Reading in words into a linked list - c

Question

Im trying to write a program that reads each word inputted by user and then sticks that word into a linked list. This is what I have tried so far but got seg faults but not too sure where I went wrong with mallocing/pointers. (Havent implemented printList yet).
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define MAX_LEN 20
typedef struct node{
char *word;
struct node *next;
}node_t;
node_t *read(node_t *node);
void printList(node_t *node);
node_t *insertNode(char *word, node_t *node, int size);
int main(int argc, char *argv[]) {
node_t *start = NULL;
printf("Enter a sentence:\n");
read(start);
return 0;
}
void *read(node_t *node){
int i, size = MAX_LEN;
char c, *word;
if(!(word=malloc(size))){
printf("Out of memory!\n");
exit(EXIT_FAILURE);
}
while((c=getchar())!='\n'){
for(i=0;c!=' ';i++){
word[i]=c;
if(i>size){
size=size*2;
if(!realloc(word, size)){
printf("Out of memory\n");
exit(EXIT_FAILURE);
}
}
}
node = insertNode(word,node,size);
}
return node;
}
node_t *insertNode(char *word, node_t *node, int size){
node_t *new_node, *current;
new_node = (node_t*)malloc(sizeof(node_t));
new_node->next = NULL;
if(!(new_node->word = malloc(size))){
printf("Out of memory\n");
exit(EXIT_FAILURE);
}
strcpy(new_node->word,word);
if (node == NULL){
node = new_node;
current = new_node;
}
else{
current->next = new_node;
current = new_node;
}
return node;
}

Answer 1

There are several issues:
Your prototype and the implementation of read don't match; make both return a node_t *.
You have two nested loops for input, one reading from stdinand another one cycling through the characters. The inner loop never updated its condition, because c can only be changed by the outer loop. There should be just one loop, which takes care of reading from the stream and writing to the string.
You don't keep tzhe result of realloc, which means that you don't reflect updates when the handle to the allocated memory changes. In these cases, you will access the old handle, which has become invalid.
You don't terminate your string with a null character.
You should reallocate before you access memory out of bounds. That usually means to check whether to enlarge the array before writing to it. Note that for an array of length n, n itself is already an illegal index.
The result of getchar should be an int, ot a char so that all valid input is distinct from EOF, for which you don't check.
Therer are probably more issues, the ones listed are the ones concerned with read. I haven't looked into the linked list insertion.
In order to properly terminate the string with a zero, I recommend to write an infinite loop and postpone the break condition after possible reallocation. Foe example:
node_t *read(node_t *node)
{
int size = MAX_LEN;
int i = 0;
char *word = malloc(size);
if(word == NULL) {
printf("Out of memory!\n");
exit(EXIT_FAILURE);
}
while (1) {
int c = getchar();
if(i >= size) {
size = size*2;
word = realloc(word, size);
if (word == NULL) {
printf("Out of memory\n");
exit(EXIT_FAILURE);
}
}
if (c == '\n' || c == EOF) {
word[i] = '\0';
break;
}
word[i++] = c;
}
node = insertNode(word, node, size);
return node;
}

Answer 2

I think the error is caused by the line
return node;
in insertNode. That should be
return new_node;