function abs() is panicking on `min_value`

[spremel]

The documentation states that abs(::MIN) returns ::MIN. However, the current behavior is to panic on integer min value.
This is easily reproducible on the stable Rust playground.

https://play.rust-lang.org/?version=stable&mode=debug&edition=2024&gist=447346fe7ffc16a8c46eb694f30138ac

Thanks

[crop2000]

Unrelated to num traits. (A max is smaller then a potential abs(min))

[cuviper]

Oof, this is going way back. It's true that the documentation says that MIN.abs() returns MIN, and once upon a time this was always the case for the signed integer types. However, Rust 1.1 changed this:

https://doc.rust-lang.org/stable/releases.html#version-110-2015-06-25

In accordance with Rust’s policy on arithmetic overflow abs now panics on overflow when debug assertions are enabled.

So for a very long time, the behavior has been that MIN panics with debug assertions (default in debug mode) and wraps back to MIN otherwise (as in release mode). We should update the documentation, though without being too prescriptive about how third-party types may handle this.

(This predates the num-traits crate itself, but these traits were split from the num crate which existed before Rust 1.0, originally split out from the standard library.)

[spremel]

Thanks for clarifying this.

That's what I thought, I was mostly confused by the documentation that was saying that MIN is the result to expect. Since it is bit-wise arithmetically correct, that would have been an "acceptable" implementation of abs.

This can be closed then.