Retaining Common Prefix of two strings.....C Programming... Segmentation fault error......

Question

char *strip_postfix(char *str1, char *str2)
{
   int i;

   for(i=0; str2[i] != '\0'; i++)
   {
      if(str1[i] != str2[i])
      {
         str1[i] = '\0';
         break;
      }
   }
   return str3;
}

This code, is giving segmentation fault error at line str1[i] = '\0' during run time..... I think there is some memory allocation issue,, as while I create a new variable and copy the contents there, and then return that new variable, everything works fine.... Please let me know what's the issue in this.

Answer 1

What happens if str1 is smaller than str2?

You also have:

return str3;

Which makes me think this code will not compile in its current form...

Answer 2

Your code should like

int str1len =  strlen(str1);    
for(i=0; str2[i] != '\0'; i++)
   {
      if(str1[i] != str2[i] || i >= str1len)
      {
         str1[i] = '\0';
         break;
      }
   }
return str1;

Thanks