With Python 3, seeing error LP_xyz instance instead of LP_xyz

[sandybandy]

Here's the Python call and exception

attr = xyz()

myfunc(a, b, c, pointer(attr))

Above code runs fine on Python 2, but throws below exception with Python 3.7.4

ERR: argument 4: <class 'TypeError'>: expected LP_xyz instance instead of LP_xyz

C function prototype (also used to generate ctypes) is: myfunc(int a, int b, int c, xyz *p);

[Alan-R]

Several things have changed (bugs fixed) in ctypesgen over the last few years. Are you running the same version of ctypesgen in python 2 as you are running in python 3?

[mara004]

ctypesgen once had an override of the POINTER type factory (and still has with --no-embed-preamble) that destroys type checks. See also #86 (comment) and #26.

It may be related to that. My guess is that the xyz instance created and the xyz type used in the argtypes might actually originate from two separate, duplicate definitions, so they're formally recognized as different.
Use -m / --link-modules to avoid that.