#if defined(QT_X11_DEFINES_FOUND) in qcborstreamreader.h problem

in qcborstreamreader.h there is

// See qcborcommon.h for why we check
#if defined(QT_X11_DEFINES_FOUND)
#  undef True
#  undef False
#endif

and in qcborcommon.h

#if defined(False) && defined(True)
#  define QT_X11_DEFINES_FOUND 1
#  undef True
#  undef False
#endif

This can lead to includes order hell, if True/False isn't defined when qcborcommon.h is included which QJsonValue does.
my example is using live555 which defines True/False. If live555 includes do not come before any Qt includes which leads to qcborcommon.h, than the above in  qcborstreamreader.h will not undefine True/False.

Besides the point using True/False in an enum is poor practice, bridging these #if defined will certainly force a includes order. Proper practice is to also check True/False in qcborstreamreader.h