return pid, 0, err
}

// Implemented in runtime package.
func runtime_BeforeExec()
func runtime_AfterExec()

// execveLibc is non-nil on OS using libc syscall, set to execve in exec_libc.go; this
// avoids a build dependency for other platforms.
var execveLibc func(path uintptr, argv uintptr, envp uintptr) Errno
var execveDarwin func(path *byte, argv **byte, envp **byte) error

func write1(fd uintptr, buf uintptr, nbyte uintptr) (n uintptr, err Errno)

// syscall defines this global on our behalf to avoid a build dependency on other platforms
func init() {
	execveLibc = execve
}

// Fork, dup fd onto 0..len(fd), and exec(argv0, argvv, envv) in child.
// If a dup or exec fails, write the errno error to pipe.
// (Pipe is close-on-exec so if exec succeeds, it will be closed.)