Uninitialized pointers are known as wild pointers because they point to some arbitrary memory location and may cause a program to crash or behave unexpectedly.
Example of Wild Pointers
In the below code, p is a wild pointer.
// C program that demonstrated wild pointers
int main()
{
/* wild pointer */
int* p;
/* Some unknown memory location is being corrupted.
This should never be done. */
*p = 12;
}
How can we avoid wild pointers?
If a pointer points to a known variable then it's not a wild pointer.
Example
In the below program, p is a wild pointer till this points to a.
int main()
{
int* p; /* wild pointer */
int a = 10;
/* p is not a wild pointer now*/
p = &a;
/* This is fine. Value of a is changed */
*p = 12;
}
If we want a pointer to a value (or set of values) without having a variable for the value, we should explicitly allocate memory and put the value in the allocated memory.
Example
int main()
{
int* p = (int*)malloc(sizeof(int));
// This is fine (assuming malloc doesn't return
// NULL)
*p = 12;
}
Note: int *ptr is wild because it points to some garbage memory by default, but int *ptr = NULL is not wild because it clearly points to nothing.