Re: FFI questions - VapourSynth

[yglukhov]

Proc types are {.closure.} by default i.e. fat pointer. You want {.cdecl.} 
instead: 
    
    
    type:
       VSAPI*  {.importc: "struct VSAPI", header: headerVapourSynth, bycopy.} = 
object
           createCore*: proc(threads:cint):ptr VSCore {.cdecl.}
           ....
    
    
    Run

Also as long as you exactly match the struct layout to that of C, you don't 
need importc and header pragmas for the type, and thus don't depend on the 
headers at all.