code review 4628045: os: Change Waitmsg.String() to operate on pointer.

src/pkg/os/os_test.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_test
 
 import (
         "bytes"
         "fmt"
         "io"
@@ skipping 1024 matching lines @@
         if err != nil {
                 t.Fatal("stat failed:", err)
         }
 
         // Stat of path+"/" should succeed too.
         _, err = Stat(path + "/")
         if err != nil {
                 t.Fatal("stat failed:", err)
         }
 }
+
+func TestNilWaitmsgString(t *testing.T) {
+        var w *Waitmsg
+        s := w.String()
+        if s != "<nil>" {
+                t.Errorf("(*Waitmsg)(nil).String() = %q, want %q", s, "<nil>")
+        }
+}