Dynamic array without new (C++)

Question

I'm new to C++ and this is a very basic question.

In C++ there are only two ways to create dynamic arrays (read in a book, correct me if I'm wrong) using memory allocation either by new operator or malloc() function which is taken from C.

When declaring an array int array[size], the square brackets [] must have a const.

However in the following code size is an unsigned int variable.

#include<iostream>

int main() {
    using namespace std;
    unsigned int size;
    cout<<"Enter size of the array : ";
    cin>>size;
    int array[size]; // Dynamically Allocating Memory
    cout<<"\nEnter the elements of the array\n";
    // Reading Elements
    for (int i = 0; i < size; i++) {
        cout<<" :";
        cin>>array[i];
    }
    // Displaying Elements
    cout<<"\nThere are total "<<size<<" elements, as listed below.";
    for (int j = 0; j < size; j++) {
        cout<<endl<<array[j];
    }
    return 0;
}

While compiling g++ throws no error and moreover the program runs perfectly.

Question 1 : Could this be another way to create dynamic array?

Question 2 : Is the code correct?

Question 3 : If [] can only contain const, why does the code work?

Answer 1

1. Correct, you have discovered a gcc extension. This has been allowed in C for a long time, but it has not made it into C++ standard until the C++14.
2. Yes, the code is correct, assuming that you are fine with using non-portable extensions to the language.
3. This is true about standard-compliant compilers. You can tell gcc that you do not want to use extensions by supplying a -std=c++98 or -std=c++11 compiler flag.

If you need a dynamically-sized array in C++, a better approach would be to use std::vector<T>. It gives you the flexibility of dynamically allocated array, and takes care of managing the allocated memory for you.