Source file src/os/exec/exec_test.go

     1  // Copyright 2009 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  // Use an external test to avoid os/exec -> net/http -> crypto/x509 -> os/exec
     6  // circular dependency on non-cgo darwin.
     7  
     8  package exec_test
     9  
    10  import (
    11  	"bufio"
    12  	"bytes"
    13  	"context"
    14  	"fmt"
    15  	"internal/poll"
    16  	"internal/testenv"
    17  	"io"
    18  	"log"
    19  	"net"
    20  	"net/http"
    21  	"net/http/httptest"
    22  	"os"
    23  	"os/exec"
    24  	"path/filepath"
    25  	"runtime"
    26  	"strconv"
    27  	"strings"
    28  	"testing"
    29  	"time"
    30  )
    31  
    32  // haveUnexpectedFDs is set at init time to report whether any
    33  // file descriptors were open at program start.
    34  var haveUnexpectedFDs bool
    35  
    36  // unfinalizedFiles holds files that should not be finalized,
    37  // because that would close the associated file descriptor,
    38  // which we don't want to do.
    39  var unfinalizedFiles []*os.File
    40  
    41  func init() {
    42  	if os.Getenv("GO_WANT_HELPER_PROCESS") == "1" {
    43  		return
    44  	}
    45  	if runtime.GOOS == "windows" {
    46  		return
    47  	}
    48  	for fd := uintptr(3); fd <= 100; fd++ {
    49  		if poll.IsPollDescriptor(fd) {
    50  			continue
    51  		}
    52  		// We have no good portable way to check whether an FD is open.
    53  		// We use NewFile to create a *os.File, which lets us
    54  		// know whether it is open, but then we have to cope with
    55  		// the finalizer on the *os.File.
    56  		f := os.NewFile(fd, "")
    57  		if _, err := f.Stat(); err != nil {
    58  			// Close the file to clear the finalizer.
    59  			// We expect the Close to fail.
    60  			f.Close()
    61  		} else {
    62  			fmt.Printf("fd %d open at test start\n", fd)
    63  			haveUnexpectedFDs = true
    64  			// Use a global variable to avoid running
    65  			// the finalizer, which would close the FD.
    66  			unfinalizedFiles = append(unfinalizedFiles, f)
    67  		}
    68  	}
    69  }
    70  
    71  func helperCommandContext(t *testing.T, ctx context.Context, s ...string) (cmd *exec.Cmd) {
    72  	testenv.MustHaveExec(t)
    73  
    74  	cs := []string{"-test.run=TestHelperProcess", "--"}
    75  	cs = append(cs, s...)
    76  	if ctx != nil {
    77  		cmd = exec.CommandContext(ctx, os.Args[0], cs...)
    78  	} else {
    79  		cmd = exec.Command(os.Args[0], cs...)
    80  	}
    81  	cmd.Env = append(os.Environ(), "GO_WANT_HELPER_PROCESS=1")
    82  	return cmd
    83  }
    84  
    85  func helperCommand(t *testing.T, s ...string) *exec.Cmd {
    86  	return helperCommandContext(t, nil, s...)
    87  }
    88  
    89  func TestEcho(t *testing.T) {
    90  	bs, err := helperCommand(t, "echo", "foo bar", "baz").Output()
    91  	if err != nil {
    92  		t.Errorf("echo: %v", err)
    93  	}
    94  	if g, e := string(bs), "foo bar baz\n"; g != e {
    95  		t.Errorf("echo: want %q, got %q", e, g)
    96  	}
    97  }
    98  
    99  func TestCommandRelativeName(t *testing.T) {
   100  	testenv.MustHaveExec(t)
   101  
   102  	// Run our own binary as a relative path
   103  	// (e.g. "_test/exec.test") our parent directory.
   104  	base := filepath.Base(os.Args[0]) // "exec.test"
   105  	dir := filepath.Dir(os.Args[0])   // "/tmp/go-buildNNNN/os/exec/_test"
   106  	if dir == "." {
   107  		t.Skip("skipping; running test at root somehow")
   108  	}
   109  	parentDir := filepath.Dir(dir) // "/tmp/go-buildNNNN/os/exec"
   110  	dirBase := filepath.Base(dir)  // "_test"
   111  	if dirBase == "." {
   112  		t.Skipf("skipping; unexpected shallow dir of %q", dir)
   113  	}
   114  
   115  	cmd := exec.Command(filepath.Join(dirBase, base), "-test.run=TestHelperProcess", "--", "echo", "foo")
   116  	cmd.Dir = parentDir
   117  	cmd.Env = []string{"GO_WANT_HELPER_PROCESS=1"}
   118  
   119  	out, err := cmd.Output()
   120  	if err != nil {
   121  		t.Errorf("echo: %v", err)
   122  	}
   123  	if g, e := string(out), "foo\n"; g != e {
   124  		t.Errorf("echo: want %q, got %q", e, g)
   125  	}
   126  }
   127  
   128  func TestCatStdin(t *testing.T) {
   129  	// Cat, testing stdin and stdout.
   130  	input := "Input string\nLine 2"
   131  	p := helperCommand(t, "cat")
   132  	p.Stdin = strings.NewReader(input)
   133  	bs, err := p.Output()
   134  	if err != nil {
   135  		t.Errorf("cat: %v", err)
   136  	}
   137  	s := string(bs)
   138  	if s != input {
   139  		t.Errorf("cat: want %q, got %q", input, s)
   140  	}
   141  }
   142  
   143  func TestEchoFileRace(t *testing.T) {
   144  	cmd := helperCommand(t, "echo")
   145  	stdin, err := cmd.StdinPipe()
   146  	if err != nil {
   147  		t.Fatalf("StdinPipe: %v", err)
   148  	}
   149  	if err := cmd.Start(); err != nil {
   150  		t.Fatalf("Start: %v", err)
   151  	}
   152  	wrote := make(chan bool)
   153  	go func() {
   154  		defer close(wrote)
   155  		fmt.Fprint(stdin, "echo\n")
   156  	}()
   157  	if err := cmd.Wait(); err != nil {
   158  		t.Fatalf("Wait: %v", err)
   159  	}
   160  	<-wrote
   161  }
   162  
   163  func TestCatGoodAndBadFile(t *testing.T) {
   164  	// Testing combined output and error values.
