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_set_memory_const() {
255 const XS: [u8; 20] = {
256 let mut xs = [0u8; 20];
257 let ptr = xs.as_mut_ptr();
259 ptr.write_bytes(5u8, xs.len());
264 assert!(XS == [5u8; 20]);
268 fn test_unsized_nonnull() {
269 let xs: &[i32] = &[1, 2, 3];
270 let ptr = unsafe { NonNull::new_unchecked(xs as *const [i32] as *mut [i32]) };
271 let ys = unsafe { ptr.as_ref() };
272 let zs: &[i32] = &[1, 2, 3];
277 fn test_const_nonnull_new() {
279 assert!(NonNull::new(core::ptr::null_mut::<()>()).is_none());
281 let value = &mut 0u32;
282 let mut ptr = NonNull::new(value).unwrap();
283 unsafe { *ptr.as_mut() = 42 };
285 let reference = unsafe { &*ptr.as_ref() };
286 assert!(*reference == *value);
287 assert!(*reference == 42);
293 // Have a symbol for the test below. It doesn’t need to be an actual variadic function, match the
294 // ABI, or even point to an actual executable code, because the function itself is never invoked.
296 pub fn test_variadic_fnptr() {
297 use core::hash::{Hash, SipHasher};
299 fn test_variadic_fnptr(_: u64, ...) -> f64;
301 let p: unsafe extern "C" fn(u64, ...) -> f64 = test_variadic_fnptr;
305 let mut s = SipHasher::new();
306 assert_eq!(p.hash(&mut s), q.hash(&mut s));
310 fn write_unaligned_drop() {
312 static DROPS: RefCell<Vec<u32>> = RefCell::new(Vec::new());
317 impl Drop for Dropper {
319 DROPS.with(|d| d.borrow_mut().push(self.0));
325 let mut t = Dropper(1);
327 write_unaligned(&mut t, c);
330 DROPS.with(|d| assert_eq!(*d.borrow(), [0]));
334 fn align_offset_zst() {
335 // For pointers of stride = 0, the pointer is already aligned or it cannot be aligned at
336 // all, because no amount of elements will align the pointer.
339 assert_eq!((p as *const ()).align_offset(p), 0);
341 assert_eq!(((p + 1) as *const ()).align_offset(p), !0);
343 p = (p + 1).next_power_of_two();
348 fn align_offset_stride1() {
349 // For pointers of stride = 1, the pointer can always be aligned. The offset is equal to
353 for ptr in 1..2 * align {
354 let expected = ptr % align;
355 let offset = if expected == 0 { 0 } else { align - expected };
357 (ptr as *const u8).align_offset(align),
359 "ptr = {}, align = {}, size = 1",
364 align = (align + 1).next_power_of_two();
369 fn align_offset_weird_strides() {
378 struct A7(u32, u16, u8);
382 struct A9(u32, u32, u8);
384 struct A10(u32, u32, u16);
386 unsafe fn test_weird_stride<T>(ptr: *const T, align: usize) -> bool {
387 let numptr = ptr as usize;
388 let mut expected = usize::MAX;
389 // Naive but definitely correct way to find the *first* aligned element of stride::<T>.
391 if (numptr + el * ::std::mem::size_of::<T>()) % align == 0 {
396 let got = ptr.align_offset(align);
399 "aligning {:p} (with stride of {}) to {}, expected {}, got {}",
401 ::std::mem::size_of::<T>(),
411 // For pointers of stride != 1, we verify the algorithm against the naivest possible
416 let limit = if cfg!(miri) { 32 } else { 1024 };
417 while align < limit {
418 for ptr in 1usize..4 * align {
420 x |= test_weird_stride::<A3>(ptr as *const A3, align);
421 x |= test_weird_stride::<A4>(ptr as *const A4, align);
422 x |= test_weird_stride::<A5>(ptr as *const A5, align);
423 x |= test_weird_stride::<A6>(ptr as *const A6, align);
424 x |= test_weird_stride::<A7>(ptr as *const A7, align);
425 x |= test_weird_stride::<A8>(ptr as *const A8, align);
426 x |= test_weird_stride::<A9>(ptr as *const A9, align);
427 x |= test_weird_stride::<A10>(ptr as *const A10, align);
430 align = (align + 1).next_power_of_two();
438 let ptr1: *mut i32 = &mut a[1];
439 let ptr2: *mut i32 = &mut a[3];
441 assert_eq!(ptr2.offset_from(ptr1), 2);
442 assert_eq!(ptr1.offset_from(ptr2), -2);
443 assert_eq!(ptr1.offset(2), ptr2);
444 assert_eq!(ptr2.offset(-2), ptr1);
451 struct Pair<A, B: ?Sized>(A, B);
455 let () = metadata(&());
456 let () = metadata(&Unit);
457 let () = metadata(&4_u32);
458 let () = metadata(&String::new());
459 let () = metadata(&Some(4_u32));
460 let () = metadata(&ptr_metadata);
461 let () = metadata(&|| {});
462 let () = metadata(&[4, 7]);
463 let () = metadata(&(4, String::new()));
464 let () = metadata(&Pair(4, String::new()));
465 let () = metadata(0 as *const Extern);
466 let () = metadata(0 as *const <&u32 as std::ops::Deref>::Target);
468 assert_eq!(metadata("foo"), 3_usize);
469 assert_eq!(metadata(&[4, 7][..]), 2_usize);
471 let dst_tuple: &(bool, [u8]) = &(true, [0x66, 0x6F, 0x6F]);
472 let dst_struct: &Pair<bool, [u8]> = &Pair(true, [0x66, 0x6F, 0x6F]);
473 assert_eq!(metadata(dst_tuple), 3_usize);
