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os/exec: add the Cancel and WaitDelay fields

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Fixes #50436.

Change-Id: I9dff8caa317a04b7b2b605f810b8f12ef8ca485d
Reviewed-on: https://go-review.googlesource.com/c/go/+/401835
TryBot-Result: Gopher Robot <gobot@golang.org>
Run-TryBot: Bryan Mills <bcmills@google.com>
Auto-Submit: Bryan Mills <bcmills@google.com>
Reviewed-by: Ian Lance Taylor <iant@google.com>
This commit is contained in:
Bryan C. Mills 2022-04-21 13:58:06 -04:00 committed by Gopher Robot
parent 9fffcde118
commit 55eaae452c
6 changed files with 846 additions and 30 deletions
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3
api/next/50436.txt Normal file
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@ -0,0 +1,3 @@
pkg os/exec, type Cmd struct, Cancel func() error #50436
pkg os/exec, type Cmd struct, WaitDelay time.Duration #50436
pkg os/exec, var ErrWaitDelay error #50436

274
src/os/exec/exec.go
View File

@ -103,6 +103,7 @@ import (
"strconv"
"strings"
"syscall"
"time"
)
// Error is returned by LookPath when it fails to classify a file as an
@ -120,6 +121,11 @@ func (e *Error) Error() string {
func (e *Error) Unwrap() error { return e.Err }
// ErrWaitDelay is returned by (*Cmd).Wait if the process exits with a
// successful status code but its output pipes are not closed before the
// command's WaitDelay expires.
var ErrWaitDelay = errors.New("exec: WaitDelay expired before I/O complete")
// wrappedError wraps an error without relying on fmt.Errorf.
type wrappedError struct {
prefix string
@ -178,7 +184,8 @@ type Cmd struct {
// goroutine reads from Stdin and delivers that data to the command
// over a pipe. In this case, Wait does not complete until the goroutine
// stops copying, either because it has reached the end of Stdin
// (EOF or a read error) or because writing to the pipe returned an error.
// (EOF or a read error), or because writing to the pipe returned an error,
// or because a nonzero WaitDelay was set and expired.
Stdin io.Reader
// Stdout and Stderr specify the process's standard output and error.
@ -192,7 +199,8 @@ type Cmd struct {
// Otherwise, during the execution of the command a separate goroutine
// reads from the process over a pipe and delivers that data to the
// corresponding Writer. In this case, Wait does not complete until the
// goroutine reaches EOF or encounters an error.
// goroutine reaches EOF or encounters an error or a nonzero WaitDelay
// expires.
//
// If Stdout and Stderr are the same writer, and have a type that can
// be compared with ==, at most one goroutine at a time will call Write.
@ -218,8 +226,64 @@ type Cmd struct {
// populate its ProcessState when the command completes.
ProcessState *os.ProcessState
ctx context.Context // nil means none
Err error // LookPath error, if any.
// ctx is the context passed to CommandContext, if any.
ctx context.Context
Err error // LookPath error, if any.
// If Cancel is non-nil, the command must have been created with
// CommandContext and Cancel will be called when the command's
// Context is done. By default, CommandContext sets Cancel to
// call the Kill method on the command's Process.
//
// Typically a custom Cancel will send a signal to the command's
// Process, but it may instead take other actions to initiate cancellation,
// such as closing a stdin or stdout pipe or sending a shutdown request on a
// network socket.
//
// If the command exits with a success status after Cancel is
// called, and Cancel does not return an error equivalent to
// os.ErrProcessDone, then Wait and similar methods will return a non-nil
// error: either an error wrapping the one returned by Cancel,
// or the error from the Context.
// (If the command exits with a non-success status, or Cancel
// returns an error that wraps os.ErrProcessDone, Wait and similar methods
// continue to return the command's usual exit status.)
//
// If Cancel is set to nil, nothing will happen immediately when the command's
// Context is done, but a nonzero WaitDelay will still take effect. That may
// be useful, for example, to work around deadlocks in commands that do not
// support shutdown signals but are expected to always finish quickly.
//
// Cancel will not be called if Start returns a non-nil error.
Cancel func() error
// If WaitDelay is non-zero, it bounds the time spent waiting on two sources
// of unexpected delay in Wait: a child process that fails to exit after the
// associated Context is canceled, and a child process that exits but leaves
// its I/O pipes unclosed.
