[PyQt] Crash when adding a QRegion to a QPainterPath

Phil Thompson phil at riverbankcomputing.com
Tue Jun 8 18:28:19 BST 2010

On Tue, 08 Jun 2010 17:45:59 +0100, Jeremy Sanders
<jeremy at jeremysanders.net> wrote:
> Hi - I have an example program here which used to work in earlier
> releases. Now it causes a core dump:
> #0  QRegion::QRegion (this=0x8f72c0, r=...) at painting/qregion.cpp:3895
> #1  0x0000003ea5ce12ad in QPaintEngineState::clipRegion (this=<value 
> optimized out>)
>     at painting/qpainter.cpp:8470
> #2  0x00007ffff1040157 in meth_QPaintEngineState_clipRegion 
> (sipSelf=0x8c36d0, sipArgs=<value optimized out>)
>     at sipQtGuiQPaintEngineState.cpp:385
> #3  0x0000003eb78dcaba in call_function (f=<value optimized out>, 
> throwflag=<value optimized out>)
>     at Python/ceval.c:3706
> This fails under Fedora 12 x86-64 and on a own-built SIP/PyQt4 under
> i386. I'm using Qt-4.6.2.
> Please download the example program:
>  http://barmag.net/tmp/svg_export.py
> If you uncomment the print statements on lines 175 and 177 the program no

> longer crashes, but state.clipOperation() looks like garbage.

Fixed in tonight's PyQt snapshot.

SIP v4.10.1 included an "improvement" where a copy of a const& argument to
a reimplementation of a virtual is made before wrapping it. This means that
Python code doesn't have to explicitly make a copy if it wants to keep a
reference and avoid potential crashes if the copy isn't made. It seems that
in some cases this is the wrong thing to do - particularly if the argument
is actually an internal sub-class of the advertised type.


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