CODEWITHSUNDEEP
clisthashtable
Foushi
Foushi

Reputation: 375

Using For to create struct to initialize

Hi I have a problem I'm trying to initialize an hashtable with an array that contains list but when I'm using a for loop, all the data are "shared". I've to initialize mannualy like that :

   struct objec_listt A,B; // Initialization of 2 two structure A and B
   INIT_LIST_HEAD(&A.list); // A is headlist
   INIT_LIST_HEAD(&B.list); // B is headlist
   hashtable->tab[0]= &A; // I insert A into the array
   hashtable->tab[1]= &B; // I insert B into the array

   insert(1,tab[0]); //  insert 1, not real syntax 
   insert(2,tab[0]); //  insert 2
   insert(3,tab[1]); //  insert 3

Now I print tab[0] and tab[1] with my own function and I get

tab[0] = 1,2

tab[2]= 3

Ok it works as I want

If I do like that It doesnt work :

   for(i=0; i<2; i++)
   {
     struct objec_listt A;
     INIT_LIST_HEAD(&A.list);
     hashtable->tab[i] = &A
   }

   insert(1,tab[0]); //  insert 1,
   insert(2,tab[0]); //  insert 2
   insert(3,tab[1]); //  insert 3

If I do a printf :

tab[0] : 1,2,3

tab[1] : 1,2,3

So the problem is like I'm trying to create "many object" that will be head of list, and for each I need to initialize an array with a size of 100, so that why I'm looking to do with loop

Thanks !

Upvotes: 0

Views: 46

Answers (1)

David C. Rankin
David C. Rankin

Reputation: 84579

Continuing from the comment, in other words, you would need something similar to the following to avoid the declaration within the for loop code block:

struct objec_listt A[2];

for(i=0; i<2; i++)
{
    INIT_LIST_HEAD(&A[i].list);
    hashtable->tab[i] = &A[i];
}

insert(1,tab[0]); //  insert 1,
insert(2,tab[0]); //  insert 2
insert(3,tab[1]); //  insert 3

In your example, when you declare struct objec_listt A within the for loop block, A has a lifetime only within the block between the {}. When the for loop exits, the memory of A is marked as released and can then be use again by your program for anything it needs -- that's not what you want. By moving the declaration outside of the for loop, you insure that A continues to exist in scope until you exit the block that contains A.

Upvotes: 1

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