1 use core::cell::RefCell;
4 use std::fmt::{Debug, Display};
7 fn test_const_from_raw_parts() {
8 const SLICE: &[u8] = &[1, 2, 3, 4];
9 const FROM_RAW: &[u8] = unsafe { &*slice_from_raw_parts(SLICE.as_ptr(), SLICE.len()) };
10 assert_eq!(SLICE, FROM_RAW);
12 let slice = &[1, 2, 3, 4, 5];
13 let from_raw = unsafe { &*slice_from_raw_parts(slice.as_ptr(), 2) };
14 assert_eq!(&slice[..2], from_raw);
24 let mut p = Pair { fst: 10, snd: 20 };
25 let pptr: *mut Pair = &mut p;
26 let iptr: *mut isize = pptr as *mut isize;
27 assert_eq!(*iptr, 10);
29 assert_eq!(*iptr, 30);
30 assert_eq!(p.fst, 30);
32 *pptr = Pair { fst: 50, snd: 60 };
33 assert_eq!(*iptr, 50);
34 assert_eq!(p.fst, 50);
35 assert_eq!(p.snd, 60);
37 let v0 = vec![32000u16, 32001u16, 32002u16];
38 let mut v1 = vec![0u16, 0u16, 0u16];
40 copy(v0.as_ptr().offset(1), v1.as_mut_ptr().offset(1), 1);
41 assert!((v1[0] == 0u16 && v1[1] == 32001u16 && v1[2] == 0u16));
42 copy(v0.as_ptr().offset(2), v1.as_mut_ptr(), 1);
43 assert!((v1[0] == 32002u16 && v1[1] == 32001u16 && v1[2] == 0u16));
44 copy(v0.as_ptr(), v1.as_mut_ptr().offset(2), 1);
45 assert!((v1[0] == 32002u16 && v1[1] == 32001u16 && v1[2] == 32000u16));
51 let p: *const isize = null();
54 let q = p.wrapping_offset(1);
55 assert!(!q.is_null());
57 let mp: *mut isize = null_mut();
58 assert!(mp.is_null());
60 let mq = mp.wrapping_offset(1);
61 assert!(!mq.is_null());
63 // Pointers to unsized types -- slices
64 let s: &mut [u8] = &mut [1, 2, 3];
65 let cs: *const [u8] = s;
66 assert!(!cs.is_null());
68 let ms: *mut [u8] = s;
69 assert!(!ms.is_null());
71 let cz: *const [u8] = &[];
72 assert!(!cz.is_null());
74 let mz: *mut [u8] = &mut [];
75 assert!(!mz.is_null());
77 let ncs: *const [u8] = null::<[u8; 3]>();
78 assert!(ncs.is_null());
80 let nms: *mut [u8] = null_mut::<[u8; 3]>();
81 assert!(nms.is_null());
83 // Pointers to unsized types -- trait objects
84 let ci: *const dyn ToString = &3;
85 assert!(!ci.is_null());
87 let mi: *mut dyn ToString = &mut 3;
88 assert!(!mi.is_null());
90 let nci: *const dyn ToString = null::<isize>();
91 assert!(nci.is_null());
93 let nmi: *mut dyn ToString = null_mut::<isize>();
94 assert!(nmi.is_null());
100 let p: *const isize = null();
101 assert_eq!(p.as_ref(), None);
103 let q: *const isize = &2;
104 assert_eq!(q.as_ref().unwrap(), &2);
106 let p: *mut isize = null_mut();
107 assert_eq!(p.as_ref(), None);
109 let q: *mut isize = &mut 2;
110 assert_eq!(q.as_ref().unwrap(), &2);
112 // Lifetime inference
115 let p = &u as *const isize;
116 assert_eq!(p.as_ref().unwrap(), &2);
119 // Pointers to unsized types -- slices
120 let s: &mut [u8] = &mut [1, 2, 3];
121 let cs: *const [u8] = s;
122 assert_eq!(cs.as_ref(), Some(&*s));
124 let ms: *mut [u8] = s;
125 assert_eq!(ms.as_ref(), Some(&*s));
127 let cz: *const [u8] = &[];
128 assert_eq!(cz.as_ref(), Some(&[][..]));
130 let mz: *mut [u8] = &mut [];
131 assert_eq!(mz.as_ref(), Some(&[][..]));
133 let ncs: *const [u8] = null::<[u8; 3]>();
134 assert_eq!(ncs.as_ref(), None);
136 let nms: *mut [u8] = null_mut::<[u8; 3]>();
137 assert_eq!(nms.as_ref(), None);
