[go-nuts] Another issue with fork(2): is it a bug?

Dear gophers,

I use the risky fork(2) in my code. In the child, I found syscall.Getpid()
and C.getpid() return different result. It's demonstrated in the following
code.
On fedora 17, x86_64, it will return something like,
child process (syscall): pid 28354, ppid 28352
child process (C): pid 28352, ppid 28352
Child exits 0

I'm not sure if it can be taken as a bug?

(The background problem: my requirement is an RPC server to serve some
requests(run some code) on behalf different user. I would like to
circumvent the fork(2) usage but found no elegant way by myself. Do I have
to invoke another program, such as su, to accomplish the work in such a
scenario? (I want to avoid it because I have to add command line interface
for each piece of code.))


-- demo code --

package main

// #include <unistd.h>
import "C"

import (
   "fmt"
   "log"
   "syscall"
)

func main() {
   r1, _, err := syscall.RawSyscall(syscall.SYS_FORK, 0, 0, 0)
   //r1, _, err := syscall.Syscall(syscall.SYS_FORK, 0, 0, 0)
   if err != 0 {
     log.Fatal(err)
   }
   // r1 := C.fork()

   if r1 != 0 {
     var wstatus syscall.WaitStatus
     pid1, err := syscall.Wait4(int(r1), &wstatus, 0, nil)
     if err != nil || pid1 < 0 {
       log.Fatal(err)
     }
     exitStatus := wstatus.ExitStatus()
     fmt.Printf("Child exits %d\n", exitStatus)
     return
   }

   // child
   fmt.Printf("child process (syscall): pid %d, ppid %d\n",
     syscall.Getpid(), syscall.Getppid())
   fmt.Printf("child process (C): pid %d, ppid %d\n",
     C.getpid(), C.getppid())
}