C++ std::string initialization using new operator function

Question

Have a basic snippet of initialization a std::string variable, and track the memory usage of program using overloaded new operator function as below:

static uint32_t s_AllocCount = 0;

// Overload of new operator.
void* operator new(size_t size) {

    s_AllocCount++;
    std::cout << "Allocating " << size << " bytes\n";

    return malloc(size);
}

Example-1: When initialized below in main:

int main()
{
    std::string name = "Hello World 1234";
    std::cout<<"No. of allocations="<<s_AllocCount<<std::endl;
    return 0;
}

Output

  Allocating 17 bytes
  No. of allocations=1

Example-2: When initialized below in main:

int main()
{
    std::string name = "Hello World";
    std::cout<<"No. of allocations="<<s_AllocCount<<std::endl;
    return 0;
}

Output

  No. of allocations=0

Query

Why the overloaded new operator is not called in the 2nd example where the length of the string is less than 16 bytes/characters. Where does the initialization of string memory happen in 2nd example.