139 // Pointers to unsized types -- trait objects
140 let ci: *const dyn ToString = &3;
141 assert!(ci.as_ref().is_some());
143 let mi: *mut dyn ToString = &mut 3;
144 assert!(mi.as_ref().is_some());
146 let nci: *const dyn ToString = null::<isize>();
147 assert!(nci.as_ref().is_none());
149 let nmi: *mut dyn ToString = null_mut::<isize>();
150 assert!(nmi.as_ref().is_none());
157 let p: *mut isize = null_mut();
158 assert!(p.as_mut() == None);
160 let q: *mut isize = &mut 2;
161 assert!(q.as_mut().unwrap() == &mut 2);
163 // Lifetime inference
166 let p = &mut u as *mut isize;
167 assert!(p.as_mut().unwrap() == &mut 2);
170 // Pointers to unsized types -- slices
171 let s: &mut [u8] = &mut [1, 2, 3];
172 let ms: *mut [u8] = s;
173 assert_eq!(ms.as_mut(), Some(&mut [1, 2, 3][..]));
175 let mz: *mut [u8] = &mut [];
176 assert_eq!(mz.as_mut(), Some(&mut [][..]));
178 let nms: *mut [u8] = null_mut::<[u8; 3]>();
179 assert_eq!(nms.as_mut(), None);
181 // Pointers to unsized types -- trait objects
182 let mi: *mut dyn ToString = &mut 3;
183 assert!(mi.as_mut().is_some());
185 let nmi: *mut dyn ToString = null_mut::<isize>();
186 assert!(nmi.as_mut().is_none());
191 fn test_ptr_addition() {
193 let xs = vec![5; 16];
194 let mut ptr = xs.as_ptr();
195 let end = ptr.offset(16);
203 let mut m_ptr = xs_mut.as_mut_ptr();
204 let m_end = m_ptr.offset(16);
206 while m_ptr < m_end {
208 m_ptr = m_ptr.offset(1);
211 assert!(xs_mut == vec![10; 16]);
216 fn test_ptr_subtraction() {
218 let xs = vec![0, 1, 2, 3, 4, 5, 6, 7, 8, 9];
220 let ptr = xs.as_ptr();
223 assert_eq!(*(ptr.offset(idx as isize)), idx as isize);
228 let m_start = xs_mut.as_mut_ptr();
229 let mut m_ptr = m_start.offset(9);
233 if m_ptr == m_start {
236 m_ptr = m_ptr.offset(-1);
239 assert_eq!(xs_mut, [0, 2, 4, 6, 8, 10, 12, 14, 16, 18]);
244 fn test_set_memory() {
245 let mut xs = [0u8; 20];
246 let ptr = xs.as_mut_ptr();
248 write_bytes(ptr, 5u8, xs.len());
250 assert!(xs == [5u8; 20]);
254 fn test_unsized_nonnull() {
255 let xs: &[i32] = &[1, 2, 3];
256 let ptr = unsafe { NonNull::new_unchecked(xs as *const [i32] as *mut [i32]) };
257 let ys = unsafe { ptr.as_ref() };
258 let zs: &[i32] = &[1, 2, 3];
264 // Have a symbol for the test below. It doesn’t need to be an actual variadic function, match the
265 // ABI, or even point to an actual executable code, because the function itself is never invoked.
267 pub fn test_variadic_fnptr() {
268 use core::hash::{Hash, SipHasher};
270 fn test_variadic_fnptr(_: u64, ...) -> f64;
272 let p: unsafe extern "C" fn(u64, ...) -> f64 = test_variadic_fnptr;
276 let mut s = SipHasher::new();
277 assert_eq!(p.hash(&mut s), q.hash(&mut s));
281 fn write_unaligned_drop() {
283 static DROPS: RefCell<Vec<u32>> = RefCell::new(Vec::new());
288 impl Drop for Dropper {
290 DROPS.with(|d| d.borrow_mut().push(self.0));
296 let mut t = Dropper(1);
298 write_unaligned(&mut t, c);
301 DROPS.with(|d| assert_eq!(*d.borrow(), [0]));
305 fn align_offset_zst() {
306 // For pointers of stride = 0, the pointer is already aligned or it cannot be aligned at
307 // all, because no amount of elements will align the pointer.
