I have a few simple .c programs that look something like this

example.c:

#include <stdlib.h>
#include <stdio.h>
#include <setter.h>

char *storage = NULL;

char *get_storage() {
    return storage;
}

void update_storage(char *new) {
    set_storage(new);
}

int main(void) {
    return 0;
}

setter.h:

void set_storage(char *new_string);

setter.c:

#include <setter.h>
#include <string.h>
#include <stdlib.h>

extern char *storage;

void set_storage(char *new_string) {
    if (storage == NULL) {
        storage = malloc(sizeof(char) * 13);
    }
    memcpy(storage, new_string, 13);
}

Which I compile like so:

gcc -shared -o example.so -fPIC example.c setter.c -I.

I then have a simple python script that loads this .so file and tries to execute the update_storage and get_storage functions.

import ctypes

libds = ctypes.CDLL('./libexample.so')
libds.update_storage.argtypes = [ctypes.c_char_p]
libds.get_storage.restype = ctypes.c_char_p

libds.update_storage(ctypes.create_string_buffer("Hello World!".encode()))
res = libds.get_storage()
print(res)

However when I run the Python script I get the following error. Does anyone know why?

AttributeError: ./libexample.so: undefined symbol: update_storage