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>>> - $ptr.byte_sub(offset).cast::<$type>() >>> + ($field_ptr:expr, $Container:ty, $($fields:tt)*) => {{ >>> + let offset: usize = ::core::mem::offset_of!($Container, $($fields)*); >>> + let field_ptr = $field_ptr; >>> + let container_ptr = field_ptr.byte_sub(offset).cast::<$Container>(); >>> + if false { >> >> This jumped out at me. It's something that I'd like to recommend NOT >> doing, here or anywhere else, because: >> >> a) Anything of the form "if false" will get removed by any compiler >> worthy of the name, especially in kernel builds. > > The `if false` branch is used to trigger a compilation failure when the > macro is used incorrectly. The intent is that the compiler should > optimize it out. I don't think there's anything wrong with that pattern. OK...probably best to either encapsulate that, or at least comment it. I'm accustomed to seeing that pattern in cases where people expected the code to *not* get optimized out, so it triggers me. :) thanks, -- John Hubbard