Rust errors / Const, static and compile-time
Rust compiler error · checked with rustc 1.99.0
Rust error E0607: cannot cast thin pointer `*const u8` to wide pointer `*const [u8]`
What it meansA cast between a thin and a wide pointer was attempted.
What rustc prints
error[E0607]: cannot cast thin pointer `*const u8` to wide pointer `*const [u8]`
--> main.rs:4:1
|
4 | v as *const [u8];
| ^^^^^^^^^^^^^^^^Real output of rustc 1.99.0 compiling the official example below (2021 edition). Your names and line numbers will differ; the first line is the part to match.
The compiler team's explanation
A cast between a thin and a wide pointer was attempted.
Erroneous code example:
let v = core::ptr::null::<u8>();
v as *const [u8];First: what are thin and wide pointers?
Thin pointers are "simple" pointers: they are purely a reference to a memory address.
Wide pointers are pointers referencing Dynamically Sized Types (also called DSTs). DSTs don't have a statically known size, therefore they can only exist behind some kind of pointer that contains additional information. For example, slices and trait objects are DSTs. In the case of slices, the additional information the wide pointer holds is their size.
To fix this error, don't try to cast directly between thin and wide pointers.
For more information about type casts, take a look at the section of the The Rust Reference on type cast expressions.
From rustc --explain E0607 (1.99.0), part of the Rust project, MIT or Apache-2.0. Official page.
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