C getopt segfault

h/w · 01-14-2008, 11:36 AM

Don't know what more to say here other than it keeps segfaulting and I haven't yet been able to figure out why. It does so while trying to access the optarg which gdb says is at address 0.

gcc version 4.2.3 20080113 (prerelease) (Debian 4.2.2-6)

Code:

/* gcc -Wall -o foo foo.c
* ./foo -x s -f 1.0 -p 2.0 -r 3.0 -t 4.0
*/

#include <getopt.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

int main(int argc, char *argv[0])
{
  extern char *optarg;
  extern int optind;

  int opt,
      flag; 

  char *ctype = NULL;

  double fv, pv;
  
  float r, t;

  while ((opt = getopt(argc, argv, "x::f::p::r::t::")) != -1) {
    switch(opt) {
      case 'x':
	ctype = optarg;
	break;
      case 'f':
	fv = (double)atof(optarg);
	break;
      case 'p':
	pv = (double)atof(optarg);
	break;
      case 'r':
	r = (float)atof(optarg);
	break;
      case 't':
	t = (float)atof(optarg);
	break;
      default:
	abort();
    }
  }

  return 0;
}

rupertwh · 01-14-2008, 11:51 AM

Quote:

Originally Posted by h/w

Code:

int main(int argc, char *argv[0])

That '0' certainly doesn't belong in there. It's 'char *argv[]' or 'char **argv'.
That might already fix your problem. Haven't looked at the rest.

h/w · 01-14-2008, 12:00 PM

Quote:

Originally Posted by rupertwh

That '0' certainly doesn't belong in there. It's 'char *argv[]' or 'char **argv'.
That might already fix your problem. Haven't looked at the rest.

Indeed, missed it among all the debugging trials. It wasn't there earlier, and was the last change (an error) I made.
The problem remains.

h/w · 01-14-2008, 12:39 PM

OK, got it.
It's due to

Code:

while ((opt = getopt(argc, argv, "x::f::p::r::t::")) != -1) {

This page here - http://www.gnu.org/software/libc/man...l#Using-Getopt
mentions how we can use :: for switches that might have a value.

However, my getopt manpage doesn't mention it. Replacing the :: with a single : takes out the segfaults.