310 assert_eq!((p as *const ()).align_offset(p), 0);
312 assert_eq!(((p + 1) as *const ()).align_offset(p), !0);
314 p = (p + 1).next_power_of_two();
319 fn align_offset_stride1() {
320 // For pointers of stride = 1, the pointer can always be aligned. The offset is equal to
324 for ptr in 1..2 * align {
325 let expected = ptr % align;
326 let offset = if expected == 0 { 0 } else { align - expected };
328 (ptr as *const u8).align_offset(align),
330 "ptr = {}, align = {}, size = 1",
335 align = (align + 1).next_power_of_two();
340 fn align_offset_weird_strides() {
349 struct A7(u32, u16, u8);
353 struct A9(u32, u32, u8);
355 struct A10(u32, u32, u16);
357 unsafe fn test_weird_stride<T>(ptr: *const T, align: usize) -> bool {
358 let numptr = ptr as usize;
359 let mut expected = usize::MAX;
360 // Naive but definitely correct way to find the *first* aligned element of stride::<T>.
362 if (numptr + el * ::std::mem::size_of::<T>()) % align == 0 {
367 let got = ptr.align_offset(align);
370 "aligning {:p} (with stride of {}) to {}, expected {}, got {}",
372 ::std::mem::size_of::<T>(),
382 // For pointers of stride != 1, we verify the algorithm against the naivest possible
387 let limit = if cfg!(miri) { 32 } else { 1024 };
388 while align < limit {
389 for ptr in 1usize..4 * align {
391 x |= test_weird_stride::<A3>(ptr as *const A3, align);
392 x |= test_weird_stride::<A4>(ptr as *const A4, align);
393 x |= test_weird_stride::<A5>(ptr as *const A5, align);
394 x |= test_weird_stride::<A6>(ptr as *const A6, align);
395 x |= test_weird_stride::<A7>(ptr as *const A7, align);
396 x |= test_weird_stride::<A8>(ptr as *const A8, align);
397 x |= test_weird_stride::<A9>(ptr as *const A9, align);
398 x |= test_weird_stride::<A10>(ptr as *const A10, align);
401 align = (align + 1).next_power_of_two();
409 let ptr1: *mut i32 = &mut a[1];
410 let ptr2: *mut i32 = &mut a[3];
412 assert_eq!(ptr2.offset_from(ptr1), 2);
413 assert_eq!(ptr1.offset_from(ptr2), -2);
414 assert_eq!(ptr1.offset(2), ptr2);
415 assert_eq!(ptr2.offset(-2), ptr1);
422 struct Pair<A, B: ?Sized>(A, B);
426 let () = metadata(&());
427 let () = metadata(&Unit);
428 let () = metadata(&4_u32);
429 let () = metadata(&String::new());
430 let () = metadata(&Some(4_u32));
431 let () = metadata(&ptr_metadata);
432 let () = metadata(&|| {});
433 let () = metadata(&[4, 7]);
434 let () = metadata(&(4, String::new()));
435 let () = metadata(&Pair(4, String::new()));
436 let () = metadata(0 as *const Extern);
437 let () = metadata(0 as *const <&u32 as std::ops::Deref>::Target);
439 assert_eq!(metadata("foo"), 3_usize);
440 assert_eq!(metadata(&[4, 7][..]), 2_usize);
442 let dst_tuple: &(bool, [u8]) = &(true, [0x66, 0x6F, 0x6F]);
443 let dst_struct: &Pair<bool, [u8]> = &Pair(true, [0x66, 0x6F, 0x6F]);
444 assert_eq!(metadata(dst_tuple), 3_usize);
445 assert_eq!(metadata(dst_struct), 3_usize);
447 let dst_tuple: &(bool, str) = std::mem::transmute(dst_tuple);
448 let dst_struct: &Pair<bool, str> = std::mem::transmute(dst_struct);
449 assert_eq!(&dst_tuple.1, "foo");
450 assert_eq!(&dst_struct.1, "foo");
451 assert_eq!(metadata(dst_tuple), 3_usize);
452 assert_eq!(metadata(dst_struct), 3_usize);
455 let vtable_1: DynMetadata<dyn Debug> = metadata(&4_u16 as &dyn Debug);
456 let vtable_2: DynMetadata<dyn Display> = metadata(&4_u16 as &dyn Display);
457 let vtable_3: DynMetadata<dyn Display> = metadata(&4_u32 as &dyn Display);
458 let vtable_4: DynMetadata<dyn Display> = metadata(&(true, 7_u32) as &(bool, dyn Display));
459 let vtable_5: DynMetadata<dyn Display> =
460 metadata(&Pair(true, 7_u32) as &Pair<bool, dyn Display>);
462 let address_1: usize = std::mem::transmute(vtable_1);