   165  	bs, err := helperCommand(t, "cat", "/bogus/file.foo", "exec_test.go").CombinedOutput()
   166  	if _, ok := err.(*exec.ExitError); !ok {
   167  		t.Errorf("expected *exec.ExitError from cat combined; got %T: %v", err, err)
   168  	}
   169  	s := string(bs)
   170  	sp := strings.SplitN(s, "\n", 2)
   171  	if len(sp) != 2 {
   172  		t.Fatalf("expected two lines from cat; got %q", s)
   173  	}
   174  	errLine, body := sp[0], sp[1]
   175  	if !strings.HasPrefix(errLine, "Error: open /bogus/file.foo") {
   176  		t.Errorf("expected stderr to complain about file; got %q", errLine)
   177  	}
   178  	if !strings.Contains(body, "func TestHelperProcess(t *testing.T)") {
   179  		t.Errorf("expected test code; got %q (len %d)", body, len(body))
   180  	}
   181  }
   182  
   183  func TestNoExistExecutable(t *testing.T) {
   184  	// Can't run a non-existent executable
   185  	err := exec.Command("/no-exist-executable").Run()
   186  	if err == nil {
   187  		t.Error("expected error from /no-exist-executable")
   188  	}
   189  }
   190  
   191  func TestExitStatus(t *testing.T) {
   192  	// Test that exit values are returned correctly
   193  	cmd := helperCommand(t, "exit", "42")
   194  	err := cmd.Run()
   195  	want := "exit status 42"
   196  	switch runtime.GOOS {
   197  	case "plan9":
   198  		want = fmt.Sprintf("exit status: '%s %d: 42'", filepath.Base(cmd.Path), cmd.ProcessState.Pid())
   199  	}
   200  	if werr, ok := err.(*exec.ExitError); ok {
   201  		if s := werr.Error(); s != want {
   202  			t.Errorf("from exit 42 got exit %q, want %q", s, want)
   203  		}
   204  	} else {
   205  		t.Fatalf("expected *exec.ExitError from exit 42; got %T: %v", err, err)
   206  	}
   207  }
   208  
   209  func TestExitCode(t *testing.T) {
   210  	// Test that exit code are returned correctly
   211  	cmd := helperCommand(t, "exit", "42")
   212  	cmd.Run()
   213  	want := 42
   214  	if runtime.GOOS == "plan9" {
   215  		want = 1
   216  	}
   217  	got := cmd.ProcessState.ExitCode()
   218  	if want != got {
   219  		t.Errorf("ExitCode got %d, want %d", got, want)
   220  	}
   221  
   222  	cmd = helperCommand(t, "/no-exist-executable")
   223  	cmd.Run()
   224  	want = 2
   225  	if runtime.GOOS == "plan9" {
   226  		want = 1
   227  	}
   228  	got = cmd.ProcessState.ExitCode()
   229  	if want != got {
   230  		t.Errorf("ExitCode got %d, want %d", got, want)
   231  	}
   232  
   233  	cmd = helperCommand(t, "exit", "255")
   234  	cmd.Run()
   235  	want = 255
   236  	if runtime.GOOS == "plan9" {
   237  		want = 1
   238  	}
   239  	got = cmd.ProcessState.ExitCode()
   240  	if want != got {
   241  		t.Errorf("ExitCode got %d, want %d", got, want)
   242  	}
   243  
   244  	cmd = helperCommand(t, "cat")
   245  	cmd.Run()
   246  	want = 0
   247  	got = cmd.ProcessState.ExitCode()
   248  	if want != got {
   249  		t.Errorf("ExitCode got %d, want %d", got, want)
   250  	}
   251  
   252  	// Test when command does not call Run().
   253  	cmd = helperCommand(t, "cat")
   254  	want = -1
   255  	got = cmd.ProcessState.ExitCode()
   256  	if want != got {
   257  		t.Errorf("ExitCode got %d, want %d", got, want)
   258  	}
   259  }
   260  
   261  func TestPipes(t *testing.T) {
   262  	check := func(what string, err error) {
   263  		if err != nil {
   264  			t.Fatalf("%s: %v", what, err)
   265  		}
   266  	}
   267  	// Cat, testing stdin and stdout.
   268  	c := helperCommand(t, "pipetest")
   269  	stdin, err := c.StdinPipe()
   270  	check("StdinPipe", err)
   271  	stdout, err := c.StdoutPipe()
   272  	check("StdoutPipe", err)
   273  	stderr, err := c.StderrPipe()
   274  	check("StderrPipe", err)
   275  
   276  	outbr := bufio.NewReader(stdout)
   277  	errbr := bufio.NewReader(stderr)
   278  	line := func(what string, br *bufio.Reader) string {
   279  		line, _, err := br.ReadLine()
   280  		if err != nil {
   281  			t.Fatalf("%s: %v", what, err)
   282  		}
   283  		return string(line)
   284  	}
   285  
   286  	err = c.Start()
   287  	check("Start", err)
   288  
   289  	_, err = stdin.Write([]byte("O:I am output\n"))
   290  	check("first stdin Write", err)
   291  	if g, e := line("first output line", outbr), "O:I am output"; g != e {
   292  		t.Errorf("got %q, want %q", g, e)
   293  	}
   294  
   295  	_, err = stdin.Write([]byte("E:I am error\n"))
   296  	check("second stdin Write", err)
   297  	if g, e := line("first error line", errbr), "E:I am error"; g != e {
   298  		t.Errorf("got %q, want %q", g, e)
   299  	}
   300  
   301  	_, err = stdin.Write([]byte("O:I am output2\n"))
   302  	check("third stdin Write 3", err)
   303  	if g, e := line("second output line", outbr), "O:I am output2"; g != e {
   304  		t.Errorf("got %q, want %q", g, e)
   305  	}
   306  
   307  	stdin.Close()
   308  	err = c.Wait()
   309  	check("Wait", err)
   310  }
   311  
   312  const stdinCloseTestString = "Some test string."
