use core::cell::RefCell; use core::ptr; use core::ptr::*; use std::fmt::{Debug, Display}; #[test] fn test_const_from_raw_parts() { const SLICE: &[u8] = &[1, 2, 3, 4]; const FROM_RAW: &[u8] = unsafe { &*slice_from_raw_parts(SLICE.as_ptr(), SLICE.len()) }; assert_eq!(SLICE, FROM_RAW); let slice = &[1, 2, 3, 4, 5]; let from_raw = unsafe { &*slice_from_raw_parts(slice.as_ptr(), 2) }; assert_eq!(&slice[..2], from_raw); } #[test] fn test() { unsafe { struct Pair { fst: isize, snd: isize, } let mut p = Pair { fst: 10, snd: 20 }; let pptr: *mut Pair = &mut p; let iptr: *mut isize = pptr as *mut isize; assert_eq!(*iptr, 10); *iptr = 30; assert_eq!(*iptr, 30); assert_eq!(p.fst, 30); *pptr = Pair { fst: 50, snd: 60 }; assert_eq!(*iptr, 50); assert_eq!(p.fst, 50); assert_eq!(p.snd, 60); let v0 = vec![32000u16, 32001u16, 32002u16]; let mut v1 = vec![0u16, 0u16, 0u16]; copy(v0.as_ptr().offset(1), v1.as_mut_ptr().offset(1), 1); assert!((v1[0] == 0u16 && v1[1] == 32001u16 && v1[2] == 0u16)); copy(v0.as_ptr().offset(2), v1.as_mut_ptr(), 1); assert!((v1[0] == 32002u16 && v1[1] == 32001u16 && v1[2] == 0u16)); copy(v0.as_ptr(), v1.as_mut_ptr().offset(2), 1); assert!((v1[0] == 32002u16 && v1[1] == 32001u16 && v1[2] == 32000u16)); } } #[test] fn test_is_null() { let p: *const isize = null(); assert!(p.is_null()); let q = p.wrapping_offset(1); assert!(!q.is_null()); let mp: *mut isize = null_mut(); assert!(mp.is_null()); let mq = mp.wrapping_offset(1); assert!(!mq.is_null()); // Pointers to unsized types -- slices let s: &mut [u8] = &mut [1, 2, 3]; let cs: *const [u8] = s; assert!(!cs.is_null()); let ms: *mut [u8] = s; assert!(!ms.is_null()); let cz: *const [u8] = &[]; assert!(!cz.is_null()); let mz: *mut [u8] = &mut []; assert!(!mz.is_null()); let ncs: *const [u8] = null::<[u8; 3]>(); assert!(ncs.is_null()); let nms: *mut [u8] = null_mut::<[u8; 3]>(); assert!(nms.is_null()); // Pointers to unsized types -- trait objects let ci: *const dyn ToString = &3; assert!(!ci.is_null()); let mi: *mut dyn ToString = &mut 3; assert!(!mi.is_null()); let nci: *const dyn ToString = null::(); assert!(nci.is_null()); let nmi: *mut dyn ToString = null_mut::(); assert!(nmi.is_null()); } #[test] fn test_as_ref() { unsafe { let p: *const isize = null(); assert_eq!(p.as_ref(), None); let q: *const isize = &2; assert_eq!(q.as_ref().unwrap(), &2); let p: *mut isize = null_mut(); assert_eq!(p.as_ref(), None); let q: *mut isize = &mut 2; assert_eq!(q.as_ref().unwrap(), &2); // Lifetime inference let u = 2isize; { let p = &u as *const isize; assert_eq!(p.as_ref().unwrap(), &2); } // Pointers to unsized types -- slices let s: &mut [u8] = &mut [1, 2, 3]; let cs: *const [u8] = s; assert_eq!(cs.as_ref(), Some(&*s)); let ms: *mut [u8] = s; assert_eq!(ms.as_ref(), Some(&*s)); let cz: *const [u8] = &[]; assert_eq!(cz.as_ref(), Some(&[][..])); let mz: *mut [u8] = &mut []; assert_eq!(mz.as_ref(), Some(&[][..])); let ncs: *const [u8] = null::<[u8; 3]>(); assert_eq!(ncs.as_ref(), None); let nms: *mut [u8] = null_mut::<[u8; 3]>(); assert_eq!(nms.as_ref(), None); // Pointers to unsized types -- trait objects let ci: *const dyn ToString = &3; assert!(ci.as_ref().is_some()); let mi: *mut dyn ToString = &mut 3; assert!