How to pass in different function pointers into atexit in c?

November 23, 2021

I understand that atexit() takes in a function pointer of this type void (*function)(void). What I want to do is that whenever the porgam exists it runs a function to free of all the memory. So I want atexit() to take in this function pointer instead
void (*function)(struct Node). Is there a way around this, or something similar that will allow me to do this.

>Solution :

You could add your own register for cleanup functions:

typedef void atexit_f(void*);
void my_atexit(atexit_f* callback, void *data);

The register would be kept in a global variable (i.e. linked list).
The register would be cleaned up in a cleanup function registered with atexit().

struct cleanup_node {
   atexit_f *cb;
   void *data;
   struct cleanup_node *next;
};

static struct cleanup_node *head;

void my_atexit_cleanup(void) {
  for (struct cleanup_node *node = head; node; node = node->next) {
     node->cb(node->data);
  }
  // free nodes itself
}

...

int main() {
  atexit(my_atexit_cleanup);
  ...
  my_atexit(some_function, some_data);
}