1 files changed, 83 insertions, 0 deletions

diff --git a/src/regress/lib/libc/stdio/test___fwriting.c b/src/regress/lib/libc/stdio/test___fwriting.c
new file mode 100644
index 0000000000..eb4671d3cf
--- /dev/null
+++ b/src/regress/lib/libc/stdio/test___fwriting.c
@@ -0,0 +1,83 @@
+/*      $OpenBSD: test___fwriting.c,v 1.1 2025/05/25 00:20:54 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 <stdio.h>
+#include <stdio_ext.h>
+#include <stdlib.h>
+
+/* we use assert() */
+#undef  NDEBUG
+
+#define TMPFILENAME     "test___fwriting.tmp"
+
+void test___fwriting0(void);
+void test___fwriting1(void);
+
+void
+test___fwriting0(void)
+{
+        FILE    *fp;
+        int      r;
+
+        fp = fopen(TMPFILENAME, "w");   /* write only */
+        assert(fp != NULL);
+        assert(__fwriting(fp) != 0);    /* writing is true immediately */
+        r = fputs("Hello world\n", fp);
+        assert(r >= 0);
+        r = fclose(fp);
+        assert(r == 0);
+
+        fp = fopen(TMPFILENAME, "a");   /* append only */
+        assert(fp != NULL);
+        assert(__fwriting(fp) != 0);    /* writing immediately */
+        r = fclose(fp);
+        assert(r == 0);
+}
+
+void
+test___fwriting1(void)
+{
+        FILE    *fp;
+        int      r;
+
+        fp = fopen(TMPFILENAME, "w+");  /* read / write */
+        assert(fp != NULL);
+        r = fputs("Hello world\n", fp);
+        assert(r >= 0);
+        assert(__fwriting(fp) != 0);
+        rewind(fp);
+        assert(fgetc(fp) == 'H');       /* read */
+        assert(__fwriting(fp) == 0);    /* writing becomes false */
+        fputc('e', fp);
+        assert(__fwriting(fp) != 0);    /* writing becomes true */
+        ungetc('e', fp);
+        assert(__fwriting(fp) == 0);    /* ungetc -> writing becomes false */
+
+        r = fclose(fp);
+        assert(r == 0);
+}
+
+int
+main(int argc, char *argv[])
+{
+        test___fwriting0();
+        test___fwriting1();
+
+        exit(0);
+}