freemelater.c

/* Jeroen Ooms 2015
 * Example of queueing objects to be free later with their corresponding
 * free() function.
 */
#include <stdlib.h>
#include <stdio.h>

struct node {
  void (*fun)(void *target);
  void *ptr;
  struct node *parent;
};

struct node *head;

#define freemelater(...) freemelater_generic((void*) __VA_ARGS__)

void freemelater_generic(void *fun, void *ptr){
  struct node *x = malloc( sizeof(struct node) );
  x->parent = head;
  x->fun = (void(*)(void*)) fun;
  x->ptr = ptr;
  head = x;
}

void gofreethings(){
  while(head != NULL){
    struct node *old = head;
    head->fun(head->ptr); //free the target object
    head = head->parent;
    free(old); //free the node struct itself
    printf("freeing something...\n");
  }
  printf("clean up done.\n");
}

int main(){
  /* alloc and queue cleanup */
  void *foo = malloc(1000);
  freemelater(free, foo);

  /* alloc and queue cleanup */
  int *bar = (int*) malloc(1000);
  freemelater(free, bar);

  /* alloc and queue cleanup */
  unsigned char *baz = malloc(1000);
  freemelater(free, baz);

  /* run cleanup */
  gofreethings();

  /* alloc and queue cleanup */
  void *test1 = malloc(1000);
  freemelater(free, test1);

  /* alloc and queue cleanup */
  int *test2 = (int*) malloc(1000);
  freemelater(free, test2);

  /* run cleanup */
  gofreethings();

  return 0;
}