CODEWITHSUNDEEP
cpointersstructure
Learning C
Learning C

Reputation: 689

Why cant I set this pointer to NULL?

I'm having some problems setting a pointer within a structure to NULL. I'm getting a segimtation fault. What is causing this and how can I fix it?

typedef struct data_{
  void *data;
  struct data_ *next;
}data_el;

typedef struct buckets_{
  char *key;
  data_el *head_data_p;
}buckets;

typedef struct hash_table_ {
  /* structure definition goes here */
  int (*hash_func)(char *);
  int (*comp_func)(void*, void*);
  buckets **buckets_array;
} hash_table, *Phash_table;

int i,size;
size = 10;

table_p -> buckets_array = (buckets **)malloc(sizeof(buckets)*(size+1));

for(i = 0; i < size; i++){
/*Getting segmitation falut here*/
table_p -> buckets_array[i] -> key = NULL;
table_p -> buckets_array[i] -> head_data_p = NULL;

Upvotes: 0

Views: 264

Answers (2)

Jonathan Wood
Jonathan Wood

Reputation: 67345

Because you aren't initializing buckets_array. So the pointers don't yet point to anything and you get an error when you try and modify what they point to.

You need to initialize your array of pointers, and also each individual pointer:

table_p -> buckets_array = malloc(sizeof(buckets *) * (size+1));

for(i = 0; i < size; i++) {
    table_p -> buckets_array[i] = malloc(sizeof(bucket));
    table_p -> buckets_array[i] -> key = NULL;
    table_p -> buckets_array[i] -> head_data_p = NULL;
}

Upvotes: 2

fjardon
fjardon

Reputation: 7996

You should replace: 

buckets **buckets_array;

With: 

buckets *buckets_array;

And: 

(buckets **)malloc(sizeof(buckets)*(size+1));

With: 

(buckets *)malloc(sizeof(buckets)*(size+1));

And also:

table_p -> buckets_array[i] -> key = NULL;
table_p -> buckets_array[i] -> head_data_p = NULL;

With:

table_p -> buckets_array[i] . key = NULL;
table_p -> buckets_array[i] . head_data_p = NULL;

Upvotes: 1

Related Questions