How to get rid of this segmentation error?

Question

void search(FILE *fp){
  char lines[81];
  char iden[11];


int i = 0;
  int count = 1;
     while(!feof(fp)){
       fgets(lines,80,fp);
       // If the line dosesn't start with #, space, or tab, it has identifier
       if (lines[0] != '#' && lines[0] != ' ' && lines[0] != '\t'){
       // An identifier ends with ':'
         while (lines[i] != ':'){
           iden[i] = lines[i];
           ++i;
         }
         ins(iden, count);
       }
            ++count;
  }
}

I am getting an error like this:

p4.c:93:12: runtime error: index 11 out of bounds for type 'char [11]'

p4.c:92:17: runtime error: index 81 out of bounds for type 'char [81]'

p4.c:93:22: runtime error: index 81 out of bounds for type 'char [81]'

Segmentation fault

Note: My input file contains data according to error checks above. I mean each line as at most 80 characters including \n and the max size of an identifier is 10. And lines that doesn't start with '#' or space or tab contains an identifier at the begining of the line that ends with ':' with maximum size of 10 including ':'

It is happening in the second while loop on the above code? Why am I getting this error?

p.s: I already opened my file and checked it in my main method

`while(!feof(fp)){ fgets(lines,80,fp);` feof() is always wrong http://stackoverflow.com/q/5431941/905902 — wildplasser, Nov 20 '16 at 19:36
remove the feof() and use the return value from fgets() instead. — wildplasser, Nov 20 '16 at 19:40

score 0 · Accepted Answer · answered Nov 20 '16 at 19:43

You never reset the counter i and don't add a terminator to the identifier.

So try:

i=0;
while (lines[i] != ':'){
     iden[i] = lines[i];
     ++i;
 }
 iden[i]='\0';

But for safety you should put in protection so actually use:

while (lines[i] != ':' && i<10){

Never trust input and always make sure your program will never exceed bounds of its variables.

How to get rid of this segmentation error?

1 Answers1