   313  
   314  // Issue 6270.
   315  func TestStdinClose(t *testing.T) {
   316  	check := func(what string, err error) {
   317  		if err != nil {
   318  			t.Fatalf("%s: %v", what, err)
   319  		}
   320  	}
   321  	cmd := helperCommand(t, "stdinClose")
   322  	stdin, err := cmd.StdinPipe()
   323  	check("StdinPipe", err)
   324  	// Check that we can access methods of the underlying os.File.`
   325  	if _, ok := stdin.(interface {
   326  		Fd() uintptr
   327  	}); !ok {
   328  		t.Error("can't access methods of underlying *os.File")
   329  	}
   330  	check("Start", cmd.Start())
   331  	go func() {
   332  		_, err := io.Copy(stdin, strings.NewReader(stdinCloseTestString))
   333  		check("Copy", err)
   334  		// Before the fix, this next line would race with cmd.Wait.
   335  		check("Close", stdin.Close())
   336  	}()
   337  	check("Wait", cmd.Wait())
   338  }
   339  
   340  // Issue 17647.
   341  // It used to be the case that TestStdinClose, above, would fail when
   342  // run under the race detector. This test is a variant of TestStdinClose
   343  // that also used to fail when run under the race detector.
   344  // This test is run by cmd/dist under the race detector to verify that
   345  // the race detector no longer reports any problems.
   346  func TestStdinCloseRace(t *testing.T) {
   347  	cmd := helperCommand(t, "stdinClose")
   348  	stdin, err := cmd.StdinPipe()
   349  	if err != nil {
   350  		t.Fatalf("StdinPipe: %v", err)
   351  	}
   352  	if err := cmd.Start(); err != nil {
   353  		t.Fatalf("Start: %v", err)
   354  	}
   355  	go func() {
   356  		// We don't check the error return of Kill. It is
   357  		// possible that the process has already exited, in
   358  		// which case Kill will return an error "process
   359  		// already finished". The purpose of this test is to
   360  		// see whether the race detector reports an error; it
   361  		// doesn't matter whether this Kill succeeds or not.
   362  		cmd.Process.Kill()
   363  	}()
   364  	go func() {
   365  		// Send the wrong string, so that the child fails even
   366  		// if the other goroutine doesn't manage to kill it first.
   367  		// This test is to check that the race detector does not
   368  		// falsely report an error, so it doesn't matter how the
   369  		// child process fails.
   370  		io.Copy(stdin, strings.NewReader("unexpected string"))
   371  		if err := stdin.Close(); err != nil {
   372  			t.Errorf("stdin.Close: %v", err)
   373  		}
   374  	}()
   375  	if err := cmd.Wait(); err == nil {
   376  		t.Fatalf("Wait: succeeded unexpectedly")
   377  	}
   378  }
   379  
   380  // Issue 5071
   381  func TestPipeLookPathLeak(t *testing.T) {
   382  	// If we are reading from /proc/self/fd we (should) get an exact result.
   383  	tolerance := 0
   384  
   385  	// Reading /proc/self/fd is more reliable than calling lsof, so try that
   386  	// first.
   387  	numOpenFDs := func() (int, []byte, error) {
   388  		fds, err := os.ReadDir("/proc/self/fd")
   389  		if err != nil {
   390  			return 0, nil, err
   391  		}
   392  		return len(fds), nil, nil
   393  	}
   394  	want, before, err := numOpenFDs()
   395  	if err != nil {
   396  		// We encountered a problem reading /proc/self/fd (we might be on
   397  		// a platform that doesn't have it). Fall back onto lsof.
   398  		t.Logf("using lsof because: %v", err)
   399  		numOpenFDs = func() (int, []byte, error) {
   400  			// Android's stock lsof does not obey the -p option,
   401  			// so extra filtering is needed.
   402  			// https://golang.org/issue/10206
   403  			if runtime.GOOS == "android" {
   404  				// numOpenFDsAndroid handles errors itself and
   405  				// might skip or fail the test.
   406  				n, lsof := numOpenFDsAndroid(t)
   407  				return n, lsof, nil
   408  			}
   409  			lsof, err := exec.Command("lsof", "-b", "-n", "-p", strconv.Itoa(os.Getpid())).Output()
   410  			return bytes.Count(lsof, []byte("\n")), lsof, err
   411  		}
   412  
   413  		// lsof may see file descriptors associated with the fork itself,
   414  		// so we allow some extra margin if we have to use it.
   415  		// https://golang.org/issue/19243
   416  		tolerance = 5
   417  
   418  		// Retry reading the number of open file descriptors.
   419  		want, before, err = numOpenFDs()
   420  		if err != nil {
   421  			t.Log(err)
   422  			t.Skipf("skipping test; error finding or running lsof")
   423  		}
   424  	}
   425  
   426  	for i := 0; i < 6; i++ {
   427  		cmd := exec.Command("something-that-does-not-exist-executable")
   428  		cmd.StdoutPipe()
   429  		cmd.StderrPipe()
   430  		cmd.StdinPipe()
   431  		if err := cmd.Run(); err == nil {
   432  			t.Fatal("unexpected success")
   433  		}
   434  	}
   435  	got, after, err := numOpenFDs()
   436  	if err != nil {
   437  		// numOpenFDs has already succeeded once, it should work here.
