System.AccessViolation

[myl]

After creating a RenderWindow and rendering lots of pretty things, i randomly had this piece of code throwing AccessViolations from the Text constructor.

public int GetTextWidthPixels(string text, Font font, uint fontSize)
{
       var textShape = new Text(text, font, fontSize);
       var bounds = textShape.FindCharacterPos((uint)(text.Length));
       textShape.Dispose();
       return (int)bounds.X;
}

The font is a static loaded resource, but to make sure, I've tested that the constructor doesn't misbehave if I pass null or a disposed Font, so this is not the issue.

I'm wondering if you could share any insight into the things that could be causing this behavior, so i know what to look for.

[Laurent]

Don't you have more detailed information about the exception? Like the call stack, or a human-friendly message?

[myl]

Well, the nature of AccessViolation is not very informative, which is why I'm asking

This is the top of the stack:

System.AccessViolationException: Attempted to read or write protected memory. This is often an indication that other memory is corrupt.
  at SFML.Graphics.Text.sfText_create()
  at SFML.Graphics.Text..ctor(String str, Font font, UInt32 characterSize)

[Laurent]

Make sure that the CSFML DLLs match your version of SFML.Net (do you have several version, or did you update an older version of SFML.Net?).

[myl]

I've just verified that my dlls are the ones that go together out of the 32 bit .Net binary package.

FYI: Don't know if it helps, but I also experienced AccessViolations from the sprite copy constructor. I didn't mention this before because I haven't ruled out that i could be passing disposed sprites yet (which would also cause an AccessViolation).

[Laurent]

Is it only these two calls that fail, or does any call to a sfml-graphics function result in the same thing?

[myl]

I also have reports for

 
at SFML.Graphics.Sprite.sfRenderWindow_drawSprite(IntPtr CPointer, IntPtr Sprite, MarshalData& states)
at SFML.Graphics.Sprite.Draw(RenderTarget target, RenderStates states)
 

and also at

 
at SFML.Graphics.Text.sfRenderWindow_drawText(IntPtr CPointer, IntPtr Text, MarshalData& states)
at SFML.Graphics.Text.Draw(RenderTarget target, RenderStates states)
 

and at

 
at SFML.Graphics.Shape.sfShape_create(GetPointCountCallbackType getPointCount, GetPointCallbackType getPoint, IntPtr userData)
at SFML.Graphics.Shape..ctor()
 

So, pretty much all around. It usually occurs after a few hours of rendering. Profiling doesn't show any mem leaks.

[Laurent]

It usually occurs after a few hours of rendering

Ah. So these functions work, but after a few hours the binding somehow gets unstable, right?

[myl]

Correctly understood.

[Laurent]

Probably a memory issue. Does the memory usage of your app increase over time?

[myl]

Which is what i guessed as well, but the leakeage is minor, if any, after profiling with ants.

[Laurent]

Since SFML.Net invokes CSFML dynamically, the profiler might not see everything that happens there.

[myl]

Hey Laurent.
I can't seem to find any information on sfml memory management in .Net, so I'm wondering how I am supposed to go about this. At first I assumed it was handled for me. But since the Texture destructor makes a Destroy(false) call, this causes a leak. I guess it does this because you don't want to release resources on the GC thread. Is it right to conclude I MUST call Texture.Dispose() on my main thread before loosing the Texture reference to avoid any leaks?
Thanks!

[Laurent]

No it's wrong

SFML resources are always destroyed (look at what Destroy(false) does). When it's done in the GC thread I just instanciate an OpenGL context because there's none.

[myl]

Glad I asked then This minimal example is leaking full on. What am I misunderstanding?

var renderWindow = new RenderWindow(new SFML.Window.VideoMode(200, 200), "I'm a leaker");
while (true)
{
    var texture = new Texture("nonprogressive.jpg");
    var sprite = new Sprite(texture);
    renderWindow.Draw(sprite);
    renderWindow.Display();
    renderWindow.DispatchEvents();
    GC.Collect();
}