1// Copyright 2020 The Go Authors. All rights reserved.
2// Use of this source code is governed by a BSD-style
3// license that can be found in the LICENSE file.
4
5//go:build ignore
6
7// This is a test program that verifies that it can read from
8// descriptor 3 and that no other descriptors are open.
9// This is not done via TestHelperProcess and GO_EXEC_TEST_PID
10// because we want to ensure that this program does not use cgo,
11// because C libraries can open file descriptors behind our backs
12// and confuse the test. See issue 25628.
13package main
14
15import (
16	"fmt"
17	"internal/poll"
18	"io"
19	"os"
20	"os/exec"
21	"os/exec/internal/fdtest"
22	"runtime"
23	"strings"
24)
25
26func main() {
27	fd3 := os.NewFile(3, "fd3")
28	defer fd3.Close()
29
30	bs, err := io.ReadAll(fd3)
31	if err != nil {
32		fmt.Printf("ReadAll from fd 3: %v\n", err)
33		os.Exit(1)
34	}
35
36	// Now verify that there are no other open fds.
37	// stdin == 0
38	// stdout == 1
39	// stderr == 2
40	// descriptor from parent == 3
41	// All descriptors 4 and up should be available,
42	// except for any used by the network poller.
43	for fd := uintptr(4); fd <= 100; fd++ {
44		if poll.IsPollDescriptor(fd) {
45			continue
46		}
47
48		if !fdtest.Exists(fd) {
49			continue
50		}
51
52		fmt.Printf("leaked parent file. fdtest.Exists(%d) got true want false\n", fd)
53
54		fdfile := fmt.Sprintf("/proc/self/fd/%d", fd)
55		link, err := os.Readlink(fdfile)
56		fmt.Printf("readlink(%q) = %q, %v\n", fdfile, link, err)
57
58		var args []string
59		switch runtime.GOOS {
60		case "plan9":
61			args = []string{fmt.Sprintf("/proc/%d/fd", os.Getpid())}
62		case "aix", "solaris", "illumos":
63			args = []string{fmt.Sprint(os.Getpid())}
64		default:
65			args = []string{"-p", fmt.Sprint(os.Getpid())}
66		}
67
68		// Determine which command to use to display open files.
69		ofcmd := "lsof"
70		switch runtime.GOOS {
71		case "dragonfly", "freebsd", "netbsd", "openbsd":
72			ofcmd = "fstat"
73		case "plan9":
74			ofcmd = "/bin/cat"
75		case "aix":
76			ofcmd = "procfiles"
77		case "solaris", "illumos":
78			ofcmd = "pfiles"
79		}
80
81		cmd := exec.Command(ofcmd, args...)
82		out, err := cmd.CombinedOutput()
83		if err != nil {
84			fmt.Fprintf(os.Stderr, "%s failed: %v\n", strings.Join(cmd.Args, " "), err)
85		}
86		fmt.Printf("%s", out)
87		os.Exit(1)
88	}
89
90	os.Stdout.Write(bs)
91}
92