Please note that the above link has been claimed by squatters and isn’t the right link for CCAN anymore! The maintainer suggests [1] just using the GitHub repo [2] instead.
[1] https://lists.ozlabs.org/pipermail/ccan/2022-September/00141...
See also ccan: https://github.com/rustyrussell/ccan
Along the same lines, there is also CCAN.
http://ccodearchive.net/list.html
https://github.com/rustyrussell/ccan
And GMP for arbitrary precision math (integers and floating point numbers).