fix issue with sometimes wrong return code of ProcessLogger


As a result of wrong return code Beremiz gives folowing traceback:
Traceback (most recent call last):
File "./Beremiz.py", line 850, in OnMenu
getattr(self.CTR, method)()
File "/home/developer/WorkData/PLC/beremiz/beremiz/ProjectController.py", line 925, in _Build
IECGenRes = self._Generate_SoftPLC()
File "/home/developer/WorkData/PLC/beremiz/beremiz/ProjectController.py", line 568, in _Generate_SoftPLC
return self._Compile_ST_to_SoftPLC()
File "/home/developer/WorkData/PLC/beremiz/beremiz/ProjectController.py", line 661, in _Compile_ST_to_SoftPLC
C_files.remove("POUS.c")
ValueError: list.remove(x): x not in list

The problem is that both threads (for reading stdout and stderr) call self.Proc.poll(),
that updates internal returncode field. This call is done without any locking and the first thread gets correct result,
but other gets 0 as retval. If 0 gets thread, that afterwards calls callback finish, then wrong return code is returned
to the parent. Now only the thread with a callback polls for the return code, other thread just checked local value.

Additionally function spin() waits now until all threads finish reading their pipes, so the results are always correct.

     1

#!/usr/bin/env python

     2

# -*- coding: utf-8 -*-

     3

     4

#This file is part of PLCOpenEditor, a library implementing an IEC 61131-3 editor

     5

#based on the plcopen standard. 

     6

#

     7

#Copyright (C) 2007: Edouard TISSERANT and Laurent BESSARD

     8

#

     9

#See COPYING file for copyrights details.

    10

#

    11

#This library is free software; you can redistribute it and/or

    12

#modify it under the terms of the GNU General Public

    13

#License as published by the Free Software Foundation; either

    14

#version 2.1 of the License, or (at your option) any later version.

    15

#

    16

#This library is distributed in the hope that it will be useful,

    17

#but WITHOUT ANY WARRANTY; without even the implied warranty of

    18

#MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU

    19

#General Public License for more details.

    20

#

    21

#You should have received a copy of the GNU General Public

    22

#License along with this library; if not, write to the Free Software

    23

#Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA

    24

    25

# Package initialisation

    26

    27

# plcopen module dynamically creates its classes

    28

    29

from plcopen import PLCOpenParser, LoadProject, SaveProject, LoadPou, \

    30

    LoadPouInstances, VarOrder, QualifierList, rect

    31

    32