(mi.as_ref().is_some()); let nci: *const dyn ToString = null::(); assert!(nci.as_ref().is_none()); let nmi: *mut dyn ToString = null_mut::(); assert!(nmi.as_ref().is_none()); } } #[test] fn test_as_mut() { unsafe { let p: *mut isize = null_mut(); assert!(p.as_mut() == None); let q: *mut isize = &mut 2; assert!(q.as_mut().unwrap() == &mut 2); // Lifetime inference let mut u = 2isize; { let p = &mut u as *mut isize; assert!(p.as_mut().unwrap() == &mut 2); } // Pointers to unsized types -- slices let s: &mut [u8] = &mut [1, 2, 3]; let ms: *mut [u8] = s; assert_eq!(ms.as_mut(), Some(&mut [1, 2, 3][..])); let mz: *mut [u8] = &mut []; assert_eq!(mz.as_mut(), Some(&mut [][..])); let nms: *mut [u8] = null_mut::<[u8; 3]>(); assert_eq!(nms.as_mut(), None); // Pointers to unsized types -- trait objects let mi: *mut dyn ToString = &mut 3; assert!(mi.as_mut().is_some()); let nmi: *mut dyn ToString = null_mut::(); assert!(nmi.as_mut().is_none()); } } #[test] fn test_ptr_addition() { unsafe { let xs = vec![5; 16]; let mut ptr = xs.as_ptr(); let end = ptr.offset(16); while ptr < end { assert_eq!(*ptr, 5); ptr = ptr.offset(1); } let mut xs_mut = xs; let mut m_ptr = xs_mut.as_mut_ptr(); let m_end = m_ptr.offset(16); while m_ptr < m_end { *m_ptr += 5; m_ptr = m_ptr.offset(1); } assert!(xs_mut == vec![10; 16]); } } #[test] fn test_ptr_subtraction() { unsafe { let xs = vec![0, 1, 2, 3, 4, 5, 6, 7, 8, 9]; let mut idx = 9; let ptr = xs.as_ptr(); while idx >= 0 { assert_eq!(*(ptr.offset(idx as isize)), idx as isize); idx = idx - 1; } let mut xs_mut = xs; let m_start = xs_mut.as_mut_ptr(); let mut m_ptr = m_start.offset(9); loop { *m_ptr += *m_ptr; if m_ptr == m_start { break; } m_ptr = m_ptr.offset(-1); } assert_eq!(xs_mut, [0, 2, 4, 6, 8, 10, 12, 14, 16, 18]); } } #[test] fn test_set_memory() { let mut xs = [0u8; 20]; let ptr = xs.as_mut_ptr(); unsafe { write_bytes(ptr, 5u8, xs.len()); } assert!(xs == [5u8; 20]); } #[test] fn test_unsized_nonnull() { let xs: &[i32] = &[1, 2, 3]; let ptr = unsafe { NonNull::new_unchecked(xs as *const [i32] as *mut [i32]) }; let ys = unsafe { ptr.as_ref() }; let zs: &[i32] = &[1, 2, 3]; assert!(ys == zs); } #[test] #[allow(warnings)] // Have a symbol for the test below. It doesn’t need to be an actual variadic function, match the // ABI, or even point to an actual executable code, because the function itself is never invoked. #[no_mangle] pub fn test_variadic_fnptr() { use core::hash::{Hash, SipHasher}; extern "C" { fn test_variadic_fnptr(_: u64, ...) -> f64; } let p: unsafe extern "C" fn(u64, ...) -> f64 = test_variadic_fnptr; let q = p.clone(); assert_eq!(p, q); assert!(!(p < q)); let mut s = SipHasher::new(); assert_eq!(p.hash(&mut s), q.hash(&mut s)); } #[test] fn write_unaligned_drop() { thread_local! { static DROPS: RefCell> = RefCell::new(Vec::new()); } struct Dropper(u32); impl Drop for Dropper { fn drop(&mut self) { DROPS.with(|d| d.borrow_mut().push(self.0)); } } { let c = Dropper(0); let mut t = Dropper(1); unsafe { write_unaligned(&mut t, c); } } DROPS.with(|d| assert_eq!(*d.borrow(), [0])); } #[test] fn align_offset_zst() { // For pointers of stride = 0, the pointer is already aligned or it cannot be aligned at // all, because no amount of elements will align the pointer. let mut p = 1; while p < 1024 { assert_eq!