `size_of::<T>()` and an alignment of | |
604 | /// `min_align_of::<T>()` | |
605 | /// | |
b039eaaf | 606 | /// The volatile parameter is set to `true`, so it will not be optimized out. |
1a4d82fc | 607 | pub fn volatile_copy_nonoverlapping_memory<T>(dst: *mut T, src: *const T, |
85aaf69f | 608 | count: usize); |
1a4d82fc JJ |
609 | /// Equivalent to the appropriate `llvm.memmove.p0i8.0i8.*` intrinsic, with |
610 | /// a size of `count` * `size_of::<T>()` and an alignment of | |
611 | /// `min_align_of::<T>()` | |
612 | /// | |
b039eaaf | 613 | /// The volatile parameter is set to `true`, so it will not be optimized out. |
85aaf69f | 614 | pub fn volatile_copy_memory<T>(dst: *mut T, src: *const T, count: usize); |
1a4d82fc JJ |
615 | /// Equivalent to the appropriate `llvm.memset.p0i8.*` intrinsic, with a |
616 | /// size of `count` * `size_of::<T>()` and an alignment of | |
617 | /// `min_align_of::<T>()`. | |
618 | /// | |
b039eaaf | 619 | /// The volatile parameter is set to `true`, so it will not be optimized out. |
85aaf69f | 620 | pub fn volatile_set_memory<T>(dst: *mut T, val: u8, count: usize); |
1a4d82fc JJ |
621 | |
622 | /// Perform a volatile load from the `src` pointer. | |
623 | pub fn volatile_load<T>(src: *const T) -> T; | |
624 | /// Perform a volatile store to the `dst` pointer. | |
625 | pub fn volatile_store<T>(dst: *mut T, val: T); | |
626 | ||
627 | /// Returns the square root of an `f32` | |
628 | pub fn sqrtf32(x: f32) -> f32; | |
629 | /// Returns the square root of an `f64` | |
630 | pub fn sqrtf64(x: f64) -> f64; | |
631 | ||
632 | /// Raises an `f32` to an integer power. | |
633 | pub fn powif32(a: f32, x: i32) -> f32; | |
634 | /// Raises an `f64` to an integer power. | |
635 | pub fn powif64(a: f64, x: i32) -> f64; | |
636 | ||
637 | /// Returns the sine of an `f32`. | |
638 | pub fn sinf32(x: f32) -> f32; | |
639 | /// Returns the sine of an `f64`. | |
640 | pub fn sinf64(x: f64) -> f64; | |
641 | ||
642 | /// Returns the cosine of an `f32`. | |
643 | pub fn cosf32(x: f32) -> f32; | |
644 | /// Returns the cosine of an `f64`. | |
645 | pub fn cosf64(x: f64) -> f64; | |
646 | ||
647 | /// Raises an `f32` to an `f32` power. | |
648 | pub fn powf32(a: f32, x: f32) -> f32; | |
649 | /// Raises an `f64` to an `f64` power. | |
650 | pub fn powf64(a: f64, x: f64) -> f64; | |
651 | ||
652 | /// Returns the exponential of an `f32`. | |
653 | pub fn expf32(x: f32) -> f32; | |
654 | /// Returns the exponential of an `f64`. | |
655 | pub fn expf64(x: f64) -> f64; | |
656 | ||
657 | /// Returns 2 raised to the power of an `f32`. | |
658 | pub fn exp2f32(x: f32) -> f32; | |
659 | /// Returns 2 raised to the power of an `f64`. | |
660 | pub fn exp2f64(x: f64) -> f64; | |
661 | ||
662 | /// Returns the natural logarithm of an `f32`. | |
663 | pub fn logf32(x: f32) -> f32; | |
664 | /// Returns the natural logarithm of an `f64`. | |
665 | pub fn logf64(x: f64) -> f64; | |
666 | ||
667 | /// Returns the base 10 logarithm of an `f32`. | |
668 | pub fn log10f32(x: f32) -> f32; | |
669 | /// Returns the base 10 logarithm of an `f64`. | |
670 | pub fn log10f64(x: f64) -> f64; | |
