Dogcows Code - chaz/tar/blob - src/testpad.c

   1 /* Find out if we need the pad field in the header for this machine
   2    Copyright (C) 1991 Free Software Foundation
   3
   4    This program is free software; you can redistribute it and/or
   5    modify it under the terms of the GNU General Public License as
   6    published by the Free Software Foundation; either version 2, or (at
   7    your option) any later version.
   8
   9    This program is distributed in the hope that it will be useful, but
  10    WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12    General Public License for more details.
  13
  14    You should have received a copy of the GNU General Public License
  15    along with this program; if not, write to the Free Software
  16    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  17 */
  18
  19 #include <stdio.h>
  20
  21 struct inc
  22 {
  23   char a[20];
  24   char b[20];
  25 };
  26
  27 struct test1
  28 {
  29   char a;
  30   struct inc in[5];
  31 };
  32
  33 struct test2
  34 {
  35   char a;
  36   char b;
  37   struct inc in[5];
  38 };
  39
  40 void
  41 main ()
  42 {
  43   struct test1 t1;
  44   struct test2 t2;
  45   int t1diff, t2diff;
  46   FILE *fp = fopen ("testpad.h", "w");
  47
  48   if (fp == 0)
  49     {
  50       fprintf (stderr, "testpad: cannot open ");
  51       fflush (stderr);
  52       perror ("testpad.h");
  53       exit (1);
  54     }
  55
  56   t1diff = (char *) &t1.in[0] - (char *) &t1;
  57   t2diff = (char *) &t2.in[0] - (char *) &t2;
  58
  59   if (t2diff == t1diff + 1)
  60     fprintf (fp, "#define NEEDPAD\n");
  61   else if (t1diff != t2diff)
  62     fprintf (stderr, "Cannot determine padding for tar struct, \n\
  63 will try with none.\n");
  64
  65   fclose (fp);
  66   exit (0);
  67 }