Write about the retrieval of n number of objects during the process of delete[]p? | C++

The n number of objects can be retrieved with the help of the pointer p (it stores the n number of objects) at the run time.
This can be achieved by the application of two techniques, which are:
1. An array which can be associated with p in the form of key and a value such as n.
2. Over-allocation of the array can be done.
The preceding techniques are used by the compilers of commercial grade.