kicad-developers team mailing list archive

[Cirilo Bernardo <cirilo.bernardo@xxxxxxxxx>]

Thanks Orson,

 Perhaps this patch should be held back for now.  Mario reported that he
fixed this problem in his new 3DViewer branch, but I don't know the
details. Everything works of course if the GL context is not deleted but
then we have a memory leak.

- Cirilo

On Tue, May 24, 2016 at 5:29 PM, Maciej Sumiński <maciej.suminski@xxxxxxx>
wrote:

> Hi Cirilo,
>
> I am wondering whether it really solves the problem. C++ standard ([1],
> 5.3.5.2) explicitly permits null pointer to be an argument for delete,
> so it should not crash there.
>
> I am afraid the problem might be a bit more entangled. Mario & me have
> already noticed a few cases when an OpenGL context switch occurs before
> a destructor is called, and as the result OpenGL resources are being
> freed in a wrong OGL context.
>
> It happens because wxWidgets does not permit setting OpenGL context when
> the parent window is invisible [2]. The second reason is delayed
> wxDialog destruction [3], so we cannot control when it exactly happens,
> and almost surely the destructor will be called when the window is
> already invisible. Due to that, the following might happen (Mario has
> discovered it):
>
> 1. Display a modal dialog with a OpenGL canvas that uses a different
> context
> 2. Switch OpenGL context to the just created canvas
> 3. Close the modal dialog (it is not destructed yet)
> 4. Return to pcbnew, switch OpenGL context to GAL
> 5. The dialog destructor is called - officially you cannot switch the
> context now, as the dialog is invisible, so you are stuck in the GAL OGL
> context. Freeing OGL resources allocated in the dialog will fail,
> because it is a wrong context.
>
> For the moment I do not have any good ideas how to solve the problem in
> a clear way.
>
> Regards,
> Orson
>
> 1. http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2011/n3242.pdf
> 2.
>
> http://docs.wxwidgets.org/stable/classwx_g_l_canvas.html#a9f9ab3909606484e717904064d4e7b4f
> 3.
>
> http://docs.wxwidgets.org/trunk/overview_windowdeletion.html#overview_windowdeletion_sequence
>
> On 05/23/2016 11:35 PM, Cirilo Bernardo wrote:
> > The attached patch fixes bug #1572567 (crash on exit from
> > 3D Footprint Properties dialog). Since there was no check
> > before deleting m_ogl_3dmode, delete can be called on
> > NULL.
> >
> > - Cirilo
> >
> >
> >
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