Question

I need to count the characters in the comments from a C program, that is supplied as a standard input. This is my function, but for some reason it’s not counting right. Can you help me please?

int characters(FILE *file)
{
     int i=0;
     char ch[500], *p;
     while (fgets(ch, sizeof(ch),file)!=NULL)
     {
        p=ch;
        while (*p)
        { 
           if (*p=='/')
           { 
              p++;
              if (*p=='*')
              {
                 p++;
                 while (*p!='*' && *(p++)!='/')
                 {
                    i++;
                    p++;
                 }
              }
           }
           else
              p++;

         }


   return i;
}

Answer 1

I think the problem is in the innermost loop:

while (*p!='*' && *(p++)!='/')

should be

while (*p!='*' && *(p+1)!='/')

But this will break if it sees something like this:

/* comment * */

because the first part of the condition *p!='*' will be false at the first asterisk, so you could do something like this instead:

while (!(*p=='*' && *(p+1)=='/')) {
   p++;
   i++;
}

Note: if the line is broken you will get a segmentation fault:

    /* comment * \n
    */

you still have to deal with that but you should add *p to the inner loop:

while (*p && !(*p=='*' && *(p+1)=='/')) {
   p++;
   i++;
}