调用CGPathAddArc时PyQt4 / Qt中止陷阱的原因是什么？

Question

After upgrading to Mavericks, with PyQt 4.10.4, Qt 4.8.5, python 2.7.5, I was trying to rebuild a PyQt application and encountered the following abort trap:

Assertion failed: (CGFloatIsValid(x) && CGFloatIsValid(y)), function void CGPathAddArc(CGMutablePathRef, const CGAffineTransform *, CGFloat, CGFloat, CGFloat, CGFloat, CGFloat, bool), file Paths/CGPath.cc, line 279.
Abort trap: 6

This is issue reflects that CGPathAddArc on Mavericks rejects NaN values from Qt (which on Snow Leopard it used to tolerate/warn about). There is a patch that looks good, but applying it requires rebuilding Qt and PyQt, and I wasn't able to get it to work for me.

faultHandler gives no details, and runsnake yields no output since the app terminates abnormally.

It's obviously a UI element, but how do I find which one?

Answer 1

Culprit was a QGraphicsEllipseItem() declared with no parameters. Qt 4.8 documentation suggests no params is a valid constructor, but apparently in Mavericks this is not the case.

Declaring the QGraphicsEllipseItem with dummy x and y parameters resolved the issue.