671 | ||
672 | /// Returns the base 2 logarithm of an `f32`. | |
673 | pub fn log2f32(x: f32) -> f32; | |
674 | /// Returns the base 2 logarithm of an `f64`. | |
675 | pub fn log2f64(x: f64) -> f64; | |
676 | ||
677 | /// Returns `a * b + c` for `f32` values. | |
678 | pub fn fmaf32(a: f32, b: f32, c: f32) -> f32; | |
679 | /// Returns `a * b + c` for `f64` values. | |
680 | pub fn fmaf64(a: f64, b: f64, c: f64) -> f64; | |
681 | ||
682 | /// Returns the absolute value of an `f32`. | |
683 | pub fn fabsf32(x: f32) -> f32; | |
684 | /// Returns the absolute value of an `f64`. | |
685 | pub fn fabsf64(x: f64) -> f64; | |
686 | ||
687 | /// Copies the sign from `y` to `x` for `f32` values. | |
688 | pub fn copysignf32(x: f32, y: f32) -> f32; | |
689 | /// Copies the sign from `y` to `x` for `f64` values. | |
690 | pub fn copysignf64(x: f64, y: f64) -> f64; | |
691 | ||
692 | /// Returns the largest integer less than or equal to an `f32`. | |
693 | pub fn floorf32(x: f32) -> f32; | |
694 | /// Returns the largest integer less than or equal to an `f64`. | |
695 | pub fn floorf64(x: f64) -> f64; | |
696 | ||
697 | /// Returns the smallest integer greater than or equal to an `f32`. | |
698 | pub fn ceilf32(x: f32) -> f32; | |
699 | /// Returns the smallest integer greater than or equal to an `f64`. | |
700 | pub fn ceilf64(x: f64) -> f64; | |
701 | ||
702 | /// Returns the integer part of an `f32`. | |
703 | pub fn truncf32(x: f32) -> f32; | |
704 | /// Returns the integer part of an `f64`. | |
705 | pub fn truncf64(x: f64) -> f64; | |
706 | ||
707 | /// Returns the nearest integer to an `f32`. May raise an inexact floating-point exception | |
708 | /// if the argument is not an integer. | |
709 | pub fn rintf32(x: f32) -> f32; | |
710 | /// Returns the nearest integer to an `f64`. May raise an inexact floating-point exception | |
711 | /// if the argument is not an integer. | |
712 | pub fn rintf64(x: f64) -> f64; | |
713 | ||
714 | /// Returns the nearest integer to an `f32`. | |
715 | pub fn nearbyintf32(x: f32) -> f32; | |
716 | /// Returns the nearest integer to an `f64`. | |
717 | pub fn nearbyintf64(x: f64) -> f64; | |
718 | ||
719 | /// Returns the nearest integer to an `f32`. Rounds half-way cases away from zero. | |
720 | pub fn roundf32(x: f32) -> f32; | |
721 | /// Returns the nearest integer to an `f64`. Rounds half-way cases away from zero. | |
722 | pub fn roundf64(x: f64) -> f64; | |
723 | ||
54a0048b SL |
724 | /// Float addition that allows optimizations based on algebraic rules. |
725 | /// May assume inputs are finite. | |
54a0048b SL |
726 | pub fn fadd_fast<T>(a: T, b: T) -> T; |
727 | ||
728 | /// Float subtraction that allows optimizations based on algebraic rules. | |
729 | /// May assume inputs are finite. | |
54a0048b SL |
730 | pub fn fsub_fast<T>(a: T, b: T) -> T; |
731 | ||
732 | /// Float multiplication that allows optimizations based on algebraic rules. | |
733 | /// May assume inputs are finite. | |
54a0048b SL |
734 | pub fn fmul_fast<T>(a: T, b: T) -> T; |
735 | ||
736 | /// Float division that allows optimizations based on algebraic rules. | |
