redis-cell | Redis module that provides rate | Command Line Interface library

You don't, at least not yet, and I'd wager probably never.

To be able to do this, you'd need two key abilities, both of which are outside of your control:

1. Redis needs to provide a function that accepts a va_list argument, not just a ....

   It's strange that Redis doesn't already provide such a function, but perhaps this is a sign that other people implementing modules avoid the problem entirely.

2. Rust needs to provide a way to construct the va_list argument.

   While it looks like RFC 2137 will introduce a VaList type, the proposed API does not provide a way to create one or set values in it.

Note that you can't do what you want, even in C (at least not easily or portably).

What can you do instead? Assuming that you are implementing the code that consumes the variadic arguments, you can remove the variation from your call. A collection of items in C is just a pointer and a length, so pass that instead: