nothing special

foo.c

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

struct array {
  int pos;
  char *pointers[1024];
};

static struct array arr;

int push(char *data) {
  if (arr.pointers[arr.pos] != NULL) {
    free(arr.pointers[arr.pos]);
    arr.pointers[arr.pos] = NULL;
  }

  char *ptr = (char *)malloc(sizeof *data);
  if (ptr == NULL)
    return 0;
  else {
    strcpy(ptr, data);
    arr.pointers[arr.pos] = ptr;
    arr.pos += 1;
    return 1;
  }
}

char* pop(int pos) {
  if (arr.pointers[pos] != NULL) {
    char *ptr = arr.pointers[pos];
    arr.pointers[pos] = NULL;
    return ptr;
  } else {
    return NULL;
  }
}

char* get(int pos) {
  if (arr.pointers[pos] != NULL)
    return arr.pointers[pos];
}

int del(int pos) {
  if (arr.pointers[pos] != NULL) {
    printf("%p\n",arr.pointers[pos]);
    free(arr.pointers[pos]);
    arr.pointers[pos] = NULL;
    return 1;
  }
  // no del occured
  return 0;
}

int main(int argc, char *argv[]) {
  arr.pos = 0;

  int i;
  for (i=0; i<1024; i++)
    arr.pointers[i] = NULL;

  char buf[] = "foo bar";
  printf("the string is: %s\n",buf);

  if (push(buf) == 0)
    printf("push failed\n");

  char *data = get(1);
  printf("array pos: %d\n", arr.pos);
  printf("the string is: %s\n",data);

  char buf2[] = "haha this sucks";
  if (push(buf2) == 0)
    printf("push failed\n");

  char *data2 = get(1);
  printf("the string is: %s\n", data2);

  int j;
  for (j=0; j<1024; j++) {
    if (arr.pointers[j] != NULL)
      printf("pointer at %d is %p\n", j, &arr.pointers[j]);
  }

  
  char *data3 = get(1);
  printf("the string is before pop: %s\n", data3);

  char *ptr = pop(1);
  printf("popped item and it is: %s\n", ptr);
  if (del(0) == 0)
    printf("delete of 0 failed\n");

  printf("new arr pos: %d\n", arr.pos);
  printf("pointer at 0 is %p\n", &arr.pointers[0]);


  return 0;
}