Problem with GDB pretty printer when using a class

QtCreator cannot display the value of instances of a C++ class for which there is a gdb pretty printer. The instance in question can be output with p <variable name> in the debugger log, as can be seen in the attached screenshot, but in the window for local variables the corresponding variables are <inaccessible>. ** 

The pretty printer (see libalkimia-gdb.py) is designed to call a method of the associated class and registered in gdb as shown in the debugger log

<521info pretty-printer

>&"info pretty-printer\n"

>~"global pretty-printers:\n"

>~" Alkimia\n"

>~" AlkValue\n"

>~" mpq_class\n"

The issue can be reproduced in QtCreator with the appended cmake test project [^test-gdb-pretty-printer-with-class.tar.gz]