474 assert_eq!(metadata(dst_struct), 3_usize);
476 let dst_tuple: &(bool, str) = std::mem::transmute(dst_tuple);
477 let dst_struct: &Pair<bool, str> = std::mem::transmute(dst_struct);
478 assert_eq!(&dst_tuple.1, "foo");
479 assert_eq!(&dst_struct.1, "foo");
480 assert_eq!(metadata(dst_tuple), 3_usize);
481 assert_eq!(metadata(dst_struct), 3_usize);
484 let vtable_1: DynMetadata<dyn Debug> = metadata(&4_u16 as &dyn Debug);
485 let vtable_2: DynMetadata<dyn Display> = metadata(&4_u16 as &dyn Display);
486 let vtable_3: DynMetadata<dyn Display> = metadata(&4_u32 as &dyn Display);
487 let vtable_4: DynMetadata<dyn Display> = metadata(&(true, 7_u32) as &(bool, dyn Display));
488 let vtable_5: DynMetadata<dyn Display> =
489 metadata(&Pair(true, 7_u32) as &Pair<bool, dyn Display>);
491 let address_1: usize = std::mem::transmute(vtable_1);
492 let address_2: usize = std::mem::transmute(vtable_2);
493 let address_3: usize = std::mem::transmute(vtable_3);
494 let address_4: usize = std::mem::transmute(vtable_4);
495 let address_5: usize = std::mem::transmute(vtable_5);
496 // Different trait => different vtable pointer
497 assert_ne!(address_1, address_2);
498 // Different erased type => different vtable pointer
499 assert_ne!(address_2, address_3);
500 // Same erased type and same trait => same vtable pointer
501 assert_eq!(address_3, address_4);
502 assert_eq!(address_3, address_5);
507 fn ptr_metadata_bounds() {
508 fn metadata_eq_method_address<T: ?Sized>() -> usize {
509 // The `Metadata` associated type has an `Ord` bound, so this is valid:
510 <<T as Pointee>::Metadata as PartialEq>::eq as usize
512 // "Synthetic" trait impls generated by the compiler like those of `Pointee`
513 // are not checked for bounds of associated type.
514 // So with a buggy libcore we could have both:
515 // * `<dyn Display as Pointee>::Metadata == DynMetadata`
516 // * `DynMetadata: !PartialEq`
517 // … and cause an ICE here:
518 metadata_eq_method_address::<dyn Display>();
520 // For this reason, let’s check here that bounds are satisfied:
522 let _ = static_assert_expected_bounds_for_metadata::<()>;
523 let _ = static_assert_expected_bounds_for_metadata::<usize>;
524 let _ = static_assert_expected_bounds_for_metadata::<DynMetadata<dyn Display>>;
525 fn _static_assert_associated_type<T: ?Sized>() {
526 let _ = static_assert_expected_bounds_for_metadata::<<T as Pointee>::Metadata>;
529 fn static_assert_expected_bounds_for_metadata<Meta>()
531 // Keep this in sync with the associated type in `library/core/src/ptr/metadata.rs`
532 Meta: Copy + Send + Sync + Ord + std::hash::Hash + Unpin,
541 struct Something([u8; 47]);
543 let value = Something([0; 47]);
544 let trait_object: &dyn Debug = &value;
545 let meta = metadata(trait_object);
547 assert_eq!(meta.size_of(), 64);
548 assert_eq!(meta.size_of(), std::mem::size_of::<Something>());
549 assert_eq!(meta.align_of(), 32);
550 assert_eq!(meta.align_of(), std::mem::align_of::<Something>());
551 assert_eq!(meta.layout(), std::alloc::Layout::new::<Something>());
553 assert!(format!("{:?}", meta).starts_with("DynMetadata(0x"));
557 fn from_raw_parts() {
558 let mut value = 5_u32;
559 let address = &mut value as *mut _ as *mut ();
560 let trait_object: &dyn Display = &mut value;
561 let vtable = metadata(trait_object);
562 let trait_object = NonNull::from(trait_object);
564 assert_eq!(ptr::from_raw_parts(address, vtable), trait_object.as_ptr());
565 assert_eq!(ptr::from_raw_parts_mut(address, vtable), trait_object.as_ptr());
566 assert_eq!(NonNull::from_raw_parts(NonNull::new(address).unwrap(), vtable), trait_object);
568 let mut array = [5_u32, 5, 5, 5, 5];
569 let address = &mut array as *mut _ as *mut ();
570 let array_ptr = NonNull::from(&mut array);
571 let slice_ptr = NonNull::from(&mut array[..]);
573 assert_eq!(ptr::from_raw_parts(address, ()), array_ptr.as_ptr());
574 assert_eq!(ptr::from_raw_parts_mut(address, ()), array_ptr.as_ptr());
575 assert_eq!(NonNull::from_raw_parts(NonNull::new(address).unwrap(), ()), array_ptr);
577 assert_eq!(ptr::from_raw_parts(address, 5), slice_ptr.as_ptr());
578 assert_eq!(ptr::from_raw_parts_mut(address, 5), slice_ptr.as_ptr());
579 assert_eq!(NonNull::from_raw_parts(NonNull::new(address).unwrap(), 5), slice_ptr);
584 let foo = ThinBox::<dyn Display>::new(4);
585 assert_eq!(foo.to_string(), "4");
587 let bar = ThinBox::<dyn Display>::new(7);
588 assert_eq!(bar.to_string(), "7");
590 // A slightly more interesting library that could be built on top of metadata APIs.
