waitid implementation for Go linux/amd64

waitid.go

package linux

import (
	"fmt"
	"syscall"
	"unsafe"
)

// Values for waitid() idtype parameter
//
//nolint: golint
const (
	P_ALL  = 0
	P_PID  = 1
	P_PGID = 2
)

// SiginfoWaitid provides version of siginfo_t struct for waitid() syscall
type SiginfoWaitid struct {
	Signo  int32
	Errno  int32
	Code   int32
	_      int32 // padding
	Pid    uint32
	UID    uint32
	Status int32
	_      [100]byte // struct should be 128 bytes
}

// Waitid implements Linux-specific syscall waitid()
func Waitid(idtype int, id int, infop *SiginfoWaitid, options int) error {
	_, _, e := syscall.Syscall6(syscall.SYS_WAITID, uintptr(idtype), uintptr(id), uintptr(unsafe.Pointer(infop)), uintptr(options), 0, 0)

	if e == 0 {
		return nil
	}

	return e
}

func init() {
	if unsafe.Sizeof(SiginfoWaitid{}) != 128 {
		panic(fmt.Sprintf("SiginfoWaitid structure should be 128 bytes, but it is %d bytes", unsafe.Sizeof(SiginfoWaitid{})))
	}
}

waitid_test.go

package linux_test

import (
	"os/exec"
	"syscall"
	"testing"

	"github.com/stretchr/testify/suite"

	"./linux"
)

type WaitidSuite struct {
	suite.Suite
}

func (suite *WaitidSuite) TestWaitidNoProcesses() {
	var info linux.SiginfoWaitid

	err := linux.Waitid(linux.P_ALL, 0, &info, syscall.WEXITED|syscall.WNOHANG)
	suite.Assert().Equal(err, syscall.ECHILD)
}

func (suite *WaitidSuite) TestWaitidSingleProcess() {
	var info linux.SiginfoWaitid

	cmd := exec.Command("/bin/sh", "-c", ":")
	suite.Assert().NoError(cmd.Start())

	err := linux.Waitid(linux.P_ALL, 0, &info, syscall.WEXITED|syscall.WNOWAIT)

	suite.Assert().Nil(err)
	// zombie status retrieved, but zombie is not reaped
	suite.Assert().EqualValues(info.Pid, cmd.Process.Pid)

	// cmd.Wait should still get zombie status
	suite.Assert().Nil(cmd.Wait())
}

func TestWaitidSuite(t *testing.T) {
	suite.Run(t, new(WaitidSuite))
}