Question

I am learning how to use dynamic arrays in C. What I want to do is to create a dynamic array data, and put “1” into the first entry using the function test().

void test(void)
{

data[0] = 1;

}


int main(void)
{

int *data = malloc(4 * sizeof *data);

test();

return 0;
}

This compiles in Visual Studio 2010 but the program crashes when run. Instead of using test(), using data[0] = 1 works.

My (newbie) guess is that I need to pass a pointer to data to function test(). How should I write this?

Attempt

void test(int *data)
{

data[0] = 1;

}

Then, in main use test(data) instead of just test().

Edit

The attempt works. However, is this a “proper” way of doing it?

Answer 1

You can pass arrays dynamically in two ways :

• Using a simple pointer and then using pointer arithmetic to manipulate

void test (int * data, int i)
{
    *(data + i) = 1; //This sets data[i] = 1
}

• Or this way :

void test(int data[], int i)
{
    data[i] = 1; //This is the more familiar notation
}

---

Either of these ways is the ‘proper’ way to go about this.