https://github.com/tkaitchuck/aHash/pull/196 bumped the MSRV of
`ahash` in a patch release, which makes it rather difficult for us
to have it as a dependency.
Further, it seems that `ahash` hasn't been particularly robust in
the past, notably
https://github.com/tkaitchuck/aHash/issues/163 and
https://github.com/tkaitchuck/aHash/issues/166.
Luckily, `core` provides `SipHasher` even on no-std (sadly its
SipHash-2-4 unlike the SipHash-1-3 used by the `DefaultHasher` in
`std`). Thus, we drop the `ahash` dependency entirely here and
simply wrap `SipHasher` for our `no-std` HashMaps.
In the next commit we'll drop the `ahash` dependency in favor of
directly calling `getrandom` to seed our hash tables. However,
we'd like to depend on `getrandom` only on certain platforms *and*
only when certain features (no-std) are set.
This introduces an indirection crate to do so, allowing us to
depend on it only when `no-std` is set but only depending on
`getrandom` on platforms which it supports.
While this isn't expected to materially improve performance, it
does get us ahash 0.8, which allows us to reduce fuzzing
randomness, making our fuzzers much happier.
Sadly, by default `ahash` no longer tries to autodetect a
randomness source, so we cannot simply rely on `hashbrown` to do
randomization for us, but rather have to also explicitly depend on
`ahash`.
We are intending to release without having completed our async
signing logic, which sadly means we need to cfg-gate it to ensure
we restore the previous state of panicking on signer errors, rather
than putting us in a stuck state with no way to recover.
Here we add a new `async_signing` cfg flag and use it to gate all
the new logic from #2558 effectively reverting commits
1da29290e7 through
014a336e59.
Rust is fairly relaxed in checking the validity of arguments
passed to #[cfg]. While it should probably be more strict when
checking features, it cannot be strict when checking loose cfg
tags, because those can be anything and are simply passed to rustc
via unconstrained arguments.
Thus, we do it for rustc manually, but scanning all our source and
checking that all our cfg tags match a known cfg tag.
Fixes#2184
