10 static S: Struct = Struct { a: 0, b: 0, c: 0 };
12 // For these tests we use offset_from to check that two pointers are equal.
13 // Rust doesn't currently support comparing pointers in const fn.
15 static OFFSET_NO_CHANGE: bool = unsafe {
16 let p1 = &S.b as *const u32;
17 let p2 = p1.offset(2).offset(-2);
18 p1.offset_from(p2) == 0
20 static OFFSET_MIDDLE: bool = unsafe {
21 let p1 = (&S.a as *const u32).offset(1);
22 let p2 = (&S.c as *const u32).offset(-1);
23 p1.offset_from(p2) == 0
25 // Pointing to the end of the allocation is OK
26 static OFFSET_END: bool = unsafe {
27 let p1 = (&S.a as *const u32).offset(3);
28 let p2 = (&S.c as *const u32).offset(1);
29 p1.offset_from(p2) == 0
31 // Casting though a differently sized type is OK
32 static OFFSET_U8_PTR: bool = unsafe {
33 let p1 = (&S.a as *const u32 as *const u8).offset(5);
34 let p2 = (&S.c as *const u32 as *const u8).offset(-3);
35 p1.offset_from(p2) == 0
37 // Any offset with a ZST does nothing
38 const OFFSET_ZST: bool = unsafe {
39 let pz = &() as *const ();
40 // offset_from can't work with ZSTs, so cast to u8 ptr
41 let p1 = pz.offset(5) as *const u8;
42 let p2 = pz.offset(isize::MIN) as *const u8;
43 p1.offset_from(p2) == 0
45 const OFFSET_ZERO: bool = unsafe {
46 let p = [0u8; 0].as_ptr();
47 p.offset(0).offset_from(p) == 0
49 const OFFSET_ONE: bool = unsafe {
50 let p = &42u32 as *const u32;
51 p.offset(1).offset_from(p) == 1
53 const OFFSET_DANGLING: bool = unsafe {
54 let p = ptr::NonNull::<u8>::dangling().as_ptr();
55 p.offset(0).offset_from(p) == 0
57 const OFFSET_UNALIGNED: bool = unsafe {
59 let p1 = arr.as_ptr();
60 let p2 = (p1.offset(2) as *const u32).offset(1);
61 (p2 as *const u8).offset_from(p1) == 6
64 const WRAP_OFFSET_NO_CHANGE: bool = unsafe {
65 let p1 = &42u32 as *const u32;
66 let p2 = p1.wrapping_offset(1000).wrapping_offset(-1000);
67 let p3 = p1.wrapping_offset(-1000).wrapping_offset(1000);
68 (p1.offset_from(p2) == 0) & (p1.offset_from(p3) == 0)
70 const WRAP_ADDRESS_SPACE: bool = unsafe {
71 let p1 = &42u8 as *const u8;
72 let p2 = p1.wrapping_offset(isize::MIN).wrapping_offset(isize::MIN);
73 p1.offset_from(p2) == 0
75 // Wrap on the count*size_of::<T>() calculation.
76 const WRAP_SIZE_OF: bool = unsafe {
77 // Make sure that if p1 moves backwards, we are still in range
79 let p = &arr[1] as *const u32;
80 // With wrapping arithmetic, isize::MAX * 4 == -4
81 let wrapped = p.wrapping_offset(isize::MAX);
82 let backward = p.wrapping_offset(-1);
83 wrapped.offset_from(backward) == 0
85 const WRAP_INTEGER_POINTER: bool = unsafe {
86 let p1 = (0x42 as *const u32).wrapping_offset(4);
87 let p2 = 0x52 as *const u32;
88 p1.offset_from(p2) == 0
90 const WRAP_NULL: bool = unsafe {
91 let p1 = ptr::null::<u32>().wrapping_offset(1);
92 let p2 = 0x4 as *const u32;
93 p1.offset_from(p2) == 0
97 assert!(OFFSET_NO_CHANGE);
98 assert!(OFFSET_MIDDLE);
100 assert!(OFFSET_U8_PTR);
102 assert!(OFFSET_ZERO);
104 assert!(OFFSET_DANGLING);
105 assert!(OFFSET_UNALIGNED);
107 assert!(WRAP_OFFSET_NO_CHANGE);
108 assert!(WRAP_ADDRESS_SPACE);
109 assert!(WRAP_SIZE_OF);
110 assert!(WRAP_INTEGER_POINTER);