need help finding why SIGABRT occured

[Ruthra]

#include <iostream>
#include <fstream>
using namespace std;

class matrix{
    char **b=NULL;
    int n;

public:

    matrix(int sz):n{sz}{
        b = new char*[n];
        for(int i=0;i<n;++i) b[i] = new char[n];
    }


    void Set(int x,int y,char c){
        b[x][y] = c;
    }

    char Get(int x,int y){
        return b[x][y];
    }

    void Print(){
        for(int i=0;i<n;++i){
            for(int j=0;j<n;++j){
                cout<<b[i][j];
            }
            cout<<endl;
        }
    }

    int Size(){ return n; }

    bool operator==(matrix y){
        for(int i=0;i<n;++i){
            for(int j=0;j<n;++j){
                if(b[i][j] != y.Get(i,j)) return false;
            }
        }
        return true;
    }

    ~matrix(){
        for(int i=0;i<n;++i) delete[] b[i];
    }
};

matrix Rotate(matrix m){
    int S = m.Size();
    matrix x(S);
    int i,j;
    for(i=0;i<S;++i){
        for(j=0;j<S;++j){
            x.Set(j,(S-1-i),m.Get(i,j));
        }
    }

    return x;
}

In the above code when comparing two matrices after recursive passing through Rotate function like this

Rotate(Rotate(Rotate(matA)))

causes a SIGABRT error.

If there are two Recursive calls like

Rotate(Rotate(matA))

there are no errors.
i couldn't find where the error occurs. Can someone tell why more Recursive call causes this error

[Peter87]

You have not defined a copy constructor.