Segmentation Fault when variables are not-null but on `callq`

Question

Update on Question: Here is the SSCCE where I receive SIGSEV on str1_h[0][j] = bar1(str1_c[j]); . All variables are not-null which I checked using gdb:

#include <fstream>  //ifstream and ofilestream

using namespace std;

int bar1(int);
int bar2(int);
int bar3(int);

int main() {
    string str1 = "string";
    ifstream ifs;
    ifs.open("./file.txt");
    string line, str2;
    while (!ifs.eof()) {
        ifs >> line;
        str2 += line;
    }
    ifs.close();
    unsigned str2_l = str2.length();
    unsigned str1_l = str1.length();
    unsigned n = str2_l - str1_l + 1;   
    int str1_c[4];
    str1_c[0] = 0;
    str1_c[1] = 0;
    str1_c[2] = 0;
    str1_c[3] = 0;
    int x[3][4][n];
    int str1_h[3][4];       
    for (unsigned j = 0; j < 4; j++) {
        str1_h[0][j] = bar1(str1_c[j]);
        str1_h[1][j] = bar2(str1_c[j]);
        str1_h[2][j] = bar3(str1_c[j]);
        for (unsigned i = 0; i < n; i++) {
            x[0][j][i] = bar1(0);
            x[1][j][i] = bar2(0);
            x[2][j][i] = bar3(0);
        }
    }   
}
int bar1(int x) {
    return 0;
}
int bar2(int x) {
    return 0;
}
int bar3(int x) {
    return 0;
}

Answer 1

You cannot have a dynamic array on the stack in C++:

int x[3][4][n];

either use new , or use an STL container (eg std::vector ). See also How do I declare a 2d array in C++ using new?

Your array x is on the stack , thus writing to this array will likely overwrite important values on the stack (eg return pointers etc.)