@@ -98,6 +98,7 @@ tests = \
tst-fclose-unopened \
tst-fclose-unopened2 \
tst-fdopen-seek-failure \
+ tst-fflush \
tst-fgetc-after-eof \
tst-fgetwc \
tst-fgetws \
new file mode 100644
@@ -0,0 +1,171 @@
+/* Test that fflush (FILE) and fflush (NULL) are semantically equivalent.
+
+ Copyright (C) 2024 Free Software Foundation, Inc.
+ This file is part of the GNU C Library.
+
+ The GNU C Library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 2.1 of the License, or (at your option) any later version.
+
+ The GNU C Library 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
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public
+ License along with the GNU C Library; if not, see
+ <https://www.gnu.org/licenses/>. */
+
+/* A success on this test doesn't imply the effectiveness of fflush as
+ we can't ensure that the file wasn't already in the expected state
+ before the call of the function. It only ensures that, if the test
+ fails, fflush is broken. */
+
+#include <fcntl.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+#include <sys/stat.h>
+#include <sys/mman.h>
+
+#include <support/check.h>
+#include <support/support.h>
+#include <support/temp_file.h>
+#include <support/test-driver.h>
+#include <support/xstdio.h>
+#include <support/xunistd.h>
+
+#define CONTENT_SZ_MAX 32
+#define TEST_FILE_COUNT 10
+
+#define FILE_FLUSH 0
+#define GLOBAL_FLUSH 1
+
+#define FILE_UNCHANGED 0
+#define FILE_CHANGED 1
+
+struct
+{
+ FILE *file;
+ char *name;
+ int fd;
+ char *mfile;
+} files[TEST_FILE_COUNT];
+
+static void
+base_init (int file)
+{
+ files[file].file = NULL;
+ files[file].fd = -1;
+ files[file].name = NULL;
+ files[file].mfile = NULL;
+}
+
+static void
+file_init (int file)
+{
+ int fd = -1;
+
+ base_init (file);
+
+ if (file >= TEST_FILE_COUNT)
+ return;
+
+ xclose (create_temp_file ("tst-fflush", &files[file].name));
+
+ fd = xopen (files[file].name, O_RDONLY, 0);
+ files[file].mfile = (char *) xmmap (NULL, CONTENT_SZ_MAX, PROT_READ,
+ MAP_SHARED, fd);
+ xclose (fd);
+
+ files[file].file = xfopen (files[file].name, "w");
+ TEST_VERIFY_EXIT (files[file].file != NULL);
+ files[file].fd = fileno (files[file].file);
+}
+
+static void
+file_cleanup (int file)
+{
+ xfclose (files[file].file);
+ free (files[file].name);
+ xmunmap (files[file].mfile, CONTENT_SZ_MAX);
+
+ base_init (file);
+}
+
+static int
+file_changed (int to_check, int global_flush)
+{
+ struct stat stats = { };
+ bool content_matches = 0;
+ char expected[CONTENT_SZ_MAX] = { };
+
+ verbose_printf ("Check that %s (%d) exactly contains the data we put in\n",
+ files[to_check].name, to_check);
+
+ /* File should contain "N:M" where both N and M are one digit exactly. */
+ snprintf (expected, sizeof (expected), "%d:%d", global_flush, to_check);
+ content_matches
+ = (strncmp (files[to_check].mfile, expected, sizeof (expected)) == 0);
+
+ TEST_VERIFY_EXIT (content_matches != 0);
+
+ TEST_VERIFY_EXIT (fstat (files[to_check].fd, &stats) >= 0);
+ TEST_VERIFY_EXIT (stats.st_size == 3);
+
+ /* Not reached if the data doesn't match. */
+ return FILE_CHANGED;
+}
+
+static void
+file_flush (int global_flush)
+{
+ for (int i = 0; i < TEST_FILE_COUNT; i++)
+ file_init (i);
+
+ /* Print a unique identifier in each file, that is not too long nor contain
+ new line to not trigger _IO_OVERFLOW/_IO_SYNC. */
+ for (int i = 0; i < TEST_FILE_COUNT; i++)
+ fprintf (files[i].file, "%d:%d", global_flush, i);
+
+ if (global_flush)
+ {
+ fflush (NULL);
+ }
+ else
+ {
+ for (int i = 0; i < TEST_FILE_COUNT; i++)
+ fflush (files[i].file);
+ }
+
+ for (int i = 0; i < TEST_FILE_COUNT; i++)
+ {
+ int changed = file_changed (i, global_flush);
+
+ verbose_printf ("Check that file %s has been modified after fflush\n",
+ files[i].name);
+ verbose_printf ("File %s; changed %d; global fflush %d\n",
+ files[i].name, changed, !!global_flush);
+ TEST_VERIFY_EXIT (changed != FILE_UNCHANGED);
+ }
+
+ for (int i = 0; i < TEST_FILE_COUNT; i++)
+ file_cleanup (i);
+}
+
+static int
+do_test (void)
+{
+ verbose_printf ("Checking fflush(FILE)\n");
+ file_flush (FILE_FLUSH);
+
+ verbose_printf ("checking fflush(NULL)\n");
+ file_flush (GLOBAL_FLUSH);
+
+ return 0;
+}
+
+#include <support/test-driver.c>