1  /* Test for difftime
       2     Copyright (C) 2021-2023 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 reproducible 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>