The handling of the "tail" of the key (the last < 32 bytes) is slightly odd (the "if (l & 1) { mix 1 byte of key }" happens before 8-byte chunks and 2-byte chunks), but if it passes SMHasher it should be fine for general use.
Author of the post writes:
> I kept making changes until the tests passed.
If SMHasher has become a target, shouldn't it be considered a bad measure now? [1]
OTOH, I would expect that tests for hashing and random number generation in particular would be naturally resistant to overfitting, due to the nature of the problem. But I'm not an expert at this topic, so I'd love to hear someone else's take on that
When a hash function has weak mixing they tend to fail catastrophically on one of those key sets, so you can think of SMHasher as more like "attempts to test the hash function to the point of failure" instead of a "target" as described in Goodhart's Law.