Unfortunately C varargs and Nim varargs are quite different from each other. C varargs are basically just a pointer to somewhere in memory and it's up to the callee to handle this collection of arbitrary data (typically done by C macros which will advance the pointer depending on the type you "took out" of the collection). Nim varargs can really only have one type and (I believe) is passed along as something more sequence like.
As another gotcha the `varargs` pragma [take a variable number of parameters after the last specified parameter.](https://nim-lang.org/docs/manual.html#foreign-function-interface-varargs-pragma), so your two definitions does not mean the same thing. In order to create a runtime dynamic list compatible with va_list (the type used by C varargs) you have to pack the arguments into one contiguous region of memory (with the correct padding) and pass a pointer of that to the function. Of course if you're only looking for a one-of or to generate this call with a macro then simply defining an object with all your data in order should suffice.
