Thread: Seg faults. structs. pointers.

I'm having trouble with this program. it reads in a list of words from a text file and allows you to add words, search for words, compare 2 lists and print the list. the first line of the text file contains the language of the words, and the second line contains the number of words. the following lines contain the words. like so:

Code:

english
14
abjure
abrogate
abstemious
acumen
antebellum
auspicious
belie
bellicose
bowdlerize
chicanery
chromosome
churlish
circumlocution
circumnavigate

im getting a problem when i try to fscanf a value into the num_words variable in the structure. i get a seg fault error there.

another problem im getting is where i let the for loop in open_file() run until MAX_WORDS... it gets crazy( line 76).
i wrote the program to print the words read in so i can see that it was reading the file OK. when it runs till MAX_WORDS it prints all kinds of crazy characters and stuff. but if i change it to a->num_words it wont run. i know it has something to do with the pointers but i dont know how to fix it. ive spent like 3 hours trying to figure it out.

also in that function there is the fscanf for a->lang and a->num_words. i have them commented out because i was trying to just increment a->num_words(line 78) this solved the first problem but didnt solve the following problem.

and lastly, in the add_word() function when i add the words to a->b[num_words + 1] i get another seg fault.

please let me know if you can help.

here is the code

Code:

# include <stdio.h>
# include <string.h>

# define MAX_WORDS      20

struct wordlist {
       char lang[15];
       int num_words;
       char b[MAX_WORDS][21];
};

void    open_file(struct wordlist *a);
void    add_word(char word[21], struct wordlist *a);
int     contains(char word[21], struct wordlist a);
void    display_word_list(struct wordlist a);

int main() {
    struct  wordlist a;
    char    word[21];
    int     c=0, sel, i=0;
            
    open_file(&a);       
	
		printf("Option 1\tAdd A Word\n");    
		printf("Option 2\tContains\n");
		printf("Option 3\tEqual Lists\n");
		printf("Option 4\tDisplay List\n");
		printf("Option 5\tExit\n");
		scanf("%d", &sel);
		
        if (sel ==1) {            
            printf("please enter a word to add: \n");
            scanf("%s", &word); 
            add_word(word, &a);
            printf("SUCCESS\n");
            for( i = 0; i <= MAX_WORDS; i++ ) {                        
                printf("%s\n", a.b[i]);   
            }
        }
                
        else if (sel ==2) {
            printf("Enter a word to search for: \n");
            scanf("%s", &word);
            c = contains(word, a);
            if( c == 1) 
                printf("Word Found"); 
            else if ( c == 2) 
                printf("Word Not Found"); 
        }
                        
        else if (sel ==3) {
                
        }
        else if (sel ==4) {
                
        }
        else if (sel ==5)
            return(0); 
        
        
    
system("pause");
    return(0);
}

void open_file(struct wordlist *a){
    
    FILE    *ifp;
    int     i=0, j=0;
    
        ifp = fopen("input.txt", "r");
        //fscanf(ifp, "%s", a->lang);
        //fscanf(ifp, "%d", a->num_words);
        
        for( i = 0; i <= MAX_WORDS; i++ ) {                 
            fscanf(ifp, "%s", a->b[i]); 
			a->num_words++;         
        }
        for( i = 0; i <= MAX_WORDS; i++ ) {                        
                printf("%s\n", a->b[i]);   
        }
	
		fclose(ifp);
}

void add_word(char word[21], struct wordlist *a) {

    int     i=0, j;  
    
		
        if ( a->num_words == MAX_WORDS ) {
            printf("List full, word not added.");
        }
        else {
            for ( i = 0; i < a->num_words; i++) {
                if(strcmp(a->b[i], word)==0) {
                    break;
                }
                else {
                    printf("check");
                    strcpy(a->b[a->num_words+1], word);
                    //printf("check");
                }
            }
        }
          
}

int contains(char word[21], struct wordlist a) {
    int    i=0;   
     
    for ( i = 0; i <= a.num_words; i++) {
        if (strcmp(a.b[i], word)==0) {
            return(1);
        }
        else {
            return(2);  
        }                
    }
}


/*
void equal_lists() {
     
     
     
              
}

void display_word_list(struct wordlist a) {
     int i=0;
     
         for (i=0; i<a.num_words;i++) {
             printf("%s\n", a.b[i]);
         }
     
     
     
}
*/

i just realized that contains() doesent work either. but dont bother trying to figure it out unless it just jumps out at you.

thanks a lot for the help.

> for( i = 0; i <= MAX_WORDS; i++ )
Well this ALWAYS steps off the end of your array, no matter what else happens.

To index the array, it's
for( i = 0; i < MAX_WORDS; i++ )

Add to that, you should look at the return result of fscanf to determine whether any data was read.
Or perhaps even use the second line (which I guess is the number of words)

Post your latest code

> fscanf(ifp, "%d", &a->num_words);
> printf("NUMWORDS %d\n", a->num_words);

If you're using gcc (or an IDE like code::blocks which uses gcc as it's compiler), then add the
-Wall
compiler option.
It will tell you a lot of useful stuff.

Yeah, that's another IDE which also uses gcc under the hood.

Something like project->settings->compiler->options should get you close to where you can add your own flags.