//
// The WaitDelay timer starts when either the associated Context is done or a
// call to Wait observes that the child process has exited, whichever occurs
// first. When the delay has elapsed, the command shuts down the child process
// and/or its I/O pipes.
//
// If the child process has failed to exit — perhaps because it ignored or
// failed to receive a shutdown signal from a Cancel function, or because no
// Cancel function was set — then it will be terminated using os.Process.Kill.
//
// Then, if the I/O pipes communicating with the child process are still open,
// those pipes are closed in order to unblock any goroutines currently blocked
// on Read or Write calls.
//
// If pipes are closed due to WaitDelay, no Cancel call has occurred,
// and the command has otherwise exited with a successful status, Wait and
// similar methods will return ErrWaitDelay instead of nil.
//
// If WaitDelay is zero (the default), I/O pipes will be read until EOF,
// which might not occur until orphaned subprocesses of the command have
// also closed their descriptors for the pipes.
WaitDelay time.Duration
// childIOFiles holds closers for any of the child process's
// stdin, stdout, and/or stderr files that were opened by the Cmd itself
@ -230,7 +294,8 @@ type Cmd struct {
// parentIOPipes holds closers for the parent's end of any pipes
// connected to the child's stdin, stdout, and/or stderr streams
// that were opened by the Cmd itself (not supplied by the caller).
// These should be closed after Wait sees the command exit.
// These should be closed after Wait sees the command and copying
// goroutines exit, or after WaitDelay has expired.
parentIOPipes []io.Closer
// goroutine holds a set of closures to execute to copy data
@ -242,7 +307,8 @@ type Cmd struct {
// goroutineErr is set to nil once its error has been received.
goroutineErr <-chan error
ctxErr <-chan error // if non nil, receives the error from watchCtx exactly once
// If ctxResult is non-nil, it receives the result of watchCtx exactly once.
ctxResult <-chan ctxResult
// The stack saved when the Command was created, if GODEBUG contains
// execwait=2. Used for debugging leaks.
@ -268,6 +334,20 @@ type Cmd struct {
lookPathErr error
}
// A ctxResult reports the result of watching the Context associated with a
// running command (and sending corresponding signals if needed).
type ctxResult struct {
err error
// If timer is non-nil, it expires after WaitDelay has elapsed after
// the Context is done.
//
// (If timer is nil, that means that the Context was not done before the
// command completed, or no WaitDelay was set, or the WaitDelay already
// expired and its effect was already applied.)
timer *time.Timer
}
// Command returns the Cmd struct to execute the named program with
// the given arguments.
//
@ -349,15 +429,22 @@ func Command(name string, arg ...string) *Cmd {
// CommandContext is like Command but includes a context.
//
// The provided context is used to kill the process (by calling
// os.Process.Kill) if the context becomes done before the command
// completes on its own.
// The provided context is used to interrupt the process
// (by calling cmd.Cancel or os.Process.Kill)
// if the context becomes done before the command completes on its own.
//
// CommandContext sets the command's Cancel function to invoke the Kill method
// on its Process, and leaves its WaitDelay unset. The caller may change the
// cancellation behavior by modifying those fields before starting the command.
func CommandContext(ctx context.Context, name string, arg ...string) *Cmd {
if ctx == nil {
panic("nil Context")
}
cmd := Command(name, arg...)
cmd.ctx = ctx
cmd.Cancel = func() error {
return cmd.Process.Kill()
}
return cmd
}
@ -566,6 +653,9 @@ func (c *Cmd) Start() error {
}
c.Path = lp
}
if c.Cancel != nil && c.ctx == nil {
return errors.New("exec: command with a non-nil Cancel was not created with CommandContext")
}
if c.ctx != nil {
select {
case <-c.ctx.Done():
@ -638,38 +728,114 @@ func (c *Cmd) Start() error {
c.goroutine = nil // Allow the goroutines' closures to be GC'd when they complete.
}
if c.ctx != nil && c.ctx.Done() != nil {
errc := make(chan error)
c.ctxErr = errc
go c.watchCtx(errc)
// If we have anything to do when the command's Context expires,
// start a goroutine to watch for cancellation.
//
// (Even if the command was created by CommandContext, a helper library may
// have explicitly set its Cancel field back to nil, indicating that it should
// be allowed to continue running after cancellation after all.)
if (c.Cancel != nil || c.WaitDelay != 0) && c.ctx != nil && c.ctx.Done() != nil {
resultc := make(chan ctxResult)
c.ctxResult = resultc
go c.watchCtx(resultc)
}
return nil
}
// watchCtx watches c.ctx until it is able to send a result to errc.