   438  		t.Errorf("unexpected failure: %v", err)
   439  	}
   440  	if got-want > tolerance {
   441  		t.Errorf("number of open file descriptors changed: got %v, want %v", got, want)
   442  		if before != nil {
   443  			t.Errorf("before:\n%v\n", before)
   444  		}
   445  		if after != nil {
   446  			t.Errorf("after:\n%v\n", after)
   447  		}
   448  	}
   449  }
   450  
   451  func numOpenFDsAndroid(t *testing.T) (n int, lsof []byte) {
   452  	raw, err := exec.Command("lsof").Output()
   453  	if err != nil {
   454  		t.Skip("skipping test; error finding or running lsof")
   455  	}
   456  
   457  	// First find the PID column index by parsing the first line, and
   458  	// select lines containing pid in the column.
   459  	pid := []byte(strconv.Itoa(os.Getpid()))
   460  	pidCol := -1
   461  
   462  	s := bufio.NewScanner(bytes.NewReader(raw))
   463  	for s.Scan() {
   464  		line := s.Bytes()
   465  		fields := bytes.Fields(line)
   466  		if pidCol < 0 {
   467  			for i, v := range fields {
   468  				if bytes.Equal(v, []byte("PID")) {
   469  					pidCol = i
   470  					break
   471  				}
   472  			}
   473  			lsof = append(lsof, line...)
   474  			continue
   475  		}
   476  		if bytes.Equal(fields[pidCol], pid) {
   477  			lsof = append(lsof, '\n')
   478  			lsof = append(lsof, line...)
   479  		}
   480  	}
   481  	if pidCol < 0 {
   482  		t.Fatal("error processing lsof output: unexpected header format")
   483  	}
   484  	if err := s.Err(); err != nil {
   485  		t.Fatalf("error processing lsof output: %v", err)
   486  	}
   487  	return bytes.Count(lsof, []byte("\n")), lsof
   488  }
   489  
   490  func TestExtraFilesFDShuffle(t *testing.T) {
   491  	testenv.SkipFlaky(t, 5780)
   492  	switch runtime.GOOS {
   493  	case "windows":
   494  		t.Skip("no operating system support; skipping")
   495  	}
   496  
   497  	// syscall.StartProcess maps all the FDs passed to it in
   498  	// ProcAttr.Files (the concatenation of stdin,stdout,stderr and
   499  	// ExtraFiles) into consecutive FDs in the child, that is:
   500  	// Files{11, 12, 6, 7, 9, 3} should result in the file
   501  	// represented by FD 11 in the parent being made available as 0
   502  	// in the child, 12 as 1, etc.
   503  	//
   504  	// We want to test that FDs in the child do not get overwritten
   505  	// by one another as this shuffle occurs. The original implementation
   506  	// was buggy in that in some data dependent cases it would overwrite
   507  	// stderr in the child with one of the ExtraFile members.
   508  	// Testing for this case is difficult because it relies on using
   509  	// the same FD values as that case. In particular, an FD of 3
   510  	// must be at an index of 4 or higher in ProcAttr.Files and
   511  	// the FD of the write end of the Stderr pipe (as obtained by
   512  	// StderrPipe()) must be the same as the size of ProcAttr.Files;
   513  	// therefore we test that the read end of this pipe (which is what
   514  	// is returned to the parent by StderrPipe() being one less than
   515  	// the size of ProcAttr.Files, i.e. 3+len(cmd.ExtraFiles).
   516  	//
   517  	// Moving this test case around within the overall tests may
   518  	// affect the FDs obtained and hence the checks to catch these cases.
   519  	npipes := 2
   520  	c := helperCommand(t, "extraFilesAndPipes", strconv.Itoa(npipes+1))
   521  	rd, wr, _ := os.Pipe()
   522  	defer rd.Close()
   523  	if rd.Fd() != 3 {
   524  		t.Errorf("bad test value for test pipe: fd %d", rd.Fd())
   525  	}
   526  	stderr, _ := c.StderrPipe()
   527  	wr.WriteString("_LAST")
   528  	wr.Close()
   529  
   530  	pipes := make([]struct {
   531  		r, w *os.File
   532  	}, npipes)
   533  	data := []string{"a", "b"}
   534  
   535  	for i := 0; i < npipes; i++ {
   536  		r, w, err := os.Pipe()
   537  		if err != nil {
   538  			t.Fatalf("unexpected error creating pipe: %s", err)
   539  		}
   540  		pipes[i].r = r
   541  		pipes[i].w = w
   542  		w.WriteString(data[i])
   543  		c.ExtraFiles = append(c.ExtraFiles, pipes[i].r)
   544  		defer func() {
   545  			r.Close()
   546  			w.Close()
   547  		}()
   548  	}
   549  	// Put fd 3 at the end.
   550  	c.ExtraFiles = append(c.ExtraFiles, rd)
   551  
   552  	stderrFd := int(stderr.(*os.File).Fd())
   553  	if stderrFd != ((len(c.ExtraFiles) + 3) - 1) {
   554  		t.Errorf("bad test value for stderr pipe")
   555  	}
   556  
   557  	expected := "child: " + strings.Join(data, "") + "_LAST"
   558  
   559  	err := c.Start()
   560  	if err != nil {
   561  		t.Fatalf("Run: %v", err)
   562  	}
   563  	ch := make(chan string, 1)
   564  	go func(ch chan string) {
   565  		buf := make([]byte, 512)
   566  		n, err := stderr.Read(buf)
   567  		if err != nil {
   568  			t.Errorf("Read: %s", err)
   569  			ch <- err.Error()
   570  		} else {
   571  			ch <- string(buf[:n])
   572  		}
   573  		close(ch)
   574  	}(ch)
   575  	select {
   576  	case m := <-ch:
   577  		if m != expected {
   578  			t.Errorf("Read: '%s' not '%s'", m, expected)
   579  		}
   580  	case <-time.After(5 * time.Second):
   581  		t.Errorf("Read timedout")
   582  	}
   583  	c.Wait()
   584  }
   585  
   586  func TestExtraFiles(t *testing.T) {
   587  	if haveUnexpectedFDs {
   588  		// The point of this test is to make sure that any
   589  		// descriptors we open are marked close-on-exec.
