Re: [Texmacs-dev] TeXmacs crashing on Qt 4.4

[Alvaro Tejero Cantero]

Just tried the last CVS on my Ubuntu 32 bit system with QT 4.3.4.

Great  progress!!

In particular:

- iconbars not repainted as often (but still more polish is needed)
- open dialog works for me
- Ctrl and Alt seem to work fine


Some stuff that was not working:

- unchecking an iconbar from "View" and readding paints an empty icon
bar. Moving (or just shaking) those "empty" icon bars restores the
visibility of the icons.

- no pictures (tested jpg, png, eps) just <error|bad postscript|0> was rendered.

- no remote opening of http://en.wikipedia.org/wiki/Probability_theory
  (minibuffer says 'Error: http:Probability_theory not found')

- drawing mode can draw grids, but cursor does not get deleted fast
enough from previous positions, and elements are not added.

- full screen mode kills the editor

- right click (for the contextual menu) shuts texmacs down
   (Fatal error: cannot handle slot type in
'qt_view_widget_rep::query', backtrace at the end of msg)
  see backtrace attached.

As a side note, the current right-click menu is not very useful since
it is actually not contextual, so maybe a good compromise would be to
just ignore this event. It is only *needed* when one wants to switch
back from presentation mode.

Right click actually did not crash texmacs in the draw mode


Cheers,

Álvaro.

On Wed, Oct 8, 2008 at 19:02, Henri Lesourd <address@hidden> wrote:
> Massimiliano Gubinelli wrote:
>
>> Hi all,
>> I've fixed some problems with the Qt port but it continues to crash
>> on my Linux  machine with Qt 4.4. I've tried to cook up test programs
>> to make Qt crash the same way TeXmacs make it crash but without
>> success. Finally I've tried to compile Qt 4.4.3 without sse2 support
>> (-no-sse2 during configure) and it works fine without crashes. So I
>> think something weird is going on and that we should report to
>> Trolltech for a possible bug in Qt. Somebody could try the last CVS on
>> other Linux boxes and report if it works or crashes? thanks.
>> Apparently there is another problem linked with 64 bits but now I'm
>> concerned with a crash affecting 32 bit machines causing TeXmacs to
>> crash while opening the "Open File" dialog box. The exact point of the
>> crash is while performing some sse2 optimized operation in
>> QImage::fill.
>>
>> Somebody has suggestions in how to proceed ?
>>
>
> Very clearly, there are also current (and relatively
> long lasting, i.e., last November, probably) problems
> in TeXmacs itself due to reference counting and memory
> allocation. These problems are highly in need of a fix.
>
> Without *first* being sure that these problems have
> been eradicated, it will be difficult to completely
> test a GUI library which, as a matter of fact, depends
> on code having such problems.
>
> Especially:
>
> 1. The "close buffer" crash problem, which is related
>  to a redundant delete instruction. To my knowledge,
>  this instruction has only be commented out, but this
>  does not addresses the underlying root cause ;
>
> 2. The way the Scheme GUI code of TeXmacs is all
>  the time creating new widgets. There are different
>  approaches to manage this, which all involve dealing
>  with reference counting in the TeXmacs code, *plus*
>  knowing how (and when) to free (or reuse, e.g. to
>  avoid blinking) the Qt objects.
>
>  As far as I remember my own code, this part was
>  tricky, because on the one hand subtle bugs can
>  exist in the TeXmacs code, and on the other hand,
>  memory leaks of one kind or another can appear
>  on the Qt side, not only because you would have
>  bad pointers or crush memory for some reason (e.g.:
>  using a Qt method in a way which looks correct,
>  but in fact is not for subtle reasons, e.g. C++
>  references), but also because of timing problems:
>  in designing the main loop, I observed that the
>  Qt library is relatively fragile if you enter
>  the main Qt loop, then leave, then reenter, etc.
>  at a too high frequency.
>
>  I devised a solution which does not raises such
>  concerns, but still, not everything is perfect
>  in the Qt library, there are ways to crash Qt
>  which should not be possible ;
>
> To summarize: in my experience, we are in front
> of two chunks of code which are slightly unstable,
> and heavily under pressure (high bandwidth of
> creating/deleting GUI elements) from TeXmacs.
>
> Thus being sure that at least the TeXmacs side
> is 100% clean seems to be an important prerequisite.
>
> It's only later that fine tuning our understanding of
> how the different Qt versions work would make sense.
>
> Best, Henri
>
>
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