463 let address_2: usize = std::mem::transmute(vtable_2);
464 let address_3: usize = std::mem::transmute(vtable_3);
465 let address_4: usize = std::mem::transmute(vtable_4);
466 let address_5: usize = std::mem::transmute(vtable_5);
467 // Different trait => different vtable pointer
468 assert_ne!(address_1, address_2);
469 // Different erased type => different vtable pointer
470 assert_ne!(address_2, address_3);
471 // Same erased type and same trait => same vtable pointer
472 assert_eq!(address_3, address_4);
473 assert_eq!(address_3, address_5);
478 fn ptr_metadata_bounds() {
479 fn metadata_eq_method_address<T: ?Sized>() -> usize {
480 // The `Metadata` associated type has an `Ord` bound, so this is valid:
481 <<T as Pointee>::Metadata as PartialEq>::eq as usize
483 // "Synthetic" trait impls generated by the compiler like those of `Pointee`
484 // are not checked for bounds of associated type.
485 // So with a buggy libcore we could have both:
486 // * `<dyn Display as Pointee>::Metadata == DynMetadata`
487 // * `DynMetadata: !PartialEq`
488 // … and cause an ICE here:
489 metadata_eq_method_address::<dyn Display>();
491 // For this reason, let’s check here that bounds are satisfied:
493 let _ = static_assert_expected_bounds_for_metadata::<()>;
494 let _ = static_assert_expected_bounds_for_metadata::<usize>;
495 let _ = static_assert_expected_bounds_for_metadata::<DynMetadata<dyn Display>>;
496 fn _static_assert_associated_type<T: ?Sized>() {
497 let _ = static_assert_expected_bounds_for_metadata::<<T as Pointee>::Metadata>;
500 fn static_assert_expected_bounds_for_metadata<Meta>()
502 // Keep this in sync with the associated type in `library/core/src/ptr/metadata.rs`
503 Meta: Copy + Send + Sync + Ord + std::hash::Hash + Unpin,
512 struct Something([u8; 47]);
514 let value = Something([0; 47]);
515 let trait_object: &dyn Debug = &value;
516 let meta = metadata(trait_object);
518 assert_eq!(meta.size_of(), 64);
519 assert_eq!(meta.size_of(), std::mem::size_of::<Something>());
520 assert_eq!(meta.align_of(), 32);
521 assert_eq!(meta.align_of(), std::mem::align_of::<Something>());
522 assert_eq!(meta.layout(), std::alloc::Layout::new::<Something>());
524 assert!(format!("{:?}", meta).starts_with("DynMetadata(0x"));
528 fn from_raw_parts() {
529 let mut value = 5_u32;
530 let address = &mut value as *mut _ as *mut ();
531 let trait_object: &dyn Display = &mut value;
532 let vtable = metadata(trait_object);
533 let trait_object = NonNull::from(trait_object);
535 assert_eq!(ptr::from_raw_parts(address, vtable), trait_object.as_ptr());
536 assert_eq!(ptr::from_raw_parts_mut(address, vtable), trait_object.as_ptr());
537 assert_eq!(NonNull::from_raw_parts(NonNull::new(address).unwrap(), vtable), trait_object);
539 let mut array = [5_u32, 5, 5, 5, 5];
540 let address = &mut array as *mut _ as *mut ();
541 let array_ptr = NonNull::from(&mut array);
542 let slice_ptr = NonNull::from(&mut array[..]);
544 assert_eq!(ptr::from_raw_parts(address, ()), array_ptr.as_ptr());
545 assert_eq!(ptr::from_raw_parts_mut(address, ()), array_ptr.as_ptr());
546 assert_eq!(NonNull::from_raw_parts(NonNull::new(address).unwrap(), ()), array_ptr);
548 assert_eq!(ptr::from_raw_parts(address, 5), slice_ptr.as_ptr());
549 assert_eq!(ptr::from_raw_parts_mut(address, 5), slice_ptr.as_ptr());
550 assert_eq!(NonNull::from_raw_parts(NonNull::new(address).unwrap(), 5), slice_ptr);
555 let foo = ThinBox::<dyn Display>::new(4);
556 assert_eq!(foo.to_string(), "4");
558 let bar = ThinBox::<dyn Display>::new(7);
559 assert_eq!(bar.to_string(), "7");
561 // A slightly more interesting library that could be built on top of metadata APIs.
