1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
|
use core::alloc::{AllocError, Allocator, Layout};
use core::cell::Cell;
use core::mem::MaybeUninit;
use core::ptr::NonNull;
#[test]
fn uninitialized_zero_size_box() {
assert_eq!(
&*Box::<()>::new_uninit() as *const _,
NonNull::<MaybeUninit<()>>::dangling().as_ptr(),
);
assert_eq!(
Box::<[()]>::new_uninit_slice(4).as_ptr(),
NonNull::<MaybeUninit<()>>::dangling().as_ptr(),
);
assert_eq!(
Box::<[String]>::new_uninit_slice(0).as_ptr(),
NonNull::<MaybeUninit<String>>::dangling().as_ptr(),
);
}
#[derive(Clone, PartialEq, Eq, Debug)]
struct Dummy {
_data: u8,
}
#[test]
fn box_clone_and_clone_from_equivalence() {
for size in (0..8).map(|i| 2usize.pow(i)) {
let control = vec![Dummy { _data: 42 }; size].into_boxed_slice();
let clone = control.clone();
let mut copy = vec![Dummy { _data: 84 }; size].into_boxed_slice();
copy.clone_from(&control);
assert_eq!(control, clone);
assert_eq!(control, copy);
}
}
/// This test might give a false positive in case the box reallocates,
/// but the allocator keeps the original pointer.
///
/// On the other hand, it won't give a false negative: If it fails, then the
/// memory was definitely not reused.
#[test]
fn box_clone_from_ptr_stability() {
for size in (0..8).map(|i| 2usize.pow(i)) {
let control = vec![Dummy { _data: 42 }; size].into_boxed_slice();
let mut copy = vec![Dummy { _data: 84 }; size].into_boxed_slice();
let copy_raw = copy.as_ptr() as usize;
copy.clone_from(&control);
assert_eq!(copy.as_ptr() as usize, copy_raw);
}
}
#[test]
fn box_deref_lval() {
let x = Box::new(Cell::new(5));
x.set(1000);
assert_eq!(x.get(), 1000);
}
pub struct ConstAllocator;
unsafe impl Allocator for ConstAllocator {
fn allocate(&self, layout: Layout) -> Result<NonNull<[u8]>, AllocError> {
match layout.size() {
0 => Ok(NonNull::slice_from_raw_parts(layout.dangling(), 0)),
_ => unsafe {
let ptr = core::intrinsics::const_allocate(layout.size(), layout.align());
Ok(NonNull::new_unchecked(ptr as *mut [u8; 0] as *mut [u8]))
},
}
}
unsafe fn deallocate(&self, _ptr: NonNull<u8>, layout: Layout) {
match layout.size() {
0 => { /* do nothing */ }
_ => { /* do nothing too */ }
}
}
fn allocate_zeroed(&self, layout: Layout) -> Result<NonNull<[u8]>, AllocError> {
let ptr = self.allocate(layout)?;
if layout.size() > 0 {
unsafe {
ptr.as_mut_ptr().write_bytes(0, layout.size());
}
}
Ok(ptr)
}
unsafe fn grow(
&self,
ptr: NonNull<u8>,
old_layout: Layout,
new_layout: Layout,
) -> Result<NonNull<[u8]>, AllocError> {
debug_assert!(
new_layout.size() >= old_layout.size(),
"`new_layout.size()` must be greater than or equal to `old_layout.size()`"
);
let new_ptr = self.allocate(new_layout)?;
if new_layout.size() > 0 {
// Safety: `new_ptr` is valid for writes and `ptr` for reads of
// `old_layout.size()`, because `new_layout.size() >=
// old_layout.size()` (which is an invariant that must be upheld by
// callers).
unsafe {
new_ptr.as_mut_ptr().copy_from_nonoverlapping(ptr.as_ptr(), old_layout.size());
}
// Safety: `ptr` is never used again is also an invariant which must
// be upheld by callers.
unsafe {
self.deallocate(ptr, old_layout);
}
}
Ok(new_ptr)
}
unsafe fn grow_zeroed(
&self,
ptr: NonNull<u8>,
old_layout: Layout,
new_layout: Layout,
) -> Result<NonNull<[u8]>, AllocError> {
// Safety: Invariants of `grow_zeroed` and `grow` are the same, and must
// be enforced by callers.
let new_ptr = unsafe { self.grow(ptr, old_layout, new_layout)? };
if new_layout.size() > 0 {
let old_size = old_layout.size();
let new_size = new_layout.size();
let raw_ptr = new_ptr.as_mut_ptr();
// Safety:
// - `grow` returned Ok, so the returned pointer must be valid for
// `new_size` bytes
// - `new_size` must be larger than `old_size`, which is an
// invariant which must be upheld by callers.
unsafe {
raw_ptr.add(old_size).write_bytes(0, new_size - old_size);
}
}
Ok(new_ptr)
}
unsafe fn shrink(
&self,
ptr: NonNull<u8>,
old_layout: Layout,
new_layout: Layout,
) -> Result<NonNull<[u8]>, AllocError> {
debug_assert!(
new_layout.size() <= old_layout.size(),
"`new_layout.size()` must be smaller than or equal to `old_layout.size()`"
);
let new_ptr = self.allocate(new_layout)?;
if new_layout.size() > 0 {
// Safety: `new_ptr` and `ptr` are valid for reads/writes of
// `new_layout.size()` because of the invariants of shrink, which
// include `new_layout.size()` being smaller than (or equal to)
// `old_layout.size()`.
unsafe {
new_ptr.as_mut_ptr().copy_from_nonoverlapping(ptr.as_ptr(), new_layout.size());
}
// Safety: `ptr` is never used again is also an invariant which must
// be upheld by callers.
unsafe {
self.deallocate(ptr, old_layout);
}
}
Ok(new_ptr)
}
fn by_ref(&self) -> &Self
where
Self: Sized,
{
self
}
}
|
