Question

Why can i do this?

int array[4]; // i assume this creates an array with 4 indexes

array[25]=1; // i have assigned an index larger than the int declaration

NSLog(@"result: %i", array[25]); // this prints "1" to the screen

Why does this work, if the index exceeds the declaration? what is the significance of the number in the declaration if it has no effect on what you can actually do with the array?

Thanks.

Answer 1

You are getting undefined behavior. It could print anything, it could crash, it could burst into singing (okay that isn’t likely but you get the idea).

If it happens to write to a location that is mapped with the adequate permissions it will work. Until one day when it won’t because of a different layout.