vlang

How can I call the C routine 'lseek'?

How can I call the C routines lseek or ftell or fseek? I tried this (macos 10.12.6):

import os
#flag -lsystem
#include <unistd.h>

seeker.v:150:11: error: unknown function: C.lseek 
  148 | // tell returns the current file position
  149 | fn (f os.File) tell() int {
  150 |     return C.lseek(f.fd, 0, C.SEEK_CUR)
  151 | }
Solution

  • You have to declare the C functions before you use them !

    fn C.lseek(fd, offset, whence int)

    This allows V to know the parameters of the function, and type check them.