Repository navigation
ffi :variadic? true generated function do not use all arguments supplied #449
Description
I get unexpected results when using it.
As an example here is what it outputs from "printf" (defined in stdlib as (def printf (ffi-fn libc "printf" [CCharP] CInt :variadic? true))):
user => (printf "a" "b" "c")
a
It seems everything after the 1st argument is ignored.
Activity
heyLu commentedon Nov 15, 2015
Yes, #420 was about the same problem. As I said there, I'm not sure if our FFI can handle the full signature of
printf. It seems to support multiple arguments to printf and passes them, but I don't know what happens after that.I went looking in
pixie/vm/libs/ffi.py, and looked forvariadic?there. I think it doesn't actually convert the additional arguments toprintf, even though it allocates space for them, it does not convert the additional arguments. (The problem seems to be that_arg_typesis used to convert the arguments, but that's just the[CCharP]from the signature, and doesn't include the (unknown) types for the optional arguments.)mpenet commentedon Nov 15, 2015
There is a missing piece yes. I tried briefly to follow what's happening in ffi.py as well but that's still a bit vague to me. I guess that's something @halgari could look into when he gets some time.