   590  		// If haveUnexpectedFDs is true then there were other
   591  		// descriptors open when we started the test,
   592  		// so those descriptors are clearly not close-on-exec,
   593  		// and they will confuse the test. We could modify
   594  		// the test to expect those descriptors to remain open,
   595  		// but since we don't know where they came from or what
   596  		// they are doing, that seems fragile. For example,
   597  		// perhaps they are from the startup code on this
   598  		// system for some reason. Also, this test is not
   599  		// system-specific; as long as most systems do not skip
   600  		// the test, we will still be testing what we care about.
   601  		t.Skip("skipping test because test was run with FDs open")
   602  	}
   603  
   604  	testenv.MustHaveExec(t)
   605  	testenv.MustHaveGoBuild(t)
   606  
   607  	// This test runs with cgo disabled. External linking needs cgo, so
   608  	// it doesn't work if external linking is required.
   609  	testenv.MustInternalLink(t)
   610  
   611  	if runtime.GOOS == "windows" {
   612  		t.Skipf("skipping test on %q", runtime.GOOS)
   613  	}
   614  
   615  	// Force network usage, to verify the epoll (or whatever) fd
   616  	// doesn't leak to the child,
   617  	ln, err := net.Listen("tcp", "127.0.0.1:0")
   618  	if err != nil {
   619  		t.Fatal(err)
   620  	}
   621  	defer ln.Close()
   622  
   623  	// Make sure duplicated fds don't leak to the child.
   624  	f, err := ln.(*net.TCPListener).File()
   625  	if err != nil {
   626  		t.Fatal(err)
   627  	}
   628  	defer f.Close()
   629  	ln2, err := net.FileListener(f)
   630  	if err != nil {
   631  		t.Fatal(err)
   632  	}
   633  	defer ln2.Close()
   634  
   635  	// Force TLS root certs to be loaded (which might involve
   636  	// cgo), to make sure none of that potential C code leaks fds.
   637  	ts := httptest.NewUnstartedServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {}))
   638  	// quiet expected TLS handshake error "remote error: bad certificate"
   639  	ts.Config.ErrorLog = log.New(io.Discard, "", 0)
   640  	ts.StartTLS()
   641  	defer ts.Close()
   642  	_, err = http.Get(ts.URL)
   643  	if err == nil {
   644  		t.Errorf("success trying to fetch %s; want an error", ts.URL)
   645  	}
   646  
   647  	tf, err := os.CreateTemp("", "")
   648  	if err != nil {
   649  		t.Fatalf("TempFile: %v", err)
   650  	}
   651  	defer os.Remove(tf.Name())
   652  	defer tf.Close()
   653  
   654  	const text = "Hello, fd 3!"
   655  	_, err = tf.Write([]byte(text))
   656  	if err != nil {
   657  		t.Fatalf("Write: %v", err)
   658  	}
   659  	_, err = tf.Seek(0, io.SeekStart)
   660  	if err != nil {
   661  		t.Fatalf("Seek: %v", err)
   662  	}
   663  
   664  	tempdir := t.TempDir()
   665  	exe := filepath.Join(tempdir, "read3.exe")
   666  
   667  	c := exec.Command(testenv.GoToolPath(t), "build", "-o", exe, "read3.go")
   668  	// Build the test without cgo, so that C library functions don't
   669  	// open descriptors unexpectedly. See issue 25628.
   670  	c.Env = append(os.Environ(), "CGO_ENABLED=0")
   671  	if output, err := c.CombinedOutput(); err != nil {
   672  		t.Logf("go build -o %s read3.go\n%s", exe, output)
   673  		t.Fatalf("go build failed: %v", err)
   674  	}
   675  
   676  	// Use a deadline to try to get some output even if the program hangs.
   677  	ctx := context.Background()
   678  	if deadline, ok := t.Deadline(); ok {
   679  		// Leave a 20% grace period to flush output, which may be large on the
   680  		// linux/386 builders because we're running the subprocess under strace.
   681  		deadline = deadline.Add(-time.Until(deadline) / 5)
   682  
   683  		var cancel context.CancelFunc
   684  		ctx, cancel = context.WithDeadline(ctx, deadline)
   685  		defer cancel()
   686  	}
   687  
   688  	c = exec.CommandContext(ctx, exe)
   689  	var stdout, stderr bytes.Buffer
   690  	c.Stdout = &stdout
   691  	c.Stderr = &stderr
   692  	c.ExtraFiles = []*os.File{tf}
   693  	if runtime.GOOS == "illumos" {
   694  		// Some facilities in illumos are implemented via access
   695  		// to /proc by libc; such accesses can briefly occupy a
   696  		// low-numbered fd.  If this occurs concurrently with the
   697  		// test that checks for leaked descriptors, the check can
   698  		// become confused and report a spurious leaked descriptor.
   699  		// (See issue #42431 for more detailed analysis.)
