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// compile-flags: -Zunleash-the-miri-inside-of-you
// This test demonstrates a shortcoming of the `MaybeMutBorrowedLocals` analysis. It does not
// handle code that takes a reference to one field of a struct, then use pointer arithmetic to
// transform it to another field of that same struct that may have interior mutability. For now,
// this is UB, but this may change in the future. See [rust-lang/unsafe-code-guidelines#134].
//
// [rust-lang/unsafe-code-guidelines#134]: https://github.com/rust-lang/unsafe-code-guidelines/issues/134
#![feature(core_intrinsics, rustc_attrs, const_raw_ptr_deref)]
use std::cell::UnsafeCell;
use std::intrinsics::rustc_peek;
#[repr(C)]
struct PartialInteriorMut {
zst: [i32; 0],
cell: UnsafeCell<i32>,
}
#[rustc_mir(rustc_peek_indirectly_mutable,stop_after_dataflow)]
const BOO: i32 = {
let x = PartialInteriorMut {
zst: [],
cell: UnsafeCell::new(0),
};
let p_zst: *const _ = &x.zst ; // Doesn't cause `x` to get marked as indirectly mutable.
let rmut_cell = unsafe {
// Take advantage of the fact that `zst` and `cell` are at the same location in memory.
// This trick would work with any size type if miri implemented `ptr::offset`.
let p_cell = p_zst as *const UnsafeCell<i32>;
let pmut_cell = (*p_cell).get();
&mut *pmut_cell
};
*rmut_cell = 42; // Mutates `x` indirectly even though `x` is not marked indirectly mutable!!!
let val = *rmut_cell;
rustc_peek(x); //~ ERROR rustc_peek: bit not set
val
};
fn main() {
println!("{}", BOO);
}
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