// watchCtx watches c.ctx until it is able to send a result to resultc.
//
// If c.ctx is done before a result can be sent, watchCtx terminates c.Process.
func (c *Cmd) watchCtx(errc chan<- error) {
// If c.ctx is done before a result can be sent, watchCtx calls c.Cancel,
// and/or kills cmd.Process it after c.WaitDelay has elapsed.
//
// watchCtx manipulates c.goroutineErr, so its result must be received before
// c.awaitGoroutines is called.
func (c *Cmd) watchCtx(resultc chan<- ctxResult) {
select {
case errc <- nil:
case resultc <- ctxResult{}:
return
case <-c.ctx.Done():
}
var err error
if c.Cancel != nil {
if interruptErr := c.Cancel(); interruptErr == nil {
// We appear to have successfully interrupted the command, so any
// program behavior from this point may be due to ctx even if the
// command exits with code 0.
err = c.ctx.Err()
} else if errors.Is(interruptErr, os.ErrProcessDone) {
// The process already finished: we just didn't notice it yet.
// (Perhaps c.Wait hadn't been called, or perhaps it happened to race with
// c.ctx being cancelled.) Don't inject a needless error.
} else {
err = wrappedError{
prefix: "exec: canceling Cmd",
err: interruptErr,
}
}
}
if c.WaitDelay == 0 {
resultc <- ctxResult{err: err}
return
}
timer := time.NewTimer(c.WaitDelay)
select {
case resultc <- ctxResult{err: err, timer: timer}:
// c.Process.Wait returned and we've handed the timer off to c.Wait.
// It will take care of goroutine shutdown from here.
return
case <-timer.C:
}
killed := false
if killErr := c.Process.Kill(); killErr == nil {
// We appear to have killed the process. c.Process.Wait should return a
// non-nil error to c.Wait unless the Kill signal races with a successful
// exit, and if that does happen we shouldn't report a spurious error,
// so don't set err to anything here.
killed = true
} else if !errors.Is(killErr, os.ErrProcessDone) {
err = wrappedError{
prefix: "exec: error sending signal to Cmd",
prefix: "exec: killing Cmd",
err: killErr,
}
}
errc <- err
if c.goroutineErr != nil {
select {
case goroutineErr := <-c.goroutineErr:
// Forward goroutineErr only if we don't have reason to believe it was
// caused by a call to Cancel or Kill above.
if err == nil && !killed {
err = goroutineErr
}
default:
// Close the child process's I/O pipes, in case it abandoned some
// subprocess that inherited them and is still holding them open
// (see https://go.dev/issue/23019).
//
// We close the goroutine pipes only after we have sent any signals we're
// going to send to the process (via Signal or Kill above): if we send
// SIGKILL to the process, we would prefer for it to die of SIGKILL, not
// SIGPIPE. (However, this may still cause any orphaned subprocesses to
// terminate with SIGPIPE.)
closeDescriptors(c.parentIOPipes)
// Wait for the copying goroutines to finish, but report ErrWaitDelay for
// the error: any other error here could result from closing the pipes.
_ = <-c.goroutineErr
if err == nil {
err = ErrWaitDelay
}
}
// Since we have already received the only result from c.goroutineErr,
// set it to nil to prevent awaitGoroutines from blocking on it.
c.goroutineErr = nil
}
resultc <- ctxResult{err: err}
}
// An ExitError reports an unsuccessful exit by a command.
@ -724,24 +890,23 @@ func (c *Cmd) Wait() error {
}
c.ProcessState = state
if c.ctxErr != nil {
interruptErr := <-c.ctxErr
var timer *time.Timer
if c.ctxResult != nil {
watch := <-c.ctxResult
timer = watch.timer
// If c.Process.Wait returned an error, prefer that.
// Otherwise, report any error from the interrupt goroutine.
if err == nil {
err = interruptErr
// Otherwise, report any error from the watchCtx goroutine,
// such as a Context cancellation or a WaitDelay overrun.
if err == nil && watch.err != nil {
err = watch.err
}
}
// Wait for the pipe-copying goroutines to complete.
if c.goroutineErr != nil {
if goroutineErr := c.awaitGoroutines(timer); err == nil {
// Report an error from the copying goroutines only if the program otherwise
// exited normally on its own. Otherwise, the copying error may be due to the
// abnormal termination.
copyErr := <-c.goroutineErr
if err == nil {
err = copyErr
}
err = goroutineErr
}
closeDescriptors(c.parentIOPipes)
c.parentIOPipes = nil
@ -749,6 +914,55 @@ func (c *Cmd) Wait() error {
return err
}
// awaitGoroutines waits for the results of the goroutines copying data to or
// from the command's I/O pipes.
