C++ Primer Plus

Pointer Danger

Danger awaits those who incautiously use pointers. One extremely important point is that when you create a pointer in C++, the computer allocates memory to hold an address, but it does not allocate memory to hold the data to which the address points. Creating space for the data involves a separate step. Omitting that step, as in the following, is an invitation to disaster:

long * fellow;          // create a pointer-to-long*fellow = 223323;       // place a value in never-never land

Sure, fellow is a pointer. But where does it point? The code failed to assign an address to fellow. So where is the value 223323 placed? We can’t say. Because fellow wasn’t initialized, it could have any value. Whatever that value is, the program interprets ...