Fix off-by-one error causing slice::sort to abort the program

[uellenberg]

Fixes #136103.
Based on the analysis by @jonathan-gruber-jg and @orlp.

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[workingjubilee]

r? libs

[orlp]

Looks good to me, @Voultapher any thoughts?

[Voultapher]

I'm suggesting minor changes, the fix itself looks good.

[uellenberg]

Some of the comments mention MIN_SMALL_SORT_SCRATCH_LEN but I don't see that actually defined anywhere, nor used in any code. Was this renamed at some point, or am I missing something?

[Voultapher]

LGTM, thanks for the fix @uellenberg

[Voultapher]

Some of the comments mention MIN_SMALL_SORT_SCRATCH_LEN but I don't see that actually defined anywhere, nor used in any code. Was this renamed at some point, or am I missing something?

In the original driftsort repository this constant was defined as pub const MIN_SMALL_SORT_SCRATCH_LEN: usize = i32::SMALL_SORT_THRESHOLD + 16;, while merging the driftsort and ipnsort code bases it was renamed to SMALL_SORT_GENERAL_SCRATCH_LEN. I think this kind of coment fixup doesn't need a separate PR, so feel free to do it here.

[Voultapher]

Could we maybe change the PR title, crash usually suggests UB, here we are just running into assert style function preconditions, in this case not using panics and instead abort to save on binary-size.

[Mark-Simulacrum]

@bors r+

[bors]

📌 Commit 1565254 has been approved by Mark-Simulacrum

It is now in the queue for this repository.