I get this error "Unhandled exception at 0x009437bd in Hash functions.exe: 0xC0000005: Access violation reading location 0x00000001"

Question

I get this error over and over again when I run my project. Don't know where is the problem. I know it's about some free memory I used again, or a null pointer or access to a non exist memory but actually I checked all the pointers and they are declared as what they should to be.

Here's the code:

#include <iostream>
using namespace std ;

typedef struct ND {
  int ID;
  char* Name;
  char* Address;
  int Age;
  double GPA;
  ND * next;
} NODE;

class HF {
private :
  int count;
  int size ;
  int prime;
  int a ,b;
  NODE ** HT;
public: 
  HF ();
  HF ( int n , int p , int a, int b);
  ~ HF ();
  int findindex(int key);
  bool insert (int ID,char* Name,char* Address,int Age,double GPA);
  bool retrieve (int & ID,char* & Name,char* & Address,int & Age,double & GPA);
  bool remove(int key);
  double GetLoadFactor ();
};

HF :: HF ()
{
  size = 100;
  prime = 997;
  a = 23 ;
  b = 88;
  count =0;
  HT = new NODE* [size];
  for (int i=0; i< size ; i++)
      HT[i] = NULL;
  }

HF :: HF ( int n , int p , int a, int b)
{
  size = n;
  prime = p;
  a = a;
  b = b;
  count = 0;
  HT = new NODE* [size];
  for (int i=0; i< size ; i++)
      HT[i] = NULL;
}

HF :: ~ HF ()
{
  NODE *p;
  for (int i=0 ; i<size ; i++)
  {
      while (HT[i] != NULL)
      {
          p = HT[i];
          HT[i] = HT[i] -> next ;
              delete p;
      }
  }
  delete  [] HT ;
}

int HF :: findindex(int key)
{
  int index ;
  index = (((a*(key)+b) % prime) % size) ;
  index = index % size ;
  return index;
}

bool HF :: insert (int ID,char* Name,char* Address,int Age,double GPA)
{
  int i ;
  NODE * n;
  n = new NODE;
  n -> ID = ID;
  n -> Address = Address;
  n -> Name = Name;
  n -> Age = Age;
  n -> GPA = GPA;
  n -> next = NULL;
  i = findindex(ID);
  if ( HT[i] == NULL)
  {
      HT[i] = n;
  }
  else
  {
      n -> next = HT[i];
      HT[i] = n;
  }
  count ++ ;
  return true;
}

  bool HF ::retrieve (int & key,char* & Name,char * &Address,int & Age,double & GPA)
  {
  int i ;
  NODE *p;
  i = findindex(key);
  if ( HT[i] == NULL)
  {
      return false;
  }
  else
  {
      p = HT[i];
      if ( HT[i] -> ID == key)// here is the break point
      { 
          key = p-> ID ;
          Name = p-> Name ;
          Address = p-> Address ;
          Age = p-> Age;
          GPA = p-> GPA ;
          return true ; 
       }
       while ( p != NULL)
       {
          if ( p-> ID == key)
          { 
              key = p-> ID ;
              Name = p-> Name ;
              Address = p-> Address ;
              Age = p-> Age;
              GPA = p-> GPA ;
              return true ; 
          }
          else
              p = p-> next ;
          }
    }
    return false;
  }
bool HF :: remove (int key)
 {

int i ;
NODE *p1 , *p2;
i = findindex(key);
if ( HT[i] == NULL)
{
    return false;
}

else
{
    p1 =p2 = HT[i];
    if(HT[i] -> ID == key)
    {
        HT[i] = HT[i] -> next;
        delete p2;
        return true;
    }


    while ( p2 != NULL)
    {
        if ( p2 -> ID == key)
        { 
            p1 -> next = p2 -> next ;
            delete p2;

            count --;
            return true;
        }
        else 
        {

            p1 =p2;
            p2 = p2 -> next;

        }
    }


}
return false;

 }

 double HF :: GetLoadFactor()
 {
double L;

L = (double) count/size ;
return L;
}

int main ()
{
double L;
int x,age;
char * name , *address;
double GPA;
HF UHashFunc1;
HF UHashFunc2( 11 , 7 , 3 , 0);

 UHashFunc1.insert( 6 , "Ahmed" , "Jenin" , 20 , 3.5);
 UHashFunc1.insert( 1 , "Sarah" , "Jenin" , 18 , 3.2);
 UHashFunc1.insert(40 , "Mohammad" , "Tolkrem", 19 , 3.0);
 UHashFunc1.insert(2 , "Ala'a" , "Jerusalem", 19 , 2.6);
 UHashFunc1.insert(41 , "Raghad" , "Tolkrem", 19 , 1.6);
 UHashFunc1.insert(80 , "Mohammad" , "Jenin", 22 , 2.7);
 UHashFunc1.insert(83 , "Murad" , "Nablus", 18 , 3.7);
 UHashFunc1.insert(44 , "Reem" , "Hebron", 19 , 2.9);
 UHashFunc1.insert(50 , "Wajde" , "Qalqelya", 20, 1.7);
 UHashFunc1.insert(42 , "Belal" , "Hebron", 20 , 3.4);
 UHashFunc1.insert(3 , "Ahmed" , "Nablus", 21 , 1.9);
 UHashFunc1.insert(84 , "Haitham" , "Nablus", 21 , 3.1);


