Undefined behavior on deleting char array trought void *

Question

Is it true that the following yields undefined behavior:

void * something = NULL;
char * buffer = new char[10];

something = buffer;
buffer = NULL;

delete [] something; // undefined??

Do I first need to cast something to char * ?

Answer 1

Yes, strictly when you use delete[] the static type of the pointer that you delete[] must match the type of the array that you originally allocated or you get undefined behaviour.

Typically, in many implementations, delete[] called on a void* which is actually an array of a type that has no non-trivial destructor works, but it's not guaranteed.

delete[] buffer

or

delete[] (char*)something

would both be valid.