   700  		//
   701  		// Attempt to constrain the use of additional threads in the
   702  		// child process to make this test less flaky:
   703  		c.Env = append(os.Environ(), "GOMAXPROCS=1")
   704  	}
   705  	err = c.Run()
   706  	if err != nil {
   707  		t.Fatalf("Run: %v\n--- stdout:\n%s--- stderr:\n%s", err, stdout.Bytes(), stderr.Bytes())
   708  	}
   709  	if stdout.String() != text {
   710  		t.Errorf("got stdout %q, stderr %q; want %q on stdout", stdout.String(), stderr.String(), text)
   711  	}
   712  }
   713  
   714  func TestExtraFilesRace(t *testing.T) {
   715  	if runtime.GOOS == "windows" {
   716  		t.Skip("no operating system support; skipping")
   717  	}
   718  	listen := func() net.Listener {
   719  		ln, err := net.Listen("tcp", "127.0.0.1:0")
   720  		if err != nil {
   721  			t.Fatal(err)
   722  		}
   723  		return ln
   724  	}
   725  	listenerFile := func(ln net.Listener) *os.File {
   726  		f, err := ln.(*net.TCPListener).File()
   727  		if err != nil {
   728  			t.Fatal(err)
   729  		}
   730  		return f
   731  	}
   732  	runCommand := func(c *exec.Cmd, out chan<- string) {
   733  		bout, err := c.CombinedOutput()
   734  		if err != nil {
   735  			out <- "ERROR:" + err.Error()
   736  		} else {
   737  			out <- string(bout)
   738  		}
   739  	}
   740  
   741  	for i := 0; i < 10; i++ {
   742  		if testing.Short() && i >= 3 {
   743  			break
   744  		}
   745  		la := listen()
   746  		ca := helperCommand(t, "describefiles")
   747  		ca.ExtraFiles = []*os.File{listenerFile(la)}
   748  		lb := listen()
   749  		cb := helperCommand(t, "describefiles")
   750  		cb.ExtraFiles = []*os.File{listenerFile(lb)}
   751  		ares := make(chan string)
   752  		bres := make(chan string)
   753  		go runCommand(ca, ares)
   754  		go runCommand(cb, bres)
   755  		if got, want := <-ares, fmt.Sprintf("fd3: listener %s\n", la.Addr()); got != want {
   756  			t.Errorf("iteration %d, process A got:\n%s\nwant:\n%s\n", i, got, want)
   757  		}
   758  		if got, want := <-bres, fmt.Sprintf("fd3: listener %s\n", lb.Addr()); got != want {
   759  			t.Errorf("iteration %d, process B got:\n%s\nwant:\n%s\n", i, got, want)
   760  		}
   761  		la.Close()
   762  		lb.Close()
   763  		for _, f := range ca.ExtraFiles {
   764  			f.Close()
   765  		}
   766  		for _, f := range cb.ExtraFiles {
   767  			f.Close()
   768  		}
   769  
   770  	}
   771  }
   772  
   773  // TestHelperProcess isn't a real test. It's used as a helper process
   774  // for TestParameterRun.
   775  func TestHelperProcess(*testing.T) {
   776  	if os.Getenv("GO_WANT_HELPER_PROCESS") != "1" {
   777  		return
   778  	}
   779  	defer os.Exit(0)
   780  
   781  	args := os.Args
   782  	for len(args) > 0 {
   783  		if args[0] == "--" {
   784  			args = args[1:]
   785  			break
   786  		}
   787  		args = args[1:]
   788  	}
   789  	if len(args) == 0 {
   790  		fmt.Fprintf(os.Stderr, "No command\n")
   791  		os.Exit(2)
   792  	}
   793  
   794  	cmd, args := args[0], args[1:]
   795  	switch cmd {
   796  	case "echo":
   797  		iargs := []interface{}{}
   798  		for _, s := range args {
   799  			iargs = append(iargs, s)
   800  		}
   801  		fmt.Println(iargs...)
   802  	case "echoenv":
   803  		for _, s := range args {
   804  			fmt.Println(os.Getenv(s))
   805  		}
   806  		os.Exit(0)
   807  	case "cat":
   808  		if len(args) == 0 {
   809  			io.Copy(os.Stdout, os.Stdin)
   810  			return
   811  		}
   812  		exit := 0
   813  		for _, fn := range args {
   814  			f, err := os.Open(fn)
   815  			if err != nil {
   816  				fmt.Fprintf(os.Stderr, "Error: %v\n", err)
   817  				exit = 2
   818  			} else {
   819  				defer f.Close()
   820  				io.Copy(os.Stdout, f)
   821  			}
   822  		}
   823  		os.Exit(exit)
   824  	case "pipetest":
   825  		bufr := bufio.NewReader(os.Stdin)
   826  		for {
   827  			line, _, err := bufr.ReadLine()
   828  			if err == io.EOF {
   829  				break
   830  			} else if err != nil {
   831  				os.Exit(1)
   832  			}
   833  			if bytes.HasPrefix(line, []byte("O:")) {
   834  				os.Stdout.Write(line)
   835  				os.Stdout.Write([]byte{'\n'})
   836  			} else if bytes.HasPrefix(line, []byte("E:")) {
   837  				os.Stderr.Write(line)
   838  				os.Stderr.Write([]byte{'\n'})
   839  			} else {
   840  				os.Exit(1)
   841  			}
   842  		}
   843  	case "stdinClose":
   844  		b, err := io.ReadAll(os.Stdin)
   845  		if err != nil {
   846  			fmt.Fprintf(os.Stderr, "Error: %v\n", err)
   847  			os.Exit(1)
   848  		}
   849  		if s := string(b); s != stdinCloseTestString {
   850  			fmt.Fprintf(os.Stderr, "Error: Read %q, want %q", s, stdinCloseTestString)
   851  			os.Exit(1)
   852  		}
   853  		os.Exit(0)
   854  	case "exit":
   855  		n, _ := strconv.Atoi(args[0])
   856  		os.Exit(n)
