The following code example is taken from the book
C++17 - The Complete Guide by Nicolai M. Josuttis, Leanpub, 2017
The code is licensed under a Creative Commons Attribution 4.0 International License. Creative Commons License

// raw code

#include <cstddef>   // for std::size_t
#include <cstdlib>   // for std::malloc()
#include <cstdio>    // for std::printf()

void* operator new (std::size_t size)
  std::printf("::new called with size: %zu\n", size);
  return ::std::malloc(size);

int main()
  struct alignas(64) S {
    int i;

  S* p = new S;  // calls our operator new only before C++17