用operator new实现new

int main()
{
    //Test1* p1 = (Test1*)malloc(sizeof(Test1));
    //new(p1) Test1(10);

    // new -> 分配+调用构造函数初始化

    // malloc/operator new -> 分配内存
    // new 定位表达式 ->显示调用构造函数初始化

    //Test1* array1 = new Test1[10];

    //delete[] array1;

    // 模拟new[]
    Test1* array2 = (Test1*)operator new(sizeof(Test1)*10 + 4);
    *((int*)array2) = 10;
    array2 = (Test1*)((int)array2 + 4);
    for (int i = 0; i < 10; ++i)
    {
        new(array2 + i) Test1(20);
    }

    // 模拟delete[]
    // 先调析构函数，再释放空间
    int count = *((int*)array2 - 1);
    for (int i = 0; i < count; ++i)
    {
        array2[i].~Test1();
    }
    array2 = (Test1*)((int)array2 - 4);
    operator delete(array2);

    return 0;
}