mirror of
https://github.com/rust-lang/rust-clippy
synced 2024-11-14 17:07:17 +00:00
73 lines
2.7 KiB
Rust
73 lines
2.7 KiB
Rust
#![warn(clippy::transmute_ptr_to_ptr)]
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#![allow(clippy::borrow_as_ptr)]
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// Make sure we can modify lifetimes, which is one of the recommended uses
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// of transmute
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// Make sure we can do static lifetime transmutes
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unsafe fn transmute_lifetime_to_static<'a, T>(t: &'a T) -> &'static T {
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std::mem::transmute::<&'a T, &'static T>(t)
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}
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// Make sure we can do non-static lifetime transmutes
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unsafe fn transmute_lifetime<'a, 'b, T>(t: &'a T, u: &'b T) -> &'b T {
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std::mem::transmute::<&'a T, &'b T>(t)
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}
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struct LifetimeParam<'a> {
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s: &'a str,
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}
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struct GenericParam<T> {
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t: T,
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}
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fn transmute_ptr_to_ptr() {
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let ptr = &1u32 as *const u32;
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let mut_ptr = &mut 1u32 as *mut u32;
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unsafe {
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// pointer-to-pointer transmutes; bad
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let _: *const f32 = ptr as *const f32;
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//~^ ERROR: transmute from a pointer to a pointer
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//~| NOTE: `-D clippy::transmute-ptr-to-ptr` implied by `-D warnings`
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let _: *mut f32 = mut_ptr as *mut f32;
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//~^ ERROR: transmute from a pointer to a pointer
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// ref-ref transmutes; bad
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let _: &f32 = &*(&1u32 as *const u32 as *const f32);
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//~^ ERROR: transmute from a reference to a reference
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let _: &f32 = &*(&1f64 as *const f64 as *const f32);
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//~^ ERROR: transmute from a reference to a reference
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//:^ this test is here because both f32 and f64 are the same TypeVariant, but they are not
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// the same type
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let _: &mut f32 = &mut *(&mut 1u32 as *mut u32 as *mut f32);
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//~^ ERROR: transmute from a reference to a reference
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let _: &GenericParam<f32> = &*(&GenericParam { t: 1u32 } as *const GenericParam<u32> as *const GenericParam<f32>);
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//~^ ERROR: transmute from a reference to a reference
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let u64_ref: &u64 = &0u64;
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let u8_ref: &u8 = unsafe { &*(u64_ref as *const u64 as *const u8) };
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//~^ ERROR: transmute from a reference to a reference
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}
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// these are recommendations for solving the above; if these lint we need to update
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// those suggestions
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let _ = ptr as *const f32;
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let _ = mut_ptr as *mut f32;
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let _ = unsafe { &*(&1u32 as *const u32 as *const f32) };
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let _ = unsafe { &mut *(&mut 1u32 as *mut u32 as *mut f32) };
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// transmute internal lifetimes, should not lint
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let s = "hello world".to_owned();
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let lp = LifetimeParam { s: &s };
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let _: &LifetimeParam<'static> = unsafe { std::mem::transmute(&lp) };
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let _: &GenericParam<&LifetimeParam<'static>> = unsafe { std::mem::transmute(&GenericParam { t: &lp }) };
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}
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// dereferencing raw pointers in const contexts, should not lint as it's unstable (issue 5959)
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const _: &() = {
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struct Zst;
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let zst = &Zst;
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unsafe { std::mem::transmute::<&'static Zst, &'static ()>(zst) }
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};
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fn main() {}
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