Python is passing 32bit pointer address to C functions

Question

I would like to call my C functions within a shared library from Python scripts. Problem arrises when passing pointers, the 64bit addresses seem to be truncated to 32bit address

Answer 1

If you don't tell ctypes what type the parameters are, it attempts to infer it from the values that you pass to the function. And this inference will not always work as you need.

The recommended way to deal with this is to set the argtypes attribute of the function and so explicitly tell ctypes what the parameter types are.

plate.plate.argtypes = [
    ctypes.POINTER(ctypes.c_float), 
    ctypes.POINTER(ctypes.c_float), 
    ctypes.c_int
]

Then you can call the function like this:

plate.plate(x.ctypes.data, y.ctypes.data, N)