Matrix transposed with pointer-to-pointer in c++

Question

I am trying to transpose a matrix with pointer-to-pointer in c++ but there is an error: "segmentation fault ('core' dumped)". I tried to find the error on forums and figured out that in matrixTrans function, the 'puntero_trans = new int *[nCol];' line and the for loop next to it, I had to move to getData function. I really do not know why this happens. Thanks for your time. My code below:

#include <iostream>

void getData();
void matrixTrans(int **, int **,int, int);
void showData(int **, int, int);

//Global variables
int **puntero_matrix = nullptr, **puntero_trans;
int nRaws, nCol;

int main() {

    getData();
    matrixTrans(puntero_matrix,puntero_trans,nRaws,nCol);
    showData(puntero_trans, nRaws,nCol);

    //Flushing memory...
    for (int i = 0; i < nRaws; ++i) {
        delete[] puntero_matrix[i];
    }
    for (int i = 0; i < nCol; ++i) {
        delete[] puntero_trans[i];
    }

    delete[] puntero_matrix;
    delete[] puntero_trans;


    std::cin.get();
    return 0;
}

void getData() {
    std::cout << "Please enter the number of raws:"; std::cin >> nRaws;
    std::cout << "Please enter the number of columns: "; std::cin >> nCol;

    puntero_matrix = new int* [nRaws];
    for (int i = 0; i < nRaws; ++i) {
        puntero_matrix[i] = new int[nCol];
    }

    for (int i = 0; i < nRaws; ++i) {
        for (int j = 0; j < nCol; ++j) {
            std::cout << "Please enter value for [" << i << "][" << j << "]: "; std::cin >> *(*(puntero_matrix + i) + j);
        }
    }
}

void matrixTrans(int **puntero_matrix, int **puntero_trans, int nRaws, int nCol) {

    puntero_trans = new int *[nCol];
    for (int i = 0 ; i < nCol; ++i) {
        puntero_trans[i] = new int[nRaws];
    }

    for (int i = 0; i < nRaws; ++i) {
        for (int j = 0; j < nCol; ++j) {
            *(*(puntero_trans + j) + i) = *(*(puntero_matrix + i) + j);
        }
    }
}

void showData(int **puntero_trans,int nRaws,int nCol) {
    for (int i = 0; i < nCol; ++i) {
        for (int j = 0; j < nRaws; ++j) {
            std::cout << *(*(puntero_trans + i) + j) << " ";
        }
        std::cout << std::endl;
    }
}

Use a *debugger* to catch the crash in action, and to locate when and where in your code it happens. It will also allow you to examine variables and their values at the time of the crash. — Some programmer dude, May 18 '21 at 05:32
Also, for any pointer (or array) `p` and index `i`, the expression `*(p + i)` is *exactly* equal to `p[i]`. Using array-indexing is easier to read and understand, as well as less to write. And once you've made the code clearer, stop using pointers and explicit memory handling, and use `std::vector` instead. — Some programmer dude, May 18 '21 at 05:34
And if you need to use pointers instead of vector due to some external requirement, you can try compiling with address sanitizer on (`-fsanitize=address` on most contemporary versions of gcc and clang), it is very likely to help you solve the problem fast. — alagner, May 18 '21 at 08:47

Matrix transposed with pointer-to-pointer in c++

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