   857  	case "describefiles":
   858  		f := os.NewFile(3, fmt.Sprintf("fd3"))
   859  		ln, err := net.FileListener(f)
   860  		if err == nil {
   861  			fmt.Printf("fd3: listener %s\n", ln.Addr())
   862  			ln.Close()
   863  		}
   864  		os.Exit(0)
   865  	case "extraFilesAndPipes":
   866  		n, _ := strconv.Atoi(args[0])
   867  		pipes := make([]*os.File, n)
   868  		for i := 0; i < n; i++ {
   869  			pipes[i] = os.NewFile(uintptr(3+i), strconv.Itoa(i))
   870  		}
   871  		response := ""
   872  		for i, r := range pipes {
   873  			ch := make(chan string, 1)
   874  			go func(c chan string) {
   875  				buf := make([]byte, 10)
   876  				n, err := r.Read(buf)
   877  				if err != nil {
   878  					fmt.Fprintf(os.Stderr, "Child: read error: %v on pipe %d\n", err, i)
   879  					os.Exit(1)
   880  				}
   881  				c <- string(buf[:n])
   882  				close(c)
   883  			}(ch)
   884  			select {
   885  			case m := <-ch:
   886  				response = response + m
   887  			case <-time.After(5 * time.Second):
   888  				fmt.Fprintf(os.Stderr, "Child: Timeout reading from pipe: %d\n", i)
   889  				os.Exit(1)
   890  			}
   891  		}
   892  		fmt.Fprintf(os.Stderr, "child: %s", response)
   893  		os.Exit(0)
   894  	case "exec":
   895  		cmd := exec.Command(args[1])
   896  		cmd.Dir = args[0]
   897  		output, err := cmd.CombinedOutput()
   898  		if err != nil {
   899  			fmt.Fprintf(os.Stderr, "Child: %s %s", err, string(output))
   900  			os.Exit(1)
   901  		}
   902  		fmt.Printf("%s", string(output))
   903  		os.Exit(0)
   904  	case "lookpath":
   905  		p, err := exec.LookPath(args[0])
   906  		if err != nil {
   907  			fmt.Fprintf(os.Stderr, "LookPath failed: %v\n", err)
   908  			os.Exit(1)
   909  		}
   910  		fmt.Print(p)
   911  		os.Exit(0)
   912  	case "stderrfail":
   913  		fmt.Fprintf(os.Stderr, "some stderr text\n")
   914  		os.Exit(1)
   915  	case "sleep":
   916  		time.Sleep(3 * time.Second)
   917  		os.Exit(0)
   918  	case "pipehandle":
   919  		handle, _ := strconv.ParseUint(args[0], 16, 64)
   920  		pipe := os.NewFile(uintptr(handle), "")
   921  		_, err := fmt.Fprint(pipe, args[1])
   922  		if err != nil {
   923  			fmt.Fprintf(os.Stderr, "writing to pipe failed: %v\n", err)
   924  			os.Exit(1)
   925  		}
   926  		pipe.Close()
   927  		os.Exit(0)
   928  	default:
   929  		fmt.Fprintf(os.Stderr, "Unknown command %q\n", cmd)
   930  		os.Exit(2)
   931  	}
   932  }
   933  
   934  type delayedInfiniteReader struct{}
   935  
   936  func (delayedInfiniteReader) Read(b []byte) (int, error) {
   937  	time.Sleep(100 * time.Millisecond)
   938  	for i := range b {
   939  		b[i] = 'x'
   940  	}
   941  	return len(b), nil
   942  }
   943  
   944  // Issue 9173: ignore stdin pipe writes if the program completes successfully.
   945  func TestIgnorePipeErrorOnSuccess(t *testing.T) {
   946  	testenv.MustHaveExec(t)
   947  
   948  	testWith := func(r io.Reader) func(*testing.T) {
   949  		return func(t *testing.T) {
   950  			cmd := helperCommand(t, "echo", "foo")
   951  			var out bytes.Buffer
   952  			cmd.Stdin = r
   953  			cmd.Stdout = &out
   954  			if err := cmd.Run(); err != nil {
   955  				t.Fatal(err)
   956  			}
   957  			if got, want := out.String(), "foo\n"; got != want {
   958  				t.Errorf("output = %q; want %q", got, want)
   959  			}
   960  		}
   961  	}
   962  	t.Run("10MB", testWith(strings.NewReader(strings.Repeat("x", 10<<20))))
   963  	t.Run("Infinite", testWith(delayedInfiniteReader{}))
   964  }
   965  
   966  type badWriter struct{}
   967  
   968  func (w *badWriter) Write(data []byte) (int, error) {
   969  	return 0, io.ErrUnexpectedEOF
   970  }
   971  
   972  func TestClosePipeOnCopyError(t *testing.T) {
   973  	testenv.MustHaveExec(t)
   974  
   975  	if runtime.GOOS == "windows" || runtime.GOOS == "plan9" {
   976  		t.Skipf("skipping test on %s - no yes command", runtime.GOOS)
   977  	}
   978  	cmd := exec.Command("yes")
   979  	cmd.Stdout = new(badWriter)
   980  	c := make(chan int, 1)
   981  	go func() {
   982  		err := cmd.Run()
   983  		if err == nil {
   984  			t.Errorf("yes completed successfully")
   985  		}
   986  		c <- 1
   987  	}()
   988  	select {
   989  	case <-c:
   990  		// ok
   991  	case <-time.After(5 * time.Second):
   992  		t.Fatalf("yes got stuck writing to bad writer")
   993  	}
   994  }
   995  
   996  func TestOutputStderrCapture(t *testing.T) {
   997  	testenv.MustHaveExec(t)
   998  
   999  	cmd := helperCommand(t, "stderrfail")
  1000  	_, err := cmd.Output()
  1001  	ee, ok := err.(*exec.ExitError)
  1002  	if !ok {
  1003  		t.Fatalf("Output error type = %T; want ExitError", err)
  1004  	}
  1005  	got := string(ee.Stderr)
  1006  	want := "some stderr text\n"
  1007  	if got != want {
  1008  		t.Errorf("ExitError.Stderr = %q; want %q", got, want)