563 // * It could be generalized to any `T: ?Sized` (not just trait object)
564 // if `{size,align}_of_for_meta<T: ?Sized>(T::Metadata)` are added.
565 // * Constructing a `ThinBox` without consuming and deallocating a `Box`
566 // requires either the unstable `Unsize` marker trait,
567 // or the unstable `unsized_locals` language feature,
568 // or taking `&dyn T` and restricting to `T: Copy`.
571 use std::marker::PhantomData;
575 T: ?Sized + Pointee<Metadata = DynMetadata<T>>,
577 ptr: NonNull<DynMetadata<T>>,
578 phantom: PhantomData<T>,
583 T: ?Sized + Pointee<Metadata = DynMetadata<T>>,
585 pub fn new<Value: std::marker::Unsize<T>>(value: Value) -> Self {
586 let unsized_: &T = &value;
587 let meta = metadata(unsized_);
588 let meta_layout = Layout::for_value(&meta);
589 let value_layout = Layout::for_value(&value);
590 let (layout, offset) = meta_layout.extend(value_layout).unwrap();
591 // `DynMetadata` is pointer-sized:
592 assert!(layout.size() > 0);
593 // If `ThinBox<T>` is generalized to any `T: ?Sized`,
594 // handle ZSTs with a dangling pointer without going through `alloc()`,
595 // like `Box<T>` does.
597 let ptr = NonNull::new(alloc(layout))
598 .unwrap_or_else(|| handle_alloc_error(layout))
599 .cast::<DynMetadata<T>>();
600 ptr.as_ptr().write(meta);
601 ptr.cast::<u8>().as_ptr().add(offset).cast::<Value>().write(value);
602 Self { ptr, phantom: PhantomData }
606 fn meta(&self) -> DynMetadata<T> {
607 unsafe { *self.ptr.as_ref() }
610 fn layout(&self) -> (Layout, usize) {
611 let meta = self.meta();
612 Layout::for_value(&meta).extend(meta.layout()).unwrap()
615 fn value_ptr(&self) -> *const T {
616 let (_, offset) = self.layout();
617 let data_ptr = unsafe { self.ptr.cast::<u8>().as_ptr().add(offset) };
618 ptr::from_raw_parts(data_ptr.cast(), self.meta())
621 fn value_mut_ptr(&mut self) -> *mut T {
622 let (_, offset) = self.layout();
623 // FIXME: can this line be shared with the same in `value_ptr()`
624 // without upsetting Stacked Borrows?
625 let data_ptr = unsafe { self.ptr.cast::<u8>().as_ptr().add(offset) };
626 from_raw_parts_mut(data_ptr.cast(), self.meta())
630 impl<T> std::ops::Deref for ThinBox<T>
632 T: ?Sized + Pointee<Metadata = DynMetadata<T>>,
636 fn deref(&self) -> &T {
637 unsafe { &*self.value_ptr() }
641 impl<T> std::ops::DerefMut for ThinBox<T>
643 T: ?Sized + Pointee<Metadata = DynMetadata<T>>,
645 fn deref_mut(&mut self) -> &mut T {
646 unsafe { &mut *self.value_mut_ptr() }
650 impl<T> std::ops::Drop for ThinBox<T>
652 T: ?Sized + Pointee<Metadata = DynMetadata<T>>,
655 let (layout, _) = self.layout();
657 drop_in_place::<T>(&mut **self);
658 dealloc(self.ptr.cast().as_ptr(), layout);