CODEWITHSUNDEEP
c++segmentation-fault
cod3min3
cod3min3

Reputation: 625

Segmentation fault occurs when trying to read in a second multidimensional array

I have started to learn c++ and I am having a problem already.My program will take 4 arguments from the command-line. These arguments will be the dimensions of two multidimensional arrays. ./myprogram 2 2 2 2

This is how I enter the elements for the first 2x2 array:

1 2 3 4

Then I enter the elements for the second array: 5

Then I get an error in the terminal stating Segmentation fault (core dumped)

Here is the code that reads from the command line and tires to read in the array elements:

#include <iostream>
#include <stdlib.h>


using namespace std;

void readArr(int, int, double**);

int main(int argc, char* argv[]) {

    int aRowCount = atoi(argv[1]);
    int aColCount = atoi(argv[2]);

    int bRowCount = atoi(argv[3]);
    int bColCount = atoi(argv[4]);

    std::cout << "Input accepted" << endl;

    if(aColCount != bRowCount) {
        std::cerr << "Col. Count of the first must match Row. Count of the second matrix." << endl;

        return 1;
    }

    double **A = new double*[aRowCount];
    for(int i = 0; i < aRowCount; i++){
        A[i] = new double(aColCount);
    }

    std::cout << "allocating A" << endl; 


    double **B = new double*[bRowCount];
    for(int j = 0; j < bRowCount; j++){
        A[j] = new double(bColCount);
    }

    std::cout << "allocating B" << endl;

    double **C = new double*[aRowCount];
    for(int k = 0; k < aRowCount; k++) {
        C[k] = new double(bColCount);
    }


    std::cout << "Reading in A" << endl;
    readArr(aRowCount, aColCount, A);

    std::cout << "Reading in B" << endl;
    readArr(bRowCount, bColCount, B);

    return 0;
}

void readArr(int rowCount, int colCount, double **array) {
    for(int i = 0; i < rowCount; i++) {
        for(int j = 0; j < colCount; j++) {
            std::cin >> array[i][j];
        }
    }
}

Upvotes: 1

Views: 94

Answers (1)

user2100815
user2100815

Reputation:

This:

    A[i] = new double(aColCount);

should be:

    A[i] = new double[aColCount];

and similar elsewhere. Your code allocates a single double, and initialises it with the value of aColCount.

Upvotes: 1

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