//
// If c.WaitDelay elapses before the goroutines complete, awaitGoroutines
// forcibly closes their pipes and returns ErrWaitDelay.
//
// If timer is non-nil, it must send to timer.C at the end of c.WaitDelay.
func (c *Cmd) awaitGoroutines(timer *time.Timer) error {
defer func() {
if timer != nil {
timer.Stop()
}
c.goroutineErr = nil
}()
if c.goroutineErr == nil {
return nil // No running goroutines to await.
}
if timer == nil {
if c.WaitDelay == 0 {
return <-c.goroutineErr
}
select {
case err := <-c.goroutineErr:
// Avoid the overhead of starting a timer.
return err
default:
}
// No existing timer was started: either there is no Context associated with
// the command, or c.Process.Wait completed before the Context was done.
timer = time.NewTimer(c.WaitDelay)
}
select {
case <-timer.C:
closeDescriptors(c.parentIOPipes)
// Wait for the copying goroutines to finish, but ignore any error
// (since it was probably caused by closing the pipes).
_ = <-c.goroutineErr
return ErrWaitDelay
case err := <-c.goroutineErr:
return err
}
}
// Output runs the command and returns its standard output.
// Any returned error will usually be of type *ExitError.
// If c.Stderr was nil, Output populates ExitError.Stderr.

14
src/os/exec/exec_other_test.go Normal file
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@ -0,0 +1,14 @@
// Copyright 2021 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.
//go:build !unix && !windows
package exec_test
import "os"
var (
quitSignal os.Signal = nil
pipeSignal os.Signal = nil
)

563
src/os/exec/exec_test.go
View File

@ -24,6 +24,7 @@ import (
"os"
"os/exec"
"os/exec/internal/fdtest"
"os/signal"
"path/filepath"
"reflect"
"runtime"
@ -31,6 +32,7 @@ import (
"strconv"
"strings"
"sync"
"sync/atomic"
"testing"
"time"
)
@ -191,6 +193,7 @@ var helperCommands = map[string]func(...string){
"describefiles": cmdDescribeFiles,
"stderrfail": cmdStderrFail,
"yes": cmdYes,
"hang": cmdHang,
}
func cmdEcho(args ...string) {
@ -1122,3 +1125,563 @@ func TestDoubleStartLeavesPipesOpen(t *testing.T) {
t.Fatalf("read %q from stdout pipe; want %q", b, msg)
}
}
func cmdHang(args ...string) {
sleep, err := time.ParseDuration(args[0])
if err != nil {
panic(err)
}
fs := flag.NewFlagSet("hang", flag.ExitOnError)
exitOnInterrupt := fs.Bool("interrupt", false, "if true, commands should exit 0 on os.Interrupt")
subsleep := fs.Duration("subsleep", 0, "amount of time for the 'hang' helper to leave an orphaned subprocess sleeping with stderr open")
probe := fs.Duration("probe", 0, "if nonzero, the 'hang' helper should write to stderr at this interval, and exit nonzero if a write fails")
read := fs.Bool("read", false, "if true, the 'hang' helper should read stdin to completion before sleeping")
fs.Parse(args[1:])
pid := os.Getpid()
if *subsleep != 0 {
cmd := exec.Command(exePath(nil), "hang", subsleep.String(), "-read=true", "-probe="+probe.String())
cmd.Stdin = os.Stdin
cmd.Stderr = os.Stderr
out, err := cmd.StdoutPipe()
if err != nil {
fmt.Fprintln(os.Stderr, err)
os.Exit(1)
}
cmd.Start()
buf := new(strings.Builder)
if _, err := io.Copy(buf, out); err != nil {
fmt.Fprintln(os.Stderr, err)
cmd.Process.Kill()
cmd.Wait()
os.Exit(1)
}
fmt.Fprintf(os.Stderr, "%d: started %d: %v\n", pid, cmd.Process.Pid, cmd)
}
if *exitOnInterrupt {
c := make(chan os.Signal, 1)
signal.Notify(c, os.Interrupt)
go func() {
sig := <-c
fmt.Fprintf(os.Stderr, "%d: received %v\n", pid, sig)
os.Exit(0)
}()
} else {
signal.Ignore(os.Interrupt)
}
// Signal that the process is set up by closing stdout.
