#include <iostream>
#include <cstdint>
#include <cstddef>
using std::size_t;
 
struct head_t { size_t size; int data[]; };
 
int* make_intarray(size_t const size) {
	head_t* h = static_cast<head_t*>(::operator new(sizeof(head_t) + size * sizeof(int)));
	h->size = size;
	return h->data;
}
 
void unmake_intarray(int* array) {
	::operator delete(static_cast<void*>(array) - offsetof(head_t, data));
}
 
size_t get_intarray_size(int const*const begin) {
	return static_cast<head_t const*>(static_cast<void const*>(begin) - offsetof(head_t, data))->size;
}
 
int main() {
	int* my_10_ints = make_intarray(10);
	// Oh noez! I forgot 10!
	size_t what_was_10_again = get_intarray_size(my_10_ints);
	::std::cout << what_was_10_again << "\n";
	unmake_intarray(my_10_ints);
}

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