ASSERT: "width > 0.0" in file painting\qrasterizer.cpp, line 742

Avalon

Hi,
Have used Qt on Linux for a while. I have an application that runs perfectly on Linux and now I have recompiled in Windows 7. All seems to run correct except for drawing in a scene when I call QGraphicsScene::update I get the error :

I can't find any/much info on what the issue is or how to fix it.

Qt Version is:
Qt Creator 3.4.2 (opensource)
Based on Qt 5.5.0 (MSVC 2013, 32 bit)

Any help. Thanks

Red Baron

I'm running 64bit Windows 10 and go the same error. I have followed the bread crumbs to the bug QTBUG-19929 because I was getting

QPainterPath::moveTo: Adding point where x or y is NaN or Inf, ignoring call
QPainterPath::lineTo: Adding point where x or y is NaN or Inf, ignoring call

every once in a while when moving my QGraphicsLineItem in my scene. Sometimes it even results in a crash:

ASSERT: "width > 0.0" in file painting\qrasterizer.cpp, line 761
...
(Internal error: pc 0x113056a in read in psymtab, but not in symtab.)
(Internal error: pc 0x113056a in read in psymtab, but not in symtab.)
(Internal error: pc 0x1130556 in read in psymtab, but not in symtab.)
(Internal error: pc 0x113056a in read in psymtab, but not in symtab.)
(Internal error: pc 0x113056a in read in psymtab, but not in symtab.)
(Internal error: pc 0x113056a in read in psymtab, but not in symtab.)
(Internal error: pc 0x113056a in read in psymtab, but not in symtab.)

I have no idea where this is coming from exactly although I have to admit that my line isn't drawn like I wanted to that is the scene gets bigger and bigger.

kshegunov

@Red-Baron @Avalon

Hi,
When you trip the assertion do extract the stack trace, so at least we can see what chain of calls leads to the crash.

Kind regards.

Red Baron

@kshegunov If I only knew how to do that on Windows (Windows 10 in particular)...

kshegunov

@Red-Baron
Hi,
Are you running the code through the debugger? What IDE are you using?

In QtCreator (I'm using gdb) after failing the assert you can click Ok (you should have, a button Ok / Continue / Ignore). After that the debugger would have stopped at the offending line:

Notice the assertion message top right (I have intentionally accessed a vector element outside the allocated size).
Going to the Stack view window and clicking with the right button you have Create full backtrace:

This should get you started. Inspecting the stack by yourself can also be helpful, as it can hint why (or how) you arrive at the problem.

Kind regards

Red Baron

Thanks. Will get to it in the next couple of days.