Thread: Segmentation Fault building array of strings from input record

I'm trying to build an array of strings from an input record. I'm getting a segmentation fault. Here's my code. The segmentation fault occurs on line 28, "strcopy..."

Suggestions? Thanks!

Code:

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <stdbool.h>
#include <ctype.h>

/* Windows filenames */
#define xtni_filename "In_Transactions.ofx" /* OFX */
#define xtni_line_len 55
FILE *xtni;
bool sw_xtni_eof = false;

char *get_xtni(int xtni_words_max, char xtni_words[])
{
    char line_xtni_cur[xtni_line_len];
    if (fgets(line_xtni_cur, xtni_line_len, xtni) == NULL) {
        sw_xtni_eof = true;
        return xtni_words;
    }

    char * xtni_cur_word;
    int xtni_num_words = 0;
    xtni_cur_word = line_xtni_cur;
    printf("line_xtni_cur: %s\n", line_xtni_cur); // testing
    xtni_cur_word = strtok (xtni_cur_word," "); // first word
    while (xtni_cur_word != NULL) {
        strcpy(&xtni_words[xtni_num_words], xtni_cur_word);
        xtni_cur_word = strtok (NULL," "); // next word
        xtni_num_words++;
        }

    return xtni_words;
}

int main()
{
   xtni=fopen(xtni_filename, "r");
   int xtni_words_max = 12;
   char * xtni_words[xtni_words_max];
   while (sw_xtni_eof == false) {
      char *xtni_words = get_xtni(xtni_words_max, xtni_words);
   }

   printf(xtni_words[0]);  // testing
   return 0;

}

Thanks for the replies. The key was laserlight's last statement

Originally Posted by laserlight

The xtni_words array has xtni_words_max elements. You should avoid accessing the array out of bounds by checking that xtni_num_words < xtni_words_max before using xtni_words[xtni_num_words].

Here is my solution...

Code:

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <stdbool.h>
#include <ctype.h>

/* Windows filenames */
#define XTNI_FILENAME "In_Transactions.ofx" /* OFX */
#define XTNI_LINE_LEN 55
FILE *xtni;

char *get_xtni(unsigned int xtni_words_max, int xtni_line_num, 
                   char xtni_words[])
{
    static char xtni_line_cur[XTNI_LINE_LEN];
    if (fgets(xtni_line_cur, XTNI_LINE_LEN, xtni) == NULL) {
       return NULL;
    }
    // check for missing newline character (line length too small)
    if (xtni_line_cur[strlen(xtni_line_cur)-1] != '\n') {
       printf("Line length too small \n");
       printf("xtni_line_cur: %s\n", xtni_line_cur);
       getchar();
       return xtni_line_cur;
    }

    char * xtni_cur_word;
    int xtni_num_words = 0;
    xtni_cur_word = xtni_line_cur;
    printf("xtni_line_cur: %s\n", xtni_line_cur); // testing
    xtni_cur_word = strtok (xtni_cur_word," "); // first word
    while (xtni_cur_word != NULL) {
        strcpy(&xtni_words[xtni_num_words], xtni_cur_word);
        xtni_cur_word = strtok (NULL," "); // next word
        xtni_num_words++;
        }

    // check for max string length
    if (strlen(xtni_words) > xtni_words_max) {
       printf("xtni_words_max too low \n");
       printf("xtni_words_max: %i\n", xtni_words_max);
       printf("xtni_line_num: %i\n", xtni_line_num+1);
       getchar();
       return xtni_line_cur;
    }

    return xtni_line_cur;
}

int main()
{
   xtni=fopen(XTNI_FILENAME, "r");
   if (xtni == NULL) {
       int errnum = errno;
       printf ("%d\n", errnum); // Convert int to char
       printf ("Error opening file. \n");
       printf ("Error Number: %i\n", errnum);
       printf ("File Name: %s\n", XTNI_FILENAME);
       printf ("Error message: %s\n", strerror(errnum));
   }

   unsigned int xtni_words_max = 48;
   char xtni_words[xtni_words_max];
   int xtni_line_num = 0;
   while (get_xtni(xtni_words_max, xtni_line_num, xtni_words) != NULL); {
      printf("%s", &xtni_words[0]);  // testing
      xtni_line_num++;
   }

   return 0;

}

Comments? Suggestions?

This is more educational than a class. Thanks.

Originally Posted by Salem

You need to check this before every attempt to modify xtni_words, not once at the end.
If the condition is true at this point, it's already game over.

Excellent observation. I modified it.

Originally Posted by Salem

> printf("%s", &xtni_words[0]);
Is a long way of saying printf("%s", xtni_words);

Thanks, I modified it.

Originally Posted by Salem

The while loop on line 66 isn't doing what you want.

I copied in a couple of printf statements from my larger program as follows:

Code:

    while (xtni_cur_word != NULL) {
        strcpy(&xtni_words[xtni_num_words], xtni_cur_word);
        xtni_cur_word = strtok (NULL," "); // next word
        printf("Word number: %i\n", xtni_num_words+1); //testing
        printf("Word: %s\n", &xtni_words[xtni_num_words]); //testing
        getchar(); // testing
        xtni_num_words++;
        }

And here's an example of what I got:

xtni_line_cur: <NAME>BORICS HAI
R CARE ELKHART

Word number: 1
Word: <NAME>BORICS

Word number: 2
Word: HAIR

Word number: 3
Word: CARE

Word number: 4
Word: ELKHART

This is exactly what I expect.