[GRASS-dev] Re: [GRASS GIS] #111: r.los fails in WinGRASS with high values for max_dis parameter

[GRASS GIS]

#111: r.los fails in WinGRASS with high values for max_dis parameter
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  Reporter:  gsancho       |       Owner:  grass-dev at lists.osgeo.org
      Type:  defect        |      Status:  new                      
  Priority:  major         |   Milestone:  6.4.0                    
 Component:  Raster        |     Version:  svn-develbranch6         
Resolution:                |    Keywords:  wingrass r.los           
  Platform:  MSWindows XP  |         Cpu:  x86-32                   
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Comment (by hamish):

 another report of it:
 http://lists.osgeo.org/pipermail/grass-windows/2008-November/001587.html

 ----
 Benjamin Ducke wrote on the -dev list:
 {{{
 Michael,

 this is a problem with dirty memory allocation that never got fixed.
 On some systems, like Linux, the memory manager is a bit more "relaxed"
 and lets this pass. On Windows, it's more strict and kills
 the application. The crashes appear a bit random which is typical for
 memory allocation problems. The more allocations involved (read: the
 bigger
 you set max_dist), the more probable it becomes that a sensitive memory
 region gets corrupted and the program bails out.

 If anyone wants to have a go at it: use Valgrind on Linux. It will tell
 you exactly where the bad allocations happen. I actually had a go at this
 years ago and it was quite easy to fix, but lost my notes in the meantime.

 From memory: the problem can be fixed by delaying the release of memory
 allocated at the start of each run through the main loop.

 I have attached a file "delete3.c" from r.cva for which I fixed the same
 problem.
 I believe this file is identical to the version that r.los uses except for
 the
 changes I made. Look for the string "DELAYED". You should find my comments
 and
 additions. Replicate them for r.los and you _should_ be OK (provided there
 were
 no substantial changes to r.los since I wrote my fixed).

 In main.c, the following has to be added towards the top of the file:

   if (G_parser (argc, argv))
        exit(EXIT_FAILURE);

   G_sleep_on_error (0);


   /* initialize delayed point deletion */
   DELAYED_DELETE =  NULL;

 And this toward the end:

   /* release that last tiny bit of memory ... */
   if ( DELAYED_DELETE != NULL ) {
       G_free ( DELAYED_DELETE );
   }

   return (0);
 }

 Unfortunately, I don't have the time to look into this myself at the
 moment.
 Sorry for not being of more help. This is a long-standing, very annoying
 issue
 that needs fixing urgently. It's embarassing to have such a basic tool
 fail in
 this way.

 Cheers,

 Ben
 }}}

-- 
Ticket URL: <https://trac.osgeo.org/grass/ticket/111#comment:8>
GRASS GIS <http://grass.osgeo.org>