  1009  	}
  1010  }
  1011  
  1012  func TestContext(t *testing.T) {
  1013  	ctx, cancel := context.WithCancel(context.Background())
  1014  	c := helperCommandContext(t, ctx, "pipetest")
  1015  	stdin, err := c.StdinPipe()
  1016  	if err != nil {
  1017  		t.Fatal(err)
  1018  	}
  1019  	stdout, err := c.StdoutPipe()
  1020  	if err != nil {
  1021  		t.Fatal(err)
  1022  	}
  1023  	if err := c.Start(); err != nil {
  1024  		t.Fatal(err)
  1025  	}
  1026  
  1027  	if _, err := stdin.Write([]byte("O:hi\n")); err != nil {
  1028  		t.Fatal(err)
  1029  	}
  1030  	buf := make([]byte, 5)
  1031  	n, err := io.ReadFull(stdout, buf)
  1032  	if n != len(buf) || err != nil || string(buf) != "O:hi\n" {
  1033  		t.Fatalf("ReadFull = %d, %v, %q", n, err, buf[:n])
  1034  	}
  1035  	waitErr := make(chan error, 1)
  1036  	go func() {
  1037  		waitErr <- c.Wait()
  1038  	}()
  1039  	cancel()
  1040  	select {
  1041  	case err := <-waitErr:
  1042  		if err == nil {
  1043  			t.Fatal("expected Wait failure")
  1044  		}
  1045  	case <-time.After(3 * time.Second):
  1046  		t.Fatal("timeout waiting for child process death")
  1047  	}
  1048  }
  1049  
  1050  func TestContextCancel(t *testing.T) {
  1051  	ctx, cancel := context.WithCancel(context.Background())
  1052  	defer cancel()
  1053  	c := helperCommandContext(t, ctx, "cat")
  1054  
  1055  	stdin, err := c.StdinPipe()
  1056  	if err != nil {
  1057  		t.Fatal(err)
  1058  	}
  1059  	defer stdin.Close()
  1060  
  1061  	if err := c.Start(); err != nil {
  1062  		t.Fatal(err)
  1063  	}
  1064  
  1065  	// At this point the process is alive. Ensure it by sending data to stdin.
  1066  	if _, err := io.WriteString(stdin, "echo"); err != nil {
  1067  		t.Fatal(err)
  1068  	}
  1069  
  1070  	cancel()
  1071  
  1072  	// Calling cancel should have killed the process, so writes
  1073  	// should now fail.  Give the process a little while to die.
  1074  	start := time.Now()
  1075  	for {
  1076  		if _, err := io.WriteString(stdin, "echo"); err != nil {
  1077  			break
  1078  		}
  1079  		if time.Since(start) > time.Minute {
  1080  			t.Fatal("canceling context did not stop program")
  1081  		}
  1082  		time.Sleep(time.Millisecond)
  1083  	}
  1084  
  1085  	if err := c.Wait(); err == nil {
  1086  		t.Error("program unexpectedly exited successfully")
  1087  	} else {
  1088  		t.Logf("exit status: %v", err)
  1089  	}
  1090  }
  1091  
  1092  // test that environment variables are de-duped.
  1093  func TestDedupEnvEcho(t *testing.T) {
  1094  	testenv.MustHaveExec(t)
  1095  
  1096  	cmd := helperCommand(t, "echoenv", "FOO")
  1097  	cmd.Env = append(cmd.Env, "FOO=bad", "FOO=good")
  1098  	out, err := cmd.CombinedOutput()
  1099  	if err != nil {
  1100  		t.Fatal(err)
  1101  	}
  1102  	if got, want := strings.TrimSpace(string(out)), "good"; got != want {
  1103  		t.Errorf("output = %q; want %q", got, want)
  1104  	}
  1105  }
  1106  
  1107  func TestString(t *testing.T) {
  1108  	echoPath, err := exec.LookPath("echo")
  1109  	if err != nil {
  1110  		t.Skip(err)
  1111  	}
  1112  	tests := [...]struct {
  1113  		path string
  1114  		args []string
  1115  		want string
  1116  	}{
  1117  		{"echo", nil, echoPath},
  1118  		{"echo", []string{"a"}, echoPath + " a"},
  1119  		{"echo", []string{"a", "b"}, echoPath + " a b"},
  1120  	}
  1121  	for _, test := range tests {
  1122  		cmd := exec.Command(test.path, test.args...)
  1123  		if got := cmd.String(); got != test.want {
  1124  			t.Errorf("String(%q, %q) = %q, want %q", test.path, test.args, got, test.want)
  1125  		}
  1126  	}
  1127  }
  1128  
  1129  func TestStringPathNotResolved(t *testing.T) {
  1130  	_, err := exec.LookPath("makemeasandwich")
  1131  	if err == nil {
  1132  		t.Skip("wow, thanks")
  1133  	}
  1134  	cmd := exec.Command("makemeasandwich", "-lettuce")
  1135  	want := "makemeasandwich -lettuce"
  1136  	if got := cmd.String(); got != want {
  1137  		t.Errorf("String(%q, %q) = %q, want %q", "makemeasandwich", "-lettuce", got, want)
  1138  	}
  1139  }
  1140  
  1141  // start a child process without the user code explicitly starting
  1142  // with a copy of the parent's. (The Windows SYSTEMROOT issue: Issue
  1143  // 25210)
  1144  func TestChildCriticalEnv(t *testing.T) {
  1145  	testenv.MustHaveExec(t)
  1146  	if runtime.GOOS != "windows" {
  1147  		t.Skip("only testing on Windows")
  1148  	}
  1149  	cmd := helperCommand(t, "echoenv", "SYSTEMROOT")
  1150  	cmd.Env = []string{"GO_WANT_HELPER_PROCESS=1"}
  1151  	out, err := cmd.CombinedOutput()
  1152  	if err != nil {
  1153  		t.Fatal(err)
  1154  	}
  1155  	if strings.TrimSpace(string(out)) == "" {
  1156  		t.Error("no SYSTEMROOT found")
  1157  	}
  1158  }
  1159  

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