getting Floating point exception (core dumped). I dont know how to fix it

Question

In the key function is gives the error. Atleast thats what gdb says. Thanks in Advance.

#include <stdio.h>
#include <stdlib.h>
#include <iostream>   // for cin and cout in C++
#include <cassert>    // for assert
#include <strings.h>
#include <string.h>
#include<time.h>
using namespace std;

int lcombinations=0;
int distinct=0;

linear hash function.

void linear(char *tword, int key, int n, char **lcArray)
{
int c;
while(c==0)
{
    if(key==n)
    {
        key=0;
    }
    if(strlen(lcArray[key])==0)
    {
        lcArray[key]=tword;
        c=1;
    }
    else
    {
        key++;
        lcombinations++;
    }
}   
}

generates key for the hash function

void key(char *tword, int l, int n, char **lcArray)
{
int total=0;
int k;
for(int i=0; i<l; i++)
{
    total= total+tword[i];
}
total=n%total;
k=rand()%25+66;
total=total*k;
linear(tword, total, n, lcArray);
}

int counter=0;

finds all the distinct words in the test.

void distinct_words(char *tword, char **distinct, int l, int n, char **lcArray)
{
int j;
int k=0;
if(counter==0)
{
    counter++;
    distinct[0]=tword;
    key(tword,l,n,lcArray);
}
else
{
    for(j=0; j<counter; j++)
    {
        if(strcmp(distinct[j],tword)!=0)
        {
            k++;
        }
    }
    if(k==counter)
    {
        distinct[counter]=tword;
        counter++;
        key(tword,l, n, lcArray);
    }
}

}

receives and breaks the text into words

int main()
{
srand(time(NULL));
FILE *inFile;
char word[81];
char *tword;
inFile = fopen("will.txt", "r");    // Open for reading, hence the "r"
assert( inFile);            // make sure file open was OK
int i=0;
int n=65437;
int j,k;
char **distinct= (char **)malloc(sizeof(char **)*n);
char **lcArray= (char **) malloc(sizeof(char*)*n);
for(int p=0; p<n; p++)
{
    lcArray[p]= (char *) malloc(sizeof(char)*81);
}
while(fscanf(inFile, "%s",word) != EOF)
{
    i++;
    k= strlen(word);
    tword= (char *)malloc(sizeof(char)*k);
    int l=0;
    for(j=0; j<k; j++)
    {
        if(isalnum(word[j]))
        {
            word[j]=toupper(word[j]);
            tword[l]=word[j];
            l++;
        }
    }
    printf("%s ", tword);
    distinct_words(tword, distinct, l, n, lcArray);
}

}

Answer 1

My suspicion is that your floating point exception is generated by this line:

total=n%total;

... specifically, if total is zero, that can cause a floating point exception on many systems.

You can avoid the exception by guarding against the possibility of the modulo value being zero:

if (total != 0)
{
   total=n%total;
}
else 
{
   printf("Hey, modulo by zero is undefined!  (It's similar to divide-by-zero!)\n");
   total = 0;  // or something
}

By the way, one key thing you'll need to learn -- if you want to retain your sanity while programming -- is how to track down exactly where in your code a crash is occurring. You can do this using a debugger (by single-stepping through the code's execution, and/or by setting breakpoints), or you can deduce where the crash occurred by sprinkling temporary printf()'s (or similar) throughout your code so that you can see what gets printed just before the crash, and use that to narrow down the problem location. Either technique will work, and one or the other is usually necessary when merely eyeballing the code doesn't give you the answer.