[GRASS-dev] [GRASS GIS] #2134: Create a general exit-safe interface to C libraries

[GRASS GIS]

#2134: Create a general exit-safe interface to C libraries
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 Reporter:  wenzeslaus                            |       Owner:  grass-dev@…              
     Type:  enhancement                           |      Status:  new                      
 Priority:  normal                                |   Milestone:  7.0.0                    
Component:  Python ctypes                         |     Version:  svn-trunk                
 Keywords:  G_fatal_error, exit, multiprocessing  |    Platform:  All                      
      Cpu:  Unspecified                           |  
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Comment(by wenzeslaus):

 Thanks Soeren, this is what I hoped for and I'm looking forward how this
 will continue. I just quickly looked at this topic for now. So, just some
 small notes now.

 I needed to do this changes to get it working:
 {{{
 #!diff
 @@ -19,12 +19,13 @@
  from multiprocessing import Process, Lock, Pipe
  import logging
  from ctypes import *
 -from core import *
 +from grass.script.core import *
  import grass.lib.gis as libgis
  import grass.lib.raster as libraster
  import grass.lib.vector as libvector
  import grass.lib.date as libdate
  import grass.lib.raster3d as libraster3d
 +from datetime import datetime
 }}}
 I though I understand how it works with exceptions and doctest but
 apparently not, even I tried verbose mode:
 {{{
 python -m doctest -v c_library_interface.py
 }}}
 Anyway test passes. Would it be possible to write a test also for the case
 of waiting, killing and restarting the server? I mean the case when I run
 something with `call_no_wait(function=aaa)`, it runs for a long time,
 meanwhile I call `call(function=bbb)` but then `bbb` fails and kills the
 server. Does this make sense?

 About the interface. I'm not sure about how to report errors. The
 functions might need to accept keyword arguments in some way. How to deal
 with objects, e.g. how to use pyGRASS through this?

 I was not thinking about how to deal with wrapping all C functions. But
 maybe manual wrapping it is inevitable if we want really Python(ic)
 interface. We already have pyGRASS for this reason.

 The last not is about naming. Although it is a well established practice
 in GRASS that things are named with two or more different names, I would
 suggest to use only one name for newly created things. We are at the
 beginning, we can always rename but it would be safer to use one name at
 time. `*C*Interface` is a nice name (although it it might by also
 `*Python*Interface`) but it is more for the particular implementation
 (interface for temporal framework or to messages) than for the general
 thing (server). `RPCServer` is very general, not sure about that. What
 about `CFunctionCaller`? I also heard suggestion `NoGFatal_Huray!!!` from
 someone here but that's not a valid Python identifier, although, with
 unicode identifiers, there might be a way. No strong opinion here.

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Ticket URL: <http://trac.osgeo.org/grass/ticket/2134#comment:2>
GRASS GIS <http://grass.osgeo.org>