Segmentation fault when allocating and filling a matrix

Question

can you explain to me why i have a segmentation error?

#define M 5 

char ** test(int size) {
    char ** grid = malloc(size * sizeof(char)); 
    for (int row = 0; row < size ; row++) {
        grid[row] = malloc (size * sizeof(char)); 
    }

   for (int i = 0 ; i < size ; i++) {
       for (int j = 0 ; j < size ; j++) {
           grid[i][j] = 1; 
       }
   }
    return grid ; 
}

int main()
{
    char ** grid = test(M);  
}

Yet it seems correct to me...

char ** grid = malloc(size * sizeof(char)); should be a pointer to an array of pointers, not a pointer to an array of chars. sizeof(char) should be sizeof(char *) — nicomp, May 08 '21 at 11:28

score -1 · Answer 1 · answered May 08 '21 at 11:19

-1

you want

  char ** grid = (char**)malloc(size * sizeof(char*));

answered May 08 '21 at 11:19

Pierre

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Do not need the casting - can hide potential errors - see https://stackoverflow.com/questions/605845/do-i-cast-the-result-of-malloc – Ed Heal May 08 '21 at 11:23
@Bob__ You're right. I missed the char * in the parens. My bad. – nicomp May 08 '21 at 11:36
2

You do need to add some explanation. – nicomp May 08 '21 at 11:37

Segmentation fault when allocating and filling a matrix

1 Answers1