bjoernager/rust
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safe transmute: require that src referent is smaller than dst

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The source referent absolutely must be smaller than the destination
referent of a ref-to-ref transmute; the excess bytes referenced
cannot arise from thin air, even if those bytes are uninitialized.
This commit is contained in:
Jack Wrenn 2024-03-13 00:11:36 +00:00
parent a165f1f650
commit 216df4a8e6
8 changed files with 122 additions and 5 deletions
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7
compiler/rustc_trait_selection/src/traits/error_reporting/type_err_ctxt_ext.rs
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@ -3091,6 +3091,13 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
rustc_transmute::Reason::DstIsTooBig => {
format!("The size of `{src}` is smaller than the size of `{dst}`")
}
rustc_transmute::Reason::DstRefIsTooBig { src, dst } => {
let src_size = src.size;
let dst_size = dst.size;
format!(
"The referent size of `{src}` ({src_size} bytes) is smaller than that of `{dst}` ({dst_size} bytes)"
)
}
rustc_transmute::Reason::SrcSizeOverflow => {
format!(
"values of the type `{src}` are too big for the current architecture"