如何使用placement new运算符创建对象数组？(How do I create array of objects using placement new operator?)

 如何使用placement new运算符创建对象数组？ 我知道如何从其他SO问题中为单个对象做这件事。 但我找不到对象数组。 
 
 要查看性能差异，我试图创建一个对象数组并在子循环后删除。 但我无法找到办法。 如何创建多个对象？ 
 
class Complex
{
  double r; // Real Part
  double c; // Complex Part

  public:
    Complex() : r(0), c(0) {}
    Complex (double a, double b): r (a), c (b) {}
    void *operator new( std::size_t size,void* buffer)
    {
        return buffer;
    }
};

char *buf  = new char[sizeof(Complex)*1000]; // pre-allocated buffer

int main(int argc, char* argv[])
{
  Complex* arr;
  for (int i = 0;i < 200000; i++) {
    //arr = new(buf) Complex(); This just create single object.
    for (int j = 0; j < 1000; j++) {
      //arr[j] = Now how do I assign values if only single obect is created?
    }
    arr->~Complex();
  }
return 0;
}

How do I create array of objects using placement new operator? I know how to do it for single object from other SO questions. But I couldn't find for array of objects.
 
To see the performance difference I am trying to create an array of objects and deleting after the subloop. But I am not able to find a way. How do I create multiple objects?
 
class Complex
{
  double r; // Real Part
  double c; // Complex Part

  public:
    Complex() : r(0), c(0) {}
    Complex (double a, double b): r (a), c (b) {}
    void *operator new( std::size_t size,void* buffer)
    {
        return buffer;
    }
};

char *buf  = new char[sizeof(Complex)*1000]; // pre-allocated buffer

int main(int argc, char* argv[])
{
  Complex* arr;
  for (int i = 0;i < 200000; i++) {
    //arr = new(buf) Complex(); This just create single object.
    for (int j = 0; j < 1000; j++) {
      //arr[j] = Now how do I assign values if only single obect is created?
    }
    arr->~Complex();
  }
return 0;
}

原文：https://stackoverflow.com/questions/42771709