On some websites, e.g. http://finprison.net, attohttpc fails with the following error:

Io Error: unexpected end of file

Curl also behaves weirdly for this particular website, but Firefox works fine, so it's probably a weird edge case.

13 websites out of the top million from Feb 3 Tranco list are affected.

Tested using this code. Test tool output from all affected websites: atto-unexpected-eof.tar.gz