Problems concerning pointers and malloc in C90 - c

Question

I am quite a newbie when it comes to C, and seem to be having a few issues when it comes to memory allocation and pointers. For my assignment, we have to create the ADT of dynamic sets using arrays, and to do this we require heavy use of pointers which I find a bit difficult to grasp.
I created a structure to act as the sets
struct Set{
int arrelement; //the 'size' of the array
int * arrvalue;; //the array
}
typedef struct Set *SetArray;
The issue arises when I come to applying functions such as Add(where I add a unique element to the set) or Cardinality (where the programs shows me the total number of elements in the set). Adding seems to crash my program after more than 2 additions and trying to retrieve the stored data supplies junk variables.
Here is the code for the relevant functions
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "Array.h"
int size = 1; // similar to arrelement, to be used for realloc
SetArray Create(){ // to allocate memory for the set
SetArray sptr;
sptr = malloc(sizeof(struct Set));
sptr->arrvalue = malloc(sizeof(struct Set));
sptr->arrelement = 1;
return sptr;
}
SetArray Add(SetArray sptr, int x){
if(Is_Element_Of(x, sptr)){ //function to keep elements in set unique.
//Function works, which brings me to
//believe values are being stored
puts("Value already exists, enter a unique value");
}
else{
if(sptr == NULL){
puts("Memory Allocation Failed. Shutting down.");
exit(EXIT_FAILURE);
}
}
sptr = realloc(sptr, size*sizeof(struct Set)); //reallocate memory
//for the
//new element
sptr->arrvalue[sptr->arrelement] = x;
sptr->arrelement++;
size++;
return sptr;
}
SetArray Remove(SetArray sptr, int x){
if(sptr == NULL){
puts("Memory Allocation Failed. Shutting down.");
exit(EXIT_FAILURE);
}
else if(!Is_Element_Of(x, sptr)){
puts("Value is not in set");
}
else if(sptr->arrvalue == NULL){
puts("Set is empty. Cannot remove that which does not exist");
}
else{
sptr = realloc(sptr, size*sizeof(struct Set));
sptr->arrvalue[sptr->arrelement] = '\0';
sptr->arrelement--;
size--;
}
return sptr;
}
SetArray Clear(SetArray sptr){
if(sptr == NULL){
puts("Memory Allocation Failed. Shutting down.");
exit(EXIT_FAILURE);
}
int i;
for(i = 0; i < sptr->arrelement; i++){
sptr->arrvalue[i] = '\0';
}
return sptr;
}
Also, not sure if relevant, but just in case, here is the Function Is_Element_Of
int Is_Element_Of(int x, SetArray sptr){
if(sptr == NULL){
puts("Memory Allocation Failed. Shutting down.");
exit(EXIT_FAILURE);
}
int flag = 0;
int i;
for(i = 0; i < sptr->arrelement; i++){
if(sptr->arrvalue[i] == x){
flag = 1;
}
}
return flag;
}
Pardon me for any mistakes, but this is my first time asking and I tried my best to keep everything organized and structured properly.
Thank you for reading.

Answer 1

You are reallocating the wrong pointer you realloc the pointer to your parent Set when you want to realloc the array it contains.
sptr = realloc(sptr, size*sizeof(struct Set));
should be
sptr->arrvalue = realloc(sptr->arrvalue, (sptr->arrelement+1)*sizeof(int));

Answer 2

I guess your main problem is this :
sptr->arrvalue = malloc(sizeof(struct Set));
since arravlue is int*, try this :
sptr->arrvalue = malloc(sizeof(int));
edit: same for realloc