1 files changed, 102 insertions, 0 deletions
diff --git a/gnulib-tests/test-fflush2.c b/gnulib-tests/test-fflush2.c
new file mode 100644
index 0000000..ec648d6
--- /dev/null
+++ b/gnulib-tests/test-fflush2.c
@@ -0,0 +1,102 @@
+/* Test of POSIX compatible fflush() function.
+   Copyright (C) 2008-2022 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/>.  */
+
+#include <config.h>
+
+#include <stdio.h>
+
+#include "binary-io.h"
+#include "macros.h"
+
+int
+main (int argc, char **argv)
+{
+  int c;
+
+  /* Avoid the well-known bugs of fflush() on streams in O_TEXT mode
+     on native Windows platforms.  */
+  set_binary_mode (0, O_BINARY);
+
+  if (argc > 1)
+    switch (argv[1][0])
+      {
+      case '1':
+        /* Check fflush after a backup ungetc() call.  This is case 1a in
+           terms of
+           <https://lists.gnu.org/r/bug-gnulib/2008-03/msg00131.html>,
+           according to the Austin Group's resolution on 2009-01-08.  */
+
+        c = fgetc (stdin);
+        ASSERT (c == '#');
+
+        c = fgetc (stdin);
+        ASSERT (c == '!');
+
+        /* Here the file-position indicator must be 2.  */
+
+        c = ungetc ('!', stdin);
+        ASSERT (c == '!');
+
+        fflush (stdin);
+
+        /* Here the file-position indicator must be 1.  */
+
+        c = fgetc (stdin);
+        ASSERT (c == '!');
+
+        c = fgetc (stdin);
+        ASSERT (c == '/');
+
+        return 0;
+
+      case '2':
+        /* Check fflush after a non-backup ungetc() call.  This is case 2a in
+           terms of
+           <https://lists.gnu.org/r/bug-gnulib/2008-03/msg00131.html>,
+           according to the Austin Group's resolution on 2009-01-08.  */
+        /* Check that fflush after a non-backup ungetc() call discards the
+           ungetc buffer.  This is mandated by POSIX
+           <https://pubs.opengroup.org/onlinepubs/9699919799/functions/fflush.html>:
+             "...any characters pushed back onto the stream by ungetc()
+              or ungetwc() that have not subsequently been read from the
+              stream shall be discarded..."  */
+
+        c = fgetc (stdin);
+        ASSERT (c == '#');
+
+        c = fgetc (stdin);
+        ASSERT (c == '!');
+
+        /* Here the file-position indicator must be 2.  */
+
+        c = ungetc ('@', stdin);
+        ASSERT (c == '@');
+
+        fflush (stdin);
+
+        /* Here the file-position indicator must be 1.  */
+
+        c = fgetc (stdin);
+        ASSERT (c == '!');
+
+        c = fgetc (stdin);
+        ASSERT (c == '/');
+
+        return 0;
+      }
+
+  return 1;
+}