58 lines
2.0 KiB
Rust
58 lines
2.0 KiB
Rust
#![warn(clippy::transmutes_expressible_as_ptr_casts)]
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// rustc_typeck::check::cast contains documentation about when a cast `e as U` is
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// valid, which we quote from below.
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use std::mem::transmute;
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fn main() {
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// e is an integer and U is *U_0, while U_0: Sized; addr-ptr-cast
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let ptr_i32_transmute = unsafe {
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transmute::<isize, *const i32>(-1)
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};
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let ptr_i32 = -1isize as *const i32;
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// e has type *T, U is *U_0, and either U_0: Sized ...
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let ptr_i8_transmute = unsafe {
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transmute::<*const i32, *const i8>(ptr_i32)
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};
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let ptr_i8 = ptr_i32 as *const i8;
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let slice_ptr = &[0,1,2,3] as *const [i32];
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// ... or pointer_kind(T) = pointer_kind(U_0); ptr-ptr-cast
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let ptr_to_unsized_transmute = unsafe {
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transmute::<*const [i32], *const [u16]>(slice_ptr)
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};
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let ptr_to_unsized = slice_ptr as *const [u16];
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// TODO: We could try testing vtable casts here too, but maybe
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// we should wait until std::raw::TraitObject is stabilized?
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// e has type *T and U is a numeric type, while T: Sized; ptr-addr-cast
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let usize_from_int_ptr_transmute = unsafe {
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transmute::<*const i32, usize>(ptr_i32)
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};
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let usize_from_int_ptr = ptr_i32 as usize;
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let array_ref: &[i32; 4] = &[1,2,3,4];
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// e has type &[T; n] and U is *const T; array-ptr-cast
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let array_ptr_transmute = unsafe {
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transmute::<&[i32; 4], *const [i32; 4]>(array_ref)
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};
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let array_ptr = array_ref as *const [i32; 4];
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fn foo(_: usize) -> u8 { 42 }
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// e is a function pointer type and U has type *T, while T: Sized; fptr-ptr-cast
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let usize_ptr_transmute = unsafe {
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transmute::<fn(usize) -> u8, *const usize>(foo)
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};
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let usize_ptr_transmute = foo as *const usize;
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// e is a function pointer type and U is an integer; fptr-addr-cast
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let usize_from_fn_ptr_transmute = unsafe {
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transmute::<fn(usize) -> u8, usize>(foo)
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};
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let usize_from_fn_ptr = foo as *const usize;
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}
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