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Debugging

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hylke

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1

Saturday, August 13th 2005, 12:56pm

Debugging

Hello,
When I run my program I'm getting this error:

Quoted

QPaintDevice: Must construct a QApplication before a QPaintDevice

I know it meens that I'm drawing something, but my windows isn't created yet.
Because my program is quite large(lots of classes), I haven't found the place where the problem is caused.
So my question is, is there some tool/debugger that can help me trace the place in which the error is caused(in example, in which function)?
Thanx in advance,
Hylke
Duh

dimitri

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Saturday, August 13th 2005, 4:58pm

RE: Debugging

Use a debugger and put a breakpoint in the Qt library where the error message is printed. Unfortunately you need a debug Qt library for that.

hylke

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3

Sunday, August 14th 2005, 8:44am

So there's no easy way to 'just' debug it?
Duh

hylke

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4

Sunday, August 14th 2005, 9:31am

valgrind was the tool that I was looking for.
It found the exact place.
Duh

dimitri

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Sunday, August 14th 2005, 9:34am

Maybe it works without a debug version of the Qt library. Try adding a breakpoint in the QWidgetPrivate constructor - provided the QPaintDevice is a QWidget. By the way, I can't find the error message you're refering too in the Qt sources:

Quoted

QPaintDevice: Must construct a QApplication before a QPaintDevice

I was only able to find:

Quoted

QPixmap: Must construct a QApplication before a QPaintDevice
QWidget: Must construct a QApplication before a QPaintDevice
QPrinter: Must construct a QApplication before a QPaintDevice

hylke

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6

Sunday, August 14th 2005, 10:18am

Thank you for yout reply.
But valgrind was all I needed :-)
Duh

anda_skoa

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Sunday, August 14th 2005, 11:27am

Just for the interested:

This usually happend if one has a static member which is a QPaintDevice.

It gets created before the main() functions executes and creates the QApplication instance.

Cheers,
_
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