Can someone help me figure out what's wrong with this program? (C) -


i doing easy challenge on /r/dailyprogrammer in c. managed write on hundred lines of code, , spend couple hours total on (usually end chickening out), , figure out compiler errors. now, when run it, segfault. i'm doing wrong?

yes, it's sort of homework help, @ least tried before coming here.

#include <ctype.h> #include <stdio.h> #include <string.h>  #define maxlen  50 #define limit   20 #define true    1 #define false   0  char* reverse(char *a); char* ltoa(long i); long atol(char *a); /* note: handle leading zeros. */ long palindromize(long p); int ispalindrome(long p);  /* meat. */  int main(int argc, char *argv[]) {     long p;     int count, limr;      p = (long) argv[1];     count = 0;     limr = false;      while (true)     {         p = palindromize(p);         count++;         if (ispalindrome(p))         {             break;         } else if (count == limit) {             limr = true;             break;         }     }      if (limr)     {         printf("it might palindrome, it'd take quite while find out.\nlast number reached: %ld\n", p);     } else {         printf("palindrome found!  after %d steps, we've found %ld.\n", count, p);     } }  long palindromize(long p) {     return (atol(reverse(ltoa(p)))) + p; }  int ispalindrome(long p) {     char *t, *r;      t = ltoa(p);     r = reverse(ltoa(p));      if (t == r)     {         return true;     } else {         return false;     } }  /* utility functions. */  /* converts string long integer. */ long atol(char *a) {     int i, sign;     long r;      (i = 0; a[i] == '0'; i++)     {         i++;     }      if (a[0] == '-' || a[-1] == '-')     {         sign = -1;     }     else     {         sign = 1;     }      (; isdigit(a[i]); i++)     {         r = 10 * r + (a[i] - '0');     }      return r * sign; }  /* converts long integer string.    , reverse based on ones in k&r. */ char* ltoa(long n) {     char *a;     int i, sign;      if ((sign = n) < 0)     {         n = -n;     }      = 0;         {         a[i++] = n % 10 + '0';     } while ((n /= 10) > 0);      if (sign < 0)     {         a[i++] = '-';     }     a[i] = '\0';      return reverse(a); }  char* reverse(char *s) {     int i, j;     char c;      (i = 0, j = strlen(s)-1; i<j; i++, j--) {         c = s[i];         s[i] = s[j];         s[j] = c;     }      return s;  }

in ltoa declare char *a; never malloc space it. when access a[i] crashes. problems this, remember simple first debugging step add print statements everywhere can @ least pinpoint error occurring.

looks ispalindrome wrong too, not in seg fault way. i'll let figure out why =d


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