#include "QVTKInteractor.h"
#include "QVTKInteractorAdapter.h"
@@ -225,6 +227,7 @@ void QVTKOpenGLNativeWidget::initializeGL()
{
if (auto* symbol = context->getProcAddress(name))
{
+ std::this_thread::sleep_for(std::chrono::milliseconds(500));
return symbol;
}
}
```
Though this patch does not fix the root cause of race condition.
---
### Author:  [@mwestphal](https://discourse.paraview.org/u/mwestphal)
#### Post date: [June 18, 2025, 8:04am UTC](https://discourse.paraview.org/t/possible-race-condition-in-qvtkopenglnativewidget-initializegl/16823/2 "2025-06-18T08:04:15Z")
@jaswantp @cory.quammen
---
### Author:  [@jaswantp](https://discourse.paraview.org/u/jaswantp)
#### Post date: [June 18, 2025, 1:44pm UTC](https://discourse.paraview.org/t/possible-race-condition-in-qvtkopenglnativewidget-initializegl/16823/3 "2025-06-18T13:44:04Z")
I remember that printing the symbol to console fixed this issue. The null check seemed to have added enough of a delay to fix this segfault. The context should already be current because `vtkOpenGLRenderWindow` calls `MakeCurrent` before the state initialization. It is a mystery because this happens only on macOS.
---
### Author:  [@qbisi](https://discourse.paraview.org/u/qbisi)
#### Post date: [June 18, 2025, 1:54pm UTC](https://discourse.paraview.org/t/possible-race-condition-in-qvtkopenglnativewidget-initializegl/16823/4 "2025-06-18T13:54:50Z")
Yes, printing the symbol did fix this race condition on macos platform for me.
What’s your current approch to fix this problem. Printing something to stdout will contamination the log system and in my opinion is not good.
For now, i would prefer this patch on darwin platform
```auto
diff --git a/GUISupport/Qt/QVTKOpenGLNativeWidget.cxx b/GUISupport/Qt/QVTKOpenGLNativeWidget.cxx
index a0f00debde..2f5ce52ddb 100644
--- a/GUISupport/Qt/QVTKOpenGLNativeWidget.cxx
+++ b/GUISupport/Qt/QVTKOpenGLNativeWidget.cxx
@@ -230,7 +230,7 @@ void QVTKOpenGLNativeWidget::initializeGL()
}
return nullptr;
};
- this->RenderWindow->SetOpenGLSymbolLoader(loadFunc, this->context());
+ // this->RenderWindow->SetOpenGLSymbolLoader(loadFunc, this->context());
this->RenderWindow->vtkOpenGLRenderWindow::OpenGLInit();
}
auto ostate = this->RenderWindow->GetState();
```
and it do work for me.
---
### Author:  [@qbisi](https://discourse.paraview.org/u/qbisi)
#### Post date: [June 23, 2025, 9:58am UTC](https://discourse.paraview.org/t/possible-race-condition-in-qvtkopenglnativewidget-initializegl/16823/5 "2025-06-23T09:58:17Z")
Hi, how did you solve this bug when you packaging paraview on macos. Any recommend method for doing null check without polluting stdout.
---
### Author:  [@jaswantp](https://discourse.paraview.org/u/jaswantp)
#### Post date: [July 2, 2025, 3:27pm UTC](https://discourse.paraview.org/t/possible-race-condition-in-qvtkopenglnativewidget-initializegl/16823/6 "2025-07-02T15:27:41Z")
Hi,
Apologies for the slow response. I think this is not an issue in our macos paraview distribution (haven’t seen anyone report a bug like this).
If you have the time, my suggestion is to build qt using a RelWithDebInfo config and try to understand what is going on here.
