C Programming: malloc() inside another function

Question

I need help with malloc() inside another function.

I\'m passing a pointer and size to the fu

Answer 1

As mentioned in the other answers, we need a pointer to the pointer. But why?

We need to pass the value by a pointer in order to be able to modify the value. If you want to modify an int, you need to pass it by the int*.

In this question, the value we want to modify is a pointer int* (pointer changed from NULL to the address of the allocated memory), so we need to pass a pointer to the pointer int**.

By doing followed, pInt inside foo(int*) is a copy of the argument. When we allocate memory to the local variable, the one in the main() is intact.

void foo(int* pInt)
{
   pInt = malloc(...);
}
int main()
{
   int* pInt;
   foo(pInt);
   return 0;
}

So we need a pointer to pointer,

void foo(int** pInt)
{
   *pInt = malloc(...);
}
int main()
{
   int* pInt;
   foo(&pInt);
   return 0;
}