strange Segmentation fault (core dumped) on matrix - c

Question

So, I have this part of code:
for (lin = 0; lin < linhas_mat1; lin++)
{
fgets(linha_s, MAX_LINHA, matriz1_file);
buffer = strtok(linha_s, " ");
for (col = 0; col < colunas_mat1; col++)
{
printf ("\nCOLUNA: %d", col);
if (&matriz1[lin][col] == NULL)
printf ("erro");
matriz1[lin][col] = atoi(buffer);
buffer = strtok(NULL, " ");
}
}
It puts a matrix from a file into the memory. The open and the allocation didn't give errors (at least I think). What's strange is that the error seems to occur (discovered by printing the number of the current line) on the last 2 elements (before the last with the code above or the last element if I add some prints, that's even stranger) and only if the matrix has 5 lines or more. The previous lines are added into memory without problem, so I can't see why the last elements give problems. Someone has a clue what's the problem or some tips in how I can find the issue?

Answer 1

The code itself has no problem. The only possible reason I can see is, when the input file has less columns than you specified, it will cause a segmentatioin fault.
Here is full version of your code, I only added some initializations
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
int main() {
int lin, col, linhas_mat1, colunas_mat1;
char* buffer;
char linha_s[1023];
int matriz1[8][5];
linhas_mat1 = 8; colunas_mat1 = 5;
const int MAX_LINHA = 20;
FILE *matriz1_file = fopen("aa.txt", "r");
for (lin = 0; lin < linhas_mat1; lin++)
{
fgets(linha_s, MAX_LINHA, matriz1_file);
buffer = strtok(linha_s, " ");
for (col = 0; col < colunas_mat1; col++)
{
//printf ("\nCOLUNA: %d", col);
if (&matriz1[lin][col] == NULL)
printf ("erro");
matriz1[lin][col] = atoi(buffer);
printf("%d ", matriz1[lin][col]);
buffer = strtok(NULL, " ");
}
printf("\n");
}
}
If you give following file as input, the matrix will get all the values without any problem, unless you remove some column from it.
1 2 9 4 5
1 2 3 4 5
1 2 3 4 5
1 2 3 4 5
1 2 3 4 5
1 2 3 4 5
1 2 3 4 5
1 2 3 4 5