CODEWITHSUNDEEP
cruntime-errorfree
user2905039
user2905039

Reputation: 11

free(): invalid next size(fast) error

I'm trying to tokenize strings from stdin. I am only interested in characters and build an array of each string (ignoring non-characters). For some reason when I read 24 characters or more from stdin I receive the error:

free(): invalid next size (fast):

This is the relevant code...it works fine on smaller strings (23 characters or less)

char  **tokenize(int *nbr_words) {


char **list = calloc(INITIAL_SIZE, sizeof(char *));
char * temp = NULL;
temp = malloc(sizeof(200));

while(fgets(temp,200,stdin)){

char * newWord = NULL;
newWord = malloc(sizeof(100)); 
int i = 0;


while(temp[i] != '\n'){

    if(isalpha(temp[i]) && temp[i+1] != '\n'){

        strncat(newWord,&temp[i],1);
        i++;
    }

        else if(isalpha(temp[i]) && temp [i+1] == '\n'){
            strncat(newWord,&temp[i],1);
            list[*nbr_words] = newWord;
            *nbr_words += 1;
            printf("%s\n",list[*nbr_words -1]);
            i++;
            if(*nbr_words % 10 == 9){
                list = realloc(list, *nbr_words + 10);
            }
            free(newWord);
            newWord = malloc(sizeof(100));
            *newWord = NULL;



    }else{  
        if(*newWord == NULL){
            i++;
        }
        else if(*nbr_words % 10 != 9){
            list[*nbr_words] = newWord;
            *nbr_words += 1;
            printf("%s\n",list[*nbr_words-1]);
            i++;
            free(newWord);
            newWord = malloc(sizeof(100));
            *newWord = NULL;
        }else{

            list = realloc(list, *nbr_words + 10);
            list[*nbr_words] = newWord;
            *nbr_words += 1;
            printf("%s\n",list[*nbr_words-1]);
            i++;
            free(newWord);
            newWord = malloc(sizeof(100));
            *newWord = NULL;
        }
    }
}
free(temp);

temp = malloc(sizeof(200));
*temp = NULL;  
}

return list;
}

Upvotes: 0

Views: 643

Answers (1)

timrau
timrau

Reputation: 23058

You keep allocating temp and newWord for size sizeof(200) or sizeof(100), while both of them are equal to sizeof(int) which is much smaller than you expect.

Modify 

temp = malloc(sizeof(200));
newWord = malloc(sizeof(100));

into

temp = malloc(200);
newWord = malloc(100);

Upvotes: 3

Related Questions