Question

Here is my relatively simple scenario, and I’m wondering if I can save myself a conditional and tidy the code up a bit. Its production code that someone else wrote and I’m just tidying up. It had no fclose at all, so all I have added is the conditional fclose() lines:

  FILE *fp;
  struct stat sb;
  /* snipped code */
  if (((fp = fopen (config_file, "r+")) == NULL) || (fstat (fileno (fp), &sb))) {
      syslog (LOG_ERR, "Fault. Unable to read config file");
      if (fp != NULL) {
          fclose (fp);
      }
      return -1;
  }
  /* code carries on after this */

The question is, do I really need to have the if(fp != null) in my code? What are the implications of just doing an fclose(fp) without checking? I had a read of the C89 standard but it wasn’t clear to me from that what the results would be.

Cheers in advance

Steve

Answer 1

fclose on a null pointer has undefined behaviour. This means it could segfault or cause you problems. I would stick with your checks as they are good practise and make the code easier to read.