Segmentation Fault when Calling Functions

When I run the following code I get a segmentation fault.

Code:

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#include <iostream>
using namespace std;

typedef int* IntPointer;

void notsneaky(IntPointer temp);
void sneaky(IntPointer temp);
void sneakybutnotsneaky(IntPointer& temp);

int main()
{
IntPointer p;

        p = new int;
        *p = 77;
        cout<<"Before call to function *p == "
          << *p << endl;
   
   
      notsneaky(p);
   
      cout<<"After call to \"notsneaky\" function *p == "
          << *p << endl;
         
      sneaky(p);
   
      cout<<"After call to \"sneaky\" function *p == "
          << *p << endl;
         
      sneakybutnotsneaky(p);
   
      cout<<"After call to \"sneaky_but_notsneaky\" function *p == "
          << *p << endl;
       
        return 0;
}

void notsneaky(IntPointer temp)
{
      int *ptr;
      *ptr=23;
        temp = ptr;
        cout<<"Inside the function call *temp == "
            <<*temp<<endl;
}

void sneaky(IntPointer temp)
{
        *temp = 99;
        cout<<"Inside the function call *temp == "
            <<*temp<<endl;
}

void sneakybutnotsneaky(IntPointer& temp)
{
      int *ptr;
      *ptr=37;
        temp = ptr;
        cout<<"Inside the function call *temp == "
            <<*temp<<endl;
}

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Here is the output:

Code:

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thetinman@computer:~/code$ ./a.out
Before call to function *p == 77
Inside the function call *temp == 23
After call to "notsneaky" function *p == 77
Inside the function call *temp == 99
After call to "sneaky" function *p == 99
Segmentation fault

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Does anyonone know what is causing this segmentation fault? How should I go about fixing it?

Code:

---

void notsneaky(IntPointer temp)
{
      int *ptr;
      *ptr=23;

---

You are attempting to dereference an uninitialized pointer.