Add files via upload

src/fallthrough.h

@@ -0,0 +1,21 @@
+/*
+ * Copyright (c) 2022 Yubico AB. All rights reserved.
+ * Use of this source code is governed by a BSD-style
+ * license that can be found in the LICENSE file.
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#ifndef _FALLTHROUGH_H
+#define _FALLTHROUGH_H
+
+#if defined(__GNUC__)
+#if __has_attribute(fallthrough)
+#define FALLTHROUGH	__attribute__((fallthrough));
+#endif
+#endif /* __GNUC__ */
+
+#ifndef FALLTHROUGH
+#define FALLTHROUGH	/* FALLTHROUGH */
+#endif
+
+#endif /* !_FALLTHROUGH_H */