Gdb doesn't see Widget members besides Ui

Compiler details:

Standard GCC MinGW, using QtCreator dumpers versions 1.90 and 1.92. I think this happened as far back as 1.2.1.
The bug is not reproducible with CDB.

Steps to reproduce / test case:

1. Create a Qt GUI app with a main window.
2. Add a push button on the main window and wire it to a slot member function.
3. Add some member variables to the main window. e.g: a, b.
4. Add a breakpoint inside the slot function.
5. Start the debugger and press the button.
6. We are now in the slot function, and the debugger dumps the locals & watches. The "this" variable contains only the Ui_MainWindow member, with no trace of a or b.

Since most domain objects are created as a child of some window or dialog this effectively limits the variable watch to function locals only.