Bulild fails under clang++ 10 which comes with Ubuntu 20.04 LTS which is to be released on April 23.
There are many implicit conversion errors like this:
error: implicit conversion from 'size_t' (aka 'unsigned long') to 'double' may lose precision
$ clang++ --version
clang version 10.0.0-2ubuntu2
Thread model: posix
$ lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description: Ubuntu Focal Fossa (development branch)