Hashmap raw_entry crash

[sgodwincs]

While trying out the experimental hashmap raw entry API, I found that the following code crashes

#![feature(hash_raw_entry)]

use std::collections::HashMap;

fn main() {
    let map: HashMap<&str, &str> = HashMap::new();
    map.raw_entry().search_bucket(0, |_| false);
}

While the corresponding version using raw_entry_mut does not. I'd expect it to return None in this case since the map doesn't even have any items.

rustc 1.32.0-nightly (f1e2fa8 2018-11-20)

[steveklabnik]

I just double checked, and this is indeed a segfault, not a panic.

[sgodwincs]

This only seems to happen when the capacity of the hashmap is 0. Using HashMap::with_capacity(1) avoids the problem.

[sfackler]

cc #56167

[Amanieu]

cc @gankro @fintelia

[Amanieu]

RawEntry is calling search_hashed_nonempty on an empty table. RawEntryMut does the same thing, but calls reserve(1) first so it's fine.

[kpp]

There is no method ::search_bucket anymore.

[Amanieu]

The crash doesn't happen any more since the switch to hashbrown.