segmentation fault (Core dumped) error on Dynamic array

Question

I am having this issue when trying to build my dynamic array, I think that there is mystake on realloc function or something, would appreciate if you can give me a hand on it. I am able to enter the names the first time but the issue start when Im doing it the second time

typedef struct {
      char nom[30], prenom[20];
      int age;

        } ITEM;

        void Lire(ITEM **items, int *nb_items)
        {
           int i = 0;

           printf("* Entrer les donnees et taper . pour terminer\n\n");

           for (i = 0; TRUE; i++) 
            {

                   ITEM *temp = (ITEM *) realloc(*items, ((i + 1) * sizeof(ITEM)));
                    if (temp == NULL)
                    {
                        free(*items);
                        printf("Il n'y a pas de memoire! \n");
                        exit (0);
                    }
                    *items = temp;
                    printf("> nom    : ");
                    scanf("%s", (*items[i]).nom);

                    if ((*items[i]).nom[0] == '.')
                    break;

                    printf("> prenom : ");
                    scanf("%s", (*items[i]).prenom);

            }
        }
int main(int argc, char *argv[])
{
   ITEM *items;
   int nb_items=0;
   items = (ITEM *) malloc(sizeof(ITEM));
   if(items == 0)
   {
       printf("Il n'y a pas de memoire! \n");
       exit (0);
   }
   Lire(&items, &nb_items);
   free (items);
   exit(0);
}

You tagged this question as C++. Why are you not using std::vector? — PaulMcKenzie
– PaulMcKenzie, Commented Oct 31, 2014 at 17:35
You can´t use realloc alone. malloc and free are there to use too. — deviantfan
– deviantfan, Commented Oct 31, 2014 at 17:35
thanks, I am using them in the main this is just a function to fill my array, should I use malloc and free here as well? — Daniel Chaparro
– Daniel Chaparro, Commented Oct 31, 2014 at 17:38
Are you typing a name that is too long? You are not protecting your strings from overrun. Try scanf("%29s", (*items[i]).nom); — Weather Vane
– Weather Vane, Commented Oct 31, 2014 at 18:06
Actually realloc can work just fine without malloc/free. If the initial value NULL, realloc works as malloc. If the requested size is 0, realloc works as free. — Valeri Atamaniouk
– Valeri Atamaniouk, Commented Oct 31, 2014 at 18:12

Valeri Atamaniouk · Accepted Answer · 2014-10-31 18:07:54Z

2

You problem is in operator precedence: *items[i] evaluates to items[i][0] and you want items[0][i], which is:

(*items)[i]

answered Oct 31, 2014 at 18:07

Valeri Atamaniouk

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Comments

sth · Accepted Answer · 2014-10-31 18:10:04Z

1

Array subscript access binds tighter than *. This causes *items[i] to be interpreted as *(items[i]), for example in this statement:

scanf("%s", (*items[i]).nom);

So items is accessed as if it would be an array of pointers to ITEM. In reality it is a pointer to an array of ITEM structs, and should be accessed like this:

scanf("%s", (*items)[i].nom);

answered Oct 31, 2014 at 18:10

sth

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Comments

pm100 · Accepted Answer · 2014-10-31 18:15:17Z

0

to make life easier i would do

            *items = temp;
            ITEM *current = &temp[i];
            printf("> nom    : ");
            scanf("%s", current->nom);
            ...etc

makes the code easier to read and simplifies the whole operator precedence isuuse

answered Oct 31, 2014 at 18:15

pm100

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1 Comment

Daniel Chaparro Over a year ago

actually this issue was solved today with your help, the names are being inserted into the array, the isse is reallocating memory I think as I am getting this segmentation Fault(Core dumped) when I need to enter the second block of info

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