os.Stdout.Close()
if *read {
if pipeSignal != nil {
signal.Ignore(pipeSignal)
}
r := bufio.NewReader(os.Stdin)
for {
line, err := r.ReadBytes('\n')
if len(line) > 0 {
// Ignore write errors: we want to keep reading even if stderr is closed.
fmt.Fprintf(os.Stderr, "%d: read %s", pid, line)
}
if err != nil {
fmt.Fprintf(os.Stderr, "%d: finished read: %v", pid, err)
break
}
}
}
if *probe != 0 {
ticker := time.NewTicker(*probe)
go func() {
for range ticker.C {
if _, err := fmt.Fprintf(os.Stderr, "%d: ok\n", pid); err != nil {
os.Exit(1)
}
}
}()
}
if sleep != 0 {
time.Sleep(sleep)
fmt.Fprintf(os.Stderr, "%d: slept %v\n", pid, sleep)
}
}
// A tickReader reads an unbounded sequence of timestamps at no more than a
// fixed interval.
type tickReader struct {
interval time.Duration
lastTick time.Time
s string
}
func newTickReader(interval time.Duration) *tickReader {
return &tickReader{interval: interval}
}
func (r *tickReader) Read(p []byte) (n int, err error) {
if len(r.s) == 0 {
if d := r.interval - time.Since(r.lastTick); d > 0 {
time.Sleep(d)
}
r.lastTick = time.Now()
r.s = r.lastTick.Format(time.RFC3339Nano + "\n")
}
n = copy(p, r.s)
r.s = r.s[n:]
return n, nil
}
func startHang(t *testing.T, ctx context.Context, hangTime time.Duration, interrupt os.Signal, waitDelay time.Duration, flags ...string) *exec.Cmd {
t.Helper()
args := append([]string{hangTime.String()}, flags...)
cmd := helperCommandContext(t, ctx, "hang", args...)
cmd.Stdin = newTickReader(1 * time.Millisecond)
cmd.Stderr = new(strings.Builder)
if interrupt == nil {
cmd.Cancel = nil
} else {
cmd.Cancel = func() error {
return cmd.Process.Signal(interrupt)
}
}
cmd.WaitDelay = waitDelay
out, err := cmd.StdoutPipe()
if err != nil {
t.Fatal(err)
}
t.Log(cmd)
if err := cmd.Start(); err != nil {
t.Fatal(err)
}
// Wait for cmd to close stdout to signal that its handlers are installed.
buf := new(strings.Builder)
if _, err := io.Copy(buf, out); err != nil {
t.Error(err)
cmd.Process.Kill()
cmd.Wait()
t.FailNow()
}
if buf.Len() > 0 {
t.Logf("stdout %v:\n%s", cmd.Args, buf)
}
return cmd
}
func TestWaitInterrupt(t *testing.T) {
t.Parallel()
// tooLong is an arbitrary duration that is expected to be much longer than
// the test runs, but short enough that leaked processes will eventually exit
// on their own.
const tooLong = 10 * time.Minute
// Control case: with no cancellation and no WaitDelay, we should wait for the
// process to exit.
t.Run("Wait", func(t *testing.T) {
t.Parallel()
cmd := startHang(t, context.Background(), 1*time.Millisecond, os.Kill, 0)
err := cmd.Wait()
t.Logf("stderr:\n%s", cmd.Stderr)
t.Logf("[%d] %v", cmd.Process.Pid, err)
if err != nil {
t.Errorf("Wait: %v; want <nil>", err)
}
if ps := cmd.ProcessState; !ps.Exited() {
t.Errorf("cmd did not exit: %v", ps)
} else if code := ps.ExitCode(); code != 0 {
t.Errorf("cmd.ProcessState.ExitCode() = %v; want 0", code)
}
})
// With a very long WaitDelay and no Cancel function, we should wait for the
// process to exit even if the command's Context is cancelled.
t.Run("WaitDelay", func(t *testing.T) {
if runtime.GOOS == "windows" {
t.Skipf("skipping: os.Interrupt is not implemented on Windows")
}
t.Parallel()
ctx, cancel := context.WithCancel(context.Background())
cmd := startHang(t, ctx, tooLong, nil, tooLong, "-interrupt=true")
cancel()
time.Sleep(1 * time.Millisecond)
// At this point cmd should still be running (because we passed nil to
// startHang for the cancel signal). Sending it an explicit Interrupt signal
// should succeed.
if err := cmd.Process.Signal(os.Interrupt); err != nil {
t.Error(err)
}
err := cmd.Wait()
t.Logf("stderr:\n%s", cmd.Stderr)
t.Logf("[%d] %v", cmd.Process.Pid, err)
// This program exits with status 0,
// but pretty much always does so during the wait delay.
