Question

I am writing small IRC Bot, and i need to split incoming messages for easier handling. I wrote a function get_word, which should split string. According to gdb and valgrind, problem is that function sometimes returns invalid pointer, and program fails when trying to free that pointer.
Here is the code:

char **get_word(char *str) {
   char **res;
   char *token, *copy;
   int size = 1;
   for(int i = 0; str[i] != '\0'; i++) {
      if(str[i] == ' ') {
         while(str[i] == ' ') {
            i++;
         }
         size++;
      }
   }
   res = malloc((size + 1) * sizeof(char *));
   copy = strdup(str);
   token = strtok(copy, " ");
   for(int i = 0; token != NULL; i++) {
      res[i] = strdup(token);
      token = strtok(NULL, " ");
   }
   free(copy);
   res[size] = NULL;
   return res;
}

Answer 1

One problem I see is with your nested loops:

Consider this input: ' \0'

The function execution reaches the for loop, i == 0. Then the while loop is also entered. At the end of while loop i == 1. Now the incrementation statement from the for loop is executed and i == 2. So next you will be reading past the end of the string.

EDIT

I understand that size is the number of words found in the input. So I’d go for something like:

for (int i = 0; str[i] != '\0'; ++i) {
    if (str[i] != ' ' && (str[i + 1] == ' ' || str[i + 1] == '\0')) {
         // Counting endings of words
         size++;
    }
}