tar/src/testpad.c

/* Find out if we need the pad field in the header for this machine
   Copyright (C) 1991 Free Software Foundation

   This program is free software; you can redistribute it and/or
   modify it under the terms of the GNU General Public License as
   published by the Free Software Foundation; either version 2, or (at
   your option) any later version.

   This program is distributed in the hope that it will be useful, but
   WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program; if not, write to the Free Software
   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/

#include <stdio.h>

struct inc
{
  char a[20];
  char b[20];
};

struct test1
{
  char a;
  struct inc in[5];
};

struct test2
{
  char a;
  char b;
  struct inc in[5];
};

void
main ()
{
  struct test1 t1;
  struct test2 t2;
  int t1diff, t2diff;
  FILE *fp = fopen ("testpad.h", "w");

  if (fp == 0)
    {
      fprintf (stderr, "testpad: cannot open ");
      fflush (stderr);
      perror ("testpad.h");
      exit (1);
    }

  t1diff = (char *) &t1.in[0] - (char *) &t1;
  t2diff = (char *) &t2.in[0] - (char *) &t2;

  if (t2diff == t1diff + 1)
    fprintf (fp, "#define NEEDPAD\n");
  else if (t1diff != t2diff)
    fprintf (stderr, "Cannot determine padding for tar struct, \n\
will try with none.\n");

  fclose (fp);
  exit (0);
}