// Since the Cmd itself didn't do anything to stop the process when the
// context expired, a successful exit is valid (even if late) and does
// not merit a non-nil error.
if err != nil {
t.Errorf("Wait: %v; want %v", err, ctx.Err())
}
if ps := cmd.ProcessState; !ps.Exited() {
t.Errorf("cmd did not exit: %v", ps)
} else if code := ps.ExitCode(); code != 0 {
t.Errorf("cmd.ProcessState.ExitCode() = %v; want 0", code)
}
})
// If the context is cancelled and the Cancel function sends os.Kill,
// the process should be terminated immediately, and its output
// pipes should be closed (causing Wait to return) after WaitDelay
// even if a child process is still writing to them.
t.Run("SIGKILL-hang", func(t *testing.T) {
t.Parallel()
ctx, cancel := context.WithCancel(context.Background())
cmd := startHang(t, ctx, tooLong, os.Kill, 10*time.Millisecond, "-subsleep=10m", "-probe=1ms")
cancel()
err := cmd.Wait()
t.Logf("stderr:\n%s", cmd.Stderr)
t.Logf("[%d] %v", cmd.Process.Pid, err)
// This test should kill the child process after 10ms,
// leaving a grandchild process writing probes in a loop.
// The child process should be reported as failed,
// and the grandchild will exit (or die by SIGPIPE) once the
// stderr pipe is closed.
if ee := new(*exec.ExitError); !errors.As(err, ee) {
t.Errorf("Wait error = %v; want %T", err, *ee)
}
})
// If the process exits with status 0 but leaves a child behind writing
// to its output pipes, Wait should only wait for WaitDelay before
// closing the pipes and returning. Wait should return ErrWaitDelay
// to indicate that the piped output may be incomplete even though the
// command returned a “success” code.
t.Run("Exit-hang", func(t *testing.T) {
t.Parallel()
cmd := startHang(t, context.Background(), 1*time.Millisecond, nil, 10*time.Millisecond, "-subsleep=10m", "-probe=1ms")
err := cmd.Wait()
t.Logf("stderr:\n%s", cmd.Stderr)
t.Logf("[%d] %v", cmd.Process.Pid, err)
// This child process should exit immediately,
// leaving a grandchild process writing probes in a loop.
// Since the child has no ExitError to report but we did not
// read all of its output, Wait should return ErrWaitDelay.
if !errors.Is(err, exec.ErrWaitDelay) {
t.Errorf("Wait error = %v; want %T", err, exec.ErrWaitDelay)
}
})
// If the Cancel function sends a signal that the process can handle, and it
// handles that signal without actually exiting, then it should be terminated
// after the WaitDelay.
t.Run("SIGINT-ignored", func(t *testing.T) {
if runtime.GOOS == "windows" {
t.Skipf("skipping: os.Interrupt is not implemented on Windows")
}
t.Parallel()
ctx, cancel := context.WithCancel(context.Background())
cmd := startHang(t, ctx, tooLong, os.Interrupt, 10*time.Millisecond, "-interrupt=false")
cancel()
err := cmd.Wait()
t.Logf("stderr:\n%s", cmd.Stderr)
t.Logf("[%d] %v", cmd.Process.Pid, err)
// This command ignores SIGINT, sleeping until it is killed.
// Wait should return the usual error for a killed process.
if ee := new(*exec.ExitError); !errors.As(err, ee) {
t.Errorf("Wait error = %v; want %T", err, *ee)
}
})
// If the process handles the cancellation signal and exits with status 0,
// Wait should report a non-nil error (because the process had to be
// interrupted), and it should be a context error (because there is no error
// to report from the child process itself).