592 // * It could be generalized to any `T: ?Sized` (not just trait object)
593 // if `{size,align}_of_for_meta<T: ?Sized>(T::Metadata)` are added.
594 // * Constructing a `ThinBox` without consuming and deallocating a `Box`
595 // requires either the unstable `Unsize` marker trait,
596 // or the unstable `unsized_locals` language feature,
597 // or taking `&dyn T` and restricting to `T: Copy`.
600 use std::marker::PhantomData;
604 T: ?Sized + Pointee<Metadata = DynMetadata<T>>,
606 ptr: NonNull<DynMetadata<T>>,
607 phantom: PhantomData<T>,
612 T: ?Sized + Pointee<Metadata = DynMetadata<T>>,
614 pub fn new<Value: std::marker::Unsize<T>>(value: Value) -> Self {
615 let unsized_: &T = &value;
616 let meta = metadata(unsized_);
617 let meta_layout = Layout::for_value(&meta);
618 let value_layout = Layout::for_value(&value);
619 let (layout, offset) = meta_layout.extend(value_layout).unwrap();
620 // `DynMetadata` is pointer-sized:
621 assert!(layout.size() > 0);
622 // If `ThinBox<T>` is generalized to any `T: ?Sized`,
623 // handle ZSTs with a dangling pointer without going through `alloc()`,
624 // like `Box<T>` does.
626 let ptr = NonNull::new(alloc(layout))
627 .unwrap_or_else(|| handle_alloc_error(layout))
628 .cast::<DynMetadata<T>>();
629 ptr.as_ptr().write(meta);
630 ptr.cast::<u8>().as_ptr().add(offset).cast::<Value>().write(value);
631 Self { ptr, phantom: PhantomData }
635 fn meta(&self) -> DynMetadata<T> {
636 unsafe { *self.ptr.as_ref() }
639 fn layout(&self) -> (Layout, usize) {
640 let meta = self.meta();
641 Layout::for_value(&meta).extend(meta.layout()).unwrap()
644 fn value_ptr(&self) -> *const T {
645 let (_, offset) = self.layout();
646 let data_ptr = unsafe { self.ptr.cast::<u8>().as_ptr().add(offset) };
647 ptr::from_raw_parts(data_ptr.cast(), self.meta())
650 fn value_mut_ptr(&mut self) -> *mut T {
651 let (_, offset) = self.layout();
652 // FIXME: can this line be shared with the same in `value_ptr()`
653 // without upsetting Stacked Borrows?
654 let data_ptr = unsafe { self.ptr.cast::<u8>().as_ptr().add(offset) };
655 from_raw_parts_mut(data_ptr.cast(), self.meta())
659 impl<T> std::ops::Deref for ThinBox<T>
661 T: ?Sized + Pointee<Metadata = DynMetadata<T>>,
665 fn deref(&self) -> &T {
666 unsafe { &*self.value_ptr() }
670 impl<T> std::ops::DerefMut for ThinBox<T>
672 T: ?Sized + Pointee<Metadata = DynMetadata<T>>,
674 fn deref_mut(&mut self) -> &mut T {
675 unsafe { &mut *self.value_mut_ptr() }
679 impl<T> std::ops::Drop for ThinBox<T>
681 T: ?Sized + Pointee<Metadata = DynMetadata<T>>,
684 let (layout, _) = self.layout();
686 drop_in_place::<T>(&mut **self);
687 dealloc(self.ptr.cast().as_ptr(), layout);