[Octave-bug-tracker] [bug #44406] glps_renderer::draw uses static state variable, potential bug?

[Dan Sebald]

URL:
  <http://savannah.gnu.org/bugs/?44406>

                 Summary: glps_renderer::draw uses static state variable,
potential bug?
                 Project: GNU Octave
            Submitted by: sebald
            Submitted on: Mon 02 Mar 2015 07:07:45 AM GMT
                Category: Plotting with OpenGL
                Severity: 3 - Normal
                Priority: 5 - Normal
              Item Group: Other
                  Status: None
             Assigned to: None
         Originator Name: 
        Originator Email: 
             Open/Closed: Open
         Discussion Lock: Any
                 Release: dev
        Operating System: Any

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Details:

In searching for a bug, I've looked through gl2ps-renderer.cc.  I notice
something here about the routine glps_renderer().  I'm going to raise it
because if this code is interruptable, there is potential for a rare obscure
bug that would be very hard to duplicate and find if some user were to report
it.

There is this construct:


glps_renderer::draw (const graphics_object& go, const std::string print_cmd)
{
  static bool in_draw = false;

  if (!in_draw)
    {
      in_draw = true;
...

  in_draw = 0;
  ret
}


If this code can be interrupted, there is the rare event possibility that the
user hits Cntrl-C at a time that corresponds to the in_draw variable value
being 1.  If so, from that point forward this draw routine will not behave
correctly if the user follows up with some related command.  Very rare, I
know, but rare bugs are the worst kind.

So, if that is an issue, how to fix?  Well, there should be some way of
reseting that static variable, or more likely make it a private class variable
and reset it to zero every time it is first used.  Keep the recursive portion
separate from the.


public
  draw();
private
  draw_recurse();
  int in_draw_rec;



  ::draw() {
    in_draw_rec = 0;
    draw_recurse();
  }

  ::draw_recurse() {
    in_draw_rec = 1;
    draw_recurse(go);
  }


one could do the same sort of thing with an input value:


  ::draw() {
    draw_recurse(go, 0);
  }

  ::draw_recurse(xyz, state) {
    draw_recurse(go, state+1);
  }


I may not have that right, but I'm not quite sure how it is intended to work
because of the virtual functions and all.  There might be a better way of
doing this as well.  I haven't thought too much about it.





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