737 | /// May assume inputs are finite. | |
54a0048b SL |
738 | pub fn fdiv_fast<T>(a: T, b: T) -> T; |
739 | ||
740 | /// Float remainder that allows optimizations based on algebraic rules. | |
741 | /// May assume inputs are finite. | |
54a0048b SL |
742 | pub fn frem_fast<T>(a: T, b: T) -> T; |
743 | ||
744 | ||
92a42be0 | 745 | /// Returns the number of bits set in an integer type `T` |
92a42be0 | 746 | pub fn ctpop<T>(x: T) -> T; |
1a4d82fc | 747 | |
92a42be0 | 748 | /// Returns the number of leading bits unset in an integer type `T` |
92a42be0 | 749 | pub fn ctlz<T>(x: T) -> T; |
1a4d82fc | 750 | |
92a42be0 | 751 | /// Returns the number of trailing bits unset in an integer type `T` |
92a42be0 | 752 | pub fn cttz<T>(x: T) -> T; |
1a4d82fc | 753 | |
92a42be0 | 754 | /// Reverses the bytes in an integer type `T`. |
92a42be0 | 755 | pub fn bswap<T>(x: T) -> T; |
1a4d82fc | 756 | |
92a42be0 | 757 | /// Performs checked integer addition. |
92a42be0 SL |
758 | pub fn add_with_overflow<T>(x: T, y: T) -> (T, bool); |
759 | ||
92a42be0 | 760 | /// Performs checked integer subtraction |
92a42be0 SL |
761 | pub fn sub_with_overflow<T>(x: T, y: T) -> (T, bool); |
762 | ||
92a42be0 | 763 | /// Performs checked integer multiplication |
92a42be0 SL |
764 | pub fn mul_with_overflow<T>(x: T, y: T) -> (T, bool); |
765 | ||
766 | /// Performs an unchecked division, resulting in undefined behavior | |
767 | /// where y = 0 or x = `T::min_value()` and y = -1 | |
92a42be0 SL |
768 | pub fn unchecked_div<T>(x: T, y: T) -> T; |
769 | /// Returns the remainder of an unchecked division, resulting in | |
770 | /// undefined behavior where y = 0 or x = `T::min_value()` and y = -1 | |
92a42be0 SL |
771 | pub fn unchecked_rem<T>(x: T, y: T) -> T; |
772 | ||
773 | /// Returns (a + b) mod 2^N, where N is the width of T in bits. | |
c34b1796 | 774 | pub fn overflowing_add<T>(a: T, b: T) -> T; |
92a42be0 | 775 | /// Returns (a - b) mod 2^N, where N is the width of T in bits. |
c34b1796 | 776 | pub fn overflowing_sub<T>(a: T, b: T) -> T; |
92a42be0 | 777 | /// Returns (a * b) mod 2^N, where N is the width of T in bits. |
c34b1796 | 778 | pub fn overflowing_mul<T>(a: T, b: T) -> T; |
9346a6ac | 779 | |
62682a34 SL |
780 | /// Returns the value of the discriminant for the variant in 'v', |
781 | /// cast to a `u64`; if `T` has no discriminant, returns 0. | |
782 | pub fn discriminant_value<T>(v: &T) -> u64; | |
c1a9b12d SL |
783 | |
784 | /// Rust's "try catch" construct which invokes the function pointer `f` with | |
7453a54e SL |
785 | /// the data pointer `data`. |
786 | /// | |
787 | /// The third pointer is a target-specific data pointer which is filled in | |
788 | /// with the specifics of the exception that occurred. For examples on Unix | |
789 | /// platforms this is a `*mut *mut T` which is filled in by the compiler and | |
790 | /// on MSVC it's `*mut [usize; 2]`. For more information see the compiler's | |
791 | /// source as well as std's catch implementation. | |
792 | pub fn try(f: fn(*mut u8), data: *mut u8, local_ptr: *mut u8) -> i32; | |
d9579d0f | 793 | } |