Hex converts to wrong decimal - arrays

Question

I am trying to read/write hexadecimals into a 2D integer array for my program, but there are issues with some hexadecimals.
When I input 272cf50 it accurately turns into 41078608 in the array and I have no problems.
But when I input ffff0000000 it turns into -268435456 instead of its decimal equivalent: 17591917608960.
Because of this when I try to check if ffff0000000 already exists in the array it says it doesn't even though I wrote it into the array. I am confused about why this is happening and how I can fix it.
This is the code:
bool inCache(unsigned long addy, unsigned long blockid, unsigned long setidx, int size, int** cache, int lps){
//find set index
//find easier way
int i=0;
while(cache[i][0]!=setidx){
i++;
}
//check if set contains blockid
for(int j=0; j<lps; j++){
if(cache[i+j][2]==1 && cache[i+j][1]==blockid){
return true;
}
}
//not in cache
return false;
}
void read(unsigned long addy, unsigned long blockid, unsigned long setidx, int size, int** cache, int lps){
unsigned long x = blockid;
bool e = inCache(addy,blockid,setidx,size,cache,lps);
if(e==true){
ch++;
}else{
cm++;
mr++;
//set x in cache
newWrite(addy,x,setidx,size,cache,lps);
}
}
void newWrite(unsigned long addy, unsigned long blockid, unsigned long setidx, int size, int** cache, int lps){
//check if already loaded in cache
bool e = inCache(addy,blockid,setidx,size,cache,lps);
if(e!=true){
//load the block into chosen cache line
//find the setidx
int i=0;
while(cache[i][0]!=setidx){
i++;
}
//go thru set and put into first available cacheline
for(int j=0; j<lps; j++){
if(cache[i+j][2]==0){
cache[i+j][2]=1;
cache[i+j][1]=blockid;
break;
}
}
//if all cachelines are full, put into least recent cacheline
cache[i][1]=blockid;
}
}
This is the specific example:
0x1: R 0xffff0000000
0x2: R 0xffff0000000
In my particular example, for the first line the read function gets called and since the value is not in the array(cache) it calls the newWrite funciton to add it to the array. When it is added to the cache is when it converts to -268435456. Then, for the second line when the read function checks if the value is in the array it returns false instead of true.

Answer 1

This is a prime example of an integer overflow. Precisely what happened, was that the inputted number was interpreted as two’s complement. The number was so long that the sign bit got flipped. Indeed,
0xFFFF0000000 - 2⁴⁴ = -268435456
which is where that mysterious number came from.
Surely the best way to manage this situation is to keep care that the variables used can hold numbers that big, or to reject too large values.
EDIT with more information
The code shows that the array’s signature is int **. This should be unsigned too in order to make the comparison to work. The following code demonstrates the problem:
#include <stdio.h>
int main(void)
{
int a = 0xffff0000000;
unsigned long b = 0xffff0000000;
printf("%d\n",a==b);
/* the number zero (meaning "false") is printed */
}