Undefined Behavior with custom allocator and Box | Rust Programming Language Community | Page 1

amber bobcat Jul 27, 2022, 12:21 AM

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MIRI is telling me my code has undefined behavior based on Stacked Borrows rules, and I am quite out of my depth. Is this code wrong? And if so, how do i fix it?

📎 errorlog.rs

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here's the whole source

📎 lib.rs

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and here's the repo https://github.com/OliveIsAWord/allocator

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i'm using the paste crate to create unique identifiers but other than that, no external crates

haughty breach Jul 27, 2022, 1:00 AM

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let ptr = unsafe { NonNull::new_unchecked(self.stack.as_ptr().add(aligned) as *mut _) }; isn’t the problem here that you’re casting a *const T to *mut?

amber bobcat Jul 27, 2022, 1:10 AM

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oh dear you are absolutely correct, that fixed it

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i knew that returned a const pointer, but i missed it because NonNull::as_ptr returns a mut pointer

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thanks!

amber bobcat Jul 27, 2022, 1:38 AM

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hello hello, one bug down, and another to take its place

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slightly fixed source code

📎 lib.rs

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new error

📎 errorlog.rs

#Undefined Behavior with custom allocator and Box