Segmentation fault 11: while trying to input B[1] using cin

Question

I'm having a problem in running the following code. It is giving me a segmentation fault as a runtime error.

#include <iostream>
using namespace std;

int main()
{
    int n;
    cout << "Enter n: ";
    cin >> n;

    float A[n][n], x[n], B[n], L[n][n], U[n][n], m[n][n], Aug[n][n + 1];

    //Initializing matrix A,L,U
    cout << "Enter A: \n";
    for (int i = 0; i < n; i++) {
        for (int j = 0; j < n; j++) {
            cin >> A[i][j];
            U[i][j] = A[i][j];
            Aug[i][j] = A[i][j];
            if (i == j) {
                L[i][j] = 1;
            }
            else {
                L[i][j] = 0;
            }
        }
    }

    //Initialising matrix B
    cout << "Enter B: \n";
    for (int i = 0; i < n; i++) {
        cin >> B[i];
        cout << "done" << i;
        Aug[i][n] = B[i];
    }

    // ...

    return 0;
}

Input:

n=2, A={2,5,-3,-4}, B={0,0}

The error occurs when I try to input B[1] so done0 gets printed however done1 doesn't. I just can't figure out what the reason of this error is as I don't see any reason for B[1] to be inaccessible.

Answer 1

You've misdiagnosed the problem. The segmentation fault occurs after the for loop finishes, in the code you haven't shown us (the // ... part). The done1 doesn't get printed because your code faults before it has a chance to flush the output buffer. Your cout << "done" << i; just puts things in the output buffer, there's nothing there to flush the buffer.