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// Copyright 2020 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.
// +build ignore
// This is a test program that verifies that it can read from
// descriptor 3 and that no other descriptors are open.
// This is not done via TestHelperProcess and GO_WANT_HELPER_PROCESS
// because we want to ensure that this program does not use cgo,
// because C libraries can open file descriptors behind our backs
// and confuse the test. See issue 25628.
package main
import (
"fmt"
"internal/poll"
"io"
"os"
"os/exec"
"runtime"
"strings"
)
func main() {
fd3 := os.NewFile(3, "fd3")
bs, err := io.ReadAll(fd3)
if err != nil {
fmt.Printf("ReadAll from fd 3: %v\n", err)
os.Exit(1)
}
// Now verify that there are no other open fds.
// stdin == 0
// stdout == 1
// stderr == 2
// descriptor from parent == 3
// All descriptors 4 and up should be available,
// except for any used by the network poller.
var files []*os.File
for wantfd := uintptr(4); wantfd <= 100; wantfd++ {
if poll.IsPollDescriptor(wantfd) {
continue
}
f, err := os.Open(os.Args[0])
if err != nil {
fmt.Printf("error opening file with expected fd %d: %v", wantfd, err)
os.Exit(1)
}
if got := f.Fd(); got != wantfd {
fmt.Printf("leaked parent file. fd = %d; want %d\n", got, wantfd)
fdfile := fmt.Sprintf("/proc/self/fd/%d", wantfd)
link, err := os.Readlink(fdfile)
fmt.Printf("readlink(%q) = %q, %v\n", fdfile, link, err)
var args []string
switch runtime.GOOS {
case "plan9":
args = []string{fmt.Sprintf("/proc/%d/fd", os.Getpid())}
case "aix":
args = []string{fmt.Sprint(os.Getpid())}
default:
args = []string{"-p", fmt.Sprint(os.Getpid())}
}
// Determine which command to use to display open files.
ofcmd := "lsof"
switch runtime.GOOS {
case "dragonfly", "freebsd", "netbsd", "openbsd":
ofcmd = "fstat"
case "plan9":
ofcmd = "/bin/cat"
case "aix":
ofcmd = "procfiles"
}
cmd := exec.Command(ofcmd, args...)
out, err := cmd.CombinedOutput()
if err != nil {
fmt.Fprintf(os.Stderr, "%s failed: %v\n", strings.Join(cmd.Args, " "), err)
}
fmt.Printf("%s", out)
os.Exit(1)
}
files = append(files, f)
}
for _, f := range files {
f.Close()
}
// Referring to fd3 here ensures that it is not
// garbage collected, and therefore closed, while
// executing the wantfd loop above. It doesn't matter
// what we do with fd3 as long as we refer to it;
// closing it is the easy choice.
fd3.Close()
os.Stdout.Write(bs)
}
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