Fixed UB

[jorgecarleitao]

This PR addresses an error whereby running cargo miri test fails. This is caused because the mut pointer gets invalidated when a non-mut pointer is created.

This is a backport of rust-lang/rust#85610 (we could consider using it, since it is stable).

[jorgecarleitao]

This was initially found here: https://github.com/jorgecarleitao/arrow2/runs/4731494362?check_suite_focus=true .

[jorgecarleitao]

@WanzenBug , if you no longer have time to maintain this crate, would it be ok for me to fork it and release in crates with the above fix (or alternatively, give me write permissions to do so?).

This crate is quite relevant for the ecosystem, and it would be nice to be able to offer continuity to it.

[WanzenBug]

Sorry, this PR must have been drowned out when catching up my notifications after Christmas.

I'll still merge PRs if any issues are noticed, but hopefully everyone will just use the version from the stdlib. I should probably reference that in the README :)

[jorgecarleitao]

fwiw, this crate is pretty much used - libflate depends on it, and pretty much the whole data engineering stack depends on that :)

[WanzenBug]

Yeah, my most popular crate, completely by accident, because I implemented some-ones RFC idea.