2 #![warn(clippy::transmutes_expressible_as_ptr_casts)]
3 // These two warnings currrently cover the cases transmutes_expressible_as_ptr_casts
4 // would otherwise be responsible for
5 #![warn(clippy::useless_transmute)]
6 #![warn(clippy::transmute_ptr_to_ptr)]
7 #![allow(unused_unsafe)]
10 use std::mem::{size_of, transmute};
12 // rustc_typeck::check::cast contains documentation about when a cast `e as U` is
13 // valid, which we quote from below.
15 // We should see an error message for each transmute, and no error messages for
16 // the casts, since the casts are the recommended fixes.
18 // e is an integer and U is *U_0, while U_0: Sized; addr-ptr-cast
19 let _ptr_i32_transmute = unsafe { usize::MAX as *const i32 };
20 let ptr_i32 = usize::MAX as *const i32;
22 // e has type *T, U is *U_0, and either U_0: Sized ...
23 let _ptr_i8_transmute = unsafe { ptr_i32 as *const i8 };
24 let _ptr_i8 = ptr_i32 as *const i8;
26 let slice_ptr = &[0, 1, 2, 3] as *const [i32];
28 // ... or pointer_kind(T) = pointer_kind(U_0); ptr-ptr-cast
29 let _ptr_to_unsized_transmute = unsafe { slice_ptr as *const [u16] };
30 let _ptr_to_unsized = slice_ptr as *const [u16];
31 // TODO: We could try testing vtable casts here too, but maybe
32 // we should wait until std::raw::TraitObject is stabilized?
34 // e has type *T and U is a numeric type, while T: Sized; ptr-addr-cast
35 let _usize_from_int_ptr_transmute = unsafe { ptr_i32 as usize };
36 let _usize_from_int_ptr = ptr_i32 as usize;
38 let array_ref: &[i32; 4] = &[1, 2, 3, 4];
40 // e has type &[T; n] and U is *const T; array-ptr-cast
41 let _array_ptr_transmute = unsafe { array_ref as *const [i32; 4] };
42 let _array_ptr = array_ref as *const [i32; 4];
44 fn foo(_: usize) -> u8 {
48 // e is a function pointer type and U has type *T, while T: Sized; fptr-ptr-cast
49 let _usize_ptr_transmute = unsafe { foo as *const usize };
50 let _usize_ptr_transmute = foo as *const usize;
52 // e is a function pointer type and U is an integer; fptr-addr-cast
53 let _usize_from_fn_ptr_transmute = unsafe { foo as usize };
54 let _usize_from_fn_ptr = foo as *const usize;
57 // If a ref-to-ptr cast of this form where the pointer type points to a type other
58 // than the referenced type, calling `CastCheck::do_check` has been observed to
59 // cause an ICE error message. `do_check` is currently called inside the
60 // `transmutes_expressible_as_ptr_casts` check, but other, more specific lints
61 // currently prevent it from being called in these cases. This test is meant to
62 // fail if the ordering of the checks ever changes enough to cause these cases to
63 // fall through into `do_check`.
64 fn trigger_do_check_to_emit_error(in_param: &[i32; 1]) -> *const u8 {
65 unsafe { in_param as *const [i32; 1] as *const u8 }
72 struct Pair(u32, u32);
74 fn cannot_be_expressed_as_pointer_cast(in_param: Single) -> Pair {
75 assert_eq!(size_of::<Single>(), size_of::<Pair>());
77 unsafe { transmute::<Single, Pair>(in_param) }