From 38a31eb29a48da6c219cbbe49df30e36dba1d5db Mon Sep 17 00:00:00 2001
From: =?utf8?q?=C3=81lvaro=20Fern=C3=A1ndez=20Rojas?= <noltari@gmail.com>
Date: Fri, 14 Nov 2025 08:19:17 +0100
Subject: [PATCH] src: add fallthrough attribute
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- Enable fallthrough warnings.
- Use fallthrough attribute instead of comments.

Signed-off-by: Álvaro Fernández Rojas <noltari@gmail.com>
Link: https://github.com/openwrt/odhcp6c/pull/120
---
 CMakeLists.txt | 1 +
 src/dhcpv6.c   | 6 +++---
 src/odhcp6c.h  | 4 ++++
 3 files changed, 8 insertions(+), 3 deletions(-)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 9067819..ebbe69b 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -26,6 +26,7 @@ target_compile_options(${PROJECT_NAME} PRIVATE -Werror=implicit-function-declara
 target_compile_options(${PROJECT_NAME} PRIVATE -Wformat)
 target_compile_options(${PROJECT_NAME} PRIVATE -Werror=format-security)
 target_compile_options(${PROJECT_NAME} PRIVATE -Werror=format-nonliteral)
+target_compile_options(${PROJECT_NAME} PRIVATE -Wimplicit-fallthrough=5)
 target_compile_options(${PROJECT_NAME} PRIVATE -Wno-unused-parameter)
 target_compile_options(${PROJECT_NAME} PRIVATE -Wmissing-declarations)
 
diff --git a/src/dhcpv6.c b/src/dhcpv6.c
index 7bcaee0..7f73699 100644
--- a/src/dhcpv6.c
+++ b/src/dhcpv6.c
@@ -1144,11 +1144,11 @@ static int dhcpv6_handle_reconfigure(enum dhcpv6_msg orig, const int rc,
 			case DHCPV6_MSG_REBIND:
 				if (t2 != UINT32_MAX)
 					t2 = 0;
-			// Fall through
+				_o_fallthrough;
 			case DHCPV6_MSG_RENEW:
 				if (t1 != UINT32_MAX)
 					t1 = 0;
-			// Fall through
+				_o_fallthrough;
 			case DHCPV6_MSG_INFO_REQ:
 				msg = odata[0];
 				syslog(LOG_NOTICE, "Need to respond with %s in reply to %s",
@@ -2146,7 +2146,7 @@ int dhcpv6_send_request(enum dhcpv6_msg type)
 	default:
 		syslog(LOG_NOTICE, "Send %s message (elapsed %"PRIu64"ms, rc %d)",
 				retx->name, elapsed, retx->rc);
-	// Fall through
+		_o_fallthrough;
 	case DHCPV6_MSG_SOLICIT:
 	case DHCPV6_MSG_INFO_REQ:
 		dhcpv6_send(type, retx->tr_id, elapsed / 10);
diff --git a/src/odhcp6c.h b/src/odhcp6c.h
index 02578cc..42c645d 100644
--- a/src/odhcp6c.h
+++ b/src/odhcp6c.h
@@ -24,6 +24,10 @@
 #define _o_aligned(n) __attribute__((aligned(n)))
 #endif /* _o_aligned */
 
+#ifndef _o_fallthrough
+#define _o_fallthrough __attribute__((__fallthrough__))
+#endif /* _o_fallthrough */
+
 #ifndef _o_packed
 #define _o_packed __attribute__((packed))
 #endif /* _o_packed */
-- 
2.30.2