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This is more robust again refactors that may change the way let bindings are created. Cc: stable@vger.kernel.org Reviewed-by: Alice Ryhl Signed-off-by: Gary Guo --- rust/pin-init/internal/src/init.rs | 78 ++++++++++++++++++-------------------- 1 file changed, 37 insertions(+), 41 deletions(-) diff --git a/rust/pin-init/internal/src/init.rs b/rust/pin-init/internal/src/init.rs index daa3f1c6466e..0a6600e8156c 100644 --- a/rust/pin-init/internal/src/init.rs +++ b/rust/pin-init/internal/src/init.rs @@ -249,10 +249,6 @@ fn init_fields( }); // Again span for better diagnostics let write = quote_spanned!(ident.span()=> ::core::ptr::write); - // NOTE: the field accessor ensures that the initialized field is properly aligned. - // Unaligned fields will cause the compiler to emit E0793. We do not support - // unaligned fields since `Init::__init` requires an aligned pointer; the call to - // `ptr::write` below has the same requirement. let accessor = if pinned { let project_ident = format_ident!("__project_{ident}"); quote! { @@ -367,49 +363,49 @@ fn init_fields( } } -/// Generate the check for ensuring that every field has been initialized. +/// Generate the check for ensuring that every field has been initialized and aligned. fn make_field_check( fields: &Punctuated, init_kind: InitKind, path: &Path, ) -> TokenStream { - let field_attrs = fields + let field_attrs: Vec<_> = fields .iter() - .filter_map(|f| f.kind.ident().map(|_| &f.attrs)); - let field_name = fields.iter().filter_map(|f| f.kind.ident()); - match init_kind { - InitKind::Normal => quote! { - // We use unreachable code to ensure that all fields have been mentioned exactly once, - // this struct initializer will still be type-checked and complain with a very natural - // error message if a field is forgotten/mentioned more than once. - #[allow(unreachable_code, clippy::diverging_sub_expression)] - // SAFETY: this code is never executed. - let _ = || unsafe { - ::core::ptr::write(slot, #path { - #( - #(#field_attrs)* - #field_name: ::core::panic!(), - )* - }) - }; - }, - InitKind::Zeroing => quote! { - // We use unreachable code to ensure that all fields have been mentioned at most once. - // Since the user specified `..Zeroable::zeroed()` at the end, all missing fields will - // be zeroed. This struct initializer will still be type-checked and complain with a - // very natural error message if a field is mentioned more than once, or doesn't exist. - #[allow(unreachable_code, clippy::diverging_sub_expression, unused_assignments)] - // SAFETY: this code is never executed. - let _ = || unsafe { - ::core::ptr::write(slot, #path { - #( - #(#field_attrs)* - #field_name: ::core::panic!(), - )* - ..::core::mem::zeroed() - }) - }; - }, + .filter_map(|f| f.kind.ident().map(|_| &f.attrs)) + .collect(); + let field_name: Vec<_> = fields.iter().filter_map(|f| f.kind.ident()).collect(); + let zeroing_trailer = match init_kind { + InitKind::Normal => None, + InitKind::Zeroing => Some(quote! { + ..::core::mem::zeroed() + }), + }; + quote! { + #[allow(unreachable_code, clippy::diverging_sub_expression)] + // We use unreachable code to perform field checks. They're still checked by the compiler. + // SAFETY: this code is never executed. + let _ = || unsafe { + // Create references to ensure that the initialized field is properly aligned. + // Unaligned fields will cause the compiler to emit E0793. We do not support + // unaligned fields since `Init::__init` requires an aligned pointer; the call to + // `ptr::write` for value-initialization case has the same requirement. + #( + #(#field_attrs)* + let _ = &(*slot).#field_name; + )* + + // If the zeroing trailer is not present, this checks that all fields have been + // mentioned exactly once. If the zeroing trailer is present, all missing fields will be + // zeroed, so this checks that all fields have been mentioned at most once. The use of + // struct initializer will still generate very natural error messages for any misuse. + ::core::ptr::write(slot, #path { + #( + #(#field_attrs)* + #field_name: ::core::panic!(), + )* + #zeroing_trailer + }) + }; } } -- 2.51.2