((p as *const ()).align_offset(p), 0); if p != 1 { assert_eq!(((p + 1) as *const ()).align_offset(p), !0); } p = (p + 1).next_power_of_two(); } } #[test] fn align_offset_stride1() { // For pointers of stride = 1, the pointer can always be aligned. The offset is equal to // number of bytes. let mut align = 1; while align < 1024 { for ptr in 1..2 * align { let expected = ptr % align; let offset = if expected == 0 { 0 } else { align - expected }; assert_eq!( (ptr as *const u8).align_offset(align), offset, "ptr = {}, align = {}, size = 1", ptr, align ); } align = (align + 1).next_power_of_two(); } } #[test] fn align_offset_weird_strides() { #[repr(packed)] struct A3(u16, u8); struct A4(u32); #[repr(packed)] struct A5(u32, u8); #[repr(packed)] struct A6(u32, u16); #[repr(packed)] struct A7(u32, u16, u8); #[repr(packed)] struct A8(u32, u32); #[repr(packed)] struct A9(u32, u32, u8); #[repr(packed)] struct A10(u32, u32, u16); unsafe fn test_weird_stride(ptr: *const T, align: usize) -> bool { let numptr = ptr as usize; let mut expected = usize::MAX; // Naive but definitely correct way to find the *first* aligned element of stride::. for el in 0..align { if (numptr + el * ::std::mem::size_of::()) % align == 0 { expected = el; break; } } let got = ptr.align_offset(align); if got != expected { eprintln!( "aligning {:p} (with stride of {}) to {}, expected {}, got {}", ptr, ::std::mem::size_of::(), align, expected, got ); return true; } return false; } // For pointers of stride != 1, we verify the algorithm against the naivest possible // implementation let mut align = 1; let mut x = false; // Miri is too slow let limit = if cfg!(miri) { 32 } else { 1024 }; while align < limit { for ptr in 1usize..4 * align { unsafe { x |= test_weird_stride::(ptr as *const A3, align); x |= test_weird_stride::(ptr as *const A4, align); x |= test_weird_stride::(ptr as *const A5, align); x |= test_weird_stride::(ptr as *const A6, align); x |= test_weird_stride::(ptr as *const A7, align); x |= test_weird_stride::(ptr as *const A8, align); x |= test_weird_stride::(ptr as *const A9, align); x |= test_weird_stride::(ptr as *const A10, align); } } align = (align + 1).next_power_of_two(); } assert!(!x); } #[test] fn offset_from() { let mut a = [0; 5]; let ptr1: *mut i32 = &mut a[1]; let ptr2: *mut i32 = &mut a[3]; unsafe { assert_eq!(ptr2.offset_from(ptr1), 2); assert_eq!(ptr1.offset_from(ptr2), -2); assert_eq!(ptr1.offset(2), ptr2); assert_eq!(ptr2.offset(-2), ptr1); } } #[test] fn ptr_metadata() { struct Unit; struct Pair(A, B); extern "C" { type Extern; } let () = metadata(&()); let () = metadata(&Unit); let () = metadata(&4_u32); let () = metadata(&String::new()); let () = metadata(&Some(4_u32)); let () = metadata(&ptr_metadata); let () = metadata(&|| {}); let () = metadata(&[4, 7]); let () = metadata(&(4, String::new())); let () = metadata(&Pair(4, String::new())); let () = metadata(0 as *const Extern); let () = metadata(0 as *const <&u32 as std::ops::Deref>::Target); assert_eq!(metadata("foo"), 3_usize); assert_eq!(metadata(&[4, 7][..]), 2_usize); let dst_tuple: &(bool, [u8]) = &(true, [0x66, 0x6F, 0x6F]); let dst_struct: &Pair = &Pair(true, [0x66, 0x6F, 0x6F]); assert_eq!