You're not the first to tell me so.

Actually,
I'm not sure what is wrong with allocating a Widget / Layout on the stack.

Of course if you use them badly it will most likely crash,
but,
why declaring a layout on an instance's stack would crash anything ?

You're telling me that a widget on the stack won't be properly deleted in the dtor of my classe instances ?

Because for me in C++ and it's common knowledge declaring something on the stack has never crashed anything.