Re: SIGSEGV from qwt3diodummy constructor

[Andreas H. <an...@xs...>]

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Hi!

Micha Bieber schrieb:
|>What was the reason for the problem?
|
|
| The dummy object, any doubts ... :->
| My guess:
|
| We have a chain:
|
| app -> qwtplot3d.dll/so -> qt.dll/so
|
| Qt has to initialize some of its structures (QString ?). The
| construction for the qwt3d static object happens too early. Perhaps the
| qt shared library isn't full available/initialized at this point yet.
| Similar for destruction. I don't know and seeing the topic-relevant
| discussions in the net, I have to admit that I'm not even eager to know
| why ... .

Oh well... ;-)

But this all doesn't explain at least two things:

a) why doesn't the crash on LabPlot happen on all systems
b) why doesn't the crash happen on other qwtplot3d applications

I don't know what the c++ standard says about construction
of global static objects, but it seems to be system (compiler?)
dependent. I think I might check the gcc mailing lists about
this issue...

| Anyway, in order to circumvent the problem, I moved all needed static
| stuff inside functions (it's a common pattern). So whatever will be used
| is constructed first in place when the function is called for the first
| time. Because main runs then, order of initialization issues shouldn't
| be longer an issue.
|
This might be better practice anyway: global objects are ugly ;-)

Many thanks for your support!

I'll inform the LabPlot maintainer about this development
and I think he might use the new qwtplot3d version as soon
as it is officially available.

- - andreas

PS: do you plan to add the neccessary adminstrative files
for the usual "configure; make; make install" commands to
your library? That would make it much easier to create
installable packages of qwtplot3d and would perhaps
eliminate the need for integrating the sources directly
it into LabPlot.

- --
Andreas Haumer                     | mailto:an...@xs...
*x Software + Systeme              | http://www.xss.co.at/
Karmarschgasse 51/2/20             | Tel: +43-1-6060114-0
A-1100 Vienna, Austria             | Fax: +43-1-6060114-71
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