Dave Harris wrote:

In-Reply-To: <d1na66$6p2$1@sea.gmane.org> daniel@calamity.org.uk (Daniel James) wrote (abridged):

...

...

5. change implementation of hash values for pointers so undefined behavior is gone (and consider adding x + (x >> 3) )

I'm going to do that.

Is it worth considering using x + x / sizeof(*p) instead?

This will not work for incomplete types, including void. I'd prefer equal hash_values for an incomplete T*, complete T*, and void* with the same value. We'll lose one potential bit of enthropy when alignof(x) == 16, but this seems sufficiently rare in practice.