cout <<"enter the ID you want to retrieve"<<endl;
cin>>x;
if(UHashFunc1.retrieve(x,name,address,age,GPA))
{
cout << "ID:"<<x<<endl;
cout << "Name:"<<name<<endl;
cout << "Address:"<<address<<endl;
cout << "Age:"<<age<<endl;
cout << "GPA:"<<GPA<<endl;
}
else
    cout<<"NOT FOUND"<<endl;

cout <<"enter the ID you want to retrieve"<<endl;
cin>>x;
if(UHashFunc1.retrieve(x,name,address,age,GPA))
{
cout << "ID:"<<x<<endl;
cout << "Name:"<<name<<endl;
cout << "Address:"<<address<<endl;
cout << "Age:"<<age<<endl;
cout << "GPA:"<<GPA<<endl;
}
else
    cout<<"NOT FOUND"<<endl;
L=UHashFunc1.GetLoadFactor();
cout << "The current load factor is : " << L <<endl;
UHashFunc1.remove(42);
L=UHashFunc1.GetLoadFactor();
cout << "The current load factor is : " << L <<endl;
x=84;
UHashFunc1.retrieve(x,name,address,age,GPA);
cout << "ID:"<<x<<endl;
cout << "Name:"<<name<<endl;
cout << "Address:"<<address<<endl;
cout << "Age:"<<age<<endl;
cout << "GPA:"<<GPA<<endl;
x=1;
UHashFunc1.retrieve(x,name,address,age,GPA);
cout << "ID:"<<x<<endl;
cout << "Name:"<<name<<endl;
cout << "Address:"<<address<<endl;
cout << "Age:"<<age<<endl;
cout << "GPA:"<<GPA<<endl;
x=50;
UHashFunc1.retrieve(x,name,address,age,GPA);
cout << "ID:"<<x<<endl;
cout << "Name:"<<name<<endl;
cout << "Address:"<<address<<endl;
cout << "Age:"<<age<<endl;
cout << "GPA:"<<GPA<<endl;

cout << "Enter The ID you want to remove"<<endl;
cin>>x;
if(UHashFunc1.remove(x))
    {
    L=UHashFunc1.GetLoadFactor();
     cout << "The current load factor after removing a record is : " << L <<endl;
}
else 
{ cout << "NOT Exist"<<endl;}

if(UHashFunc1.remove(2))
    {
    L=UHashFunc1.GetLoadFactor();
     cout << "The current load factor after removing a record is : " << L <<endl;
}
else 
{ cout << "NOT Exist"<<endl;}
 UHashFunc1.insert( 45 , "Amjad" , "Nablus" , 19 , 2.0);
 L=UHashFunc1.GetLoadFactor();
 cout << "The current load factor after adding a record is : " << L <<endl;
 if(UHashFunc1.remove(80))
    {
    L=UHashFunc1.GetLoadFactor();
     cout << "The current load factor after removing the record is : " << L <<endl;
}
else 
{ cout << "NOT Exist"<<endl;}
 if(UHashFunc1.remove(50))
    {
    L=UHashFunc1.GetLoadFactor();
     cout << "The current load factor after removing the record is : " << L <<endl;
}
else 
{ cout << "NOT Exist"<<endl;}

  UHashFunc2.insert( 5 , "Ahmed" , "Jenin" , 20 , 3.5);
 UHashFunc2.insert( 1 , "Sarah" , "Jenin" , 18 , 3.2);
 UHashFunc2.insert(9 , "Mohammad" , "Tolkrem", 19 , 3.0);
 UHashFunc2.insert(2 , "Ala'a" , "Jerusalem", 19 , 2.6);
 UHashFunc2.insert(8 , "Raghad" , "Tolkrem", 19 , 1.6);
 UHashFunc2.insert(100 , "Mohammad" , "Jenin", 22 , 2.7);
 UHashFunc2.insert(50 , "Murad" , "Nablus", 18 , 3.7);
 UHashFunc2.insert(23 , "Reem" , "Hebron", 19 , 2.9);
 UHashFunc2.insert(40 , "Wajde" , "Qalqelya", 20, 1.7);
 UHashFunc2.insert(17 , "Belal" , "Hebron", 20 , 3.4);
 UHashFunc2.insert(3 , "Ahmed" , "Nablus", 21 , 1.9);
 UHashFunc2.insert(7 , "Haitham" , "Nablus", 21 , 3.1);

