How does delete[] know the size of an array?

Question

I am curious how delete[] figures out the size of the allocated memory. When I do something like:

int* table = new int[5];
delete[] table;

Answer 1

How delete[] works is implementation-dependent, but the global new operator associates a descriptor with the allocated memory in some way (in most cases, it's prepended to the allocated memory, or stored in a lookup table). The descriptor contains the actual size of the memory that was allocated.

In your second code example, delete[] will correctly delete the nine-element array of int, and the original five-element array will be leaked.