Question

My main() crashes below when add(4) is called.

As I understand int* add, it should return a pointer to integer. Then, I should be able in main to say:

int * a = add(3);

to return a pointer to int.

Please explain what I’m doing wrong.

#include <cstdlib>
#include <iostream>

using namespace std;

int* add (int a) {
   int * c, d;
   d = a + 1;
   *c = d;
   cout << "c = " << c << endl; 
   return c;
}

int main(int argc, char *argv[])
{
    int a = 4;

    int * c;

    c = add(4); 

    system("PAUSE");
    return EXIT_SUCCESS;
}

Answer 1

In

 *c = d;

the pointer c is not initialized, so your program runs into undefined behavior. You could do something like the following instead:

void add( int what, int* toWhat )
{
    (*toWhat) += what;
}

and call it like this:

int initialValue = ...;
add( 4, &initialValue );