Misaligned Pointer panic in the Paging Introduction post about blog_os HOT 8 CLOSED

I would like to comment that I am also running into this issue.

I so far always swapped 0xdeadbeaf for 0xdeadbea0 since that is a multiple of 0x4.

While that works, I am worried I might run into bigger problems later down the line.

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Hi, maybe the read_unaligned and the write_unaligned could be used in this case. I have not encountered this error so far.
Here are some links:
https://doc.rust-lang.org/std/ptr/fn.read_unaligned.html
https://doc.rust-lang.org/std/ptr/fn.write_unaligned.html

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@carloalbertogiordano
Thanks, but those can't be used as the os doesn't contain, or support, the std crate

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These functions are re-exports from libcore, which is supported. So you can write core::ptr::read_unaligned and core::ptr::write_unaligned.

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Okay, thanks @bjorn3 ! I haven't tried it, but I think it will work. I'll leave this open for now though, as it should be working without read/write_unaligned

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@bjorn3 Can confirm. core::ptr::write_unaligned does work.
But, any idea as to why the standard syntax doesn't work anymore?

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Dereferencing unaligned pointers is UB. Previously if you were lucky the compiler wouldn't miscompile it, but to catch this UB, rustc recently added a compiler pass when debug assertions are enabled which adds code to check on every pointer dereference if the pointer is aligned or not and if not aborts. This helps finding this UB.

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Okay, so that's just how rustc compiles it now. Thanks!

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