1 files changed, 71 insertions, 0 deletions

diff --git a/src/regress/lib/libc/stdio/test___freadahead.c b/src/regress/lib/libc/stdio/test___freadahead.c
new file mode 100644
index 0000000000..66d5e3492a
--- /dev/null
+++ b/src/regress/lib/libc/stdio/test___freadahead.c
@@ -0,0 +1,71 @@
+/*      $OpenBSD: test___freadahead.c,v 1.2 2025/06/03 14:35:27 yasuoka Exp $   */
+
+/*
+ * Copyright (c) 2025 YASUOKA Masahiko <yasuoka@yasuoka.net>
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+#include <assert.h>
+#include <errno.h>
+#include <stdio.h>
+#include <stdio_ext.h>
+#include <stdlib.h>
+
+/* we use assert() */
+#undef  NDEBUG
+
+#define TMPFILENAME     "test___freadahead.tmp"
+
+void test___freadahead0(void);
+
+void
+test___freadahead0(void)
+{
+        FILE    *fp;
+        int      r;
+        size_t   s;
+
+        fp = fopen(TMPFILENAME, "w");
+        assert(fp != NULL);
+        r = fputs("Hello world", fp);
+        assert(r >= 0);
+        r = fclose(fp);
+
+        fp = fopen(TMPFILENAME, "r");
+        s = __freadahead(fp);
+        assert(s == 0);
+        assert(fgetc(fp) == 'H');
+        s = __freadahead(fp);
+        assert(s == 10);
+        r = fflush(fp);
+#if 0
+        /* fflush() to reading file is not supported (yet) */
+        assert(errno == EBADF);
+#else
+        assert(r == 0);
+        s = __freadahead(fp);
+        assert(s == 0);
+#endif
+
+        r = fclose(fp);
+        assert(r == 0);
+}
+
+int
+main(int argc, char *argv[])
+{
+        test___freadahead0();
+
+        exit(0);
+}