(metadata(dst_tuple), 3_usize); assert_eq!(metadata(dst_struct), 3_usize); unsafe { let dst_tuple: &(bool, str) = std::mem::transmute(dst_tuple); let dst_struct: &Pair = std::mem::transmute(dst_struct); assert_eq!(&dst_tuple.1, "foo"); assert_eq!(&dst_struct.1, "foo"); assert_eq!(metadata(dst_tuple), 3_usize); assert_eq!(metadata(dst_struct), 3_usize); } let vtable_1: DynMetadata = metadata(&4_u16 as &dyn Debug); let vtable_2: DynMetadata = metadata(&4_u16 as &dyn Display); let vtable_3: DynMetadata = metadata(&4_u32 as &dyn Display); let vtable_4: DynMetadata = metadata(&(true, 7_u32) as &(bool, dyn Display)); let vtable_5: DynMetadata = metadata(&Pair(true, 7_u32) as &Pair); unsafe { let address_1: usize = std::mem::transmute(vtable_1); let address_2: usize = std::mem::transmute(vtable_2); let address_3: usize = std::mem::transmute(vtable_3); let address_4: usize = std::mem::transmute(vtable_4); let address_5: usize = std::mem::transmute(vtable_5); // Different trait => different vtable pointer assert_ne!(address_1, address_2); // Different erased type => different vtable pointer assert_ne!(address_2, address_3); // Same erased type and same trait => same vtable pointer assert_eq!(address_3, address_4); assert_eq!(address_3, address_5); } } #[test] fn ptr_metadata_bounds() { fn metadata_eq_method_address() -> usize { // The `Metadata` associated type has an `Ord` bound, so this is valid: <::Metadata as PartialEq>::eq as usize } // "Synthetic" trait impls generated by the compiler like those of `Pointee` // are not checked for bounds of associated type. // So with a buggy libcore we could have both: // * `::Metadata == DynMetadata` // * `DynMetadata: !PartialEq` // … and cause an ICE here: metadata_eq_method_address::(); // For this reason, let’s check here that bounds are satisfied: let _ = static_assert_expected_bounds_for_metadata::<()>; let _ = static_assert_expected_bounds_for_metadata::; let _ = static_assert_expected_bounds_for_metadata::>; fn _static_assert_associated_type() { let _ = static_assert_expected_bounds_for_metadata::<::Metadata>; } fn static_assert_expected_bounds_for_metadata() where // Keep this in sync with the associated type in `library/core/src/ptr/metadata.rs` Meta: Copy + Send + Sync + Ord + std::hash::Hash + Unpin, { } } #[test] fn dyn_metadata() { #[derive(Debug)] #[repr(align(32))] struct Something([u8; 47]); let value = Something([0; 47]); let trait_object: &dyn Debug = &value; let meta = metadata(trait_object); assert_eq!(meta.size_of(), 64); assert_eq!(meta.size_of(), std::mem::size_of::()); assert_eq!(meta.align_of(), 32); assert_eq!(meta.align_of(), std::mem::align_of::()); assert_eq!(meta.layout(), std::alloc::Layout::new::()); assert!(format!("{:?}", meta).starts_with("DynMetadata(0x")); } #[test] fn from_raw_parts() { let mut value = 5_u32; let address = &mut value as *mut _ as *mut (); let trait_object: &dyn Display = &mut value; let vtable = metadata(trait_object); let trait_object = NonNull::from(trait_object); assert_eq!(ptr::from_raw_parts(address, vtable), trait_object.as_ptr()); assert_eq!(ptr::from_raw_parts_mut(address, vtable), trait_object.as_ptr()); assert_eq!