1 #![warn(clippy::transmute_ptr_to_ptr)]
2 #![allow(clippy::borrow_as_ptr)]
4 // Make sure we can modify lifetimes, which is one of the recommended uses
7 // Make sure we can do static lifetime transmutes
8 unsafe fn transmute_lifetime_to_static<'a, T>(t: &'a T) -> &'static T {
9 std::mem::transmute::<&'a T, &'static T>(t)
12 // Make sure we can do non-static lifetime transmutes
13 unsafe fn transmute_lifetime<'a, 'b, T>(t: &'a T, u: &'b T) -> &'b T {
14 std::mem::transmute::<&'a T, &'b T>(t)
17 struct LifetimeParam<'a> {
21 struct GenericParam<T> {
25 fn transmute_ptr_to_ptr() {
26 let ptr = &1u32 as *const u32;
27 let mut_ptr = &mut 1u32 as *mut u32;
29 // pointer-to-pointer transmutes; bad
30 let _: *const f32 = std::mem::transmute(ptr);
31 let _: *mut f32 = std::mem::transmute(mut_ptr);
32 // ref-ref transmutes; bad
33 let _: &f32 = std::mem::transmute(&1u32);
34 let _: &f64 = std::mem::transmute(&1f32);
35 // ^ this test is here because both f32 and f64 are the same TypeVariant, but they are not
37 let _: &mut f32 = std::mem::transmute(&mut 1u32);
38 let _: &GenericParam<f32> = std::mem::transmute(&GenericParam { t: 1u32 });
41 // these are recommendations for solving the above; if these lint we need to update
43 let _ = ptr as *const f32;
44 let _ = mut_ptr as *mut f32;
45 let _ = unsafe { &*(&1u32 as *const u32 as *const f32) };
46 let _ = unsafe { &mut *(&mut 1u32 as *mut u32 as *mut f32) };
48 // transmute internal lifetimes, should not lint
49 let s = "hello world".to_owned();
50 let lp = LifetimeParam { s: &s };
51 let _: &LifetimeParam<'static> = unsafe { std::mem::transmute(&lp) };
52 let _: &GenericParam<&LifetimeParam<'static>> = unsafe { std::mem::transmute(&GenericParam { t: &lp }) };
55 // dereferencing raw pointers in const contexts, should not lint as it's unstable (issue 5959)
60 unsafe { std::mem::transmute::<&'static Zst, &'static ()>(zst) }