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Create your own allocator

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The example is showing below.

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#include <iostream>
#include <memory>
#include <vector>

template <class T>
class TrackingAllocator{
    public:
        using value_type = T;
    
        using pointer = T *;
        using const_pointer = const T *;

        using void_pointer = void *;
        using const_void_pointer = const void*;

        using size_type = size_t;

        using difference_type = std::ptrdiff_t;

        TrackingAllocator() = default;
        ~TrackingAllocator() = default;

        size_type get_allocations() {
            return mAllocations;
        }

        pointer allocate(size_type num_objects) {
            return static_cast<pointer>(operator new(sizeof(value_type)*num_objects));
        }

        void deallocate(pointer p, size_type num_objects) {
            operator delete(p);
        }

        size_type max_size() const{
            return std::numeric_limits<size_type>::max();
        }
private:
    static size_type mAllocations;
};

template <class T>
typename TrackingAllocator<T>::size_type TrackingAllocator<T>::mAllocations = 0;

int main () {
    std::vector<int, TrackingAllocator<int> > v(5);
    return 0;
}