Question

My Problem is, that this code just works with tiny input-strings

The code should check if a input is an Palindrom. And there are two options, i implement them in extra functions (this error also appers, when i comment the functions out)

for example:
input “otto” – is okay
“reliefpfeiler” – is okay
“xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx” –> segmentation fault

int main(int argc, char **argv)
{
   char* str;
   int erg;
   int c;
   char stroriginall[50];

   fgets(str,50,stdin);
   str[strlen(str)-1]='\0'; 

   if(strlen(str)>40)
   {
      printf("%s: Error, input must <=40!",argv[0]);
      return 1;
   }

   strcpy(stroriginall,str);

   while ((c=getopt(argc, argv, "si")) != -1)
   {
      switch(c)
      {
      case 's':
         str=removeSpaces(str);
         break;
      case 'i':
         toLowerCase(str);
         break;
      }
   }

   erg=checkPalindrom(str);

   if(erg==0)
   {
      printf("%s ist ein Palindrom\n",stroriginall);
   }
   else
   {
      printf("%s ist kein Palindrom\n",stroriginall);
   }

   return 0;
}

i hope anybody can help me 🙂

Answer 1

One of your problems is that str is just a pointer (uninitialised for that matter) and you haven’t allocated any memory for it. See:

char* str;
int erg;
int c;
char stroriginall[50];

fgets(str,50,stdin);

Change char* str to char str[50]. That call to fgets stores 50 chars into the buffer pointer to by str, there’s no memory allocated for str so you’ll segfault.

We also don’t have the definition to the functions your calling where there could be plenty more problems.

You should also enable all of the warnings on your compiler so these problems are pointed out to you at compile time (if it didn’t already do so).