* dtable.cc (dtable::dup_worker): Add comment explaining why refcnt isn't

incremented here.
(dtable::dup3): Simplify slightly.  Add comment.
* syscalls.cc (dup3): Increment refcnt here, similarly to dup2.

winsup/cygwin/syscalls.cc

@@ -161,8 +161,9 @@ dup3 (int oldfd, int newfd, int flags)
       set_errno (cfd < 0 ? EBADF : EINVAL);
       res = -1;
     }
-  else
-    res = cygheap->fdtab.dup3 (oldfd, newfd, flags);
+  else if ((res = cygheap->fdtab.dup3 (oldfd, newfd, flags)) == newfd)
+    cygheap->fdtab[newfd]->refcnt (1);
+
   syscall_printf ("%R = dup3(%d, %d, %p)", res, oldfd, newfd, flags);
   return res;
 }