[Qt-interest] The pains of debugging on Windows - Random 'ASSERT' crash on the QList [] operator

[william.crocker at analog.com]

Andre Somers wrote:
> Josiah Bryan wrote:
>   
>> I apologize for the vagueness of this post - I'll get the exact message 
>> next time I'm at the location. However, I've been vexed by this problem 
>> this week and I'm trying to reproduce the problem on Linux - to no avail.
>>
>> Bottom line: The program I'm using randomly crashes with an assert 
>> failure on the [] operator saying something about index out of range, 
>> IIRC. The thing is, this on Windows, and when I run it in the Qt Creator 
>> debugger, after the assert failure, no stack is available to see where 
>> the failure came from. I have not tried running it under the command 
>> line gdb yet on windows - but the last time I did under gdb (for a 
>> different problem), the stack came back looking like:
>>
>> 0x038512 blah blah /blah/kernel.dll
>> 0x029381 ?? ()
>> 0x082385 ?? ()
>> ...
>>
>> E.g. no stack info for anything in my code or in Qt (Yes, it was a debug 
>> build!)
>>
>> So, my main methods of debugging - gdb and Qt Creator - both seem to be 
>> useless. (common problem on windows I've experienced, not just with this 
>> problem.) For any serious debugging, I've used Linux + gdb - works great 
>> when it crashes. However, I can't get it to crash on Linux, no matter 
>> how much fuzzing I throw at it, no matter how I try to re-create the 
>> problem. So I'm left debugging on windows.
>>
>> Anyone have any suggestions on how to better use the built-in Qt Creator 
>> debugger when the program randomly crashes, or get 'gdb' on the command 
>> line showing useful stack info?
>>
>> Thanks for your time everyone.
>>   
>>     
> I know where you're comming from; I run into similar issues sometimes 
> myself.
> There is a switch you can use to turn on fatal warnings. In your run 
> environment, define the QT_FATAL_WARNINGS variable. That has helped me 
> sometimes. Still, I wish there was a way to make ASSERTS go away and 
> just trigger a proper crash I can debug.
>
>   

Install your own message handler with  qInstallMsgHandler and then set a 
break there or
call a special, empty function named stop_here() from your message 
handler and
from all "throw" contexts to give you one convenient place to set a 
break point for all.

> André
>
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