[Qt-interest] QScriptEngineDebugger crash

[Kent Hansen]

Hi Dave,

Dave Ceddia skrev:
> I've noticed a crash when using QScriptEngineDebugger. Maybe the way 
> I'm using it is odd, but I have a checkbox in my GUI that enables or 
> disables the debugger, and when running a script, a new debugger will 
> be allocated and attached to the script engine. When the script has 
> completed, the debugger will be detached and destroyed. This way, the 
> state of the checkbox does not directly affect the existence of a 
> debugger object.
>
> What I'm noticing is that if I create a debugger, attach it, run the 
> script, and detach it, the debugger will replace the engine's print() 
> function with its own trace function, and the engine's print() 
> function will never return to its normal state (see 
> QScriptDebuggerBackend::attachTo and QScriptDebuggerBackend::detach in 
> Qt's src/scripttools/debugging/qscriptdebuggerbackend.cpp). Because of 
> this, if I then run a script without a debugger attached, the program 
> will segfault when I try to print() from a script.
>
> My workaround right now is to save the engine's print function right 
> after I create the engine:
>      QScriptValue oldPrintFunction = 
> engine->globalObject().property("print");
> Then, when I detach and delete the debugger, I set the engine's print 
> function back to normal:
>      engine->globalObject().setProperty("print", oldPrintFunction);
>
> This seems to work fine so far, but it seems more like a bug than 
> expected behavior...

I believe this is fixed with 
http://qt.gitorious.org/qt/qt/merge_requests/554. The change will be in 4.6.

Regards,
Kent