From b9b88be046a92a43d70badb340cac9ffd9695dcb Mon Sep 17 00:00:00 2001 From: Benno Lossin Date: Mon, 14 Aug 2023 08:46:55 +0000 Subject: [PATCH] rust: init: wrap type checking struct initializers in a closure In the implementation of the init macros there is a `if false` statement that type checks the initializer to ensure every field is initialized. Since the next patch has a stack variable to store the struct, the function might allocate too much memory on debug builds. Putting the struct into a closure that is never executed ensures that even in debug builds no stack overflow error is caused. In release builds this was not a problem since the code was optimized away due to the `if false`. Reviewed-by: Martin Rodriguez Reboredo Reviewed-by: Alice Ryhl Reviewed-by: Gary Guo Signed-off-by: Benno Lossin Link: https://lore.kernel.org/r/20230814084602.25699-6-benno.lossin@proton.me Signed-off-by: Miguel Ojeda --- rust/kernel/init/macros.rs | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/rust/kernel/init/macros.rs b/rust/kernel/init/macros.rs index 5063b45970f3..a1ccc978feab 100644 --- a/rust/kernel/init/macros.rs +++ b/rust/kernel/init/macros.rs @@ -1040,14 +1040,14 @@ macro_rules! __init_internal { // 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)] - if false { + let _ = || { $crate::__init_internal!(make_initializer: @slot(slot), @type_name($t), @munch_fields($($fields)*,), @acc(), ); - } + }; } Ok(__InitOk) } @@ -1168,8 +1168,8 @@ macro_rules! __init_internal { @acc($($acc:tt)*), ) => { // Endpoint, nothing more to munch, create the initializer. - // Since we are in the `if false` branch, this will never get executed. We abuse `slot` to - // get the correct type inference here: + // Since we are in the closure that is never called, this will never get executed. + // We abuse `slot` to get the correct type inference here: unsafe { ::core::ptr::write($slot, $t { $($acc)*