---
### Author:  [@cory.quammen](https://discourse.paraview.org/u/cory.quammen)
#### Post date: [July 2, 2025, 3:31pm UTC](https://discourse.paraview.org/t/possible-race-condition-in-qvtkopenglnativewidget-initializegl/16823/7 "2025-07-02T15:31:54Z")
I’m not entirely sure what nullptr check is being done, but perhaps you just loop on that check until it is valid and then proceed?
---
### Author:  [@qbisi](https://discourse.paraview.org/u/qbisi)
#### Post date: [July 2, 2025, 3:32pm UTC](https://discourse.paraview.org/t/possible-race-condition-in-qvtkopenglnativewidget-initializegl/16823/8 "2025-07-02T15:32:37Z")
> [@qbisi](#):
>
> ```auto
> diff --git a/GUISupport/Qt/QVTKOpenGLNativeWidget.cxx b/GUISupport/Qt/QVTKOpenGLNativeWidget.cxx
> index a0f00debde..2f5ce52ddb 100644
> --- a/GUISupport/Qt/QVTKOpenGLNativeWidget.cxx
> +++ b/GUISupport/Qt/QVTKOpenGLNativeWidget.cxx
> @@ -230,7 +230,7 @@ void QVTKOpenGLNativeWidget::initializeGL()
> }
> return nullptr;
> };
> - this->RenderWindow->SetOpenGLSymbolLoader(loadFunc, this->context());
> + // this->RenderWindow->SetOpenGLSymbolLoader(loadFunc, this->context());
> this->RenderWindow->vtkOpenGLRenderWindow::OpenGLInit();
> }
> auto ostate = this->RenderWindow->GetState();
>
> ```
Hi, thans for your suggestion. What if i comment this line and use vtkglad to find the appropriate OpenGL lib on darwin platform. It do works for me, but i am not sure if is has some side effect.
---
### Author:  [@jaswantp](https://discourse.paraview.org/u/jaswantp)
#### Post date: [July 2, 2025, 3:33pm UTC](https://discourse.paraview.org/t/possible-race-condition-in-qvtkopenglnativewidget-initializegl/16823/9 "2025-07-02T15:33:45Z")
The nullptr check refers to [https://gitlab.kitware.com/vtk/vtk/-/blob/master/GUISupport/Qt/QVTKOpenGLNativeWidget.cxx#L226](https://gitlab.kitware.com/vtk/vtk/-/blob/master/GUISupport/Qt/QVTKOpenGLNativeWidget.cxx#L226)
```cpp
if (auto* symbol = context->getProcAddress(name))
{
return symbol;
}
```
---
### Author:  [@jaswantp](https://discourse.paraview.org/u/jaswantp)
#### Post date: [July 2, 2025, 3:39pm UTC](https://discourse.paraview.org/t/possible-race-condition-in-qvtkopenglnativewidget-initializegl/16823/10 "2025-07-02T15:39:18Z")
> What if i comment this line and use vtkglad to find the appropriate OpenGL lib on darwin platform. It do works for me, but i am not sure if is has some side effect.
We kind of want to use the OpenGL functions provided by Qt. But as it is troublesome on macOS, I think it is reasonable to conditionally skip `this->RenderWindow->SetOpenGLSymbolLoader(loadFunc, this->context());` on apple.
---
### Author:  [@qbisi](https://discourse.paraview.org/u/qbisi)
#### Post date: [July 2, 2025, 3:42pm UTC](https://discourse.paraview.org/t/possible-race-condition-in-qvtkopenglnativewidget-initializegl/16823/11 "2025-07-02T15:42:06Z")
```auto
diff --git a/GUISupport/Qt/QVTKOpenGLNativeWidget.cxx b/GUISupport/Qt/QVTKOpenGLNativeWidget.cxx
index a0f00debde..6dd37d3ac2 100644
--- a/GUISupport/Qt/QVTKOpenGLNativeWidget.cxx
+++ b/GUISupport/Qt/QVTKOpenGLNativeWidget.cxx
@@ -225,6 +225,7 @@ void QVTKOpenGLNativeWidget::initializeGL()
{
if (auto* symbol = context->getProcAddress(name))
{
+ qDebug() << "symbol not null";
return symbol;
}
}
```
I had to print something to console to pass the race condition.
