io - C trie node reassignment causing segmentation fault -

i trying implement spellchecker, , 1 step load dictionary trie structure. have used gdb determine that, understanding, getting segmentation fault every time try assign current->children value. full code @ bottom, method in question:

bool load(const char* dictionary) {     file* dic = fopen(dictionary, "r");      if(dic == false)     {         return false;     }      root = calloc(27, sizeof(node));     node* current = null;     /**for(int i=0;i<27;i++)     {         current->children[i]=null;     }*/ //this location of segmentation fault if uncommented     int = 0;      while((a = fgetc(dic)) != eof)     {         if (a == '\n')         {             //this end of word             if(!current->is_word)             {                 //duplicate case                 current->is_word = true;                 wordcounter++;             }             current = root;                 }         else         {             if(current->children[a-'a'] == null)             {                 current->children[a-'a'] = calloc(27,sizeof(node));             }             current = current->children[a-'a'];         }     }     if(current!= root && !current->is_word)     {         current->is_word = true;         wordcounter++;     }      fclose(dic);     return true; } 

there commented code there tried implement after checking couple other answers on stackoverflow, causes segmentation fault occur @ for loop. otherwise, occurs @ if(current->children[a-'a']==null){...}

what's happening here? thought calloc() automatically set assigned memory 0? memory touching i'm not supposed to?

full .c below:

#include <stdbool.h> #include <stdio.h> #include <stdlib.h> #include <ctype.h>  #include "dictionary.h"  typedef struct node {     bool is_word;     struct node* children[27]; } node;  node* root; int wordcounter=0;    //returns true if word in dictionary else false.  bool check(const char* word) {     node* current = root;     int b = 0;      while(word[b] != '\n')     {         int letter = tolower(word[b]);          if(letter == '\'')         {             return false;         }          if(current->children[letter-'a'] != null)         {             current = current->children[letter-'a'];             b++;         }         else         {             return false;         }     }      if(current->is_word == true)     {         return true;     }        return false; }    // loads dictionary memory.  returns true if successful else false. bool load(const char* dictionary) {     file* dic = fopen(dictionary, "r");      if(dic == false)     {         return false;     }       root = calloc(27, sizeof(node));     node* current = null;     /**for(int i=0;i<27;i++)     {         current->children[i]=null;     }*/     int = 0;      while((a = fgetc(dic)) != eof)     {         if (a == '\n')         {             //this end of word             if(!current->is_word)             {                 //duplicate case                 current->is_word = true;                 wordcounter++;             }             current = root;                 }         else         {             if(current->children[a-'a'] == null)             {                 current->children[a-'a'] = calloc(27,sizeof(node));             }             current = current->children[a-'a'];         }     }     if(current!= root && !current->is_word)     {         current->is_word = true;         wordcounter++;     }      fclose(dic);     return true; }   //returns number of words in dictionary if loaded else 0 if not yet loaded.  unsigned int size(void) {     return wordcounter; }    //unloads dictionary memory.  returns true if successful else false.  void memfree(node* current) {     for(int = 0; < 27; i++)     {         if(current->children[i] !=null)         {             memfree(current->children[i]);         }     }     free(current); }  bool unload(void) {     memfree(root);         return true; } 

the error happens because you're initializing current = null, dereferencing (current->children). it's straight null pointer dereference.

looking @ rest of code, meant do

node *current = root; 

instead.