 cout <<"enter the ID you want to retrieve from the 2nd Func"<<endl;
cin>>x;
if(UHashFunc2.retrieve(x,name,address,age,GPA))
{
cout << "ID:"<<x<<endl;
cout << "Name:"<<name<<endl;
cout << "Address:"<<address<<endl;
cout << "Age:"<<age<<endl;
cout << "GPA:"<<GPA<<endl;
}
else
    cout<<"NOT FOUND"<<endl;

cout <<"enter the ID you want to retrieve from the 2nd Func"<<endl;
cin>>x;
if(UHashFunc2.retrieve(x,name,address,age,GPA))
{
cout << "ID:"<<x<<endl;
cout << "Name:"<<name<<endl;
cout << "Address:"<<address<<endl;
cout << "Age:"<<age<<endl;
cout << "GPA:"<<GPA<<endl;
}
else
    cout<<"NOT FOUND"<<endl;

L=UHashFunc2.GetLoadFactor();
cout << "The current load factor is : " << L <<endl;
UHashFunc2.remove(2);
L=UHashFunc2.GetLoadFactor();
cout << "The current load factor is : " << L <<endl;
x=5;
UHashFunc2.retrieve(x,name,address,age,GPA);
cout << "ID:"<<x<<endl;
cout << "Name:"<<name<<endl;
cout << "Address:"<<address<<endl;
cout << "Age:"<<age<<endl;
cout << "GPA:"<<GPA<<endl;
x=1;
UHashFunc2.retrieve(x,name,address,age,GPA);
cout << "ID:"<<x<<endl;
cout << "Name:"<<name<<endl;
cout << "Address:"<<address<<endl;
cout << "Age:"<<age<<endl;
cout << "GPA:"<<GPA<<endl;
x=50;
UHashFunc2.retrieve(x,name,address,age,GPA);
cout << "ID:"<<x<<endl;
cout << "Name:"<<name<<endl;
cout << "Address:"<<address<<endl;
cout << "Age:"<<age<<endl;
cout << "GPA:"<<GPA<<endl;

cout << "Enter The ID you want to remove from the 2nd Func"<<endl;
cin>>x;
if(UHashFunc2.remove(x))
    {
    L=UHashFunc2.GetLoadFactor();
     cout << "The current load factor after removing a record is : " << L <<endl;
}
else 
{ cout << "NOT Exist"<<endl;}

if(UHashFunc2.remove(2))
    {
    L=UHashFunc2.GetLoadFactor();
     cout << "The current load factor after removing a record is : " << L <<endl;
}
else 
{ cout << "NOT Exist"<<endl;}
 UHashFunc2.insert( 45 , "Amjad" , "Nablus" , 19 , 2.0);
 L=UHashFunc2.GetLoadFactor();
 cout << "The current load factor after adding a record is : " << L <<endl;
 if(UHashFunc2.remove(100))
    {
    L=UHashFunc2.GetLoadFactor();
     cout << "The current load factor after removing the record is : " << L <<endl;
}
else 
{ cout << "NOT Exist"<<endl;}
 if(UHashFunc2.remove(9))
    {
    L=UHashFunc2.GetLoadFactor();
     cout << "The current load factor after removing the record is : " << L <<endl;
}
else 
{ cout << "NOT Exist"<<endl;}


cin>>x;



return 0;
 }

There are no building errors just these ones when break point

First-chance exception at 0x009437bd in Hash functions.exe: 0xC0000005: Access violation reading location 0x00000001. Unhandled exception at 0x009437bd in Hash functions.exe: 0xC0000005: Access violation reading location 0x00000001. First-chance exception at 0x009437bd in Hash functions.exe: 0xC0000005: Access violation reading location 0x00000001. The thread 'Win32 Thread' (0x1e40) has exited with code -1073741510 (0xc000013a). The program '[788] Hash functions.exe: Native' has exited with code -1073741510 (0xc000013a).

Answer 1

I was able to easily reproduce the error you ran into. You have a constructor for HF that takes parameters like this:

HF :: HF ( int n , int p , int a, int b)
{
    size = n;
    prime = p;
    a = a;
    b = b;

As you can see the parameter names a and b are exactly the same as the member variable names. Hence HF::a and HF::b are never assigned values. Hence they are always uninitialized and contain garbage. Hence you get nothing but random values, and all the hashing stuff you are trying to do doesn't work as a result.

You should change the parameter names to something different. Say with capital letters perhaps:

HF :: HF ( int n , int p , int A, int B)
{
    size = n;
    prime = p;
    a = A;
    b = B;

Once I do that, it solves all the memory corruption errors, and it runs to completion just fine.

Answer 2

Learn to use, and then apply, std::vector<T>, std::string, std::shared_ptr<T>, std::unique_ptr<T>. Then come back if problem persists.

Answer 3

This is most certainly a NULL pointer. You are accessing memory location 1 (0x00000001), which is 1 byte offset from NULL (aka 0x00000000). The code you posted is verbose and a bit of a mess, and without a line number where you are accessing the pointer, it's hard to say where exactly you are accessing a NULL pointer.