array_initialization.cpp

#include <iostream>

const int LENGTH = 8;

template<typename T>
void
output_array(T *p)
{
   for (int i = 0; i < LENGTH; ++i)
   {
      std::cout << *(p + i);
   }
   std::cout << "\n";
}

int TEST_CTOR_CALL =  0;

struct pod_test {
   int data;
};

struct test {

   operator char() const { return 'X'; }

   test() { ++TEST_CTOR_CALL; }

   test(int) {}
   
};

int main()
{
   std::cout << "Omitting initializer results in uninitialized PODs\n";
   
   char a0[LENGTH];
   output_array<char>(a0);
   
   pod_test a1[LENGTH]; 
   std::cout << a1->data << (a1 + 1)->data << "...\n";
   
   std::cout << "Leaving initializer empty initializes PODs to 0\n";
   
   char a2[LENGTH] = {};
   output_array<char>(a2);
   
   int a3[LENGTH] = {};
   output_array<int>(a3);

   pod_test a4[LENGTH] = {}; 
   std::cout << a4->data << (a4 + 1)->data << "...\n";

   std::cout << "Omitting initializer cause default constructor of non-POD types to be called\n";
   
   test a5[LENGTH];
   output_array<test>(a5);

   test a6[LENGTH] = { 5, };
   output_array<test>(a6);
   
   std::cout << "(test default constructor called: " << TEST_CTOR_CALL << ")\n";

   std::cout << "Finally, using new\n";

   char *a7 = new char[8];
   output_array<char>(a7);
   
}