Help: 64bit python call c and got OSError: exception: access violation writing 0xFFFFFFFF99222A60

[Random832]

On Mon, Jan 22, 2018, at 16:00, Jason Qian via Python-list wrote:
> Hello!
> 
>   I am using ctypes on Windows to interface with a dll  and it works fine
> on Linux and windows 32-bit python.  But, when using 64-bit python, we got
> error "exception: access violation writing 0xFFFFFFFF99222A60".

You are treating the obj type (myPythonAPI *) as c_int, which is only 32 bits. You should be using a pointer type instead (ideally you should be using void * and c_void_p, so Python doesn't need the class definition.) Don't forget to set lib.loadInstance.restype as well.

> __declspec(dllexport) myPythonAPI* loadInstance(){ return new
> myPythonAPI(); }
> __declspec(dllexport) int createService(myPythonAPI* obj, const char*
> serviceName) { eturn obj->createService(serviceName);

> lib = cdll.LoadLibrary('xxxxxxx.dll')
> 
> lib.createService.argtypes=[c_int,ctypes.c_char_p]
> lib.createService.restype=ctypes.c_int
> 
> class myDriver(object):
> def init(self):
> self.obj = lib.loadInstance()