Which i think might pollute the stdout.
By the way, i had also build paraview/vtk with serial SMP backend and no mpi.
---
### Author:  [@jaswantp](https://discourse.paraview.org/u/jaswantp)
#### Post date: [July 2, 2025, 3:46pm UTC](https://discourse.paraview.org/t/possible-race-condition-in-qvtkopenglnativewidget-initializegl/16823/12 "2025-07-02T15:46:59Z")
> [@qbisi](#):
>
> I had to print something to console to pass the race condition.
> Which i think might pollute the stdout.
Yeah, I remember having to do that too. But I noticed that the if statement on `symbol` added enough of a delay to fix the race condition and I did not need the print statement.
Apparently, it is still not enough of a delay and needs a print. Can you contribute the fix to VTK which skips setting the opengl symbol loader for macOS?
---
### Author:  [@qbisi](https://discourse.paraview.org/u/qbisi)
#### Post date: [July 2, 2025, 3:51pm UTC](https://discourse.paraview.org/t/possible-race-condition-in-qvtkopenglnativewidget-initializegl/16823/13 "2025-07-02T15:51:44Z")
> [@qbisi](#):
>
> `this->RenderWindow->SetOpenGLSymbolLoader(loadFunc, this->context());`
Another occurance of setting the opengl symbol loader
[https://gitlab.kitware.com/vtk/vtk/-/blob/master/GUISupport/Qt/QVTKOpenGLWindow.cxx?ref\_type=heads#L219](https://gitlab.kitware.com/vtk/vtk/-/blob/master/GUISupport/Qt/QVTKOpenGLWindow.cxx?ref_type=heads#L219).
Should i conditionaly comment this line too ?
---
### Author:  [@jaswantp](https://discourse.paraview.org/u/jaswantp)
#### Post date: [July 2, 2025, 3:52pm UTC](https://discourse.paraview.org/t/possible-race-condition-in-qvtkopenglnativewidget-initializegl/16823/14 "2025-07-02T15:52:48Z")
> [@qbisi](#):
>
> Should i conditionaly comment this line too ?
Yes
---
### Author:  [@jaswantp](https://discourse.paraview.org/u/jaswantp)
#### Post date: [July 2, 2025, 3:53pm UTC](https://discourse.paraview.org/t/possible-race-condition-in-qvtkopenglnativewidget-initializegl/16823/15 "2025-07-02T15:53:32Z")
Something like
```cpp
#if !defined( __APPLE__ )
this->RenderWindow->SetOpenGLSymbolLoader(loadFunc, this->context());
#endif
```
---
### Author:  [@qbisi](https://discourse.paraview.org/u/qbisi)
#### Post date: [July 2, 2025, 4:21pm UTC](https://discourse.paraview.org/t/possible-race-condition-in-qvtkopenglnativewidget-initializegl/16823/16 "2025-07-02T16:21:54Z")
> [@jaswantp](#):
>
> Can you contribute the fix to VTK which skips setting the opengl symbol loader for macOS?
[Skip setting the opengl symbol loader for macOS (!12262) · Merge requests · VTK / VTK · GitLab](https://gitlab.kitware.com/vtk/vtk/-/merge_requests/12262)
I have opened my first commit to vtk. Fix me if i made something wrong.
---
### Author:  [@jaswantp](https://discourse.paraview.org/u/jaswantp)
#### Post date: [July 7, 2025, 3:31pm UTC](https://discourse.paraview.org/t/possible-race-condition-in-qvtkopenglnativewidget-initializegl/16823/17 "2025-07-07T15:31:19Z")
> [@qbisi](#):
>
> I have opened my first commit to vtk. Fix me if i made something wrong.
Thank you for the contribution! i have started the test and will merge after it comes back clean.