qmetatype.h -> error: constexpr variable 'len' must be initialized by a constant expression

[Lillo]

Hello, i have a QT3D project made in QT5.14.2 and i wanted to be able to run it in with Qt6.2, but in the build step i have this error in the qt file qmetatype.h. If someone can help me i would appreciate it very much. I attach a screenshot with the error.

[sierdzio]

Try porting to Qt 5.15 first, it should print you some nice deprecation and porting messages during compilation and at runtime. This will help you fix the issues.

A wild guess in this case: Qt 6 requires Q_PROPERTY types to be fully qualified (not forward declared). Go through your properties and make sure it's true.

[alirezaa]

@Lillo
I have just faced the same issue, when trying to port my project to Linux and using Qt 6.8.1.
I noticed, that you have marked this topic as solved; then could you please elaborate on how, you've managed to resolve this issue and what the exact cause was?
Many thanks, in advance

[jsulm]

@alirezaa Did you follow what @sierdzio suggested?

[alirezaa]

@jsulm
I did check all Q_PROPERTY types in my project and didn't detect the possible issue @sierdzio had mentioned in any of them, but haven't tried first porting my project to Qt 5.15 yet, but I will.