1 files changed, 59 insertions, 0 deletions
diff --git a/tests/ui/consts/offset_from.rs b/tests/ui/consts/offset_from.rs
new file mode 100644
index 00000000000..465147041d9
--- /dev/null
+++ b/tests/ui/consts/offset_from.rs
@@ -0,0 +1,59 @@
+// run-pass
+
+#![feature(const_ptr_sub_ptr)]
+#![feature(ptr_sub_ptr)]
+
+struct Struct {
+    field: (),
+}
+
+#[repr(C)]
+struct Struct2 {
+    data: u8,
+    field: u8,
+}
+
+pub const OFFSET: usize = {
+    let uninit = std::mem::MaybeUninit::<Struct>::uninit();
+    let base_ptr: *const Struct = &uninit as *const _ as *const Struct;
+    // The following statement is UB (taking the address of an uninitialized field).
+    // Const eval doesn't detect this right now, but it may stop compiling at some point
+    // in the future.
+    let field_ptr = unsafe { &(*base_ptr).field as *const () as *const u8 };
+    let offset = unsafe { field_ptr.offset_from(base_ptr as *const u8) };
+    offset as usize
+};
+
+pub const OFFSET_2: usize = {
+    let uninit = std::mem::MaybeUninit::<Struct2>::uninit();
+    let base_ptr: *const Struct2 = &uninit as *const _ as *const Struct2;
+    let field_ptr = unsafe { &(*base_ptr).field as *const u8 };
+    let offset = unsafe { field_ptr.offset_from(base_ptr as *const u8) };
+    offset as usize
+};
+
+pub const OVERFLOW: isize = {
+    let uninit = std::mem::MaybeUninit::<Struct2>::uninit();
+    let base_ptr: *const Struct2 = &uninit as *const _ as *const Struct2;
+    let field_ptr = unsafe { &(*base_ptr).field as *const u8 };
+    unsafe { (base_ptr as *const u8).offset_from(field_ptr) }
+};
+
+pub const OFFSET_EQUAL_INTS: isize = {
+    let ptr = 1 as *const u8;
+    unsafe { ptr.offset_from(ptr) }
+};
+
+pub const OFFSET_UNSIGNED: usize = {
+    let a = ['a', 'b', 'c'];
+    let ptr = a.as_ptr();
+    unsafe { ptr.add(2).sub_ptr(ptr) }
+};
+
+fn main() {
+    assert_eq!(OFFSET, 0);
+    assert_eq!(OFFSET_2, 1);
+    assert_eq!(OVERFLOW, -1);
+    assert_eq!(OFFSET_EQUAL_INTS, 0);
+    assert_eq!(OFFSET_UNSIGNED, 2);
+}