erroneous assert encoded >= 0xf001

[k4lizen]

This one:

rustix/src/backend/linux_raw/io/errno.rs

Line 91 in cd95201

assert!(encoded >= 0xf001);

Is causing issues here: Smithay/smithay#1725 . I think the issue is that the assert fails when errno is 0, because wrapping_neg puts it back to 0. This is also what is shown in my corefile of the crash

[sunfishcode]

That code in rustix is assuming that the argument value is the value of an error code from a syscall which has failed, which would always be non-zero. Admittedly it's not made explicit in the documentatoon; that's something we should fix.

Do you know what's returning an Err with a type that returns a zero value for its error code?

[k4lizen]

I guess this?

https://github.com/Smithay/smithay/blob/cb90ea06c6cb89f47f65a8cdf71d78917707f822/src/backend/session/libseat.rs#L145-L150

I can't recover that from my crash though since I don't have those symbols, it's what @YaLTeR says in his report of the crash