删除ptr vs delete [] ptr

Question

  

可能重复：
  Is delete[] equal to delete?

int main()
{
    char *ptr = new char[10];

    delete ptr;  // or delete [] ptr;
}

delete []用于数组，delete用于单个对象，对吧？因此，在上面的代码中它应该是delete [] ptr;，但似乎delete ptr;也可以。不可思议？

此外，

int main()
{
    int x;
    cin >> x;
    char *ptr = new char[x];  //cannot make sure whether it is a char pointer or a pointer to an array, right?
    // delete ptr, or delete [] ptr;
}