X-Git-Url: https://git.liburcu.org/?a=blobdiff_plain;f=include%2Furcu%2Fcompiler.h;h=0de713adc1a03f4affc48eda0efd03c1b7c1a470;hb=dd8987a4052e51b87d2a399fec8997c5192f362f;hp=2f32b38d6fb1850291ebd500f0a2fdca53f5c428;hpb=06326a94ac233064654c7100b6384b2833f7b898;p=urcu.git

diff --git a/include/urcu/compiler.h b/include/urcu/compiler.h
index 2f32b38..0de713a 100644
--- a/include/urcu/compiler.h
+++ b/include/urcu/compiler.h
@@ -74,6 +74,23 @@
 		(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))