c - linked list is crashing my program -

hello coding program accepts user input string , tokenize , store linked list. i've tested linked list manual mean word word input without using strtok() , works fine maybe there strtok(). not sure though may check implementation of linked list.

here code:

#include <stdio.h> #include <stdlib.h> #include <string.h>  typedef struct wordnode node; struct wordnode {     char *word;     char *nextword;     node *next; };  node *head = null; node *tail = null;  node* createlist(char*, char*); node* addtolist(char*, char*); void printlist(void);  int main(void) {     char input[2048];     char *userword, *firstword, *nextword;      gets(input);      userword = strtok(input, " .,!?;:");      while(userword != null)     {         firstword = userword;         userword = strtok(null, " .,!?;:");         nextword = userword;         addtolist(firstword, nextword);      }      printlist();      return 0; }  node* createlist(char* word, char* nextword) {     node *ptr = malloc(sizeof(node));      if(ptr == null)     {         /*node creation failde*/         return null;     }      ptr->word = malloc((strlen(word) + 1)*sizeof(char));     ptr->nextword = malloc((strlen(nextword) + 1)*sizeof(char));     ptr->word = strdup(word);     ptr->word = strdup(nextword);     ptr->next = null;      head = tail = ptr;      return ptr; }  node* addtolist(char* word, char* nextword) {     if(head == null)     {         return createlist(word, nextword);     }      node *ptr = malloc(sizeof(node));      if(ptr == null)     {         /*node creation failed*/         return null;     }      ptr->word = malloc((strlen(word) + 1)*sizeof(char));     ptr->nextword = malloc((strlen(nextword) + 1)*sizeof(char));     ptr->word = strdup(word);     ptr->word = strdup(nextword);     ptr->next = null;      tail->next = ptr;     tail = ptr;      return ptr; }  void printlist(void) {     node *ptr = head;      while(ptr != null)     {          printf("\n--%s----%s--\n", ptr->word, ptr->nextword);         ptr = ptr->next;     } } 

i removed string malloc part , noticed i've put nothing on *nextword pointer why printing random special chars.

node* createlist(char* word, char* nextword) {     node *ptr = malloc(sizeof(node));      if(ptr == null)     {          /*node creation failde*/         return null;      }      //ptr->word = malloc((strlen(word) + 1)*sizeof(char));     //ptr->nextword = malloc((strlen(nextword) + 1)*sizeof(char));     ptr->word = strdup(word);     ptr->nextword = strdup(nextword);     ptr->next = null;      head = tail = ptr;      return ptr; }  node* addtolist(char* word, char* nextword) {     if(head == null)     {         return createlist(word, nextword);     }      node *ptr = malloc(sizeof(node));      if(ptr == null)     {         /*node creation failed*/         return null;     }      //ptr->word = malloc((strlen(word) + 1)*sizeof(char));     //ptr->nextword = malloc((strlen(nextword) + 1)*sizeof(char));     ptr->word = strdup(word);     ptr->nextword = strdup(nextword);     ptr->next = null;      tail->next = ptr;     tail = ptr;      return ptr; }