My Qt 6.6.0 code crashs in debug mode (~QArrayDataPointer()) and not on release on Windows

[Nelson numerical software]

Thank you for these comprehensive comments. :)

Great work from the developers for this 6.6.0 with many new features.

I have my answer

[Christian Ehrlicher]

Your pragma(lib) stuff in dllmain.cpp is wrong. You must not mix debug and release libraries on windows. I would remove this MSVC only stuff and let do cmake the correct things.

[Nelson numerical software]

@Christian-Ehrlicher said in My Qt 6.6.0 code crashs in debug mode (~QArrayDataPointer()) and not on release on Windows:

Your pragma(lib) stuff in dllmain.cpp is wrong. You must not mix debug and release libraries on windows. I would remove this MSVC only stuff and let do cmake the correct things.

I confirm that it was the trouble

on windows debug build must be linked with Qt debug library

Thanks for your time and investigations

[OnkarP]

Can you explain what you changed to fix this issue ?
As I am also facing the similar problem. I am using already built MSVC 2019 64 bit compiled libraries from QT 6.6.3 with VS 2022 C++ 64 bit application. My application is wrote for Debug and Release configuration. In both modes the crash is happening.

[KeithS]

Thanks @Nelson-numerical-software I had the exact same problem too. Easy mistake to make in Visual C++ when updating Qt versions and modifying linker input file list.

[Christian Ehrlicher]

@KeithS said in My Qt 6.6.0 code crashs in debug mode (~QArrayDataPointer()) and not on release on Windows:

and modifying linker input file list.

That's the reason to use a build system like e.g. CMake.

[WaldemarH]

Hi guys. I just came to the same issue on 6.8.2 where even the code below crashes on exactly the same space as above where the code run perfect before. So what changed... the build was done on w10 (months ago) and then after a format w11 was installed with a clean VS2022 installation. Since this happened qt crashes all the time. Now project didn't change so w10->w11 transition has to be the culprit. I'll edit this post after I'll rebuild 6.8.2 on w11.

int main( int argc, char *argv[] )
{
QVector<JSON_Object> value_object_list;

JSON_Object		e1;
JSON_Object		e2;
JSON_Object		e3;
JSON_Object		e4;
JSON_Object		e5;

value_object_list.append( e1 );
value_object_list.append( e2 );
value_object_list.append( e3 );
value_object_list.append( e4 );
value_object_list.append( e5 );

[Christian Ehrlicher]

Don't mix debug and release libraries.

[snyang]

I found one of my debug dll was compiled by using runtime library MultiThreadedDLL.
After change C/C++ -> runtime library as MultiThreadedDebugDLL in visual studio, the problem is gone.

Use the tool Dependencies, I can see the bad dll is using:

And the good dll is using:

[WaldemarH]

Created a new project, build it and all was fine (the same code). And as stated above the reason was mixing of debug/non-debug libraries.
Now the whole issue as it looks occurred when that Project->Options->Advanced->Use Debug Libraries was set to No (in all VS versions I have never set this value to anything.. I assume it came with VS22). Which caused that Compiler->Code Generation->Runtime libraries switched to non-debug version in the background.

So the solution is to switch the 'Use Debug Libraries' to true and all will be ok.