t.Run("SIGINT-handled", func(t *testing.T) {
if runtime.GOOS == "windows" {
t.Skipf("skipping: os.Interrupt is not implemented on Windows")
}
t.Parallel()
ctx, cancel := context.WithCancel(context.Background())
cmd := startHang(t, ctx, tooLong, os.Interrupt, 0, "-interrupt=true")
cancel()
err := cmd.Wait()
t.Logf("stderr:\n%s", cmd.Stderr)
t.Logf("[%d] %v", cmd.Process.Pid, err)
if !errors.Is(err, ctx.Err()) {
t.Errorf("Wait error = %v; want %v", err, ctx.Err())
}
if ps := cmd.ProcessState; !ps.Exited() {
t.Errorf("cmd did not exit: %v", ps)
} else if code := ps.ExitCode(); code != 0 {
t.Errorf("cmd.ProcessState.ExitCode() = %v; want 0", code)
}
})
// If the Cancel function sends SIGQUIT, it should be handled in the usual
// way: a Go program should dump its goroutines and exit with non-success
// status. (We expect SIGQUIT to be a common pattern in real-world use.)
t.Run("SIGQUIT", func(t *testing.T) {
if quitSignal == nil {
t.Skipf("skipping: SIGQUIT is not supported on %v", runtime.GOOS)
}
t.Parallel()
ctx, cancel := context.WithCancel(context.Background())
cmd := startHang(t, ctx, tooLong, quitSignal, 0)
cancel()
err := cmd.Wait()
t.Logf("stderr:\n%s", cmd.Stderr)
t.Logf("[%d] %v", cmd.Process.Pid, err)
if ee := new(*exec.ExitError); !errors.As(err, ee) {
t.Errorf("Wait error = %v; want %v", err, ctx.Err())
}
if ps := cmd.ProcessState; !ps.Exited() {
t.Errorf("cmd did not exit: %v", ps)
} else if code := ps.ExitCode(); code != 2 {
// The default os/signal handler exits with code 2.
t.Errorf("cmd.ProcessState.ExitCode() = %v; want 2", code)
}
if !strings.Contains(fmt.Sprint(cmd.Stderr), "\n\ngoroutine ") {
t.Errorf("cmd.Stderr does not contain a goroutine dump")
}
})
}
func TestCancelErrors(t *testing.T) {
t.Parallel()
// If Cancel returns a non-ErrProcessDone error and the process
// exits successfully, Wait should wrap the error from Cancel.
t.Run("success after error", func(t *testing.T) {
t.Parallel()
ctx, cancel := context.WithCancel(context.Background())
defer cancel()
cmd := helperCommandContext(t, ctx, "pipetest")
stdin, err := cmd.StdinPipe()
if err != nil {
t.Fatal(err)
}
errArbitrary := errors.New("arbitrary error")
cmd.Cancel = func() error {
stdin.Close()
t.Logf("Cancel returning %v", errArbitrary)
return errArbitrary
}
if err := cmd.Start(); err != nil {
t.Fatal(err)
}
cancel()
err = cmd.Wait()
t.Logf("[%d] %v", cmd.Process.Pid, err)
if !errors.Is(err, errArbitrary) || err == errArbitrary {
t.Errorf("Wait error = %v; want an error wrapping %v", err, errArbitrary)
}
})
// If Cancel returns an error equivalent to ErrProcessDone,
// Wait should ignore that error. (ErrProcessDone indicates that the
// process was already done before we tried to interrupt it — maybe we
// just didn't notice because Wait hadn't been called yet.)
t.Run("success after ErrProcessDone", func(t *testing.T) {
t.Parallel()
ctx, cancel := context.WithCancel(context.Background())
defer cancel()
cmd := helperCommandContext(t, ctx, "pipetest")
stdin, err := cmd.StdinPipe()
if err != nil {
t.Fatal(err)
}
stdout, err := cmd.StdoutPipe()
if err != nil {
t.Fatal(err)
}
// We intentionally race Cancel against the process exiting,
// but ensure that the process wins the race (and return ErrProcessDone
// from Cancel to report that).
interruptCalled := make(chan struct{})
done := make(chan struct{})
cmd.Cancel = func() error {
close(interruptCalled)
<-done
t.Logf("Cancel returning an error wrapping ErrProcessDone")
return fmt.Errorf("%w: stdout closed", os.ErrProcessDone)
}
if err := cmd.Start(); err != nil {
t.Fatal(err)
}
cancel()
<-interruptCalled
stdin.Close()
io.Copy(io.Discard, stdout) // reaches EOF when the process exits
close(done)
err = cmd.Wait()
t.Logf("[%d] %v", cmd.Process.Pid, err)
if err != nil {
t.Errorf("Wait error = %v; want nil", err)
}
})
// If Cancel returns an error and the process is killed after
// WaitDelay, Wait should report the usual SIGKILL ExitError, not the
// error from Cancel.
