Messages in this thread Patch in this message | | | Date | Mon, 14 Aug 2023 08:47:03 +0000 | From | Benno Lossin <> | Subject | [PATCH v4 06/13] rust: init: make initializer values inaccessible after initializing |
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Previously the init macros would create a local variable with the name and hygiene of the field that is being initialized to store the value of the field. This would override any user defined variables. For example: ``` struct Foo { a: usize, b: usize, } let a = 10; let foo = init!(Foo{ a: a + 1, // This creates a local variable named `a`. b: a, // This refers to that variable! }); let foo = Box::init!(foo)?; assert_eq!(foo.a, 11); assert_eq!(foo.b, 11); ```
This patch changes this behavior, so the above code would panic at the last assertion, since `b` would have value 10.
Reviewed-by: Martin Rodriguez Reboredo <yakoyoku@gmail.com> Reviewed-by: Alice Ryhl <aliceryhl@google.com> Reviewed-by: Gary Guo <gary@garyguo.net> Signed-off-by: Benno Lossin <benno.lossin@proton.me> --- v3 -> v4: - added Reviewed-by from Gary.
v2 -> v3: - added Reviewed-by's from Martin and Alice.
rust/kernel/init/macros.rs | 20 +++++++++++--------- 1 file changed, 11 insertions(+), 9 deletions(-)
diff --git a/rust/kernel/init/macros.rs b/rust/kernel/init/macros.rs index 2bad086cda0a..cfeacc4b3f7d 100644 --- a/rust/kernel/init/macros.rs +++ b/rust/kernel/init/macros.rs @@ -1075,13 +1075,13 @@ macro_rules! __init_internal { // In-place initialization syntax. @munch_fields($field:ident <- $val:expr, $($rest:tt)*), ) => { - let $field = $val; + let init = $val; // Call the initializer. // // SAFETY: `slot` is valid, because we are inside of an initializer closure, we // return when an error/panic occurs. // We also use the `data` to require the correct trait (`Init` or `PinInit`) for `$field`. - unsafe { $data.$field(::core::ptr::addr_of_mut!((*$slot).$field), $field)? }; + unsafe { $data.$field(::core::ptr::addr_of_mut!((*$slot).$field), init)? }; // Create the drop guard: // // We rely on macro hygiene to make it impossible for users to access this local variable. @@ -1107,12 +1107,12 @@ macro_rules! __init_internal { // In-place initialization syntax. @munch_fields($field:ident <- $val:expr, $($rest:tt)*), ) => { - let $field = $val; + let init = $val; // Call the initializer. // // SAFETY: `slot` is valid, because we are inside of an initializer closure, we // return when an error/panic occurs. - unsafe { $crate::init::Init::__init($field, ::core::ptr::addr_of_mut!((*$slot).$field))? }; + unsafe { $crate::init::Init::__init(init, ::core::ptr::addr_of_mut!((*$slot).$field))? }; // Create the drop guard: // // We rely on macro hygiene to make it impossible for users to access this local variable. @@ -1138,11 +1138,13 @@ macro_rules! __init_internal { // Init by-value. @munch_fields($field:ident $(: $val:expr)?, $($rest:tt)*), ) => { - $(let $field = $val;)? - // Initialize the field. - // - // SAFETY: The memory at `slot` is uninitialized. - unsafe { ::core::ptr::write(::core::ptr::addr_of_mut!((*$slot).$field), $field) }; + { + $(let $field = $val;)? + // Initialize the field. + // + // SAFETY: The memory at `slot` is uninitialized. + unsafe { ::core::ptr::write(::core::ptr::addr_of_mut!((*$slot).$field), $field) }; + } // Create the drop guard: // // We rely on macro hygiene to make it impossible for users to access this local variable. -- 2.41.0
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