code review 4029053: os: implement new Process api

src/pkg/os/exec_unix.go

 // Copyright 2009 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
 package os
 
-import "syscall"
+import (
+        "runtime"
+        "syscall"
+)
 
 // Options for Wait.
 const (
         WNOHANG   = syscall.WNOHANG   // Don't wait if no process has exited.
         WSTOPPED  = syscall.WSTOPPED  // If set, status of stopped subprocesses is also reported.
         WUNTRACED = syscall.WUNTRACED // Usually an alias for WSTOPPED.
         WRUSAGE   = 1 << 20           // Record resource usage.
 )
 
 // WRUSAGE must not be too high a bit, to avoid clashing with Linux's
 // WCLONE, WALL, and WNOTHREAD flags, which sit in the top few bits of
 // the options
 
 // Wait waits for the Process to exit or stop, and then returns a
 // Waitmsg describing its status and an Error, if any. The options
 // (WNOHANG etc.) affect the behavior of the Wait call.
 func (p *Process) Wait(options int) (w *Waitmsg, err Error) {
+        if p.Pid == -1 {
+                return nil, EINVAL
+        }
         var status syscall.WaitStatus
         var rusage *syscall.Rusage
         if options&WRUSAGE != 0 {
                 rusage = new(syscall.Rusage)
                 options ^= WRUSAGE
         }
         pid1, e := syscall.Wait4(p.Pid, &status, options, rusage)
         if e != 0 {
                 return nil, NewSyscallError("wait", e)
         }
         w = new(Waitmsg)
         w.Pid = pid1
         w.WaitStatus = status
         w.Rusage = rusage
         return w, nil
 }
 
-// Release resources associated with the Process,
-// rendering it unusable. It returns an Error, if any.
+// Release releases any resources associated with the Process.
 func (p *Process) Release() Error {
         // NOOP for unix.
+        p.Pid = -1
+        // no need for a finalizer anymore
+        runtime.SetFinalizer(p, nil)
         return nil
 }
 
 // FindProcess looks for a running process by its pid.
 // The Process it returns can be used to obtain information
 // about the underlying operating system process.
-// If the process cannot be found, an error is returned.
 func FindProcess(pid int) (p *Process, err Error) {
         // NOOP for unix.
-        return &Process{pid, 0}, nil
+        return newProcess(pid, 0), nil
 }