X-Git-Url: http://git.liburcu.org/?a=blobdiff_plain;f=include%2Furcu%2Fcompiler.h;fp=include%2Furcu%2Fcompiler.h;h=3ba9aeca0c075b10d36e116112b5a359c59b16ff;hb=2a17fe10ad97e997981a98463a4cbda9b4a933a5;hp=fb3c8f160dc580aa8ede55e1ad0fa525e5942ade;hpb=20865c71e59536962252babe23c8ebdbd1cc28b0;p=urcu.git

diff --git a/include/urcu/compiler.h b/include/urcu/compiler.h
index fb3c8f1..3ba9aec 100644
--- a/include/urcu/compiler.h
+++ b/include/urcu/compiler.h
@@ -70,6 +70,23 @@
 		(type *)((char *)__ptr - offsetof(type, member));	\
 	})
 
+/*
+ * caa_container_of_check_null - Get the address of an object containing a field.
+ *
+ * @ptr: pointer to the field.
+ * @type: type of the object.
+ * @member: name of the field within the object.
+ *
+ * Return the address of the object containing the field. Return NULL if
+ * @ptr is NULL.
+ */
+#define caa_container_of_check_null(ptr, type, member)			\
+	__extension__							\
+	({								\
+		const __typeof__(((type *) NULL)->member) * __ptr = (ptr); \
+		(__ptr) ? (type *)((char *)__ptr - offsetof(type, member)) : NULL; \
+	})
+
 #define CAA_BUILD_BUG_ON_ZERO(cond) (sizeof(struct { int:-!!(cond); }))
 #define CAA_BUILD_BUG_ON(cond) ((void)CAA_BUILD_BUG_ON_ZERO(cond))