It took me some serious thinking to figure out why you could take t, despite t being NULL. If I managed to understand it correctly, it is because t is an array

It took me some serious thinking to figure out why you could take t, despite t being NULL. If I managed to understand it correctly, it is because t is an array, and arrays are special. t is a pointer to an array, i.e. it points to the first element of the array. t is an array, which means it behaves like a pointer to the first element. The remarkable consequence of this is that t and t have the same numerical value, but different types. t==t evaluates to true.