custom_allocator.cpp

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

template<class T>
class MyAllocator : public std::allocator<T> {
public:
    MyAllocator() {}
    MyAllocator(const MyAllocator& x) {}

    template<class U>
    MyAllocator(const MyAllocator<U>& x) {}

    pointer allocate(size_type n) {
        std::cout << "allocate " << n * sizeof(T) << "bytes" << std::endl;
        return (pointer) std::malloc(n * sizeof(T));
    }

    void deallocate(pointer ptr, size_type n) {
        std::free(ptr);
    }

    template<class U>
    struct rebind {typedef MyAllocator<U> other;};
};