From 1cdd9b407db0f842387dc5e4f18e6563dcd87b18 Mon Sep 17 00:00:00 2001
From: Russ Cox <rsc@golang.org>
Date: Thu, 6 Nov 2014 09:36:51 -0500
Subject: [PATCH] os: document that users of Fd should keep f alive

Fixes #9046.

LGTM=r
R=r
CC=golang-codereviews
https://golang.org/cl/162680043
---
 src/os/file_plan9.go   | 3 ++-
 src/os/file_unix.go    | 1 +
 src/os/file_windows.go | 1 +
 3 files changed, 4 insertions(+), 1 deletion(-)

diff --git a/src/os/file_plan9.go b/src/os/file_plan9.go
index 5efc2a4f1db..132594eede9 100644
--- a/src/os/file_plan9.go
+++ b/src/os/file_plan9.go
@@ -25,7 +25,8 @@ type file struct {
 	dirinfo *dirInfo // nil unless directory being read
 }
 
-// Fd returns the integer Unix file descriptor referencing the open file.
+// Fd returns the integer Plan 9 file descriptor referencing the open file.
+// The file descriptor is valid only until f.Close is called or f is garbage collected.
 func (f *File) Fd() uintptr {
 	if f == nil {
 		return ^(uintptr(0))
diff --git a/src/os/file_unix.go b/src/os/file_unix.go
index f59d563e697..ff4fc7d12e8 100644
--- a/src/os/file_unix.go
+++ b/src/os/file_unix.go
@@ -29,6 +29,7 @@ type file struct {
 }
 
 // Fd returns the integer Unix file descriptor referencing the open file.
+// The file descriptor is valid only until f.Close is called or f is garbage collected.
 func (f *File) Fd() uintptr {
 	if f == nil {
 		return ^(uintptr(0))
diff --git a/src/os/file_windows.go b/src/os/file_windows.go
index 3b5519390ba..2a90a50559d 100644
--- a/src/os/file_windows.go
+++ b/src/os/file_windows.go
@@ -36,6 +36,7 @@ type file struct {
 }
 
 // Fd returns the Windows handle referencing the open file.
+// The handle is valid only until f.Close is called or f is garbage collected.
 func (file *File) Fd() uintptr {
 	if file == nil {
 		return uintptr(syscall.InvalidHandle)