I’m trying to utilize a C library using ctypes in Python. The C library provides a subroutine that returns two arrays via pointers: one for integer data and one for float data.

Here’s a simplified example of my Python code:

import ctypes
import numpy as np

lib = ctypes.CDLL('./reader.so')  # Assicurati di sostituire con il percorso corretto della tua libreria

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

data_ptr = ctypes.POINTER(ctypes.c_int)()
xyz_ptr = ctypes.POINTER(ctypes.c_float)()
readdata(ctypes.byref(data_ptr), ctypes.byref(xyz_ptr))

size = 17  # Dimensione dell'array
data = np.frombuffer((ctypes.c_int * size).from_address(ctypes.addressof(data_ptr.contents)), dtype=np.int32)
xyz = np.frombuffer((ctypes.c_float * size).from_address(ctypes.addressof(xyz_ptr.contents)), dtype=np.float32)

print("Dati integer:", data)
print("Dati float:", xyz)

libc = ctypes.CDLL(None)
libc.free(data_ptr)

This is the code of the fortran module (reader.so):

subroutine readdata(data1, data2) bind(c, name='readdata')
    use iso_c_binding
    implicit none
    
    integer(c_int), intent(out), dimension(:), allocatable :: data1
    real(c_float), intent(out), dimension(:), allocatable :: data2
    
    integer :: length, i
    
    length = 17  ! Esempio di dimensione, sostituire con la dimensione effettiva
    allocate(data1(length))
    allocate(data2(length))
    
    ! Assegna dati casuali all'array di interi data1
    do i = 1, length
        data1(i) = i * 10  ! Modifica questo assegnamento con la logica desiderata
    end do
    
    ! Assegna dati casuali all'array di float data2
    do i = 1, length
        data2(i) = real(i * 10, kind=4) 
    end do
    
end subroutine readdata

The problem is that I’m encountering an error when trying to convert the pointers into numpy arrays. I suspect that the pointers might be close to each other and may cause memory overlap issues.

I’ve tried rearranging the operations and manually deallocating memory, but I haven’t been able to resolve the issue.

Could someone help me understand how to properly solve this problem of converting C pointers to numpy arrays in Python?

Thank you in advance for any assistance!