--- /dev/null
+/* Test of ftello() function on large files.
+ Copyright (C) 2024 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>, 2024. */
+
+#include <config.h>
+
+/* Specification. */
+#include <stdio.h>
+
+#include <fcntl.h>
+#include <unistd.h>
+
+#include "macros.h"
+
+#define TESTFILE "test-ftello.data"
+#define TESTFILE_ZEROES 3000000000LL
+#define TESTFILE_DATA "GNU"
+#define TESTFILE_DATA_LEN 3
+
+int
+main (void)
+{
+ remove (TESTFILE);
+
+ if (sizeof (off_t) <= 4)
+ {
+ fprintf (stderr, "off_t is only 32 bits.\n");
+ return 77;
+ }
+ /* off_t is larger than 32-bit. */
+
+ /* Create a file that is larger than 2 GiB.
+ On file systems such as ext2, the file will have "holes" and thus
+ not consume much disk space. */
+ {
+ int fd = open (TESTFILE, O_CREAT | O_TRUNC | O_RDWR, 0600);
+ ASSERT (fd >= 0);
+ if (ftruncate (fd, TESTFILE_ZEROES) < 0
+ || lseek (fd, TESTFILE_ZEROES, SEEK_SET) < 0
+ || write (fd, TESTFILE_DATA, TESTFILE_DATA_LEN) < 0
+ || fsync (fd) < 0)
+ {
+ close (fd);
+ remove (TESTFILE);
+ fprintf (stderr, "Could not create 3 GB large file.\n");
+ return 77;
+ }
+ close (fd);
+ }
+
+ /* Check the value of ftello(). */
+ {
+ FILE *fp = fopen (TESTFILE, "r");
+ ASSERT (fp != NULL);
+
+ ASSERT (fseeko (fp, 0, SEEK_END) == 0);
+
+ off_t length = ftello (fp);
+ ASSERT (length > 0);
+ ASSERT (length == TESTFILE_ZEROES + TESTFILE_DATA_LEN);
+
+ int ret = fclose (fp);
+ ASSERT (ret == 0);
+ }
+
+ remove (TESTFILE);
+
+ return test_exit_status;
+}