Thread: Please help! My program hangs when calling function, can you tell me why?

I haven't been able to test the logic inside the function yet (which I know isn't complete yet) as my program just hangs when it try to call substrings().

I have lots of messages printing to try and debug. I am only just starting to learn C so apologise for my inelegant code.

Any help to get me past this hurdle would be very much appreciated. Thank you in advance.

Code:

#include <stdio.h>
#include <ctype.h>
#define TRUE 1
#define NUM_OPTION_STATS 5
#define MAX_SUB_STRING_INPUT 20

int substrings( int *optionStats, char *source, char *subString);

int main(void){
   
   int optionStats[NUM_OPTION_STATS];
   int i=0, j=0;
   char source[MAX_SUB_STRING_INPUT] = {0};
   char subString[MAX_SUB_STRING_INPUT] = {0};
   
   char in;
   int finished1 = 0;
   int finished2 = 0;
   
   printf("Substrings\n");
   printf("-----------\n");
   
   do {
      printf("Enter a string (1-20 characters): ");
      
      while ((in = getchar())!= '\n') {
         source[i++] = in;
      }
      
      source[i] = '\0';
      
      if (i=0)
      {
         fputs("You haven't entered anything. Please try again. \n", stderr);
         
      }
      else {
         
         finished1=1;
         
      }
      
   } while (finished1==0);
   
   printf("should have worked\n");
   printf("check source: %s\n", source);
   i=0;
   while (source[i] != '\0') {
      putchar(source[i++]);
   }
   printf("\nMove onto substring\n");
   
   
   
   do {
      printf("Enter a substring (1-20 characters): ");
      
      for (j=0;  (in = getchar()) != '\n'; ++j) {
         printf("%c\n", in);
         subString[j] = in;
         printf("%c\n", subString[j]);
         
      }
      subString[j] = '\0';
      if (j=0)
      {
         fputs("You haven't entered anything. Please try again. \n", stderr);
         
      }
      
      if (j<=MAX_SUB_STRING_INPUT) {
         finished2=1;
      }
      
   } while (finished2==0);
   
   printf("should have worked\n");
   printf("check substring: %s\n", subString);
   printf("check substring 1st character: %c\n", subString[0]);
   
   printf("About to call function\n");
   printf("Let's check source again first: %s\n", source);
   
   substrings(optionStats, source, subString); //this is where it hangs
   printf("Function called\n");
   
}




/****************************************************************************
 * Function substrings() is an implementation of the strstr() standard library
 * function.
 ****************************************************************************/
int substrings(int *optionStats, char* source, char* subString)
{
   printf("You made it into the substring function!");
   int i, j, k;
   int source_length, substring_length;
   
   /*determine length of source string*/
   for (i=0; i<MAX_SUB_STRING_INPUT; i++) {
      while (source[i] != '\0') {
         source_length++;
      }             
   }
   /*TEST*/
   printf("%d\n", source_length);
   
   /*determine length of substring string*/
   for (i=0; i<MAX_SUB_STRING_INPUT; i++) {
      if (subString[i] != '\0')
         substring_length++;
   }
   
   /*TEST*/
   printf("%d\n", substring_length);
   
   
   for (j=0; j<substring_length; j++) {
      for (k=0; k<source_length-substring_length; k++) {
         if (source[k] && subString[j] == 0) {
            j++;
         }
      }
   }
   
   if (j == substring_length) {
      printf("Output: \"%s\" is a substring of \"%s\"", subString, source);
   }
   else {
      printf("Output: \"%s\" is NOT a substring of \"%s\"", subString, source);
   }
   
   
   optionStats[3]++;
   
   return TRUE;
}

Thank you for your prompt response Salem.

So my problem is in the function, not in main? I thought because it hadn't printed the inside function message it hadn't even made it there.

I will think about your comments and have another go. I might be back with another question! thanks again.

Look closely... what does this section of code do to your loop's exit condition?

Code:

     else {
        finished1=1;
      }
   } while (finished1==0);

Hi Tater,

Thanks for your assistance.

I'm sorry, but I can't see the problem with this. I thought by setting finished1 to 1, I am not meeting while condition of finished 1 being equal to 0 and therefore breaking out of the loop.

Is this reasoning incorrect?

(BTW I have now gotten this called function to work correctly and I am trying to implement input validation. So your comment is timely!)

Yep you are right Salem - I was wanting to compare not assign there. I noticed this working through the input validation and have fixed, silly mistake!
Cheers again.