Fix safety of transparent_convert (#681)

rust-diplomat · Sep 9, 2024 · d741c84 · d741c84
1 parent a43baaf
commit d741c84
Show file tree

Hide file tree

Showing 2 changed files with 3 additions and 0 deletions.
diff --git a/macro/src/lib.rs b/macro/src/lib.rs
@@ -476,6 +476,7 @@ pub fn transparent_convert(
 
     let full = quote! {
         #expanded
+        #[repr(transparent)]
         #input_cached
     };
     proc_macro::TokenStream::from(full.to_token_stream())

diff --git a/macro/src/transparent_convert.rs b/macro/src/transparent_convert.rs
@@ -21,6 +21,8 @@ pub fn gen_transparent_convert(s: ItemStruct) -> proc_macro2::TokenStream {
         impl #impl_generics #struct_name #ty_generics {
             // can potentially add transparent_convert_owned, _mut later
             pub(crate) fn transparent_convert(from: &'transparent_convert_outer #field1) -> &'transparent_convert_outer Self {
+                // Safety: This is safe because the caller of gen_transparent_convert
+                // adds a repr(transparent) to the struct.
                 unsafe {
                     &*(from as *const #field1 as *const Self)
                 }