[vtkusers] vtkOpenGLClearErrorMacro() never returns

[Bill Lorensen]

It seems risky to have glGetError in a while loop without a guard to stop
the loop. According to the open GL Super Bible, the safe way to clear the
error is:
GLenum glError;
unsigned int i = 0;
  do
    {
    glError = glGetError();
    ++i;
    }
  while(i < 6 && glError != GL_NO_ERROR);

I have see some docs that say there can be more  error codes. Certainly,
some upper bound should be set.

I'll prepare a patch.






On Tue, Apr 15, 2014 at 5:58 AM, Richard Whitehead <
richard.whitehead at vivosight.com> wrote:

> Marco,
> Thanks for the support!  I only get it on one of my computers, where
> OpenGL is issuing warnings, but then the purpose of this code is to clear
> warnings...  It simply doesn't work.  Hopefully someone who knows what it's
> doing could fix it.
> Thanks again,
> Richard
>
>
> On 15 April 2014 10:49, Marco Sambin <m.sambin at gmail.com> wrote:
>
>> Hi Richard,
>>
>> quite a while ago, while I was making experiments with the use of JOGL
>> with VTK under Windows, I encountered the same issue that you describe.
>>
>> Basically, in some cases my application got stuck, and the CPU usage went
>> up to 25% (I have a quad core processor on my dev PC). I discovered this
>> was due to a "vtkClearOpenGLErrors()" call in the rendering pipeline, which
>> was iterating indefinitely in its "while" loop. Not sure what was the real
>> cause of this, did not have the time to debug in detail. At that time, I
>> worked around the problem by setting the VTK_REPORT_OPENGL_ERRORS option to
>> "false" on CMake (which forces the implementation of vtkClearOpenGLErrors()
>> to be empty). I understand that this may not be a viable workaround in your
>> case, and I also believe it would be good to understand the real cause for
>> this infinite loop inside vtkClearOpenGLErrors().
>>
>> But for now, I can only let you know that "you are not alone" ;-)
>>
>> Maybe someone else on the list can shed some more light or share some
>> experience about this issue.
>>
>> Best regards,
>>
>> Marco
>>
>>
>>
>> On Mon, Apr 14, 2014 at 1:04 PM, Richard Whitehead <
>> richard.whitehead at vivosight.com> wrote:
>>
>>>
>>> This new macro was introduced in 6.1.0.  It is getting called when my
>>> app exits and it sits in an infinite loop.
>>> The documentation say is t is supposed to silently clear errors, but it
>>> is not doing this.
>>>
>>> Please can anyone suggest how to fix it?  Since my app is closing I am
>>> willing to discard errors, but the only method I can see that should clear
>>> errors is, well, vtkOpenGLClearErrorMacro...
>>>
>>> Many thanks,
>>>
>>> Richard
>>>
>>>
>>>
>>>
>>> --
>>>
>>> Richard Whitehead *–* Senior Imaging Engineer
>>>
>>> *Michelson Diagnostics Ltd*
>>>
>>> *M:* +44 (0)7905 955276   *T:* +44 (0)20 8308 1695
>>>
>>> *E: *richard.whitehead at vivosight.com   *W:* www.vivosight.com
>>>
>>>
>>> <http://www.vivosight.com/>
>>>
>>>
>>> Michelson Diagnostics Ltd, 1 Grays Farm Production Village, Grays Farm
>>> Road, Orpington, Kent  BR5 3BD, UK
>>>
>>> Registered Office: 3 Shearwater, Maidstone, ME16 0DW.     Registered in
>>> England No. 5732681
>>>
>>> _______________________________________________
>>> Powered by www.kitware.com
>>>
>>> Visit other Kitware open-source projects at
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>>
>
>
> --
>
> Richard Whitehead *–* Senior Imaging Engineer
>
> *Michelson Diagnostics Ltd*
>
> *M:* +44 (0)7905 955276   *T:* +44 (0)20 8308 1695
>
> *E: *richard.whitehead at vivosight.com   *W:* www.vivosight.com
>
>
> <http://www.vivosight.com/>
>
>
> Michelson Diagnostics Ltd, 1 Grays Farm Production Village, Grays Farm
> Road, Orpington, Kent  BR5 3BD, UK
>
> Registered Office: 3 Shearwater, Maidstone, ME16 0DW.     Registered in
> England No. 5732681
>
> _______________________________________________
> Powered by www.kitware.com
>
> Visit other Kitware open-source projects at
> http://www.kitware.com/opensource/opensource.html
>
> Please keep messages on-topic and check the VTK FAQ at:
> http://www.vtk.org/Wiki/VTK_FAQ
>
> Follow this link to subscribe/unsubscribe:
> http://www.vtk.org/mailman/listinfo/vtkusers
>
>


-- 
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