largefile: Add tests

[Bruno Haible]

This patch adds a unit test for the 'largefile' module. It is meant to
attract the attention of the person who builds a package with Gnulib
tests included. Useful since most packages' configure script doesn't
print a summary file regarding the result of the AC_SYS_LARGEFILE
invocation.


2023-04-16  Bruno Haible  <bruno@clisp.org>

        largefile: Add tests.
        * tests/test-largefile.c: New file.
        * modules/largefile-tests: New file.

============================ tests/test-largefile.c ============================
/* Test of largefile module.
   Copyright (C) 2023 Free Software Foundation, Inc.

   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 3 of the License, 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, see <https://www.gnu.org/licenses/>.  */

/* Written by Bruno Haible <bruno@clisp.org>, 2023.  */

/* This test may fail if AC_SYS_LARGEFILE could not arrange for a 64-bit off_t.
   This should be rare, though: only very old systems don't have support for
   files larger than 2 GiB.  */

#include <config.h>

#include <sys/types.h>
#include <sys/stat.h>

int
main (void)
{
  int result = 0;

  /* Check the size of off_t.
     With MSVC, this test succeeds only thanks to the 'sys_types' module.  */
  if (sizeof (off_t) <= 4)
    result |= 1;

  /* Check the size of the 'struct stat' field 'st_size'.
     With MSVC, this test succeeds only thanks to the 'sys_stat' module.  */
  {
    struct stat st;
    if (sizeof (st.st_size) <= 4)
      result |= 2;
  }

  return result;
}
=========================== modules/largefile-tests ===========================
Files:
tests/test-largefile.c

Depends-on:
sys_types
sys_stat

configure.ac:

Makefile.am:
TESTS += test-largefile
check_PROGRAMS += test-largefile