Are memory leaks possible with decltype(new any_type())?

Question

I am checking for any memory leaks possibility with class pointers using valgrind and found out that following program has no memory leaks :

#include <iostream>
#include <utility>
#include <memory>

using namespace std;

class base{};

int main()
{
  unique_ptr<base> b1 = make_unique<base>();
  base *b2 = new base();
  cout << is_same<decltype(new base()), decltype(b1)>::value << endl;
  cout << is_same<decltype(new base()), decltype(b2)>::value << endl;
  delete b2;
  return 0;
}

How can this be possible?

Answer 1

The operand of decltype (and also sizeof) is not evaluated, so any side-effects, including memory allocation, won't happen. Only the type is determined, at compile-time.

So the only memory allocations here are in make_unique and the first new base(). The former is deallocated by the unique_ptr destructor, the latter by delete b2, leaving no leaks.