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#include <cassert>
#include <cstddef>

#if __clang__ || __GNUG__
  const size_t overhead = sizeof(size_t);
#else
  const size_t overhead = 2 * sizeof(size_t);
#endif

struct S {
  void *p;
  S ();
  ~S ();
};

void* operator new[] (size_t n, void *p, size_t bufsize) {
  assert (n <= bufsize);   // alternatively, throw an exception
  return p;
}

void f() {
  const size_t n = 32;
  alignas(S) unsigned char buffer[sizeof(S) * n + overhead];
  S *sp = new (buffer, sizeof buffer) S[n];
 
  // ...
  // Destroy elements of the array.
  for (size_t i = 0; i != n; ++i) {
    sp[i].~S ();
  }
}