(NonNull::from_raw_parts(NonNull::new(address).unwrap(), vtable), trait_object); let mut array = [5_u32, 5, 5, 5, 5]; let address = &mut array as *mut _ as *mut (); let array_ptr = NonNull::from(&mut array); let slice_ptr = NonNull::from(&mut array[..]); assert_eq!(ptr::from_raw_parts(address, ()), array_ptr.as_ptr()); assert_eq!(ptr::from_raw_parts_mut(address, ()), array_ptr.as_ptr()); assert_eq!(NonNull::from_raw_parts(NonNull::new(address).unwrap(), ()), array_ptr); assert_eq!(ptr::from_raw_parts(address, 5), slice_ptr.as_ptr()); assert_eq!(ptr::from_raw_parts_mut(address, 5), slice_ptr.as_ptr()); assert_eq!(NonNull::from_raw_parts(NonNull::new(address).unwrap(), 5), slice_ptr); } #[test] fn thin_box() { let foo = ThinBox::::new(4); assert_eq!(foo.to_string(), "4"); drop(foo); let bar = ThinBox::::new(7); assert_eq!(bar.to_string(), "7"); // A slightly more interesting library that could be built on top of metadata APIs. // // * It could be generalized to any `T: ?Sized` (not just trait object) // if `{size,align}_of_for_meta(T::Metadata)` are added. // * Constructing a `ThinBox` without consuming and deallocating a `Box` // requires either the unstable `Unsize` marker trait, // or the unstable `unsized_locals` language feature, // or taking `&dyn T` and restricting to `T: Copy`. use std::alloc::*; use std::marker::PhantomData; struct ThinBox where T: ?Sized + Pointee>, { ptr: NonNull>, phantom: PhantomData, } impl ThinBox where T: ?Sized + Pointee>, { pub fn new>(value: Value) -> Self { let unsized_: &T = &value; let meta = metadata(unsized_); let meta_layout = Layout::for_value(&meta); let value_layout = Layout::for_value(&value); let (layout, offset) = meta_layout.extend(value_layout).unwrap(); // `DynMetadata` is pointer-sized: assert!(layout.size() > 0); // If `ThinBox` is generalized to any `T: ?Sized`, // handle ZSTs with a dangling pointer without going through `alloc()`, // like `Box` does. unsafe { let ptr = NonNull::new(alloc(layout)) .unwrap_or_else(|| handle_alloc_error(layout)) .cast::>(); ptr.as_ptr().write(meta); ptr.cast::().as_ptr().add(offset).cast::().write(value); Self { ptr, phantom: PhantomData } } } fn meta(&self) -> DynMetadata { unsafe { *self.ptr.as_ref() } } fn layout(&self) -> (Layout, usize) { let meta = self.meta(); Layout::for_value(&meta).extend(meta.layout()).unwrap() } fn value_ptr(&self) -> *const T { let (_, offset) = self.layout(); let data_ptr = unsafe { self.ptr.cast::().as_ptr().add(offset) }; ptr::from_raw_parts(data_ptr.cast(), self.meta()) } fn value_mut_ptr(&mut self) -> *mut T { let (_, offset) = self.layout(); // FIXME: can this line be shared with the same in `value_ptr()` // without upsetting Stacked Borrows? let data_ptr = unsafe { self.ptr.cast::().as_ptr().add(offset) }; from_raw_parts_mut(data_ptr.cast(), self.meta()) } } impl std::ops::Deref for ThinBox where T: ?Sized + Pointee>, { type Target = T; fn deref(&self) -> &T { unsafe { &*self.value_ptr() } } } impl std::ops::DerefMut for ThinBox where T: ?Sized + Pointee>, { fn deref_mut(&mut self) -> &mut T { unsafe { &mut *self.value_mut_ptr() } } } impl std::ops::Drop for ThinBox where T: ?Sized + Pointee>, { fn drop(&mut self) { let (layout, _) = self.layout(); unsafe { drop_in_place::(&mut **self); dealloc(self.ptr.cast().as_ptr(), layout); } } } }