Array dimension in c++ 11 [duplicate]

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• C++ declare an array based on a non-constant variable? 3 answers

I have studied in C++ Primer that the dimension of an array should be a const expression but the following code compiles and gives the desired result. Why?

#include<iostream>
using namespace std;
int main()
{
unsigned int bufsize = 10;
int h[bufsize]={};
for(int i=0; i<=9; i++)
    cout<<h[i]<<endl;
}

But if I add the following:

constexpr int a = bufsize;

Then the compiler shows error meaning that bufsize is not a constant expression then why is the program compiling correctly otherwise if the dimension of the array should be constant expression