Re: [matplotlib-devel] IPython Segfaults (again)

[Charles M. <cm...@in...>]

	It must be some kind of race condition.  I can easily recreate the error on agg 
and non-agg wx and gtk backends (don't have qt).  Here is what I do to cause the 
error fast.

plot(rand(100)) # just to have something up
f = get_current_fig_manager()
f.canvas<hold down tab>
# the key repeat will cause rapid fire on the completion

Straight Gtk periodically spits out something other than seg fault:
"In [6]:f.canvas.Fatal Python error: PyEval_SaveThread: NULL tstate"

Hope this helps,
	Charlie

John Hunter wrote:
>>>>>>"Fernando" == Fernando Perez <Fer...@co...> writes:
> 
> 
>     Fernando> Charles Moad wrote:
>     >> I can't seem to crash TkAgg, but WXAgg and GTKAgg still do.
>     >> This seems to not be related to the repr issue from before.
>     >> This is all mpl-cvs btw.
> 
>     Fernando> OK, I'm afraid this one may require John's help to
>     Fernando> debug.  I don't know the mpl internals nearly well
>     Fernando> enough to even begin to guess where this could be coming
>     Fernando> from.
> 
>     Fernando> The fact that it's a segfault and not an uncaught
>     Fernando> exception means the bug is triggered inside C code.
>     Fernando> <TAB> triggers dir() and getattr() calls, which have to
>     Fernando> traverse the object's internal dictionary.  If the
>     Fernando> object is implemented in C/C++, that traversal can do
>     Fernando> arbitrary things, including any number of
>     Fernando> segfault-inducing manipulations.
> 
> The canvas object (eg FigureCanvasGTKAgg) is implemented in python.
> It inherits from a gtk base class and an Agg base class.  It would be
> useful to test whether you get this behavior on the GTK and WX
> backends (no Agg).  My guess is that this is some is caused by a
> threading problem, but can't be sure.  This would explain why you see
> it with GTKAgg and WXAgg but not TkAgg.
> 
> JDH