From 45210ce14136d9410d7139fba816c4465b4c7af5 Mon Sep 17 00:00:00 2001
From: Felix Fietkau <nbd@nbd.name>
Date: Fri, 29 Apr 2022 12:57:25 +0200
Subject: list.h: add container_of_safe macro

It works like container_of, except that it also deals with NULL pointers

Signed-off-by: Felix Fietkau <nbd@nbd.name>
---
 list.h | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/list.h b/list.h
index a2cb241..6aa7b2a 100644
--- a/list.h
+++ b/list.h
@@ -42,6 +42,14 @@
 	})
 #endif
 
+#ifndef container_of_safe
+#define container_of_safe(ptr, type, member)						\
+	({										\
+		const __typeof__(((type *) NULL)->member) *__mptr = (ptr);		\
+		__mptr ? (type *)((char *) __mptr - offsetof(type, member)) : NULL;	\
+	})
+#endif
+
 struct list_head {
 	struct list_head *next;
 	struct list_head *prev;
-- 
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