Thread: Weird Segfualt when calculating abundance

I wrote this little app today to do the simple, maybe even trivial, task of seeing if a numbers abundant. Heres my code:

Code:

/******************************************
***                                     ***
***                                     ***
*** Abundant Number - A number that is  ***
*** less than the sum of its factors    ***
*** (excluding itself). For example,    ***
*** the factors of 12 (1, 2, 3, 4, 6)   ***
*** add up to 16. Compare deficient     ***
*** number, perfect number.             ***
*******************************************/

#include <iostream.h>
#include <stdlib.h>

void abundant(int org);      //Our function to check the abudance of a number
int main(int argc, char *argv[])
{

   /*
    * If theres no arguments present then print a error message
    * and exit.
    */
   if( argc < 2 ){
      cout << "Usage: " << argv[0] << " <test number>\n";
      cout << "<test number> is the number to test for abundance.\n";
      exit(0);
      }

   /*
    * Convert the first argument to a integer.
    */
   int test;
   test = atoi(argv[1]);

   /*
    * If the integers value is higher then 200 then print a error
    * message and quit.
    */
   if( test > 200 ){
      cout << "This application only accepts numbers between 0 - 200\n";
      exit(0);
      }

   /*
    * Now we're sure that the number is applicable to our checks we
    * call our abundance checking function. The only argument to
    * this function is the integer named test. (The users argument)
    */
   abundant(test);
   return 0;
}

void abundant(int org)
{
   int i, j, test;
   int intarr[200];
   j = 0;

   /*
    * Declare a loop. The loop will execute "org" amount of time. Org
    * is the number we are testing.
    */
   for(i=0; i >= org; i++)
   {
      /*
       * When we divide "org" by "i" if theres no remainder then we will
       * add it to our integer array. This just stores "org"s factors.
       */
      if(((org % i) == 0) && (i != org))
      {
         intarr[j] = i;
         j++;
      }
   }

   /*
    *  Now we loop through our array of factors and add them all up.
    */
   for(i=0; i >= j; i++)
   {
      test += intarr[i];
   }

   /*
    * If the sum of factors is greater than the number we are testing
    * then the number is abundant.
    */
   if( test > org){
   cout << org << " - The number is abundant.\n";
   return;
   }

   /*
    * Else, if the sum of factors is equal to, or less then the
    * number we are testing we display a message with our results.
    * In this case our results are that the number ISN'T abundant.
    */
   else if( test <= org){
   cout << org << "Isn't a abundant number.\n";
   return;
   }
}

It compiled ok and I proceeded to run it. I supplied it with numbers in the correct range and it simply "crapped out". When I use a number above 200 it works perfect. (i.e displays the error message)

If I don't supply it with any arguments it does what its meant to and displays the usage.

When I supply it with the correct info it simply does nothing.

I tried to debug it with gdb, as I have only used gdb on my linux box I wasnt sure if the "no debuging symbols" was ok.

(no debugging symbols found)...(gdb)

(gdb) run 100
run 100
Starting program: \DOCUME~1\Fergus\MYDOCU~1/Abudance.exe 100
77f50000:ntdll.dllntdll.dll: No such file or directory.
77e60000:C:/WINDOWS/system32/kernel32.dll(no debugging symbols found)...
77c10000:C:/WINDOWS/system32/msvcrt.dll(no debugging symbols found)...

Program received signal SIGSEGV, Segmentation fault.
0x401432 in ?? ()
(gdb)

It throws a segfualt out. I simply don't understand how my program is accessing memory out of its allowed range.

Any ideas or Suggestions?
Thanks!
-Moddy

Originally Posted by SlyMaelstrom

Your problem is in this section:

Code:

   /*
    *  Now we loop through our array of factors and add them all up.
    */
   for(i=0; i >= j; i++)
   {
      test += intarr[i];
   }

Ah, I see now! I hav re-read my code and the for statements seem wrong. (i.e >= instead of <=) That if statement also looks incorrect (AND instead of OR).

I can't see any reasons not to enter the loop though. =/