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// run-pass
use std::ptr;
#[repr(C)]
struct Struct {
a: u32,
b: u32,
c: u32,
}
static S: Struct = Struct { a: 0, b: 0, c: 0 };
// For these tests we use offset_from to check that two pointers are equal.
// Rust doesn't currently support comparing pointers in const fn.
static OFFSET_NO_CHANGE: bool = unsafe {
let p1 = &S.b as *const u32;
let p2 = p1.offset(2).offset(-2);
p1.offset_from(p2) == 0
};
static OFFSET_MIDDLE: bool = unsafe {
let p1 = (&S.a as *const u32).offset(1);
let p2 = (&S.c as *const u32).offset(-1);
p1.offset_from(p2) == 0
};
// Pointing to the end of the allocation is OK
static OFFSET_END: bool = unsafe {
let p1 = (&S.a as *const u32).offset(3);
let p2 = (&S.c as *const u32).offset(1);
p1.offset_from(p2) == 0
};
// Casting though a differently sized type is OK
static OFFSET_U8_PTR: bool = unsafe {
let p1 = (&S.a as *const u32 as *const u8).offset(5);
let p2 = (&S.c as *const u32 as *const u8).offset(-3);
p1.offset_from(p2) == 0
};
// Any offset with a ZST does nothing
const OFFSET_ZST: bool = unsafe {
let pz = &() as *const ();
// offset_from can't work with ZSTs, so cast to u8 ptr
let p1 = pz.offset(5) as *const u8;
let p2 = pz.offset(isize::MIN) as *const u8;
p1.offset_from(p2) == 0
};
const OFFSET_ZERO: bool = unsafe {
let p = [0u8; 0].as_ptr();
p.offset(0).offset_from(p) == 0
};
const OFFSET_ONE: bool = unsafe {
let p = &42u32 as *const u32;
p.offset(1).offset_from(p) == 1
};
const OFFSET_DANGLING: bool = unsafe {
let p = ptr::NonNull::<u8>::dangling().as_ptr();
p.offset(0).offset_from(p) == 0
};
const OFFSET_UNALIGNED: bool = unsafe {
let arr = [0u8; 32];
let p1 = arr.as_ptr();
let p2 = (p1.offset(2) as *const u32).offset(1);
(p2 as *const u8).offset_from(p1) == 6
};
const WRAP_OFFSET_NO_CHANGE: bool = unsafe {
let p1 = &42u32 as *const u32;
let p2 = p1.wrapping_offset(1000).wrapping_offset(-1000);
let p3 = p1.wrapping_offset(-1000).wrapping_offset(1000);
(p1.offset_from(p2) == 0) & (p1.offset_from(p3) == 0)
};
const WRAP_ADDRESS_SPACE: bool = unsafe {
let p1 = &42u8 as *const u8;
let p2 = p1.wrapping_offset(isize::MIN).wrapping_offset(isize::MIN);
p1.offset_from(p2) == 0
};
// Wrap on the count*size_of::<T>() calculation.
const WRAP_SIZE_OF: bool = unsafe {
// Make sure that if p1 moves backwards, we are still in range
let arr = [0u32; 2];
let p = &arr[1] as *const u32;
// With wrapping arithmetic, isize::MAX * 4 == -4
let wrapped = p.wrapping_offset(isize::MAX);
let backward = p.wrapping_offset(-1);
wrapped.offset_from(backward) == 0
};
const WRAP_INTEGER_POINTER: bool = unsafe {
let p1 = (0x42 as *const u32).wrapping_offset(4);
let p2 = 0x52 as *const u32;
p1.offset_from(p2) == 0
};
const WRAP_NULL: bool = unsafe {
let p1 = ptr::null::<u32>().wrapping_offset(1);
let p2 = 0x4 as *const u32;
p1.offset_from(p2) == 0
};
fn main() {
assert!(OFFSET_NO_CHANGE);
assert!(OFFSET_MIDDLE);
assert!(OFFSET_END);
assert!(OFFSET_U8_PTR);
assert!(OFFSET_ZST);
assert!(OFFSET_ZERO);
assert!(OFFSET_ONE);
assert!(OFFSET_DANGLING);
assert!(OFFSET_UNALIGNED);
assert!(WRAP_OFFSET_NO_CHANGE);
assert!(WRAP_ADDRESS_SPACE);
assert!(WRAP_SIZE_OF);
assert!(WRAP_INTEGER_POINTER);
assert!(WRAP_NULL);
}
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