Initializing a pointer in a separate function in C

Question

I need to do a simple thing, which I used to do many times in Java, but I\'m stuck in C (pure C, not C++). The situation looks like this:

int *a;

void initA         


        

Answer 1

You are assigning arr by-value inside initArray, so any change to the value of arr will be invisible to the outside world. You need to pass arr by pointer:

void initArray(int** arr) {
  // perform null-check, etc.
  *arr = malloc(SIZE*sizeof(int));
}
...
initArray(&a);

Answer 2

You need to adjust the *a pointer, this means you need to pass a pointer to the *a. You do that like this:

int *a;

void initArray( int **arr )
{
    *arr = malloc( sizeof( int )  * SIZE );
}

int main()
{
    initArray( &a );
    return 0;
}