time/tst-difftime.c

   1 /* Test for difftime
   2    Copyright (C) 2021 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, see
  17    <https://www.gnu.org/licenses/>.  */
  18
  19 #include <time.h>
  20 #include <support/check.h>
  21
  22 static void
  23 test_difftime_helper (time_t t1, time_t t0, double exp_val)
  24 {
  25   double sub = difftime (t1, t0);
  26   if (sub != exp_val)
  27     FAIL_EXIT1 ("*** Difftime returned %f (expected %f)\n", sub, exp_val);
  28 }
  29
  30 static int
  31 do_test (void)
  32 {
  33   time_t t = 1383791700; /* Provide reproductible start value.  */
  34
  35   /* Check if difftime works with current time.  */
  36   test_difftime_helper (t + 1800, t - 1800, 3600.0);
  37   test_difftime_helper (t - 1800, t + 1800, -3600.0);
  38
  39   t = 0x7FFFFFFF;
  40   /* Check if we run on port with 32 bit time_t size */
  41   time_t tov;
  42   if (__builtin_add_overflow (t, 1, &tov))
  43     return 0;
  44
  45   /* Check if the time is converted after 32 bit time_t overflow.  */
  46   test_difftime_helper (t + 1800, t - 1800, 3600.0);
  47   test_difftime_helper (t - 1800, t + 1800, -3600.0);
  48
  49   t = tov;
  50   test_difftime_helper (t + 1800, t - 1800, 3600.0);
  51   test_difftime_helper (t - 1800, t + 1800, -3600.0);
  52
  53   return 0;
  54 }
  55
  56 #include <support/test-driver.c>