t.Run("killed after error", func(t *testing.T) {
t.Parallel()
ctx, cancel := context.WithCancel(context.Background())
defer cancel()
cmd := helperCommandContext(t, ctx, "pipetest")
stdin, err := cmd.StdinPipe()
if err != nil {
t.Fatal(err)
}
defer stdin.Close()
errArbitrary := errors.New("arbitrary error")
var interruptCalled atomic.Bool
cmd.Cancel = func() error {
t.Logf("Cancel called")
interruptCalled.Store(true)
return errArbitrary
}
cmd.WaitDelay = 1 * time.Millisecond
if err := cmd.Start(); err != nil {
t.Fatal(err)
}
cancel()
err = cmd.Wait()
t.Logf("[%d] %v", cmd.Process.Pid, err)
// Ensure that Cancel actually had the opportunity to
// return the error.
if !interruptCalled.Load() {
t.Errorf("Cancel was not called when the context was canceled")
}
// This test should kill the child process after 1ms,
// To maximize compatibility with existing uses of exec.CommandContext, the
// resulting error should be an exec.ExitError without additional wrapping.
if ee, ok := err.(*exec.ExitError); !ok {
t.Errorf("Wait error = %v; want %T", err, *ee)
}
})
// If Cancel returns ErrProcessDone but the process is not actually done
// (and has to be killed), Wait should report the usual SIGKILL ExitError,
// not the error from Cancel.
t.Run("killed after spurious ErrProcessDone", func(t *testing.T) {
t.Parallel()
ctx, cancel := context.WithCancel(context.Background())
defer cancel()
cmd := helperCommandContext(t, ctx, "pipetest")
stdin, err := cmd.StdinPipe()
if err != nil {
t.Fatal(err)
}
defer stdin.Close()
var interruptCalled atomic.Bool
cmd.Cancel = func() error {
t.Logf("Cancel returning an error wrapping ErrProcessDone")
interruptCalled.Store(true)
return fmt.Errorf("%w: stdout closed", os.ErrProcessDone)
}
cmd.WaitDelay = 1 * time.Millisecond
if err := cmd.Start(); err != nil {
t.Fatal(err)
}
cancel()
err = cmd.Wait()
t.Logf("[%d] %v", cmd.Process.Pid, err)
// Ensure that Cancel actually had the opportunity to
// return the error.
if !interruptCalled.Load() {
t.Errorf("Cancel was not called when the context was canceled")
}
// This test should kill the child process after 1ms,
// To maximize compatibility with existing uses of exec.CommandContext, the
// resulting error should be an exec.ExitError without additional wrapping.
if ee, ok := err.(*exec.ExitError); !ok {
t.Errorf("Wait error of type %T; want %T", err, ee)
}
})
// If Cancel returns an error and the process exits with an
// unsuccessful exit code, the process error should take precedence over the
// Cancel error.
t.Run("nonzero exit after error", func(t *testing.T) {
t.Parallel()
ctx, cancel := context.WithCancel(context.Background())
defer cancel()
cmd := helperCommandContext(t, ctx, "stderrfail")
stderr, err := cmd.StderrPipe()
if err != nil {
t.Fatal(err)
}
errArbitrary := errors.New("arbitrary error")
interrupted := make(chan struct{})
cmd.Cancel = func() error {
close(interrupted)
return errArbitrary
}
if err := cmd.Start(); err != nil {
t.Fatal(err)
}
cancel()
<-interrupted
io.Copy(io.Discard, stderr)
err = cmd.Wait()
t.Logf("[%d] %v", cmd.Process.Pid, err)
if ee, ok := err.(*exec.ExitError); !ok || ee.ProcessState.ExitCode() != 1 {
t.Errorf("Wait error = %v; want exit status 1", err)
}
})
}

17
src/os/exec/exec_unix_test.go Normal file
View File

@ -0,0 +1,17 @@
// Copyright 2022 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.
//go:build unix
package exec_test
import (
"os"
"syscall"
)
var (
quitSignal os.Signal = syscall.SIGQUIT
pipeSignal os.Signal = syscall.SIGPIPE
)

5
src/os/exec/exec_windows_test.go
View File

@ -17,6 +17,11 @@ import (
"testing"
)
var (
quitSignal os.Signal = nil
pipeSignal os.Signal = syscall.SIGPIPE
)
func init() {
registerHelperCommand("pipehandle", cmdPipeHandle)
}