1 files changed, 112 insertions, 0 deletions
diff --git a/tests/ui/consts/offset.rs b/tests/ui/consts/offset.rs
new file mode 100644
index 00000000000..b2c663fe617
--- /dev/null
+++ b/tests/ui/consts/offset.rs
@@ -0,0 +1,112 @@
+// 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);
+}